PUMP INSTALLATION AND OPERATIONS

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 PUMP INSTALLATION AND OPERATIONS

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Considerable attention must be paid to proper pump installation to ensure trouble-free operation. The following factors must be taken into consideration: 

INSTALLATION OF PUMP:

• The pumps should be accessible for inspection and maintenance and should include valves on both suction and discharge lines. they should be removed from areas that are subjected to flooding, water leakage, and corrosion; they should be located as close as possible to the source of supply and headroom should be provided for lifting the rotor and casing. If the pumps must be located in areas of high humidity, the motors must be designed for this purpose. 

• The pump is provided with a steel baseplate to which the pump and motor are attached. This baseplate must be bolted securely to the foundation. In most cases, larger bases are grouted into place, but this may not be required on smaller units if the foundation is rigid and the baseplate can be bolted down securely. 

• The piping should run to a pump as directly as possible, avoiding sharp bends. Entrance to the pump should be provided with long-radius ells or bends to reduce inlet friction to a minimum, and the suction piping should run straight into the pump. 

• Piping must be supported to take the strain from the pump and provide for expansion and contraction to avoid pump misalignment. Expansion joints or loops should be used when hot liquids are being handled. 

• The suction piping should be large enough to minimize the friction losses. Short suction lines are recommended but are not always possible. In order to avoid problems experienced with long intake pipes and high suction lifts, an individual suction line should be provided for each pump. If this is impractical, the suction-header size should be approximately 50 percent larger than the pump connection and should be reduced at the pump flange. The use of tees or right-angle fittings should be avoided, and long radius ells or bends should be used instead. 

• The suction header should be sloped upward from the reservoir to the pump, and high spots in the header, where air might collect, should be avoided. The suction end should be flared, and the suction inlet should be well below the low-water level to eliminate the possibility of air entrainment. The suction should not be located close to the point of makeup or returning water, since eddy currents may interfere with pump operation. When supplying two or more pumps from a long intake header, a tapering header with Y branches to the pump suction should be used. For pumps operating under high suction lift, stuffing boxes should be sealed, using water taken from the discharge header or from a separate source of supply. 

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• The suction lift should be limited to 10 to 15 ft, since only clean cold water can be raised this amount without experiencing operating difficulties. For hot water, it is necessary to bring the water to the pump under a positive head. The velocity should be low, and a suction head of 10 to 20 ft is desirable. When starting up new boiler-feed water or high-temperature-water circulating pumps, a strainer is frequently installed to prevent foreign material from getting into the pumps (and lines) or clogging the suction intake. 

• The strainers can be removed when the system is cleaned. All strainers should be inspected periodically. 

• A pump that has its suction line below the pump centerline requires priming that is, the air must be evacuated from the pump suction before water will enter the pump and fill the piping and casing. Priming may be accomplished by filling the suction piping with water from some other source. When water is ejected in a steady stream, it may be assumed that the pump is full of water, and the pump may be started, after which the discharge valve may be opened slowly. If a vacuum pump is used, it should preferably be a wet vacuum pump, since water may damage a dry vacuum pump. 

• To ensure successful operation of a pump, it should be set on a foundation that is substantial and rigid enough to permit the pump to absorb vibration. Good foundations are usually made of concrete. Before the concrete is poured, the foundation bolts are secured. 

• To prevent the bed plate from springing out of line, the pump must be aligned carefully. Pumps that come already mounted on a bedplate should be leveled before they are placed in operation. Pumps that are to be set on a rough foundation should be set approximately in location and leveled with shims before the bedplate is grouted in position. Commercial grouting is readily available with recommended curing periods. Next, check suction and discharge flanges to determine if they are level. 

• After suction and discharge flanges have been bolted up, the alignment should be checked again. If connecting of piping has caused misalignment, repeat the procedure followed previously. 

• Check pump and motor rotation and insert bolts in flanges and connect up. A short time after the pump has been in operation, the alignment should be checked again. After it is certain that all is satisfactory, the unit can be doweled. The doweling is done with tapered pins usually provided with the pump. Dowel pins are located in the feet of the pump and driver, as well as in the bedplate. 

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OPERATION OF PUMPS:

• Before operation, after all piping has been connected and after the baseplate has been bolted in place, the pump and motor should be aligned with a dial indicator to ensure that operation is free from vibration. Any misalignment will cause vibration that could lead to bearing and mechanical seal failure. 

• When the alignment is being checked, and with the coupling disconnected, the direction of rotation should be checked. This check also can be made with the coupling connected. however, the pump must be filled with liquid to prevent running the packing or seal dry. A mechanical seal can fail in a short period of time if it is run dry. 

• Before placing the pump in operation, make certain that bearings are lubricated. Rotate the motor by hand to make certain everything is free. Prime the pump and fill the pump full of liquid, and with suction valve open and discharge valve closed, start the pump, noting suction and discharge pressures. (All pumps should be fitted with pressure gauges on both the suction and discharge sides.) After running the pump this way for a minute or two with the air vent open, close vent valves and open the discharge valve slowly. 

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• Observe gauges closely, and if anything unusual occurs or pressures seem unusual, stop the pump and check it thoroughly. 

• Start and stop the pump several times and observe performance. If all looks satisfactory, continue to operate for 1h to 1 hour, meanwhile observing bearing temperatures and watching gauges, lubrication, and general actions of the pump and motor for overheating. Then shut the pump down, recheck alignment, tighten all bolts, and give the entire installation a careful check. Place the pump again in operation. 

• observe the packing gland, gland seals, lubrication, and overheating. Never run a pump for an extended period of time with the discharge valve closed unless the vents are open or the pump is equipped with a bypass to permit some water to circulate through the pump at all times. 

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