United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA > '. 204
978
Research and Development
&EPA
Performance
Tests of Four
Selected Oil
Spill Skimmers
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-204
September 1978
PERFORMANCE TESTS OF FOUR SELECTED OIL SPILL SKIMMERS
by
Robert W. Urban
Douglas J. Graham
Pollution Abatement Associates
Corte Madera, California 94925
and
Sol H. Schwartz
Mason & Hanger-Silas Mason Co., Inc.
Leonardo, New Jersey 07737
Contract No. 68-03-0490
Project Officer
John S. Farlow
Oil and Hazardous Materials Spills Branch
Industrial Environmental Research Laboratory
Edison, New Jersey 08817
U.S. Coast Guard
U.S. Department of Energy
U.S. Environmental Protection Agency
U.S. Navy
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental
Research Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views or policies of the OHMSETT Interagency Test Committee
or its member organizations, the U.S. Environmental Protection Agency,
the U.S. Coast Guard, the U.S. Department of Energy, and the U.S. Navy,
nor does mention of trade names or commercial products constitute endorsement
or recommendation for use, nor does failure to mention or test other
commercial products indicate that other commercial products are not
available or cannot perform similarly well as those mentioned.
ii
-------
FOREWORD
When energy and material resources are extracted, processed, con-
verted, and used, the related pollutional impacts on our environment and
even on our health often require that new and increasingly more efficient
pollution control methods be used. The Industrial Environmental Research
Laboratory - Cincinnati (lERL-Ci) assists in developing and demonstrating
new and improved methodologies that will meet these needs both efficiently
and economically.
This report describes performance evaluation tests of four oil
skimmers. This report will be of interest to all those interested in
cleaning up oil spills in inland and coastal waters. Further information
may be obtained through the Resource Extraction and Handling Division,
Oil and Hazardous Materials Spills Branch, Edison, New Jersey.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
iii
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PREFACE
In February, 1977, representatives of the United States Environmental
Protection Agency, Coast Guard, Navy, and Department of Energy met to
form an OHMSETT Interagency Test Committee (OITC) for the purpose of
sponsoring tests of selected oil pollution control equipment at the Oil
and Hazardous Materials Simulated Environmental Test Tank (OHMSETT)
facility in Leonardo, New Jersey. The primary motivations in forming
the OITC were:
(a) To combine funds to study equipment of joint interest.
(b) To provide a formal focal point for interagency discussion and
comparison of oil pollution abatement programs.
Other interested U.S. and Canadian agencies have been invited to parti-
cipate in committee discussions, offer recommendations for selection of
test equipment, and share in test data results.
This report describes the performance testing of four selected
commercial off-the-shelf oil spill pickup devices. In addition to the
complete technical details contained in this written report, a 16 mm
narrated motion picture report has also been prepared which shows the
dynamic nature of selected test runs and a summary of test results.
As public agencies, the sponsors of this work hope that the test
results generated under this program can be utilized not only within
their own agencies but also by the public.
iv
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ABSTRACT
A series of performance tests were conducted at the U.S. Environmental
Protection Agency's OHMSETT test facility with four selected oil spill
pickup devices (skimmers). A description of the OHMSETT facility is
presented in Appendix A. Each of the four skimmers was tested for two
weeks with both high and low viscosity oils. Selection of the four test
skijnmers depended on the satisfaction of the following criteria:
(a) Commercial hardware must have either never before tested at
OHMSETT, or have a significant improvement over similar pre-
viously tested equipment.
(b) Equipment must be of significant interest to at least one of
the Test Committee sponsoring agencies.
(c) Manufacturer must be willing to lend the equipment for testing
at no charge to the government.
The objectives of the tests were not to compare skimmers with one
another, but to establish the range of best performance for each skimmer
under the manufacturer's design limits and to document test results on
16 mm film and by quantitative measures of performance.
The four oil skimmers studied by the Test Committee during the
OHMSETT 1977 season were, in order of testing:
(1) Oil Mop ZRV Skimmer. A catamaran vessel designed primarily
for oil skimming at speeds above 1.5 m/s.
(2) Cyclonet 050. A device mounted on an inflatable boat designed
for oil skimming in relatively calm water.
(3) Clowsor Skimmer. A unit designed primarily for recovering oil
at very high rates while held stationary in calm water.
(4) Bennett Mark 6E. A semi-catamaran vessel designed for skimming
oil at speeds up to 1.5 m/s.
A total of 198 individual data test runs were made during the
course of the 8-week test program. Each skimmer was tested to the limit
of its design conditions and beyond, in order to confirm the limit of
effective oil slick pickup. Considerable quantitative data were obtained
for each skimmer and are discussed in separate sections of this report.
In reviewing the test results for each skimmer, it should be kept in
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mind that trends, or rates of change, of test results are often more
Important than the numerical value of individual data points. These
trends show to what extent changing environmental conditions may affect
performance.
A motion picture report entitled "Performance Testing of Four
Selected Oil Skimmers" is an important adjunct to this report and
illustrates the dynamic response of each skimmer to selected test tank
conditions.
This report was submitted in fulfillment of Contract No. 68-03-
0490, Job Order No. 32, by Mason & Hanger-Silas Mason Co., Inc. under
the sponsorship of the U.S. Environmental Protection Agency, U.S. Coast
Guard, U.S. Department of Energy, and U.S. Navy. Technical direction
was subcontracted to Pollution Abatement Associates. This report covers
a period from April 18, 1977 to October 28, 1977, and work was completed
as of December 15, 1977.
Vi
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CONTENTS
Foreword ill
Preface iv
Abstract v
Figures viii
Tables ix
Abbreviations x
Conversion Factors xi
Acknowledgments xii-
1. Project Objectives 1
2. Oil Mop ZRV Skimmer
Conclusions and recommendations 3
Skimmer description 5
Test matrix and procedures 7
Test results and discussion 8
3. Cyclonet 050 Skimmer
Conclusions and recommendations 15
Skimmer description 16
Test matrix and procedures 18
Test results and discussion 20
4. Clowsor Skimmer
Conclusions and recommendations 31
Skimmer description 32
Test matrix and procedures 34
Test results and discussion 37
5. Bennett Mark 6E
Conclusions and recommendations A3
Skimmer description 45
Test matrix and procedures 46
Test results and discussion 49
Appendices
A. Facility description 58
6. Sampling procedures 61
C. Range of test oil properties for the 1977 OITC series .... 64
D. Skimmer brochures 66
vii
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FIGURES
Number Page
1 Oil Mop ZRV under test 6
2 Oil Mop ZRV schematic 6
3 Oil Mop bow wringers 7
4 TE Trends - Oil Mop ZRV 9
5 RE Trends - Oil Mop ZRV 9
6 Oil Mop ZRV jamming conditions 11
7 Cyclonet 050 under test 17
8 Cyclonet 050 schematic 18
9 TE Trends (Heavy Oil) - Cyclonet 050 22
10 TE Trends (Light Oil) - Cyclonet 050 22
11 TE Trends - single vs. double Cyclonet 050 23
12 Bow underview - Cyclonet 050 and Zodiac 23
13 Underwater view - Cyclonet 050 (No Waves, 0.75 m/s Tow) .... 24
14 Modifications to Cyclonet 050 28
15 Maximum performance limits - Cyclonet 050 Hydrocyclone 29
16 Clowsor under stationary test 33
17 Clowsor schematic . . 34
18 Underwater view - Clowsor (No Waves, 0.25 m/s Tow) 38
19 RE Trends (stationary tests) - Clowsor 39
20 RE Trends (stationary tests - heavy oil) - Clowsor 40
21 RE Trends (Towed) - Clowsor 40
22 Bennett under test .......... .... 45
23 Bennet Mark 6E schematic 46
24 TE Trends (heavy oil) - Bennett Mark 6E 50
25 TE Trends (light oil) - Bennett Mark 6E 51
26 RE Trends - Bennett Mark 6E 52
27 Scraper blade detail - Bennett Squeeze Belt 57
viii
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TABLES
Number
1 Highest Average Results - Oil Mop ZRV (Heavy Oil) 3
2 Highest Average Results - Oil Mop ZRV (Light Oil) . . 3
3 Test Matrix - Oil Mop ZRV '.'.'. 7
4 Test Procedures - Oil Mop ZRV 1 !!!!!!*'" 8
5 Test Results - Oil Mop ZRV (Heavy Oil) ...!!!!!!!!! 13
6 Test Results - Oil Mop ZRV (Light Oil) 1 !!!!!! 14
7 Highest Average Results - Cyclonet 050 (Heavy Oil) ...'.'!! 15
8 Highest Average Results - Cyclonet 050 (Light Oil) ...!!! 15
9 Test Matrix - Cyclonet 050 19
10 Test Procedures - Cyclonet 050 !!!!!! 20
11 Test Results - Cyclonet 050 (Heavy Oil) ....!!!!!!!! 25
12 Test Results - Cyclonet 050 (Light Oil) '.'.'. 26
13 Highest Average Results - Clowsor (Heavy Oil) '. '. '. '. 31
14 Highest Average Results - Clowsor (Light Oil) 31
15 Test Mateix - Clowsor 35
16 Test Procedures - Clowsor (Encircling Boom) '.'.'. 36
17 Test Procedures - Clowsor (Stationary) '. 35
18 Test Procedures - Clowsor (Towed) [ 37
19 Test Results - Clowsor (Heavy Oil) i 41
20 Test Results - Clowsor (Light Oil) 42
21 Highest Average Results - Bennett Mark 6E (Heavy Oil) 43
22 Highest Average Results - Bennett Mark 6E (Light Oil) 43
23 Test Matrix - Bennett Mark 6E 47
24 Test Procedures - Bennett Mark 6E '.'.'. 48
25 Test Results - Bennett Mark 6E (Heavy Oil) ....!!!!!.' 53
26 Test Results - Bennett Mark 6E (Light Oil) ! ! .' ! 55
ix
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ABBREVIATIONS
m —metres
mm —millimetres
m —cubic metres
m/s —metres per second
m2/s -square metres per second
m3/s —cubic metres per second
s —seconds
VQ±l —oil collected by skimmer during steady state test time (m3)
tss —steady state test time (s)
VT —total oil/water mixture collected by skimmer during steady
state test time (m3)
Qn —rate at which test oil enters the front of the skimmer
(m3/s)
ND —No Data
HC —Harbor Chop wave condition. A non-regular wave condition
achieved by allowing waves to reflect off all tank side walls
OHMSETT —Oil and Hazardous Materials Simulated Environmental Test Tank
OITC —OHMSETT Interagency Test Committee
ORR -
.1
—Oil Recovery Rate » volume of oil recovered by the skimmer
per unit time during steady state test (m3/s)
x 100 —Recovery Efficiency • percent oil in the oil/water mixture
being recovered from the water surface by the skimmer (%)
—Throughput Efficiency » percent of oil entering the
skimmer which is recovered from the water surface by
the skimmer (%)
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METRIC TO ENGLISH
CONVERSION FACTORS
To convert from
Celsius
joule
joule
kilogram
metre
metre
metre2
metre2
metre3
metre3
metre/second
metre/second
metre2/second
metre3/second
metre3/second
newton
watt
ENGLISH TO METRIC
centistoke
degree Fahrenheit
erg
foot
foot2
foot/minute
foot3/minute
foot-pound-force
gallon (U.S. liquid)
gallon (U.S. liquid)/
minute
horsepower (550 ft
Ibf/s)
inch
inch2
knot (international)
litre
pound-force (Ibf avoir)
pound-mass (Ibm avoir)
to
degree Fahrenheit
erg
f oo t-pound-force
pound-mass (Ibm avoir)
foot
inch
foot2
inch2
gallon (U.S. liquid)
litre
foot/minute
knot
centistoke
foot3/minute
gallon (U.S. liquid)/minute
pound-force (Ibf avoir)
horsepower (550 ft Ibf/s)
metre2/second
Celsius
joule
metre
metre2
metre/second
metre3/second
joule
metre3
metre3/second
watt
metre
metre2
metre/second
metre3
newton
kilogram
Multiply by
tc - (tF-32)/1.8
1.000 E+07
7.374 E-01
2.205 E+00
3.281 E+00
3.937 E+01
1.076 E+01
1.549 E+03
2.642 E+02
1.000 E+03
1.969 E+02
1.944 E+00
1.000 E+06
2.119 E+03
1.587 E+04
2.248 E-01
1.341 E-03
1.000 E-06
t - (tF-32)/1.8
1.000 E-07
3.048 E-01
9.290 E-02
5.080 E-03
4.719 E-04
1.356 E+00
3.785 E-03
6.309 E-05
7.457
2.540
6.452
,144
,000
.448
5.
1.
4.
4.535
E+02
E-02
E-04
E-01
E-03
E+00
E-01
xi
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ACKNOWLEDGMENTS
Acknowledgments are first and foremost due the individual manu-
facturers who willingly supplied their skimmers and operator personnel,
as necessary for the duration of these tests.
Mr. John S. Farlow, the OHMSETT Project Officer for the Environ-
mental Protection Agency, served as the OHMSETT Interagency Test Committee
(OITC) Chairman and provided valuable assistance throughout the project.
