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Powering the New Navy: Marine Gas Turbines 95
% Captain Roy E. Goldman, U. S. Navy (Retired)
Merchant Ships: Take a Number, Please 100
By John Freestone, Editorial Assistant, Lloyd’s Register of Ships
Powering the New Navy: Marine Gas Turbines
By Captain Roy E. Goldman, U. S. Navy (Retired), former Program Director for Marine Gas Turbines, Naval Sea Systems
Command
About two decades ago, the world saw the dawn of a technical revolution "'ben the USS Nautilus (SSN-571) and her successors went to sea and demonstrated capabilities which have added much to cbis nation’s naval might. In the intervening years, American nuclear-powered subrnarines and surface ships have con- hnued to play increasingly vital roles as their numbers have grown. Concurrent '"Vlth this growth, a number of factors— t*°t the least of which is economic— ave inhibited the Navy’s attainment of a fleet which does not depend on fossil Uels as its sources of energy. Consequently, a substantial proportion of the avy’s surface ships will continue to be convention ally powered for many years to come. The majority of the surface uips between now and the early years the next decade will not use steam tUrbines for propulsi on, but will be Powered by gas turbines derived from aircraft engines.
j November 1974, the missile- aunching hydrofoil Pegasus (phm-i) was aunched. The destroyer Spruance 1^-963) was starting builder’s trials out the same time and is due for 0rrimissioning later this year. These 3o° ships, each the leader of a class of and each powered by gas turbines, e the precursors of the Navy’s fleet of ®as tufoine-powered ships.
the period which immediately pre- e<a the launchings of the Pegasus and e Spruance, the U. S. Navy had no gas
turbine propelled ships of greater than about 250 tons displacement. There were only the 17 patrol gunboats of the USS Asheville (PG-84) class (three now in foreign navies) which combine diesel with gas turbine propulsion, plus a few odd experimental craft. These twin- screw gunboats constituted the Navy’s first serious application of the gas turbine for propulsive power. For cruising speeds below 12 knots they are powered by two Cummins 1450-s.h.p. diesels. For higher speeds—up to more than 40 knots—the diesels are uncoupled, and one General Electric LM 1500 gas turbine engine propels the vessel. These boats have been quite successful in coastal patrols during the Vietnam War and in shadowing operations in the Mediterranean. Further, they have provided a good personnel base for the Navy’s new gas turbine-powered ships. Since the LM 1500 is derived from the J-79 engine which powers the highly successful F-4 Phantom aircraft, it has certain similarities in maintenance and operation to the main engines which will power our new ships. In addition, there is a basic commonality of design in the controllable- pitch propellers used in the PGs and those being installed in two of the new gas turbine-powered ship classes: DD-963 and PF-109. From 1975 on, the proportion of gas turbine-powered ships in the Navy will continue to grow. Barring technical breakthroughs or a marked departure from present planning, by the early 1980s about one quarter of the Navy’s surface ships will be gas turbine powered. In addition to the two new classes just starting to be delivered, plans for that fleet now include the 50-ship patrol frigate (PF-109) class, a number of surface effect ships (SES), and others for a total of more than 100 gas turbine- powered ships. In fact, all of the Navy’s conventionally-powered newsurfacecom- batants will use gas turbines for propulsion. The Navy is crossing the threshold of a new era in ship propulsion, one that will change the entire spectrum of naval operations and support.
The use of gas turbines to propel ships is relatively new. The first naval craft to be partially propelled by a gas turbine was the Royal Navy’s MGB-2009, which went to sea in July 1947 with a 2,500 h.p. open cycle gas turbine driving the center shaft of three. The MGB-2009 was a success. Since then, gas turbine systems, either combined or pure, have been or are being installed in the Sheffield and Amazon-class frigates and in the through-deck cruiser Invincible of the Royal Navy, in the Federal German Navy Rate-class frigates, in the French Navy Georges Leygues-class destroyers, in the Soviet Kara, Krivak, Kashin, and Mirka classes, in the Canadian Iroquois-class destroyers, and in a variety of ships of other navies. In commercial service, there soon will be about 20 gas turbine- propelled merchantmen.
