Does Your Progressive Cavity Pump Not Start?
Progressive cavity pumps often have a hard life, especially in energy-from-waste (EfW) and waste-recycling applications.
These positive displacement screw pumps are great for moving thick paste-like fluids at an even speed and pressure but are often problematic with abrasive and aggressive waste-streams.
Whatever your application, if you have an issue with a faulty progressive cavity pump try this checklist for possible solutions.
Here's our trouble-shooter for a variety of progressive cavity pump (screw-pump) issues:
- Check the power supply matches the pump motor voltage and amps.
- Check that the fuses haven’t blown.
- Has the pump been idle for some time? The rotor and stator may have ‘bonded’, if it doesn’t turn then check for dried debris and lubricate with an appropriate oil or glycerin.
- Has the cable or its connections been damaged? If so, have the damaged section replaced.
- Check that the motor windings haven’t burnt out.
- Have the pumped fluid’s properties changed? Tight tolerances on progressive cavity pumps mean that if the media’s viscosity or temperature do not match the pump’s specification it can lead to thermal expansion. This could burn the rotor and stator where they rub or even jam it, stopping all movement and putting strain on the motor.
- Examine the rotor to make sure it's not blocked or jammed. If it is, then withdraw it from the pump, clean down and if there is no damage evident, reassemble.
- Try reducing the pump’s rotation speed before switching it on, also check the delta start settings if it is an older 3-phase motor, or invertor settings on a newer 3-phase. Generally, the larger the motor, the longer the time delay between start up and full power is needed. If the pump starts okay on a low speed, wait until it has discharged steadily for a time before increasing speed step-by-step to normal operation.
Pump Starts But Then Stops Pumping?
- The rotor might be blocked or the strainer clogged; both can be overcome by cleaning the affected parts. If the strainer has been blocked, check the rotor for cavitation damage (pitting and wear).
- Check the discharge of the pipe to ensure that it isn’t blocked.
- The voltage may be either too low or too high; most pumps in the UK are designed to run on either single-phase 240v or 3-phase 380v – 415v.
- If the pump is running dry or hotter than usual (e.g., above 60 degrees oC), turn off the power to prevent further damage.
- If the main pump motor is forced air-cooled (fan cooled), check this is working properly.
- Gland packing: check this is not worn and has been applied correctly. If it is wound too tight, it can put adverse resistance on the shaft, too loose and it will allow air ingress (and excessive fluid leakage).
- Is the pump still suitable for the application? Feel free to contact us if you are unsure. Call 0800 118 2500.
Is The Pump Giving Too Little Output?
- Check the feed intake is supplied and that the pump’s inlet is fully submerged. Stop the pump and isolate the power while you check for blockages at either end.
- Check the motor is rotating in the correct direction. If not, the wiring needs correcting before it is started up again.
- Has performance reduced over time? Check the wear parts and replace them if worn out. Progressive cavity pumps rely on tight tolerances and abrasive slurries can soon wear down the stator walling and rotor edges.
- Examine the discharge pipework and replace it if leaking or cracked.
- Another reason why the pump may be giving too little output is if the final discharge head is too high; where this is the case, you may need to use a larger pump or an alternative type.
- Check that the rotation speed is correct. Reduced speed for the same power draw could indicate something jamming inside the pump, or the fluid’s viscosity is too high for the pump configuration.
Is The Pump Giving A Vibration Or Knocking Noise?
- Check the transfer bearings are turning smoothly.
- Check for cavitation, this is caused by an insufficient suction head so allow the water level to rise, or lower the pump’s intake deeper into the feeder tank if possible, before turning the pump back on. Net Positive Suction Head (NPSH) needs to meet the pump’s minimum capacity to avoid internal damage. Check if the intake pipe is not causing excess friction. Friction is increased by tight bends, long distances, internal lining damage, an elbow bend too near the pump flange.
- Check the rotor for blockages, and dried matter.
Atlantic Pumps Are Here To Help
If you find your site’s progressive cavity pumps are all too frequently breaking down, it could be that the application is better served by a different technology such as that from the latest generation of LSM, a pump range that uses peristaltic principles.
An increasing number of industrial users of prog pumps, such as municipal EfW (Energy from Waste) facilities and large AD (Anaerobic Digestion) plants, are making significant breakthroughs with alternative pump technologies.
Speak to an Atlantic Pumps technical consultant today, online or by phoning 0800 118 2500 and discover the next level of pump efficiency and full working up-time.