Mason & Hanger-Silas Mason Co., Inc., the operating contractor for
OHMSETT, deserves a special note of thanks for the professional and
innovative support of their personnel at the OHMSETT test site. Mr.
R.A. Ackerman, General Manager, Mr. M.G. Johnson, Test Director, and the
Test Engineers, H.W. Lichte and M.K. Breslin, provided continual guidance
and assistance throughout the test program concerning detailed test
procedures and sequence to maximize the number of data runs obtained.
In the areas of data collection and reduction, Mr. G.F. Smith was
especially helpful in the laboratory measurement of numerous oil/water
samples and the reduction of this raw data into graphic form.
Videotape coverage, a key element in making real time decisions
between test runs, 16 mm photography for the motion picture, and 35 mm
photography for the written report were amply carried out in spite of
the usual difficulties of weather and electronic malfunctions by the
OHMSETT photo/video electronics department.
Funds for this project were provided by the OHMSETT Interagency
Test Committee (OITC) comprised of the U.S. Environmental Protection
Agency, the U.S. Department of Energy, the U.S. Coast Guard, and the
U.S. Navy.
xii
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SECTION 1
PROJECT OBJECTIVES
The objectives of the 1977 OITC-sponsored OHMSETT tests were three-
fold:
(1) Collect quantitative performance data of skimmer operation
over a wide range of wave conditions, tow speeds, and oil
types.
(2) Determine a range of best performance for each oil skimmer.
(3) Identify equipment modifications which may increase skimmer
performance.
These objectives were accomplished for each of the four selected skimmers
by conducting the test series described in the individual skimmer sections
of this report.
Three techniques were important to ensure good test data. First,
for each skimmer, initial test runs involving many oil/water samples
were conducted to ensure that performance data was being taken only
after steady state conditions had developed after start up of the test
run. Second, while conducting these tests repeatability of the measured
data was of primary concern. In some cases, a number of reruns were
conducted to confirm repeatability. Third, every effort was made to
ensure that all of the test oil slick entered the mouth of the skimmer
to reduce the uncertainty in determining the oil volume actually en-
countered during the test run.
The following three performance parameters were determined for each
individual test run (see also Abbreviations):
(!) THROUGHPUT EFFICIENCY (TE). Percentage of oil entering the
skimmer which is picked up.
(2) RECOVERY EFFICIENCY (RE). Percent oil in the oil/water
mixture picked up by the skimmer.
(3) OIL RECOVERY RATE (ORR). Volume of oil recovered by the
skimmer per unit time during steady state operation.
During the course of data analysis it also became clear that the
trend of the above three parameters with variations of tow speed, wave
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condition, and oil type is at least as important as the numerical values
in determining the range of applicability of a given skimmer.
Each of the following four sections is a complete and self-contained
description of test procedures, conditions, results, and trends of
results with changes in conditions for each of the four skimmers tested.
It should be kept in mind that each skimmer is designed to operate most
effectively in a different range of environmental conditions; therefore,
direct comparison of one skimmer with another is not always possible.
Four Appendices are attached to this report and present, in turn, a
description of the OHMSETT facility, properties of the test oils used
for each skimmer test, descriptive brochures for each skimmer, and
sampling procedures.
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SECTION 2
OIL MOP ZRV SKIMMER
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
During the period 18 to 29 April 1977, 44 oil pickup performance
data runs were conducted with the Oil Mop ZRV skimmer. A total of 17
tests were conducted with high viscosity (heavy) oil and 27 tests using
low viscosity (light) oil1.
Best performance—
The highest average values of the three skimmer performance parameters,
TE, RE, and ORR, for each of the heavy and light oil tests are summarized
in Tables 1 and 2.
TABLE 1. HIGHEST AVERAGE RESULTS - OIL MOP ZRV (HEAVY OIL)
Performance Highest average Tow speed Wave condition
parameter result m/s ht x length (m x m)
TE 71% 0.5 0
RE 77% 1.0 0
ORR 3.6 (x 10-V/s) 1.5 0
TABLE 2. HIGHEST AVERAGE RESULTS - OIL MOP ZRV (LIGHT OIL)
Performance Highest average Tow speed Wave condition
parameter result m/s ht x length (m x m)
TE 78% 1.0 0
RE 70% 1.0 0
ORR 4.8 (x 10~3m3/s) 2.0 0
Physical properties of both test oils are listed in Appendix C for each
skimmer test.
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The above values are the highest averages of all individual test results
at the same test tank conditions. Although certain test results may be
higher than the values listed above, the use of an average is more
representative of the true value since it compensates for random experi-
mental errors.
For an overall conclusion of the trends of the above three skimmer
performance parameters, the average values of results are plotted for
each test tank condition tested.
Operating Limits—
Based upon the behavior observed in these tests, the operating
limits for this skimmer appear to depend upon three factors:
(1) Mechanical design of the bow mop wringer and stern roller
assemblies.
(2) Contact time between oil slick and mops as the skimmer travels
over the slick.
(3) Large surface area of the drip pan between stern rollers and
bow wringer.
Regarding the first item, the bow wringer assembly was unable to
rotate the mops with heavy oil at speeds faster than 1.5 m/s without
jamming, due to mop strands adhering to the squeeze rollers. Followine
the conclusion of this test series, the manufacturer resolved this
problem through a redesign of the bow wringer assembly. Oil loss
occurred in light oil tests in the form of a rooster tail as the mops
were pulled aboard the skimmer over the stern roller at forward soeeda
above 1.5 m/s. K
Regarding the second factor, the oil contact time limits the pickup
rate of oil at high skimmer forward speeds. The number of test runs was
insufficient to establish this upper speed limit precisely. The maximum
speed for which data was obtained was 2.5 m/s. At skimmer forward
speeds of 2.5 m/s, the oil-to-mop contact time is only 4.8 seconds
between the bow and stern of the 11.7 m long catamaran where the mops
are lifted out of the water.
Oil loss from the third factor was noted during tests with heavy
oil. The loss was caused by slippage of the mops over the squeeze
rollers at the bow due to the large drag of the oil-laden mops against
the drip pan as they were pulled forward by the bow wringer assembly.
Mechanical Problems—
Mechanical difficulties were encountered with the mop wringer
assembly on the bow, the drain pan between bow and stern, and the stern
rollers. The bow mop wringer jammed frequently when operating with
heavy oil and a 25 cm diameter mop. The jamming with the mop and heavy
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oil was due to individual strands of the mop which would stick to the
roller after being squeezed, thus dragging the mop around the roller
causing a jam. A number of field modifications were attempted (see
Discussion paragraph), but without success. The problem was reduced
somewhat with the substitution of a thinner 15 cm diameter mop for the
25 cm diameter one. All heavy oil tests were run with the thinner 15 cm
diameter mop. However, the tendency to jam was still present above a
1.5 m/s tow speed. Also, in heavy oil tests, the cumulative drag of the
six oil-laden 15 cm mops against the return pan caused slippage of the
mops against the squeezing rollers above 1.5 m/s tow speeds. It was
necessary to instail a set of nonpowered rollers stretching across the
return pan to lift the saturated mops off the pan before the bow wringer
assembly could pull the mops forward without slippage. A splash cover
on the stern roller assembly was added to prevent loss of light oil via
the rooster tail phenomena at speeds above 1.5 m/s. The presence of
deck level engine hatches caused take up of water in the engine com-
partments during some wave tests.
Recommendations
None of the mechanical problems mentioned in the Conclusions section
above are serious. All have been passed on to the equipment manufacturer
and have been considered in the design of subsequent Oil Mop units. It
is recommended that the Oil Mop ZRV skimmer, complete with modifications
to eliminate the mechanical problems discussed above, be retested at
OHMSETT.
SKIMMER DESCRIPTION
The Oil Mop ZRV skimmer as manufactured by Oil Mop, Incorporated,
of Belle Chasse, Louisiana, is a self-propelled catamaran vessel, 11.6 m
in length with a 3.7 m beam, designed to be operated by a crew of two.
Other technical specifications are presented in the brochure in Appendix
D. As an oil slick enters the space between the catamaran hulls from
the right, it is contacted by one of six floating polypropylene brush-
like ropes called mops. The mops are rotated at a speed equal to the
forward way of the skimmer so that a zero relative velocity condition is
achieved. The oil in the slick is sorbed onto the surface of the many
flexible strands of the mop as the skimmer moves over the oil slick.
After the skimmer has passed a fixed point in the oil slick, the mops
are lifted out of the water, up over a stern roller assembly, and
pulled along a flat return tray running the length of the vessel by a
powered squeeze wringer assembly at the bow. Here the oil is squeezed
out of the mops and drops by gravity into a tray below, where it is
pumped off the skimmer by two positive displacement Tuthill lobe pumps.
The total pumping capacity of these two pumps is 17.7 x 10~3m3/s, although
in these tests with 3 mm thick oil slicks, the maximum average offloading
rate observed was 4.98 x 10~3m3/s with light oil. Two diesel prime
movers, one in the stern of each catamaran hull, drive the outboard
propulsion (not used for these tests) and the various hydrualic motors
which operate the bow wringer assembly and the Tuthill offloading pumps.
The two hydraulically actuated wringer assemblies are mounted on the
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bow. Each provides rotational and squeezing power for a gang of three
mops. Figures 1, 2, and 3 show the device under test at OHMSETT as well
as its operating principle and above-mentioned wringer assemblies.
Figure 1. Oil Mop Inc. ZRV under test.
Splash Shield
Bow Wringer
Skimmer Travel . £> Clean Mop
Return Tray Rollers
Figure 2. Oil Mop Inc. ZRV schematic.
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Figure 3. Oil Mop Inc. ZRV bow wringers.
TEST MATRIX AND PROCEDURES
Test Matrix
Initial checkout tests were conducted to establish the maximum
operating wave and tow speed conditions under which oil collection tests
were to be conducted and to evaluate various sampling procedures. The
performance tests for both heavy and light oils were then conducted in
accordance with the matrix of test conditions itemized in Table 3.
TABLE 3. TEST MATRIX - OIL MOP ZRV
Test
mode
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Towed
Tow speed
(m/s)
0.5
1.0
1.5
1.5
0.5
1.0
2.0
2.5
1.0
2.0
2.5
1.0
2.0
Slick
thk. (mm)
3
.
1
1
!
;
I
•
>
1
;
Waves
(m x m)
0
0
0.6 HC
0
'
0
0.6 HC
0.6 HC
0.6 HC
0.8 x 12.4
0.8 x 12.4
Test
oil
Heavy
Heavy
Heavy
Heavy
Heavy
Light
Light
Light
Light
Light
Light
Light
Light
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Procedures
For initial checkout runs without oil, the procedure was to set the
wave condition and tow the skimmer at a gradually increasing speed from
1 to 3 m/s. Skimmer response was noted in tape recorded comments by the
test engineers and photographed with 35 mm and above water video cameras.
These taped comments and replay of the videotape formed the basis for
establishing the maximum tow speed and wave conditions to be used for
subsequent oil performance tests.
All oil performance tests under the test conditions of Table 3 were
conducted using the procedure itemized in Table 4. Appendix B gives
sampling procedures, and Appendix C lists test oil properties.
TABLE 4. TEST PROCEDURES - OIL MOP ZRV
1. Pump dry the mop wringer sumps and skimmer-to-collection barrel
with the onboard positive displacement pumps.
2. Accelerate skimmer up to test speed; at a predetermined mark
along the tank, start test oil distribution.
3. When test oil slick reaches the skimmer bow, activate mop
rotation, skimmer pumps, and a stopwatch. During the run,
obtain grab samples from the pump discharge at intervals
ranging from 5 seconds at the beginning of the run to 15
seconds near the end of the run. Shut off test oil dis-
tribution at a predetermined spot and continue towing
for two additional vessel lengths, or 24 metres. At this
point, stop mop rotation but leave the offloading pumps
operating.
4. When all fluid has been pumped from the mop wringer sumps
into the collection barrels, stop the offloading pumps and
stopwatch.
5. Using squeegees, scrape any oil in the drip tray into the mop
wringer sumps. Pump this fluid into the collection barrels,
timing the pump activation required. Record the total elasped
time the offloading pumps were operating.
TEST RESULTS AND DISCUSSION
Test Results
Results of the performance parameters TE (Throughput Efficiency)
and RE (Recovery Efficiency) are plotted in Figures 4 and 5.
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100 •-
6-S
CIEN
w
u
Q
50
0.6mHC*
Calm
Heavy Oil —.100
Light Oil
0.8 m x 12. A m
50
0 0.5 1 1.5 2 2.5
TOW SPEED, m/s
Figure 4. Throughput efficiency trends - Oil Mop Inc. ZRV.
100 -
u
w
o
o
50
Heavy Oil
Light Oil
Calm
•
0.6 m HC
a
0.6 m HC
*'*D
""Q
I
0.5
Figure 5.
1
2
2.5
1.5
TOW SPEED, m/s
Recovery efficiency trends - Oil Mop Inc. ZRV.