Marine gas turbines represent only a
very small percentage of the gas turbine power plants in service in all applications throughout the world. The vast majority of the gas turbines are used as aircraft propulsion engines or stationary plant prime movers. The demands of the marine application of gas turbine engines, particularly those placed on the propulsion plants of naval ships, differ from those of aircraft or stationary plants. Most of these differences are caused by the hostile nature of the sea- air environment and by the inherent requirements of a ship’s power train. Altering the gas turbine to make it suitable for use at sea has come to be
known as "marinization.”
The marinization process involves the use of different materials and coatings in that part of the engine known as the "hot section,” changing the design of the turbine frame to make it more rugged, removal of the propulsion fan if there is one, and providing a power takeoff coupling arrangement to the power turbine to make up to a reduction gear and clutch from which either a propeller or generator can be driven, depending on the application. The resultant shipboard model is referred to as a derivative engine.
Designing a marine propulsion engine from scratch was not considered for the first generation of gas turbine naval ships because of the required develop' ment time and costs. Stationary power plant engines are not generally con' strained by space and weight to the degree aircraft engines are, and most are not required to respond to rapid fluctuations in speed. As a consequence, aircraft gas turbines have, in genera, higher performance than their stationary counterparts because of their high rati° of thrust delivered per unit of weight- Aircraft gas turbine engines are usu ally lighter and much more compact than stationary engines, have higher
pressure ratios and higher operating temperatures, and more economical fuel consumption. Gas turbine engine power output varies with inlet air temperature. As outside air temperature increases, the amount of power available decreases drastically. In the sea-level temperature range, every degree Fahrenheit increase ln ambient temperature will decrease the power deliverable by a gas turbine engine by about %%. Another major difference between aircraft gas turbine engines and many stationary application engines is that stationary engines can rake advantage of regenerative tech- niclues, using a heat exchanger to transfer heat from the engine exhaust back t0 the compresser discharge to improve efficiency. At present, such techniques are never used in aircraft gas turbines and are not generally used in marine applications, because of the size of regenerator units.
The Navy decision to use aircraft derivative engines was also influenced by fhe following considerations, not necessarily in order of importance:
* Gas turbine power plants offer great savings in space when compared to steam or diesel installations. An entire gas turbine propulsion engine takes up less space than the main condenser of a steam plant of equal horsepower, ^hen compared to a low-speed diesel engine installation of the same power,
entire gas turbine engine takes up about the same space as one cylinder.
* Weight savings, particularly for the aircraft derivative engine, are similarly nigh. An average aircraft derivative ma- riUe gas turbine engine installation will ^e*gh less than 40% of an equal shaft
orsepower propulsion plant. Propul- Sl°n engine weight saving is perhaps not critical in a ship such as a destroyer but °bviously is in hydrofoils or surface e®fect ships. Thus, this is the only kind °f plant that would be practicable in die latter new vessels.
Gas turbine plants, particularly aircraft privative plants, are remarkably uncomP 'cated and require a bare minimum of 'Auxiliaries. This simplicity offers wide- Pread advantages in maintenance and ^ ease of automated operation. sh^ann'ng requirements for gas turbine 'P propulsion plants are thus considerably less than those of a steam plant. Uc*i of the maintenance will be done
by tenders rather than ship’s force. The number of people in the engineering department of each of the four Canadian Iroquois-class ships is 40, while well over 60 would have been required if the ships had steam plants. Similarly, the engineering department of the Spruance has only 54 officers and men, compared to more than 100 for a steam plant. In the Spruance, a normal underway engineering watch section will be five men; the Belknap (DLG-26)-class ships (about the same size) require 18.
