7
SHIPBLDR. AND MAR. ENG.-BLDR. TECHMW PROGREW IN MARlNE ENGINEERING DURING 1963 ACKNOWLEDGMENT This article is reprinted from the January. 1964 issue of “The Ship- builder and Marine Engine-Builder. IN HIS PRESIDENTIAL ADDRESS to the Institute of Marine Engineers, Sir Nicholas Cayzer, Bart., said “The position of Great Britain since the war has changed, and continues to change, radically. We are more dependent today on our skills and inventive- ness than for many generations. We cannot rest on our past greatness. Our future will depend on our ability to meet change in a changing world.” In reviewing the progress made in marine engi- neering during the past year it is clearly evident that British marine engine-builders are not only ready to meet change in a changing world but, wherever possible, they intend to anticipate it. STEAM TURBINES AND BOILERS The main testbed of the B.S.R.A. Wallsend Re- search Station has been busily occupied during the past year. The permanent boiler (3,000 lb of steam per hour, 1,200 Ib per sq. in. gauge, 1,200 deg. F.), has greatly facilitated the work.’ The h.p. turbine for the British Venture, the first of the standard Pame- trada turbine sets, was successfully tested and has been followed by a prototype for advanced steam conditions developing 22,000 S.H.P. at 108 r.p.m. The steam conditions are higher than those used at sea, viz., 850 lb per sq. in. gauge and 1,050 deg. F. at the superheater outlet. Extensive trials at this tempera- ture, which correspond to 1,035 deg. F. at the tur- bine inlet. have been very successful, including rapid transient maneuvering trials. Due to the relatively high incidence of failures of turbine thrust bearings, a large research effort has been devoted to the elucidation of the problem. The most recent failures have been associated with the production of steel wire machined from the surface of the thrust collar due to debris embedded in the white metal of the thrust pads. This phenomenon has been reproduced under controlled laboratory conditions. A parallel investigation was the trial at sea in the British Prestige to examine the operating condi- tions of an h.p. turbine thrust under service condi- tions. This investigation was of a very detailed nature and began with an examination of the main line shafting, movement of the main thrust block, shuttling at the h.p. fine tooth coupling and two independent methods of measuring thrusts sensitive enough to obtain the full vibration characteristics. It is known that supersonic steam speeds occur Naval Enpimri Journal. Aupuit. IW 639

TECHNICAL PROGRESS IN MARINE ENGINEERING DURING 1963

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SHIPBLDR. AND MAR. ENG.-BLDR.

T E C H M W PROGREW IN MARlNE ENGINEERING DURING 1963

ACKNOWLEDGMENT This article is reprinted from the January. 1964 issue of “The Ship- builder and Marine Engine-Builder.

IN HIS PRESIDENTIAL ADDRESS to the Institute of Marine Engineers, Sir Nicholas Cayzer, Bart., said “The position of Great Britain since the war has changed, and continues to change, radically. We are more dependent today on our skills and inventive- ness than for many generations. We cannot rest on our past greatness. Our future will depend on our ability to meet change in a changing world.”

In reviewing the progress made in marine engi- neering during the past year it is clearly evident that British marine engine-builders are not only ready to meet change in a changing world but, wherever possible, they intend to anticipate it.

STEAM TURBINES AND BOILERS

The main testbed of the B.S.R.A. Wallsend Re- search Station has been busily occupied during the past year. The permanent boiler (3,000 lb of steam per hour, 1,200 Ib per sq. in. gauge, 1,200 deg. F.), has greatly facilitated the work.’ The h.p. turbine for the British Venture, the first of the standard Pame- trada turbine sets, was successfully tested and has been followed by a prototype for advanced steam conditions developing 22,000 S.H.P. at 108 r.p.m. The

steam conditions are higher than those used at sea, viz., 850 lb per sq. in. gauge and 1,050 deg. F. at the superheater outlet. Extensive trials at this tempera- ture, which correspond to 1,035 deg. F. at the tur- bine inlet. have been very successful, including rapid transient maneuvering trials.

Due to the relatively high incidence of failures of turbine thrust bearings, a large research effort has been devoted to the elucidation of the problem. The most recent failures have been associated with the production of steel wire machined from the surface of the thrust collar due to debris embedded in the white metal of the thrust pads. This phenomenon has been reproduced under controlled laboratory conditions.