-iioo
50
-------
From Figure 4, it can be seen that: (a) TE was consistently better when
recovering light oil than when recovering heavy oil, (b) the TE curves
fell off gradually as tow speed increased, and (c) the TE curves for
light oil in calm water, 0.6 metre harbor chop and 0.8 x 12.4 metre
regular waves are all close together. These last two points indicate an
insensitivity to wave type and, to a lesser degree, tow speed over the
range of 1.0 to 2.5 m/s. Figure 5 shows that the RE performance parameter
is also relatively insensitive to tow speed and, to a lesser extent,
wave conditions for light oil.
Discussion
Initital checkout tests yielded two important results. First, the
maximum wave and tow speed conditions for subsequent oil tests were
established at a 3 m/s tow through a 0.8 x 12.4 metre wave train.
Pitching motions at this speed were such that, if they occurred during
actual spill operations, they would certainly induce the skimmer operator
to lower the forward speed to reduce pitching. Therefore, an upper
limit on the wave and tow speeds for the oil collection data runs was
set at 2.5 m/s through a 0.8 x 12.4 metre wave train. Second, during
checkout runs with heavy oil at 1 m/s, the 25 cm diameter mops jammed in
the bow wringer assembly. Since this condition did not exist at tow
speeds of 3 m/s with no oil or with light oil present, it was concluded
that heavy oil was causing the individual strands of polypropylene mop
to adhere to the wringer rollers, causing a jamming section either
forward or aft of the bottom powered roller. A second nonpowered roller
and a doctor blade comprised of angle iron placed close to the top power
roller were added, but neither solved the jamming problem. It was then
decided to conduct the first oil performance runs using light oil and
the 25 cm diameter mops, which did not jam, and later install smaller 15
cm diameter mops for the heavy oil tests.
Even with installation of the smaller 15 cm diameter mops for the
heavy oil tests, no data was obtained above 1.5 m/s due to the continued
wringer jamming problem illustrated in Figure 6.
10
-------
Powered
Rollers
Unpowered
Rollers
Normal Operation
(a) The Jamming Problem with
Heavy Oil.
Jam
(b) Addition of Second
Unpowered Roller
Jam
Jam
Jam
(c) Addition of Angle
Iron Doctor Blade
Figure 6. Oil Mop Inc. ZRV jamming conditions.
The majority of the tests were conducted with light oil. Adjustments
of the relative mop speed were made initially to determine the best
setting. Test runs confirmed that a zero relative velocity condition
between the rotating mops and the oil slick would yield the best TE
value.
The position of the data for heavy oil below 1.0 m/s was due to the
spreading of the test slick uniformly across the space between the
hulls. As the total width of the six mops did not completely fill up
this space, some oil passed between the mops and hulls and down the
11
-------
center line gap between the two groups of three mops. At speeds above 1
m/s, where the majority of the data were taken, the bow wave formed by
the catamaran hulls concentrated the oil slick against the two gangs of
three mops so that the mops could encounter a larger percentage of the
test oil. In general, it seemed that the performance of the skimmer
could be improved by placing the two gangs of three mops closer together
along the center line of the inner catamaran hull spacing.
Determination of the RE performance parameter is the most accurate
since it is directly measured and is independent of the oil slick en-
counter percentage. The TE and ORR parameters are very sensitive to an
accurate knowledge of the volume of oil encountered by the skimmer
during the test. For certain runs, the encounter percertage of the test
oil slick was not 100%. In these cases, an estimate of the encounter
percentage was made from sequential 35 mm slides taken of the slick
entering the skimmer bow during the test run. For some tests of this
kind the inaccuracy in the knowledge of percent encounter led to a
calculation of a TE value greater than 100%. In these cases, neither TE
nor the ORR which depends on the TE value were reported.
During the course of testing the following modifications were made
to improve performance:
(1) Set of six non-powered rollers across the drip pan.
(2) Splash shield to capture oil being thrown off the mops as they
are pulled up over the stern roller.
Due to time limitations, other modifications required to eliminate the
jamming problem with heavy oil above 1.5 m/s could not be performed.
After the conclusion of these tests, the bow wringer assembly was re-
designed by the manufacturer to prevent mop jams.
A complete set of tabular data is given in Tables 5 and 6.
12
-------
TABLE 5. TEST RESULTS - OIL MOP ZRV (HEAVY OIL) AVERAGE VISCOSITY; 3000 x 10-6m2/s
Test
no.
11
11A
12
13
13A
13B
13C
13D
15
ISA
15B
15C
19
19A
18B
19C
20
Tow
speed
m/s
1.0
1.0
1.0
1.0
1.0
1.0
1.5
1.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
Oil dlst.
rate
(m3/s)xlO-3
4.54
5.10
4.73
4.91
4.73
3.78
7.12
6.80
2.14
2.01
2.14
2.39
2.27
2.65
2.52
2.02
2.08
Slick
thick.
TTTm
3
3
3
3
3
3
3
3
3
3
3
3
2
3
3
3
3
Waves
m x m
0
0
0
0
0
0
0
0
0
0
0
0
0.
0.
0.
0.
0.
6HC
6HC
6HC
6HC
6HC
Encounter
%
100
100
100
100
100
100
100
100
100
100
100
100
50
75
65
70
45
Rel. mop
speed
m/s
0
0
0
*
*
*
0
0
0
0
. 0
0
0
0
0
0
0
Rec.
eff.
%
76
74
79
84
83
67
72
78
85
60
51
46
63
41
38
33
28
Thru
eff.
%
46
59
69
69
65
49
57
70
—
78
65
71
—
69
78
85
87
Oil rec.
rate
(m3/s)xlO-3
1.6
2.4
2.5
2.7
2.5
1.4
3.3
3.8
—
1.2
1.1
1.3
__
1.1
8.5
0.9
0.6
*max w/o slippage
-------
TABLE 6. TEST RESULTS - OIL MOP ZRV (LIGHT OIL) AVERAGE VISCOSITY; 9
10~6-2
TEST CONDITIONS
Test
no.
6B
25
25A
25B
26
26A
27
27A
27B
29
29A
30
30A
28
35
35B
35C
35A
36
36A
36B
38
37
32
32A
33
33A
Tow
speed
m/s
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.0
2.0
2.5
2.5
2.5
1.0
1.0
1.0
1.0
2.0
2.0
2.0
2.0
2.5
1.0
1.0
2.0
2.0
Oil dist.
rate
(m3/s)xlO~3
5.48
4.34
5.10
5.23
5.10
5.10
5.04
5.04
5.54
9.20
9.39
11.66
12.22
11.34
4.85
4.98
4.98
5.42
9.45
9.00
9.39
9.14
12.10
4.66
4.73
8.82
9.00
Slick
thick.
turn
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Uaves
m x m
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.6HC
0.6HC
0.6HC
0.6HC
0.6HC
0.6HC
0.6HC
0.6HC
0.6HC
0.8x12.4
0.8x12.4
0.8x12.4
0.8x12.4
Encounter
%
100
100
95
100
100
100
100
100
100
95
100
100
100
90
95
95
90
90
75
90
95
75
80
55
50
85
80
Rel . mop
speed
m/s
0
0
0
0
(+0.25)
(+0.25)
(+0.5)
(+0.5)
(+0.5)
0
0
0
0
0
0
0
0
(+0.25)
0
0
0
(+0.25)
0
0
0
0
0
TEST RESULTS
Rec.
eff.
%
65
63
75
78
65
64
69
59
59
64
60
49
52
44
50
57
58
50
42
48
42
37
36
53
69
40
49
Thru
eff.
%
84
62
90
78
61
52
52
58
51
72
62
49
44
36
58
86
88
56
62
72
52
52
42
__
51
79
Oil rec.
rate
(m3/s)xlO-3
3.5
2.1
3.5
3.2
2.5
2.1
2.1
2.3
2.2
5.0
4.7
4.5
4.2
2.9
2.1
3.1
3.1
2.1
3.5
4.6
3.7
2.8
3.3
__
3.0
4.5
-------
SECTION 3
CYCLONE! 050 SKIMMER
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
Oil collection performance tests were conducted with the Cyclonet
050 skimmer during the period 22 August to 2 September 1977. A total of
26 data runs were conducted with high viscosity (heavy) oil and 19 data
runs with low viscosity (light) oil.
Best Performance—
The highest average values of the three skimmer performance param-
eters, TE, RE, and ORR, for each of the heavy and light oil tests are
listed along with key test conditions in Tables 7 and 8 below.
TABLE 7. HIGHEST AVERAGE RESULTS - HEAVY OIL TESTS (CYCLONET 050)
Performance
parameter
TE
RE
ORR
TABLE 8.
Performance
parameter
ORR
Highest average
value
34%
27%
0.9 (x 10-3m3/s)
HIGHEST AVERAGE
Highest average
value
20%
12%
0.6 (x 10-3m3/s)
Tow speed
m/s
0.75
0.75
0.75
RESULTS - LIGHT
Tow speed
m/s
0.75
1.50
1.50
Wave condition
ht x length (m x
0
0.18 x 8
0
OIL TESTS (CYCLONET
Wave condition
ht x length (m x
0
0
0
m)
050)
m)
The above values are the highest of the averages of all individual
test results calculated for each test tank condition. Although certain
test results may be higher than the values listed above, the use of an
15
-------
average is more representative of the true value since it compensates
for unavoidable random experimental errors. For an overall indication
of the trends of the three performance parameters, the average values of
results are plotted in the Test Results section for each test tank
condition used.
Operating Limits—
Two major oil loss mechanisms were consistently observed in both
calm water and wave tests, and placed a definite upper limit on per-
formance. These oil loss mechanisms were:
(1) Vortex shedding of oil out the bottom of the convergent side
wall near the point of attachment to the hydrocyclone.
(2) Losses underneath the hull of the Zodiac boat at all speeds.
A number of preliminary tests were conducted to quantify the oil
losses from each of the above two mechanisms. Based upon these tests,
modifications (described in the TESTS RESULTS AND DISCUSSION section)
were made before any of the data reported here was collected.
Even with the modifications installed, test data show that the
speed range limits of the device in calm water are from 0.75 to 1.5 m/s,
with TE values below 10% in a 0.15 m harbor chop wave condition and a
tow speed of 0.75 m/s for light oil.
Mechanical Problems—
Mechanical problems encountered in obtaining good test data were
due to the required delicate adjustments of the two Cyclonet units with
respect to the Zodiac boat. Modifications to the convergent side wall
mouth of the skimmer, and pitch and yaw adjustments of the two skimmer
units were required to achieve the best test results. These modifi-
cations are described in the TEST RESULTS AND DISCUSSION section.
The diesel engine, pump and piping presented no mechanical problems
throughout the two week period.
Recommendations
The two weeks of OHMSETT testing provided a comprehensive perfor-
mance evaluation of the Cyclonet 050. Mechanisms which caused consistent
losses were examined. Adjustments were made to the design of the unit
under the direction of the manufacturer and the losses minimized. Any
further testing of the Cyclonet 050 should be performed under actual
field conditions to establish its operational usefulness.
SKIMMER DESCRIPTION
The Cyclonet 050 skimmer consists of two Cyclonet units mounted on
either side of an inflatable Zodiac boat. The skimmer was developed by
16
-------
Alsthom/Atlantique of Grenoble, France. The test version was manu-
factured under license in the United States. The oil slick enters the
front of the device into the convergent area, where it is concentrated,
and then the hydrocyclone chamber through the below-water entrance port.
Once inside the hydrocyclone chamber, oil and water are separated by
centrifugal action induced by the forward way of the device. Oil is
concentrated near the top of the chamber and pumped out of the unit to
storage while clean water is expelled to the sea through the exit port
of the hydrocyclone side wall. Symmetrical Cyclonet units are mounted
on either side of the Zodiac boat and connected to a common pump. The
pump is a diesel-driven, Spate induced-flow pump. Its maximum pumping
rate is approximately 6.3 x 10~3m3/s. The Cyclonet 050 tested had no
onboard storage for recovered oil. The manufacturer suggests the use of
collapsible pillow tanks placed inside the Zodiac boat. The skimmer
operator can adjust the flowrate out of each Cyclonet hydrocyclone by
means of valves on the common pump manifold and by adjusting the speed
of the pump diesel prime mover. The depth of each Cyclonet can be
adjusted by a hand winch. A typical crew consists of two men, the
outboard motor operator and skimmer operator.
The skimmer is 5.8 metres long and A metres wide, measured between
the outboard edge of each skimmer convergent. In normal operation the
Zodiac is powered by an outboard motor. For testing purposes, the
device was rigged between the towing bridges and towed down the test
tank. Figures 7 and 8 show the device under test at OHMSETT and a
schematic of its operation. Additional manufacturer specifications are
presented in Appendix D.
I
Figure 7. CYCLONET 050 under test.
17
-------
HYDROCYCLONE
CONVERGENT
Water Out
Figure 8. CYCLONE! 050 schematic.
TEST MATRIX AND PROCEDURES
Test Matrix
Tests for the Cyclonet 050 skimmer were conducted according to a
matrix consisting of shakedown runs, to establish maximum tow speed and
wave conditions, and oil data runs with heavy and light oils. Repeated
runs were made within the test matrix to examine areas of particular
interest. These areas included examining the performance of a single
Cyclonet hydrocyclone (as opposed to the complete skimmer system of two
hydrocyclones and the Zodiac boat) and performing a series of runs to
examine the maximum loading of a single hydrocyclone. Table 9 lists
test conditions for which oil collection performance data was obtained.
