Tuthill 6000, Installation And Service Instructions Manual

Page: 34 / 36

Service Manual # 67
Page 34 of 36
Section 21: 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. Magnetic coupling has decoupled. Check for excessive pressure/speed problems.
f. Relief valve setting is too low. Liquid is discharging through the by-pass port.
2. Problem: Capacity is too low.
a. Air leaks in suction line.
b. Suction losses are too high. The suction lift is too great or the suction line is too small or
too long. This can be detected by installing a vacuum gauge directly at the pump suction.
The maximum vacuum at the pump suction should never exceed 15” of mercury.
Vaporization caused by higher vacuums will generally result in capacity drop off. Redesign
suction conditions .
c. Pump speed is too slow.
d. Strainer too small or obstructed.
e. Suction pipe or port not immersed in liquid deep enough
f. Piping improperly installed permitting air pocket to form in the pump.
g. Increased clearances or wear in the pump will sometimes cause the pump to deliver an
insufficient supply of liquid. This may be corrected by reducing the thickness of the cover
gaskets. A folded gasket or a slight amount of dirt can exaggerate the problem and cause
leakage. Refer to Assembly Procedure section for minimum end clearances.
3. Problem: Pump works spasmodically.
a. Leaky suction lines.
b. Suction conditions vary.
c. Air or vapor in liquid.
4. Problem: Excessive power draw.
a. Pressure too high.
b. Liquid more viscous than originally expected.