A parallel investigation was the trial at sea in the British Prestige to examine the operating condi- tions of an h.p. turbine thrust under service condi- tions. This investigation was of a very detailed nature and began with an examination of the main line shafting, movement of the main thrust block, shuttling at the h.p. fine tooth coupling and two independent methods of measuring thrusts sensitive enough to obtain the full vibration characteristics.

It is known that supersonic steam speeds occur

Naval Enpimri Journal. Aupuit. IW 639

PROGRESS IN MAR. ENCRC. SHIPBLDR. AND MAR. ENC.-BLDR.

in certain present-day turbines. for example, in auxiliary turbines and in the astern turbine of main propulsion machinery. Research has shown that the forms of bladmg currently used in such turbines are not suited to these very high steam speeds, and in effect constitute a lrmitation in the amount of work which can be performed by a turbine stage at hgh efficiency.

Research is in progress at the Wallsend Research Station to develop blade forms which will operate satisfactorily at supersonic steam speeds. Methods of designing such blades have been developed, as- sisted by tests in a supersonic wind tunnel. The stage has been reached at which supersonic blades operating in an experimental turbine have given high efliciency. Experimental work is continuing to obtain a more detailed knowledge of the factors involved, so that supersonic blades can develop high a c i e n c y in normal ahead blading. This will lead to still smaller turbines, particularly at the h.p. end, in relation to power, and render such turbines able to take further increase in inlet temperature due to the smaller size of the casings and rotor.

Full details of shore trials of marine steam tur- bines are given by Brawn [I]. There is no doubt that full-scale trials, even of machinery only, p m vide much more accurate data with smaller risks than would be involved in trying out new features at sea, where, if modifications are required, the cost is very high. It is also true that designers can do a brilliant job with research results as a guide, but the final proof of their endeavors is accurate meas- urement of overall quantities of power in relation to steam flow and demonstration that the machinery will withstand rapid transient temperatures and pressures during maneuvering without undue dis- tortion. The paper shows the development in ac- curacy and the greater precision in distorting measurements which have been developed from simple “hog” wires to complete water-cooled space frames kinematically supported with recorders able to deal with rapid transient conditions.

Occasional instances of the formation of hard bonded deposits of fuel oil ash in the tube bundles of marine boilers have arisen throughout the his- tory of oil-fired marine water-tube boilers, but these events have increased in frequency in recent years, and some shipowners now regard the ex- ternal cleaning of boiler tubes, at relatively short intervals (two or three months), as an inevitable routine operation. Some results from a fuel-oil water-wadung plant in studies of the fouling of marine superheaters is given by Tipler [2]. While the rate of formation of these deposits is influenced by boiler design and operation variables, neither of these factors is readily changed once a vessel is in service. The author has, therefore, given consider- able attention to the possibility of modifying the characteristics of the fuel ash. One approach is the water washing of fuel oil to minimize its sodium

content and thus reduce the formation of low melt- ing sodium compounds which form the basis for de- posit formation. The author comments on previous experience with water-washing systems and gives details of sea trials on the S.T.S. Partula an 18,000- ton bitumen carrier. The flow diagram of the fuel- oil water-washing plant on thls ship is given in Figure 1. It is concluded that in existing installa- tions considerable improvements in superheater conditions are possible by raising the standard of combustion. This may imply the replacement of oil-worn or abused components, or alternatively the retraining of staff to take full advantage of the equipment in their charge. Regular and thorough soot blowing is also essential in multi-boiler instal- lations, it is preferable to operate all units at a moderate output, rather than holding one boiler in reserve while the remainder operate at their nomi- nal ratings. There are many boilers in service which, due to their over compact superheat design, are very vulnerable to fouling. In these extreme cases, it may be an advantage to investigate the effects of fuel centrifuging. With regard to new construction, design factors should receive due consideration. Land experience of steam temperatures over 1,000 deg. F., shows that temperatures up to at least 1,000 deg. F. are practicable without serious superheater fouling, provided care is taken in the design of the superheater from aerodynamic aspects. There is. therefore, no need to halt the present upward trend in marine steam temperatures provided smiliar pre- cautions are taken.

