Bell & Gossett Double Suction Pump Troubleshooting Guide

If you’ve been called to take a look at a Bell & Gossett double suction pump, there are several troubleshooting causes and solutions that can solve your client’s problems. Take a look at our guide below to determine what’s wrong and how to fix it.

This troubleshooting guide is applicable for e-HSC, VSX, VSH, VSC and VSCS series models.

No Liquid Being Delivered to System

• Lack of prime—Completely fill the pump and suction pipe with liquid.
• Loss of prime—Inspect the suction pipe joints and fittings for any signs of leaks and/or vent the casing to remove any accumulated air.
• Suction lift is too high
  • Solution 1—Check for an obstruction at the inlet. If one isn’t present, check the suction pipe for friction loss. 
  • Solution 2—Static lift may be too high. Use a mercury column or vacuum gauge to measure while the pump operates. If the static lift is too high, the liquid to be pumped needs to be raised, or the pump needs to be lowered.
• Discharge head is too high—Make sure the valves are wide open.
• Speed is too low
  • Solution 1—Make sure the motor is properly wired.
  • Solution 2—Frequency is too low, or the motor may have an open phase. Ensure that the driver and speed match the pump nameplate speed.
• Suction diffuser or strainer screen is clogged—Dismantle the components and clean.
• Impeller is clogged—Dismantle the pump and clean the impeller.

Not Enough Liquid Being Delivered to System

• Suction lift is too high
  • Solution 1—Check for an obstruction at the inlet. If one isn’t present, check the suction pipe for friction loss. 
  • Solution 2—Static lift may be too high. Use a mercury column or vacuum gauge to measure while the pump operates. If the static lift is too high, the liquid to be pumped needs to be raised, or the pump needs to be lowered.
• Impeller is clogged—Dismantle the pump and clean the impeller.
• Speed is too low
  • Solution 1—Make sure the motor is properly wired.
  • Solution 2—Frequency is too low, or the motor may have an open phase. Ensure that the driver and speed match the pump nameplate speed.
• Air is leaking into suction pipe—Test the flanges for leaks by plugging the inlet and putting the line under pressure. If the gauge shows a drop in pressure, there is a leak.
• Discharge head is too high—Make sure the valves are wide open, or replace piping with a larger size.
• Cavitation, or insufficient NPSH A
  • Solution 1—Increase the positive suction head on pump.
  • Solution 2—Lower the temperature of the liquid in the suction pipe.
• Defective impeller—Check the impeller, shaft and bearings. If needed, replace these components.
• Motor rotation is in the wrong direction—Check the rotation of the motor and compare it to the directional arrow that’s on the pump casing. Adjust the rotation direction.
• Impeller rotation is in the wrong direction—Adjust the impeller rotation direction on the shaft.
• Impeller diameter is too small—Check with the OEM to see if a larger impeller can be used in the unit you’re working on. If not, you can cut the pipe losses or increase the speed (or both). Do not overload the driver.

Not Enough Pressure

• Mechanical defects
  • Solution 1—Check the impeller, shaft and bearings. If needed, replace these components.
  • Solution 2—Check the rotation of the motor and compare it to the directional arrow that’s on the pump casing. Adjust the rotation direction.
• Impeller diameter is too small—Check with the OEM to see if a larger impeller can be used in the unit you’re working on. If not, you can cut the pipe losses or increase the speed (or both). Do not overload the driver.
• Liquid passages are blocked—Take apart the pump and check the passages of the impeller and casing to remove obstruction.
• Air or gases are present in liquid
  • Solution 1—Install an air removal device.
  • Solution 2—Fix leaks in system piping.
• Speed is too low
  • Solution 1—Make sure the motor is properly wired.
  • Solution 2—Frequency is too low, or the motor may have an open phase. Ensure that the driver and speed match the pump nameplate speed.
• Excessive system flow—Balance the system.

Pump Works for a Short Time, Then Stops

• Incomplete priming—Remove air from the pump, valves and piping. Correct any high points in the suction line if needed.
• Suction lift is too high
  • Solution 1—Check for an obstruction at the inlet. If one isn’t present, check the suction pipe for friction loss. 
  • Solution 2—Static lift may be too high. Use a mercury column or vacuum gauge to measure while the pump operates. If the static lift is too high, the liquid to be pumped needs to be raised, or the pump needs to be lowered.
• Air is leaking into suction pipe—Test the flanges for leaks by plugging the inlet and putting the line under pressure. If the gauge shows a drop in pressure, there is a leak.
• Air or gases are present in liquid
  • Solution 1—Install an air removal device.
  • Solution 2—Fix leaks in system piping.

Pump is Using Too Much Power

• Head is lower than recommended rating, and is pumping too much liquid—Follow OEM guidelines to machine the impeller’s outer diameter to the correct size.
• Cavitation, or insufficient NPSH A
  • Solution 1—Increase the positive suction head on pump.
  • Solution 2—Lower the temperature of the liquid in the suction pipe.
• Mechanical defects
  • Solution 1—Check the impeller, shaft and bearings. If needed, replace these components.
  • Solution 2—Check the rotation of the motor and compare it to the directional arrow that’s on the pump casing. Adjust the rotation direction.
• Liquid is heavier than allowed for (viscosity or specific gravity)—Check with the OEM to get the recommended size of a larger driver to use, then test the liquid for viscosity and specific gravity.
• Motor rotation is in the wrong direction—Check the rotation of the motor and compare it to the directional arrow that’s on the pump casing. Adjust the rotation direction.
• Casing has been distorted by excessive strains from discharge piping or suction—Check the alignment of the casing, along with the pump for any friction between the impeller and casing. Replace parts as needed.
• Damaged shaft—Check the deflection of the rotor by turning the bearing journals. The total indicator run-out shouldn’t exceed 0.002” on the shaft and 0.004” on the impeller eye’s outer diameter. Replace as needed.
• Damage or fault of bearings and/or impeller—Check the bearings and impeller for any damage and replace as needed.
• Pump and driver are misaligned—Realign the pump and driver.
• Speed is too high—Ensure that the driver speed matches the pump nameplate speed.