18
-------
TABLE 9. TEST MATRIX - CYCLONET 050
Test
mode
Slick
across both
both Cyclonets
and Zodiac
Slick into
one Cy clone t
Slick across
both Cyclonets
and Zodiac
Oil injected
directly into
one hydro-
cyclone
Tow speed
(m/s)
0.5
0.75
1.0
1.5
0.75
1.5
0.75
0.75
1.0
1.5
0.75
0.75
0.75
1.0
1.5
0.75
1.5
0.75
0.75
0.75
1.5
Slick
thk. (mm)
1
1
1
1
1
1
1
3
3
3
2
1
1
1
1
3
3
1
1
Waves
(m x m)
0
0
0
0
0.18 x 8
0.18 x 8
0.15 HC
0
0
0
0
0
0
0
0
0
0
0.15 HC
0.18 x 8
0
0
Test
oil
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Light
Light
Light
Light
Light
Light
Light
Light
Light
Procedures
For all tests the Cyclonet skimmer was towed with a bridle approx-
imately 3 metres behind the main towing bridge at a distance of approxi-
mately 7.3 metres from the tank's west wall. The test oil slick was
between 3 and 4 metres wide and confined by two floating ropes attached
to the outboard edge of each skimmer convergent side wall. Three dif-
ferent size collection barrels, 10.93 m3, 0.37 m3, and 0.06 m3, were
stationed on the auxiliary bridge.
Observations were made with 16 mm movie, 35 mm still, and under-
water video cameras. The bottom of the Zodiac boat was painted white and
the test oils were dyed red to ensure good photographic contrast for oil
escaping under the boat.
The final procedures for data collection were established during
initial shakedown tests with oil. Oil/water grab samples of the skimmer
pump discharge were taken at regular intervals for initial oil runs and
were plotted to determine when steady state was being reached. From
this information, the final test procedure was established for the oil
data test runs.
19
-------
Following the procedures of Table 10, it was possible to reasonably
ensure that the skimmer had reached a steady-state operational level and
that all oil collected during this steady-state period had been off
loaded into the collection barrels. However, to be certain steady-
state recovery efficiencies were being measured, discrete pump discharge
samples were continuously taken throughout all runs. A discussion of
the oil/water sampling procedures used during the 1977 OITC test series
is presented in Appendix B. Appendix C lists test oil properties.
TABLE 10. TEST PROCEDURES - CYCLONET 050
1. Start pump with discharge hose out of collection barrel.
2. Start main towing bridge when wave condition has stabilized.
Begin test oil distribution.
3. Start Scoreboard clock when oil reaches skimmers, clock
is initially set at number of seconds that oil is to be dis-
tributed, plus 45 seconds.
A. After clock has elasped 45 seconds, direct skimmer pump
discharge into collection barrels and begin collecting grab
samples at pump discharge connection.
5. Stop test oil distribution after 300 feet or equivalent
preset time.
6. Stop collecting samples and secure hose discharge when
Scoreboard horn sounds - as clock has counted down to zero.
7. Stop pump - begin tow back.
TEST RESULTS AND DISCUSSION
Test Results
During preliminary shakedown runs, it was quickly established that
the upper speed limit of Cyclonet 050 operation is about 1.5 m/s. The
convergents of the skimmers began to overflow at a tow speed of 2.0 m/s.
Tests with oil showed that the required forced vortex did not form in
the hydrocyclone chambers at speeds below 0.5 m/s. Waves selected for
oil data runs were the 0.18 metre x 8 metre long regular wave, a wave
longer than the Zodiac boat, and the 0.15 metre harbor chop. A 0.3
metre harbor chop was attemped but found to be too severe for the device.
It should be remembered that in tank testing, a skimmer is towed into an
oncoming wave train. At an actual spill, operation may be possible when
more severe waves are present by moving at a different relative heading.
Performance of the device in calm water peaked at TE - 38% at 0.75
m/s and decreased.to TE - 25% at 1 m/s and to about 18% at 1,5 m/s. At
20
-------
0.75 m/s in waves, additional turbulence and shedding of oil around the
skimmer were observed. This resulted in a decreased TE value to about
28% with the regular wave and to 17% with the harbor chop.
For light oil tests calm water baseline performance was again
established. Best performance was at 0.75 m/s with TE = 22%. Perfor-
mance decreased to about 14% at 1 m/s and then held steady to 1.5 m/s.
Tendency of the lighter oil to become mixed in the water column is the
primary reason that performance with light oil was reduced over that
with heavy oil.
To determine the maximum TE obtainable with the Cyclonet concept
(without Zodiac), the oil loss effect of the Zodiac was eliminated by
directing a single oil slick into the convergent mouth of one Cyclonet
unit. The results of this procedure show that the hull of the Zodiac
contributed to a decline in overall efficiency. It should be noted that
the difference in Throughput Efficiency between the single Cyclonet and
the complete Cyclonet-Zodiac assembly becomes less and less as the speed
increases. This confirms observations during the test that, as the
Zodiac's bow wave increased with speed, relatively more oil was forced
to the sides and into the two Cyclonet convergents rather than under-
neath the boat. Figures 9, 10, and 11 depict the Cyclonet 050's per-
formance trends graphically. Figures 12 and 13 follow to identify the
underside portion of the device and observed losses under tow.
The results shown in Tables 11 and 12 contain data from 45 data
runs out of a total of 74 test runs (48 with heavy oil and 26 with
light oil). The remaining runs were rejected because modifications to
maximize performance were not complete, correct procedures were not
followed, or the results were not repeatable.
21
-------
G
§
W
H
I
100 •-
80
60
40
20
Calm
0.18 m x 8 m Wave
-•100
80
60
40
20
0.15 m HC
Figure 9.
100 r-
w
40
20
0
O.S 1 1.5 2
TOW SPEED, m/s
Throughput efficiency (heavy oil) - CYCLONET 050.
-•100
0.18 m x 8 m Wave
0.15 m HC
n,
1D
a
Calm
I
•D
I
60
40
20
0.5 1 1.5
TOW SPEED, m/s
Figure 10. Throughput efficiency (light oil) - CYCLONET 050.
22
-------
100
u
-•
U
. •
-
O
a
20
I
-,100
Heavy Oil
No Waves
Double CYCLONET
and ZODIAC
I
Single CYCLONE!
60
40
20
0 0.5 1 1.5
TOW SPEED, m/s
Figure 11. Throughput efficiency - single vs. double CYCLONET
050.
Figure 12. Bow underview - CYCLONET 050 and Zodiac.
23
-------
Figure 13. Underwater view - CYCLONE! 050 (No waves, 0.75 m/s tow).
-------
TABLE 11. TEST RESULTS - CYCLONET 050 (HEAVY OIL) AVERAGE VISCOSITY; 550 x lQ-6m2/s
ro
en
TEST CONDITIONS
Test
no.
20
20A
16
19
19A
26
18
18B
18C
21
21A
22
22A
23
23A
28
28A
15R
25
24
29
30
32
32A
31
31A
Tow
speed
m/s
0.5
0.5
0.75
0.75
0.75
0.75
1.0
1.0
1.0
1.5
1.5
0.75
0.75
1.5
1.5
0.75
0.75
0.75
1.0
1.5
0.75
0.75
0.75
0.75
1.5
1.5
Oil dist.
rate
(m3/s)xlO-3
2.4
1.8
2.5
2.8
2.5
2.8
3.1
3.5
3.0
4.4
4.8
2.8
2.5
4.5
4.4
2.8
2.6
6.6
9.5
12.8
1.1
1.4
.4
.8
1.0
1.3
Slick
thick.
imp
1.6
1.2
1.0
1.2
1.0
1.1
1.0
1.1
0.9
1.0
1.0
1.2
1.1
1.0
0.9
1.2
1.1
2.9
3.1
2.8
*
*
*
*
.8
1.2
Waves
m x m
0
0
0
0
0
0
0
0
0
0
0
0.18x8
0.18x8
0.18x8
0.18x8
0.15HC
0.15HC
0
0
0
0
0
0
0
0
0
Encounter
%
100
100
95
100
100
95
95
100
100
98
100
95
95
100
100
95
98
90
90
95
98
98
100
98
100
100
Pumping
rate
mVsxlO-3
3.4
3.6
3.7
3.9
3.6
4.6
3.6
3.7
3.7
3.8
3.7
1.9
4.0
2.8
3.0
4.7
4.6
3.6
5.2
5.3
3.6
3.6
3.6
3.6
3.1
3.4
TEST RESULTS
Rec.
eff.
%
22
17
20
18
25
25
17
8
19
16
28
42
13
8
10
7
9
50
14
19
7
15
6
15
2
3
Thru
eff.
%
32
34
31
25
36
43
21
8
23
14
21
30
21
2
7
13
16
30
9
9
24
40
50
70
6
7
Oil rec.
rate
(m3/s)xlO~3
0.8
0.6
0.8
0.7
0.9
1.2
0.6
0.3
0.7
0.6
1.0
0.8
0.5
0.3
0.3
0.4
0.4
2.0
0.8
1.1
3.0
0.6
0.2
0.6
0.1
0.1
*Single slick only
-------
TABLE 12. TEST RESULTS - CYCLONE! 050 (LIGHT OIL) AVERAGE VISCOSITY; 22 x 10~6m2/s
Test
no.
33
33A
34
34A
35
35A
36
36A
37
37A
40
40B
41
41A
43
43A
43B
43C
44
Tow
speed
m/s
0.75
0.75
1.0
1.0
1.5
1.5
0.75
0.75
1.5
1.5
0.75
0.75
0.75
0.75
0.75
0.75
0.75
0.75
1.5
TEST
Oil dist.
rate
(m3/s)xlO'
2.9
2.8
3.1
3.4
5.2
5.0
7.3
7.5
14.0
15.4
2.6
2.4
2.4
2.2
1.3
2.1
2.3
3.6
2.3
CONDITIONS
Slick
thick. Waves
.3
tnm m x EI
1.3
1.2
1.0
1.1
1.1
1.1
3.1
3.2
3.0
3.3
1.1
1.0
1.0
1.0
*
*
*
*
*
0
0
0
0
0
0
0
0
0
0
0.15HC
0.15HC
0.18x8
0.18x8
0
0
0
0
0
Encounter
90
90
95
98
98
95
85
90
90
95
95
90
95
95
100
100
100
100
100
Pumping
rate
4.9
4.6
4.7
4.7
4.7
4.8
5.1
4.9
5.1
5.2
5.0
4.4
4.4
4.2
3.1
3.2
3.2
3.2
3.1
TEST RESULTS
Rec . Thru
eff. eff.
1 % %
10
12
7
9
12
13
13
14
10
9
3
3
13
5
47
62
66
90
57
19
22
11
13
11
13
11
10
4
3
6
6
25
10
112
97
89
80
78
Oil rec.
rate
(m3/s)xlO~3
0.6
0.6
0.4
0.4
0.6
0.6
0.8
0.8
0.6
0.5
0.2
0.2
0.6
0.3
1.4
2.0
2.1
2.9
1.8
*oil injected into Cyclonet
-------
Discussion
Several modifications were made to the Cyclonet and Zodiac to
improve performance. In initial test runs, underwater video revealed
that few losses were observed at the underwater hydrocyclone exit port,
indicating that the device was not overloaded with oil. However,
significant oil losses were seen coming from under the outboard con-
vergent side walls of the Cyclonet collectors and between the sides of
the Zodiac and the inboard convergent walls. Most serious was the oil
loss from a vortex in the convergent area just forward of the hydro-
cyclone entrance port. To reduce the oil losses from these various
causes, certain modifications were performed:
(1) To reduce vortex shedding with the convergent area a tri-
angular portion on the convergent was removed.
(2) To prevent losses between the boat and the convergent and to
smooth the flow into the convergent entrance, the convergent
was pulled against the side of the Zodiac with a cable jack.
(3) To reduce convergent oil losses, weight was moved aft to raise
the relative pitch of the Cyclonet 5 degrees.
(4) To decrease oil shedding and Improve concentration of oil
inside the convergent, the debris screens were removed.
Performance improved signficantly after the above modifications
were made, although oil losses by vortex shedding in the convergent area
were still observed and the performance of the device was still sen-
sitive to other skimmer adjustments of height and yaw angle of the tow.
The modifications as mentioned are detailed in Figure 14.
27
-------
(a) Side View
Removed
Exhaust Port
Shaded Area Removed
Oil Loss
Vortex Shedding
Hydrocyclone
Chamber
Pulled to I
J L
Hydrocyclone Chamber
Oil Loss Gap
Convergent
Convergent wall
pulled to boat
Zodiac
Boat
(b) Plan View
Oil Slick
Figure 14. Modifications to CYCLONE! 050
28
-------
A final effort was made to establish the upper limits of the Cyclonet
hydrocyclone concept excluding all the oil loss mechanisms listed above,
which are unique to the Cyclonet-Zodiac combination. This was accomplished
by directing the test oil distribution hose to discharge directly
into the Cyclonet hydrocyclone entrance port, thus completely bypassing
the Zodiac boat and convergent. The results of this direct injection
procedure indicate a Recovery Efficiency of 54% for a corresponding
Throughput Efficiency of 100%. For a constant tow speed, as the oil
distribution rate increases, the Recovery Efficiency increases, but at
the expense of Throughput Efficiency due to the hydrocyclone becoming
overloaded. A single data run at a higher tow speed of 1.5 m/s was
conducted as a spot check for sensitivity of this behavior to speed.
