TECHNICAL PROGRESS IN MARINE ENGINEERING DURING 1962

THE SHIPBUILDER AND MARINE ENGINE BUILDER

MARliW ENGINEERING DURllVG 1962

ACKNOWLEDGMENT

This staf article is reprinted from the January 1963 issue of “The Ship- builder and Marine Engine Builder.”

AUTOMATION

THE INTEREST IN automatic operation of ships and in particular of ships’ machinery, both steam and Diesel, has increased during the year, being stim- ulated by the diffculties of maintaining fully quali- fied crews and of their cost as an increasing pro- portion of a ship’s total outgoings. Owners in many countries are showing a practical interest, in particular in America, Japan, Russia and Sweden.

In the United States of America a paper C11 was read before S.N.A.M.E. in which the operation of a C-4 Mariner dry-cargo ship is considered with sufficient automation to reduce the present complement of 55 to 14 for a steam turbine vessel (and to 12 for gas turbine machinery). A period of 30 days at sea with no maintenance is designed for, and for 90 days with only minor maintenance, human inter- vention being practically confined to monitoring and mition fixing. The author of paper C2l subdivided the subject into automatic safety and alarm devices, and into mechanization of operations. Proposals are made for the automatic control of much of the plant

both in boiler room and engine-room. Pneumatic controls are favored owing to the advantages of low upkeep costs, absence of fire risk, long life and possibility of air storage for emergency operation. Also described is the Werkspoor medium-pressure, spill- type burner which can operate effectively with turn- down ratio of 1:4. When shut down, the burner is oil cooled and does not need to be withdrawn; it can be remotely controlled by push button and has given some years of trouble-free service in a works boiler and also in a Dutch cruiser. In reference C31, the subject is discussed from the French point of view. The extra cost of part automation spread over ten years appears to be equivalent (in a French ship) to the cost of six or seven members of crew. In addition to the proposals for remote control of machinery, it is suggested that ballasting and maintenance of stability and trim should also be automatically controlled. A typical complement for a medium sized or large cargo ship with semi-automation is given as, the master, chief engineer, chief officer, three navigator-engineer officers for watch keeping, one radioelectronics officer, four technical

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MARINE ENGINEERING IN 1962 THE SHIPBUILDER AND M. E. BUILDEn

ratings, two seamen, and three hotel staff (total of sixteen). In a tanker an extra crew member would be needed for the pumps. Apart from the watchkeepers, all others would normally be on day work.

As distinct from theoretical proposals, many actual installations are making more extended use of automatic controls. Their success will, of course, depend on the reliability of both the main and the auxiliary machinery. The recently reported results of the operation of the B. & W. type machinery of the Yamtomi Maru for 6,546 hours without overhaul is very encouraging, and many Japanese builders are equipping their engine-rooms with a centralized and automatic control system centered in a console housed in a sound proof and vibration proof control room.

The Kinkssan M a r u has a main engine control console on the bridge as well as the one adjoining the engine-room. It is a dry cargo vessel of 8,316 tons, 18.25 knots and the main engines are Mitsui- B. & W. 874 VT.2BF 160 units developing 12,000 B.H.P. at 115 r.p.m. The crew numbers 43, that is, seven less than in other comparable ships-four of the seven being engine-room crew. During the maiden voyage from Japan to New York, 638 main engine meneuvers were effected by remote control, 369 from the control room adjoining the engine- room and 269 from the wheelhouse console. On only three occasions did the main engines fail to start properly at the first attempt.

The Richmond M a r u of 9,547 tons, 21.68 knots and 13,000 B.H.P., has automatic controls extended to the two-stage cleaning of the fuel oil and to the maintenance of constant temperature and flow rate for piston and jacket cooling media. The starting, control and monitoring of the main engine and of the auxiliaris are carried out from the control room. The performance of these and similar vessels will be followed with considerable interest.

The remote control of cargo handling in tankers is a subject dealt with in reference [4]. The first such ships to be equipped were tankers of 35,500 tons deadweight built in 1959, and the specifications for 77,000 and 86,000-ton tankers now building also call for remote hydraulic control of cargo valves. The experience gained with remote hydraulic control is discussed. For complete automation, the stripping system will either require mechanization of its valves or must be integrated with the main cargo system by the development of new stripping techniques. The problems connected with remote control of new techniques of tank cleaning are discussed as are the problems of complete automation of cargo handling and ballast systems.

DIESEL MACHINERY

The large-bore Diesel engine satisfactorily continues to demonstrate its reliability and practically all engine manufacturers can now offer 20,000

B.H.P. per shaft or more. [5, 6, 71 refer respectiveiy to the Gotaverken, the Doxford and the B. & W. engine.

The Gotaverken 760 mm. and 850 mm. bore engines cover the power ranges 6,300-15,000 B.H.P., and 12,600-25,200 B.H.P. The reasons are given for choosing the constant-pressure system of supercharging these engines in preference to the pulse-pressure system. The general features of the constant-pressure turbo-charging system and the scavenging air pumps are described, Engine flow characteristics and the use of a diffuser before the exhaust gas receiver (thus effectively using some of the kinetic energy), and another after the compressor spiral are discussed, and reasons given for using plain bearings in preference to ball bearings in the supercharger. A turbo-charger inspected after 27,000 hours running showed nozzles and blades to be in very good condition. Use of the constant-pressure system permits positioning the turbo-chargers at some distance from the engine and gives more flexibility for engine-room arrangement. The development potential of the constant- pressure system is discussed and two experimental engines have been built to explore the possibility of realizing the higher m.i.p., which is theoretically offered by this system of supercharging.

