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PLP Sanitary Lobe Pump Troubleshooting

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    Malfunctions

    What are the main malfunctions and problems with the PLP Sanitary Lobe Pump?

    A malfunction in a pump system may be caused by various reasons and is not necessarily the pump itself. Issues with the pipework or other fluid accessories within the system can be contributing factors. Furthermore, if the operating conditions differ too greatly from the provided specification for which the pump was selected for can also be a major contributing factor.

    Consequently, it is always recommended to check the following first:

    • Has the pump been installed correctly?
    • Are the operating conditions still according to the initial specification?
    • Are the other fluid accessories within the pipework functioning correctly?

    In general, the following malfunctions can be identified:

    1. Pump provides no flow
    2. Pump provides irregular flow
    3. Capacity is too low
    4. Pump overheats
    5. Motor overheats
    6. Excessive Screw / Rotor wear
    7. Excessive wear of shaft sealing
    8. Pump vibrates excessively or makes too much noise
    9. Pump has seized
    10. Pump stops upon start up

    Overleaf is a table of the possible causes and solutions of these malfunctions.

    Malfunction   Cause Solution
    1 2 3 4 5 6 7 8 9 10
    X                 Wrong Direction or Rotation Have a qualified electrician revers the direction of rotation of the electric motor
    X                 Pump is not completely filled with liquid Fill the pump casing entirely with fluid and fit a non-return valve to the suction side
    X X X         X   Insufficient Suction Pressure / NPSHa Increase the suction pressure, lower position of the pump further below the fluid level, enlarge suction pipe ø, shorten / simplify suction pipework, reduce operating speed, reduce product temperature
        X X         X Excessive vapour is present in the suction line
      X X         X   Air is entering the suction line Check Connections
    X X X         X   Gas in the suction line Vent suction pipe / pump casing
      X X         X   Insufficient static head Increase liquid level
          X X     X   X Product viscosity is too high Lower the operating speed / increase product temperature
        X             Product viscosity is too low Increase the operating speed / lower the product temperature
        X X   X   X   X Product temperature is too high Cool the product / pump casing
            X         X Product temperature is too low Heat the product / pump casing
              X X X X Foreign particles are in the product Clean the system / install a suction filter sized according to the max solids passage of the pump
        X X X X   X X X Pressure at delivery side is too high Check piping for obstructions / simplify the discharge pipework
          X X X   X X Pump casing distorted by piping Check alignment / support the piping & install flexible couplings
            X     X   Speed too high Lower the speed
        X             Speed too low Increase the speed
          X X X X X X Insufficient flushing Increase flushing capacity / pressure
          X X X X X X X Worn out bearings / gears Replace the worn out parts
    X                   Safety Valve is open Check if the delivery valve is open / check piping for obstructions / check piping for pressure loss

    Inspection & Maintenance Schedule

    Routine inspection and maintenance can avoid unnecessary and expensive downtime as well as operating costs. It is recommended to regularly check:

    • If the pump functions properly – excessive noise levels may indicate wear problems to bearings and gears, dragging of rotors / lobes on the pump casing or cavitation.
    • Pressure and Flow of the flushing system, if present
    • Temperature of the heating/cooling system, if present
    • Oil level in the gearbox – If the oil level has reduced, check the pump for oil leakages
    • Monitor regularly the pump suction and discharge pressure conditions to ensure they are in line with typical system levels.

    Oil Changes

    • 300 operating hours after the initial commissioning
    • Every 3000 operating hours or at least every 3 months
    • If not being used regularly, every 2000 operating hours, or at least every 3 months
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