CEMP-E
EI 11C201
1 March 1997
c. Suction pipe connections. Pump suction piping will be selected to provide a velocity of 1.2
to 1.8 meters (4 to 6 feet) per second. Pipe should be one or two sizes larger than the pump
suction nozzle. Vertical pumps installed in a dry well which is adjacent to the wet well, will be
fitted with a 90 degree suction elbow, followed by an eccentric reducer and a gate valve. The
suction line will be extended through the wall into the wet well, and terminated with either a 90 or
45 degree flared elbow, or an elbow with a flared fitting. The most commonly used piping
arrangements are illustrated in figure 7-1, where D is the diameter of the flared inlet, and S is the
submergence depth. Adequate submergence of the suction inlet is critical to prevent air from
being drawn in by vortexing. Minimum required submergence depths are given in table 7-2 as a
function of velocity. The net positive suction head (NPSH) will also be considered when
determining S. See paragraph 7-2c (2).
7-7
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