EPA-R2-73-113
FEBRUARY 1973 Environmental Protection Technology
Use of Fire Streams
to Control Floating Oil
sS
Office of Research and Mjni
U.S. Environmental Protection
Washington. 0 C 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
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.
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EPA-R2-73-113
February 1973
USE OF FIRE STREAMS
TO CONTROL FLOATING OIL
by
Bernard Katz and Ralph Cross
Project 15080 FVP
Project Officer:
Frank J. Freestone
Edison Water Quality Research Laboratories, NERC
Edison, New Jersey 08817
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office. Washington, D.C. 20402
Price 75 cents domestic postpaid or £0 cents QPO Bookstore
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EPA Review Notice
This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the con-
tents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
ii
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ABSTRACT
The substantial momentum output of large volume, high pressure water
nozzles can be used to establish surface currents which are helpful
in controlling floating oil. When these induced currents have
components opposite to the ambient current, a turbulent rip zone is
established where the opposing currents cancel. It is mainly by
means of this zone that oil slicks may be influenced in a useful way.
An empirical relationship for the distance between the impact point
of the stream and the rip zone, as a function of nozzle output and
natural current speed, has been determined and compared with a
theoretical prediction based on a simplified model.
If the natural current is small, the rip zone's turbulence will be
slight and it will be a barrier to approaching oil. If the natural
current is large, the turbulence will be intense and the oil will be
churned downward and pass under the zone. Techniques for the use of
such large volume, high velocity water streams to control oil are
described and their limitations are discussed.
This report was submitted in partial fulfillment of Project 15080 FVP,
under the partial sponsorship of the Water Quality Office, Environmental
Protection Agency. '
iii
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CONTENTS
Section
I Conclusions
II Recommendations
III Introduction
IV Fire Streams
V Fire Stream Effects
VI Control of Floating Oil
VII Tactics for Small Natural Currents
VIII Tactics for Large Natural Currents
IX Using Fire Streams to Adjust Boom
Configuration
X Anchoring
XI Acknowledgments
XII References
XIII Glossary
Page
1
3
5
7
11
17
19
23
25
27
29
31
33
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FIGURES
Number
Volume and Momentum Discharge vs Tip 6
Pressure for Several Tip Diameters
Components of Fire Stream Momentum Discharge 8
at the Water Surface
Fire Stream Induced Patterns for Various Angles 10
of Orientation Between the Fire Stream and
the Natural Current
Distance Between the Fire Stream Inpact Point and 12
the Rip or Null-current Zone vs the Fire Stream
Momentum Discharge Divided by the Momentum Flux
per Unit Area of the Natural Current
Distance Between the Fire Stream Impact Point and 14
the Rip or Null-current Zone vs Fire Stream
Momentum Discharge for Various Natural Current
Speeds
Drawing Oil Out of an Embayment by Entrainment 20
vi
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SECTION I
CONCLUSIONS
The effectiveness of fire streams in controlling oil spills is directly
related to the amount of horizontal momentum that they put into the
surface. The optimum input of horizontal momentum to the water is
achieved when:
a) The largest available tip is used.
b) Solid streams are used.
c) The maximum pressure consistent with solid stream operation is used.
d) The monitor is horizontal or at a slightly depressed elevation.
e) The height of the monitor above the water is a minimum.
The fire stream establishes a fan-shaped current structure in the water.
If this current structure has components directed opposite to the natural
current, a turbulent rip zone will develop at its upstream edge. The
distance from the impact point and width of the "front" covered by the
rip zone increase as the horizontal momentum input to the water increases
and as the natural current velocity decreases. In open water, the net
flow in the rip zone is tangential to it and directed away from a hori-
zontal axis drawn parallel to the fire stream. But, when confined in a
channel so that the rip zone extends across the entire width of the
channel, there is no net flow in the rip and it becomes a null current
zone.
If the natural current is small, the turbulence of the rip zone is not
intense and it will be a barrier to floating oil. Under these conditions
the zone can be used to block or direct the flow of oil. In general, this
will be accomplished by directing the fire stream in the direction of
desired oil movement.
If the natural current is large, the turbulence of the rip zone will be
intense, and it will not be a barrier to floating oil. Under these
conditions, the fire stream may only be used to divert the oil usually
by directed the stream at right angles to the direction of the natural
current.
Since the fire stream must play on nearly the same spot for several
minutes before its effects are fully developed, and it must continue
to play on this spot if the effects are to be maintained, it will usually
be necessary to secure the fire boats when using their fire streams to
herd oil.
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SECTION II
RECOMMENDATIONS
Additional tests are needed to:
1. Determine more exactly the limiting velocity between "small" and
"large" natural currents.
2. Determine the depth of penetration of the fire-stream-induced current.
3. Establish more firmly the relationship between horizontal momentum
output of the fire stream, natural current speed, and size of the induced
current structure.
