Troubleshooting Guidelines- Possible Causes & Remedies for Fristam’s Positive Displacement Pumps

A positive displacement pump is an essential piece of equipment in most industries, such as food processing, bio-pharmaceuticals, dairy, and personal & home care. The pumps effectively deal with thick, viscous liquids and provide smooth production line operation. But, as with all machinery, they may also experience occasional problems. Knowing about the potential causes and remedies at hand can ensure that they operate at optimal levels.

Fristam, a renowned name in positive displacement pumps manufacturing, provides reliable solutions as the industry experts for their FK, FKL and FL series. If you experience problems with your pump, this guide will help you identify and fix them.

1. Pump either does not pump or pumps irregularly

Probable Causes:

• Pump interior not fully filled with fluid; pump interior not vented; discharge valve shut.
• Suction line blocked or clogged.
• Pump with geodesic suction head: fluid drops at dead stand and casing runs dry.
• Suction line leaking; leaky seal on pump cover and sucking in air.
• Air trap in suction line.
• Pump blocked; foreign matter in pump.

Remedies:

• Make sure the pump is well primed and the discharge valve is open for operation.
• Clean and check suction line is not blocked.
• Fit a foot valve to the suction line to avoid dry running.
• Repair leaks in suction lines and change defective cover seals.
• Lay suction lines level with gradual slope to remove air pockets.
• Disassemble and clean the pump; scrap out any foreign bodies.

2. Flow rate too high

Possible Causes:

• Pump oversized.
• No regulating valve behind discharge port.

Remedies:

• Make sure the positive displacement pump type is suitable for the application's flow rate requirements.
• Fit a regulating valve or throttle control to adjust the output.

3. Flow rate too low; discharge head too low

Possible Causes:

• Pump too small; motor speed too low due to improper voltage.
• Suction line leaky and sucking in air.
• Viscosity of pumping medium too high.
• Rotor wear; clearance too large.
• Back pressure too high; relief valve regulating incorrectly.
• Wrong direction of rotation.

Remedies:

• Check pump size and motor speed are appropriate for the desired output.
• Seal leaks in the suction line to ensure correct vacuum conditions.
• Lower the viscosity by heating the medium or refer to Fristam for other options.
• Check and replace worn out rotors to ensure correct clearance.
• Set relief valve settings to ensure maximum back pressure regulation.
• Check and correct pump direction of rotation if needed.

4. Metal noise

Possible Causes:

• Foreign material in pump interior.
• Rotors mechanically seized; rotor nuts loose.
• Too much bearing and gearwheel wear due to overloading or poor lubrication.
• Speed too high.
• Pump and shaft seal running dry without water.
• No high-temperature rotors fitted for high-temperature services.
• Excessive throttling of discharge pipe.

Remedies:

• Dismantle and check pump for foreign particles.
• Check the alignment of rotors and secure rotor nuts tightly.
• Replace worn gearwheels and bearings and properly lubricate them.
• Regulate speed by using a frequency converter to avoid excessive operation.
• Ensure unbroken fluid supply to prevent dry running.
• Install high-temperature rotors when dealing with hot liquids.
• Eliminate excessive throttling to enhance flow conditions.

5. Flow noise

Potential Causes:

• Running in overload or part-load condition.
• Suction line flow losses too high.
• Cavitation

Remedies:

• Vary the operating point to match with pump design.
• Increase diameter of suction line to minimize flow resistance.
• Verify NPSH (Net Positive Suction Head) requirements to avoid cavitation.

6. Vibrations

Potential Causes:

Weight and hydraulic forces of pipes stressing the pump.

Remedies:

• Provide adequate pipe support to avoid excessive load on the pump.
• Install vibration dampers and avoid water hammer effects.

7. Excessive heating of pump shaft bearings and drive gear

Possible Causes:

• Bearing damage.
• Lubricating oil insufficient.

Remedies:

• Check and replace damaged bearings, if necessary.
• Replace lubricating oil according to Fristam's maintenance schedule.

8. Motor power consumption too high

Possible Causes:

• Discharge line resistance too high; pump throttled too severely; flow rate too low.
• Viscosity and/or density of pumping medium too high.
• Rotors mounted with incorrect clearance against specifications.
• Severe pump shaft bearing or gear motor damage.

Remedies:

• Increase discharge line size to lower resistance and modify throttle valve.
• Optimize speed of motor using a frequency converter or control gear.
• Mount rotors with proper clearance according to manufacturer recommendations.
• Check bearings and gear motor for damage and replace if needed.

9. Leakage at Shaft Seal

Possible Causes:

• Mechanical damage or wear in the shaft seal.
• Shaft seal running dry; suction head higher than permissible; pumping medium too hot.
• Pressure of sealing or flushing water too high or low.
• Shaft seal materials chemically not suitable for pumping medium.
• Sealing water too contaminated or too hot.

Remedies:

• Repair or replace shaft seals that are worn out or damaged.
• Lower suction head and employ double shaft seal for high-temperature services.
• Adjust sealing water pressure by using a throttle valve.
• Select shaft seal materials which are compatible with the fluids being handled.
• Use good quality sealing water with a maximum temperature of 70°C.

How to Maintain Your Fristam Positive Displacement Pump

Regular pump maintenance is necessary to maximize the life of your equipment. Below are some general guidelines:

• Adhere to the manufacturer's maintenance schedule.
• Regularly clean the pump and its parts.
• Replace with Fristam-approved spare parts.
• Check performance data with positive displacement instrumentation equipment.

By doing so, you can avoid downtime and enhance the effectiveness of your positive displacement pump application.

Conclusion

Understanding the workings of a positive displacement pump makes it easier to troubleshoot and maintain it efficiently. Fristam's FK and FL series pumps are manufactured for reliability, but timely maintenance and prompt response to possible faults guarantee their optimum performance.

If you require more information or high-quality positive displacement pump manufacturing services, visit Fristam's official website for expert assistance.