Operating results of the P type Doxford engine are proving to be satisfactory. Among other items mentioned in [Sl, it is noted that having experi- mented with chromium plated liners, the company now use liners of centrifugally cast iron and rates of wear when using high viscosity fuel are reported to be 0.003 to 0.008 in. per 1,000 hours. Water temperatures are advised to be 150/155 degrees F. inlet and 175/180 degrees F. outlet, but difficulty is ex- perienced in getting watchkeepers to maintain such temperatures, as the engine-room is more comfort- able when they are lower. Reference is made to a new type of lubricator which is being developed.

The more powerful J-type engine is now under construction with 760 mm. bore, 2,180 mm. combined stroke and an m.i.p. of 135 psi and provides up to 20,000 B.H.P. per shaft. Cylinder centers are even closer than on the P-type and nine and ten- cylinder engines can be built with no serious critical speeds in the running range.

In 171 it is shown that the mean cycle temperature and cylinder wall temperatures of the highly supercharged B. & W. engines have not been increased due to the higher rating. With a charging pressure of 10.7 psi, the m.i.p. is 135 psi, the compression pressure is 755 psi, the maximum pressure 925 psi, and oil continues to be used as the piston cooling medium. The design of cylinder liners for poppet- valve engines and for opposed-piston engines is discussed and vanadium cast iron liners are considered to be generally satisfactory as regards wear.

Fuel Znjection With increasing power output per cylinder, con-

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THE SHIPBUILDER AND M. E. BUILDER MARINE ENGINEERING IN 1962

trol of injection becomes more difficult. Many methods have been adopted to overcome this difficulty but among the most elegant and effective is the BICERA fuel-injection system. This system works on the hydraulic accumulator principle re- quiring no excessive or suddenly applied loads, and with only lightly loaded injection control equipment, it can give practically any desired character- istic (including the equivalent of pilot injection), with no valve bounce. Mark I of the equipment was developed in 1960 and now Mark I1 has been developed to bring it nearer the commercial pro- duction stage. In [8] mention is made of modifica- tions to the hydraulically-operated servo valve, servo piston and also to the accumulator which is fitted to each pump-injector. The design of the various components and the layout of the system as a whole can easily be varied to suit different applications.

Matching of Engine Turbo-charger In [91 work is reviewed which has been carried

out on behalf of B.S.R.A. on this subject. The maximum energy available in exhaust gases is expressed in terms of an equivalent engine mean effective pressure (e.m.e.p.) and is a function of the exhaust release pressure and supercharger boost pressure, these in turn depending on scavenge ratio and air/fuel ratio. The exhaust energy availability factor is defined as the ratio of energy available at inlet to the turbine and the maximum energy available in the exhaust gases. The losses at either end of the exhaust pipe, and the effect of pipe size and nozzle area are discussed and published results are reviewed.

A theoretical and experimental investigation into the factors which affect the magnitude of the energy content of exhaust pulses in a turbo-charged two- stroke cycle Diesel engine is the subject of 1101. From a theoretical analysis an expression is obtained for the assessment of the energy content of the exhaust gas and the concept of continuous mean power is derived. The influence of wave action on this continuous mean power is examined using the method of characteristics and it is shown that there is an optimum size of nozzle and of exhaust pipe. The continuous mean power increases with engine speed, release pressure and period of supercharge. The experimental work covered a wide range of the variables and the results agreed qualitatively with the trends predicted by the theoretical analysis.

The author of [lll describes tests carried out to determine the influence of exhaust belt design on the discharge process of the two-stroke cycle Diesel engine. A quantitative assessment of belt design is made from an analysis of discharge time and mass flow rate during blow down. Results are given in the form of tables and curves and recommendations on belt design are given. For a given port geometry, optimum dimensions of belt can be estimated. If

practical difficulties preclude the use of such a belt, the effect of fitting a smaller belt can be ascertained, and it can then be decided whether to modify the original port or not.

Firing Order and Balancing A valuable summary of the effect of firing order

on multi-cylinder, in-line engines is given in C121 and desirable features in the crankshafts of such engines are listed. The number of possible different firing orders in both two and four-stroke cycle engines increases rapidly with the number of cylin- ders, and although many of them are unusable, a great deal of scope remains for exploring alternative arrangements when a compromise is required due to conflicting design requirements. For supercharged engines, particularly those using the pulse system, the efficiency of the system is considerably influenced by firing order and this has to be added to the usual considerations of torsional vibration and internal and external mass balance. In excep- tional cases it may be necessary to accept a crankshaft arrangement which satisfies torsional or mass-balancing requirements but not both, supple- mentary devices are then used to solve the out- standing difficulties.

In connection with the subject of m a s balancing C131 gives an account of a counter balancing device, based on the Lanchester balancing system, which has been developed by the engine builders. It is claimed to be the first of its kind to be fitted to a large marine Diesel. At each end of the engine a pair of pinions, equipped with counter weights and driven at twice engine speed, exert a force on the driving gear wheels through a special spring ten- sioning arrangement. Diagrams illustrate the effect of the system on the balancing characteristics.

Experimental Work on Crankshafts and Pistons A four-stroke cycle V-16 turbo-charged Diesel

engine of 15% in. bore and 22 in. stroke rated at 165 psi b.m.e.p. at 360 r.p.m., has been fitted with strain gauges attached to the crank pin and journal fillets. The leads were threaded through the oil ways and brought out through a mercury pool con- nector to the amplifier and recording circuitry. The instrumentation and results are reported in Cl4l.

From the records, crankpin fillet stresses are plotted against r.p.m. for alternate and consecutive firing. The effect of bearing clearance did not prove to be of major importance. The stresses are found to be high compared with published limiting stresses for crankshafts. The effect of adjacent crank throws is very sigdicant and conventional single throw analysis is not considered adequate to explain the stress in a crankshaft that has adjacent throws in the same plane.