4. Perfect methods of deflection for large natural currents.
5. Perfect methods of entrainment.
6. Perfect methods of using fire streams to position boom arrays.
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SECTION III
INTRODUCTION
This report deals with the use of water streams from fire hoses or monitors
in controlling floating oil. It is also applicable, at least in part,
to any device such as the Battelle Boom, which employs this method.
However, fire streams and fireboats are stressed because in most cases
only they are capable of generating the large output of momentum needed
to materially affect significant amounts of floating oil, and are at
the same time available for rapid deployment in many large harbors.
Until recently, the main use of fire streams at an oil spill was to "break
up" the oil by playing the fire streams directly onto it. In cases of
highly volatile petroleum products this still may be the best procedure
for reasons of fire safety. But where explosion or fire is not a hazard,
it has become vitally necessary to control and contain the oil so that
environmental and property damage can be minimized and as much of the oil
as possible can be recovered. This is exactly opposite to dispersal -
the previous approach. Whereas dispersal required little in the way of
special knowledge or techniques, control and containment are a far more
difficult matter.
A number of experiments have been conducted with a view towards learning
to apply the tremendous pumping capacity of fire boats to best advantage
in controlling oil slicks. These have revealed that in certain situations
fire streams can be quite effective if used properly, but if not used
properly they may be totally ineffective or even counter-productive. The
experiments are continuing. Frequently the results of one experiment
will suggest other experiments and there still are many things to be
tried and learned. However, we believe that enough has been discovered
at this point to warrant the issuing of a preliminary report.
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10000
8000
9000
8000
— 7000
z
s
UJSOOO
O
tr
<
I
o
en
o
2 5000
4000
JOOO
2000
1000
6000
O
5000 ^
CO
o
_l
to
4000
UJ
o
I
O
to
o
•z.
UJ
3000
2000
1000
800
600
400
200
I I I I I
I I I I I I I
80
100
120 140 160
PRESSURE (PS.I.)
180
200
220
240
260
280
DISCHARGE (0 GAL/MIN) 8 MOMENTUM RATE (F SLUG FT./SEC2) = (|_BS.)
VS. NOZZLE PRESSURE ( PSI.) FOR SEVERAL NOZZLE DIAMETERS
FIGURE I
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SECTION IV
FIRE STREAMS
For the purposes of controlling oil slicks, the useful output
of a fire stream is its continuous discharge of momentum. This
momentum discharge - the time rate of momentum output - is pro-
portional to the product of the mass rate of water discharge
multiplied by the discharge velocity; therefore, it is also pro-
portional to the product of nozzle tip area and tip pressure
(velocity head). It is, in fact, equal in magnitude, but opposite
in direction, to the reaction force on the nozzle. Figure 1 shows
the volume discharge, 0, and the momentum discharge, F, vs tip
pressure for several different tip diameters.
Unfortunately, the entire momentum output of the tip is not usable.
There are two reasons for this:
a) The fire stream usually enters the water at an angle. There-
fore, it has a horizontal and a vertical component (Fig. 2); only
the horizontal component is useful for the control of floating oil.
The smaller the angle, A, the larger the horizontal component
will be and the smaller the vertical component will be. The angle,
A, is affected by the height of the tip above the water, the tip
pressure, and angle that the tip makes with the horizontal. De-
creasing the height of the tip, and increasing the pressure have
the effect of reducing the angle A. For any particular height
and pressure angle, A, will be the smallest when the tip is aimed
horizontally, and A increases as the angle between the nozzle and
the horizontal (whether elevation or depression) increases.
b) A portion of fire stream's momentum is lost to air resistance.
Although the process by which this happens is not fully under-
stood, it is known that, with the same pressure, air resistance
increases with increasing tip size, and, with the same tip air
resistance increases at an even faster rate with increasing
pressure. (D Also droplets are much more affected by air resist-
ance than solid streams, and the smaller the droplets the more
they are affected. Thus, nozzles which tend to break up the fire
stream into fog or fine spray are generally ineffective. By the
same token, solid streams should be operated at pressures well
below those at which coning occurs.
Of course, the longer the fire stream the greater the effects
of air resistance. Thus, while the smallest angl« of entry, A,
is achieved when the nozzle is aimad horizontally, a slight down-
ward angle of aim would shorten the fire stream and the increase
of momentum loss due to increased angle of entry x*ould tend to
be offset by the decreased loss due to the shorter fire stream.
On the other hand, an upward angle of aim increases the fire
stream length and the air resistance loss as well as increasing
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HORIZONTAL
COMPONENT
COMPONENTS OF FIRE STREAM MOMENTUM DISCHARGE
AT THE WATER SURFACE
FIGURE 2
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the angle of entry. Thus, depressing the tip from horizontal by
several degrees will have little effect, but elevation from the
horizontal produces rapid deterioration. For example: Nozzle
elevation of -5° produced effects that were virtually indistinguish-
able from 0°, but +10° elevation produced a much truncated pattern,
and at -20° elevation the fire stream had a negligible effect on
the water movement.
