ASTM F1878-98(2009)
(Guide)Standard Guide for Escort Vessel Evaluation and Selection
Standard Guide for Escort Vessel Evaluation and Selection
SIGNIFICANCE AND USE
This guide presents some methodologies to predict the forces required to bring a disabled ship under control within the available limits of the waterway, taking into account local influences of wind and sea conditions. Presented are methodologies to determine the control forces that an escort vessel can reasonably be expected to impose on a disabled ship, taking into account the design of the ship, transit speed, winds, currents, and sea conditions. In some instances, this guide presents formulae that can be used directly; in other instances, in which the interaction of various factors is more complicated, it presents analytic processes that can be used in developing computer simulations.
Unlike the more traditional work of berthing assistance in sheltered harbors or pulling a “dead ship” on the end of a long towline, the escorting mission assumes that the disabled ship will be at transit speed at the time of failure, and that it could be in exposed waters subject to wind, current, and sea conditions.
The navigational constraints of the channel or waterway might restrict the available maneuvering area within which the disabled ship must be brought under control before it runs aground or collides with fixed objects in the waterway (see allision).
The escort mission requires escort vessel(s) that are capable of responding in timely fashion and that can safely apply substantial control forces to the disabled ship. This entails evaluation of the escort vessel's horsepower, steering and retarding forces at various speeds, maneuverability, stability, and outfitting (towing gear, fendering, and so forth). This guide can be used in developing escort plans for selecting suitable escort vessel(s) for specific ships in specific waterways.
The methodologies and processes outlined in this guide are for performance-based analyses of escort scenarios. This means that the acceptability of a vessel (or combination of vessels) for escorting is based upon the ability to contro...
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 cond...
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F1878 − 98(Reapproved 2009) An American National Standard
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 (or combination of vessels). A pre-escort conference is con-
ducted to ensure that all principal persons (ship master, pilot,
1.1 This guide covers the evaluation and selection of escort
and escort vessel masters) have a good understanding of how
vessels that are to be used to escort ships transiting confined
tomakeasafetransitandinteractintheeventofanemergency.
waters. The purpose of the escort vessel is to limit the
uncontrolledmovementofashipdisabledbylossofpropulsion 1.5 This guide addresses various aspects of escorting, in-
or steering to within the navigational constraints of the cluding several performance criteria and methodologies for
waterway. The various factors addressed in this guide also can analyzing the criteria, as well as training, outfitting, and other
be integrated into a plan for escorting a given ship in a given escort-related considerations. This guide can be expanded as
waterway. The selection of equipment also is addressed in this appropriate to add new criteria, incorporate “lessons learned”
guide. as more escorting experience is gained in the industry, or to
include alternative methodologies for analyzing the criteria.
1.2 This guide can be used in performance-based analyses
to evaluate: 1.6 This guide addresses physical control of the disabled
1.2.1 the control requirement of a disabled ship, ship with the assistance of the escort vessel(s). Other possible
1.2.2 the performance capabilities of escort vessels, functions, such as firefighting, piloting, or navigational
1.2.3 the navigational limits and fixed obstacles of a redundancy,areoutsidethescopeofthisguide.Also,thisguide
waterway, was developed for application to oceangoing ships in coastal
1.2.4 the ambient conditions (wind and sea) that will impact waterways; it is not suitable for application to barge strings in
the escort response, and riverine environments.
1.2.5 the maneuvering characteristics of combined disabled
2. Referenced Documents
ship/escort vessel(s).
2.1 Code of Federal Regulations Document:
1.3 This guide outlines how these various factors can be
33 CFR Part 168—Escort Vessels for Certain Tankers, Final
integratedtoformanescortplanforaspecificshiporaspecific
Rule
waterway. It also outlines training programs and the selection
2.2 IMO Resolutions:
of equipment for escort-related activities.