Seizing of the top piston ring and burning of its

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MARINE ENGINEERING IN 1962 THE SHIPBUILDER AND M. E. BUILDEX

piston groove is the subject of 1151, and its occur- rence in modern highly rated engines is considered to be due to insufficient cooling of the gases in the annular space between side of piston crown (about top ring) and the cylinder wall. The author analyzes the movement of gas in this region. Pressure rise occurring during combustion causes hot gases to flow into and fill this space, and as the corresponding Reynolds numbers are considerably less than critical, gas flow is considered to be laminar. Ex- pressions are given for gas velocity in terms of crown depth to top ring and piston clearance, and a table of such velocities is calculated for the case of a supercharged Diesel engine having a maximum pressure of 1,420 psi and a temperature at end of combustion of 3,090 deg. F. The crown depth varies in steps from 0.39 in. to 1.5 in., and piston clearance in steps from 3.9 to 19.7 mils.

In [16] the author reports the result of an investigation of the incidence of residual thermal stress failures in C.I. engines of small and medium size. Comments are made on the design of cylinder heads for the inherent reduction of thermal stresses. In choosing materials f o r resistance to thermal stress failure, high duty flake graphite cast irons with small amounts of alloying elements, especially molybdenum, have so far been better than other flake graphite cast irons, probably due to their superior creep resistance. Nodular graphite cast irons, although they have been found superior to flake graphite cast irons in laboratory tests, are inferior in engine tests, probably due to their lower thermal conductivity. Some details are given of a high nickel nodular graphite cast iron which is being investigated for its ability to resist thermal stress failure.

Control Equipment A compact speed governor, suitable for large

marine Diesel engines, has been designed by the Woodward Governor Company of Rockford, Illi- nois, U.S.A. Two spring-loaded accumulators maintain oil pressure at the top of a servo piston which is connected mechanically to the fuel control mech- anisms. A centrifugal governor actuates a pilot valve which controls the oil supply to the under side of the servo piston, the area of which is greater than that at the top. Movement of the pilot valve one way admits oil to the underside, while movement the other way allows the oil to escape. A simple hunting link is arranged to assist in control and damping is provided by a needle valve which can be set to control maximum rate of flow of oil to and from the servo.

An interesting alarm and temperature indicator cabinet for Diesel engines has been developed with the co-operation of Det norske Veritas. Up to 36 sensing elements can be fitted in positions such as oil returns from the thrust and main bearings, crankpins, crossheads and camshaft drive, the cool-

ing oil from pistons, turbo-chargers and jacket water. Elements are compact and easily fitted; an appropriate temperature limit is preset for each position and excessive temperature is indicated by a light or siren at the top of the cabinet. Below these are 36 small lamps, one for each sensing e lo ment, each equipped with its own dial on which can be set the appropriate preset maximum temperature. The lamps normally show a dim light which on “alarm” becomes brilliant. The actual temperature at any element can be picked up and displayed on a thermometer dial which is part of the instrument.

Various methods of control of crankcase explosion flames are discussed in C171, which deals with an experimental and theoretical investigation into the use of oil wetted flame traps to suppress the flame emitted from the safety vents of a marine Diesel engine during a crankcase explosion. In the practical investigation, (Part I), tests were conducted in explosion vessels of 200 and of 66 cu. ft. capacity under conditions which subjected the trap to the greatest possible heating effect, while keeping pressure developed in the explosion to a low level. Traps of mild steel gauze, monel gauze and crimped ribbon were tried. True monel gauze showed no particular advantage over mild steel gauze. The crimped ribbon trap was highly effective in pre- venting the transmission of flame and appeared to be more effective than the gauze, but it was more liable to suffer damage by melting.

Part I1 of the paper presents a method of esti- mating the required flame trap size both for gauzes and for crimped ribbon, and compares the values obtained with the practical tests of Part I. Reason- able agreement is obtained. It is estimated that using twelve layers of gauze as the maximum practicable, a vent ratio of 7.8 sq. in. per cu. ft. would be required to quench the flame and resist melting.

In Part I11 the experimental and theoretical results are considered in relation to low-speed propulsion engines. It is concluded that with such engines it is not practicable to provide sufficient flame trap area to suppress with certainty the flame from a “ d d ” explosion. Reliance should be placed on suitable siting and shielding of the vents, rather than on the degree of protection afforded by flame traps of inadequate area.

GAS TURBINES AND FREE PISTON MACHINERY

The final breaking up of the Shell G.T. tanker Auris appears to confirm that, for the time being, the orthodox gas turbine is not considered as a satisfactory alternative to the Diesel engine for the main propulsion of merchant ships. However, interest is still alive in its possibilities for auxiliary power generation, particularly in large vessels.

The United States Lines ship Pioneer Mom has been fitted with an auxiliary power plan- 1,100-

388 Naval Enqinmmra Journal, May I9U


H.P. Solar Saturn gas turbine driving a 600-KW generator. The exhaust gases for the turbine pass through a boiler and generate 5,000 pounds of steam per hour at 150 psi for heating, galley and laundry, with an overall utilization factor of 65 per cent. The electrical and steam outputs are more than adequate for harbor requirements, and are adequate for auxiliary requirements at sea. The total weight of the installation including the boiler is 15,750 lb., of which the turbine and generator account for 8,750 lb.

The turbine and generator are carried on a com- mon bedplate mounted in the engine-room with no special foundations. The boiler is suspended from the deck head and is shaped to fit the available space. The plant is fully automatic in operation, started by push button, it is on line in less than one minute and full steam is available in ten minutes. When in port, the main boilers and all associated plant can be completely shut down, giving maximum time for maintenance and improving overall fuel economy.

