Progressive Cavity Fault Diagnosis

Pump will not start

Rotor & Stator Adhesion.

Adhesion between Stator and Rotor due to prolonged period of inactivity. Lubricate rotor and stator with glycerin, or inert oil.

 Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration/system set up to reduce pressure on the outlet

Blockage

Open inspection port to remove solids, if not possible to remove all,   disassemble the pump and clean

Fluid Temperature

Clearances between rotor and stator are minute. If the fluid is outside the pump design range, the stator will suffer thermal expansion and burn against the   rotor

Solid Size

The solid size is too large for the pump. Reduce pump speed or install a filter   on the suction

Sedimentation / Crystallization

During inactivity, sedimentation or crystallization is occurring. Flush   pump, disassemble and clean

Frozen Fluid

Temperature is too low with fluid freezing within the pump. Ensure the pump is protected from elements, drain when not in use or install trace heating.

Stator Incompatible with fluid

Check chemical compatibility

Incorrect pump speed

Check pump speed. Verify power absorbed, frequency, voltage and rpm.

Viscosity too high

Check against original pump specification

Gland Packing

Gland packing is worn too tight and requires loosening

Inverter Settings / Wiring

Check to start torque of the motor is correct as on initial startup power absorbed can be high meaning, if the torque is not set correctly on the inverter, it will not start the pump.

Due to the friction between the stator and rotor it may be necessary to increase start-up torque.

If an inverter is used an incorrect configuration of the parameters could cause problems.

On motors with 7.5 kW or larger inverters, it is recommended to set an acceleration ramp of at least 4 s, whereas for motors with

smaller inverters, at least 2 s. 

This will reduce the stress at a start-up. Moreover, the starting rpm significantly affects the startup

The torque is required to start the pump.

 It is therefore recommended to reduce the pump’s starting rpm if any problems arise.

If forced air cooling is fitted to the motor and is not wired (requires wiring separately to the motor) then the pump may start and trip as it is not receiving sufficient cooling from the external cooling fan.

Pump not creating suction

Blockage

Open inspection port to remove solids, if not possible to remove all, disassemble the pump and clean

Fluid Temperature

Clearances between rotor and stator are minute. If the fluid is outside the pump design range, the stator will suffer thermal expansion and burn against the rotor

Solid Size

The solid size is too large for the pump. Reduce pump speed or install a filter   on the suction

Sedimentation / Crystallization

During inactivity sedimentation or crystallization is occurring.   Flush pump, disassemble and clean

Air Ingress

Air Ingress through Seal or inlet pipework. Refit/replace the seal.   Tighten bolts on joints.

Frozen Fluid

Temperature is too low with fluid freezing within the pump. Ensure the pump is protected from elements, drain when not in use or install trace heating.

Suction Head too high

Check inlet pressure, check inlet filter, check suction line is fully open.

Low Pump Speed

Pump speed too low for low viscosity fluids, and amounts to transfer too large.

High Pump Speed

Pump speed too high with viscous liquid. Risk of cavitation

Direction of rotation

Check the direction of rotation is inline with arrow on nameplate. Check   drive coupling

NPSH

Check NPSHA meets NPSHR. Increase fluid level, lower viscosity,   increase pipe suction diameter, reduce pump speed

Dry Running

Partially or fully running dry. Install dry protection probe

Stator Worn

Replace

Rotor Worn

Replace

High Viscosity

Check against pump specification

Gland Packing

Gland packing worn too tight and requires loosening

Flow Rate Incorrect

Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration / system   set up to reduce pressure on the outlet

Blockage

Open inspection port to remove solids, if not possible to remove all,   disassemble pump and clean

Air Ingress

Air Ingress through Seal or inlet pipework. Refit/replace the seal.   Tighten bolts on joints.

Suction Head too high

Check inlet pressure, check inlet filter, check suction line is fully open.

Air Pockets

Air pockets within the fluid. Check system. Slow pump, increase the level of fluid in tank, or deepen suction pipework.

Low Pump Speed

Pump speed too low for low viscosity fluids, and amounts to transfer too large.

Dry Running

Partially or fully running dry. Install dry protection probe

Stator Worn

Replace

Rotor Worn

Replace

Transmission Broken or Faulty

Check and repair where needed

Incorrect pump speed

Check pump speed. Verify power absorbed, frequency, voltage and rpm.

High Viscosity

Check against pump specification

Gland Packing

Gland packing is worn too tight and requires loosening

Mechanical Seal

Check seal faces for wear. Check seal compression. Replace worn items.  

Seal System

Pump Seal System is unsuitable and requires changing.

Uneven Flow

  Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration / system   set up to reduce pressure on outlet

Air Ingress

Air Ingress through Seal or inlet pipework. Refit/replace seal.   Tighten bolts on joints.

Suction Head too high

Check inlet pressure, check inlet filter, check suction line is fully open.

Air Pockets

Air pockets within the fluid. Check system. Slow pump, increase the level of fluid in tank, or deepen suction pipework.

High Pump Speed

Pump speed too high with viscous liquid. Risk of cavitation

Dry Running

Partially or fully running dry. Install dry protection probe

Stator Worn

Replace

Rotor Worn

Replace

High Viscosity

Check against pump specification

Excessive Pump Vibration

Solid Size

The solid size is too large for the pump. Reduce pump speed or install a filter on the suction

Air Ingress

Air Ingress through Seal or inlet pipework. Refit/replace the seal.   Tighten bolts on joints.

