ASTM F1878-98(2004)
(Guide)Standard Guide for Escort Vessel Evaluation and Selection
Standard Guide for Escort Vessel Evaluation and Selection
SCOPE
1.1 This guide covers the evaluation and selection of escort vessels that are to be used to escort ships transiting confined waters. The purpose of the escort vessel is to limit the uncontrolled movement of a ship disabled by loss of propulsion or steering to within the navigational constraints of the waterway. The various factors addressed in this guide also can be integrated into a plan for escorting a given ship in a given waterway. The selection of equipment also is addressed in this guide.
1.2 This guide can be used in performance-based analyses to evaluate:
1.2.1 the control requirement of a disabled ship,
1.2.2 the performance capabilities of escort vessels,
1.2.3 the navigational limits and fixed obstacles of a waterway,
1.2.4 the ambient conditions (wind and sea) that will impact the escort response, and
1.2.5 the maneuvering characteristics of combined disabled ship/escort vessel(s).
1.3 This guide outlines how these various factors can be integrated to form an escort plan for a specific ship or a specific waterway. It also outlines training programs and the selection of equipment for escort-related activities.
1.4 A flowchart of the overall process for developing and implementing an escort plan is shown in Fig. 1. The process begins with the collection of appropriate data, which are analyzed with respect to the performance criteria and in consultation with individuals having local specialized knowledge (such as pilots, waterway authorities, interest groups, or public/private organizations, and so forth). This yields escort vessel performance requirements for various transit speeds and conditions; these are embodied in the ship's escort plan. When the time comes to prepare for the actual transit, the plan is consulted in conjunction with forecast conditions and desired transit speed to select and dispatch the appropriate escort vessel (or combination of vessels). A pre-escort conference is conducted to ensure that all principal persons (ship master, pilot, and escort vessel masters) have a good understanding of how to make a safe transit and interact in the event of an emergency.
1.5 This guide addresses various aspects of escorting, including several performance criteria and methodologies for analyzing the criteria, as well as training, outfitting, and other escort-related considerations. This guide can be expanded as appropriate to add new criteria, incorporate "lessons learned" as more escorting experience is gained in the industry, or to include alternative methodologies for analyzing the criteria.
1.6 This guide addresses physical control of the disabled ship with the assistance of the escort vessel(s). Other possible functions, such as firefighting, piloting, or navigational redundancy, are outside the scope of this guide. Also, this guide was developed for application to oceangoing ships in coastal waterways; it is not suitable for application to barge strings in riverine environments.
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Standards Content (Sample)
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An American National Standard
Designation:F1878–98 (Reapproved 2004)
Standard Guide for
Escort Vessel Evaluation and Selection
This standard is issued under the fixed designation F1878; 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 ducted to ensure that all principal persons (ship master, pilot,
and escort vessel masters) have a good understanding of how
1.1 This guide covers the evaluation and selection of escort
tomakeasafetransitandinteractintheeventofanemergency.
vessels that are to be used to escort ships transiting confined
1.5 This guide addresses various aspects of escorting, in-
waters. The purpose of the escort vessel is to limit the
cluding several performance criteria and methodologies for
uncontrolledmovementofashipdisabledbylossofpropulsion
analyzing the criteria, as well as training, outfitting, and other
or steering to within the navigational constraints of the
escort-related considerations. This guide can be expanded as
waterway. The various factors addressed in this guide also can
appropriate to add new criteria, incorporate “lessons learned”
be integrated into a plan for escorting a given ship in a given
as more escorting experience is gained in the industry, or to
waterway. The selection of equipment also is addressed in this
include alternative methodologies for analyzing the criteria.
guide.
1.6 This guide addresses physical control of the disabled
1.2 This guide can be used in performance-based analyses
ship with the assistance of the escort vessel(s). Other possible
to evaluate:
functions, such as firefighting, piloting, or navigational redun-
1.2.1 the control requirement of a disabled ship,
dancy, are outside the scope of this guide.Also, this guide was
1.2.2 the performance capabilities of escort vessels,
developed for application to oceangoing ships in coastal
1.2.3 the navigational limits and fixed obstacles of a water-
waterways; it is not suitable for application to barge strings in
way,
riverine environments.
1.2.4 the ambient conditions (wind and sea) that will impact
the escort response, and
2. Referenced Documents
1.2.5 the maneuvering characteristics of combined disabled
2.1 Code of Federal Regulations Document:
ship/escort vessel(s).