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FIRE STREAM INDUCED PATTERNS FOR VARIOUS ANGLES, 6, OF ORIENTATION
BETWEEN THE FIRE STREAM AND THE NATURAL CURRENT.
FIRE STREAM
IMPACT POINT
RIP
,X Q- 180°
IMPACT POINT
e =90°
FIGURE 3
THE RIP IS THE TURBULENT ZONE IN WHICH OPPOSING COMPONENTS OF THE
FIRE STREAM - INDUCED CURRENT AND THE NATURAL CURRENT CANCEL.
IN A NARROW CHANNEL THE RIP BECOMES A NULL-CURRENT ZONE.
10
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SECTION V
FIRE STREAM EFFECTS
When a fire stream plunges into a body of water, it establishes a fan-
shaped pattern of turbulent, aerated water with velocity components in
the general direction of the fire stream. The shape of the pattern
depends on the angle of the fire stream with respect to the natural
current (See Figure 3). Its size for a particular angle depends on the
stream, and on the magnitude of the natural current. Velocities in the
pattern, of course, vary, depending on where in the pattern they are
measured.
When the fire"stream-induced current has components directed opposite to
the natural current, a rip zone' will be established in the region where
these opposing currents cancel each other out. This zone determines the
up-stream boundary of the pattern. The rip zone is not a stable region;
it is turbulent and it meanders. However, it is by means of this rip
zone that floating oil may be affected in a useful way. In open water, the
net flow in the rip zone is tangential to it and directed away from a
horizontal axis drawn longitudinally through the fire stream. But,
when the fire-stream-induced current has components directed opposite to the
natural current, a rip zone will be established in the region where these
opposing currents cancel each other out. This zone determines the up-
stream boundary of the pattern. The rip zone is not a stable region; it
is turbulent and it meanders. However, it is by means of this rip zone
that floating oil may be affected in a useful way. In open water the
net flow in the rip zone is tangential to it and directed away from a
horizontal axis drawn longitudinally through the fire stream. But, when
the fire-stream-induced current is confined in a narrow channel so that
the rip zone extends across the full width of the channel, there is no
net flow in the rip and it becomes a null-current zone.
The distance of the rip or null-current zone from the impact point depends
on the horizontal momentum flux of the fire stream at the impact point and
on the speed of the natural current. For the case of fire streams directly
opposed to the natural current two attempts have been made to determine this
functional relationship. The first is based on an empirical analysis of
test results; the second is based on a theoretical analysis (presented in
detail in the Appendix) of a somewhat simplified model. Both results are
shown in Figure 4, which is a plot to logarithmic scales of the distance,
L, between the impact point and the null-current zone or rip zone vs. the
horizontal component of fire-stream momentum discharge, F^, divided by the
momentum flux per unit area, pV2 (where p is the water density, and V is
the velocity of the natural current through a vertical plane perpendicular
to Fh.
11
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1000
500
UJ
I
0.
or
1
—
-------
The theoretical result,
L = 10.2(Fh/pVz)
2N0.5
was determined from the model analysis. The corresponding line was
then drawn from this equation. The empirical result,
L = 9(Fh/pV2)°'3
was found by first plotting the data points on Figure 4, drawing a
best fit line through them, determining the corresponding equation, The
discrepancy between the two results in due almost entirely to the differ-
ing exponents (0.3 and 0.5) with the difference due to the coefficients
( 9 and 10.2) being barely significant. It should be pointed out that
L = 10.2(jyPV2)°-3
is dimensionally consistent (as it would have to be from the way it
was determined), while
, °'3
L = 9(Fh/pV2)
is not. However, the former does not correspond to any observed
results. This divergence between theory and experimental results is
discussed in the Appendix and deserves further investigation. In a
general way, the two results are in agreement with each other and with
expectation. Since F is porportional to tip area and tip pressure,
while pV2 increases with increasing natural current, both results
predict that larger distances between the impact point and the rip zone
are associated with larger tip areas and higher tip pressures, and with
lower natural currents. Smaller distances are brought about by the
reverse situation.
It is possible to express either result by a series of curves of L vs,
F^ for various current speeds. This has been done in Figure 5 for the
empirical relationship. If the current speed is known, Figures 1 and 5
may be used to estimate L for various tip sizes and tip pressures.
This may be done as follows:
(a) Find the momentum discharge, F, corresponding to the tip diameter
and tip pressure from Figure 1.
(b) .Take 90% of F as an approximation of F . (It is assumed that
the monitor elevation is nearly horizontal, and its height above the
water is not more than 20 feet, and tip pressure is greater than 25
pounds. If these conditions are not met, a smaller percentage of F
should be used.
13
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O.I KTS.
UJ
8
o.
Ct
P
200-
O 2
§ 2P
rn uj -
01 lo J
UJ
uZ
O
CC
UJ
O
CO
Q
50-
0.2 KTS.
1.0 KTS.
— 1.5 KTS.
r~r~r
1500
JOOO
FH (LBS)
5500
i—r
6000
FIRE STREAM MOMENTUM DISCHARGE
-------
(c) Find this value on the horizontal, F^, axis of Figure 5;
then read upward to the appropriate current velocity curve.
