TYPE 82 GUIDED MISSILE DESTROYER

COMMANDER D. G. GREAVES, R.N., C.ENG.

Historical A brief history of the events which led up to the current machinery instal-

lation design and some explanation to indicate why a destroyer design should be allocated a Type number normally reserved for frigate designs may be of

some interest. Commencing with the Whitby and Blackwood Class frigates, to which Type numbers 12 and 14 respectively were allocated, all later steam machinery New Designs and Converted frigates were sequentially numbered. Similarly, new series of Type numbers 41 and 61 were raised for the Diesel engined frigates and a further series, commencing at 81, for COSAG engined frigates, the first being the Tribal Class.

A ship design study was initiated by Director-General Ships in April, 1961, for a frigate design to eventually replace the highly successful WhitbylRothesayl Leanderllmproved Leander vessels, this frigate to be equipped with C F 299, a new surveillance radar, among other weapons, and the propelling machinery to be selected by the Marine Engineering Directorate. During this stage the design was known variously as the 'CF 299 Frigate' or 'New Frigate', until a Draft Staff Requirement published on 8th March, 1963, introduced the term 'Post Leander Frigate'.

Co~nplementary to the Ship Design Study, the Project Group of the Marine Engineering Directorate prepared a plant evaluation report published in June, 1962, as a result of which a feasibility study was undertaken by that same group to investigate in more detail the following types of machinery installation :

(i) Steam (ii) COSAG, based upon the Y. 1 l 1 A design (iii) Gas turbines (iv) Diesel

The Feasibility Study Report was finally published in July, 1963, by which time the design had become known as the SIGS Frigate (Small Improved Guidance System). D.M.E. accepted the recommendation of this report to the effect that an all-steam machinery installation design be selected as the pro- pelling machinery and in April, 1963, a contract was placed with the Yarrow- Admiralty Research Department to prepare the Guidance Drawings and Part 1V Machinery Specification for a single-skin frigate design, i.e., no double bottoms, of 45 ft beam and 91 ft total main machinery space length, developing 40,000 s.h.p. It was at this stage that the D.M.E. New Design Destroyer Section was invested with the responsibility of developing up the basic design into a ship installation including supervising the preparation of the Specifications

and Guidance Drawings. It was also at this time that the Type numbzr of 82 was allocated to this particular design of G.P. frigate.

By October, 1963, when the 'Staff Requirements for Type 82 General Purpose Frigate' were published, the beam had been, of necessity, increased to 50 ft and the displacement accordingly by hull and wzapon design development. Already the power requirements neczssary to meet the specified performance were rapidly extending beyond those upon which the machinery design had been based.

As it had become obvious that even at this stage of the design the proverbial quart was materializing, it was considered essential to re-appraise the complete ship and machinery design. In January, 1964, as a result of this detailed examination, a number of decisions were promulgated which meant, for the Marine Engineering Directorate, a 'back to the drawing board' approach to the machinery design. Those which affected the machinery in particular were:

(a) Propelling machinery to be combined steam and gas (COSAG) (b) Beam to be increased to 52 ft (C) Increase in displacement necessitating a further proportionate increase

in the s.h.p. required (d) Double-bottom hull construction to be utilized.

All of these had considerable repercussions on the design, not the least b2ing the last item (d) which resulted in the loss of the full tank depth to the height available for the machinery installation and a considerable loss of beam, external double-bottom tanks being frowned upon by naval conrtructors. A rapid re-examination of the machinery design was essential in order to provide sufficient support to the Naval Construction Directorate in submitting the Sketch Design to the Board, and a machinery space length of 114 ft, based more on County Class experience than the actual design to be installed, was agreed.

The description 'Type 82 Escort' appeared in July, 1964, and was established in August, 1964, by the publication of 'Staff Requirements for Type 82 General Purpose Escort'. At the same time the beam was further increased to 54 ft as a result of detailed development of the Building Drawings, and 'Destroyzr' category had bzen firmly perpetuated by March, 1965.

No further alterations to the Class title have k e n suggested, equilibrium having been achieved with 'Typc 82 Guided Missile Destroyer'.

Machinery Layout The layout of the main machinery spaces follows very much upon that of the

County Class G.M.D.s with the exception that a single combined machinery control room is provided within the Ship Control Complex. FIG. 2 shows the one-twelfth scale model of the main machinery spaces, constructed by Y-A.R.D. From forward to aft the main machinery compartments are as follows :-

( a ) The boiler room containins two main boilers, follows the boxed-boiler concept and is of similar s ~ z z to that provided in the County Class.

