10.1 INTAKES, SUCTION PIPING, AND STRAINERS

WILSON L. DORNAUS

CHARLES C. HEALD

The most critical part of a system involving pumps is the suction approach, or inlet, whether in the form of piping or open pit. A centrifugal pump that lacks proper pressure or flow patterns at its inlet will not respond properly or perform to its maximum capability. Uniformity of flow and flow control to the point of pumped fluid contact with the impeller inlet vanes are the most important. Part of this may be controlled by proper pump design, but the pit designer and suction piping designer have definite responsibilities to achieve satisfactory pump operation. In open suction pit (wet-well) designs, the fluid flow must be as uniform as possible right up to contact with the pump suction bell or suction pipe, preferably without a change in direction or velocity.

Examples of dry-pit and wet-pit centrifugal pumps connected to open suction pits are shown in Figure 1.

FIGURE 1: Pump auction connections: (a-d) vertical dry-pit pimps. (a) Suction bell diameter and distance from bottom, side, and back walls designed to provied radial inflow, equal velocity distribution, minimum entrance loss. Proper spacing of bell and vertical baffle required to prevent underwater eddies and rotation at inlet. (b) To minimize excavation under pump, decreasing-type suction elbow can be formed in the foundation. (c) Width of suction inlet under pump minixized use of turning vanes. (d) Smaller pumops provided with integral suction elbows and can be connected to wet well...