(d) The distance between the impact point and the null-current
zone will be the corresponding value on the vertical, L, scale of
Figure 5.
Though the relationships depicted in Figures 4 and 5 must, at this
point, be considered tentative and subject to modification as more
data are collected, the values of L obtained in this way should
give reasonable approximations provided the tip pressure and current
speed are accurately known. However, weak currents are difficult
to measure and are usually highly erratic. Significant deviations
from the above relationships will probably be due to imperfect knowledge
of current speed.
The length of the rip zone (approximately the width of the fan-shaped
pattern at its furthest from the impact point) is probably also
related to F^/pV , but because end points of the rip zone are
difficult to see when the natural current is small, not enough
observations have been made to establish this relationship.
However, a number of observations of the angle subtended by the
edges of the fan, at several different natural current speeds, have
all yielded values between 80 and 90 degrees. If this is borne out
by future work (in particular if the angle remains constant with
distance from the impact point, which it seems to do, and if it is
not also dependent upon the natural current speed) the relationship
between the length of the rip zone and its distance from the impact
point is a simple geometric one, and the dependence of the length of
the rip zone upon the fire stream's momentum discharge and the
natural current's momentum flux would follow from it.
For "small" natural currents (less than 1/2 knot) the rip zone is
well separated from the fan-shaped aerated water near the impact
point. It is a region of low turbulence which will divert or collect
oil and other flotsam. For "large" natural currents, (greater than
1 knot), the rip zone is coincident with the edge of the aerated
water. It is a region of high turbulence, and floating oil has been
observed to go under or penetrate it. It is expected that with
further experimentation the velocity range between "small" and "large"
natural currents can be narrowed somewhat.
15
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SECTION VI
CONTROL OF FLOATING OIL
The foregoing discussion of fire streams and their effects on the
water surface shall form the basis for the tactics to be developed
for using fire streams to control floating oil. However, it would
be futile to try to anticipate every possible situation and develop
cookbook methods for handling them. Rather, we shall suggest a number
of possible uses of fire streams, and describe methods for their im-
plementation. It will be left to the commanders on the scene to adapt
these to specific situations. It should be stressed that no tactic
should be followed blindly. The person in charge should frequently
and carefully observe the results of the procedure being employed to
be sure that the desired effect is being achieved. Often it will be
found that the initial evaluation of a situation was in error, or that
the conditions (e.g., current, wind) have changed. The required
changes in tactics may be minor, such as re-aiming the monitor, or
drastic, such as re-positioning the fire boat and/or boom array. Bear
in mind that control and clean-up of any fairly large oil spill is
likely to be a project of at least several days' duration. In
sheltered areas along the edges of the main channels, in peripheral
channels, and in parts of large shallow embayments such as New York
City's Jamaica Bay, there are places where currents are insignificant.
But in most places currents are a factor which will have to be consi-
dered. Since the currents are mainly tidal, it will be necessary,
in such places, to plan on rather drastic changes approximately every
six to twelve hours, depending on whether the tides are semi-diurnal
or diurnal. All this may seem obvious, but it has been observed that
one of the main causes of wasted effort at oil spills is inattentive-
ness. The other major cause is lack of knowledge, which is gradually
being remedied.
In most cases, fire streams will be used in conjunction with and in
fairly close proximity to (i.e., within several hundred feet of) a
boom array or bulkhead. Unless the current is virtually nil and the
extent of the oil patch small, operating a fire stream in open water,
far from an enclosure or barrier of some sort can, at best, result in
an insignificant diversion, and tat worst, can cause a greater dis-
persion or emulsification of the oil.
Also, it should be stressed that the fire stream should not be allowed
to play directly on the oil, but rather at a point far enough away so
that the stream does not "break up" the oil. For large caliber
streams and low natural currents this can be from 100 to 200 feet.
Remember the movement or blocking of the oil is accomplished by the
null-current zone and the flow patterns set up in the water rather
than by the fire stream itself. If the fire stream is allowed to play
directly on the floating oil, the oil will be churned up, emulsified,
and carried away by the natural current rather than contained.
17
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A constantly shifting fire stream has little opportunity to develop
a current structure. To fully develop its current pattern, the
fire'stream must play on nearly the same spot for several minutes,
and it must continue to play on this spot to maintain the pattern.
If the natural current is very small the angle of train can be varied
continuously back and forth through a small arc, but this should be
thought of as a broadening of the impact point. Tests have shown
that, while it is possible for most fire boats having twin screws to
maintain, for a few minutes, any heading with respect to natural
currents of a few knots in combination with any angle of train of
the bow monitor operated at pressures up to 150 psi, it is generally
impossible to do this for an indefinite period. And to control oil
effectively, the fire boat generally must maintain position as well
as orientation. For these reasons it will be necessary, in most cases,
to secure the fire boat when using the fire streams to control oil.
Furthermore, experience has proved that a large percentage of the
spills will probably occur near a bulkhead or dock to which the fire
boat can be moored.