In the paper “Marine Gas Turbines in the Royal Navy,” [lS] the author divides the subject into five sections:- (i) gas turbines for major warship propulsion, (ii) gas turbines for high speed craft propulsion, (iii) gas turbines for electrical power generation, (iv) miscellaneous gas turbine applications, (v) general conclusions. For those interested in merchant ship applications, section (iii) dealing with auxiliary power generation is the most interesting.

Generator sets manufactured by W. H. Allen, Sons & Co., Ltd. (500-KW), Ruston & Hornsby, Ltd. (750-KW), and the Rover Co., Ltd: (40-KW), have been developed and tested. Restrictions on the space available for air inlet and exhaust trunking in war- ships is partly due to military requirements and might account for some of the initial disappoint- ments. There appears to have been particular sensitivity to compressor fouling, but this is being overcome and recent experience has been more encouraging. Compressor washing has had to be carried out weekly and liquid cleaning agents have been found more satsifactory than solid agents.

A Russian project for powering refrigerated ships and tankers by gas turbines is given in some detail in 1193. Non-reversible gas turbine units of 6,500- H.P. each, can be used either singly or two coupled together to supply 13,000 H.P. to a single screw shaft, driving a controllable pitch propeller. Each unit has the following components arranged in line. A two-stage single wheel I.-p. turbine is directly COUPled to a 12-stage h.-p. compressor, and through gearing drives the main fuel pump and the main servo oil pump for the controllable pitch propeller.

Free Piston Machinery The Japanese tug Hiryu Maru, having com-

menced service in February, 1961, had completed

2,011 hours of commercial service by February, 1962, and the results of operating experience over this period are given in a technical article in Japa- nese Shipping and Shipbuilding, Vol. 2, No. 7, May, 1962, together with details of the vessel and her machinery.

It was overhauled and inspected after 1,000 hours and after 2,000 hours running; particulars of cylinder wear, piston ring wear for the two S.I.G.M.A. gasifiers are tabulated. Apart from minor defects, one gasifier piston connecting bearing was replaced during overhaul-this bearing is an old type, since modified by S.I.G.M.A., who intend to replace all of the old design by the modified type.

Owing to frequent maneuvering, a superior quality heavy fuel was used and the 2,000-S.H.P. machinery generally operated in the range 1,000- 1,400 S.H.P., in service. For short and sudden reduction of load, surplus gas is released to atmos- phere, while for prolonged periods at reduced power, recirculation of the gas was adopted. Use of a new type of stabilizer smoothed out in about two seconds gas pressure fluctuations caused by very large load change. The gasifier fuel controls are coupled to the variable pitch propeller control and a safety device is incorporated to prevent excessive torque. Remote control is used. The tug can exert a towing hawser pull of 31 tons and has sufficient stability to withstand a 30-ton side pull on the towing hook. The engine-builders, Nippon Kokau are to manufacture six, 4,000-S.H.P. free-piston units for installation in dredgers.

STEAM TURBINES AND BOILERS

Two papers, each bearing the title of “Post-War Development and Future Trends of Steam Turbine Tanker Machinery” [20, 213 were presented at the International Conference organized by the Institute of Marine Engineers. After a historical review of development, the principal sections of the papers deal with the development of machinery producing 16,000, 20,000 and 25,0000 S.H.P. Main particulars are given in Table I.

In [203, the review of the experience of the past few years forms a valuable part of the paper, with many sources of trouble being candidly commented on. In view of persistent boiler tube failures it is apparent that despite the nominally conservative ratings of merchant marine boilers in terms of heat release per cu. ft. of furnace volume and per sq. ft. of radiant heating surface, the actual local heat transfer rate in the area prone to tube failure must be excessive. As a result it is considered that the ideal boiler for taqker service (where height is seldom a problem) should include the maximum furnace volume which can be accommodated within the contours of the ship. It is hoped that this, together with the improved methods of oil burning

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MAFUNE ENGINEERING IN 1962 THE SHIPBUILDER AND M. E. BUILDER

(including steam atomizing) will help to improve boiler reliability.

The finally selected heat cycle for the 20,000- S.H.P. design incorporates the maximum possible use of bled steam from the 1.-p. turbine, including a condensate circulated distiller, combined 1.-p. feed heater and drain cooler de-aerator, split economizer with h.-p. feed heater and two stages of bled steam air heating, and was calculated to give an average service fuel rate of 0.512 lb. per S.H.P./hour, based on boiler conditions of 6,000 psig at 900 deg. F. The cycle is diagrammatically shown in Figure 1.

The question of back pressure versus self-condensing generation for electrical power is fully dealt with, and for this particular design the choice is for self-condensing turbo alternators, one high- efficiency type and one low-efficiency type with consumptions of 10.9 and 26.0 lb. per KW/hour respectively.

Heat balance flow charts are given in [21] for a typical present-day 20,000-S.H.P. installation, 600 psig at 875 deg. F. with a fuel consumption rate of 0.508 lb. per S.H.P./hour and for a projected 22,000- S.H.P. installation, 12,000 psig at 950 deg. F., with a fuel consumption rate of 0.465 lb. per S.H.P./hour. The advance in steam conditions shows a possible saving in fuel consumption of 8 per cent.

A design study is given in considerable detail in [223 for a new, simplified, standardized, mechanical and functional arrangement of the main propulsion unit for a Mariner 20-knot cargo vessel. For a unit developing 16,400 S.H.P. the machinery weight is reduced by 155 tons and the machinery space volume is slightly reduced with the length of the space reduced to 47 ft. 6 in. from values in excess of 55 ft. 0 in. These reductions of weight and space en- able the comparable ship with similar form to carry the same cargo the same distance at the same speed and yet be finer, allowing a reduction in service S.H.P. of 1,100. There are significant reductions in first costs, while fuel costs can be reduced by 13 per cent and, owing to reduction of engine-room crew, the wages cost is reduced by 12% per cent.

