"Oil Fuel Notes"

The following notes on oil firing have been transcribed from the notebook of Arthur Clark, an Engine Room Artificer in the Royal Navy - the notebook is in the possession of his grandson, David Clark (david.clark24@ntlworld.com), who also served as an ERA, but at a slightly later date. Arthur Clark did his training at HMS Fisguard IV (a "stone frigate") - the notebook is dated October 1916. He would later go on to serve in the light cruiser HMS Cambrian.

It has been transcribed word-for-word, with the few notes from the editor entered [in square brackets] - as much as possible, the same punctuation and "look" of the original has been maintained. Images (about 150k each) of the complete notebook will be found at the end.

David Clark has also written an excellent summary which will make his Grandfather's notes a bit easier to follow:
Introduction to Boiler Room Operations.

This page is dedicated to the memory of Arthur Clark.


(click on the photo for an enlargement)

A. Clark E.R.A.

Oil Fuel Notes

October 1916

H. M. S. Fisguard IV


[Cover] [inner]

(click on the photos for an enlargement)

Ques. I Trace the course of oil from the tank to the sprayer and name and name all the fittings it has to pass? Ans. 1 1. Sluice valve on tank

2. Tank suction strainer

3. Screw down non return valve (S.D.N.R.)

4. Pump suction valve

5. Pump

6. Spring loaded relief valve

7. Pump delivery valve

8. Air vessel

9. Cold filters

10. Heater

11. Hot filters

12. Emergency valve.

13. Thermometer

14. Sprayer master valve

15. Sprayer.

Ques. II What is meant by flash point and what is the minimum flash point allowed in the R.N.? Ans. 2 The temperature at which oil gives off vapour in such quantities as to become inflammable. Min. F.P. 175º Fahr.
Ques. 3 What is meant by "Ignition Point" and what relation has it to F.P? Ans. 3 The temperature at which oil takes fire and continues to burn when a light is applied. It varies generally being about 40º above F.P.
Ques. 4 What is meant by "viscosity". How is it reduced? Ans. 4 The sticking together of the particles of oil. It is reduced by applying heat to the oil.
Ques. 5 Why should oil be heated? Ans. 5 By raising the temperature a more efficient atomising is obtained, the oil becomes more the consistency of water and therefore spraying in finer particles, which mix more readily with air.
Ques. 6 At what temperature should Texas oil be burnt? Ans. 6 About 200º Fahr.
Ques. 7 What is the most essential item to burn fuel oil efficiently? Ans. 7 To mix air with the oil before combustion takes place.
Ques. 8 What machinery in the boiler rooms should be started first when sufficient steam is generated in the boilers? Ans. 8 The fan engines.
Ques. 9 What should your aim be when regulating the fans? Ans. 9 To keep the air pressure at "smoking point", so that any decrease will cause distinct smoking, when any increase will give a clean funnel. If the air pressure be still further increased, white smoke will be seen at the funnel. Black smoke is less efficient than white and is only excusable when changing over boilers or when suddenly increasing speed. White smoke is excusable when shutting off boiler altogether.
Ques. 10 What means are provided to ascertain whether smoke is being made? Ans. 10 Glass windows, mirrors and sight holes in the furnaces.
Ques. 11 And how are they fitted? Ans. 11 The windows are fitted in the uptakes and smoke boxes, one at each end , behind the further hangs a light, and the mirrors are so fitted that when little or no smoke is being made, the light is reflected and can be seen from the stokehold plates. A sight hole is placed under the steam drum to enable any smoke or sparks to be seen at once.
Ques 12 What range of pressure is required for a good spray? Ans. 12 From 35 to 150 lbs. Oil will spray at a pressure of 20 lbs. but will be an inferior spray.
Ques. 13 How should a battery of sprayers be worked so as to spray most efficiently? Ans. 13 As far as possible regulate the steam pressure by altering the oil and air pressures and not by shutting off or relighting sprayers: regulate the spindle of each sprayer to a cone full of flame and have the same amount of flame in each cone. The number of sprayers used should be such that for the normal working an oil pressure of 60 - 70 lbs. is required; this allows plenty of latitude for manoeuvring without shutting or relighting the sprayers.
Ques. 14 How should a sprayer be set? Ans. 14 If a steel air cone is fitted in the boiler, the cap nut of the sprayer should be ¾" from the small end of the cone. The flame should strike centrally and about ½" back from the lateral slots. If a brick-lined tube is fitted, the face of the cap nut must be a fixed distance from the furnace side of the flame ring. This distance is different for each different sized tube and the gauge must be made from the drawings supplied.
Ques. 15 What causes the sprayer to drip? Ans. 15 (1) Leakage between the cap and gunmetal body, due to being improperly cleaned when put together.