(h) The steam turbine room which contains both shaft sets of main steam turbines, the steam turbo alternators, distilling machinery and all steam plant auxiliaries with the exception of the main bailer blowers. This compartment is similar in size to that for the County Class but with the added advantage that the space originally occupied by the control room is now available.

( c ) The two sets of main gearing are fitted into a gearing room similar to the County Class, together with the lubricating oil system and othisr auxiliaries.

FIG. &-SCALE MODEL OF M A C H I N E R Y COMPARTMENTS

(d) The gas turbine room in which the two Olympus gas turbines and their associated auxiliaries are situated is shorter than the Courzty Class by the length originally occupied by the gas turbine control room and Dieso working space. The Olympus gas generators are enclosed in an acoustically lagged compartment of sufficient size to provide access for maintenance and to permit rapid replacement of the complete unit Two of the three 1,000 kW Paxman Ventura Diesel generators are also installed in this compartment.

The air-conditioning machinery, refrigeration plant, motor-driven fire pumps and Biogest plants are distributed throughout the length of the ship in eight auxiliary machinery spaces. Two spaces immediately forward and aft of the main machinery spaces also contain the main boiler fuel and Dieso working spaces respectively. The general arrangement of engineering compart- ments within the ship is shown in FIG. 3.

Selection of Main Propulsion Machinery Following the re-appraisal of the ship design in January, 1964, it became

obvious that the machinery would be required to develop approximately the same power as at present provided by the County Class. Emphasis was placed on providing a set of main machinery of proved reliability which would also be compatible with the requirements of high density, low weight, economical fuel consumption, low initial and running costs, and th3 ability to leave harbour or anchorage at short notice. An r.11-Diesel installation for this power was rejected on the grounds of lack of availability of a grovzd engine. The design would have had to be baszd upon the use of the Ruston A 0 V16 e n ~ i n e which at that time was still in the development stage. In view of the imltipllcity of engines required, the design of the main gearing and control systems would,

SPARE C E A R

STEERING G E A R C O L D A N = S W I T C H B O A R E A U X I L I A R Y N A V A L C O M P A R T M E N T C O O L R O O M S M A C H I N E R Y STORES

C O M P A R T M E h T SPACE N o 3

S W I T C H B O A R Q U P T A K E S A U X I L I A R Y A U X I L I A R Y SPARE M A C H I N E R Y M A C H I N E R Y C E A R SPACE N o 2 SPACE N o I

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M A C H I N E R Y G ~ A R S W I T C H B O A R G S R O O M R O O M C O M P A R T M E N T R O O M C O M P A R T M E N T SPARE G E A R S P A C E N o 8 ' ( U N D E R )

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A U X I L I A R Y S P A R E A U X I L I A R Y G T U P T A K E S S H I P E R U M A C H I N E C L E A N B O I L E R A U X I L I A R Y A U X I L I A R Y M A C H I N E R Y G E A R M A C H I N E R Y C O N T R O L STORE F I T T I N G F I T T I N G U P T A K E S M A C H I N E R Y M A C H I N E R Y S P A C E N O 7 S T O R E S P A C E N o 6 C E N T R E S H O P S H O P SPACE N o 2 ;SPACE N o l

GLAND A' AUXILIAR; A U X I L I A R Y G A S C O M P A R T M E N T S M A C H I N E R Y M A C H I N E R Y T U R B I N E G E A R I N G

S P A C E ~ ~ . 5 S P A C E N o . 4 R O O M R O O M

S T E A M T U R B I N E

R O O M

A U X l L l A R Y BOILER M A C H 1 N E R Y N A V A L S P A R E CEAR

R O O M S P A C E N o 3 S T O R E S S T O R E

FIG. 3-ARRANGEMENT OF ENGINEERING COMPARTMENTS

in addition, have imposed the necessity for extensive development which the ship design and building programme did not permit.

An all-steam plant for the specified s.h.p. would have required a completely new design of boiler, steam turbine and main gearing, all of which would need to be thoroughly shore-tested. Within the time-scale available it would only be possible to shore-test the new boiler design and carry out a back-to- back test of the main gearing. The facility for rapidly getting under way could only be provided by remaining flashed-up in harbour with consequential demands for additional watchkeeping. It was considered therefore that the risk of installing an unproved set of main steam machinery as the sole propelling plant was also unacceptable.

