4>EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-154 Sept. 1981
Project Summary
Performance Testing of the
Soviet Oil/Debris Skimmer
H. W. Lichte
The oil skimming capability of a
specially modified Soviet oil/debris
skimmer was investigated at the U.S.
Environmental Protection Agency's
Oil and Hazardous Materials Simulated
Environmental Test Tank (OHMSETT)
in 1979. The self-propelled vessel is
17.7 m long and weighs 39 metric
tons. The 111 -kw diesel engine drives
a ducted propeller, water jet propulsion
system. The vessel is capable of 5
knots forward speed and skims effec-
tively at speeds of 0 to 1.0 m/sec.
The unique combination of various
weir designs into one system, vessel
mobility, the efficient use of energy, a
series-type of oil/water gravity sepa-
rator, and the propulsion techniques
all suggest that this model is an
effective harbor skimmer. The oil
recovery rate of 12.4 mVhr was
confirmed using high-viscosity test oil
(1.5 pascal seconds and 0.95 specific
gravity) in calm water conditions.
Recovery efficiency was 85 percent at
0.77 m/sec forward speed, and
throughput efficiency was 90 percent
at 0.51 m/sec forward speed. Per-
formance dropped when low-viscosity
oils were skimmed at faster speeds
and higher wave conditions. The
skimmer collected 64 percent of the
81.3-m3 oil volume encountered
during the test program.
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
Performanee evaluation of a Soviet oi I
skimmer was conducted at the U.S.
Environmental Protection Agency's Oil
and Hazardous Materials Simulated
Environmental Test Tank in 1979. The
program was sponsored through the
Joint U.S./U.S.S.R. Project on Preven-
tion and Cleanup of Pollution of the
Marine Environment from Shipping.
The test program was designed at
OHMSETT to evaluate the oil skimming
capability of a specially modified Soviet
skimmer. Model 2550/4, which was
provided by the Black Sea Central
Planning and Designing Bureau (Odes-
sa).
The Soviet oil/debris skimmer tested
at OHMSETT is a fourth generation
design for recovery of floating pollutants,
oil, and debris from the water surface.
The vessel can navigate offshore and in
the roads within limits established by
the U.S.S.R. Register of Shipping. The
maximum range is 18.53 km off port
with a sea force of 3 and wind force not
exceeding Soviet standards of 4.
The self-propelled vessel is 17.7 m
long, with a constructive water line
(CWL) beam of 4.3m and a total weight
of 39 metric tons. The CWL draft is 1.6
m, and the freeboard is 2.4 m. The 111-
kw diesel engine drives a ducted
propeller, water jet propulsion system.
The vessel is capable of 2.6 m/sec
forward speed and skims effectively at
speeds of 0 to 1.0 m/sec. Hydraulically
controlled bow doors provide an ad-
-------
justable oil slick sweep width up to 8 m.
Figure 1 shows the vessel at OHMSETT
with the bow doors wide open, and
Figure 2 illustrates the flow pattern
through the vessel.
The skimmer can be operated in both
an advancing and a stationary mode.
The speed and direction of the vessel is
controlled by reaction rudders down-
stream of the propeller duct. The unique
stationary mode requires the vessel to
maneuver its stern to a dock or piling
and close the reaction rudder. The
current then caused by the prop wash
pushes floating oil around either or both
side,s of the bow door opening and
subsequently sucks it into and over the
broad-crested weir.
The test was designed to simulate
harbor conditions typical of the
skimmer's design environment. The
U.S.S.R. designed the system both as a
stationary skimmer not requiring booms
and as an advancing skimmer usable at
forward speeds up to 1.0 m/sec and at a
maximum wave height of 1.5 m. The
OHMSETT test plan therefore included
three major phases: (1) investigation of
the fluid flow, (2) oil skimming in the
stationary mode, and (3) oil skimming in
the advancing mode. This skimmer was
the largest ever tested at OHMSETT,
had the deepest draft, and was the first
to require an active propulsion system
during testing.