(2) Slight obstruction in the orifice of sprayer due to a burr.

(3) Slight defect of the central punch point of spindle due to a burr.

Ques. 16 What precautions should be taken when cleaning a sprayer? Ans. 16 Never use anything harder than copper wire for cleaning the holes in the cap, see that the joints of the body and cap are perfectly clean and free from burrs.
Ques. 17 Is the angle of the oil spray important, how should it be set? Ans. 17 (1) Yes (2) It should be adjusted so that the tube or cone is well filled with flame without overheating and without any oil dripping from lateral slots.
Ques. 18 What is meant by and what are the causes of an overheated cone? Ans. 18 When the cone or tube becomes red hot, they are said to be overheated; and is caused by insufficient air passing through the cone.
Ques. 19 What is meant by and what are the causes of a wet cone? Ans. 19 The inner surface of the cone being covered with oil due to:- the temperature of oil too low; too much air; angle of spray not quite correct: correct angle by altering spindle.
Ques. 20 What are the causes of oil dripping from the cone slots? Ans. 20 Cone too cold; oil too cold; sprayer set incorrectly or defective.
Ques. 21 What are the causes of the flame becoming extinguished? Ans. 21 Water in the tank reaching the sprayer; air passing over from the air vessel.
Ques. 22 What effect has water on the spray? Ans. 22 Air cone gets coated with a frothy mixture of oil and water. Cones become cold and drip badly. Boiler tubes get coated with a deposit. If possible change over to another tank.
Ques. 23 How is air admitted to the Air Vessel? Ans. 23 By closing down the pump suction valve and opening the "shifting cock". When sufficient air has been admitted, close the cock and open the suction valve. In some cases it is only necessary to open the "shifting cock."
Ques. 24 Why keep a steady pump pressure? Ans. 24 To ensure a steady combustion of fuel.
Ques. 25 What is meant by the term "Backflash"? Ans. 25 The flames being forced from the furnace into the stokehold. This is caused by an explosion of vapour inside the furnace giving for a time higher pressure in the furnace than in the stokehold. It may be caused by an accumulation of vapour in the furnace being ignited when the requisite amount of air is introduced into it, or by the intermittent supply of oil and air.
Ques. 26 What precautions should be taken to avoid the effects of a "Backflash"? Ans. 26 Keep clear of the furnace sight holes as much as possible when lighting up or altering speed. The chance of a Backflash when burning oil over coal is practically nil.
Ques. 27 If steaming at "FULL SPEED" and ordered to "STOP" what would you do? Ans. 27 Ease [?] oil pressure to prevent boilers from blowing off and ease fans. If by doing so the oil pressure should fall below 30 lbs., shut off some sprayers.
Ques. 28 What precautions should be taken when easing down? Ans. 28 Ease oil pressure, then air pressure. Keep fans running for some time after the oil is shut off to blow any vapour which may be remaining out of the furnace.
Ques. 29 What precautions must be taken when changing over filters? Ans. 29 Open out to clean filter cautiously, allowing the oil pressure at the boiler to rise gradually, also give orders to stand clear of the furnace fronts when opening out, to avoid the effects of a Backflash should it occur, due to the sudden rise of oil pressure.
Ques. 30 What precautions must be taken when entering a stokehold where oil is being burnt? Ans. 30 Always see that the air lock door farthest away from you is shut before attempting to enter air lock.
Ques. 31 How would you proceed to burn oil over coal? Ans. 31 Put steam in the heater and raise the temperature of the oil to ignition point, so as spray with a pressure of 35 lbs with the spindle open ½ turn. Gradually increase the pressure in the system to that ordered and at the same time gradually open the spindle to 1 ¼ turns. Increase the air pressure in proportion.
Ques. 32 What should be the conditions of the fire when burning oil over coal and what special precautions are necessary when firing up? Ans. 32 The same was when burning coal alone. Level fires 5-7 inches with frequent regular light firing. Coal must not obstruct any of the flame. Do not fire up green coal in front of the cone but push over live coal and fire upon flame from whence live coal was taken.
Ques. 33 What should be done with regard to cleaning fires when burning oil over coal? Ans. 33 Fires should be cleaned as often and as thoroughly as when burning coal alone. Oil should be shut off on each separate furnace in turn to enable fires to be cleaned thoroughly and well.
Ques. 34 State some oils to be used as fuel? Ans. 34 Russian, Texas, Borneo, Burmah, Rumanian, Mexican, Persian, Blast furnace, Scotch shale.
Ques. 35 Through what process does oil go through before going into the furnace as fuel? Ans. 35 Through a form of distillation to take off the light oil, in order to obtain a flash point.
Ques. 36 What is the chief chemical impurity in oil fuel? Ans. 36 Sulphur.
Ques. 37 How does the single orifice sprayer differ from the Duplex? Ans. 37 The S.O.S. has only one exit hole and either 1, 2 or 3 tangential holes. The Duplex has two exit holes and 9 tangential holes.
Ques. 38 Why are tangential holes drilled in the cap of the sprayer? Ans. 38 To give the oil a rotary motion inside the spraying chamber of the cap, so as to enable it to leave the exit hole in the form of a spray.
Ques. 39 What is the output of a sprayer? Ans. 39 The number of lbs of Texas oil used per hour at a temperature of 200º Fah. and at a pressure of 150 lbs/sq."
Ques. 40 Why is a special lighting up sprayer used? Ans. 40 Because the output of oil from any other sprayer is more than can be accommodated by the supply of air without the use of the fans and therefore dense clouds of smoke is the result of using a large sprayer and higher pressure.
Ques. 41 What should be done with regard to raising steam in an oil fuel boat when in open anchorage? Ans. 41 Always have lighting up sprayer shipped and ready for use.
Ques. 42 How is pulsation caused and what can be done to remedy it? Ans. 42 Causes. Insufficient air passing through from small end. Too high an oil temperature.