The results of this effort are represented in Figure 15.
100
80
60
§
M
I
W
20
-llOO
Throughput
Efficiency
D
Recovery
Efficiency
Tow Speed (Calm Water)
0.75 m/s
1.5 m/s
I
60
40
20
Figure 15.
1234
TEST OIL DISTRIBUTION RATE x 10-3m3/s
Maximum performance limits with direct injection of light
oil into chamber - CYCLONET 050.
It can be concluded from this test series that, for maximum Throughput
Efficiency with light oil, the Recovery Efficiency will be about 50% and
that the majority of oil is lost from under the Zodiac and in the con-
vergent before the oil gets a chance to enter the entrance port to the
hydrocyclone chamber.
Throughout the two week test period, no mechanical problems were
encountered with the pump, the diesel engine, or valves and fittings.
The device was ready for skimming once the diesel was primed and started.
The Zodiac boat lost air pressure and took on water overnight. Wooden
29
-------
floor boards were very slippery and required matting for safety.
As a result of the performance data obtained in these tests, the
manufacturer is now offering a removable deep draft bow section for the
Zodiac to prevent oil losses under the shallow draft unmodified Zodiac.
This addition also serves to direct more oil into the Cy-.lonet con-
vergents on either side of the Zodiac.
30
-------
SECTION 4
CLOWSOR SKIMMER
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
During the period 6 to 16 September 1977, 32 oil collection performance
data tests were conducted with the Clowsor skimmer. A total of 21 of
these tests were conducted with high viscosity (heavy) oil and 11 tests
conducted with low viscosity (light) oil.
Best Performance—
The highest average values of the 3 performance parameters TE, RE,
and ORR for each of the heavy and light oil tests are listed in the
tables below.
Performance
parameter
TE
RE
ORR
TABLE
Performance
parameter
TE
RE
ORR
Highest average
value
96%
91%
6.0 (x 10-V/s)
14. HIGHEST AVERAGE
Highest value
value
61%
65%
3.4 (x HTV/s)
Tow speed
m/s
0
0
0
RESULTS - CLOWSOR
Tow speed
m/s
0.37
0
0
Wave condition
ht x length (m
0
0
0
(LIGHT OIL)
Wave condition
ht x length (m
0
0
0
x m)
x m)
The above values are the highest of the averages of all individual test
results for each test tank condition.
Operating Limits—
Depending upon slick thickness, the Clowsor showed itself capable
31
-------
of achieving very high Oil Recovery Rates. The highest rate recorded
during these tests was with heavy oil in which the slick thickness
reached a maximum of approximately 300 mm during the test and the Oil
Recovery Rate reached a maximum value of 6.4 x 10~3 cubic metres per
second. An oil recovery rate in excess of this value could have been
attained had the supplied pumps been able to off load the skimmer at a
higher flowrate.
There are 4 factors which limit the performance of the Clowsor
skimmer:
(1) Currents in excess of 0.25 m/s.
(2) Waves in excess of 0.3 metre harbor chop.
(3) Paddle speeds greater than 2.5 rpm.
(4) Oil with viscosity less than about 20 x 10~6m2/s.
Recommendations
The Clowsor skimmer as tested at OHMSETT performed according to its
design goals as a high volume oil skimmer for high viscosity oil spills
under low wave and low current conditions. The concept of a paddle and
perforated ramp combination has been well executed in construction of
this skimmer. The range of applicability of the skimmer has been de-
termined during these tests as described in the Operating Limits para-
graph above. It is recommended that any further performance tests be
conducted during actual spills.
SKIMMER DESCRIPTION
The Clowsor skimmer, manufactured by Anti Pollution, Inc., of
Morgan City, Louisiana, is designed as a stationary skimmer operating in
calm water and low currents. The Clowsor paddle-perforated ramp concept
is available in a number of different sizes for use in shallow or deeper
water. The physical dimensions and weights of the manned skimmer tested
are listed in Appendix D.
In operation, the oil slick is pulled up a perforated inclined ramp
by 4 rotating paddles. As a wedge of oil and water is drawn over the
perforated inclined ramp, any water present in the wedge settles down-
ward and passes through the holes in the plate, leaving an oil-rich
mixture behind. The paddle pulls the oil-rich fluid wedge up over the
top of the incline and into a sump where it is pumped off the skimmer.
For these tests, large pumps located on the auxiliary bridge behind the
skimmer were used to offload collected oil. In field operation, onboard
pumps or shore based vacuum tanks are used to empty the sump. Water
settling downward through the holes in the ramp exits from the skimmer
through flapper check valves in the bottom of the unit. These valves
also prevent surging of water upward through the perforated ramp.
32
-------
An additional feature of the skimmer is the use of an air floa-
tation oil boom and hydraulic motor recovery reel mounted on the star-
board side of the skimmer. This boom is deployed around an oil slick
and is secured to the opposite side of the skimmer. Powered retrieval
is provided by the hydraulic motor mounted atop the boom recovery reel.
When the boom is then reeled in, the contained area in front of the
skimmer decreases in area, greatly increasing the oil slick thickness
and allowing the paddles to recover more oil and less water.
The skimmer is outfitted with double-pinned standoff struts. These
struts allow the skimmer to respond to waves when attached to the bow of
a larger vessel such as a barge or small tugboat. During these tests,
the struts were bolted to the auxiliary bridge extending across the
tank. The Clowsor is shown undergoing a stationary test in Figure 16
and its operating principle is diagrammed schematically in Figure 17.
Figure 16. CLOWSOR under stationary test,
33
-------
Oil Out
Floatation
Ballast
Paddles
Water Forces Through
Ramp and Out
lapper Check Valves
Travel 1>
Figure 17. Clowsor Schematic.
TEST MATRIX AND PROCEDURES
Test Matrix
The Clowsor skimmer was tested in the following three modes of
operation:
(1) Encircling boom mode.
(2) Stationary mode in thick oil slicks.
(3) Towed mode to simulate currents.
A matrix of the conditions for tests of each of these three con-
figurations is presented in Table 15.
34
-------
TABLE 15. TEST MATRIX - CLOWSOR
Test
mode
Tow speed
(m/s)
Slick
thk. (mm)
Waves
(m x m)
Test
oil
Encircling boom
51
Heavy
Stationary
Towed
Stationary
Towed
0
0
0
0
0
0
0
0
0.25
0.37
0.25
0
0
0
0
0.25
0.37
0.25
13
26
26
26
0-51
0-300
0-22
0-37
4
4
4
0-22
0-51
0-341
0-275
4
4
4
0
0
0.2 x 8
0.3 HC
0
0
0
0
0
0
0.3 HC
0
0
0
0
0
0
0.3 HC
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Light
Light
Light
Light
Light
Light
Light
Procedures
The procedures for each of the three test configurations are outlined
in Tables 16 through 18. During the latter two series of tests, two
difficulties were encountered in collecting repeatable data. First, the
two large centrifugal pumps located behind and above the skimmer on the
auxiliary bridge tended to lose prime. Second, during some of the high
volume flow stationary tests, the oil distribution hose outlet was under
the water surface, causing water to become entrained with the rising oil
as it surfaced to form the test slick. A splash plate was added to
ensure distribution of oil above the water line, and all subsequent
tests were performed with this technique. Comparing results of test
runs under similar conditions showed that not using a splash plate
caused an additional water content of about 10% to appear in the oil
presented to the skimmer which the skimmer was not able to separate.
Appendix B gives sampling procedures, and Appendix C lists test oil
properties.
35
-------
TABLE 16. TEST PROCEDURES - CLOWSQR (ENCIRCLING BOOM)
1. Pump skimmer collection well dry.
2. Deposit test oil within the encircling boom area in front of
the skimmer and activate the skimmer paddles, off loading pump and
a stopwatch.
3. Obtain grab samples from the pump discharge at varying
time intervals during the run.
4. When the Clowsor operator signals that all the oil
has been drawn up the ramp into the sump, continue to
run the pump until all liquid is pumped out of the sump
and secure the stopwatch.
5. Fill the skimmer sump with water from a fire hose and
activate the pump and stopwatch until water appears at the
end of the discharge hose at the collection barrel, then
take the hose out of the barrel, and secure the pump and
stopwatch. From the stopwatch, record the total time the
pump was on during the test.
TABLE 17. TEST PROCEDURES - CLOWSOR (STATIONARY)
1. Fill skimmer collection sump with water and activate pumps
to establish prime in the pump suction hoses.
2. Activate distribution of test oil into the boomed area in front
of the skimmer. At the same time, activate the skimmer paddles,
off loading pumps, and stopwatch.
3. During the run, upon signal from the Clowsor operator, adjust
the pump discharge valves to maintain a nearly constant level
in the skimmer sump to avoid gross changes in skimmer draft.
4. During the run, obtain grab samples from the pump discharge.
5. After a predetermined time interval, usually five minutes, stop
test oil distribution. Continue operating the skimmer paddles
until the Clowsor operator signals that all oil has been col-
lected. Continue to operate pumps until the skimmer sump is
almost dry and then secure pumps, fill the sump with water from
a fire hose, and continue pumping into the collection barrels
until clear water is observed coming out the end of the dis-
charge hose. Secure the pumps and stopwatch and record the
total pump activation time.
36
-------
TABLE 18. TEST PROCEDURES - CLOWSOR (TOWED)
1. With the skimmer sump filled with water to the proper ballast
level, start the tow down the tank and, at a predetermined point,
activate test oil distribution.
2. When the test oil slick contacts the front of the paddles, activate
the paddles, off loading pumps and stopwatch.
3. Using the choking valves on the discharge side of the off loading
pumps, continually adjust the flow rate as directed by the
Clowsor operator to maintain a nearly constant ballast level
in the skimmer collection sump.
4. Througout the run, obtain grab samples from the pump discharge.
5. At a predetermined point along the tank wall, secure test oil
distribution and, at the discretion of the Clowsor operator, secure
the paddles before the end of the tow. Continue operating the
off loading pumps until the level of the skimmer sump is almost
dry. At this point, fill the skimmer sump with water from a fire
hose and continue pumping into the collection barrels until clear
water is seen coming out the end of the discharge hose. Secure the
pumps, stop timing, and record the total pump activation time.
TEST RESULTS AND DISCUSSION
Test Results .
Only three tests were run in the encircling boom mode. It was
concluded at the end of these three tests that the boom concept would
greatly speed oil slick pickup and further testing would not yield any
new information.
In the stationary mode tests, conducted in calm water, Recovery
Efficiency for heavy oil was consistently in the 85-95% range over a
wide variation of oil distribution rates, while a slight decrease in
Recovery Efficiency occurred with light oil for increasing oil dis-
tribution rates. Performance with regular and harbor chop wave con-
ditions decreased significantly.
In the third configuration tested, the skimmer was slowly towed to
simulate stationary operation in the presence of a light current. The
effect of waves on performance diminished Recovery Efficiency. Ad-
ditionally, performance in calm water at tow speeds greater than 0.25
m/s seemed to be decreasing rapidly, based upon underwater observation
of the oil droplet cloud pushed underwater by the rotating paddles.
Discussion
A significant reduction in performance in the presence of waves was
37
-------
observed. This is due primarily to the action of the large surface area
paddles slapping the water in front of the skimmer and breaking up the
oil slick into droplets. With a usual rotation speed of 1 revolution
every 24 seconds, the speed of each paddle tip is approximately 13 cm/s.
Even in calm water with no waves, this top speed caused a rather large
oil droplet cloud to form in front of the skimmer. This droplet cloud
was eventually recovered by the stationary skimmer as the oil droplets
resurfaced inside the boomed area in front of the skimmer. However,
under tow and in the presence of waves, this oil droplet cloud moved out
of the protective area of the encircling boom in front of the skimmer
and was lost. Vortices were formed at the paddle edges and appeared to
be a major source of the oil entrainment.
No modifications were necessary to optimize performance of the
Clowsor skimmer. Figure 18 shows the device under tow and Figures 19
through 21 graphically depict the performance trends of the Clowsor
skimmer. Tables 19 and 20 follow which include tabular data derived
from this study.
Figure 18. Underwater view - CLOWSOR (no waves, 0.25 m/s tow speed)
38
-------
100
§
H
O
M
W
O
O
8
50
No Waves
D
Heavy Oil
Light Oil
•D
100
50
05 10 15 20 25
TEST OIL DISTRIBUTION RATE x 10"3m3/s
Figure 19. Recovery efficiency trends (stationary tests) - CLOWSOR.
39
-------
100 •-
O
W
8
3
50
-ilOO
Calm
0.3 m HC
0.2 x 8 m
I I
I A I
10
\ I i
T "
20 30 40 50 T 100 T 300
SLICK THICKNESS, (mm)
50
500
Figure 20. Recovery efficiency trends (stationary tests -
heavy oil) - CLOWSOR.
