Nordson 25B - Pump Suction Problems

Troubleshooting
6-5
E 1999 Nordson Corporation
All rights reserved
104 330H
Issued 8/99
Manual 1-8
Use the following guidelines to isolate and correct 25B pump suction
problems.
Cavitation
A large percentage of pump problems are the result of siphoning
problems or cavitation. Pressure variations can be caused by restricting
the suction or siphon side of the pump. When the pump does not fully
prime on the up stroke, the pump will race or dive on the early portion of
the down stroke. When the plunger contacts the fluid, a hydraulic shock
and pressure spike is created. This hydraulic hammer also reduces
packing, plunger, and siphon check valve life.
As a pump is used in higher viscosity and/or flow applications, the
chances of cavitation increase. The simplest way to avoid cavitation
problems is to provide a positive pressure at the pump inlet. This can be
accomplished by one of the following methods.
S Elevate the material supply, above the pump if possible.
S Immerse the pump inlet (use bucket or drum mount kits).
S Use a positive pressure supply system to feed the pump. Normal
supply pressures are 0.35–1.03 bar (5–15 psi).
S Use ram (elevator) mounted pumps, inductor plates, or
follower plates.
Pump Suction Problems