► Because of their simplicity—with relatively few auxiliary equipments such as pumps, blowers, vacuum arrangements, tubing and piping as compared to steam plants—shipboard gas turbine plants are much less vulnerable than steam plants to shock and battle damage. Further, in the event of failure or damage to the few propulsion auxiliaries that do exist in a gas turbine plant, most, if not all, can be replaced by the ship’s crew with a modular on-board spare. Such replaceable items include igniter assemblies, fuel controls, and some bearings. Barring a catastrophic failure—for which the only real protection is redundancy such as that in the twin-screw, four- engine Spruance— to which gas turbine and steam ships are equally vulnerable, a gas turbine ship offers greater potential for mobility in a battle damage situation. One notable difference is that gas turbine power plant failures generally happen very rapidly as compared to most steam plant failures. However, repairs to a steam plant might require weeks or months, while the gas turbine plant can usually be back on the line in hours.
► Maintenance concepts and methods for the aircraft derivative engines can draw directly on the vast engineering experience and expertise that exist for aircraft gas turbines. Basic models of such engines have improved greatly because of numerous changes introduced as they have seen service. This process has come to be known as engine growth. In the past several years, the aircraft industry has increased engine reliability and reduced costs through more sophisticated maintenance techniques. Many of these improvements have been brought about by avoiding the wholesale replacement of engine parts that had historically been undertaken during periodic engine overhaul.
When engines are brought to an aircraft shop for rework today, the only component parts renewed are those determined to be worn out or defective by a knowledge of their condition or by a variety of monitoring and nondestructive testing techniques. The Navy’s gas turbine ships will benefit from these techniques and thus enhance material readiness at lowered costs.
► The Navy can draw on the considerable engineering capabilities of the Naval Air Systems Command and its various field activities. This ready-made infrastructure, with a proven history of being responsive to fleet needs, will strongly support these new ships. The engines in the Spruance, Pegasus and the other gas turbine-powered ships are supported by Naval Air Rework Facilities.
Gas turbine-propelled ships are much more maneuverable than steam or diesel-powered ships. By using a crash astern maneuver, many such ships have demonstrated their ability to stop in little farther than one ship length while moving at full power. In addition, the gas turbine ship can go from a cold iron condition to full power in less than ten minutes and from a stopped condition with engines idling to high speed in a minute or two. Both are tremendous military advantages, as is the fact that the engines can be controlled from the bridge.
► At or near maximum rated power output, aircraft derivative engine specific fuel consumption is now competitive with medium-speed diesel engine plants of similar horsepower and is lower than that of steam plants. Steam plants have an average specific fuel consumption of about 0.5 pounds per s.h.p. hour or more burning distillate fuel, while gas turbine and diesel plants consume about
0. 4 or less pounds per s.h.p. hour. Because the Navy’s worldwide commitments demand long-legged ships, a decision to build large numbers of gas turbine ships wasn’t made until the technology had reached the point where such a relatively reduced specific fuel consumption had been demonstrated. For that reason, both the Spruance and Pegasus classes—as well as the others planned—will offer better fuel economy than most, if not all, other gas turbine power plants currently in marine service. The cost of all fossil fuels has recently
Comparing the air pollution of a gas turbine power plant burning light distillate fuel with a 1200-psi steam plant burning Navy distillate, the gas turbine plant will emit a smaller amount of Pollutants—particularly carbon monox- 'de and oxides of nitrogen.
The simplicity of gas turbine engines Is such that major engine replacements are relatively uncomplicated. In the case °f the Spruance and Pegasus classes, the tUain propulsion engines are each replaceable by breaking them down into Wo major subassemblies, the gas gener- at0r and the power turbine. Both major Parts can be removed and new ones
become very high. Nonetheless, the use °f distillates, which are the best and most practical liquid fuels for gas turbines, continues to be more economical when compared to less thoroughly refined fuels such as bunker C.
^ Aircraft derivative marine gas turbines can be installed so that they operate wtth less air and waterborne radiated noise than steam or diesel engines. In addition, their structural vibration is lower, particularly at the high power levels. Since gas turbine engines burn clean fuels at near 100% combustion efficiency, gas turbine ships are relatively cleaner than other fossil fuel ships. While gas turbine engines can be steamed with a clear stack, just as steam 0r diesel plants can, the higher exhaust temperatures and greater exhaust gas flows may result in stronger infrared S1gnatures for gas turbine-propelled ships unless special precautions are taken.
installed in port with ease. In the case the destroyer, the only external Service required is the availability of a Crane with appropriate reach and capac- W An engine change will take three ^ays or less.