As with other methods of oil control, fire streams are far, far more
effective in the presence of low natural currents than they are when
the natural current is high. Fortunately, in harbors the majority of
spills occur near shore, where the currents are often small, even though
the current in the main stream may be quite large. In cases of
collision, the ships involved should be moved to shore if possible as
a first step. For these reasons, and also because the oil film will
be thicker and less dispersed near the source, the major effort should
be expended at or near the site of the spill. Only after everything
possible is being done at the source, should any remaining capability
be expended in more distant areas.
18
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SECTION VII
TACTICS FOR SMALL NATURAL CURRENTS
In relatively confined channels, when the natural current is less than
1/2 knot, fire streams may be effectively used to set up a dynamic
barrier (the null-current zone) to stop the progress of the oil. For
example; they may be used to seal off the mouth of a slip or basin
to prevent oil inside from getting out or oil outside from getting in.
At 100 psi nozzle pressure a 3-inch tip was found to effectively cover
a basin 200 feet wide, and a 5-inch tip was able to cover a 300-foot
wide basin. These effective fronts can be augmented if necessary, by
using additional monitors to create adjacent null-current zones.
The null-current zone is similar to a boom in many ways, and it can be
used as a boom in cases where the fire boat can be maneuvered into a
suitable position. Its major disadvantage in this respect is that the
fire boat could not then be used for other activities. However, it has
two important advantages: the null-current zone can be easily penetrated
by small boats, while a boom cannot. And a fire stream can be activated
or adjusted much more quickly and easily than a boom can be deployed or
moved. Where speed is essential, fire streams may be used initially
to contain the oil until boom can be deployed, whereupon the fire boat
would be free to perform another function. Whether the boom should be
deployed between the oil and the fire boat, or the fire boat should be
included in the enclosed area, will depend on the nature of the other
function.
Fire streams may be used to move oil from under piers or between pilings
where it is not readily accessible for recovery. In most cases this may
be done by directing the fire stream so as to establish a flow under
the pier or through the pilings that will push the oil out. Where
this cannot be done, it may be possible to draw the oil out by entrain-
ment. In this process, the fire stream is used to establish a current
across the mouth of the area to be cleared, which in turn, will cause
an outward flow of surface water from the area. Figure 6 shows an
example how entrainment might be used. The arrows indicate the
direction of flow. Though this niethod has worked, we have not yet
made sufficient tests to optimize the techniques, and it should be
used with caution. In instances where a fire boat could not be well-
positioned for flushing out hidden oil, streams with hoses or pipe
extensions such as under pier or cellar pipes have been used with
considerable success. It is worthy of mention that, at high tide,
the water surface under many piers may be completely enclosed by the
piers' super structure, and the trapped oil cannot be driven out until
the water level lowers.
19
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SKIMMER
BOOM
V \ > '
I OM ,
ANCHOR
FIGURE 6
DRAWING OIL OUT OF AN EMBAYMENT BY ENTRAPMENT
20
-------
The efficiency of an oil pick-up device can be greatly increased if
fire streams are used to herd the oil towards the pick-up point. A
pick-up point will be in a semi-enclosed area (e.g., a corner where two
bulkheads meet, the apex of a boom array, the juncture between a boom
and a bulkhead, etc.)- If the area is small, hose and hand-held
nozzles will be most effective. The objective is to maintain a
continuous layer of oil on the water surface, having the maximum possi-
ble thickness, in the vicinity of the pick-up device. If there is
no natural current, the oil will continue to move towards the pick-up
point until a balance is reached between the hydraulic head in the oil
layer and the pressure exerted on the edge of the oil by the fire-
stream-induced current. The current should be very slight at the oil
edge to avoid churning the oil. As oil is removed by the pick-up
device, the edge of the oil will recede towards the pick-up point. If
there is a slight current opposing the fire-stream-induced-current, the
limit of effectiveness of the fire stream will be marked by a null-
current zone. In this case, the edge of the oil will not recede towards
the pick-up point. Rather, the oil will tend to collect along the
null-current zone, and it will be necessary to advance the impact
point of the fire stream. This can be done by elevating the tip, but
a price is paid in reduced efficiency. The better way is to increase
the tip pressure or to advance the nozzle. Think in terms of advancing
the null-current zone (which can be considered to be one of the
boundaries of the pick-up area) so that the pick-up area is completely
covered by the oil layer. If the natural current is towards the
pick-up point fire streams may still be useful in directing the oil.