100
-• 100
50
w
Calm
Calm
Heavy Oil
D Light Oil
50
D
0.3 m HC
0.3 m HC
I
0.5
2
2.5
1 1.5
TOW SPEED, tn/s
Figure 21. Recovery efficiency trends (towed) - CLOWSOR.
40
-------
TABLE 19. TEST RESULTS - CLOWSOR (HEAVY OIL) AVERAGE VISCOSITY
TEST CONDITIONS
Test
no.
7A
7B
7C
8
8A
9
9A
10A
10B
11A
12
13
14B
1AC
ISA
±5B
17
17A
18
19
19A
Tow
speed
m/s
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.25
0.25
0.37
0.25
0.25
Oil dlst.
rate
(m3/s)xlO~3
0
0
0
0
0
0
0
0
0
0
5.7
16.4
1.6
1.6
3.2
3.2
3.2
3.2
4.7
3.2
3.2
Slick
thick.
roip
51
51
51
13
13
26
26
26
26
26
0-51
0-300
0-22
ND
0-37
0-30
4
4
4
4
4
Waves
m x m
0
0
0
0
0
0
0
0.2x8.0
0.2x8.0
0.3HC
0
0
0
0
0
0
0
0
0
0.3HC
0.3HC
Total test
oil down
m3
0.6
0.6
0.6
0.1
0.1
0.3
0.3
0.3
0.3
0.3
3.5
5,6
0.5
0.9
0.9
0.9
0.9
0.9
0.8
0.9
0.9
Paddle
speed
rpm
*
*
A
*
*
*
*
*
*
*
*
*
*
*
*
*
2.4
2.5
1.4
2.4
2.4
TEST RESULTS
Rec.
eff.
%
87
83
80
58
82
78
84
7
11
35
84
91
94
93
94
89
88
89
86
40
35
Thru
eff.
%
96
96
96
91
91
93
71
72
66
97
96
66
71
__
85
88
99
78
78
Oil rec.
rate
(m3/s)xlO-3
1.8
1.5
1.9
0.4
2.1
2.6
1.4
1.5
1.1
4.8
6.0
0.7
ND
__
1.7
1.5
3.5
1.7
ND
*paddle speed varied by operator
-------
TABLE 20. TEST RESULTS - CLOWSOR (LIGHT OIL) AVERAGE VISCOSITY: 14 x 10~6m2/s
TEST CONDITIONS
Test
no.
23
23A
24
24A
25
25A
20
20A
21
21A
22
Tow
speed
m/s
0
0
0
0
0
0
0.25
0.25
0.24
0.25
0.37
Oil dist.
rate
(mVs)xlO-3
1.6
1.6
3.2
3.2
19.0
19.0
3.2
3.2
3.2
3.2
4.7
Slick
thick.
mm
ND
0-22
0-51
0-20
0-341
0-275
4
4
4
4
4
Waves
m x m
0
0
0
0
0
0
0.3HC
0.3HC
0
0
0
Total test
oil down
m3
0.5
0.5
0.9
0.9
4.6
3.8
0.9
0.9
0.9
0.9
0.8
Paddle
speed
rpm
2.4
3.5
2.5
2.5
ND
ND
ND
ND
ND
3.5
ND
TEST RESULTS
Rec.
eff .
%
60
67
66
65
47
52
16
17
63
61
64
Thru
eff.
%
63
81
36
49
50
74
41
43
67
50
65
Oil rec.
rate
(m3/s)xlO-3
ND
0.8
1.3
2.4
3.0
3.8
1.1
1.1
1.5
0.8
1.8
-------
SECTION 5
BENNETT MARK 6E SKIMMER
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
Best Performance—
During the period 17 to 28 October 1977, a total of 99 data runs
were performed with the Bennett Mark 6E skimmer. A total of 62 runs
were conducted with heavy oil and 37 runs with light oil. The test
results at each set of test conditions were averaged to take into account
random testing errors. The highest of these averages for each type of
oil is presented in Tables 21 and 22 below. The use of the highest
average test results over all test conditions is more representative of
the true value because random experimental errors are averaged out.
TABLE 21. HIGHEST AVERAGE RESULTS - BENNETT MARK 6E (HEAVY OIL)
Performance
parameter
TE
RE
ORR
Highest average
value
95%
88%
6.8 (x 10"3m3/s)
Tow speed
m/s
1.5
0.5
1.0
Wave condition
ht, m
0.3
0
HC
0
TABLE 22. HIGHEST AVERAGE RESULTS - BENNETT MARK 6E (LIGHT OIL)
Performance
parameter
TE
RE
ORR
Highest average
value
90%
64%
2.3 (x 10-V/s)
Tow speed
m/s
0.75
1.25
1.0
Wave condition
ht, m
0
0
0
Operating Limits—
The performance of the Bennett Mark 6E skimmer as determined by
Throughput Efficiency appears to be limited by four factors:
43
-------
(1) Wave-following ability of the bow ramp.
(2) Degree of turbulence inside the skimmer as a function of forward
skimmer speed and specific positions of the forward and aft
gill doors, and bow ramp depth.
(3) Physical properties of oil.
When operating in waves, the bow ramp must be lowered to remain
below the water surface as the skimmer heaves. Tests showed that the
wave-following ability of the ramp was affected by wave steepness and
attempts to lower the ramp in the 0.3 m harbor chop produced increased
turbulence in the area of the collection belt, thus causing more oil
droplets into suspension and reduced Throughput Efficiencies.
Sensitivity to oil properties and velocity was observed in the
comparison of speeds at which TE on the average dropped to below 50%.
With heavy oil, this occurred at a forward speed of 2.75 m/s, while with
light oil at about 1.25 m/s. Operational effectiveness is thus determined
by the tendency of specific oils to become mixed into the water column,
exiting the skimmer via the forward and aft gill doors.
The effectiveness of this device with respect to TE is directly
related to the stability of the oil/water interface and is seen to
diminish as turbulence increases.
Mechanical Limits—
The performance of the device is directly sensitive to operator
controlled skimmer settings of the bow ramp and gill doors. Several
test runs were required for each condition to find the right combination
of settings. The oil off loading rate was limited due to squeeze belt
mechanical problems and the pressure of the squeeze belt was not suf-
ficient to force all the oil from within the collection belt. This
overload of the collection belt with excess oil was more pronounced with
light oil than with heavy oil. In heavy oil tests, oil was removed from
the collection belt primarily by a doctor blade assembly.
Recommendations
The Bennett Mark 6E skimmer is a self-contained, powered skimmer
showing good performance for collecting oil in moderate wave conditions.
The number of moving parts requires a skilled operator familiar with the
device in order to set the interdependent adjustments for best oil
pickup performance.
A number of modifications are recommended to Improve performance.
Two would be particularly helpful. First, the squeeze belt mechanism
needs increased pressure against the collection belt to ensure removal
of all collected oil. Second, adjustment controls for the underwater
bow and gill door settings should be simplified and designed to aid the
skimmer operator, and indicators should be provided.
44
-------
The basic performance limits have been established in this test
series. Additional testing should be performed (after the recommended
modifications have been made) to establish performance with different
oils.
SKIMMER DESCRIPTION
The Mark 6E skimmer, manufactured by Bennett Pollution Controls,
Ltd., of Vancouver, Canada, is an inshore, self-propelled skimmer. The
hull design, a semi-catamaran type, consists of three sections: two
outer catamaran-like hulls attached to either side of a center machinery
section. The outer hulls contain the transfer pumps and ballast com-
partments. The skimmer measures 11.25 m in length overall with a beam
of 3.9 m. A helmsman and an oil recovery operator are the two crewmen
required for skimmer operation. Additional skimmer specifications are
provided in Appendix D. Figures 22 and 23 follow, showing the device
under test and a schematic of operation.
Figure 22. BENNETT MARK 6E under test.
-------
Squeeze Belt
Oil Out
Absorbent Belt
Oil Out
Bow Ramp
Gill Doors
Skimmer Travel
Figure 23. BENNETT MARK 6E schematic of oil collection principle.
The device combines three separate processes for oil/water separation.
First, the volume and speed of the oil slick entering the skimmer is
regulated by a bow ramp and two gill doors in the floor of the skimmer.
The thickness of the layer of water which must be processed with the
floating oil entering the skimmer is controlled by adjusting the bow
ramp. Opening or closing the gill doors controls the rate at which the
floating oil slick moves aft to the rotating, absorbent, polyester wool
collection belt. Second, the backward facing, inclined collection belt,
which is both oleophilic and hydrophobic, absorbs oil off the water
surface, and carries it up to a perforated squeeze belt where the oil is
squeezed out into a sump. The third process for collecting oil consists
of a baffled overflow weir collection box. Any oil which misses the
rotating absorbing belt, due to large oil slick thickness or high
forward skimmer speed, is forced under the weir box and up into the
quiescent area inside. Oil from the weir box is piped into the oil
transfer pumps and offloaded along with oil from the squeeze belt sump.
TEST MATRIX AND PROCEDURES
Test Matrix
After preliminary shakedown tests to finalize procedures and establish
tow and wave limits, test runs were conducted with the Bennett Mark 6E
skimmer with both heavy and light oil in various wave conditions in
accordance with the test matrix in Table 23. Initial tests established
a calm water performance baseline for heavy oil, followed by tests in
waves and finally with a high rate of oil slick loading into the device.
Light oil tests were run in the same manner except that high rate oil
slick loading runs were not performed.
46
-------
TABLE 23. TEST MATRIX - BEHNET MARK 6E
Tow speed
(m/s)
0.5
1.0
1,25
1.5
1.75
2.0
2.25
2.5
2.75
3.0
0.5
0.75
1.0
0.5
0.75
1.0
1.25
1.5
1.75
0.75
1.0
1.25
1.5
1.0
0.5
0.75
1.0
1.25
0.5
0.75
1.0
0.5
0.75
Slick
thk. (mm)
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
12
3
3
3
3
3
3
3
3
3
Waves
(m x m)
0
0
0
0
0
0
0
0
0
0
0.18 x 8
0.18 x 8
0.18 x 8
0.3 HC
0.3 HC
0.3 HC
0.3 HC
0.3 HC
0,3 HC
0.6 HC
0.6 HC
0.6 HC
0.6 HC
0
0
0
0
0
0.3 HC
0.3 HC
0.3 HC
0.6 HC
0.6 HC
Test
oil
Heavy
Heavy
Heavy
Heavy
Heavy
Heavy
Light
Light
Light
Procedures
A number of preliminary shakedown runs were necessary to establish
testing procedures for this device. The main problem in finalizing pro-
cedures was to ensure the presence of a consistent steady-state operating
period for the device during the relatively short tow time down the
tank.
Once the steady-state behavior of the device was determined by
numerous discrete grab samples during checkout tests* a single, con-
tinuous bleed sample procedure was implemented. This arrangement worked
47
-------
particularly well since the Recovery Efficiency of the rotating absorbing
belt remained relatively constant for each oil and the positive dis-
placement pump provided a homogenous oil/water sample. As a result,
test run turnaround times were reduced since the composite sample from
the large collection barrel on the auxiliary bridge was not required.
The device contains a large internal surface area. To achieve data
consistency with the relatively small test oil slick volumes used (about
0.3 m3), it was necessary to keep a constant oil prime within the
skimmer. Several priming runs were sufficient to reach a constant state
at the start of each day, or after skimmer adjustment. During testing,
the oil slick entering the mouth of the skimmer was carried to the
absorbing belt by the surface currents due to the skimmer's forward
speed through the water. After towing ceased at the end of a test run,
a fire hose was used to maintain this surface current to enable the
remaining floating oil to reach the rotating belt. The skimmer was not
flushed completely with the fire hose; a constant residual volume of oil
was allowed to remain on the inside surfaces of the skimmer as a "prime"
between each run.
The procedure used for all data runs is listed in Table 24. Appendix
B gives sampling procedures, and Appendix C lists test oil properties.
In addition to normal test data, the following skimmer adjustments were
also recorded:
(1) Bow and gill door settings.
(2) Belt speed.
(3) Belt depth.
TABLE 24. TEST PROCEDURES - SENNET MARK 6E
1. Start skimmer engine and set bow and gill doors as required.
2. Start main towing bridge and oil distribution as required
for the towing speed.
3. Start oil collection belt. When oil has reached the belt
surface, time belt speed with a stopwatch.
4. Begin pumping out collected oil from the sump and begin taking
grab samples. Collect the discharge oil in the collection
barrels on the auxiliary bridge.
5. Stop oil distribution rate after 91.4 m, continue towing.
6. Close bow ramp door when the last of the oil slick enters
the device. Hose oil back towards the collection belt as
the towing bridge slows down.
(Continued)
48
-------
TABLE 24. (Continued)
7. Continue hosing the captured oil towards the belt until oil
is no longer being collected by the belt. Stop stopwatch
and secure grab samples.
8. Pump the oil discharge line dry with the onboard pump, mark
collected oil volume height on collection barrel.
