vc/EPA
United States
Environmental Protection
Agency
Municipal Environmental Resear
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81 -229 Dec. 1981
Project Summary
Performance Testing of the
DiPerna Sweeper
Michael K. Breslin
The DiPerna Sweeper, a partial-
vacuum oil skimmer, was tested in a 2-
week test program conducted at the
U.S. Environmental Protection Agen-
cy's Oil and Hazardous Materials
Simulated Environmental Test Tank
(OHMSETT) in Leonardo, New Jersey.
Forty-three oil recovery tests were
run. The object of the program was to
establish a range of best performance
for the skimmer under various en-
vironmental conditions in light and
heavy oils.
The DiPerna Sweeper is a self-
contained, floating oil skimmer that
can operate in either a stationary or
advancing mode. Its principle of
operation is based upon drawing oil
and water into a sealed container by
creating a slight vacuum in the
container. A floating weir serves as
the inlet. The partial vacuum is created
by pumping fluid from the sealed
container. The container serves as an
oil/water separator. Separate pumps
draw water from the bottom of the
vessel while others draw oil from the
top.
The device was able to recover over
75% of the oil presented to it in calm
water at tow speeds up to 2 kts.
Performance decreased in waves.
Modifications are suggested to im-
prove such performance. The separator
functioned well. In one case, the oil
offloaded from the skimmer was 95%
free of water.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory. Cincin-
nati, OH, to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The DiPerna Sweeper (Figure 1) was
designed by James DiPerna and built by
the Brewer Dry Dock Company,* both of
Staten Island, New York. In April 1979,
the skimmer, which can be transported
on a common-carrier, flatbed tractor
trailer, was moved from the shipyard to
OHMSETT. The original gravity flow
design was modified toa partial vacuum
design at OHMSETT under the direction
of Mr. DiPerna. The merits of the
conversion were demonstrated using a
small model built by Mr. DiPerna (Figure
2). The modifications did not affect the
basic nonmixing oil/water collection
principle. Other modifications suggested
by Mr. DiPerna regarding removing the
skimming head and altering the skimmer
to allow the fluid to flow over a weir
attached to the separator were not acted
upon at this time.
On 14 May, the skimmer was lifted
into the test tank where 43 oil recovery
tests were run with light and heavy oils,
which are described in Appendix B of
the full report. On 25 May, the device
was removed from the tank. All per-
formance testing was conducted at
"Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
-------
Figure 1. The DiPerna Sweeper being lifted into the test tank.
OHMSETT by the operating contractor
Mason & Hanger-Silas Mason Co., with
the guidance of the U.S. EPA Project
Officer.
Device Description
The original design of the DiPerna
Sweeper consisted of a gravity-flow API
oil/water separator mounted between
two floatation chambers (Figure 2). A
segregated floating head with an
overflow weir, connected to the main
portion of the skimmer by a 20-cm
diameter hose, served as a fluid inlet
(Figure 3). Oil and water were drawn
into the skimmer over the weir by
lowering the water level inside the
device below the outside waterline. This
was accomplished by pumping water
from the bottom of the separator. Oil
collected in the first compartment was
routed to a rear compartment where it
was offloaded by a small pump. The
water was removed from the bottom of
the separator in the second compart-
ment. This design allowed the use of
less than half of the separator volume
since a good portion of the separator
extended above the mean waterline.
Modifications to seal the top of the
separator from the atmosphere and
reroute pump piping were carried out
while the skimmer awaited testing at
OHMSETT (Figure 4). The changes
permit the use of the entire volume of
the oil/water separator and simplify the
offloading of collected oil.
With the top of the separator sealed, a
partial vacuum is induced inside the
separator by pumping air out from the
top of the chamber. Fluid allowed over
the inlet weir fills the evacuated area.
Thus a flow of fluid over the weir can be
maintained even though the fluid level
inside the separator is above the
waterline. Water is still removed from
the lower rear of the separator, but the
oil outlets are relocated to ports welded
flush with the sealed deck. The design
utilizes the entire volume of the
oil/water separator with a minimum
increase in vessel draft.
The segregated floating head was not
modified from the original design. The
design and concept of a light, wave-
following skimming weir, which was
separate from the main body of the
skimmer, appeared sound and did not
warrant change. The head was detached
from the separator so it could follow
waves, maintaining the weir at the
desired depth. Swamping of the weir
and sump by waves would be avoided if
it performed as designed. The skimming
head had not been previously tested in
either a model or in full scale. Chambers
and valves are incorporated into the
head to permit ballasting with water.