. lastly, a scrutiny of economic factors 'Uvolved reveals that marine gas turbine Pr°pulsion plants, particularly aircraft erivatives, are quite a bit less costly to ac<quire and install than steam or diesel c ants. This is true even though the t0tation of gas turbines cannot now be reversed. As a consequence, the addi- Onal cost Qf a Controllable-pitch pro- wr or a reversible type reduction gear ^rrangement must be included. Grossly .Peaking, the cost per unit horsepower 1974 dollars was over $100 for a diesel
plant, slightly less than that but greater than $90 for a steam plant, and significantly less than $90 for a gas turbine.
In recognition of the broad impact of gas turbine propulsion in the Navy, a logical step has been taken by the establishment of the gas turbine systems technician (GS) rating. Plans for the training and career patterns of the men who will have this rating are being made with the participation of staff personnel of a number of interested commands and offices in the Navy. The USS Spruance crew includes two officers and 15 men who have received gas turbine training at a new school established at Great Lakes, Illinois.
The men who wear the GS rating badge will represent a new breed of sailor. They will be responsible for the operation and maintenance of gas turbine engines used for propulsion and auxiliary power,controllable-pitchpropel- lers and their hydraulics, reduction gears and clutches, and also the automated electronic control systems that are much more complex than steam plant controls. Their watchstanding duties will require a high degree of knowledge but will not be as difficult as steam plant watchstanding because of a centralized and automated data display and automatic logging features.
Maintenance of the gas turbine engines themselves will be neither difficult nor time consuming for the crew. That part of their work will be limited to periodic checks and when-necessary modular replacement of external engine parts. The most difficult part of the GS’ maintenance responsibilities will be concerned with the automated control systems. In effect, the gas turbine systems technician will be a combination of today’s engineman, IC electrician, and a bit of electronics technician. The main propulsion personnel of the Spruance and Pegasus are enginemen and IC men, many of whom have served in the Ashe- ty//<?-class PGs.
By the 1980s the gas turbine plants in the fleet—in addition to that in the previously discussed Asheville class will include:
Spruance (DD-963) class; Twin-screw destroyers 6,900-ton full-load displacement are totally powered by gas turbines. Each will have four 20,000-s.h.p. General Electric LM 2500 propulsion gas
turbine engines and three Allison 501K-17 gas turbine engines for auxiliary power each driving a 2,000-kw. generator set. They have controllable pitch propellers.
Pegasus (PHM-i) class: These 210-ton full-load displacement ships will have a combined diesel or gas turbine (CODOG) propulsion system with two Mercedes-Benz diesel engines for cruising in the hullborne mode and one General Electric LM 2500 gas turbine engine for foilborne high speed. The propulsors are water jets rather than screws. Ship’s electrical power will be provided by a pair of Garrett Airesearch ME 831-800 gas turbine engines driving 300-kw., 400-hertz generator sets.
PF-109 class: These 3,400-ton full-load displacement ships will have a crew of fewer than 200 through automation techniques. Each will be driven by a single controllable-pitch propeller of the same design as that in the Spruance class and will be powered by two General Electric LM 2500 gas turbine engines. Auxiliary power prime movers will be diesels.
Surface Effect Ships: There will be at least two different types of gas turbine- propelled surface effect ships, to provide the nucleus of a 100-knot Navy. Currently there is a design effort toward the construction of a class of these ships with destroyer capabilities and a class of air-capable surface effect ships of perhaps 10,000 tons displacement. Early units will probably be powered by General Electric LM 2500 engines, to be followed by units powered by the 35,000- s.h.p. Pratt & Whitney FT-9 engine currently being developed under a Navy contract.
With the first deliveries of this new fleet later this year, there will certainly be a period of reeducation and revision of thinking such as attends any innovation. In addition, the power plants themselves will exhibit certain teething problems and bugs that will have to be ironed out. The U. S. Navy is firmly committed to the use of gas turbines for ship propulsion. Recently, this commitment has been strengthened as firm decisions have been made to apply gas turbine power in an ever-widening variety of ship classes, each of which will add new dimensions to the Navy’s ability to carry out its missions.