High- and low-viscosity oil tests were
required to measure the pump and
oil/water separation efficiency. Because
the Soviets were interested in the new
modification incorporating the coke
filter, fluid flow experiments were also
needed.. Calm water and wave conditions
were selected to observe the effects of
splash in the broad-crested weir area
and the resonance of the vessel hull
reacting to wave length. Forward test
speeds were selected to observe bow/
wave interactions, vessel trim, and bow
door opening.
The skimmer had some new unproven
modifications. Each of these was
isolated in specific tests to determine its
contribution to performance.
Discussion of Results
Fluid Flow
Fluid flow measurements in the main
duct were of specific interest to the
Soviets. They provided the opportunity
to measure and confirm calculations in
a large test tank. Empirical calculations,
though straightforward in this applica-
Figure 1. Soviet skimmer as tested at OHMSETT.
tion, nevertheless depend on friction
factors, degree of laminar flow, geom-
etry, physical properties of the fluid,
propeller efficiency, and synergistic
factors difficult to measure. The results
imply a reasonably progressive increase
in flow at speeds of 0 to 1.0 m/sec.
Beginning with the experiments con-
ducted at 1.3 m/sec, the degree of
linearity becomes confusing. The ma-
nometer readings to measure the main
duct flow were steady in the calm water
tests, but they were erratic at high
speeds and wave conditions. Reading
error was more likely to occur because
of the pitch and roll of the vessel and
turbulence in the main duct. Variations
in the differences of the two columns
over several seconds was not uncommon.
The later stages of the low-viscosity oil
test series revealed clogging problems
with the Pitot tube. The direct-reading,
four-cone velometer in the vertical duct
was valuable in the early testing, but it
soon became apparent that the flow in
that area was not increasing as expected,
and the meter registered in the lower 10
percent of the scale. The stainless steel
cones were well protected, but bearings
and the electrical connections soon
became corroded from the salt water.
The test results indicate that the trii
of the oil collection box varied as a resu
of ballast, engine speed, and towspeei
The skimmer operator continuousl
attempted to keep the bow down and
10-cm skim depth over the broac
crested weir. If the bow sank too lov
the vessel would dive dangerously an
the bow doors would submerge corr
pletely. If the bow rose too high, th
vessel would rise and cause encountere
oil to flow under the weir into the mai
duct and be lost out the propeller tunne
The gate positions, though alwa\
recorded, were not changed ofte
during the test program. The broac
crested weir angle, a function <
operator control and turbulence froi
waves, proved tedious to interpret. Th
goal was to keep the leading edge 10 ci
below the water line, which was
function of ballast and vessel speed.
Skimming Oil
The high-viscosity oil tests distribute
a grand total of 41.6 m3 of oil during th
6 test days. A summary of the 57 tes
shows good performance. Recovei
efficiency (RE) averaged 66 percei
through all test conditions, dropping to
low of 48 percent in a 0.69-m harbl
-------
Pump and Engine Room
Bow
Figure 2. Soviet skimmer flow diagram.
chop at a forward speed of 1.0 m/sec.
The best RE (85 percent) was in calm
water at 0.77 m/sec; this figure
dropped slightly to 83 percent at 1.0
m/sec. The stationary operating mode
of the skimmer was outstanding, with
an RE of 94 percent. In this mode, the
vessel used reaction rudders and
sucked oil on the water surface from 4 m
away.
The best performance for throughput
efficiency (TE) was 90 percent in calm
water at 0.51 m/sec, a figure that
dropped to 80 percent at 1.0 m/sec.
Best performance in waves (0.36 x 6.95
m) produced a 77-percent TE at 1.0
m/sec, which dropped to 15 percent at
1.0 m/sec with a 0.7 harbor chop. TE
during stationary collection of the
available surrounding oil pool was 86
percent. Maximum recovery rate as
designed in the skimmer was verified to
be 12.4 mVhr.
The low-viscosity oil tests distributed
a grand total of 39.7 m3 of oil during the
4 test days. The skimmer collected an
average of 61 percent of the distributed
oil for all test conditions. A summary of
the 42 tests shows good performance
for the low-viscosity oil.