Remedies. Close in stokehold ends of air cone slots; reduce temperature of oil so as to give an efficient spray, reduce angle of spray by closing down spindle, advance sprayer slightly towards furnace. It some cases it may be remedied by momentarily opening the cleaning doors of each sprayer in turn.

Ques. 43 How should a sprayer with steel air cones be set? Ans. 43 By using a gauge ¾" thick, placing it between the sprayer cap nut and the small end of cone. Where a brick-lined tube is fitted a suitable gauge is used, placed against the furnace side of the flame ring. The sprayer should be placed so that the cap nut touches the gauge. Set the sprayer central by the eye.
Ques. 44 What is the construction of the air cone and Brick-lined tube? Ans. 44 The cone is usually made up of 3/16" sheet steel of suitable length and diameter; in the large end, slots are cut to give the air rotary motion which causes a thorough mixture of oil and air on leaving the large end. The expenditure of these cones is considerable, owing to their being burnt away at the furnace ends. A brick-lined tube has therefore been introduced. In this arrangement, the plain and slotted parts, are, as it were telescoped and instead of being conical the tube is cylindrical, beyond this is a brick tube built up; this is of course impervious to the flames. The spray strikes a little over the centre of the plain portion, is heated to burning point and mixes with the air which comes from between the plain and slotted parts. By the time it gets well into the brick tube the mixture is thoroughly alight and so continues into the furnace. The uses of the cone and tube are: that they not only mix the air with the oil, bringing it to ignition point but ensure the oil being well ignited before entering the furnace.
Ques. 45 What are the fittings on a heater? Ans. 45 Oil inlet and outlet, steam inlet and drain; steam pressure gauge and spring loaded relief valve. (Long valve)
Ques. 46 Explain the method of testing a Heater? Ans. 46 Fill the heater with steam and allow to condense, thus forming a partial vacuum. Put on oil pressure of 150 lbs through system. Break vacuum and draw off water watching for signs of oil.
Ques. 47 What precautions must be taken to ensure the thermometer showing the correct temperature? Ans. 47 See that the mercury cup is filled with mercury.
Ques. 48 What is the cause of the oil fuel pump running away with a low vacuum on gauge? Ans. 48 Tank empty.
Ques. 49 What is the cause of the pump running away with a high vacuum on gauge? Ans. 49 Tank strainer choked or too many pumps on one tank.
Ques. 50 Why is heavier and better brickwork required for oil fuel than for coal furnaces? Ans. 50 Because the heat in similar furnaces is roughly as 5 to 4.
Ques. 51 What steps should be taken to preserve the brickwork? Ans. 51 See that the bolts do not slack back, fit check nut where necessary, use plenty of sand and fireclay and also glass as necessary. Enter furnace after each steaming and fill up cracks. If the beds of the furnaces give trouble, bottles or broken glass scattered on will give good results.
Ques. 52 What is generally the cause of sight hole and smoke window glasses cracking? Ans. 52 Small cooling holes in the furnace side of glass choking.
Ques. 53 How may a draught be created in the funnel when lighting up? Ans. 53 If possible revolve the fans by hand. Light up bogey placed in furnace the night before, to warm the air. Throw a piece of lighted waste down the funnel.
Ques. 54 What are oil fuel joints made of - How should they be tested? Ans. 54 They should be made metal to metal if jointing material is required, then asbestos sheeting covered with soft soap should be used. Hydraulic leather is used for joints on the oil tanks. The system should be tested to 150 lbs sq. inch, after joints have been made.
Ques. 55 If on patrol duties with boilers banked, what precautions would you take in order to be ready for a sudden "FULL SPEED"? Ans. 55 Keep water low in boilers to prevent priming. Raise steam every 4 hours to working pressure using a different sprayer each time.
Ques. 56 What would be the result of a flap slipping down in the air supply trunks when steaming at high speeds? How can this be avoided? Ans. 56 A violent backflash, owing to the sudden decrease of air. The furnace would fill with smoke due to unconsumed vapour and air, and the steam pressure would drop rapidly. It can be avoided by seeing that all the flaps are securely fastened before lighting up.
Ques. 57 What precautions must be taken when sounding the tanks? Ans. 57 See that all sluice valves and non-watertight bulkheads are open, (if so fitted). See that deck plate plugs of the breathing pipes are lifted when cleared for action.
Ques. 58 How would you test for water in an oil tank. Ans. 58 By passing a strop [strip?] of sensitised paper round the end of the sounding rod and lowering it into the tank. The paper will become bleached by the presence of water in the tank.
Ques. 59 How does the spray vary with the number and area of the tangential holes. Ans. 59 An increase in the number or area of the tangential holes reduces the angle of spray.
Ques. 60 Compare 10 lbs of oil with coal? Ans. 60 10 lbs of oil = 14 lbs coal (Heat value 1.4)
Ques. 61 What apparatus is used for determining flash points of oil fuel? Ans. 61 The Pensky-Martens Apparatus.
Ques. 62 What are the advantages of oil over coal? Ans. 62 Superior evaporative powers; ease of shipment; reduction in the number of stokers required; less stokehold duties; absence of ashes and coal dust; no opening of furnace doors; cleanliness; ease of control; capability of forcing.
Ques. 63 What are the disadvantages of oil fuel? Ans. 63 Dependance on foreign supplies and increased cost.
Ques. 64 What should be done in the event of a boiler running short of water? (Where oil fuel is burnt) Ans. 64 Immediately shut off the oil supply to prevent tubes getting burnt.