TEST RESULTS AND DISCUSSION
Test Results
Calm water tests with heavy oil were conducted at speeds of up to 3 m/s.
Successful oil collection occurred above 1.5 m/s because of the ability
of the bow ramp to take a thin cut just below the oil slick. Once the
oil slick was within the skimmer hull, surface velocities were greatly
reduced, allowing oil pickup by the rotating collection belt in a low
velocity region. The bow waves produced by each catamaran hull helped
concentrate the oil down the center line of the skimmer's interior.
In calm water, the device produced an average TE value of 95% at
0.5 m/s with performance diminishing as speed approached 3 m/s. Through-
put efficiency in a 0.3 m harbor chop ranged from 89% at 0.5 m/s to 77%
at 1.0 m/s. Beyond this, performance dropped to about 42% at 1.75 m/s.
With a 0.6 m harbor chop, the TE was about 50% from 0.75 to 1.5 m/s. As
can be seen from the differences in TE values between calm and wave
conditions, the device is sensitive to waves and is limited by the
maximum wave height of approximately 0.6 m.
With light oil and in calm water the TE value averaged 80% at 0.5
m/s and decreased to 46% at 1.25 m/s. Testing was not continued beyond
this tow speed, as the trend was clearly established. The 0.3 m and 0.6
m harbor chop wave conditions had parallel trends. Also, the data
reveal greater variations of TE with light oil than with heavy. This is
due to the fact that light oils emulsify more readily in wave conditions.
Overall, lower performance with light oil was observed.
Oil pickup for all tests was conducted with the rotating absorbing
belt alone. Recovery Efficiency values are relatively constant over a
wide range of conditions. For heavy oil, Recovery Efficiency is about
80% for all speeds and wave conditions, decreasing with increasing speed
as more oil becomes emulsified due to turbulence. RE values for light
oil are about 60% for all speeds and wave conditions and show the same
general downward trend as for heavy oil. Figures 24, 25, and 26 follow
to depict, graphically, the above-mentioned results, and Tables 25 and
26 contain those data points derived from selected tests.
49
-------
e
§
H
O
h-l
PH
Pn
100
80
60
9 20
Calm
0.5
1.5 2
TOW SPEED, m/s
2.5
100
80
60
40
20
3.5
Figure 24. Throughput efficiency trends (heavy oil) - BENNETT
MARK 6E.
50
-------
100 r -|100
S 401- n.i ™ nr. --*X H40
80|- Lk. H80
U
u
* 60|- n U. H60
o
w
H -%v "Q
0.3 m *"*~
Q
o
20|- D-... 4^ °-6 m HC -|20
" -a
0.5 1 1.5 2 2.5
TOW SPEED, m/s
Figure 25. Throughput efficiency trends (light oil) -
BENNETT MARK 6E.
51
-------
100
e
I 60
0
H
W
40
Heavy Oil
.^-- Light Oil
n -a—-O---.Q...Q
Data Plotted for both Calm and
Wave Conditions
0.5
Figure 26.
1
1.5 2
TOW SPEED, m/s
100
60
40
20
2.5 3 3.5
Recovery efficiency trends - BENNETT MARK 6E.
52
-------
TABLE 25. TEST RESULTS - BENNETT MARK 6E (HEAVY OIL) AVERAGE VISCOSITY; 3000 x 10-6m2/s
Ul
to
Test
no.
7
7A
8
8A
SB
9C
10
10A
11
11A
12
L2A
13
13A
14A
14B
15
16
16A
17C
17D
18
18A
18B
18C
18D
18E
Tow
speed
m/s
0.5
0.5
1.0
1.0
1.0
1.25
1.5
1.5
1.75
1.75
2.0
2.0
2.25
2.25
2.5
2.5
2.75
3.0
3.0
0.5
0.5
1.0
1.0
1.0
1.09
1.0
1.0
TEST CONDITIONS
Oil diat. Slick
rate thick. Waves
(m3/s)xlO~3 mm m x m
1.86
1.85
3.75
3.77
3.86
4.67
5.59
5.38
6.46
6.71
7.16
7.58
8.38
8.46
10.8
9.0
10.01
11.69
11.01
2.08
1.93
3.85
3.56
3.65
3.27
3.68
3.61
3.0
3.0
3.0
3.1
3.1
3.0
3.0
2.9
3.0
3.1
2.9
3.1
3.0
3.0
3.3
2.9
3.0
3.2
3.0
3.4
3.1
3.1
2.9
3.0
2.7
3.0
2.9
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.18x7.9
0.18x7.9
0.18x7.9
0.18x7.9
0.18x7.9
0.18x7.9
0.18x7.9
0.18x7.9
Enc.
%
100
100
100
100
100
90
97
98
98
100
90
96
96
96
95
96
100
100
100
98
100
98
98
95
95
95
95
Door
setting
Bow Mid
1.04
1.09
1.09
1.09
1.09
0.99
0.94
0.97
0.94
0.91
0.86
0.81
0.81
0.84
0.84
0.84
0.83
0.83
0.83
1.06
1.06
1.06
1.06
0.99
ND
0.99
1.17
0.47
0.50
0.40
ND
0.38
0.35
0.16
0.24
0.25
0.28
0.23
0.23
0.30
0.28
0
0.05
0.05
0.10
0.10
0.41
0.41
0.41
0.41
0.43
0.30
0
0
Aft
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.13
0.27
0.27
TEST RESULTS
Rec . Thru
eff. eff.
% %
83
86
82
83
66
58
86
74
76
75
81
80
76
75
70
81
80
76
66
83
80
77
82
75
80
80
80
85
106
103
73
73
78
98
92
83
92
81
65
81
58
59
66
50
43
14
100
103
34
39
30
51
55
57
Oil rec.
rate
(m3/s)xlQ-3
1.6
2.0
3.8
3.9
2.8
3.2
5.2
5.7
5.2
6.1
5.2
4.6
6.4
4.6
5.6
5.6
5.0
5.0
1.5
2.0
2.0
1.2
1.3
1.0
1.6
1.9
1.9
(Continued)
-------
TEST CONDITIONS
Test
no.
19
19A
20A
20B
21A
21B
21C
21D
22
22A
23
24
25
27
28
29
30
31
31A
Tow
speed
m/s
0.75
0.75
0.5
0.5
0.75
0.75
0.75
0.75
1.0
1.0
1.25
1.5
1.75
0.75
1.0
1.25
1.5
1.0
1.0
Oil dist.
rate
(m3/s)xlO-3
2.83
2.86
1.78
1.88
2.77
2.80
2.80
2.80
3.60
3.81
4.87
5.65
6.46
2.83
3.74
4.66
5.89
13.04
14.28
Slick
thick.
"l^iii
3.1
3.1
2.9
3.0
3.0
3.0
3.0
3.0
2.9
3.1
3.2
3.1
3.0
3.1
3.0
3.0
3.2
10.6
11.6
Door
Waves
m x m
0.18x7.9
0.18x7.9
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.6HC
0.6HC
0.6HC
0.6HC
0
0
Enc.
%
95
95
98
98
100
100
100
100
100
100
100
100
100
95
98
100
100
100
100
setting
Bow
1.06
1.06
0.99
1.02
1.02
1.02
1.02
1.02
1.02
0.99
1.02
1.02
1.02
1.07
1.07
1.07
1.07
1.04
0.99
Mid
0
0
0.50
0.50
0.50
0.60
0
0
0
0
0
0
0
0
0
0
0
0.30
0
Aft
0.27
0.27
0.06
0.06
0.27
0.06
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.06
0.27
TEST RESULTS
Rec.
eff .
%
81
82
88
87
84
86
86
84
83
86
82
79
76
76
76
75
76
80
83
Thru
eff.
%
67
65
89
88
67
59
95
75
81
72
84
57
42
50
53
49
51
43
76
Oil rec.
rate
(m3/s)xlO-3
1.8
1.7
1.6
1.6
1.9
1.6
2.6
2.1
2.9
2.7
3.1
3.2
2.7
1.3
1.9
2.2
2.9
5.6
8.0
-------
TABLE 26. TEST RESULTS - BENNETT MARK 6E (LIGHT OIL) AVERAGE VISCOSITY: 32 x lQ-6m2/s
Ui
Test
no.
40A
45
41
41A
41B
42
43
43A
43B
44
50A
SOB
51
51A
51C
52
52A
52B
53
53A
60
60A
61
61A
61B
70
70A
71
71A
72
72A
Tow
speed
m/s
0.5
0.5
1.0
1.0
1.0
1.5
0.75
0.75
0.75
1.0
0.5
0.5
0.75
0.75
0.75
1.0
1.0
1.0
1.25
1.25
0.50
0.50
0.75
0.75
0.75
0.75
0.75
1.0
1.0
0.50
0.50
TEST CONDITIONS
Oil dlst. Slick
rate thick. Waves
(m3/s)xlO~3 mm m x m
1.91
1.89
3.82
3.73
3.84
5.72
3.36
2.99
2.80
3.69
1.75
2.31
2.83
3.14
2.77
4.08
4.27
4.15
4.24
4.77
1.80
1.76
2.86
3.18
2.89
2.80
2.95
3.77
4.36
4.06
1.80
3.1
3.1
3.1
3.0
3.1
3.1
3.6
3.2
3.0
3.0
2.9
3.7
3.1
3.4
3.0
3.3
3.5
3.4
2.8
3.1
2.9
2.9
3.1
3.4
3.1
3.0
3.2
3.1
3.5
6.5
2.9
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.6HC
0.6HC
0.6HC
0.6HC
1.6HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
0.3HC
Enc.
%
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
Door
setting
Bow Mid
0.97
0.91
0.99
0.97
0.97
0.97
0.97
1.09
0.97
1.09
0.97
0.97
0.97
0.97
0.97
0.91
0.91
0.94
0.93
0.91
1.09
1.04
1.52
1.07
1.07
1.02
1.02
1.02
1.02
1.02
1.02
0.36
0.36
0.36
0
0.25
0.15
0.25
0.25
0.25
1.15
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.05
0.05
ND
Aft
0.06
0.08
0.06
0.27
0.15
0.27
0.27
0.27
0.27
1.27
0.27
0.27
0.27
0.14
0.15
0.14
0.05
0.05
0.03
0.03
0.08
0.16
0.27
0.27
0.27
0.27
0.27
0.15
0.15
0.27
0.27
TEST RESULTS
Rec . Thru
eff. eff.
% %
59
68
52
55
57
52
60
57
55
50
55
71
60
51
58
64
59
63
68
60
43
30
40
50
52
55
60
55
40
58
51
76
88
43
53
41
27
76
65
73
39
59
81
90
67
71
63
43
65
54
37
26
17
12
20
27
41
48
39
38
59
59
Oil rec.
rate
(m3/s)xlO~3
1.5
1.6
1.6
1.9
1.6
2.0
2.6
1.9
1.9
1.4
1.4
1.9
2.6
2.1
1.9
2.6
1.8
2.7
2.2
1.7
0.4
0.3
0.3
0.6
0.7
1.1
1.4
1.4
1.6
2.4
1.1
-------
Discussion
It was noted that the rotating absorbent belt performed best when
near the water surface. The belt did not function well if it pushed the
oil much below the water surface, causing oil and water to mix.
In operating the device, the major difficulty was with the bow and
gill door settings. The adjustment of these openings was found to be
critical to performance and a number of runs were spent determining
their best settings.
Bow ramp depth determines the thickness of the oil/water cut when
first entering the device. The depth must be set for each speed and
wave condition. At speeds near 0.5 m/s, it was necessary to have a
water cut of about 15 cm so that enough flow of water through the device
could be induced to push the oil against the absorbent belt. At higher
speeds, it was necessary to set this cut from 2.5 to 5 cm, adjusting the
height as speed increased. In waves, it was necessary to ensure that
the lowest trough of the wave flowed over the bow door.
The middle gill door is directly beneath the rear of the absorbent
belt. If there is too much water flow through the skimmer, oil tends to
be sucked through this door and out the bottom of the device. During
calm water tests with heavy oil, an abrupt flow change within the
skimmer was noted at 1.5 m/s. With the large middle gill door opening
necessary for a slower tow speed, oil was being carried out of this gill
door and lost. Performance improved only after the middle gill door was
nearly closed.
Heavy oil tests in calm water were conducted with the bow trash
grate in place. For heavy oil tests in waves, however, the trash grate
caused oil emulsification in initial runs, and subsequent data runs were
conducted without the grate. In both calm and wave conditions with
light oil, the trash grate caused a great amount of oil emulsification,
so the trash grate was removed for all light oil tests.
Major mechanical problems concerned the squeeze belt and scraper
blade assemblies. Contact pressure between the open-mesh squeeze belt
and absorbent belt was not sufficient to force oil through the mesh and
into the collection sump. Additionally, the scraper blade, as originally
installed, did not effectively wipe the squeeze belt of collected oil.
Both assemblies worked better with heavy oil because of its tendency to
form a thicker layer on the absorbent belt.
The following modifications were performed to achieve the best
skimmer performance:
(1) Change squeeze belt to thinner material for light oil tests to
eliminate oil trapped in thick weave of original belt.
(2) Install a squeegee over the scraper bar for light oil tests.