33 CFR Part 168—Escort Vessels for Certain Tankers, Final
1.3 This guide outlines how these various factors can be
Rule
integratedtoformanescortplanforaspecificshiporaspecific
2.2 IMO Resolutions:
waterway. It also outlines training programs and the selection
IMO Resolution A.601(15)—Provision and Display of Ma-
of equipment for escort-related activities.
neuvering Information on Board Ships
1.4 A flowchart of the overall process for developing and
IMO Resolution A.751(18)—Interim Standards for Ship
implementing an escort plan is shown in Fig. 1. The process
Maneuverability
begins with the collection of appropriate data, which are
2.3 Marine Safety Committee Circulars:
analyzed with respect to the performance criteria and in
MSC Circular 389/Interim Guidelines for Estimating Ma-
consultation with individuals having local specialized knowl-
neuvering Performance in Ship Design
edge (such as pilots, waterway authorities, interest groups, or
MSC Circular 644/Explanatory Notes to the Interim Stan-
public/private organizations, and so forth). This yields escort
dards for Ship Maneuverability
vessel performance requirements for various transit speeds and
conditions; these are embodied in the ship’s escort plan. When
3. Terminology
the time comes to prepare for the actual transit, the plan is
3.1 For purposes of clarity within this guide, the vessel
consulted in conjunction with forecast conditions and desired
being escorted is referred to as the “ship” or “disabled ship.”
transitspeedtoselectanddispatchtheappropriateescortvessel
The vessel accompanying the ship as its escort is referred to as
(or combination of vessels). A pre-escort conference is con-
the “escort vessel.”
This guide is under the jurisdiction of Committee F25 on Ships and Marine
Technology and is the direct responsibility of Subcommittee F25.06 on Marine
Environmental Protection. Available from the Superintendent of Documents, U.S. Government Printing
Current edition approved May 1, 2004. Published May 2004. Originally Office, Washington, DC 20402.
approved in 1998. Last previous edition approved in 1998 as F1878 - 98. DOI: AvailablefromtheInternationalMaritimeOrganization,4AlbertEmbankment,
10.1520/F1878-98R04. London, SE1 7SR U.K.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1878–98 (2004)
FIG. 1 Flowchart of the Overall Process for Developing and Implementing an Escort Plan
3.2 The escorting measures addressed in this guide are 3.3.1 Conventional Propulsion System—The propulsive
based on performance. thrust is fixed in a fore/aft direction.
3.2.1 The term “performance measure” refers to perfor- 3.3.2 Omni-DirectionalPropulsionSystem—Thepropulsive
mance capabilities that must be possessed by the escort thrust is steerable in any direction (360°) around the hull.
vessel(s) in controlling the disabled ship within a particular Examples are the azimuthing Z-drive screw propeller system
waterway. This requires a holistic analysis of the combined and the vertical axis cycloidal system.
maneuvering dynamics of the escort vessel(s) and ship within 3.4 The terms “direct mode” and “indirect mode” refer to
the waterway in ambient weather and sea conditions. two towing modes for exerting control forces on a disabled
Performance-based requirements involve extensive preplan- ship via towline from the escort vessel.
ning and analyses, but offer greater assurance that the escort 3.4.1 Direct Mode—The towline force is derived directly
vessel(s) actually will be effective. The methodologies and from the escort vessel’s propulsion system. In general, the
processes presented in this guide can be used in determining towline orientation is over the bow or over the stern of the
theperformanceenvelopeofanescortvesselatdifferenttransit escort vessel, and only the propulsive thrust vector parallel to
speeds and under a range of weather and sea conditions. the towline axis is effective on the disabled ship.
3.3 The terms “conventional propulsion” and “omni- 3.4.2 Indirect Mode—The towline force is derived from the
directional propulsion” refer to propulsion systems of the escort vessel’s hull drag as it is pulled along behind the
escort vessel. disabled ship (similar to a drag chute). High-performance
F1878–98 (2004)
escort vessels should have sufficient stability so that they can 3.6.8 grounding, n—impact of a ship’s hull with the sea
turn approximately sideways to the towline without capsizing bottom.
(tripping), thereby substantially increasing their hull drag and,
3.6.9 maneuvering coeffıcients, n—a set of numerical coef-
consequently, increasing their towline force. The propulsion ficients the are used in polynomial representations of the forces
system of these escort vessels is used indirectly to maintain an
acting on a ship in terms of the instantaneous state of the ship.
over-the-side towline orientation (rather than pull directly on
3.6.10 oppose maneuver, n—an escort vessel maneuver in
the towline itself). In the indirect mode, specially designed
which the assisting escort vessel(s) apply maximum steering
escort vessels can kite off to one side or the other of the
force to a disabled ship to turn the ship against its rudder. In
disabled ship’s stern, thereby imposing substantial steering
this maneuver, the objective is to return the ship to its original
forces on the ship as well as retarding forces to slow it down.
heading by opposing the rudder forces.
3.5 The terms “parameters” and “constraints” refer to addi- 3.6.11 propulsion failure, n—the ship is unable to propel or
tional conditions that define the escort scenario and response. actively stop itself.
3.6.12 response times, n—the sequence of time delays
3.5.1 Parameters—Additional details that are specified as
following a disabling failure on a transiting ship before the
part of the performance criteria to define more fully the
escort vessel(s) can apply corrective forces.
performance “problem” that must be solved by the escort
3.6.13 rescue tow, n—amaneuverinwhichtheescortvessel
vessel(s). Parameters are used to customize the performance
makes up lines and pulls the disabled ship; undertaken after all
criteria to reflect a particular waterway or a specific perfor-
forward way has come off the disabled ship.
mance objective. Examples of parameters include an initial
3.6.14 retard maneuver, n—an escort vessel maneuver in
ship speed at moment of failure, or winds, currents, and sea
state conditions that must be assumed during the escort which the assisting escort vessel(s) apply maximum braking
force to a disabled ship. In this maneuver, the objective is to
response.
take speed off the ship as quickly as possible by pulling astern.