DIESEL MACHINERY

A call for British enginebuilders to use their resources correctly and advantageously has been made by Jackson 131. Close co-operation of research teams can lead to the improvement of British en- gines. In delivering the thirty-second Andrew Laing Lecture the author discusses two decades of re- search and development on the Doxford engine. He deals with fuel and starting systems, heavy fuel, crankshafts, turbcharging development of “P’ and “J” engines, balancing and torsional and axial vibra- tions, combustion, tightening uf large nuts, remote control and propeller efficiencies. He examines the proposals which have been put forward for future research and gives an account of the work which Doxford’s have carried out on the relation between rating and fuel consumption, methods of reducing fuel consumption, power-weight ratio and research to reduce maximum pressure. The author considers that a 25 percent improvement in power will not give a corresponding improvement in power/weight ratio. An increase in m.i.p. of 25 percent will lead to an improvement in power/weight ratio of no more than 6 percent since the size of the crankshaft will have to be increased, also the cylinder centers to provide adequate bearings, and the sizes of the side rods and running gear due to the increased

bu) N a r d fnqirwn Journal. Auqult. 1964

SHIPBLDR. AND MAR. ENG.-BLDR. PROGRESS IN MAR. ENGRG.

b-a from

buntrr tank

1 INf COOf

- Purlitrr recycle - Oil skimming linr - Solids discAargu line Purified oil /,nu

Heat @,changer /n le f and O~ t '? f

Figure 1. Flow Diagram of Fuel-oil Water-waahing Plant on the PartuIa.

I 1 I I

i g, I

_ I

' s v - l

9..

r 2nd

maximum pressures. The author has strongly ad- vised Doxfords to stabilize on present ratings for a period until details have been perfected on the "P" and "J" engines so that the best methods of manu- facture of the various components can be applied to reduce costs.

Some ten years ago, when the supercharging of large two-stroke Diesel engines became a reality, a degree of supercharging of about 30 percent was the immediate aim. Recently, engine designers have raised the degree of supercharging from 30 percent to 60 percent, which corresponds to a b.m.e.p. of 120 Ib per sq. in. Gunten and Gyssler [4J have discussed the turbo-charger and the supercharging of large tw-stroke Diesel engines. They give a brief history and development of the Brown-Boveri turbocharger then deal progressively with the general description, latest design, materials used, tests on stressed parts and maintenance. The supercharging of large two- stroke Diesel engines shows much variety. Dist i i - tions can be made according to the way in which the energy in the exhaust gases is utilized. The system used to supply the air also distinguishes the various methods of supercharging. An account is

given of a test installation to investigate the influ- ence of a pulsating delivery pressure upon the shift- ing of the surge line. The results are given in Figure 2. The strong way in which the compressor reacts in the lower frequency range is evident from this diagram. This occurs somewhat according to the rule of thumb, which states that surging can be expected as soon as the maximum delivery pressure reaches the peak of the curve for n = constant under steady state conditions. In the higher fre- quency ranges, which are encountered with the actual engine, the compressor can stand more.

In an attempt to examine the operational reli- ability of post-war built main propulsion heavy oil crankshafts in ships classed with Lloyd's Register of Shipping, the Society's records of reported defects for a ten-year period, 1953 to 1962 inclusive, have been scrutinized by Archer [SI and analyzed in respect of engines of over 1,000 B.H.P. The analysis covem the incidence of cracked, broken or "slipped" shafts (but does not include cracks in couplings) classified in relation to range of horse power, types of crankshaft construction, position of machinery in the ship and location of fracture, and has been given

Naval Engl-n Journal. Auguct. 1W 641

PROGRESS IN MAR. ENGRG. SHIPBLDR. AND MAR. ENG.-BLDR.

204 _ - - . 0 qr 50 v

Figure 2. Compressor and Pulsating Delivery Pressure Resalts of Teats d e d out on a VTR 250 Compressor. The Intake Vdume V is given in m' per m.

for both single-acting, two-stroke cycle, and single- acting four-stroke cycle engines. It is concluded that the calculated margin against fatigue failure of about 1.5 appears unexpectedly slender for a practically Rule-size crankshaft, especially as no attempt has been made to take into account the high loop and appreciable radial static stresses set up by the shrinkage assembly of journals and webs, particularly in the fillets on the underside of the crankpin. Even without the additional allowable torsional vibration stress, which would increase the safety margin to about 1.85, the provision for meet- ing the occasional unpredictably severe operating condition might perhaps be thought none too gener- ous. In the author's opinion, torsional vibration and metallurgical quality merit special attention, while observation of the cardinal rules of design in the avoidance of severe stress concentration at highly stressed positions will assist in reducing still fur- ther the already low incidence of marine crankshaft failures in classed vessels.