Recovery efficiency for low-viscosity
oils averaged 44 percent through the
tow tests, dropping to a low of 19
percent under the worst condition, a
0.69-m harbor chop at 0.51 m/sec. The
best RE (59 percent) was in calm water
at 1.0 m/sec; this figure dropped
slightly to 56 percent in waves (0.4 x
1.52 m). The stationary test RE was 51
percent in calm water, with the oil being
pushed around the vessel by the
reaction rudders and sucked in.
The best throughput efficiency was
89 percent in the advancing mode in
calm water at 0.51 m/sec. Performance
dropped to 85 percent at 1.0 m/sec in
calm water, and 74 percent with regular
waves (0.4 x 1.52 m). Throughput
efficiency in the stationary mode was
nearly 100 percent. The best maximum
recovery rate was 8.64 mVhr when
advancing at 0.51 m/sec in calm water.
Oil quantities in the port side storage
tank, vertical annuli, and main duct
Stern
were too low to measure in both the
high- and low-viscosity oil test phases.
The mechanical adjustments available
to the skimmer operator during the oil
tests were selected based on experience
from the fluid flow tests.
Photographs, motion pictures, and
video tape recorded several oil loss
sources. The major losses occurred in
advancing tests when oil was driven
under the broad-crested weir into the
main duct and was quite apparent
discharging out the propeller duct. This
was less obvious at slow speeds and in
calm water than at high speeds and in
waves. The bow doors did not cause
significant oil loss an any of their
selectable angles. This fact was sur-
prising in that they were not articulated
in the vertical plane.
Oil loss was not apparent in the
stationary tests. The large quantity of oil
stagnant in front of the skimmer was
quickly reduced to a sheen. The suction
was great enough to cause a vortex
originating at the oil surface several
meters out from the bow and running
-------
horizontally into the mouth of the
skimmer.
Conclusions and
Recommendations
The Soviet oil/debris skimmer, Model
2550/4, performed well, according to
its design requirements. The combina-
tion of a unique application of various
weirs into one system, its mobility, the
efficient use of energy, the incorporation
of series oil/water separation, the
propulsion system, and the use of high
oil/water flow conditions suggest that
the skimmer is the best of its class in
harbor operations. The actual oil collec-
tion performance was near design
specification and proved better in the
high-viscosity oil than in the low-
viscosity oil, as expected because of
entrainment. The high throughput
efficiencies in the normal advancing
and stationary modes were commend-
able.
The centrifugal pump used in the
gravity separation system was effective
in transferring oily water. The second
onboard pump, a vortex fire/ballast
system, had a significantly smaller
capacity. Future modifications of the
design should address the incorporation
of a positive displacement pump some-
where in the circuit. The two-man
operation of the vessel was difficult
because one man was needed on the
bow, and another was needed to divide
his time between the wheel house and
the pump controls. An additional man is
needed for skimming oil in the advancing
mode.
Future testing of the skimmer should
address in more detail the efficiency of
the coke filter system, the use of the gill
door in the advancing mode, and larger
oil volume performance tests requiring
significant quantities of oil in the port-
side storage.
The full report was submitted in
fulfillment of Contract No. 68-03-2642
by Mason & Hanger-Silas Mason Co.,
Inc., under sponsorship of the U.S.
Environmental Protection Agency.
H. W. Lichte is with Mason & Hanger-Silas Mason Co., Inc., Leonardo, NJ 07737.
John S. Farlow is the EPA Project Officer (see below).
The complete report, entitled "Performance Testing of the Soviet Oil/Debris
Skimmer," (Order No. PB 81-244 790; Cost: $6.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
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
U S GOVERNMENT PRINTING OFFICE. 1981 — 757-012/7347
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Pees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED
PS OOOU32*
KEGIO-M 5 LIBRARY
?30 S tjF.MrtbUK'i STREET
CHlLAbO IL b
AGEniCY
------- |