The sweep width of the head is 1.2 m;
the width of the weir is 0.5m. Directly
behind the weir is a small sump that
leads to the large hose connecting the
head to the skimmer. Additional skim-
ming heads can be attached to the
skimmer with the use of small ports
welded to the fluid inlet pipe. Because
these heads can be used at a distance
from the skimmer, oil can be collected
from shallow areas or under piers while
the main skimmer sits in deeper water.
Fluid is drawn into the skimmer by
pumping water from the lower rear of
the separator. It enters the separator
chamber at the front directly beneath
the deck. Unmixed oil is delivered to the
top of the separator where it floats; the
water seeks the lower level. In this
manner, oil and water mixing is mini-
mized. The residence time of the oil and
water in the separator can be varied
depending on the offloading pumping
rate. The pumps used in the OHMSETT
tests had a combined flow rate of about
120 mVhr. Residence time (190 sec)
with all of the pumps operating appeared
more than adequate.
A small, sealed deck house with plexi-
glass windows was placed on the
skimmer with a pipe running from it
through the deck to the keel of the
separator. Water is drawn from the pipe
producing fluid flow up the pipe.
Windows allow the operator to see
when oil is being drawn up the pipe and
thus slow the water pump rate or to
offload oil.
The vessel had an overall length of
5.5m, a beam of 2.9m, a draft of 1.7m,
and a freeboard of 1m. The vessel
weighed about 3000 kg.
Results
The DiPerna Sweeper proved to be a
simple and effective design incorporating
only pumps for oil recovery. The
skimmer can be pushed, towed, or self-
propelled during its oil collection
operations. The force of the water from
the pump discharge off the rear of the
skimmer is enough to propel the device
forward at about 0.25 to 0.5 kt. Such a
forward speed may be suitable for tank
testing but would not be practical for
field use. The skimmer is chiefly
designed to be attached to oil booms
where winds and currents would drive
oil to the skimming head; it is not
intended for high-speed skimming. t
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Mast
Starboard
Flotation Chamber
Water Outlet
Oil Outlet
Skimming
Head
Oil/Water Separator
(in the keel only)
Oil Transfer Pipe
V~^"L---—
\1V-—-"^ Oil/Water
Oil/Water Inlet
Figure 2. Cutaway view of original DiPerna Sweeper design.
Weir (inlet)
Converging Sides
Sump
Connecting Hose
Flotation and Water
Ballast Chamber
Water (ballast) Outlet
Figure 3. Isometric view of the floating skimming head.
Water Outlets and Filling Ports
Mast
Skimming
Oil Outlet
New Welded Deck
Sealed Deck House
Water Outlets
Skimming
Head
.Figure 4. Cutaway view of the modified DiPerna Sweeper.
Floating Skimming Head
If the skimming head is to be retained,
a major redesign is necessary. The
shovel-nose design of the head caused
many problems in the presence of
waves. It acted as a damper to slow the
inlet weir's wave response; it produced
turbulence in the oil slick when it
heaved above the waterline; it provided
a spillway for the excess oil and water
that was washed up to the weir but
could not enter. As the oil and water ran
down the nose, it mixed vigorously and
pushed the oncoming oil slick away
from the head. The best solution
seemed to be a deeper weir cut in waves
so the shovel nose would never rise
high enough to cause problems. Under
tow in both calm water and waves, the
shovel nose acted as a diving plane
causing the weir to sink below the calm-
water setting and the head to pitch
forward. The nose also caused problems
with ballasting the skimming head. If
the ballast water drained to the rear
areas because of a rearward pitch of the
head, the nose became a forward
buoyancy chamber that maintained the
head in the tilted position. SCUBA diver
weights, guy wires, and a wire rope
cable to a winch on the mast provided
the ballast and kept the weir at the
desired calm water setting for the tests.
An unfortunate interference occurred,
however because of the use of the guy
ropes and the wire rope on the skimming
head. When a wave trough was en-
countered, the ropes restricted the
downward travel of the head causing a
sudden stop. This prevented the weir
from maintaining a constant depth and
allowed water and oil to flow down off
the nose onto the approaching oil slick.
Without the ropes, however, the move-
ments of the skimming head from side
to side and pitching forward would have
made oil collection much more difficult.
The removal of the shovel nose from the
skimming head and judicious placement
of floatation and ballast should solve
most of the above problems. A feature
the skimming head lacks is a vertical
plate to prevent waves from splashing
over the head and, thus, losing oil.