NUCLEAR POWER

By February, 1963, N.S. Savannah had logged 29,649 nautical miles and had visited 11 ports. Op- erating experience with the vessel is given by J. H. MacMillan, D. C. MacMillan, Robb, Lill and Me- hann [61. It is reported that the handling character- istics and overall performance of the ship and the reactor plant have been very good. The response time of the reactor in meeting a change in steam demand is rapid. While difficult to compare directly with a conventionally powered ship, it can be said that the Sauannuh's reactor can meet a change in load demand in half to quarter the time which would be required for a conventional ship's plant to meet the same demand. Although this speed may not be necessary in any routine operation, the char- acteristics do provide for easy maneuvering. During the first year of operation, 35 unplanned reactor scrams have occurred the majority of which were attributed to electrical noise in the nuclear installa- tion. Five of these scrams occurred while the ship

was underway, but in no instance was the safety of the ship in jeopardy. None of the scrams resulted in equipment damage, and in all cases the operator response and the recovery procedures proved to be entirely satisfactory.

The reactor plant has provided reliable perform- ance. Recognizing that no prototype for the Savan- nah power plant had been operated previously, the record of plant reliability is very good.

Among the principal maintenance items in the nuclear power plant was the problem of hydraulic leakage at O-rings in the control rod drive system. Following a careful and complete O-ring replace- ment program and the minor redesign of critical components, the leakage of hydraulic oil has been virtually eliminated.

Three years ago, tenders were submitted to the Ministry of Transport for nuclear propulsion ma- chinery of 20,000 S.H.P. suitable for installing in a tanker of about 65,000 tons deadweight. A paper by Davis [7] describes one of the designs submitted by a consortium-formed for the purpose. A brief de- scription of the machinery is given and there are aIso detailed descriptions of particular aspects of the design. Comment is made on the philosophy be- hind the design and the characteristics of the reactor system. This embraces a consideration of basic safety characteristics, the disposal of active waste, refuelling procedure, the control of the plant and its operational response and a brief study of the economics of the project, bearing in mind that while uncertainty must attend any estimate of fuel costs, the capital cost of the installation is established by the firm price embraced in the tender. The author concludes that the problems to be faced are sub- stantially those embraced by the 1960 design. Some problems will be greatly eased by reduction in size, others will remain as relatively troublesome; some will be resolved by general nuclear research and perhaps paper studies, others by research specfical- ly directed to maritime projects; some problems will only be resolved by the operation of a nuclear ship and among these will be the problems that are themselves introduced by the building and operat- ing of the ship.

The effects of prolonged stress relieving treatment on the mechanical properties of reactor pressure vessel steels is dealt with by Watkins, Wood and Nichols [81. The authors have investigated the effect of the long stress relieving treatments given to reactor pressure vessels on the tensile, Charpy impact, creep and stress rupture properties of re- actor quality, low-carbon, )ugh manganese, 28 tons per sq. in. steels. A considerable number of casts have been tested, including open-hearth Si-killed steel, open-hearth A1 grained-refined steel, electric furnace steel and weld metal.

For all the plate materials, stress relieving at 600 deg. C. or above resulted in a fall in the yield point and U.T.S. of about 1-2 tons per sq. in.; for the

642 Naval Enginoars Journal. August. 1964

SHIPBLDR. AND MAR. ENG.-BLDR. PROGRESS IN MAR. ENGRG.

weld metal it was generally three tons per sq. in. or more. Prolonged stress relieving resulted in an increase in the Charpy impact transition tempera- ture of 10-20 deg. C., even at stress relieving tem- peratures as low as 575 deg. C. The impact properties of electric furnace steel did not generally deteriorate on stress relief, and often an improve- ment was observed. Weld metal impact properties showed considerable variability in response to stress relief. Prolonged stress relieving at 600 deg. C. caused a marked deterioration in the creep and rupture strength of Si-killed steel, but the creep strength of A1 grain-refined steel was not signifi- cantly aff ectd by strain relief.