Suction Head too high

Check inlet pressure, check inlet filter, check suction line is fully open.

High Pump Speed

Pump speed too high with viscous liquid. Risk of cavitation

NPSH

Check NPSHA meets NPSHR. Increase fluid level, lower viscosity,   increase pipe suction diameter, reduce pump speed

Drive Shaft

Verify driveshaft movement. The transmission bush may be fitted   incorrectly

Stator Worn

Replace

Rotor Worn

Replace

Transmission Broken or Faulty

Check and repair where needed

Bearings Worn

Replace Bearings

Incorrect pump speed

Check pump speed. Verify power absorbed, frequency, voltage and rpm.

Pump seized or stopped

pumping

Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration/system set up to reduce pressure on the outlet

Solid Size

The solid size is too large for the pump. Reduce pump speed or install filter   on the suction

Fluid Temperature

Clearances between rotor and stator are minute. If the fluid is outside the pump design range, the stator will suffer thermal expansion and burn against the   rotor

Blockage

Open inspection port to remove solids, if not possible to remove all,   disassemble the pump and clean

Sedimentation / Crystallization

During inactivity sendimentation or crystallization is occurring.   Flush pump, disassemble and clean

Drive Shaft

Verify driveshaft movement. The transmission bush may be fitted   incorrectly

Dry Running

Partially or fully running dry. Install dry protection probe

Stator Worn

Replace

Rotor Worn

Replace

Transmission Broken or Faulty

Check and repair where needed

Bearings Worn

Replace Bearings

High Viscosity

Check against pump specification

Stator Damage

  Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration/system set up to reduce pressure on the outlet

Blockage

Open inspection port to remove solids, if not possible to remove all,   disassemble the pump and clean

Fluid Temperature

Clearances between rotor and stator are minute. If the fluid is outside the pump design range, the stator will suffer thermal expansion and burn against the   rotor

Solid Size

Solid size is too large for the pump. Reduce pump speed or install the filter on suction

Sedimentation / Crystallization

During inactivity sendimentation or crystallization is occurring.   Flush pump, disassemble and clean

Fluid Temperature

Clearances between rotor and stator are minute. If fluid is outside   pump design range, the stator will suffer thermal expansion and burn against the   rotor

Suction Head too high

Check inlet pressure, check inlet filter, check suction line is fully open.

High Pump Speed

Pump speed too high with viscous liquid. Risk of cavitation

NPSH

Check NPSHA meets NPSHR. Increase fluid level, lower viscosity,   increase pipe suction diameter, reduce pump speed

Dry Running

Partially or fully running dry. Install dry protection probe

Stator Worn

Replace

Stator Incompatible with fluid

Check chemical compatibility

Incorrect pump speed

Check pump speed. Verify power absorbed, frequency, voltage and rpm.

Rotor Damage

  Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration / system   set up to reduce pressure on outlet

Blockage

Open inspection port to remove solids, if not possible to remove all,   disassemble pump and clean

Solid Size

Solid size is too large for pump. Reduce pump speed or install filter   on suction

Sedimentation / Crystallization

During inactivity sendimentation or crystallization is occurring.   Flush pump, disassemble and clean

Fluid Temperature

Clearances between rotor and stator are minute. If the fluid is outside the pump design range, the stator will suffer thermal expansion and burn against the   rotor

High Pump Speed

Pump speed too high with viscous liquid. Risk of cavitation

NPSH

Check NPSHA meets NPSHR. Increase fluid level, lower viscosity,   increase pipe suction diameter, reduce pump speed

Rotor Worn

Replace

Rotor Incompatible with fluid

Check chemical compatibility

Incorrect pump speed

Check pump speed. Verify power absorbed, frequency, voltage and rpm.

Seal Leakage

Blockage

Open inspection port to remove solids, if not possible to remove all,   disassemble pump and clean

Solid Size

Solid size is too large for pump. Reduce pump speed or install filter   on suction

Fluid Temperature

Clearances between rotor and stator are minute. If fluid is outside   pump design range, stator will suffer thermal expansion and burn against the   rotor

High Pump Speed

Pump speed too high with viscous liquid. Risk of cavitation

Direction of rotation

Check the direction of rotation is in line with arrow on nameplate. Check   drive coupling

High Viscosity

Check against pump specification

Gland Packing

Gland packing is worn too tight and requires loosening

Mechanical Seal

Check seal faces for wear. Check seal compression. Replace worn items.  

Seal System

The pump Seal System is unsuitable and requires changing.

Drive Motor Generating Heat

Adhesion between Stator and Rotor

Adhesion between Stator and Rotor due to prolonged period of inactivity. Lubricate rotor and stator with glycerine, or inert oil.

 Excess Pressure on Outlet

Increase pump size or motor size. Change piping configuration / system set up to reduce pressure on the outlet.

Fluid Temperature

Clearances between rotor and stator are minute. If fluid is outside   pump design range, stator will suffer thermal expansion and burn against the   rotor

Incorrect pump speed

Check pump speed. Verify power absorbed, frequency, voltage and rpm.

Gland Packing

Gland packing is worn too tight and requires loosening

Insufficient Pressure

Stator Worn

Replace

Rotor Worn

Replace