56
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(3) Graduate bow ramp and gill door control rods to allow repro-
ducible settings.
No other mechanical problems were of significance. The diesel
prime mover, hydraulic pumps and motors were operated without incident
throughout the two week test period. The polyester wool rotating col-
lection belt showed no significant wear after the two weeks of testing.
Figure 27 shows the scraper blade detail.
Figure 27. Scraper blade detail - BENNETT MARK 6E (squeeze) belt.
57
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APPENDIX A
OHMSETT TEST FACILITY
Figure A-l. OHMSETT test facility.
GENERAL
The U.S. Environmental Protection Agency is operating an Oil and
Hazardous Materials Simulated Environmental Test Tank (OHMSETT) located
in Leonardo, New Jersey (Figure A-l). This facility provides an environ-
mentally safe place to conduct testing and development of devices and
techniques for the control of oil and hazardous material spills.
The primary feature of the facility is a pile-supported, concrete
tank with a water surface which is 203 metres long by 20 metres wide
and which has a water depth of 2.4 metres. The tank can be filled with
fresh or salt water. The tank is spanned by a bridge capable of exerting
a force of up to 151 kilonewtons and towing floating equipment at speeds
of up to 3 metres/second for at least 45 seconds. Slower speeds yield
longer test runs. The towing bridge is equipped to lay oil or hazardous
58
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materials on the surface of the water several metres ahead of the device
being tested, so that reproducible thicknesses and widths of the test
fluids can be achieved with minimum interference by wind.
The principal systems of the tank include a wave generator, beach,
and a filter system. The wave generator and absorber beach have cap-
abilities of producing regular waves of up to 0.7 metre in height and
28.0 metres in length, as well as a series of high (up to 1.2 metres),
reflecting, complex waves meant to simulate the water surface of a
harbor or sea. The tank water is clarified by recirculation through a
0.13 cubic metre/second diatomaceous earth filter system in order to
permit full use of a sophisticated underwater photography and video
imagery system, and to remove the hydrocarbons that enter the tank water
as a result of testing. The towing bridge has a built-in skimming board
which can move oil onto the North end of the tank for cleanup and recycling.
When the tank must be emptied for maintenance purposes, the entire
water volume of 9842 cubic metres is filtered and treated until it meets
all applicable State and Federal water quality standards before being
discharged. Additional specialized treatment may be used whenever
hazardous materials are used for tests. One such device is a trailer-
mounted carbon treatment unit for removing organic materials from the
water.
Testing at the facility is served from a 650 square metres building
adjacent to the tank. This building houses offices, a quality control
laboratory (which is very important since test fluids and tank water are
both recycled), a small machine shop, and an equipment preparation area.
This government-owned, contractor-operated facility is available
for testing purposes on a cost-reimbursable basis. The operating con-
tractor, Mason & Hanger-Silas Mason Co., Inc., provides a permanent
staff of fourteen multi-disciplinary personnel. The U.S. Environmental
Protection Agency provides expertise in the areas of spill control tech-
nology and overall project direction.
For additional information, contact: John S. Farlow, OHMSETT
Project Officer, U.S. Environmental Protection Agency, Research and
Development, lERL-Ci, Edison, New Jersey 08817, 201-321-6631.
SPECIAL EQUIPMENT
During the 8 week OHMSETT Interagency Test Committee (OITC) test
program, some equipment changes were made to increase the ease and
quality of data collection. Although these changes were the results of
working with the four oil skimmers tested during the OITC 1977 season,
it is felt they could be of use in future OHMSETT test programs. The
modifications are:
(1) Use of tape recorders by the Project and Test Engineers.
(2) Use of a stadium-type lighted stopclock on control tower.
59
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Small portable tape recorders were very useful in capturing detailed
performance information and Impressions of the Test Engineer and the
OITC Project Engineer during the course of individual test runs. When
transcribed, this record was invaluable for explaining data differences
between runs and in documenting key behavior patterns of, the skimmer
under test. This method of data recording was especially useful during
rainy weather when keeping accurate hand-written notes would have been
difficult. A system of remote microphones all hard-wired to a central
tape recorder was found to be impractical as the engineers using these
recorders had to move about more than cord restraints would allow.
A labor saving of one technician was possible during the Cyclonet
050 tests following the installation of a large, stadium-type lighted
stopclock mounted on a control tower. This stopclock is visible from
the skimmer and all portions of the tow and auxiliary bridges and was
used to coordinate a number of different events such as oil slick dis-
tribution, pump activation aboard the skimmer, and the beginning of
sample taking aboard the skimmer. The number and conditions of the next
test run could be quickly displayed so that all OHMSETT technicians
could begin at once to change tow speed, wave, and oil distribution
settings as needed.
60
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APPENDIX B
SAMPLING PROCEDURES
Discrete sampling, that is, continuous sampling from a small dis-
charge port at the outlet of the skimmer pump at various time intervals,
was utilized to determine the presence of steady state in the operation
of the skimmers. Although discrete samples provide the level of detail
necessary to determine steady state operation, the collection and anal-
ysis of the many samples required extensive lab time. Due to the ex-
tensive experience during this test program with Discrete versus Com-
posite (standard OHMSETT) sampling procedures, the following general
conclusions can be drawn:
(1) Discrete samples are necessary for the first series of runs
for each test oil to determine the transient response time of
the skimmer before steady state operation is established.
(2) For transient periods on the order of 1/5 of the total test
time, the Composite sample, taken once at the end of the run
from the total oil/water mixture collected during the run, is
of sufficient accuracy and Discrete sampling is not required.
(3) A method of Composite sampling which appears to require less
time to perform than the current OHMSETT standard procedure and
should be considered for future OHMSETT programs, is termed
the Small Volume Composite sample. In this procedure, a
continuous, single sample is obtained for each test run by
slowly bleeding the oil/water mixture from the pump discharge
into a sample bottle. This smaller sample, about 2 litre
size, can be more easily analyzed than the larger 1.89 m3
barrels which are difficult to emulsify uniformly and, for
light test oil, may settle out quickly after being agitated,
thus making the obtaining of a representative grab sample
difficult.
(A) Selection of one of the above three sampling procedures for a
given skimmer can only be made after comparing the results of
all three during initial shakedown runs. In the order of
decreasing desirability, the sampling procedures are (maxi-
mizing the number of data runs):
—Small Volume Composite, (1) above
—Composite, (2) above
—Discrete, (3) above
61
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Data presented in this report are derived from the careful analysis
of both discrete and composite samples. The intent was to present the
the overall trends of device performance as they were observed and
measured at OHMSETT. As an example, in the case of the Oil Mop ZRV, the
highest RE from discrete or composite samples was utilized if, and only
if, they agreed by at least 10%. Otherwise, the composite sample was
felt to be more respresentative and therefore included in the data set.
Subsequent calculations of TE and ORR were based on the results of the
above conditional statement. Figure B-l represents the comparison of
Discrete and Composite sample results.
62
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100
90
80
.J
M
O
^^
B
sa
w
M
M
ta
O
CJ
Test No. 35A
Qdiscrete sampling (% oil vs. time)
/^fluid collected vs. time <
Dtotal fluid collected
composite recovery eff. = 45.6%
discrete recovery eff. = 49.5% ""
D
200
180
160
1AO
w
120 §
-j
o
u
100 co
z
o
80 g
60
40
20
25
50
150
Figure B-l.
75 100
PUMPING TIME (seconds)
Skimmer comparison of DISCRETE and COMPOSITE oil/water sampling OIL MOP ZRV.
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APPENDIX C
Differences in the physical properties of the same type oil as
indicated in Table C-l below are the result of:
(1) temperature variation
(2) contamination and reprocessing
TABLE C-l. RANGE OF TEST OIL PROPERTIES FOR THE 1Q77 OTTP
-------
These four programs were conducted separately at OHMSETT during the
1977 test season. As a result, tank water temperature was different for each
test series. Since it is felt that the oil temperature as it is encountered
by a device is the same as water temperature, significant oil property
differences result.
Oil property variations as a result of mixing contamination and re-
processing have been documented previously at OHMSETT. Performing a
100% purge of the main bridge oil storage, transfer, and distribution
system while transferring oils during a given test program is prohibited
by time and cost limitations. This results in the mixing of slight but
significant amounts of oils and thus variations in measured properties.
Additionally, the reprocessing of test oils by vacuum distillation
contributes to specific property changes. These effects are currently
being investigated at OHMSETT.
Laboratory methods are continually evaluated via the control chart
method as presented by the American Society for Testing and Materials,
Committee E-ll. Statements on precision and accuracy are available at
OHMSETT.
65
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APPENDIX D
SKIMMER BROCHURES
OIL MOP INC
DYNAMIC SKIMMER
PAT. PENDING
T'. <
RECOVERY RATE
RECOVERY SPEED
STORAGE CAPACITY
PUMPING CAPACITY
TRAVEL SPEED
.LENGTH
WIDTH
SHIPPING WEIGHT
250 BBL/HR
6 KNOTS
2400 GAL. 9.080L
400 BBL/HR
15 KNOTS
38' 2" 11.6M
12* 2" 3 7M
20,000 LB. 9-.072KG
66
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CYCLONET 050
aapantion naturvtlo par cycIOKMQ
natural ••pantton fey cyclona action
technical particular*
The unit :
Body width
Length . . . .
Height . .
Average draught
Weight
0 50 m
1 50 m
100 m
085 m
80 kg (approx.)
Operating speed 05-5 knots
Power input for two units 8 h p at 5 knots
ZODIAC Inflatable Boat
1
3
^i^'
-------
CLOWSOR
Length
Width
Height
2.3 m
3.03 m
1.2 m
68
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u-r*:nr POLLUTION CONTROLS LTD.
'' UJ r; *, i.-. ;r>—r. mrni
«•"»•
I BENNETT
6t
'—•--.» SK-Cl-OI-OJ*
BENNETT MARK 6 E OIL SKIMMER.
Langth (overall)
Length (watorlint)
B*am (moulded)
Depth (moulded)
Displacement (loaded)
Freeboard (loaded)
Freeboard (Ught)
Net tonnage (tans of 100 ft3 )
Free swept width
between hulls
Shipping Weight.
37ft. Oin.
37ft. Oin.
13ft. Tin.
4ft. Oin.
22.7 tons
181ns.
7.35
4 ft. 65n«.
4ft. Oms.
29,500 IU.
11.3 m
11.3 m
4.1m
1.22m.
23.1 tonnes
13,380 kilogrammes.
69
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«MJ
I
TECHNICAL Rf KMT DATA
mout am Ott rrnn* foh
EPA-600/2-78-204
4 filvt A*»L> ftuCI ill I
Performance Teat* of Four Selected Oil Spill Skimmers
Robert U. Urban, Douglas J. Graham and Sol H. Schwartz
Mason & Hanger-Silas Maaon Co., Inc.
P. O. Box 117
Leonardo, New Jersey 07737
AO« Nt » toAMt AMU AOOIlif*~
Industrial Environments! Research Laboratory-do.. OB
Office of Reaearch aod Development
U.S. Environmental Protection Agency
Cincinnati. Ohio 45268
ACCt**iO*»NO.
ft Mf »OMT DATf
* tM»0*MUK»OM&AMl*AttOMCODf
ONOAJWI2ATION Kg POM T NO
»* moolujM f UMCMT l«dT
1BB61G
ii eauriugfwutjv wv
68-03-0490
i f w« or ftcronr AMD ^f moo covi Nto
Final
COO*
'fNfcO I
—
ETA/600/12
Aaaoclatea. Corca Madera, California 94925
with Pollution Abatement
A aeriea of performance teata were conducted at the 0.S. Environmental
Protection Agency'. OI«SETT teat facility with four .«lact«l oil .pill pickup devices
(aki^era). Each of the four skteara waa t«wd for two w^k. wiu, both high and
low viacoaity oils, v
the objactlvea of the teata were to eatahliah the rang* of bast performance for
aach aklM«r undar the manufacturer 'a daaign limlta and to document teat raaulta on
16mm film and by quantitative meaaurea of performance.
A,, e °U •""•*'* «t«***l «>y the OtttSETT Intaraganey t»at Committea ware: 1)
Oil Mop Skimmer - A catamaran vassal dealgned primarily for oil aklmmlnt at spaads
•Jf* J'* •/i; 2> Cyclonat 050 - A davica aMacad on an inflaubla host daslgnad for
oil skiamMng in relatively calm water. 3) Clovaor Skimmer - A unit designed primtrily
for rscovsring oil at v«ry high rataa whila held stationary in calm watarTA) Bennett
M*A,M - A •emi-catamaran vassal designed for skimming oil at spaads up to 1.5 ,/s.
A total of 198 individual data taat runs wars aada during the course of the
8-week teat program. Bach skimmer was tasted to the li«it of Its design conditions
and beyond.
WOMOS **O OOCUMCMT
Performance teats
Skimmers
Uater pollution
Oils
b.lOCHTir*C
ion
6. COSATt
Spilled oil cleanup
Protected watera
Coastal waters
680
RELEASE TO PUBLIC
ASSIFTED
82
DRCLsSSiniD
•M turn M«*f
70
•«*•
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