ASTM F1778-97(2008)
(Guide)Standard Guide for Selection of Skimmers for Oil-Spill Response
Standard Guide for Selection of Skimmers for Oil-Spill Response
SIGNIFICANCE AND USE
This guide is intended to facilitate the oil spill response equipment selection process for local, regional, and national spill response teams. It is not intended to define rigid sets of equipment standards.
The effectiveness of the equipment chosen to combat an oil spill will depend on the oil type and environment(s) encountered, as well as other factors. This guide is intended to be used by persons generally familiar with the practical aspects of oil spill cleanup operations including on-scene response coordinators, planners, oil spill management teams, oil spill removal organizations, and plan evaluators.
Eleven general types of skimming systems are described in this guide. Each description includes a summary of the operating principle and a list of selection considerations.
Selection considerations are included to guide the user on the selection of a particular skimmer type or category. Users are cautioned that within each category there may be a wide variation in performance among various skimmers.
When selecting a skimmer for use in extremely cold conditions, consideration should be given to the effect of ice forming on the skimmer, changes in buoyancy, possible restriction of inlets, and changes to hydraulic efficiency. Because there may be wide variations in skimmer performance at extreme temperatures, even within a given category, ambient temperature is not included as a selection consideration.
SCOPE
1.1 This guide covers considerations for selecting skimmer systems for the recovery of marine-oil spills. The purpose of this guide is to provide oil spill response planners, equipment manufacturers, users, and government agencies with a standard on the equipment selection process for the removal of oil from the marine environment.
1.2 This guide does not address the compatibility of spill-control equipment with spill products. It is the user's responsibility to ensure that any equipment selected is compatible with anticipated products and conditions.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F1778 − 97(Reapproved 2008)
Standard Guide for
Selection of Skimmers for Oil-Spill Response
This standard is issued under the fixed designation F1778; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 nameplate recovery rate—the maximum skimming
capacity of a device under optimum conditions of oil type,
1.1 This guide covers considerations for selecting skimmer
slick conditions, and environmental conditions.
systems for the recovery of marine-oil spills. The purpose of
3.1.3 oil recovery rate—the volume of oil recovered by the
this guide is to provide oil spill response planners, equipment
device per unit time. F631
manufacturers, users, and government agencies with a standard
on the equipment selection process for the removal of oil from 3.1.4 recovery effıciency—the ratio, expressed as a
the marine environment.
percentage, of the volume of oil recovered to the volume of
total fluids recovered. F631
1.2 This guide does not address the compatibility of spill-
3.1.5 throughput effıciency—the ratio, expressed as a
control equipment with spill products. It is the user’s respon-
percentage, of the volume of oil recovered to the volume of oil
sibility to ensure that any equipment selected is compatible
encountered. F631
with anticipated products and conditions.
1.3 The values stated in SI units are to be regarded as
4. Significance and Use
standard. No other units of measurement are included in this
4.1 This guide is intended to facilitate the oil spill response
standard.
equipment selection process for local, regional, and national
1.4 This standard does not purport to address all of the spill response teams. It is not intended to define rigid sets of
safety concerns, if any, associated with its use. It is the equipment standards.
responsibility of the user of this standard to establish appro-
4.2 The effectiveness of the equipment chosen to combat an
priate safety and health practices and determine the applica-
oil spill will depend on the oil type and environment(s)
bility of regulatory limitations prior to use.
encountered, as well as other factors. This guide is intended to
be used by persons generally familiar with the practical aspects
2. Referenced Documents
of oil spill cleanup operations including on-scene response
coordinators, planners, oil spill management teams, oil spill
2.1 ASTM Standards:
removal organizations, and plan evaluators.
F625 Practice for ClassifyingWater Bodies for Spill Control
Systems
4.3 Elevengeneraltypesofskimmingsystemsaredescribed
F631 Guide for Collecting Skimmer Performance Data in
in this guide. Each description includes a summary of the
Controlled Environments
operating principle and a list of selection considerations.
4.4 Selection considerations are included to guide the user
3. Terminology
ontheselectionofaparticularskimmertypeorcategory.Users
3.1 Definitions:
are cautioned that within each category there may be a wide
3.1.1 encounter rate—the volume of oil per unit time variation in performance among various skimmers.
actively directed to the removal mechanism. F631
4.5 When selecting a skimmer for use in extremely cold
conditions, consideration should be given to the effect of ice
formingontheskimmer,changesinbuoyancy,possiblerestric-
This guide is under the jurisdiction of ASTM Committee F20 on Hazardous tion of inlets, and changes to hydraulic efficiency. Because
Substances and Oil Spill Response and is the direct responsibility of Subcommittee
there may be wide variations in skimmer performance at
F20.12 on Removal.
extreme temperatures, even within a given category, ambient
Current edition approved Sept. 15, 2008. Published September 2008. Originally
temperature is not included as a selection consideration.
approved in 1997. Last previous edition approved in 2002 as F1778 – 97 (2002).