Merchant Ships:
Take a Number, Please
By John Freestone, Editorial Assistant, Lloyd’s Register of Ships
Much confusion and inconsistency concerning merchant ship types exist in the shipowning, building, and associated engineering industries. Different interpretations of a vessel’s nature are found even within the walls of a single institution as different departments base their records on varying criteria. Shipping statistics have long been prepared and quoted, but heretofore the emphasis has been on flag and tonnage. Now, with the increasing number of analyses being made of ship design, performance, and demand—all of which depend on reliable, consistent, and often widely-based data—there is a real requirement for a type classification that enables different data sources to be compatible in this respect. •
Therefore, I propose a type classification based on function. Design, form, arrangement, appearance, dimensions, and structural features all proceed from the ship’s function. Function, moreover, is something that can be readily ascertained by the technically interested party and the less technical alike, by those with access to plan and specification and those without. The larger the number of ships involved in any sample (the world’s seagoing fleet now exceeds 50,000 ships), the scantier becomes the available information that is common to all. Builders’ plans may be available for one vessel, while for a similar vessel only a four-line reference-book entry can be found.
Depth of detail available thus varies, as does the requirement for it. What is fundamental is a basic categorization into which any vessel can be readily fitted. Further sub-type categories are also proposed. These can be omitted entirely or developed either partially or fully according to requirements.
If required, an initial breakdown in a single-digit field may be used to distinguish basic hull forms, thus:
1. Surface displacement single hull (the "conventional” ship form)
2. Twin/multihull
3. Air cushion vehicle
4. Hydrofoil
5. Flexible towage container, e.g., "Dracone”
6. Submersibles
7. Floating docks
8. Rigs and platforms
9. Buoys
Some 23 basic type categories may be employed:
Passenger (Pass.)
Ferry (Ferry)
Containership (Cont.)
General cargo (Gen. Cgo.)
Specialized cargo (Sp. Cgo.)
Bulk carrier (Bulk)
Ore carrier (Ore Ca.)
Gas carrier (Gas Ca.)
Tankers (Tank.)
Specialized tankers (Sp. Tank.)
Towing (Tug)
Fishing (Fishing)
Icebreaking (Ice-Br.)
Research and survey (Res.)
Hopper (Hopper)
Dredging (Dredger)
Factory (Factory)
Other special service (Sp. Svc.)
Barge (Barge)
Yacht (Yacht)
Sailing (Sail)
Great Lakes (Laker)
Naval (Naval)
Because these categories are frequently found in combination in one hull, such combinations must be provided for. Any attempt to select the "main function” and ignore the others returns us to the present confusion and inconsistency.
The basic types occur (or appear likely to do so) in as many as three functions in one hull (e.g., Pass./Gen. Cgo./Ferry).
This necessitates a three-digit field of coding with the function codes arranged so that all combinations occur laterally- Any vertical combinations will require multiple coding in one column, which is generally inadvisable. The basic types to be grouped in each column need therefore to be mutually exclusive. For example; gas carrier and tug can be grouped together but passenger and cargo cannot.
The Basic Type Code is therefore:
|
| First | Second | Third |
|
| Column | Column | Column |
| l | Pass. | Gen. Cgo. | Barge |
| 2 | Bulk | Sp. Cgo. | (Yacht) |
| 3 | Gas Ca. | Tank. | Sp. Tank |
5$ 55 | 4 | Tug | Factory | Ferry |
5 |
| Ice-Br. | Fishing | |
1 | 6 | Research Dredger | Sp. Svc. | |
0 | 7 | (Sail) | Naval | Laker |
| 8 | Hopper |
| Ore ca. |
| 9 |
|
| Cont. |
0 is used whenever none of the above apply in the digit being coded.