The initial steam conditions are taken as 850 psig and 950 deg. F. The basic steam cycle uses high- efficiency, cross-compounded turbines, four-stage regenerative feed heating and high efficiency boilers fitted with regenerative air heaters-no economizer is fitted. The steam flows aft in the h.-p. turbine, crosses over and then flows in a forward direction through the 1.-p. ahead turbine which exhausts axially into the condenser. The astern turbine is located in the 1.-p. turbine casing, with its associated bearing directly accessible. The main condenser, which also serves one of the turbo generator units, is designed for scoop circulation, but is evacuated by means of motordriven vacuum pumps. The two turbo generating sets, one condensing and the other a back pressure set, and the main feed pumps are operated by bled steam. Gear K-values of 125/95

Figure 1. Heat Balanc4pl i t Economizer System for Vessels of 68,000 tons deadweight.

have been selected for use in the single plane type double reduction gearing. The gear elements are arranged with all centers in the same horizontal plane. The overall height of the machinery is reduced while accessibility is improved. The turbine and gear components can be packaged into three self-sufficient factory-assembled units, and much of the auxiliary plant is also designed as packaged Units.

Tube Deposits, Waterside and Fireside

Heat transfer tests have been carried out on tubular specimens of ferritic and austenitic types of superheater alloys which had previously been ex- posed to high temperature steam for periods of 6, 12 and 18 months, in order to determine the effect of corrosion by steam [23]. Specimens of scaled tubes and new tubes of the same alloy were ma- chined externally to the same dimensions, mounted in similar heat exchangers and tested in series under conditions such that the only difference was in the scaled inner surface of the corroded tube and the bright, smooth, honed inner surface of the clean tube. The heat transfer rate across the ferritic tubes was reduced by as much as 15 per cent, whereas for the austenitic tubes, the thin dense scale had the effect of increasing the heat transfer rate by about 8 per cent, possibly because of the increased roughnffs of the corroded surface.

Satisfactory results still continue to be reported of the effect of hydrazine treatment in protecting steam generating surfaces. Owing to its effect in reducing total dissolved solids, it also reduces the likelihood of solids carry over and in several cases its use has resulted in the cessation of superheater tube failures due to this effect. Its use is also reported to have successfully eliminated the phe- nomenon of “hide out” in a boiler due to its maintenance of clean tube conditions.

390 Naval Engineen Journal. May I 9 0


Non-bled steam rate Ib./s.h.p. hr.

TABLE I-Principal Machinery Particulars for the Post-War Classes of Tankers

6.91 6.20 6.15 5.77 *5.75/5.62

Single casing 15 rows all impulse 4.450 r.pm.

Double caslng. two flow

2 x 15 rows all reaction

3,685 r.p.m.

EN.8 EN25

80 76

Type of casing No. of staees

Double caslng 12 mws all impulse 4,996 r.p.m.

Double casing, one flow

+7 reaction 5 impulse

2,733 r.p.m.

EN.8 EN.25

97 80

Normal spe-d

Type of casing L.P. turbine:

Desim vacuum in. Hq. 1 2R.S

No. of stages

Normal speed

28.5 28.5 28.5 28.5

Gearing: Material: wheels Pinions

"K' factor: Primaries Secondaries

Ib/.hr. Normal service evapora-

tion ex tank heating Ib./hr.

' Singlecasing 14 rows all impulse 3.989 r.p.m.

Double casing, two flow


3,662 r.p.m.

2 x 55,600 2 x 55.600 2 x 63.000 2 x 57.000 2 x 74.300

F.S. 34-38 tons/sq. in.

Nickel Steel 67 60

3?; per cent

Design fuel consumption

Percentage improvement

Ib./s.h.p. hr. tons/_day

in fuel rate

Single casing 15 rows all impulse

Double casing, two flow


3.700 r.p.m.

tons/sq. in.

0.615 0.577 0.573 0.525 *0.508 82 86.5 98 90 *109

Bash 6.2 6.7 14.6 17.4

71 8o I

Single casing 10 rows all impulse 5.402 r.p.m.

Double casing, one flow

+4 reaction 5 impulse

3.556 r.p.m.

EN.9 EN26

92 77

1 Turbo-alternators: I I I I I I ~ _ ~ _ . -... Number, size and type 1 2-600kW. I 2-6OohW. I 2-750kW. 1 2-700kW. I 2-750kW. Fuel consumption: I self-condensing I self-condensing I self-condensing I b ackpressure I condensing i

at 900" F.

Fireside tube deposits can be kept to a minimum by water washing the fuel prior to combustion. The results of about a year's experience with the Sharples water-wash system in the tanker Atlantic Seaman is reported [24]. When the water-wash system was put into operation, the boiler tubes were of various ages and in various conditions. Inspection in service revealed little significant for- mation of deposits on the surfaces of generator and superheater tubes. The total accumulation of slag deposits after about two years' operation was fairly light (water washing had been practiced only for the last 12 months of this period).

Boiler Tests Tests carried out during trials on a boiler intend-

ed for the passenger liner France were undertaken by engineers responsible for both the design and testing of the boilers concerned. The results in C251 include a comparison between heat transfer data used for design purposes and data obtained by m82asurements taken at the trial. An adequate c m - perison is only possible if the heat transferred in

the furnace by convection and radiation can be measured separately. The method of measurement adopted is described and the validity of the results is assessed. Discrepancies between measured and estimated data are noted and discussed. A more recent method of estimation of heat transfer in fur- naces, due to Hottel, gives much closer agreement with measured values and appears to confirm that the efficiency of combustion in the boiler is very good.