21
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SECTION VIII
TACTICS FOR LARGE NATURAL CURRENTS
When the natural current is in excess of one knot, the null-current
zone ceases to be a barrier to floating oil. It is too turbulent,
and the oil mixes downward and is carried past it. In short, it is
no longer possible to block the movement of the oil. However, tests
have indicated that for currents up to about 2 knots, it may be possi-
ble to divert the oil; the method is similar to entrainment. The fire
stream is directed perpendicular to the natural current, as in Figure
3C, rather than against it. Oil carried by the current to the fire-
stream-induced pattern will be shunted to the end of the pattern. In
this case emulsification of the oil is unavoidable, but there is less
tendency for the droplets to be dragged downwards. Diversions of up
to 70 ft. have been accomplished in this way. Note that the area
between the fire boat and the impact point of the fire stream will
still be open to the unimpeded flow of oil. However, other streams
may be used to close this gap. The impact point of these auxiliary
streams should be slightly upstream of the impact point of the main
stream. Rail pipes could serve well to generate the auxiliary streams.
Some success in eliminating the gap and lengthening the deflection has
been achieved by using nozzles held horizontally very close to the
surface of the water so that the fire stream just skims the surface.
So far this method has been effective only in the absence of waves.
The objective is to concentrate as much high velocity momentum as
possible right at the water surface for the full length of the fire
stream. This is impossible when the wave height exceeds about half
the diameter of the fire stream because the wave crests will interrupt
the stream and the wave troughs will allow oil to pass under it.
Also wave induced rocking of the boat will often cause the nozzle to
dip below the surface thus periodically destroying the stream at its
source. Attempts to overcome these difficulties by increasing the
vertical spread of the stream and holding the tip higher have been
unsuccessful because the moemntum output is excessively diluted by the
reduced velocity and by the spreading of the stream itself.
i
Since the objective is clean-up of the oil, it will have to be diverted
to a place where this can be done. For the present this means a semi-
enclosed area where the currents are small. It may not be possible
to accomplish the necessary diversion with one fire boat, but if the
other boats are available, additional structures may be established
so that the necessary diversion can be accomplished in a step-wise
fashion. This diversion technique might also be used to protect an
area, for example a marina, by forcing the oil to flow around rather
than through it.
23
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For currents greater than about 2 knots there is very little that can
be done.in the way of control by fire stream.
24
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SECTION IX
USING FIRE STREAMS TO ADJUST BOOM CONFIGURATION
Fire streams can be used to modify the shape or position of a section
of containment boom. This is particularly useful at times when it may
be desirable or necessary to fasten only one end of the boom to a pier
or wall. The technique is more likely to be useful in protecting an
area rather than in corralling oil. The up-stream end of the boom is
fastened to the pier or bulkhead, and the fire streams are used to push
the boom outwards into the main stream, thus forming a protected embay-
ment which can be entered from the open, down-stream end. A similar
result can be achieved with a number of anchors. This is an alternative
method which is more quickly and easily activated and which might, in
some cases, be more effective.
Left to itself the boom will tend to line up with the natural current.
With the fire stream in use, that portion of the boom towards which
the fire stream is directed will "belly" outwards. Down-stream of the
"belly", the remaining boom, if any, will trail in the natural current
again. The extent of the "bellying" depends, of course, on the natural
current speed, the rate of momentum input to the water at the impact
point, the proximity of the impact point to the boom, the overall length
of the boom, and the angle between the fire stream and the natural current.
Using a 3-inch tip at 30 psi it was possible to hold 100 ft of boom out
in a current of 0.2 knots; with 120 psi in a 1 knot current the boom was
held out only 30 feet. Using a 5-inch tip at 120 psi, 70 feet of boom
were held out in a 1-1/2 knot current. In each case the total length
of boom was 200 ft.
Care must be taken to avoid "spilling" or twisting of the boom, and this
imposes limits on the fire stream output and/or the proximity of the im-
pact point to the boom. To achieve optimum displacement without causing
the boom to spill or twist it is best to start with tip pressures
moderate and/or the impact point at some distance from the boom, and
then gradually increase the pressure while closing the distance. The
impact point is generally advanced by increasing nozzle elevation, but,
for reasons already discussed in the section on fire streams, elevation
much above the horizontal is likely to be counterproductive.
There are two basic configurations: In the first, the fire boat is
almost directly down-stream of the tied end of the boom; as, for
example, when both are secured to a bulkhead which is parallel to the
current. The fire stream is directed against the current and between
the boom and bulkhead thus forcing the boom outwards. This method can
be used to protect an exposed area such as a small marina. Because the
fire stream and the current directly oppose each other along a line
containing the moored end of the boom, this configuration is somewhat
unstable, the boom having a tendency to fold back upon itself, unless
the impact point is kept about 100 feet up-stream of the trailing end
25
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of the boom. In order to initiate boom movement, it may be necessary
to use a small boat to open a space for the fire stream impact point
between the boom and bulkhead. Although the fire stream can impact
quite close to a wall without causing any damage, it should never play
directly onto the wall. If the currents are strong (greater than one
knot) some oil will go under any section of the boom making a large
angle with the current.
In the second configuration the fire boat is abeam of the boom and direct-
ing its stream perpendicular to the current; as, for example, when the
boom fastened to the end of a pier, and the fire boat is moored to the
side of the pier closer to shore. Though it is not possible to achieve,
under the same conditions, as much displacement as with the former method
there are no instability problems. Also there is evidence that a boom
supported by a fire stream in this way may be more effective than either
boom or fire stream alone. Oil that penetrated the barrier near the
moored end has been observed to skirt the inner edge of the boom.