3.5.2 Constraints—Limitations associated with “solving”
The control of a ship’s heading is not an objective. Also
the performance problem. Examples of constraints include the
referred to as arrest.
stability limits of the escort vessel (which limit how much
3.6.15 rudderfailure,n—theship’srudderislockedatsome
towline heeling moment the escort vessel can tolerate),
angle or it is swinging uncontrollably.
strength limits of the ship’s bollards (which limit how much
3.6.16 ship track/course, n—the path covered by the ship’s
towline force can be applied), or the navigable limits of the
center of gravity during a voyage, a waterway transit, or a
waterway (which limit how much maneuvering room is avail-
maneuver.
able).
3.6.17 tactical diameter, n—the distance, perpendicular to
3.6 Definitions:
the original course direction, between the ship’s center of
3.6.1 allision, n—a collision with a fixed object.
gravity at the start and at the end of a 180° heading change.
3.6.2 allowable reach, n—the straight line distance forward
3.6.18 zigzag maneuver, n—a test used to measure the
from the designated ship, parallel to its course direction, to a
effectiveness of the rudder to initiate and check course
point at which a grounding of an allision would occur.
changes. The maneuver is described in MSC Circular 644,
3.6.3 allowable transfer, n—the straight line distance from
Section 2.2.
the designated ship, perpendicular to its course direction, to a
3.7 Evaluation and Selection Variables:
point at which a grounding or an allision would occur.
3.7.1 transit speeds, n—the speed of the escorted ship
3.6.4 assist maneuver, n—an escort vessel maneuver in
measured through the water. The transit speed takes into
which the assisting escort vessel(s) apply maximum steering
account tidal and wind-driven currents. Transit speed is not
forcetoadisabledshiptoenhancetheturnoftherudder.Inthis
over ground (SOG) as measured by Global Positioning System
maneuver,theobjectiveistomaketheradiusofturnoftheship
(GPS), Loran, or radar.
as small as possible.
3.7.2 bollard pull, n—the maximum sustainable force that
3.6.5 emergency scenarios, n—the complete description of
the escort vessel is able to develop while pulling on a towline
the failure, the navigational situation, and the emergency assist
attached to a stationary object. The forward and astern bollard
response.
pulls are individually specified.
3.6.6 escort operating area, n—a subregion of the water- 3.7.3 dynamic pull (at a particular speed), n—the maxi-
way, harbor, bay, and so forth, that has been identified as the
mum sustainable force that the escort vessel is able to develop
regioninwhichtheescortvessel(s)willstandbyoraccompany while moving through the water at a particular speed.
the designated ship. The subregion may contain locations that
3.7.4 transfer, n—the distance perpendicular to the original
would require timely escort vessel assistance should the ship
track that a ship’s center of gravity travels in a 90° change in
experience a propulsion or steering failure, or both.
heading.
3.7.5 advance, n—the distance parallel to the original track
3.6.7 escort vessel, n—a vessel that is assigned to stand by
or is dedicated to travel in close proximity to a designated ship that a ship’s center of gravity travels in a 90° change of
heading.
to provide timely assistance should the ship experience a
propulsion or steering failure, or both. The escort vessel has 3.7.6 performance limits, n—limits of performance mea-
appropriate fendering and towing gear to provide emergency sures such that under all circumstances, the use of vessels,
assist capability relative to the demand of the disabled ship. equipment, or crew shall not place the life and safety of
F1878–98 (2004)
individuals in jeopardy. No applicable federal or state regula- 4.6.2 The failure scenario (rudder failure alone, or simulta-
tions should be exceeded in determining escort vessel perfor- neous rudder/propulsion failure, degree of failure, and so
mance capabilities and limits. forth);
4.6.3 Navigationalconstraintwithinwhichthedisabledship
4. Significance and Use
must be brought under control (such as allowable advance and
4.1 This guide presents some methodologies to predict the
transfer, cross-track error, and so forth);
forcesrequiredtobringadisabledshipundercontrolwithinthe
4.6.4 Wind, current, and sea conditions; and
available limits of the waterway, taking into account local
4.6.5 Time delays, failure recognition, decision making,
influences of wind and sea conditions. Presented are method-
escort vessel notification, escort vessel positioning, achieving
ologiestodetermine the control forces that an escortvesselcan
full power, and so forth.
reasonably be expected to impose on a disabled ship, taking
4.7 The anticipated users of this guide are:
into account the design of the ship, transit speed, winds,
4.7.1 Ship owners/operators who are required to select
currents, and sea conditions. In some instances, this guide
escort vessel(s) that meet the performance measures addressed
presents formulae that can be used directly; in other instances,
by this guide.
inwhichtheinteractionofvariousfactorsismorecomplicated,
4.7.2 Escort vessel designers/operators who need to evalu-
it presents analytic processes that can be used in developing
ate the performance capabilities of their vessels with respect to
computer simulations.
the measures addressed by this guide.
4.2 Unlike the more
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