DOI: 10.1520/F1778-97R08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5. Skimmer Selection Considerations
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1 Selecting a type of skimmer for a given application
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. involves examining the skimmer’s likely performance against
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1778 − 97 (2008)
a range of operational requirements. The following are recom- On the other hand, several skimming principles such as brush,
mended as a guide to this process, with the requirements drum, and paddle-belt skimmers operate most effectively with
grouped according to the operating environment, the slick more viscous oils.
conditions, and skimmer performance criteria. Comments on
5.3.1.1 Recommended viscosities for skimmer performance
each of these operational requirements, specific to each skim-
data are given in Guide F631. These include: 200, 2000, and
ming type, are given in Section 6.
60 000 mm /s. These values are referred to in the skimmer
selection considerations as low, medium, and high viscosity
5.2 Operating Environment:
oil.
5.2.1 Wave Conditions—Depending on the type of skimmer,
5.3.2 Slick Thickness—Slick thickness greatly affects the
waves may affect both the oil-recovery rate and the oil-
recovery rate of virtually all skimming principles, nameplate
recovery efficiency. In general, most skimmers work best in
recovery rates only being achieved with thick slicks. Slick
calm conditions with decreases in recovery rate and efficiency
thicknessalsoaffectstherecoveryefficiencyofmostskimmers,
as waves increase; in particular most skimmers are greatly
in particular those employing suction or weir skimming prin-
affected by short choppy waves. For each skimming type,
ciples. On the other hand, many skimmers can deal effectively
comments are given on the sensitivity to different wave
with thin slicks by varying the operating parameters of the
environments. (Classification information for calm, protected,
device (that is, for oleophilic devices, by reducing the speed of
and open-water environments is given in Practice F625.)
the oleophilic element, and by adjusting the weir settings for
5.2.1.1 Additionalconsiderationsforselectingskimmersfor
weir devices).
particular wave conditions are that both the skimming device
5.3.2.1 In evaluating a skimming principle based on ex-
andtherequiredsupportplatformareapplicabletotheintended
pected slick thickness, consideration should be given to
environment.
whether containment booms can be used to concentrate oil for
5.2.2 Currents—Should the operating environment of con-
recovery.
cern have significant water currents, this should be considered
5.3.2.2 In the skimmer descriptions in Section 6, reference
in the selection process. Many skimmers will not operate
is made to device performance in thin slicks, which is defined
effectively in currents greater than 1 knot due to decreases in
as continuous slicks less than 1 mm in thickness, or discon-
throughput efficiency. On the other hand, several skimming
tinuous patches of oil with an average thickness of less than 1
principles such as the sorbent belt, brush, submersion plane,
mm.
advancing weir, and boom skimmers rely on relative current
5.3.3 Debris—The presence of debris presents two concerns
for effective operation and are applicable in currents greater
than1knot.Severalskimmertypessuchastheoleophilicbrush in a skimming operation: first; that debris may restrict flow to
the skimming head, and second, that debris may interfere
andoleophilicropemopareavailableaswell,inconfigurations
that allow them to operate effectively in high currents. directly with the skimming component (that is, clogging or
obstructing openings, impeding moving parts). Some skim-
5.2.2.1 Comments on performance in currents are restricted
ming types, such as most oleophilic devices, are largely
tothosedirectlyrelatedtotheskimmingdevice.Ifcontainment
insensitive to the presence of debris. Suction and air conveyor
booms are used to collect or concentrate oil, or both, for
devices are generally tolerant of debris up to the size of the
skimming, additional operating limitations related to contain-
transfer hoses used.Weir devices, in general, are susceptible to
ment boom performance in currents may also apply.
clogging with debris; however, many weir devices use integral
5.2.3 Water Depths—Water depths may be a concern for
transfer pumps that can process a range of debris types. Where
skimming operations in nearshore waters and when supporting
applicable, comments are made on debris tolerance or sensi-
a shoreline cleanup operation. It is important to note that any
tivity in the selection considerations comments. It should be
draft limitations would apply to both the skimming device as
noted that these comments pertain to the general skimming
well as the required support vessel; certain skimmer types,
type, and that certain skimmers within a given category may
although not requiring deep water for their skimming compo-
include means of dealing with debris. Guidance for a range of
nent, may require large support vessels for deployment and
debris types respecting skimmer performance can be taken
operation.
from Guide F631, which lists a number of debris forms for
5.2.3.1 While many skimming types are available in a range
skimmer testing.