The all-gas-turbine plant was an attractive proposition emotionally. The Marine Engineering Directorate at this time had reached the stage, however, of deciding to use to advantage the enormous financial investment and exten- sive operational experience in aircraft type light-weight gas turbines, rather than expending naval resources in developing special marine versions. The Bristol Siddeley Olympus engine with its power potential of more than 20,000 s.h.p. was the favourite contender, but in view of the unproved performance and reliability under marine conditions of aircraft gas turbines in general, and the Olympus in particular, there was no great enthusiasm within the Ship Department to commit the entire propulsion system to this unit. In addition, it was felt that development over the next two or three years would no doubt provide an entirely satisfactory design, but not in time to meet the Type 82 time-scale. To achieve the specified endurance under cruising conditions, would have required a greater all-up weight than the all-steam or COSAG designs with consequent addition to the running costs. Furthermore, the only suitable generators available for a non-steam ship were Diesels and use of these at sea and in harbour would increase the maintenance load. In view of the similarity between the Type 82 and the County Class destroyers which made possible the use of existing machinery units, thus providing reliability to a greater extent than is normally possible in a new design, and a need to provide the means of achieving a rapid get-away, the choice fell upon the COSAG arrangement. This decision was strongly supported by the ship operators in the light of their experience with the County and Tribal Class vessels. The arguments that a combination of steam and gas machinery would cause difficulties in maintenance, spares support and machinery control, together with high capital cost, are considered in the case of the Type 82 to be more than offset by the ability to incorporate machinery currently in service in the County Class. Such a policy brings in its train a considerable number of advantages to both the operator and the designer including known reliability (or unreliability which can be designed out), utilization of present holdings of spare gear and depot spare units and of existing maintenance facilities and instructions. Furthermore, the need for prototype design and testing is elimi- nated and the very important factor of operator familiarity maintained. Higher availability is achieved as a bonus by virtue of the fact that one element of the combined plant can be maintained at sea while proceeding on the other and, in harbour, the ship can be retained at short notice on the gas plant without interfering with maintenance of the steam plant.

Main Boilers These are the single-furnace type fitted with economizer, superheater and

superheat control similar to the County Class design. In the light of the diffi- culties that have been experienced a t sea with this design, every effort has been made to eliminate the operational and maintenance shortcomings, particularly with regard to reduction of superheater efficiency, due to choking

of the gas paths. The superheater design is based on that of the Assault ship boilers and now provides a walk-in space between the hairpin tubes. The tube pitching has been modified to permit the insertion of water-washing lances through the gas lanes, which was not possible with the previous staggered pitch tubes; any slight reduction in heat transfer efficiency being absorbed by design margins. Doors to the superheater will be hinged to allow simple access for cleaning the tube ends adjacent to the drums, and standard taper lip hand- hole plugs will be fitted. Rack type retractable soot blowers, one for the super- heated and one for the saturated pass, will be installed in addition to the normal outfit of soot blowers. Advantage has also been taken during the re-design to incorporate a number of improvements generally. The diameter of the steam drum will be increased by 6 inches to 54 inches to improve both steamlwater separation and access to the drum internal gear, and an additional screen header drum results from the new boiler geometry. Raising the design pressure by a small margin will allow the safety valves to b: set well clear of the steaming pressure and avoid 'popping' during normal manceuvring. Some re-design of the boiler casings to provide the degree of blast protection now considered necessary is required. Other minor but no less important modifications include a furnace flame-out indicator, a hinged water-drum manhole to prevent damage to the simmering coil, and a re- allocation of safety valves now provides two on the steam drum and only one on the superheater.

Steam Turbines To reduce the congestion within the steam turbine room, it was decided t o - %

instruct A.E.I. to prepare a new single-cylinder design of steam turbine incor- porating an astern turbine at the exhaust end of the ahead turbine, utilizing the experience of the G.P. frigate and the County Class turbines. Ahead control is achieved by the use of four sequentially operated nozzle valves of the single- seated Venturi type and astern control of the two-row velocity-compounded Curtis stage and single impulse stage by a single astern manoeuvring valve. '

An over-speed governor is provided to close the main steam turbine guarding ' valve when the rotor speed in the ahead or astern direction reaches 110 per cent of the design speed. In the interest of reducing underwater noise and machinery wear, provision is made for balancing the turbine rotor iil situ without the need to obtain access to the steam spaces. The main condenser is of the single-pass surface regenerative type, with tubes rolled into the tube plates 2t both ends and the closed-feed controller contained within the sump. The cause of the main bearing wear in the current design County Class rotor is still under active investigation, although the rate of barring appears t o have a significant effect. Consequently, barring speeds in the Type 82 design have been increased to achieve a rotor speed of 10 r.p.m.