Finally, the weir tended to raise up
above the waterline when the fluid in
the head sump was pumped out and
thus restricted flow over the weir.
However, if the sump did not drain
somewhat in between waves, the next
wave would swamp the sump and oil
would be washed away from the weir. A
self-compensating weir lip or inlet valve
-------
could be built into the skimming head to
prevent such starving of fluid flow.
Oh'/Water Inlet Hose
The hose used in the tests was too
heavy and too stiff to allow the skimming
head to act independently of the main
body of the skimmer. If the skimmer
operator changed his location on the
deck of the vessel, the slight tilt of the
vessel would twist the hose and alter
the attitude of the skimming head. The
floatation of the skimming head is not
enough to freely move the inlet hose in
response to oncoming waves.
Oil/Water Separator
Converting the separator from gravity
flow to partial vacuum made the
additional separator volume available
above the waterline. This accounted for
64% of the 6.3 m3 total separator
volume. Oil/water separation had to be
enhanced by this change since the fluid
residence time increased along with the
volume. Only during wave tests using
low viscosity oil did any oil reach the
water discharge pump inlet, and then it
was very little. This means that the
water discharge capacity could be
increased beyond that used in these
tests without significantly affecting
performance of the separator. Onboard
storage capacity of collected oil was also
increased by the modification. The
changes also provided oil offloading
ports on the deck that could be drawn
from during a test to increase the mass
flow rate through the skimmer. This was
done by additional pumps placed on the
skimmer.
Nonturbulent collection of oil and
water was virtually unchanged by
converting to a partial vacuum skimmer.
The inlet pipe was extended to within
150 mm of the new decking to deliver
the oil to the top of the collected fluid.
This prevented the oil from having to
rise up through the fluid inside the
separator and perhaps be swept away
with the water under the baffles to the
water discharge pump inlet.
The vessel was stable and had a slow
wave response because of the water-
filled keel and the catamaran-like
arrangement of the floatation chambers
on both sides of the vessel.
Sealed Deck House
Purpose of the deck house was to
determine when oil reached the inlet of
the water discharge pipe located
100mm above the keel of the separator.
This would be an indication that the
vessel was either full of oil or that the
water had been removed from beneath
the oil and oil would be offloaded next.
Since oil was offloaded from the ports
welded flush with the deck and logistics
prevented tests with enough oil to fill
the skimmer, the deck house was not
put to its designed use. It did, however,
provide an excellent view of the amount
of oil mixed with the water at the bottom
of the skimmer. It also provided an
additional port from which water could
be drawn to increase the mass flow rate
through the skimmer.
Oil and Water Offloading
Pumps
The gasoline-driven pumps that
arrived with the skimmer consisted of a
diaphragm pump (7m3/hr) for oil
offloading and a centrifugal pump
(70m3/hr) for water discharge. Both
pumps performed well until carburetor
trouble forced the diaphragm pump out
of service. With the increase in usable
separator volume, the pump capacity
could be increased without fear of
drawing the collected oil out with the
water. It was evident that an increase in
mass flow rate over the weir could
diminish the turbulence generated by
the headwave and thus increase the
skimmer's performance at higher tow
speeds. To accomplish this, an air-
driven double-diaphragm pump (32
mVhr) was placed onboard to offload oil
from an exit port on deck and a gasoline
centrifugal pump (16 mVhr) was placed
onboard to discharge water drawn up
into the sealed deck house. The resulting
increase in mass flow rate produced an
increase in performance in both calm
water and in waves. The general
absence of oil exiting with the discharged
water would indicate the pump rate
could be increased to about 225 mVhr
without deleterious effects. This would
give a fluid residence time of about 100
sec in the separator. Since the oil enters
the separator only loosely mixed with
the water, there should be enough time
for the oil to stabilize at the top of the
separator and not be drawn out with the
discharged water.
Data Discussion
Recovery Efficiency (RE) was not
recorded for each test because, less
than halfway through the program, the
oil was offloaded during the test rather
than following it. During the test,
offloading drew an uncontrollable
amount of water with the oil; this
lowered the RE of the device. Under
such circumstances, comparing the
RE's would not render useful con-
clusions as to the causes. The quantities
of oil offloaded into the barrels gave
representative values of RE if the barrel
was not drained of much water before
the sample was taken. This was the
case in several tests in which the
procedure was to offload the oil after
completion of the test run. The values
obtained were 86% for 0.5 kt, 91% for
0.75 kt, 91 % for 1.0 kt, 89% for 1.25 kt,
88% for 1.5 kt, and 87% for 2.0kt. These
values should be considered below the
capability of the skimmer since the
amount of oil in the one full barrel
represented 70% of the oil collected by
the skimmer. As the oil was drawn from
the skimmer, the oil layer inside
decreased to where water was drawn
out with the oil. This lowered the
percentage of oil in the outlet stream
and subsequently that in the barrel also.