The authors conclude that the deterioration in tensile and high-temperature properties can be min- imized by limiting the maximum temperature and by careful control of the stress relieving cycle, but that the change in impact properties on stress relief must be taken into account even at stress relieving temperatures as low as 550 deg. C. or 575 deg. C.

AUTOMATION

There are some confused and conflicting opinions and ideas on the subject of automation, ranging from those who think it is the answer to all prob- lems and, at the other end of the scale, those who want nothmg to do with the subject. It is inevitable that some form of automation will be universally accepted in the near future, but it must be con- trolled automation. Progress in automation is dealt with by Munton, McNaught and Mackenzie 191. Early automatic controls were all self-operating, that is, the power for operating the control device was provided directly by the change in a condition of the medium being controlled, as in safety valves or in such items as float control valves for con- trolling water level. With the more sophisticated arrangements, adequate power generally cannot be obtained directly from the function being controlled and an intermediate stage has to be introduced so that the variation in the function is merely required to produce a low power signal, which is amplified by pneumatic, hydraulic or electric means, to give sufficient power to provide the measure of control required. Where the degree of automation is lim- ited, and the number of staff reduced in c o w - quence, to obtain the most effective use of the remaining manpower, mechanization to some de- gree, to save human energy, will be found necessary and, to obtain full control, at least some degree of centralization will be required, involving the use of mechanized control.

A pneumatic control scheme giving the basic essentials of combustion control is shown in Figure 3 and includes four major components termed mas- ter steam pressure controller, selector valves, dia- phragm operated fuel valve and piston-operated damper control valve.

It appears to the authors that in the immediate

I. -

1 I I

F w r e 3. Simple Pneumatic Combustion Control Scheme.

future development of automation should be con- centrated on the operation of the machinery from a control room within the machinery space. The next step, and it will be a major step, will be to take the control room right outside the machinery space, with the engineer on watch malung only an infrequent--possibly once per watch-tour of the machnery space. The authors emphasize, however, the great difficulties that have to be overcome to achieve this.

In the Mahout [lo], pneumatic equipment pro- vides remote control of the main Stephen-Sulzer Diesel engine from the bridge. An interesting fea- ture of the auxiliary equipment is that the Rolls- Royce prime movers for the Diesel generator sets are fitted, in addition to normal protection alarms, with mechanical shutdown equipment, which will come into effect if the coolant temperature or lubri- cating oil pressure reach a dangerous level.

An outstanding example of the employment of automatic and remote-control devices to cut down crew is found in the Clan Macgillivray. In this mo- torship the engine-room complement has been re- duced to six engineers, one electrician and 12 Asian ratings. Normal watches at sea are manned by only one engineer and one Asian donkeyman.

Naval Enpinoon Journal, Auquat. 1944 643

PROGRESS IN MAR. ENGRG. SHIPBLDR. AND MAR. ENG.-BLDR.

A system for controlling an M.A.N. Diesel engine from a ship’s bridge was demonstrated during the year by Maschinenfabrik Augsburg-Numberg A.G. [lll. This project has been carried out in collaboration with Allgemeine Elektricitk-Gesell- schaft (A.E.G.). The A.E.G. automatic control de- vice was fitted, for the purposes of demonstration, to an M.A.N., type KZ70/120, five-cylinder Diesel engine which develops 5,500 B.H.P., at 135 r.p.m. Orders are passed from the bridge in conventional manner, via the engineroom telegraph, but instead of being read on the telegraph by the engineer who would then move to his controls to effect the ma- neuver, the orders are passed electrically to an order transformer, split up by an A.E.G. unit, re- lated to one another and then activate the various functions of the engine by hydraulic mechanism.

A remotecontrol system for ships’ propelling machinery has been introduced by Messrs. Richard- sons Westgarth & Co., Ltd. [121 who have a p proached the problem of control from three sta- tions. The normal conventional control station local to the engine is retained, alternative stations being on the bridge and at a centralized p i t i o n in the engine room. The system is principally electrical, but the method may be readily undertaken using pneumatic actuators.