Main Gearing The main gearing design by Associated Electrical Industries follows, very

closely upon that for the County Class with the exception that only single steam and gas turbine drives are required on each shaft. This has necessitated some re-design of the hydraulic couplings and automatic synchronizing clutches which now have to transmit the full gas turbine output through a single unit, and the provision of larger quantities of lubricating/cooling oil to the couplings. Manually operated clutches are provided for disconnecting the steam turbines and for selecting boost or manaeuvring drive. To enable the gearbox to be readily converted from manual to automatic selection of the mode of gas turbine drive, thus avoiding the necessity to stop the ship, provision has been made to replace the boost-drive manual clutch with an inverted automatic

v: 4 * A<&&' FIG 4-GAS TURBINE UNIT IN ASSEMBLY SHOP

(Courtesy of Bristol Siddeley Engines, Ltd.)

synchronizing clutch and to fit a transient disc brake to its input shaft. Drive from the steam and gas turbines is by means of torque tubes and flexible couplings of the diaphragm type.

Gas Turbines The Bristol Siddeley Marine Olympus gas turbine power unit with a capa-

bility in excess of 20,000 s.h.p. has been selected for the gas turbine drive unit. The gas generator unit consists of a marinized version of the Olympus 201 gas generator which has been in service with the Royal Air Force since 1956 and accumulated over 300,000 running hours. It has a minimum overhaul life of 3,000 hours. The marinized engine, known as the Type BS 2109/10, is a straight flow, high pressure ratio unit with a five-stage low pressure compressor and a seven-stage high pressure compressor, each driven by its own single-stage turbine. The two compressor-turbine units, with their coaxial shafts, are mechanically independent. Gear-driven accessories, such as fuel and lubricating oil pumps, are mounted on an intermediate casing between the two compressors. Due to the close proximity of the Diesel generators, it has been considered advisable to provide continuous barring motors to avoid possible brinelling of the gas generator bearings which are all of ball or roller type.

The power turbine, Type TM l (FIG. 4), is of robust design with an overall life similar to that for the steam turbines. It is a single-stage light-weight design using plain journal bearings and connected to the gas generator simply by means of a flexible gas duct, thus avoiding alignment problems. The bearings are lubricated by an oil supply from the main gearing and steam turbine system, and itz situ balancing facilities, without the need to penetrate the gas spaces, are provided.

FIG. 5-MAIN CEARCASE VERTICAL CPMS

The gas generator is cantilevered off the face of the power turbine by mzans of a tubular support frame, the advantages of which are two-fold:

(i) To reduce the shock received by the gas generator by taking advantage of the power turbine and mounting weights, and

(ii) To provide ready access to the engine and its auxiliaries for routine maintenance purposes. The support frames are designed to swing free to facilitate engine replacement.

Main Machinery Mounting System Analysis of the underwater noise signature of previous COSAG machinery

installations indicated that considerably more effort was required to reduce the noise transmitted from the gas turbines and the main gearing, while that from the main steam turbine was probably acceptable. A mounting system developed by Y-A.R.D. and known as the Constant Position Mounting System (C.P.M.S.) supports the selected machinery units on a number of capsules, each capsule being positioned by regulation of hydraulic fluid pressure from a motor-driven pumping unit against a diaphragm, loaded pneumatically, as dictated by a positioning valve. Accuracy of positioning to 0.004 in. with a working range of 0-030 in. is achieved. To ensure complete isolation from the hull, vertical, athwartship and fore and aft positioning units are required. Three-point vertical support, to avoid stressing the unit's sub-frame, is normally provided. In the Type 82 machinery installation, the Olympus power turbine, and hence the gas generator which it supports, is mounted on a constant position mounting system as is the main gearing. In the case of the latter unit, if complete isolation is to be achieved the main thrust must be transmitted to the hull through these capsules and a main shaft noise isolating coupling fitted. The problem of providing simple replacement routes for the C.P.M.S. capsules and for their day-to-day maintenance was further complicated by

the need to provide a system of shock chocks for the main gearing which is normally designed to withstand maximum shock without additional protec- tion, and shock mountings for the gas turbine, which is not. The C.P.M.S. capsules themselves, while able to withstand the full shock application, provide no attenuation.