There was not enough time in the test
program to optimize device settings for
every condition tested so the test results
should not be considered the best
performance possible by the skimmer.
When time allowed, device settings
were changed and tests were run under
the same tank conditions.
To w Speed
Increasing tow speed raised a head
wave in front of the floating head and
created turbulence by forcing more
water to be channeled from the sweep
width of the head (1.2 m) into the width
of the weir (0.5 m). The tow speed at
which performance would begin to
decline should be predictable by com-
paring the flow over a rectangular weir
(1.2 m wide) at different water depths
over the weir to the tow speeds and
pumping capacity of the skimmer. With
the use of one pump, 70 m3/hr of water
could be discharged. A water depth of 4
cm is needed for a 70-m3/hr flow.
Bernoulli's equation predicts a 1.86-kt
tow speed will produce a headwave of
4.5 cm. A decline in throughput effi-
ciency (TE) and oil recovery rate (ORR)
perfomance occurred between 1.5 and
2 kt. With the use of four pumps (125
mVhr), the point of decline should be.
about 2.2 kt. The data for TE versus tow
speed in heavy oil and calm water show
-------
a significant decline in performance
above 2 kt using four pumps. Extrapo-
lation of these results suggest that a
greater pumping capacity would result
in better performance at higher tow
speeds. As long as the current inside the
skimmer is not large enough to entrain
and sweep a good deal of oi I to the water
discharge inlet, performance will in-
crease with pumping capacity.
Waves
TE and ORR werie greatly decreased
by the presence of waves. Below 0.75 kt
in harbor chop waves, the oil was
washed away from the skimming head
by the wave reflection. Above 1 kt, TE
performance declined to less than 50%
in the harbor chop. This was because of
the inability of the skimming head to
respond well to the waves, which
caused turbulence in front of the weir
and allowed waves to splash over the
head. ORR values leveled outand began
declining at 1 kt in the harbor chop as
pompared with 1.5 kt in calm water.
Regular waves reduced skimming
performance compared with that.in
harbor chop. The harbor chop condition
varied the water level at the weir at a
greater frequency than the regular
waves. The skimmer head heaved only
slightly during the harbor chop, but the
waves slapped into and overthe weir. In
regular waves, the skimming head
heaved a great deal and was often 180°
out of phase with the oncoming waves.
A great deal more turbulence was
generated in front of the weir and more
waves splashed over the skimming
head and degraded the performance. A
redesign of the skimming head and inlet
hose should increase performance in
waves at all tow speeds.
Oil Viscosity
Skimmer TE and ORR performance
was superior in the high viscostiy oil.
Driven by the turbulence created in
front of the weir, the low viscosity oil
tended to mix with the water and pass
beneath the skimming head. Although
the TE results were consistently lower
in the low viscosity oil, the general
trends in performance were very
similar. Low viscosity oil reached the
water discharge inlet during tests in
waves whereas the high viscosity oil did
not. The amount of oil discharged with
the water was insignificant, but it points
to a possible problem of discharging oil
|if the pumping capacity is increased.
Weir Depth
This variable was not investigated
completely since the skimming head
rose up in the water if the fluid in its
sump was lowered very much. Gen-
erally, the weir was kept at about 60 to
70 mm deep in calm water. In wave
tests, the weir depth varied a great deal
because of the poor wave response
capability of the skimming head. In
wave tests, skimmer performance
increased if the weir was set at a depth
of about 100 or 120 mm before the start
of the test. The lower setting further
submerged the shovel nose of the
skimming head and reduced its presence
above the water's surface where it
produced oil-entraining turbulence.
Slick Thickness
TE was not noticeably affected by the
changes in slick thickness; however,
ORR varied in direct proportion to the
changes.
Recovery efficiency samples indicate
the device is capable of consistently
high values of RE.
Conclusions
The DiPerna Sweeper proved effective
in recovering low and high viscosity oils
at tow speeds up to 2 kt (Tables 1 and 2).