of sizes that may allow their operation in shallow waters,
certain types are generally applicable to shallow water depths
5.4 Performance Requirements:
and these are noted in the skimmer descriptions. Skimmer
5.4.1 Recovery Rate—For some applications the most im-
types in this category include rope mop skimmers, vacuum
portant performance criteria will be the product recovery rate.
systems,airconveyors,someweirskimmers,andsomesorbent
Although the various skimming categories are available in a
belt skimmers.
range of sizes and capacities, generalizations can be made on
5.3 Slick Conditions: expected recovery rates. In this guide, comments are made on
5.3.1 Oil Type and Viscosity—Few skimming principles expectedrecoveryratesonlyastheywouldapplytothevarious
operate with optimum effectiveness over a wide range of oil skimming principles and not to particular devices. For ex-
viscosities. For many skimmers, recovery rates will tend to be ample, weir skimmers and boom skimmers are available with
less than the reported maximum rates for oils that have a very high nameplate recovery rates, limited only by the available
lowviscosity,andforoilsthathaveaveryhighviscosity,either pumpingcapacity.Ontheotherhand,oleophilicskimmerstend
initially or as a result of weathering or emulsification, or both. to have a fixed upper limit of recovery depending on the size
F1778 − 97 (2008)
of the oleophilic surface used (that is, surface area of discs, used. In most boom skimmers, weir-type skimmers are used.
length and diameter of rope mop). Boomskimmersprovideacombinedcontainmentandrecovery
system.
5.4.1.1 Although specific skimmer performance data are not
6.2.1.1 Oil spill containment boom is often attached to each
included in this guide, users are reminded that a skimmer’s
side of the mouth of a skimmer in order to increase the sweep
nameplate recovery rate should be used with caution as it may
width. Although such a system would be similar to a boom
not accurately reflect skimmer performance under varying
skimmer, it would not meet the definition of a boom skimmer
conditions of slick thickness, slick viscosity, and environmen-
because the skimmer in the system could be used apart from
tal parameters. Where possible, performance data based on
the boom. In a boom skimmer, the skimmer is part of the boom
field use or experiments should be used, with reference to the
and is not intended to be used by itself.
slick and environmental conditions of particular concern to the
6.2.2 Selection Considerations:
user.
6.2.2.1 Oil Type—Applicable to low and medium viscosity
5.4.2 Recovery Effıciency—Selection of a skimmer based on
oils.
the expected recovery efficiency may be particularly important
6.2.2.2 Debris Tolerance—Debris must be screened or re-
depending upon the availability of storage, the availability of
moved from the skimmer opening.
systems to separate free water from the recovered fluids, and
6.2.2.3 Wave Conditions—Recovery rate and efficiency de-
thepermissibilityofdischargingdecantedwaterattherecovery
graded by choppy waves.
site. The expected recovery efficiency will, for most skimming
6.2.2.4 Currents—May be operated at currents greater than
categories, vary greatly depending on the thickness and vis-
one knot, at reduced recovery efficiency, by pumping at a high
cosity of the slick and on the environmental conditions at the
rate.
spill site.
6.2.2.5 Water Depth—Generally limited by towing vessels.
5.4.2.1 In general, skimmers using oleophilic principles can
6.2.2.6 Mode of Application—Requires relative forward ve-
be expected to have higher recovery efficiencies relative to
locity: may be operated in stationary mode if current present.
skimmers using weir or suction principles. Among weir skim-
6.2.2.7 Other—Typicallydesignedforvessel-of-opportunity
mers, devices in the induced flow category can be expected to
application.
have a high efficiency. As well, several skimming categories
6.3 Brush Skimmers:
are typically configured with onboard gravity separation,
6.3.1 Description—Brush skimmers are oleophilic skim-
which would enhance their overall efficiency. For skimmers
mers that pick up oil on the bristles of a brush. There are two
without onboard separation, oil/water separation should be
main configurations for the brushes: drum brush skimmers, in
considered to maximize the use of available storage.
whichthebrushesaremountedaroundtheperimeterofadrum;
5.4.3 Mode of Application—Comments on the mode of
and chain brush skimmers, in which the brushes are mounted
application include the ability to use in an advancing mode and
on several continuous loop chains. In each case the brushes are
the applicability to use on a vessel-of-opportunity.
rotated through the oil/water interface, picking up oil and some
5.4.3.1 Certain skimmer categories, such as oleophilic disc,
water.Therecoveredfluidisthencombedfromthebristlesinto
rope mop, and some weir skimmers are not generally used in
a sump. Both brush skimmer types are generally used in an
an advancing mode. Conversely, devices such as the boom
advancing mode. Chain brush skimmers are typica
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