IMO Resolution A.601(15)—Provision and Display of Ma-
1.4 A flowchart of the overall process for developing and
neuvering Information on Board Ships
implementing an escort plan is shown in Fig. 1. The process
IMO Resolution A.751(18)—Interim Standards for Ship
begins with the collection of appropriate data, which are
Maneuverability
analyzed with respect to the performance criteria and in
2.3 Marine Safety Committee Circulars:
consultation with individuals having local specialized knowl-
MSC Circular 389/Interim Guidelines for Estimating Ma-
edge (such as pilots, waterway authorities, interest groups, or
neuvering Performance in Ship Design
public/private organizations, and so forth). This yields escort
MSC Circular 644/Explanatory Notes to the Interim Stan-
vessel performance requirements for various transit speeds and
dards for Ship Maneuverability
conditions; these are embodied in the ship’s escort plan. When
the time comes to prepare for the actual transit, the plan is 3. Terminology
consulted in conjunction with forecast conditions and desired
3.1 For purposes of clarity within this guide, the vessel
transitspeedtoselectanddispatchtheappropriateescortvessel
being escorted is referred to as the “ship” or “disabled ship.”
The vessel accompanying the ship as its escort is referred to as
the “escort vessel.”
This guide is under the jurisdiction of Committee F25 on Ships and Marine
Technology and is the direct responsibility of Subcommittee F25.07 on General
Requirements. Available from the Superintendent of Documents, U.S. Government Printing
Current edition approved Nov. 1, 2009. Published January 2010. Originally Office, Washington, DC 20402.
approved in 1998. Last previous edition approved in 2004 as F1878 - 98(2004). Available from the International Maritime Organization, 4Albert Embankment,
DOI: 10.1520/F1878-98R09. London, SE1 7SR U.K.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1878 − 98 (2009)
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-Directional Propulsion System—The propulsive
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 (2009)
escort vessels should have sufficient stability so that they can appropriate fendering and towing gear to provide emergency
turn approximately sideways to the towline without capsizing assist capability relative to the demand of the disabled ship.
(tripping), thereby substantially increasing their hull drag and,
3.6.8 grounding, n—impact of a ship’s hull with the sea
consequently, increasing their towline force. The propulsion
bottom.
system of these escort vessels is used indirectly to maintain an
3.6.9 maneuvering coeffıcients, n—a set of numerical coef-
over-the-side towline orientation (rather than pull directly on
ficients the are used in polynomial representations of the forces
the towline itself). In the indirect mode, specially designed
acting on a ship in terms of the instantaneous state of the ship.
escort vessels can kite off to one side or the other of the
3.6.10 oppose maneuver, n—an escort vessel maneuver in
disabled ship’s stern, thereby imposing substantial steering
which the assisting escort vessel(s) apply maximum steering
forces on the ship as well as retarding forces to slow it down.
force to a disabled ship to turn the ship against its rudder. In
3.5 The terms “parameters” and “constraints” refer to addi-
this maneuver, the objective is to return the ship to its original
tional conditions that define the escort scenario and response.
heading by opposing the rudder forces.
3.5.1 Parameters—Additional details that are specified as
3.6.11 propulsion failure, n—the ship is unable to propel or
part of the performance criteria to define more fully the
actively stop itself.
performance “problem” that must be solved by the escort
vessel(s). Parameters are used to customize the performance
3.6.12 response times, n—the sequence of time delays
criteria to reflect a particular waterway or a specific perfor-
following a disabling failure on a transiting ship before the
mance objective. Examples of parameters include an initial
escort vessel(s) can apply corrective forces.
ship speed at moment of failure, or winds, currents, and sea
3.6.13 rescue tow, n—a maneuver in which the escort vessel
state conditions that must be assumed during the escort
makes up lines and pulls the disabled ship; undertaken after all
response.
forward way has come off the disabled ship.
3.5.2 Constraints—Limitations associated with “solving”
3.6.14 retard maneuver, n—an escort vessel maneuver in
the performance problem. Examples of constraints include the
which the assisting escort vessel(s) apply maximum braking
stability limits of the escort vessel (which limit how much
force to a disabled ship. In this maneuver, the objective is to
towline heeling moment the escort vessel can tolerate),
take speed off the ship as quickly as possible by pulling astern.
strength limits of the ship’s bollards (which limit how much
The control of a ship’s heading is not an objective. Also
towline force can be applied), or the navigable limits of the
referred to as arrest.
waterway (which limit how much maneuvering room is avail-
able). 3.6.15 rudder failure, n—theship’srudderislockedatsome
angle or it is swinging uncontrollably.