Based on samples taken at the oil off-
loading pump outlet, the skimmer has
the capability of collecting oil with less
than 5% water. This is because the
method draws oil and water into the
skimmer without mixing them and off-
loads the oil from top of the collected
fluid and the water from the bottom.
Best performance of the skimmer
obtained during the 2-week test program
is listed below (TE in percent; and ORR
in mVhr). RE samples were not taken
on every test and do not appear in the
chart.
Discrete samples taken at the pump
outlet resulted in RE values of 95.5% at
1 kt in calm water and 88% at 0.5 kt in
the 0.3-m harbor chop.
The skimmer performed best in high
viscosity oil in calm water. Waves
caused drastic reductions in perform-
ance, and regular-wave, head seas
resulted in the poorest performance.
The greater the number of pumps
removing fluid from the skimmer, the
better the device performed. Primary
objective to improve performance was
to get as much of the oil slick into the
device as possible and not worry
whether some oil was discharged out
the stern with the water.
The shovel-nose design of the skim-
ming head and its attachment to the
main body of the device via a large stiff
hose was not conducive to optimum
wave following. Overall performance in
waves could be substantially improved
with the proper skimming head and inlet
hose.
The main portion of the skimmer was
stable and generally unresponsive to
waves. This was due to the deep, water-
filled keel and the floatation chambers
on both sides of the vessel.
Recommendations
A redesign of the skimming head and
in ret hose should be undertaken to
improve wave response of the hose and
head system, to improve the skimming
head water ballasting system, to prevent
wave splashover response and to
prevent turbulence and headwave
production while under tow in calm
water and in waves.
The main portion of the skimmer
should be outfitted with larger pumps
than those tested. A pump with a
capacity of about 200 m /hr should be
used to remove the water from the
bottom of the vessel, while a 50 mVhr
positive displacement pump should be
0.5 kt
1.0 kt
1.5 kt
2.0 kt
2.5 kt
TE ORR* TE ORR TE ORR TE ORR TE ORR
Calm water
0.3m harbor chop
0.3m reg. wave
95.0 12.7+ 96.2 26.3" 95.1 38.0* 75.3 40.2 33.2 22.1
44.1 5.3 72.8 19.4 46.4 18.5 27.3 14.6 ND ND
ND ND 38.310.0-23.5 9.4 21.1 11.321.0 14.0
*ORR values are corrected to 12-mm-thick oil slicks by multiplying the measured
ORR by 12 mm and dividing by the actual slick thickness.
*0ne water discharge pump (70 m3/hrj was used. All other tests used four pumps
(125 rrf/hr total).
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Table 1 . Test Results of the DiPerna Sweeper
Tow Slick
Test Speed Waves Thick
No. (knots) (m x m) (mm)
SD3 0,5
1 0.5
2 0.5
3 0.75
4 0.75
5 1.0
6 1.0
7 1.0
8 1.25
9 1.25
10 1.50
11 0.5
12 1.25
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
0.3 mHC
Calm
11.7
12.4
12.4
13.2
13.4
12.9
12.8
12.8
12.9
10.4
9.4
11.9
10.1
in High Viscosity Oil
Weir
Depth TE
(cm) (%)
6.35
6.35
6.35
6.35
6.35
6.35
7.62
6.35
6.35
6.35
6.35
varied
7.62
95.0
91.3
93.7
91.8
95.0
94.5
84.3
96.2
97.2
95.1
95.1
25.7
93.8
ORR
(m3/hr)
12.4
12.6
12.9
20.1
20.8
27.2
24.1
27.4
28.1
27.5
29.8
3.4
26.5
Comments
140 kg ballast on vessel, wts and ropes
on head
Good test
No losses seen in underwater film footage
Ballast on skimmer raised to 340 kg
Good test, water discharge clean of oil
Small losses less than 1% at boom
attachment points
Oil not hosed in at the end of the test.
95% RE at oil/ water outlet
Good test
Oil shedding seen from the front
Same as test No. 8
Good test
Wave reflection down nose of skimming
head washed oil away, 88% RE at oil/
water outlet
Good test
13
1.5
Calm
12.6
14
15
16
17
18
19*
2.0
2.0
2.5
0.5
2.0
2.0
Calm
Calm
Calm
0.3 mHC
Calm
Calm
13.1
12.8
12.2
12.8
8.7
9.7
7.62
6.35
6.35
varied
6.35
10.16
46.9
55.9
23.4
30.7
34.3
30.2
27.4
31.8
15.9
4.4
13.3
13.1
7.62 87.4 36.5 A good deal of entrapment from the
skimming head
Entrainment much worse
Large oil losses seen due to shedding
Some oil escaped under the port boom
Main skimmer and head out of phase due
to waves, jerking action on head caused
oil losses
New pump on skimmer failed in middle
of test
Four pumps used - lowered weir to gain
flow
*Four pumps were used from this test on except for tests 24, 39, 40, 41, and 42.