The latest development in the Foster Wheeler range of marine boilers is the E.S.D.ll. The first of this type was built by Richardsons Westgarth, Ltd., who had retained it for trials and demonstra- tions. "his particular boiler can generate 80,000 lb. per hour at 925 p i g and 915 degrees F., but units capable of 176,000 lb. per hour at 785 psig and 914 deg. F. are being built. In the Mark I1 of the E.S.D. boiler, the control unit and superheater have been modified to eliminate the intermediate superheater headers and to simplify the construction. The superheater width is constant for the whole height

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MARINE ENGINEERING IN 1962 THE SHIPBUILDER AND M. E. BUILDER

and the by-pass is fitted between the main gas baflle and the generating bank without increasing the overall width. This in turn leads to a smaller superheater surface and at higher loads the area for gas flow across the control unit enables the overall draft loss to be kept low. The pressure drop on the steam side is also reduced by the elimination of the attem- poratot circuit. The design is such that alloy steel is only required for the superheater lower rows and outlet header. Greater use is made of the combustion air for cooling the casing. In use, the boiler proves to be very flexible.

NUCLEAR POWER

‘N.S. Savannah By the end of August, 1962, the N.S. Savannah

had logged 9,848 nautical miles and some details of the operating experience and arduous pre-critical assembly testing is given in [26]. The initial fuel loading took just under 30 hours and criticality was achieved on the 21st of December, 1961. While at the fitting-out base at Camden, N.J., the wwer generated was limited to 10 per cent, at which condition the reactor showed excellent load-following and self regulating characteristics. After transfer to Yorktown, Va., the power output was increased up to 40 per cent. On the journey the auxiliary steam boilers were tested and were finally able to drive the ship at 1 2 knots and the “take home” motor was able to maintain 8 knots.

The official acceptance trial was conducted from the 24th to 26th of April, 1962, and consisted pri- marily of various ship tests, since most of the power plant tests had already been successfully completed. Automatic operation of the steam dump system was demonstrated, however, the test consisting of closing and opening the main steam valve with the steam dump valve set to open at the initial throttle pressure. The steps involved were:

(1) Closing the throttle valve from 104 r.p.m. (about 58 M W in 20 seconds).

(2) Keeping it closed for eight minutes. (3) Opening it to the 104 r.p.m. position again in

20 seconds, with no control adjustments being made. During this test the reactor power and steam

pressure varied only 5 MW and 10 psi, respectively. Various transient tests carried out from full

power conditions confirmed that the reactor is stable and self-regulating for load changes as large as 40 per cent full load and that the control characteristics of the complete plant are such that even the most severe transient can easily be handled by manual control. The reactor was deliberately scrammed from a power level of 70 MW. Within 20 seconds, the Diesel generators were paralleled with the turbo generators and the ship was powered with the “take home” motor. The reactor was able to regain criticality one hour and 33 minutes after scram. Other tests were carried out on the effec- tiveness of the shield, the nuclear instrumentation,

radiation monitoring devices, and water quality ili primary, secondary and intermediate loops. An analysis of suspended solids in the primary loop during the 100 per cent power run indicated that 99 per cent of the activity came from manganese. There was no detectable Activity from iron, cobalt, tungsten or chromium. Only an infinitesimal amount of fission product activity was detected. No radio- active materials were found in the intermediate and secondary systems. Such results are similar to those for other pressurized water reactors with good structural integrity.

After the acceptance trial, there were various demonstration runs and the vessel went into commercial service on the 28th of August.

Some Problems In dealing with some of the problems of merchant

ship nuclear propulsion, the author of [271 points out that all marine reactor installations proposed to date are totally uneconomic and, furthermore, the apparent savings possible with new reactor designs disappear when a project is required to con- form to the accepted conservative design criteria and construction codes for marine nuclear work. Thus he examines the major engineering and ship items which are amenable to modification and cost reduction without impairment of the necessary reliability.

Elimination of a separate containment vessel is feasible if the hull structure can be safely stiffened and strengthened to form a containment compart- ment of such a size that the maximum pressure would not exceed 30 psig. The alternative to containment in the hull structure might be to reduce the size of the containment vessel. This could be achieved by reducing loop dimensions and installing the heat exchangers adjacent to, or even inside, the reactor vessel. Any increase in containment pressure will be more than offset by reduction in size and thus containment plate scantlings will not increase, they may even be made lighter.

The author critically examines reactor vessel, primary circuits, heat exchangers and pumps from the point of view of materials and design, bearing in mind that it is necessary to reduce the capital cost of a commercial marine nuclear plant by a factor of three. Reference [28] indicates the possibility of using low-alloy steels in place of more sophisti- cated and expensive stainless steels, owing to the high degree of corrosion resistance of the former material that is achieved by inducing a film of mag- netite on the internal wetted surface by steam processing.

The problems of shielding, control, instrumentation, refuelling, collision protection and nuclear safety are commented on. When considering the possible types of marine reactor, it is considered unlikely that the pressurized water, boiling water or organic liquid moderated types of reactor can

392 NdVdl Enqinwrs Journdl. Mar I963


ever achieve a state better than parity with conventional installations even when fully developed. The three other types mentioned are the high-temperature gascooled reactor, steamcooled heavy- water reactor and steam-generating heavy-water reactor, but a full assessment cannot yet be made of their suitability for shipboard use as they are not yet sufficiently developed.

In C2Sl on the Dounreay Submarine Prototype, the authors give a brief discussion of background history of the installation and follow with a detailed description of the prototype reactor, its associated installations and of some design and manufacturing problems. An important feature of the primary circuit is the so-called “crevice free” design, intended to prevent lodgment of radi-active isotopes in in- convenient places. Examples are given of the design of main valves and pressurized heater pockets.