MISCELLANEOUS

Extensive research is still being camed out on free-piston gas turbine machinery and a paper by Herbert and Milne [13] contains some very inter- esting thoughts for the future. In considering future development of the gasifier, the authors show that it is possible to achieve an increase of power of 45 percent with certain modifications, and that a net reduction in the unit cost of the gasifier can be anticipated, in spite of the increased output, and consistent with the establishment of the highest standards of reliability. It is also claimed that the increase in power is achieved with a modest in- crease in pressure and no increase in temperature, while the volume flow at the turbine inlet remains substantially constant. This means that only the transmission cost rises and there is no appreciable increase in the cost of the gas piping or turbine, with an increase in unit output of the gasifier. Since the cost of the transmission does not exceed 30 percent of the total cost of the main machinery, even when a controllable pitch propeller is used, the achieve- ment of a 45 percent improvement in gasifier output permits a reduction of not less than 25 percent in the total costfiorse-power of the main machinery and stem gear.

In view of the current demand for single-screw machinery of 20-30,000 S.H.P. for tankers and bulk carriers of up to 130,000 tons deadweight, the authors have considered the potential of free-piston machinery far such powers. In a power station under construction in France, power is to be pro-

vided by 12 twin gasifiers. Each twin gasifier unit is to be initially rated at 2,625 G.H.P. as compared with the current rating of 1,250 G.H.P. for a single unit. This represents an increase of 5 percent and is achieved without increase in thermal loading due to the reduction in scavenge loss brought about by trimming.

A marine set using ten such twin gasifiers would currently develop 21,000 S.H.P. and following the process of evolution, could eventually produce more than 30,000 S.H.P.

A preliminary design study of a 20-30,000 S.H.P. installation, arranged aft and suitable for a tanker or bulk carrier of 60,000 tons deadweight shows that the free-piston machinery compares very fa- vorably with large bore Diesels in respect of weight and space requirements.

The length of service life of tailshafts is dealt with by Heck and Baker U41. Various factors are dis- cussed that influence the length of service and practical means for improving life expectation are suggested. These include a stress-relief groove in the shaft at the big end of the taper, cold-working the shaft surface, increased pull-up of propeller on taper during assembly, testing the assembly for water-tightness, “spooning” and shortening the key- way in the shaft, increased stiffness and full struc- tural continuity in the hull abaft the after peak bulkhead, skew in propeller blades, ample propeller aperture clearances, correct number and spacing of shaft bearings and provision of water service to stem tube for use in sandy or silty waters when ordinary lignum-vitae bearings are fitted. Studies are reported on the life expectancy curves of a large group of ocean-going single-screw vessels with propelling machinery of 1,500 S.H.P. or more, of smaller groups including the Mariner type vessels and ships fitted with oversize tailshafts and of ves- sels in Great Lakes service. The problem of pro- pellers lost at sea is reviewed, and suggestions are offered for improving inspection procedures to re- duce in-service tailshaft failures.

A new additive for treating heavy fuel oils used in marine and industrial boilers and furnaces, known as Duramis Plus, has been introduced 1151. It is essentially a blend of phenolic products and organic bases, added to the fuel at a concentration of 0.1 percent by weight (one gallon to four tons). I t has four main actions, Firstly it disperses sludge present in the fuel tanks and pipelines and breaks down emulsions of the oil with salt or fresh-water. Secondly, it stabilizes the fuel against further break- down into the solid carbonaceous matter and heavy gums which form sludge. Thirdly, because treated fuel reaches the burner relatively free of those pieces that are hard to bum, atomization is more nearly complete, less excess air is needed for com- plete combustion, boiler efficiency is improved and there are fewer particles of partially burned carbon to form soot deposits or smuts. Finally, the organic

bL4 Moral Engimors Journal. August. 1964

SHIPBLDR. AND MAR. ENG.-BLDR. PROGRESS IN MAR. ENGRG.

bases in the new additive reduce the corrosive effects of sulphur trioxide (produced when sulphur impurities in the fuel are burned) both by inhibit- ing its formation and by neutralizing it when formed. A vertical, two-stage, two-crank air compressor

has been designed for Diesel engine starting duties by Messrs. G. & J. Weir, Ltd. [l6]. The machine is claimed to be simple to maintain and to have a long working life. There is only one size and it has a stroke of 6 in., a first stage bore of 10% in. and a second stage bore of 4% in. It is suitable for a range of capacities covering the most common marine re- quirements, the output depending on the speed and power of the prime movers. For instance, when de- livering 175 cu. ft. of free air per minute at a dis- charge pressure of 450 lb. per sq. in. (gauge) an 80-H.P. motor is recommended.