20
21
22
23
24
25
26
27
28
29
30
2.0
2.0
2.0
0.5
0.75
0.75
1.0
1.5
2.5
2.0
0.5
Calm
Calm
Calm
12.4
12.1
0.3 mHC 12.0
0.3 mHC 11.7
0.3 mHC 12.0
0.3 mHC 12.0
0.3 mHC 12.5
Calm 12.2
0.3 mHC 11.8
0.4x1.1.6 —
— — — Aborted due to oil distribution pump
failure
11.43 75.3 41.6 Good test
11.43 69.5 37.3 Skimming head rising and falling as it
emptied and filled again
varied 44.1 5.3 Larger booms used to guide oil to the
skimmer
varied 45.2 8.9 One pump used to compare results
varied 80.7 16.2 Turbulence caused by skimming head
action, some oil reached the water dis-
charge inlet
varied 72.8 19.4 86% RE determined from grab sample
at oil/water outlet
varied 46.4 19.3 Skimmer head sump drained after each
wave, good test
12.7 33.2 22.5 Good test, vortices in front of head
caused losses
varied 27.3 14.4 Waves and oil splashed over skimming
head
— — — Aborted due to lack of oil entering
skimming head
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Table 1.
Test
No.
31
32
33
34
Table 2.
Test
No.
35
36
37
38
39
40
41
42
43
(Continued)
Tow
Speed
(knots)
1:0
1.5
2.0
2.5
Test Results
Tow
Speed
(knots)
0.5
0.5
1.0
1.0
1.5.
2.0
2.5
1.0
1.0
Waves
(m x m)
0.4x11.6
0.4x11.6
0.4x11.6
0.4x1 1.6
of the DiPerna
Waves
(m x m)
Calm
Calm
Calm
Calm
Calm
Calm
Calm
0.4x1 1.6
0.4x11.6
Slick
Thick
(mm)
12.6
12.5
12.5
12.6
Sweeper
Slick
Thick
(mm)
12.2
—
12.4
12.2
12.5
12.3
12.7
—
Weir
Depth
(cm)
varied
varied
varied
varied
in Low Viscosity
Weir
Depth
(cm)
70.2
—
10.2
10.2
12.7
11.4
varied
—
TE
(%)
38.3
23.5
21.1
21.0
Oil
TE
(%)
83.1
—
73.5
78.0
32.5
8.3
7.2
—
ORR
(m3/hr)
10.5
9.8
11.8
14.7
ORR
(m3/hr)
11.1
—
19.9
31.8
•
18.1
5.7
2.0
—
Comments
Waves reflected from head washed on-
coming oil slick away
Same as test No. 31
Air entered skimmer because the head
drained completely at times
Losses due to shedding more than splash-
over, water discharge clean of oil
Comments
Test aborted due to obstruction in water
jet nozzle which controlled the slick width
Water discharge lightly colored by oil
Aborted, water discharge pump ran
out of gas
Vortices formed at boom attachment
points, oil drawn underwater and lost
Smallest pump failed, three pumps in
service
Three pumps in service, only 5 or 6%
decrease in pumping rate of 4 pumps
Great deal of entrapment from skimming
head
Oil pushed away from head by reflection
waves
Aborted due to break in oil boom tie line
used for offloading oil and removing air
from the top of the skimmer.
The oil/water separator should be
enlarged. A longer residence time and a
more stable vessel would result if the
lower portion of the oil/water separation
compartment were extended beyond
the center to the port and starboard
sides to form a rectangular cross-
section.
The full report was submitted in
fulfillment of Contract No. 68-03-2642
by Mason & Hanger-Silas Mason Co.,
Inc., under the sponsorship of the U.S.
Environmental Protection Agency.
•ArU.S. GOVERNMENT PRINTING OFFICE:1981--559-092/3350
-------
Michael K. Breslin is with Mason and Hanger-Silas Mason Co.. Inc., Leonardo, NJ
07737.
Richard A. Griffiths is the EPA Project Officer (see belowj.
The complete report, entitled "Performance Testing of the DiPerna Sweeper,"
(Order No. PB 82-109 174; Cost: $6.50. subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Oil and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
I
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED
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