3.6 Definitions:
3.6.16 ship track/course, n—the path covered by the ship’s
3.6.1 allision, n—a collision with a fixed object.
center of gravity during a voyage, a waterway transit, or a
3.6.2 allowable reach, n—the straight line distance forward
maneuver.
from the designated ship, parallel to its course direction, to a
3.6.17 tactical diameter, n—the distance, perpendicular to
point at which a grounding of an allision would occur.
the original course direction, between the ship’s center of
3.6.3 allowable transfer, n—the straight line distance from
gravity at the start and at the end of a 180° heading change.
the designated ship, perpendicular to its course direction, to a
3.6.18 zigzag maneuver, n—a test used to measure the
point at which a grounding or an allision would occur.
effectiveness of the rudder to initiate and check course
3.6.4 assist maneuver, n—an escort vessel maneuver in
changes. The maneuver is described in MSC Circular 644,
which the assisting escort vessel(s) apply maximum steering
Section 2.2.
forcetoadisabledshiptoenhancetheturnoftherudder.Inthis
3.7 Evaluation and Selection Variables:
maneuver,theobjectiveistomaketheradiusofturnoftheship
as small as possible. 3.7.1 transit speeds, n—the speed of the escorted ship
measured through the water. The transit speed takes into
3.6.5 emergency scenarios, n—the complete description of
account tidal and wind-driven currents. Transit speed is not
the failure, the navigational situation, and the emergency assist
over ground (SOG) as measured by Global Positioning System
response.
(GPS), Loran, or radar.
3.6.6 escort operating area, n—a subregion of the
3.7.2 bollard pull, n—the maximum sustainable force that
waterway, harbor, bay, and so forth, that has been identified as
the escort vessel is able to develop while pulling on a towline
the region in which the escort vessel(s) will stand by or
attached to a stationary object. The forward and astern bollard
accompany the designated ship. The subregion may contain
pulls are individually specified.
locations that would require timely escort vessel assistance
should the ship experience a propulsion or steering failure, or 3.7.3 dynamic pull (at a particular speed), n—themaximum
both.
sustainable force that the escort vessel is able to develop while
moving through the water at a particular speed.
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 3.7.4 transfer, n—the distance perpendicular to the original
to provide timely assistance should the ship experience a track that a ship’s center of gravity travels in a 90° change in
propulsion or steering failure, or both. The escort vessel has heading.
F1878 − 98 (2009)
3.7.5 advance, n—the distance parallel to the original track 4.6 The “specified parameters” are additional details that
that a ship’s center of gravity travels in a 90° change of must be factored into the performance analysis. These param-
heading. eters might be specified by a regulatory agency imposing the
escort requirement, by a study group evaluating the feasibility
3.7.6 performance limits, n—limits of performance mea-
of escorting in a particular waterway, or by the ship or escort
sures such that under all circumstances, the use of vessels,
vessel operators themselves to define the performance enve-
equipment, or crew shall not place the life and safety of
lope of their vessels. Some examples of these parameters are:
individuals in jeopardy. No applicable federal or state regula-
4.6.1 A ship transit speed (at the moment of failure);
tions should be exceeded in determining escort vessel perfor-
4.6.2 The failure scenario (rudder failure alone, or simulta-
mance capabilities and limits.
neous rudder/propulsion failure, degree of failure, and so
forth);
4. Significance and Use
4.6.3 Navigational constraint within which the disabled ship
4.1 This guide presents some methodologies to predict the
must be brought under control (such as allowable advance and
forcesrequiredtobringadisabledshipundercontrolwithinthe
transfer, cross-track error, and so forth);
available limits of the waterway, taking into account local
4.6.4 Wind, current, and sea conditions; and
influences of wind and sea conditions. Presented are method-
4.6.5 Time delays, failure recognition, decision making,
ologies to determine the control forces that an escort vessel can
escort vessel notification, escort vessel positioning, achieving
reasonably be expected to impose on a disabled ship, taking
full power, and so forth.
into account the design of the ship, transit speed, winds,
4.7 The anticipated users of this guide are:
currents, and sea conditions. In some instances, this guide
4.7.1 Ship
...
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