It is not necessary to take out any of the plungers to put in one of the packing rings; if the cotters and nuts are removed, and the engine turned round, the plungers will remain on the top centre, and there is ample space to get the glands down to insert one of the making-up packing rings.

Great care must be taken to prevent the plungers being scratched or bruised, in order to avoid rapid wear of the leather.

The drain cocks of the cylinders, slide jackets, &c., should remain open when the pumps are standing idle.

The pumps should be turned every day, and a little oil should be placed in the bearings and cylinders from time to time.

The cup for the injection oil, and the wire gauze strainer over the air-inlet valve, should be frequently washed in hot water, to keep them free from dust and cloggy oil.

The greatest possible care must be exercised to keep dirt away from the lubricators, valves, and valve seatings.

To draw the large plunger for examination.-Remove the top cover, then put the engine on its bottom centre; slack the gland; take out the split pin and draw the cotter; put the engine on the top centre; insert a piece of wood between the bottom of the plunger and any fixed part of the machine; turn the engine towards the bottom centre and clear the plunger from the rod. Insert a washer, or piece of plate, over the hole in the crosshead, and turn the engine towards the top centre till the plunger is gradually forced out of the barrel.

To draw the small plungers.—The pump must be lifted out of the tank, or else the pump and tank must be lifted together. This operation is only necessary when a thorough refit is to be made. The glands of the pump are packed with ribbon metallic packing, a weighed quantity of which is made into a ring in a mould supplied for the purpose.

The only working leather in these pumps is that in the top of the plunger; it consists of a flat ring, turned on edge and stretched over the top of the plunger into a recess; it is backed by a metal packing ring. This leather is cut to a gun-metal template, from a flat piece of leather, by means of an ordinary trammel knife.

(Four-stage

Brotherhood's Air compressing Pump Type, 1905).—This machine is steam-driven, of construction as shown in Fig. 88.

The air is compressed in four stages, and is cooled between each stage in intercoolers. The normal working air pressure produced is 2500 lbs. per square inch. The action of the pump is shown diagrammatically in Fig. 89. The first intercooler

coils are attached to the front cover of the base casting of the machine, and can be removed without disturbing any other parts. The second, third, and fourth intercoolers are fitted in the pump casing.

L.P. Pump Barrel
Leather.

Fig. 88.-Brotherhood's Air-compressing Pump (Four-stage Type, 1905).

All coolers are formed of solid drawn copper tubing, and all joints are metallic. The double-acting circulating water pump is driven direct from the crosshead; this pump will lift water from a depth of 6 feet below the base of the compressor without requiring to be charged. The pump will discharge against a head of 8 feet quietly and efficiently.

The compressor is designed to work efficiently without injection water, the air being completely cooled after each

compression; but the necessary fittings for water injection are provided.

Compressors of this pattern have been supplied to all classes of modern vessels in H.M. Navy.

Instructions for Testing (see Fig. 89). Remove the non-return valve and relief valve on the air outlet, and connect to the watertesting pump. Gag the relief valves on first, second, and third intercoolers. Open the drain cock on the first intercooler. Remove valve A, one valve B, valves C, D, E, and F, and their covers, also valve H. Remove the crosshead; the thrust of the plungers is then taken by the pump itself, and not by the working parts of the engine.

(1) Pump to 4000 lbs. per square inch, testing the fourth cooling coil, high-pressure barrel and plunger, and valve G. N.B.-The high-pressure ram will be forced in.

(2) Release the pressure, remove the valve G. Insert valve E. Pump to 2500 lbs. per square inch, testing the third cooler coil, high-pressure cover, and valve E. N.B.-The high-pressure ram will be forced out.

(3) Release the pressure, remove the valve E. Insert valve C. Pump to 1000 lbs. per square inch, testing the second cooler coil, low-pressure barrel and plunger, and valve O. N.B.-The lowpressure ram will be forced out.

(4) Release the pressure, remove the valve C. Pump to 500 lbs. per square inch, testing the connecting pipes, and valves B.

Insert valve B. first cooler coil,

(5) Release the pressure, remove one valve B. Insert valve A. Pump to 150 lbs. per square inch, testing the low-pressure cover and valve A.

Packings.-Leather packings, cut from flat sheets and not pressed or moulded, are used. The flat sheet should be pared and planished to the required thickness; it should then be nailed on a wooden block, which is placed in a lathe, and the disc cut out by a knife tool to the bronze template provided. The highpressure plunger leathers are soaked in warm water for a few minutes to render them pliable; they are then placed on a cone tool, whence they are transferred over the plunger head, and are closed into their proper grooves by a sleeve tool.

To Draw the Large Plunger for Examination.-Remove the top cover, unscrew the nut of the connecting link under the crosshead, put the engine on the top centre, screw eyebolts in the plunger top, and lift with tackle.

To Draw the Small Plungers. Unscrew the high-pressure cover and the nut at the bottom of the plunger stem; put the engine on the top centre, and lift the plunger out by hand.

se

tions.-Before starting the engines when they have not been at work for some time, see that all nuts and cotters are properly adjusted and cured by their set screws, lock nuts, or split pins. See that the nuts and split pins securing the springs on the guide spindles of the air-inlet valves are in their places, and that all the springs are

free

Air Outlet

Fig. 89.-Brotherhood's Air-compressing Pump (Four-stage Type, 1905).

to the air-inlet valve strainer immediately the engine commences to work.

Before starting the engines against a pressure in the reservoir, open the relief screw-plug valve on the top of the pump, and leave it open till the engines are at work.

The drain cocks may be closed when the engine is fairly at work. Fresh water is preferable to salt for injection water, and should always be used, if obtainable.

Fig. 90.-Belliss' Air-compressor
(Two-stage Type).

Sperm oil is the most suitable for the internal lubrication of the pumps.

If the circulating water and injection lubrication are sufficient, the air pipes leading from the pumps to the separator columns, or from the pumps to the reservoir, should not be much above the temperature of the circulating water.

If the pumps do not appear to be working efficiently, close the outlet valve of the separator column for a short time, and observe if the pressure rises quickly. See that the valves in the circulating water pipes are open, and that the water is flowing through the casings. Try the pressure gauges occasionally by their stop and relief valves to make sure they are not inactive.

If the pump should stop when working at its maximum steam pressure, one of the packings may have failed, or a valve may have become obstructed; the cause of the stoppage should be found and remedied. A faulty leather can be identified by the

location of the air leak.

Messrs. Brotherhood make a single-stage compressor fitted for supplying air at a pressure of 50 to 80 lbs. per square inch, for cleaning the fire sides of the tubes of water-tube boilers. The working parts are enclosed and fitted with forced lubrication.