The basic design considerations of the plan are reviewed and given in reference C291. Two coolant loops were decided on with several pumps in paral- lel and arrangements for quick shut down. There was difficulty in arranging suitable pipe runs owing to the geometry of the installation, but in the final arrangement thermal stresses were kept below 40 per cent of minimum U.T.S. The advantages and disadvantages of possible primary circuit materials are discussed and the special precautions required to prevent contamination or corrosion during manufacture are commented on. The operation of the pressurizer is discussed; it is used to establish the pressure in the primary coolant circuit, to limit pressure changes due to volume change of coolant and to degas it. The testing procedure for most parts of the plant is described.

GEARING AND TRANSMISSION

Naval Development In the first part of C301, the authors give details

of some Naval propulsion gears of this period and corresponding records of their performance on trials and in service. Experience with the Whitby-class vessels and the result of full-scale trials suggest that for through-hardened, hobbed and shaved gears, and with the best available material combina- tion (En.26 pinions and En.9 wheels), the maximum permissible loads should not exceed 200 K for primary gears and 160 K for secondaries, if using a normal lubricating oil without E.P. additives. One set of the Y.100 Mark I1 gears has been fitted with a carburized and ground En.36 primary pinion and nitrided and ground En.40, primary wheels the face width having been reduced to raise the tooth loading to 450 K. The direction of rotation is such that the apices of the gear are trailing.

The 30,000-H.P. Y.E.A.D.I. gears represented the first British attempt to design and manufacture a carburized and ground marine propulsion set of large power. The design is of the double-reduction, d’ial-tandem, articulated type with single helical

En.36a carburized hardened and ground gears, required to run satisfactorily on a grade of oil not containing E.P. additives. Gear proving trials were carried out over the full range of power, with instrumentation arranged for measuring bearing temperatures, conditions in the lubricating-oil system and gearcase distortion. The gears performed very satisfactorily throughout the trials and the gear tooth surface remained in excellent condition with indications of full face contact at full power. Dis- tortion of the casing was also carefully measured.

Of particular interest are the descriptions of the Y.102A and Y.111A gears fitted in the new County- class guided-missile ships and the TribaGclass general-purpose frigates, respectively. The main propulsion machinery of these ships consists of steam and gas turbines and the gear designs permit:

(a) Ahead and astern operation with the ahead and astern steam turbine.

(b) Use of gas turbines to boost the ahead steam turbine power output.

(c) Use of gas turbines alone fo r ahead power. (d) Use of gas turbines alone for ahead &d

astern operation. The general layout of the Y.102A gears is shown

in Figure 2. The steam turbine gear trains and gas turbine boost gear trains are of the double-reduction, tandem articulated type and the maneuvering drive from each gas turbine comprises ahead and astern gear trains with associated hydraulic cou- plings, manually operated clutches and main syn- chronizing clutches. These latter permit the gas turbines to be connected to the propeller shaft when i t is rotating in the ahead direction. They engage automatically at synchronism and are then locked into engagement to become capable of transmitting both ahead and astern torques. Leading design data of the gearing is given in Table 11.

In the majority of ships’ sets, the gears are in En.36 steel and are carburized, hardened and ground. In some a number of induction hardened and ground gears in En.24 steel are nitrided and ground gears in En.40, have been installed. Under normal ahead operating conditions the tooth loading does not exceed 465 K; however, when maneuvering at full power astern on one gas turbine alone, the associated astern gear train (in the Y.102A design) is loaded up to 819K. During gear proving trials ashore, an outboard gas turbine astern pinion and idler have been run for one hour at this load without ill effect. To date, the U.102A shore trials have completed over 1,000 hours running, including 110 hours at full power and 33% hours continuously at 130 per cent full torque. The gears are in excellent condition. E.P. lubricating oils have been used throughout the trials.

In the second part of the paper, some opinions on lubricating oil filtration, cleanliness and flushing

Naval Enpinoarc Journal. May 1963 393

MARINE ENGINEERING IN 1962 THE SHIPBUILDER AND M. E. BUILDER

F Steam

Figure 2. Sectional View of Y.102 Gearbox Port Set.

TABLE 11-Leading Design Data for Y.102A Gearing

~~

angle (maximum)

Pitch No.of Normal Face Helix Normal circle teeth pitch, Width. angle pressure factor

Gear dlameter. in. in. in.

H.P. flnt reductlon pinion 7.96 28 424 H.P. flnt reduction wheel L.P. Arst reduction ptnlon 11.65 41 312 L. P. flrst reduction wheel 33.54 118

H.P. second reduction pinion 12.83 33 419 L.P. second reductlon pinion 12.83 33 1.2 13 10 deg. 43 min. 20 deg. 464

33.54 118 0.8 8.5 26 deg. 23 min. 20 deg.

~ _ _ _ ~ ~ ~ .

Main gear wheel 11.92 185

Primary input wheel Primary output wheel

~~

13.61 52 13.61 52 0.8 7 13deg.24min. 20deR. 319

First reductlon pinion 12.04 46 First reduction wheel 38.48 147 0.8 7 13deg.24min. 20deg. 314

Second reduction ptnlon 12.63 33 1.2 13 10deg.43min. 20deg. 424 ~

Astern pinion 8.12 31 819. Astern idler 8.38 32 0.8 7 13 deg. 24 min. 20 deg. 530 Astern wheel 25.65 98

*!ull power astern on one gas turbine (emergency condition&

394 Naval Enpinews Journal. May I963


are expressed and experience with E.P. lubricating oils is described.

Circarc Gears It has been known that gear tooth profiles, other

than the involute, could give higher load capacity or lower friction loss, but experience with such forms has usually resulted in a reversion to the involute profile, which has the merits of being simpler to produce and of lower sensitivity to assembly im- perfections.