It was considered necessary to investigate this problem in advance of selection of the ~ n a i n machinery contractor affecting, as it did, the main seatings and hull structure. A full-scale wooden mock-up of the gearcase base and seating has been constructed by Y-A.R.D. and dummy capsules ballasted to the true weight were used to simulate maintenance and renewal routines. As a result, a number of modifications were found to be desirable but on the whole the proposed arrangement proved to be surprisingly satisfactory. Special lifting gear and transporting arrangements are also being developed on this mock-up. The mock-up of the gearcase vertical inboard mounts are shown in FIG. 5. The C.P.M.S. for the gas turbine units will be tested during the course of the shore trials at Bristol Siddeley Engines Ltd., which are described separately.

The problem of driving from one fixed and one floating prime mover on to an hydraulically mounted gearcase in both the working and the failed position presents no problems which cannot b: solved by standard proved flexible couplings, but the design of large-bore pipe systems may tease for a time. A diagrammatic arrangement for the gas turbine machinery is shown in FIG. 6.

Steam Plant Auxiliaries The duties of the main steam plant for both the Type 82 and the County

Class designs bzing similar, and following the principle of using existing designs, the first choice of auxiliary unit was that already fitted in the latter ships. The basic concept was to evaluate the performance and reliability of these units, to use those which were entirely satisfactory in an unmodified form and to eradicate in the Order and Manufacturing stage known defects and short- comings in the others. Overriding this basis was the requirement to incorporate any substantially advantageous design features and principles which had been developed subsequent to the design of the County Class machinery. The alter- native approach was to seek new designs of auxiliaries, accepting the additional prohibitive headquarters and industrial work-load involved in design testing, book-writing, spare gear provisioning and training with no guarantee that the new unit would be any more reliable than that which it replaced. To assist in compiling a comprehensive history of each machine, the Ship Maintenance Authority was requested to advise on reliability as indicated from the defect reports from sea, categorizing each machine as either:

(a) Black-numerous defects reported (6) Grey-moderate number of defects reported ( c ) White-few or no defects reported.

The only major items which seemed to have a clean bill of health and which could be repeated without modification were the Diesel air compressor, boiler combustion equipment, the auxiliary boiler and the stripping pumps. By far the greater proportion required some modification to design by reason of proved unreliability, maintenance difficulties, alterations in duties or simpli- fication of the machinery arrangement. This group included units such as the gear-driven forced lubrication pump, the turbo and motor-driven extraction pumps, the deaerator and its extraction pump, H.P. and servo air compressors and main boiler blowers. In the majority of cases some slight re-design only was required whereas in others, e.g., the H.P. air compressor, something more extensive was essential.

G L A C I E R DU '0; P T E

M O U L D E D R U B B E R

O L Y M P U S ' F A C E D BRONZE F R A M E

B A C K E D P A D S

B U T Y L B O O T

J U B I L E E C l I P . -

A I R SUPPLY

FIG. 6-D~AGRAMMATIC ARRANGEMENT OF CONSTANT POS~TIONING MOUNTING SYSTEM

A third category of items entirely different from those fitted in the County Class includes the following:

(a) Motor-driven main forced lubrication pump-A Drysdale positive rotary pump replaces the centrifugal design to avoid suspected incompatibility with the positive displacement pump which occurs at certain shaft speeds resulting in reduced forced lubrication main pressure and, in extreme cases, 'cutting-in7 of the stand-by pump.

(b) Air ejector and gland vapour condenser-These have now been combined into a common unit.

( c ) Main feed pump-It is now D.M.E. policy to fit turbine-driven water- lubricated feed pumps with consequential saving of space, simplification of maintenance and elimination of lubricating oil problems.

(d ) Auxiliary circulatitig, lubricating oil cooler, 0. M.S. Diesei generator a r ~ d ventilation cooler pumps-The existing County Class pumps do not meet the specified duties of the new design.