It is frequently impossible to avoid a gap where the boom end is fastened
to a wall. This is particularly true where allowance must be made for
the rise and fall of the tide. When no other means are available, this
gap can be sealed quite effectively by means of fire streams. Since
the gap will usually be only several feet wide, small caliber streams
will in most cases be quite adequate.
26
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SECTION X
ANCHORING
In a previous section we explained the need for securing a fire boat in
order to use its monitors effectively. There are other activities (e.g.,
boom deployment and retrieval) which are much more quickly, safely and
easily performed from a moored boat than from one that is hove-to. Yet,
in many places where such activities might be required, there are no
mooring facilities. For these reasons an effective anchoring system
that can be rapidly and safely deployed will, at times, be a very valuable
aid.
Almost all boats carry anchors, but, on many fire boats and other type
boats of equivalent size, the anchor is a stockless or "patented" type
weighing about 1/4 ton. Because of the need for bow fenders, the anchor
is not kept in a hawspipe from which it can be readily dropped, and it
must be put over the rail. The equipment is so cumbersome that the
usefulness of the anchor in an emergency situation is virtually nil. Yet,
it is possible to put together an anchoring system which is at least as
effective in terms of holding strength, but which can be handled easily,
safely, and quickly by only two men. Its components and their specifi-
cations are listed below:
a) Anchor - 85 Ib Danforth (lightweight) standard. Holding strength
2,700 Ibs in soft mud; 19,000 Ibs in hard sand, (For comparison: the
holding strength of the 1/4 ton stockless is 1,800 to 7,200 Ibs depending
on the bottom; the reaction force on a 5-inch tip operating at 100 psi
is 3,926 Ibs, but surges in anchor line tension up to 1000 Ibs greater
have been measured,
b) Chain (50 ft) - 1/2", hot galvanized, proof coil. Working load
4,250 Ibs; proof load 8,500 Ibs; min. break test 17,000 Ibs,
c) Line (use a length equal to seven times the maximum anchoring depth)-
nylon, 1-1/4", 3 strand, hard lay. Working load 4125 Ibs; tensile
strength 37,000 Ibs.
Whether or not anchoring is possible in a particular situation will
depend on the type of bottom, the anchoring gear available, and the
current and wind speeds. But once anchored in a steady current, and with
the fire stream operating at a constant pressure and angle of train, an
equilibrium of forces will develop that will hold the boat steady.
However, any change in the natural current, or the fire stream will
force the system to seek a new equilibrium, which means that the fire
boat will move. If it is possible to set up in such a way that the
anchor line, current, and fire stream all have the same line of action,
these motions will be kept to a minimum.
27
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SECTION XI
ACKNOWLEDGMENTS
The practical use of fire streams at actual spills and at numerous test
exercises provided the basic information for this report. The Officers
and Members of the Marine Division of the NYFD and the personnel of
Alpine Geophysical Associates were the principal project participants.
The guidance of Mr. Howard Lamp'l, EPA Project Officer, and the coopera-
tion of the City of New York and the US Navy in providing the test basin
at Wallabout Creek, Brooklyn, New York, is gratefully acknowledged.
29
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SECTION XII
REFERENCES
(1) Casey, James F. (1970) Fire Service Hydraulics, Reuben H,
Donnelly Corp., N.Y.C., 427 pp
(2) Daily, James W. and Harleman, Donald R.F. (1966) Flu id Dynamic s
Addison-Wesley Pub, Co. Inc., Reading, Mass., 454 pp
31
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SECTION XIII
GLOSSARY
Ambient Current - any naturally occuring water current (eg. tidal,
Wind driven, river flow).
Boom - A floating barrier used to contain oil on the water surface, or
to direct its movement.
Coning - The break-up of a fire stream into tiny droplets and its spread-
ing into a conical shape as a result of excessive pressure.
Fire Stream - A stream of water produced by fire fighting apparatus.
Induced Current - An artificially produced flow of waterf such as that
caused by a boat's propeller or by a fire stream directed into a body
of water.
Monitor - A large nozzle with associated piping and controls attached to
the deck of a fire boat for producing large volume fire streams.
Natural Current - Ambient current.
Null Current Zone - A rip zone in which there is no net flow of water.
Rip Zone - A turbulent surface region where two oppresing currents have
equal strength. Usually there is no net flow through the rip zone, though
there is often flow under or around it.
Tip - The nozzle of a monitor or fire boat,
33
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SECTION XIV
APPENDIX
The data on counter-currents generated by directing a stream of water
from a fire nozzle into the current shown in Figure 4 is here augmented
with the development of a simple theory which explains the main features
of the resulting empirical relationship. Some of the simplifying assump-
tions necessary to this theory, however, have resulted in a incorrect
prediction of the exponent, even though the form of the result agrees
with the empirical result.
