Service Manual 73
Page 30 of 32
2. Remove the adjusting screw cap and gasket to expose the adjusting screw.
3. Loosen the lock nut.
4. Start the pump running.
5. Slowly restrict the discharge line, while observing the pressure gage. Stop immediately if the
pressure rises above a safe level.
6. With the discharge line fully closed, the gauge will read the full by-pass pressure setting for
the current speed and viscosity. Do not leave the discharge line closed for a long time, since
the fluid temperature will rise rapidly.
7. Adjust the valve adjusting screw to obtain the desired full by-pass setting. Tighten the screw
to increase the setting, and loosen it to reduce the setting.
8. Once set, reopen the discharge line.
9. This setting should be 15 to 25 percent above normal operating pressure presented by the
system to ensure the valve does not operate during normal use.
!
CAUTION
If there is some other flow control device present in the system that will vary the system pressure,
the relief valve setting should be set above this pressure to ensure the valve does not function
during normal use.
10. Tighten the lock nut.
11. Install the adjusting screw cap and gasket.
Troubleshooting
1. Problem: No fluid is delivered.
a. Power is not on.
b. Net positive suction head available (NPSHa) is lower than required for the vapor pressure
of the liquid pumped. You should calculate NPSHa and redesign piping, if necessary.
c. Leaks in suction line or port passages. These can be detected by submerging pressure
line from discharge side of pump into a pail of liquid where the air will be seen in the form
of bubbles.
d. Direction of shaft rotation is incorrect.
e. Relief valve setting is too low. Liquid is discharging through the by-pass port.