( e ) Main -fuel pumps-A new design of pump was essential to meet the specified ability to achieve full power on the steam plant burning either F.F.O. or Dieso, with a supplementary requirement to pump Avcat at reduced powers in an emergency. The prototype now under development by G. & J. Weir is unfortunately a compromise design and, like most compromises, is not a thing of beauty. It is expected, however, that the close attention of maintainers, designers and operators, together with prototype testing a t the A.F.E.S., will produce a reliable and easily maintainable compromise.

(J) Distilling plant-Again, in accordance with D.M.E. policy, a two-stage flash plant to Buckley and Taylor design has been selected to take advantage of the simplified operation and improved stability. Such a radical change also requires a new design pumping unit which will be shore-tested at the A.D.E.S. during prototype trials. - - -

( g ) Auxiliary lubricatitig oil systenl-Evidence is accumulating to the effect that the use of OEP 69 lubricating oil in geared auxiliary machinery can result in lacquering of bearing surfaces and failure of overspeed trip mechanisms. Auxiliaries operated on OM 100 do not appear to suffer from these effects. Tn view of the necessity to continue to operate modern main gears on OEP 69, a separate geared auxiliary lubricating oil system has been provided in this design with separate storage and renovating facilities to avoid any possibility of cross-contamination.

Electrical Power Generation The Type 82 has not avoided the continuing escalation of power demands

by the apparently insatiable highly sophisticated modern weapon systems. A total of 7 MW of power is provided compared with 3-65 MW in the County Class. This requirement is met by two steam-driven geared design main generators each of 2,000 kW and three 1,000 kW Diesel-driven Paxman Ventura generators.

The steam turbo generators which are being manufactured by A.E.I. are of a new design selected by competitive design and tender exercise and are installed in the steam turbine room. A machine of this capacity requires relatively large auxiliaries which it was thought inadvisable to drive from the prime mover. Consequently, it has been necessary to install separate motor- driven auxiliaries with the additional installation problems that this implies. Facilities for inspection of nozzles and blading without the need for dismantling and for in situ balancing are included in the design. Efforts to make the unit completely self-sustaining have been unrewarding due to two major difficulties: firstly, the problem of designing the glands for sealing by superheated steam or, alternatively, providing a simple and reliable desuperheater; and secondly, the unacceptability of providing power for the motor-driven auxiliaries from upstream of the main supply breaker. The Electrical Engineering Directorate maintains that the alternator must be protected against an insulation failure of any auxiliary by this breaker.

The selection of three identical Diesel generators simplifies the spares and maintenance problem and the design intention is that all three machines should be operated in sequence to provide power in harbour and when on 'gas only' drive. To meet the specified provision of an emergency/salvage generator, one unit is installed in the after superstructure complete with its own switchboard and circulating pump. All three machines can be started remotely from the machinery control room to provide instantaneous stand-by.

Air-Conditioning Machinery Largely due to the increased demands of the weapon systems, the Type 82

has an installed air-conditioning plant capacity of 7.2 million BTU/hour compared to 3 million in the County Class. Following the principle of utilizing existing machinery it is the intention to fit eight in number 900,000 BTU/hour Hall's plants, similar to those in the County Class, any six of which would meet the estimated maximum load requirement. The design of the chilled-water rlng main is providing some difficult problems in attempting to meet what are apparently two incompatible requirements: the ability to simply manipulate the main section isolating valves to permutate any six out of eight plants, and the desirability to run as few plants as possible compatible with the ship load. Some re-design work on the Hall's plants will be necessary but it is the intention to retain interchangeability with similar plants fitted elsewhere.

Machinery Control Following the recommendations of the SURlC Committee on ship control,

the compartment immediately above the gearing room has been nominated as the Ship Control Centre. This Centre contains the machinery control console, the main switchboard primary control console, the damage control head- quarters (including the ship safety centre) and, within a separate enclosure, the secondary steering position. The advantage of achieving close co-ordination between the technical departments of the ship under operating conditions, without the need to resort to telephonic aids, is obvious. The fear that this Centre may be transformed into a Tower of Babe1 under Action conditions, distracting machinery operators at a time when extra concentration is required, is a very real problem. With this in mind, the compartment has been arranged in such a way that a noise-insulating bulkhead can be erected between the machinery control console and the damage control centre should this be considered necessary at a later stage of the design.

Secondary machinery control positions are provided in the steam and gas turbine rooms for use in the event of a Ship Control Centre disaster with, in addition, less sophisticated control of power and shaft direction at the prime movers themselves and at the gearcase for use if a complete control power failure occurs.