The Basic Code is thus:
100 Passenger 010 General cargo 200 Bulk carrier 020 Specialized cargo 300 Gas carrier 030 Tanker
3 Special tanker 400 Tug
040 Factory
4 Ferry
050 Icebreaker
5 Fishing
600 Research and Survey
6 Special service 070 Naval
The top photo shows a fishing vessel, found in many local variants. Under Mr. Freestone’s system, it is coded 005:024.069. Examples of special service vessels are the lightship (006:039), center, and merchant marine training ship (006:079). All photos, except as noted, are by the author.
7 Great Laker 060 Dredger
1 Barge 700 Sailing
2 Yacht
8 Ore carrier
9 Containership
The combination types arrived at by simple addition are:
14 General cargo and ferry 019 General cargo/containership 021 Specialized cargo barge 024 Specialized cargo and ferry 026 Specialized cargo and special service 031 Tanker-barge 033 Tanker, part conventional/ part special 040 Factory 045 Fishing factory
53 Icebreaking special tanker
54 Icebreaking ferry
056 Icebreaking and special service 061 Dredger-barge 066 Dredger and special service 076 Naval and special service 1°4 Passenger and ferry HO Passenger-cargo *14 Passenger-cargo and ferry Ho Passenger-special cargo H4 Passenger-special cargo and ferry H6 Pass./naval/special service ^07 Great Lakes bulk carrier Ho Bulk/Specialized cargo ■Ho Bulk/oil carrier ^33 Bulk Cargo/Oil/Specialized Tanker 238 Ore/Bulk/Oil carrier 3°3 Gas carrier/Specialized Tanker 330 Gas carrier/Tanker 333 Gas carrier/Tanker/Specialized Tanker
4°1 Articulated ship (i.e. "tug” plus "barge”)
134 Tug and ferry
405 Tug and fishing
406 Tug and special service 4^6 Tug/Specialized cargo/
Special service 450 Tug and icebreaker *^5 Research fishing ^°6 Survey/research and special service 0 Survey/research and icebreaker 2 Sailing yacht
Sailing and special service fe e. sail training)
710 Sailing-general cargo 860 Hopper dredger
By searching one, two or three digits, individual basic types with/with- out, all/some of their combination types may be selected or eliminated. For example:
► If only one type is required, search in the one column only—say, code 1 in the first column gives all passenger ships. Searching the other two columns identifies or eliminates combination passenger- cargo ships and passenger-ferries: 110,104, 114, 124.
► Searching the second and third digits for 3 gives all types of tanker. A 3 in the first digit brings in gas carriers.
► 010 and 020 in the three digits isolate the numerically large cargo ship categories, at the same time eliminating their combination types.
Several of these basic types hardly require definition. The following notes are for guidance in respect to the others:
General Cargo
The common single/shelter/multi-deck general cargo carrier. Ignore special rooms, tanks, spaces for specialized cargoes unless they determine the whole function, in which case we have a specialized cargo ship, such as a livestock carrier or vehicle carrier. Cargo ships may be regarded as two close families, one the general cargo type (010) having only a few "offspring” (refrigerated, collier, container facility, etc.), the other
This coaster would be considered a general cargo ship {010:027), though of small dimensions.
A modern break-bulk general cargo ship, part refrigerated (010:027.060)
|
|
i iSiSfa! |
|
fry* » JSWaJQsdsW |
|
• MAHTH ELMSHOM,
A specialized cargo/ferry combination, this carries vehicles and deck passengers {024:069.071.084).
Despite their huge deadweight, the very large crude carriers (VLCCs) are still tankers (030:045).
General cargo/barge combination, found in coastwise and inland trading (011:027)
tNCHGY OCMBUTKm
The increasing use of the containership has made it a basic type (020:009).
This combination vessel has the structural arrangements of a tanker and proportions of a barge (031:045).
the special cargo type (020) being vessels built or adapted for specialized and restrictive cargoes, such as livestock, vehicles (Ro-Ro), and pallets. The general user of this code can accommodate ah the cargo vessels in two categories (010 and 020), which readily distinguish the specialized carriers from the general purpose. More detailed breakdown of the special cargo ships is provided by the sub-type coding below.
Containership
Vessels with fixed cellular guides for carrying containers. Part container ships are combination cargo/containerships. Other general cargo ships and Ro-Ro specialized cargo ships may have container facilities.