This theory is an attempt to predict the location of the "null point",
or point where the fire stream jet current exactly counters the natural
river or tidal current, when the fire stream is directed into the current,
It is developed from an analysis of a horizontal jet at the water surface,
and is based on the following conceptual model:
The fire stream hitting the water, generally at some downward angle, is
here considered to be a horizontal axisymmetric jet at the water surface.
The natural current in the water is assumed zero for the moment, The
initial diameter and velocity of the jet are chosen such that both the
water flow rate and the momentum flux through the lower half of the
axisymmetric jet match the flow and horizontal momentum flux from the
fire nozzle on the boat. The equation describing the velocity distri-
bution as a function of distance from the initial jet is used to calculate
the distance from the jet (or impact point of the fire stream) to the
point where the centerline velocity has decayed to the value of the
opposing natural current. Finally, it is assumed that the natural
current and the jet-induced current can be superposed, so that the above
point represents the null point.
The details are as follows:
The fire nozzle discharge velocity, Un, can be calculated from the
pressure, PQ, behind the nozzle; if tKe pipe diameter where the pressure
is measured is at least twice the nozzle diameter, the relationship
simplifies to
Un = (2 P0/p)1/2
where p is the mass density of the water. The jet momentum flux of a
horizontal nozzle is given by
FL = A_p U2 = 2 P A
h ^H n z *o An
where ^ is the cross-sectional area of the nozzle. For Nozzles aimed
at an angle © from the horizontal, the horizontal momentum flux becomes
F = 2 PQ A,^ Cos 6
35
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Considering now the half of the axisymmetric jet at the water surface,
the diameter of this jet, dj, in relation to the nozzle diameter, dn,
is given by d. = / 2 dn. This yields the same flow rate through the
"half jet" at the nozzle velocity as is delivered by the fire nozzle.
With the jet velocity, Uj, taken as the nozzle velocity, Un, (for nearly
horizontal nozzles), the momentum flux requirement is satisfied,
Away from the jet (at least, say, six diameters), the decay of the
centerline velocity of the jet with distance is approximately described
by
= 6.4 (dj/z)
where z is distance from the nozzle along the centerline of the jet, '
Setting U(z) equal to the natural current, V; replacing dj with
and U. with Un, and z with the distance to the null point, L, gives
L = 6.4 Ujd j = 9.0 U^
This can be converted to the form of the empirical equation
L = 9 (Fu/pV2) °'3
h
by noting that Fh - p ^ U^ = pvj- 1
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
.'. Rer
3. Accession No.
w
4. Title
USE OF FIRE STREAMS TO CONTROL FLOATING OIL
5, R
e.
S. Performing Organ'zation
7. Authors)
Katz, Bernard & Cross, Ralph
9. Organization
Alpine Geophysical Associates, Inc.
under contract to
New York City Fire Department
10. Project Wo.
15080 FVP
11. Contract/Grant No.
13. Type. Repoi and
Period Covered
12. apon<.nriBgC"wniz,~':-m Environmental Protection Agency, W.Q.O.
15. Supplementary Notes
Environmental Protection Agency report
number, EPA-R2-73-113, February 1973.
16. Abstract
The substantial momentum output of large volume, high pressure water nozzles can be used
to establish surface currents which are helpful In controlling floating oil. When these
latticed currents have components opposite to the ambient current, a turbulent rip zone
is established where the opposing currents cancel. It Is mainly by means of this zone
that oil slicks may be Influenced in a useful way. An empirical relationship for the
distance between the impact point of the stream and the rip zone, as a function of
nozzle output and natural current speed, has been determined and compared with a
theoretical prediction based on a simplified model.
If the natural current is small, the rip zone's turbulence will be slight and it will be
a barrier to approaching oil. If the natural current Is large, the turbulence will be
Intense and the oil will be churned downward and pass under the zone. Techniques for
the use of such large volume, high velocity water streams to control oil are described
and their limitations are discussed.
This report was submitted in partial fulfillment of Project 15080 FVP, under the partial
sponsorship of the Water Quality Office, Environmental Protection Agency.
17a. Descriptors
*011, "turbulence, *Eddles, "Hydraulics, "Jet, *Piers, "Velocity, *turbulence, *pressure
*Anchors, "Basins, *Boats, "Currents (water), *Docks, *0il Spills, "Nozzles, *Discharge,
*Tralnlng, "Harbors, "Inland Waterways, "Entrainment, Momentum Transfer, Emulsions,
17b. Identifiers
"Surface Currents, "Monitor Streams, "Hose Streams, "Fire Departments, "Booming,
"Herding, "Rip Zone, "Null Current Zone.
17c. COWRR Field & Group
18. Availability
19. S' urityC'ass.
(Report)
20. Security Class,.
(f-ge)
21. N?.of
Pages
22. Prf&
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
.U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. O. C. 2O24O
Abstractor Bernard Katz I institution Alpine Geophysical Assoc.. Jflg, for N.Y.F.D
WRE1C \OZ (REV. JUNE 1071)
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