The object of the air vessel is to assist in maintaining a continuous pressure at the sprayer and thus avoid pulsation.

It is not advisable to keep too much air in the vessel, as when oil pressure is reduced, the air expands and should it fall below the edges of the holes in the internal pipe, it could be discharged to the burners and extinguish the flames.


When liquid fuels are used there is much more intense heat than with coal and all iron and steel work should be protected by bricks, if in the vicinity of the flames. With coal and oil the bars should be kept well covered with coal. There is generally no deposit on the tubes with liquid fuel, but if air supply is insufficient a small deposit may be found. This is reduced by forcing the boilers with sufficient air pressure.


Is the rapid chemical action accompanied by the rapid evolution of heat. In the sense of the word "Combustible" it means combining with the oxygen of the air so as to produce heat rapidly.


Means the visible products of combustion escaping from the funnel into the air. This colouring matter is carbon in a very finely divided state carried off mechanically out of the furnace into the funnel. The number of sooty particles determines the colour of the smoke.


Whatever incombustible substances remain after combustion is completed are called ashes, irrespective of composition. As a rule a large proportion of silica and alumina is found in ashes.

Clinker is formed by fusion of the impurities of the fuel.

Specific heat of ashes .215.





Wipe all oil on deck plates and air boxes as soon as possible. Do your utmost to prevent oil from reaching the bilges and make good any leaks as soon as discovered. Report at once all leaks.


Oil pressure and air pressure should be enough to produce the correct amount of smoke.

Fluctuations should not be more than 5 lb / sq."

Oil temperature - 200 Fahr. unless otherwise ordered.


Regulate the pressure in the system by the relief valve and not the speed of pump. The pump should work slowly.

STEAM PRESSURE should be kept constant as ordered: any alteration in pressure due to variations in the speed of engines should be made by altering the oil pressure and air pressure. Do not shut off any sprayers unless absolutely necessary.

HEATER. Temperature of the oil is to be regulated by the steam valve with the drain just eased. Test drain water every half hour by closing down to feed tank and drawing off water from the test cock on the water collector. Water must always be run to bilge when first putting steam on the heater, until it is certain that no oil has leaked through while standing. When shutting off heater always open drain to bilge and leave open.