Bulk
Includes bulk carriers, ore carriers, and ulk carriers strengthened for ore cargoes. To distinguish bulk carriers proper (*n the absence of structural information) from a one-deck general cargo ship the following criteria are suggested: 400 • kp length, machinery aft. Colliers are °und in either category Bre carrier
distinguished structurally by two longitudinal bulkheads placed well inboard, e ore space lying between these and a °ve a deep bottom space.
Bulk/Tank/Ore
Combinations include bulk/oil, ore/oil ar,d obo carriers, distinguished by subtype codings
'Specialized Tanker
“fuid cargo carriers other than the gas Cartier and the conventional oil tanker
factory Ve .
sseis such as whaling factories and fish °duct processing vessels. Factory th ^Crs are a comhination type since ey can trawl as well as process passenger
kJSsels with more than 12 passenger
pern Ves l •
sels in which the number of day nu bert^e<I) passengers exceeds the ^jnber (if any) of night (berthed) pas, gors. Thus a Dover-Ostende "mail- ferates as a combination passenger- ^ (104), a transatlantic liner as SSenger (ioo) or passenger-cargo (110), the cross-river passenger ferry and the estuarial excursion ship as ferries only (004), the cross-channel train/car- ferry as specialized cargo/ferry combination (024) or (124), according to the actual number of berths.
Fishing
Inclusive of all catching types, trawlers, line fishing craft, and whale chasers
Laker
The bulk carrier peculiar to the Great Lakes should be dealt with as a combination type (207), facilitating the choice of their inclusion/exclusion when bulk carriers are required
Naval
Naval auxiliaries built on mercantile lines and therefore sometimes of relevance to merchant shipping analyses. These would include supply ships and special tankers, among others. Equally this code facilitates their ready removal from any sample.
Dredger
Inclusive of all types, suction, cutter, dip, bucket, etc. All hopper dredgers are combination dredger-barge types (860).
Barge
Includes large deep-sea towed craft and sheltered water log tippers. Admittedly difficult to define on the margins of the small coastal tanker and cargo ship, but even here, using combination codes (031, 011) errors of omission at least are obviated. A breadth: depth ratio of 2.5 :1 could be an arbitrary dividing line.
Hopper
Vessels arranged for the discharge of cargo or spoil through the bottom.
Sail
This may be claimed as a distinction by means of (main) propulsion rather than by function. If however, sailing vessels are present in the sample, the characteristics peculiar to the sailing vessel may demand a distinct category without resorting to a separate propulsioncoding arrangement. Therefore this anomalous type has been integrated into the scheme.
Yacht
Powered yachts. Auxiliary powered sailing yachts are combination sail-yacht types (702).
Special Service
These include the wide range of specialist craft, such as pilot cutters, drilling rig supply vessels, lightships, mooring tenders, crane ships and pontoons, salvage vessels.
The more detailed of the criteria mentioned (e.g. passenger berths) are frequently as readily available for the relevant ships as other apparently more obvious characteristics are for other ships.
Other criteria:
Structural features and dimensions are, with the few exceptions above, of limited significance. Tonnage, capacity, means of propulsion, actual cargos carried (as opposed to those the vessel is designed for), seagoing or nonseagoing, special features (framing, cargo gear, side/bow doors, size of hatches), are subjects for separate categorization and coding distinct from the ship type. Some exceptions are shown below where such a characteristic (e.g. "ore,” "stern trawling”) determines the basic type or sub-type.
Combining Basic Types with the Initial Breakdown.
Probably the greatest scope for future developments in sea transport lies here. Provision is made for true passenger hydrofoils, container-carrying hovercraft, submarine tankers, and the wider use of the catamaran hull. The wide publicity given to innovations should not obscure their assessment; frequently they will be found to be truly variants or sub-types of established basic types.
Sub-Types
If a further breakdown is required, sub-types may be chosen in depth and range according to the nature of the sample or the object of the analysis. That being so, they must conform to a specific parent/family group, a basic/ combination type.
