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When one side of a duplex pump makes a quick stroke it indicates either that the stuffing-box gland of the opposite side is too tight or that the packing in the cylinder of the side making the quick stroke is wearing out or has, perhaps, given way. A broken discharge or suction valve will also cause a “jerky“ motion of the pistons.
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Pumps should be examined frequently in order to know what parts are beginning to wear and how fast the wear is taking place. When this is done the worn parts can, in the majority of cases, be taken out and replaced by new ones before they give out entirely, thus avoiding delay, but what is better, duplicated parts kept on hand ready at a moment’s notice.
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The regular inspection of the screen in the separating chamber in the suction pipe renders frequent inspections of the interior of the pump unnecessary, the inspection previously alluded to is generally easier and more quickly done.
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Considerable wear can and frequently does take place in a pump in the course of six months, and for this reason it is advisable to inspect the interiors at shorter intervals, say four months for general service pumps and once in three months for boiler feed pumps. More frequent inspections should be made when handling dirty water.
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When a pump has to run faster one week than the week previous in order to supply approximately an equal volume of water, the plungers and valves should be examined, because such behavior indicates leakage.