Page 140 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

122 Major Process Equipment Maintenance and Repair

Figure 3-4 Typical action of a horizontal duplex pump.

designated as 2 X 3 has a plunger diameter of 2 in, and a stroke length of
3 in. For a direct-acting pump, the same convention is followed, except
that the diameter of the drive piston precedes the liquid-end-element di-
ameter. For example, a pump designated 6 X 4 X 6 has a drive-piston di-
ameter of 6 in., a liquid-piston diameter of 4 in., and a stroke length of 6
in.

Llquid-End Components

All reciprocating pumps contain one or more pumping elements @is-
tons, plungers, or diaphragms) that reciprocate into and out of pumping
chambers to produce the pumping action. Each chamber contains at least
one suction and one discharge valve. The valves are simply check valves
that are opened by the liquid differential pressure. Most valves are spring
loaded.
The liquid end is that portion of the pump that does the pumping. Ele-
ments common to all reciprocating-pump liquid ends are the liquid cylin-
der, pumping element, and valves.