A list of possibilities follows, grouped under the parent basic type category. Note that containers can be carried by general cargo ships (010) that have a container facility or by special cargo ships (020). Searching the sub-types locates all container carriers; searching the basic type divides the container ships proper from the remainder.
Experimental combination of tanker and icebreaker (030:045)
Suction dredger which carries its own spoil in hopper spaces (060:073:860)
An example of the transoceanic passenger liner, usually with some cargo space (110:027)
A passenger/specialized cargo/ferry combination with Ro-Ro facilities for autos and trailers (124:071.084)
A combination of sail, general cargo, and barge (711:027.106), a retrospective category no longer in commercial use
10 General Cargo OH Collier
°12 Container facility (non-cellular)
027 General cargo
048 Passenger (1-12 berths)
060 Part Refrigerated
66 Sealer (015 combination)
°83 Liquid vegetable products
20 Specialized cargo/009 Container
3 LASH, Barge carrier
8 Cement
010 Chemicals (solids)
006 Container (cellular)
012 Container (cellular)
18 Dock ship 023 Fish carrier 037 Landing 040 Livestock
47 Pallet, package
060/061 Refrigerated, part/full
84 Roll-on/Roll-off, vehicles, including movable car decks
063 Salt
9 Side loading
°83 Liquid vegetable products
85 Wood, wood products
1Q0 Passenger 082 Troopship
004 Ferry °°9 Chain
0^5 Island-communications ®49 Passenger day excursion
48 Passenger (1-12 berths) f^8 Rail vehicles, Ro-Ro °84 Road vehicles, Ro-Ro
2°0 Bulk °°8 Cement Coal 045 Oil
^6 Strengthened for ore
300 Gas Carrier
°°2 Atmospheric (0-10 psi)
^ Liquid gas
°54 Pressurized (more than 10 psi)
^0 Refrigerated
°*> Tanker ^5 Oil Storage
®03 Specialized Tanker
0Ozf •
4 Bitumen, asphalt, tar Chemicals
^ Molasses
44 Naval replenishment
45 Oil
86 Water 089 Wine
400 Tug 001 Articulated
22 Firefighting 056 Pusher 064 Salvage
3 Fishing
024 Fishing vessel (other than trawler) 066 Sealer
069 Side fishing/trawling 071 Stern fishing/trawling 080 Trawler
088 Whaler, whale-catcher 050 Icebreaker 040 Factory
23 Fish factory
87 Whale/whale oil factory
21 Factory, other
600 Survey and Research
95 Hydrographic
96 Weather
97 Oceanographic 006 Special Service 006 Cable
013 Crane
15 Debris collector
16 Depot, mother 018 Dock ship 020 Drilling
22 Firefighting 029 Grain elevator 033 Hospital, health
38 Launch
39 Lightship
042 Moorings and buoy tenders
50 Patrol
51 Pilot
52 Pipelayer
53 Pontoon
057 Radio (broadcasting)
062 Rockbreaker 064 Salvage, repair
67 Sheerlegs
68 Sludge, sewage carrier 070 Steam-supply
072 Storage, stores
74 Supply
75 Tender 079 Training 081 Trials
070 Naval 050 Patrol 072 Stores 074 Supply 079 Training
81 Trials
82 Troops
007 Great Laker 046 Ore strengthened
060 Dredger 005 Bucket 014 Cutter 017 Dipper
19 Drag 028 Grab
36 Jet 059 Rake
062 Rock-breaker 073 Suction
001 Barge 001 Articulated
20 Drilling 053 Flat
031 Hinged centerline
37 Landing 043 Munitions 045 Oil
094 Oil reclamation 052 Pipelayer 064 Salvage, repair
67 Sheerleg
68 Sludge
070 Steam supply 072 Storage 077 Tipping 086 Water
700 Sail 079 Training 102 Barkentine 105 Schooner 002 Yacht 105 Schooner
Initial breakdown: Rig
020 Drilling
110 Semi-submersible
For general application
027 General cargo space
060/061 Part/fully refrigerated
049 Passengers (1-12 berths)
The user concerned with less than the whole world fleet may limit sub-type codes to two digits if that range of codes will meet his requirements.