Zwicker's Revised Practical Instructor IN QUESTIONS AND ANSWERS for Machinists, Firemen, Electricians and Steam Engineers

PUMPS


| January/February 1996



Q. What kinds of pumps are there?
A. There are many kinds, but we consider only single action and double action for feeding boilers and general use.

Q. How many valves has a single action plunger pump?
A. Two valves, a receiving valve and a discharge valve.

Q. How many valves has a double action?
A. Four, two receiving and two discharging. The double action receives and discharges both strokes. This kind of pump has a steam cylinder on one end. Large pumps have eight, sixteen and thirty-two small valves on water cylinder, according to the size of the pump.

Q. Why do large pumps have many small water valves and not a few larger ones in proportion?
A. The reason the pumps have small valves is that the valves do not have to open as much as larger ones, consequently the pump does not loose the quantity of water each stroke as it would with larger valves.

Q. How are pumps set up and leveled?
A. Set the pump so the receiving is from the boiler and the discharge toward the boiler, put in the same size receiving and discharge pipe as tapped in the pump, so the pump can have a good supply and discharge. The pump is leveled with a spirit-level or a square and plumb line. To level a double-action pump, some level across the frame and along the piston; the other way is to take the valve chamber cap off the water cylinder and level the valve seats, so the valves will rise and drop plumb. To level a single action pump, take off the valve chamber caps and level both ways.

Q. How are the steam valves of duplex pumps set and adjusted?
A. Take off the valve chest cover, shove the piston against one of the cylinder heads and mark the piston rod with a pencil at the packing-box gland, then shove the piston against the other cylinder-head and make another mark, find the center between the two marks and move the piston until the center mark reaches the packing-box gland where the first mark was made. Or in other words plumb the lever that connects the valve rocker shaft and the piston. After this is done, see how the steam valve is for lead; if equal at both ends the valve is set, if not, adjust by uncoupling the valve stem at the coupling outside of the packing box, and turn to suit the adjustments in equalizing the 'lead.'