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The steam ends of pumps require the same lubrication as the cylinders and valves of engines. Intermittent lubrication is never to be recommended even for slow running pumps. Sight feed oil cups are always preferred.
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A sight feed lubricator connected to the steam pipe below the throttle or to the steam chest is automatic in its operation. All that is necessary is to fill it. When the speed increases the feed increases and when the pump stops the feed stops. An oil hand pump is also desirable to introduce a mixture of oil and graphite, about 10 per cent. of graphite.
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The water end stuffing-boxes of a pump may be lubricated by putting a heavy grease on the piston rods, or good cylinder oil may be used when grease is not at hand. Some of the grease works into the stuffing-boxes and furnishes better lubrication than can be obtained by the water alone. Care must be used not to use too much oil as it must not go beyond the stuffing-boxes and contaminate the water.
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When a pump works properly under high pressures and fails to work under low pressures, the difficulty is generally found in the lift of the valves.
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When the water end of a pump is known to be in good condition failure to run properly will in all probability be discovered in the steam end, and in single cylinder pumps the fault is generally caused by clogging of the auxiliary valves and ports. Sometimes pieces of packing break off and get into these small ports, thus shutting off the admission or release of steam.