Machinery control is basically pneumatic as in previous designs, primarily to consolidate present knowledge and training facilities and to sustain operator 'know-how'. Due to the single control room concept the complete console has been re-designed from first principles, taking into account the study carried out by Fleet Work Study Team No. 18 and experience at sea. Automatic control systems which are known to be unreliable in the County Class, e.g., the forced lubricating oil temperature control and the closed exhaust pressure control, are to be re-designed completely, whereas reliable systems, e.g., the main boiler combustion control, are to be retained practically unmodified. An additional system of automatic shaft-speed control, which is designed to simplify the work of the throttle watchkeepers, is under development and will eventually be fitted. Bridge control of machinery, however, is not contemplated. It has also been decided that insufficient is known about the application of Machinery Information Systems to naval installations to warrant fitting in this design. Such a system would have included data logging, alarm, print out of selected parameners at regular intervals and memory facilities, relieving the watchkeepers of some of their more routine duties. The transfer of responsi- bility for noting unusual and possibly dangerous readings from the watchkeeper to a black box has not yet been accepted in principle by D.M.E.

Overhaul by Replacement The policy of overhaul by replacement may be described as requiring not

only the complete machine to be designed for replacement at regular main- tenance intervals (or earlier if a failure occurs), but also the provision within the ship design of the necessary facilities for carrying out this task with the least disturbance to other machines and structure. It also implies that adequate repair facilities are available to provide a regular supply of refitted equipment with a minimum of stocks. Design aims in order to implement this policy have been defined as follows :

(a) Space round the various items of machinery to enable convenient access to seatings and to pipe and other connections to the systems of which they form a part.

(h ) Easy disconnection and easy slinging; fixed gantries and rails are convenient but not, in general, essential, except in those locations where ordinary slinging gear cannot be used. The design of the machine must also lend itself to convenience of slinging.

(c) A reasonably uncongested route to the point from which the machine is removed from the compartment. Ideally, no consequential removal of other equipment, pipes, etc., should be necessary, albeit this is not fully practicable in a warship. On the other hand, it is essential that vital machinery should not be immobilized just because something else is being removed.

(d ) A removal path from the machinery spaces to the upper deck. The ideal is a trunk large enough to take the largest item of machinery that has to be removed as a single unit and which is unobstructed except by easily portable equipment, such as ladders. If a trunk cannot be provided, in-line hatches of the requisite size may suffice, provided that the ship's domestic arrangements were not reduced to chaos every time the route is used. The aim should be to enable a crane to plumb right down into the machinery spaces.

These aims will be kept well to the fore during the detailed design period, tempered, as always, by other ship design requirements. Auxiliary machinery removal trunks with a clear path 6 ft X 5 ft have been specified from the crown of the steam turbine room and gearing room straight to the upper deck where removable plates will be provided. To avoid wasting space in highly desirabIe locations, these trunks are normally part of the machinery space ventilation system. Removal of auxiliary machinery from the gas turbine room will be through portable sections of the Olympus gas turbine intake trunks, again with access direct to the upper deck. The layout of machinery within the compart- ments will be arranged to provide removal lanes to the machinery removal trunks and arrangements will be checked on the full-scale mock-up.

Machinery removal trunks for the eight auxiliary machinery spaces is not a practicable proposition in a tight ship design such as the Type 82. It has therefore been necessary to investigate the provision of a vertical line of hatches up to the main fore-and-aft gangway and transporting arrangements to the nearest weather-deck door.

As the Olympus gas generator has an overhaul life similar to the auxiliary machinery, it must also be capable of simple replacement-a target of 24 hours being set for an engine change. Removal is effected via the intake trunk and plenum chamber, the weight being supported by a specially designed trans- porting trolley and a system of fixed and portable guide rails. In view of the importance attached to guaranteeing this operation, Y-A.R.D. constructed a full-size mock-up at their works to check the design of lifting gear and rails

FIG. ~ - R E ~ I O V A L OF GAS GENERATOR

(a) AIR DOWNTAKE, PLENUM CHAMBER AND ACOUSTIC ENCLOSLJRE, P o R r s l n t

(6) TRANSPORT TROLLEY AND LIFTING COLUMNS IN POSITION

(C) OLYMPUS (PORT SIDE) ENrERlNG AIR DOWNTAKE

(d) OLYMPUS (PORT SIDE) APPROACHING THE VERTICAL SECTION OF THk AIR U O W h T A K t

( P ) OLYMPUS (PORT SIDE) I N PI-ENUM CHAMBER WITH GUIDE RAILS FITTED

(fj OLYMPUS (PORT SIDE) AT M A X I M U M CRANE LIFT POSITION

and to confirm the estimated dimensions of the intake trunk of approximately 9 ft X 6 - 5 ft. The passage of the engine from its acoustic chamber to the top of the air intake trunk is shown in FIG. 7.