Economics is an important aspect of engineering and a potentially valuable tool a t every level of design. A paper by Benford [17] outlines the prin- ciples of engineering economy, applied to decision- making in ship design. It explains the several available economic criteria and emphasizes rational methods for selecting criteria suitable to various economic circumstances. The author also stresses the importance of stipulating reasonable rates of interest and explains, in this regard, the influence of taxes, inflation, borrowed funds and relative risk. Captive fleet considerations, fast tax write-off, short cuts in cost studies, and the importance of intangible considerations are also discussed.

REFERENCES

El] ‘‘Shore Trials of Marine Steam Turbine Machinery,”

actions of the Institute of Marine Engineers, April, 1963. [ Z ] ”Some Results Obtained from a Fuel-oil Water-wash-

ing Plant in Studies of the Fouling of Marine Super- heaters,” by W. Tipler, MA.; Transactions of the Institute of Marine Engineers, December, 1963.

131 '"Rue Decades of Research and Development on the Doxford Engine,” by P. Jackson, MSc.; Transactions

by T. W. F. Brown, C.B.E, D.Sc., S.M., A.R.T.C.; TIXIIS-

of the North-East Coast Institution of Engineers and Shipbuilders, November, 1963. “The Turbo-charger and the Supercharging of Lnrge Two-stroke Diesel Engines,” by H. E von Gunten and C. Gyssler; Transactions of the North-East Coast In- stitution of Engineers and Shipbuilders, April, 1963. “Some Factors Influencing the Life of Marine Crank- shafts.‘‘ by s. Archer, M.Sc.; Transactions of the Insti- tute of Marine Engineers, November, 1963. “N.S. Savannah Operating Experience.” by J. H. Mac- Millan, D. C. MacMillan, J. E. Robb, H. I. LilI, Jr., and R. 0. Mehann; Transactions of the American Society of Naval Architects and Marine Engineers, November, 1963. “Design Study for Marine Propulsion Machinery In- corporating a Boiling Water Reactor, as Tendered in 1960,” by A. W. Davis, D.Sc.; Transactions of the Institute of Marine Engineers. Joint Panel on Nuclear Marine Propulsion. May, 1963. “Eclects of Prolonged Stress Relieving Treabnenb on the Mechanical Properties of Reactor Pressure Vessel Steels,” by B. Watkins. D. S. Wood and R. W. Nichols; British Welding Journal, February, 1963. “Progress in Automation,” by R. Munton. B.S., J. McNaught and J . N. Mackenzie; Transactions of the Institute of Marine Engineers, 23 April, 1963. “Mahout-A Cargo Liner with Bridge Control of the Main Engine;” The Shipbuilder and Marine Engine- builder, August, 1963. “Automatic Control for an M A N . Engine;” The Ship- builder and Marine Engine-builder, August, 1963. “The Richardsons Westgarth Remote-control System for Ships’ Propelling Machinery;” The Shipbuilder and Marine Engine-builder, November, 1963. “The Application of Free-piston Gas Turbine Ma- chinery to Marine Propulsion,” by c. w. Herbert and G. F. Milne, B.S.; Transactions of the Institute of Ma- rine Engineers, October, 1963. ‘Marine Propeller Shaft Casualties,” by J. W. Heck and E. Baker; Transactions of the American Society of Naval Architects and Marine Engineers, November, 1963. “Keeping Fuel Oil Clean;” The Shipbuilder and Ma- rine Engine-builder, December, 1963. “Weir Starting-air Compressor;” The Shipbuilder and Marine Engine- builder, November, 1983.

[17] “Principles of Engineering Economy in Ship Design,” by Harry Benford; Transactions of the American So- ciety of Naval Architects and Marine Engineers, No- vember, 1963.

GIBBS & COX, INC. NAVAL ARCHITECTS AND MARINE ENGINEERS

NEW YORK AN fWAL o c y o ~ m fwlorfR

Naval Engimrc Journal, August. 1964 645