A new appraisal has recently been made by Asso- ciated Electrical Industries, Ltd., of the Wildhabet- Navikov gear in the light of the higher standards of accuracy offered by modem gear case machining [31]. The basic principles of the tooth form are discussed, and it is claimed that the system will operate satisfactorily with small number of teeth and that radii of curvature conditions are favourable with low helix angles.

REFERENCES

[I] “Automation in U.S. Shipping,” by C. J. Clayton; So- ciety of Naval Architects and Marine Engineers (New York Section), October, 1961.

[2] “Automation of Steamship Machinery,” by H. Lameris; Association of Ship Technologists (Netherlands) and reprinted in Schiff und W e d , February, 1962.

(31 “Automation in Ships,” by P. L. Bain and Q. Vilcoq; Association Technique Maritime et ABronautique, May. 1962.

(41 “Remote Control of Cargo Handling,” by I. H. Vincent; A.P.I. Annual Tanker Conference, 1962. Summary in Mahne Engineering (New York), May, 1962.

(51 “The Gotaverken Diesel Engine,” by G. Yellowley and L. T. Collin; North-East Coast Institution of Engineers and Shipbuilders, April, 1962.

(61 “The Doxford Direct Drive Diesel Engine,” by P. Jack- son; Institute of Marine Engineers (International Con- ference), May, 1962.

[7] “Direct Drive Diesel Machinery,” by H. Andresen; Institute of Marine Engineers (International Confer- ence), May, 1962.

[S] “Hydraulic Fuel Injector for Diesel Engines,” by K. H. Gray; Shipping World, April, 1962.

[9] “The Matching of Two-stroke Engines and Turbo Su- perchargers,” by J. H. Horlock and R S. Benson; C.I.M.A.C. Conference, Copenhagen, 1962.

1101 “The Energy Content of Exhaust Pulses in the Exhaust System of a Supercharged Two-stroke Engine Model,” by R. S. Benson and W. A. Woods; International Jour- nal of Mechnical Science, Vol. 2, 1961.

Ill] “Exhaust Belt Design in Two-stroke Diesels,” Engi- neering, Vol. 193, February, 1962.

I121 “Crankshaft Arrangement and Firing Orders,” Marine Engineering, Vol. 84, October, 1961.

[I31 “De Schelde Engine Balancing System for 9RD90 Schelde-Sulzer Engine”; Holland Shipbuilding and Ma- rine Engineering, December. 1961.

[14] “Determining the Strength of Large Crankshafts,” by J. W. Roeder and J. K. Doane; Society of Mechanical Enpineers, April, 1962.

[15] “Wire Drawing of Gases Round Piston Crowns,” by B. Ya Gintsburg; Veshik Mashinostroeniya, Vol. 12, December, 1961.

[ U ] “Residual Thermal Stresses in Compression Ignition Engines,” by A. Dearden; Institute of Marine Engineers, June, 1962.

[17] “Crankcase Explosions in Marine Oil Engines-The Efficacy of Gauze and Crimped-ribbon Flame Traps,” by K. C. Brawn; Institute of Marine Engineers, August, 1962.

[18] “Marine Gas Turbine in the Royal Navy,” by G. P. A. Trewby; Institute of Marine Fhgineers (International Conference), May, 1962.

[19] “Marine Gas Turbine Installations,” by G. A. Ogloblin; Suhstrmie, Vol. 27, October, 1961.

(201 “Post-war Development and Future Trends of Steam Turbine Tanker Machinery,” by E. H. W. Platt and G. Strachan; Institute of Marine Engineers (International Conference), May, 1962.

211 “Post-war Developments and Future Trends of Steam Turbine Tanker Machinery,” by H. G. Bauer; Institute of Marine Engineers (International Conference), May, 1962.

221 “Improved Steam Propulsion Plant to Reduce Building and Operating Costs,” by D. C. MacMillan and E C. &tide; Society of Naval Architects and Marine Engi- neers, November, 1962.

231 “The EfFed of Corrosion by Steam at 1,100 Deg. to 1,500 Deg. F. upon the Heat Transfer Through Super- heater Tube Alloys,” by H. L. Solberg, J. E. B d and W. J. Rebello; American Society of Mechanical Engineers, National Power Conference, 1961.

241 “Reduction of Fireside Deposits in Marine Boilers,” by W. A. Walls and W. S. Proctor, Journal of the Insti- tute of Petroleum, Vol. 43, April, 1962.

1251 “Some Results of Tests on a Boiler for the Liner France,” by P. Fanconnier and Des. Robert; Bulletin of the Association Technique Maritime et Athmautique, 1962.

[26] “Operating Experience with Nuclear Propulsion; Start- up and Initial Operation of the N.S. Savannah,” by J. W. Landis; Joint Panel on Nuclear Marine Propulsion, 1962.

1271 “Problems of Merchant Ship Nuclear Propulsion,” by B. Hildrew; Institute of Marine Engineers (Internation- al Conference), May, 1962.

(281 “The Dounreay Submarine Prototype,” by W. T. C. Ridley, H. T. Lewis and D. L. Alexander; Joint Panel for Nuclear Marine Propulsion, March, 1962.

I291 “Experience in the Design and Manufacture of Marine Nuclear Plant,” by D. J. Pepper; North-East Coast Institution of Engineers and Shipbuilders, January, 1962.

[30] “Progress and Development in Naval Propulsion Gears, 1946-1962,” by P. D. V. Weaving and W. H. Sampson, Institute of Marine Engineers, December, 1962.

[31] “The Development of Circarc Gearing,” by C. F. Wells and B. A. Sholter; A.E.I. Engineering, Vol. 2, March/ April, 1962.

Naval Enginmars Journal, May 1963 395

396 Naval Enqinaar? Journal. May I963

Documents

TECHNICAL PROGRESS IN MARINE ENGINEERING DURING 1962