Mock-Ups Apart from the main gearing seating and Olympus removal previously

mentioned, it is the intention to build a full-scale mock-up of the starboard side of the main machinery spaces, including the Ship Control Centre. extending 6 ft into the port side. The detailed arrangement of auxiliary machinery and the design of all systems will be finalized and the working drawings prepared at the mock-up prior to commencing installation in the ship. The appropriate maintenance authorities will be consulted before approval of any particular arrangement, maintenance exercises being simulated a t the mock-up as may be considered necessary. Unfortunately, M.O.D. (N) policy to undertake a competitive exercise, even for a First of Class design, precluded the nomination of a Leading Main Machinery Contractor and, due to the delays resulting from the Defence Review, the first Type 82 is now pro- grammed to complete in approximately the same time as it takes to build a follow-on County Class G.M.D. Provided pressure is kept up on the Main Machinery Contractor to follow the principle of designing in the mock-up and not in the ship and of obtaining approval a t the former before installation in the latter, it is still considered that the mock-up can provide invaluable guidance and not simply be a copy of the ship installation as has frequently occurred in the past.

Ordering of Machinery Machinery for ships under construction in commercial shipyards may be

ordered in several different ways. Responsibility for the timely ordering and delivery of the bulk of the mechanical engineering machinery to meet his programme is normally firmly placed with the Main Machinery Contractor. Certain other items which are expected to retain a fair amount of outstanding design work at the time of ordering the ship, and machines which are pool items, e.g., standard designs of Diesel generators, are nominated as Admiralty Supply Items. Recently, a third category has become necessary-the Long Lead Item-brought about by the greater sophistication of modern designs of machinery and the extended deliveries which are now to be expected from most manufacturers. In the present machinery design, the main steam turbines, condensers, boiler pressure parts and the main gearing were ordered approxi- mately 18 months ahead of the ship, and the steam turbo alternators some 14 months. At one time, just before the publication of the Defence Review, it looked as though we would have a set of machinery but no ship! The turbo blowers, evaporators, air conditioning plant, main boiler fuel pumps and air compressors have also been ordered well in advance of the ship to meet the building programme. With the exception of the main boiler fuel pumps, all Long Lead items become the Main Machinery Contractor's responsibility when the ship contract is placed.

Shore Trials As the main propulsion steam turbines, boilers and gearing utilize the basic

design features of existing machinery, it was considered that the expense and time required to shore-test these units was not warranted, but testing of individual components, such as the modified design of the fluid coupling, is being undertaken where it is considered that design information is insufficiently firm.

The Olympus power turbine is of new design but, although following the principles of a similar land-based turbine, prudence dictated that the build of the first gas turbine plant as a whole be proved ashore. Bristol Siddley Engines have therefore been contracted to install and test an Olympus gas generator and power turbine plant, complete with the ship type engine starting system, control and indication console, mounted as in the ship on constant position mountings and driving on to a pair of Heenan and Froude high-speed water brakes. Apart from proving the build, it is also the intention to obtain accurate performance figures, to check the proposed design of the intake plenum chamber, to measure the noise spectrum and to check the performance of the C.P.M. system. This series of trials is planned to commence in the autumn of 1966, continuing for approximately 300 hours7 running time.

The only other major units considered to warrant shore testing are the 2,000 kW steam turbo alternators. Being of new design, these machines will be subjected to an intensive test programme to be carried out at a selected venue, the alternator output having stripped the works' test facilities now available.

The degree of type testing to be applied to the auxiliary machinery is currently under review and, to date, full prototype testing has bcen approved for the distilling machinery, the L.P. air compressor, the boiler fuel pump and the main boiler blower.

Note: This article was written at the stage when the Part IV Machinery Specification

had been completed and the Guidance Drawings issued but the contract for the first destroyer had yet to be placed. It therefore describes the specified design, not the finally approved installation, and as the Main Machinery Contractor develops the detailed installation design, no doubt certain philosophies will have to be modified and with them the machinery design itself.