Why Does a Diaphragm Pump Flow Rate Decrease After Long-Term Operation? Causes and Solutions

 Why Does a Diaphragm Pump Flow Rate Decrease After Long-Term Operation? Causes and Solutions

Diaphragm pumps are widely used in chemical processing, wastewater treatment, pharmaceutical, food processing, coatings, and other industries because of their excellent ability to handle high-viscosity fluids, corrosive liquids, and media containing particles.

However, during actual operation, many users encounter a common problem:

The diaphragm pump works normally at the beginning, but after running for a period of time, the flow rate gradually decreases.

Why does this happen?

A reduced flow rate does not always mean the pump selection is wrong. In most cases, it is related to air supply conditions, wear of internal components, medium characteristics, or improper maintenance.

Shanghai Shangcheng Pump & Valve analyzes the common reasons and solutions for diaphragm pump flow reduction.

1. Insufficient Air Supply Pressure Causes Flow Reduction

For air operated diaphragm pumps, compressed air is the power source.

During long-term operation, flow reduction may occur if:

Air pressure becomes unstable;

The air compressor cannot provide enough capacity;

The air pipeline leaks;

The air filter is blocked.

When the air pressure decreases, the diaphragm movement speed becomes slower.

As a result:

The suction and discharge cycles decrease;

The pumping capacity decreases;

The flow rate drops.

Therefore, the first step is to check:

Air pressure;

Air pipeline condition;

Air filter and regulator system.

2. Diaphragm Wear Reduces Pumping Performance

The diaphragm is one of the most important components in a diaphragm pump.

During operation, the diaphragm repeatedly moves back and forth and may suffer from:

Fatigue damage;

Chemical corrosion;

Particle abrasion.

After long-term use, problems such as:

Diaphragm deformation;

Reduced sealing performance;

Small cracks;

may occur.

When the diaphragm cannot maintain proper sealing, the pump suction capability decreases, causing lower flow output.

Regular inspection of the diaphragm condition is recommended for continuous operation systems.

3. Ball Valve Problems Affect Flow Stability

Diaphragm pumps rely on inlet and outlet ball valves to control liquid flow direction.

If the ball valve has:

Wear;

Blockage;

Poor sealing;

Foreign particles stuck inside;

the pump may experience:

Liquid backflow;

Lower discharge pressure;

Reduced flow rate.

This problem is especially common when transferring:

Slurry;

Wastewater;

Particle-containing liquids.

Checking the ball valve is an important step during troubleshooting.

4. Increased Medium Viscosity Reduces Flow Rate

Although diaphragm pumps are suitable for high-viscosity fluids, changes in medium properties can still affect performance.

For example:

Oil becomes thicker at low temperature;

Resin viscosity increases;

Coating materials become less fluid.

Higher viscosity increases pumping resistance.

Possible solutions include:

Increasing medium temperature;

Reducing suction resistance;

Optimizing pipeline design;

Rechecking pump selection.

5. Inlet Pipeline Problems Cause Insufficient Suction

Diaphragm pumps are positive displacement pumps and require suitable suction conditions.

Problems such as:

Small inlet pipe diameter;

Blocked filter;

Excessive suction height;

Partially closed inlet valve;

can cause insufficient liquid supply.

Typical symptoms include:

Reduced flow;

Unstable operation;

Abnormal noise.

The inlet pipeline should always be kept clean and properly sized.

6. Air Distribution Valve Failure Affects Diaphragm Movement

The air distribution valve controls the alternating air supply to both sides of the diaphragm.

If the air valve becomes:

Worn;

Blocked;

Stuck;

the diaphragm movement may become slow or abnormal.

Common symptoms:

Slow pump operation;

Unstable flow;

Failure to switch direction properly.

In this situation, the air valve assembly should be inspected and repaired.

7. How to Prevent Diaphragm Pump Flow Reduction?

To maintain stable performance, proper maintenance is essential.

1. Maintain Stable Air Supply

Regularly check:

Air pressure;

Filters;

Air treatment equipment.

Stable compressed air ensures consistent diaphragm movement.

2. Inspect Wear Parts Regularly

Important components include:

Diaphragm;

Ball valves;

Valve seats;

Air distribution valve.

Replacing worn parts in time can prevent unexpected downtime.

3. Select Proper Materials According to Medium

Different applications require different materials.

Examples:

PP or PVDF for corrosive chemicals;

Wear-resistant materials for abrasive slurry;

Sanitary materials for food and pharmaceutical applications.

Incorrect material selection may shorten service life.

Conclusion

When a diaphragm pump flow rate decreases after long-term operation, the main causes may include:

Insufficient air supply;

Diaphragm wear;

Ball valve problems;

Increased medium viscosity;

Blocked inlet pipeline;

Air valve failure.

Instead of replacing the pump immediately, users should check the entire operating system step by step.

Shanghai Shangcheng Pump & Valve provides diaphragm pump selection and application solutions for chemical, environmental protection, food, pharmaceutical, and industrial fluid transfer industries, helping customers achieve stable and efficient operation.

Keywords:

Air Operated Diaphragm Pump, Diaphragm Pump Flow Reduction, AODD Pump Troubleshooting, Industrial Diaphragm Pump Manufacturer.