Overview
Detailed guide to plunger pump pulsation, acceleration head, suction design, discharge pressure waves, dampeners and corrective action.
Why Does Your Plunger Pump Keep Pulsating? is an important engineering question because the wrong decision can increase downtime, energy use, chemical consumption, maintenance cost and process variation. This guide explains the selection and troubleshooting points in practical detail.
Quick answer
Pulsation is inherent in reciprocating plunger pumps because flow is delivered in strokes. Excessive pulsation is usually caused by long piping, high speed, trapped air, poor suction, inadequate back pressure, incorrect dampener sizing or a badly located injection point.
Table of Contents
- Why Pulsation Occurs
- Normal Versus Excessive Pulsation
- Acceleration Head on the Suction Side
- Air and Gas Entrapment
- Discharge Piping Effects
- Back Pressure
- Pulsation Dampener Selection
- Pipe Supports and Layout
- Operating Speed
- Verification
- Practical Checklist
- Frequently Asked Questions
Why Pulsation Occurs
The plunger alternately fills and discharges the chamber. Flow therefore varies during each stroke instead of remaining perfectly continuous.
For final selection, this point should be checked using the actual minimum, normal and maximum operating conditions. A design based only on one average value can appear satisfactory during a short trial but fail during start-up, low level, maximum pressure, final concentration or maximum viscosity.
Normal Versus Excessive Pulsation
Some pressure fluctuation is normal. It becomes a problem when it causes pipe movement, gauge needle hammering, noise, flow-meter instability or repeated valve and fitting failures.
The technical offer should clearly state any assumption used for this condition. Written assumptions make it easier for the buyer, consultant and manufacturer to review suitability before fabrication and prevent disagreement during commissioning.
Acceleration Head on the Suction Side
Each stroke accelerates and decelerates liquid in the suction pipe. Long lines, small diameter, high speed and high viscosity increase acceleration losses.
Installation and maintenance details are also important. Correctly selected equipment can still perform poorly when piping, supports, instruments, alignment, liquid level or operating procedure differs from the design basis.
Air and Gas Entrapment
Air leaks, gas release or poor priming compress during the discharge stroke and create irregular delivery.
For final selection, this point should be checked using the actual minimum, normal and maximum operating conditions. A design based only on one average value can appear satisfactory during a short trial but fail during start-up, low level, maximum pressure, final concentration or maximum viscosity.
Discharge Piping Effects
Long rigid piping, closed valves, sharp restrictions and unsuitable injection points reflect pressure waves back toward the pump.
The technical offer should clearly state any assumption used for this condition. Written assumptions make it easier for the buyer, consultant and manufacturer to review suitability before fabrication and prevent disagreement during commissioning.
Back Pressure
Very low or unstable discharge pressure can prevent reliable check-valve seating. A properly selected back-pressure valve may improve stability.
Installation and maintenance details are also important. Correctly selected equipment can still perform poorly when piping, supports, instruments, alignment, liquid level or operating procedure differs from the design basis.
Pulsation Dampener Selection
A dampener absorbs part of the flow variation. It must be compatible with the chemical and sized for pump displacement, pressure and allowable residual pulsation.
For final selection, this point should be checked using the actual minimum, normal and maximum operating conditions. A design based only on one average value can appear satisfactory during a short trial but fail during start-up, low level, maximum pressure, final concentration or maximum viscosity.
Pipe Supports and Layout
Even a good dampener cannot correct unsupported piping. Secure the line and avoid arrangements that trap gas.
The technical offer should clearly state any assumption used for this condition. Written assumptions make it easier for the buyer, consultant and manufacturer to review suitability before fabrication and prevent disagreement during commissioning.
Operating Speed
Reducing stroke frequency or using a larger pump at lower speed may reduce pulsation, subject to the pump manufacturer's operating limits.
Installation and maintenance details are also important. Correctly selected equipment can still perform poorly when piping, supports, instruments, alignment, liquid level or operating procedure differs from the design basis.
Verification
Measure actual pressure and flow under normal conditions, calibrate the pump and compare before and after corrective action.
For final selection, this point should be checked using the actual minimum, normal and maximum operating conditions. A design based only on one average value can appear satisfactory during a short trial but fail during start-up, low level, maximum pressure, final concentration or maximum viscosity.
Practical Checklist Before Final Selection
- Define the exact process objective and expected operating cycle.
- Confirm minimum, normal and maximum flow, pressure, level, viscosity, density and temperature as applicable.
- Verify wetted-material compatibility at the actual chemical concentration and temperature.
- Check mechanical limits, torque, service factor, shaft or piping loads and pressure protection.
- Include the required instruments, alarms, interlocks, calibration and maintenance access.
- Ask the supplier to state design assumptions, operating limits and excluded items.
- Review drawings and datasheets before manufacturing.
- Verify actual performance during commissioning under real process conditions.
Why Work With Premix Technologies?
Premix Technologies manufactures industrial agitators, dosing pumps and complete chemical dosing systems for water treatment, chemicals, pharmaceuticals, food processing, oil and gas, mining and other process industries. Equipment can be customized for process conditions, materials of construction, instrumentation and plant control requirements.
Our engineering approach begins with process data and operating requirements. The final selection can include impeller or pump type, materials, motor and gearbox, sealing, accessories, instruments, control philosophy and installation requirements.
Explore our industrial agitators, dosing pumps and chemical dosing systems, or contact Premix Technologies with your application details.
Frequently Asked Questions
Can equipment be selected only from capacity?
No. Capacity is only one input. Process properties, pressure, geometry, materials, operating range, control method and maintenance conditions must also be checked.
Why are minimum and maximum operating conditions important?
Equipment may perform correctly at normal conditions but fail during start-up, low level, peak pressure, high viscosity or shutdown.
Should the supplier state design assumptions?
Yes. Clear assumptions reduce technical risk and allow suitability to be reviewed before fabrication.
Is a larger motor or pump always safer?
No. Oversizing can reduce controllability, increase mechanical loading or waste energy. The complete system must be checked.
Why is commissioning verification necessary?
Actual piping, pressure, viscosity, tank internals and operating practice may differ from preliminary data. Site verification confirms the final result.
Conclusion
Premix Technologies manufactures industrial agitators, dosing pumps and chemical dosing systems for process industries. For technical selection, sizing or quotation support, contact our engineering team.