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12.4.1.1 Check water inlet valve

Check water inlet valve for proper operation. Water supply pressures differing from

those originally specified will result in inadequate or erratic supply. Remedy by using a

properly sized valve or adjusted water supply pressure.

12.4.1 2 Sudden slugs of water

Sudden slugs of water will cause severe variations in steam pressure. These can be the

result of large volume returns from a condensate pump, or an oversized water inlet

valve. Inlet water flows should be as smooth as possible to avoid sudden steam

pressure drops, which will cause flashing and cavitation in the boiler feed pumps.

12.4.1.3 Water flows

Make certain that total water flows (returns and make-up) do not exceed rated

deaerator capacity.

12.5 Pumps

Unusual noise may be caused by several factors, as follows:

12.5.1 Cavitation

At any given temperature, all liquids have a definite pressure at which they will boil. It

follows, therefore, that a liquid will boil at any temperature, if the pressure is reduced

sufficiently. All pumps have a specific net positive suction heat (NPSH) requirement. If

this positive head is not available, pump cavitation will develop, resulting in severe

damage.

The required NPSH has been provided in this system, including additional height to

overcome suction line friction losses.

Suction piping is intentionally oversized to further reduce these losses.

Any unusual restriction, such as a clogged strainer, in the suction piping will cause

cavitation. The existence of such an obstruction can best be determined by a thorough

visual check or by installing a compound gauge (reading in vacuum and pressure) in the

pump suction line close to the pump. A thoroughly clean unrestricted line will produce

a pressure reading on the gauge, while the pump is running, equal to the operating

pressure of the deaerator plus the static head available. This head is measured in feet

from the water level to the pump suction centerline and converted to PSIG by dividing

by 2.31. A slight variance may be observed due to friction losses in suction piping. Any

restriction must be corrected immediately or severe pump damage will result.