FILTERS Report at once any choking and change over to clean filter and see that the choked filter is immediately cleaned.

SPRAYERS 1 ¼ turns open should be the mean working position of the spindle. Should choking of a sprayer occur, remove sprayer and clean it; ship a spare one if required; if not ship a blank nut on the end of supply pipe to the sprayer which has been removed.

BILGE This must be inspected at least once a watch and reported. Before watchkeeping ceases, every part of bilge should be inspected and any accumulation wiped up.


Flush with water and pump out the surface oil by means of a flexible suction hose.

GENERAL Keep sand boxes full of sand to put out any small fire which may occur; have good spanners handy to make good any leaks. Always use glass or shade goggles when cleaning cones. Report heater drain every watch also bilge, whether free from oil or otherwise.




Rigid cleanliness must be insisted upon, particularly regarding the wiping up of oil on the deck plates, air boxes etc.

A small fire should be smothered with sand, fire clay or a piece of damp cloth. If a fire cannot be reached by this method, direct water on to it, to cool down the oil, if beyond this measure, shut off the oil supply , extinguish coal fires if necessary, by water, stop fans, close all air doors and draught plates, send hands out of compartment, close down everything, cover funnels and ventilators so as to smother fire by lack of air. In addition the instruction laid down in Art. 351 Steam Manual and Chapter to Stokers Manual, shall be strictly observed.


Before lighting up see that all the combustion space is free from oil; all air flaps in good working order and all joints tight. The principle aim is to make as little smoke as possible and a special sprayer is used.

Fix up the tube by placing it into the cone with the flexible ends connected one end to the master valve and the other to the sprayer. After this has been done place a piece of lighted waste in cone (the waste having been soaked with oil). Start hand pump and keep up a pressure of 50 - 60 lbs having the master valve and sprayer open just wide enough to keep sufficient oil spraying onto the lighted waste in the cone, to prevent it burning away.

When the oil passing through the tube takes fire you can dispense with the waste and then open the master valve wide. At first sign of steam open all steaming connections on the system (i.e.) steam to heater, fan engines, oil fuel pumps etc. As soon as possible start the fan engine and O.F. pump and as soon as the temperature of the oil in the heater is raised to that required, light up another sprayer, disconnect U tube and replace by steaming sprayer.


When pumping up oil tanks allow 5% for expansion. Sounding rods should be marked full when tank is 95% full. No fires of any description should be allowed near tanks, filling pipes, or vapour escape pipes while the tanks are being filled.

Before any tank is entered, it is to be pumped out as dry as possible with the oil pump and then with the hand pump. It is then filled with water from the fire main to expel foul air and then pumped out, the operation being repeated if thought necessary. Wipe out with oakum or sponge not waste and finish off with old bunting. If much oil clings to the side of tank, wipe down with shale oil if possible.


Ease fans as necessary, close air flaps to cone, get asbestos torch well soaked in oil and well alight before turning on the oil. Place the torch soaked in oil just under the cap nut of sprayer and turn on oil. The oil should not be allowed to flow into the furnace because if the furnace lining were not at a temperature to ignite the fuel instantly an explosive mixture of oil and air might be formed which would lead to serious results.


A single orifice sprayer consists of a gunmetal body and spindle bush, steel spindle and cap, gunmetal cap nut and necessary glands and nuts. The spindle screw[s] through the bush and has a centre punch point. The cap has one exit hole and either 1, 2 or 3 tangential holes and when the spindle is in the shut position there is a clearance of 2/1000" (two thousandths) between the tip of the spindle and the inner edge of the exit hole. As the spindle has this clearance it does not become burred through being closed down on the exit hole. The glands should be packed with asbestos and covered with soft soap. The wheel is graduated into quarters and eights.

In the original, there follow 9 pages of drawings - they may be found below, clicking on the small thumbnails for an enlargement, following the 26 pages of text-only.

Scans of the Notebook

(each is about 150 kb)

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Oil Fuel Filter (Page 27)

Steam Oil Heater (Page 28)

General Arrangement (Page 29)

U Lighting-Up Tube (Page 30)

Single Orifice Sprayer (Page 31)

Brick-Lined Tube (Page 32)

Oil Fuel System of HMS Cambrian (Page 33)

Steam Supply Pipes (Page 34)

Dial for Mechanical Stokehold Telegram, as fitted in HMS Royal Sovereign (Page 35)

Last Updated: 5 May, 2002.

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