Maintenance of membrane pumps: membrane replacement, valve cleaning and pulsation damper maintenance

1. Scope and purpose

This manual covers the maintenance of Double Diaphragm Air Operated Diaphragm Pumps (AODD). Instructions include how to replace the diaphragms, clean the check valves, and adjust the pulsation damper. The procedures are designed to ensure reliable operation and prolong the service life of equipment in industrial production conditions.

2. Safety measures

WARNING: Before starting any work, the pump and piping system must be completely depressurized. Perform a full Lockout/Tagout (LOTO) procedure for compressed air and fluid sources. The use of appropriate personal protective equipment (PPE), including safety glasses, chemical-resistant gloves and safety shoes, is mandatory. If the pump has been used to work with hazardous chemicals, thoroughly flush the pump with neutral media before disassembly.

3. Tools and materials

4. Pre-service checklist

5. Step-by-step procedure

1. Isolating and draining the pump: Shut off the supply of air and working fluid. Perform the LOTO procedure. Gradually open the drain holes to release the residual pressure and drain the working fluid into a suitable container. Do not leave the pump under pressure.
2. Liquid side disassembly: Disconnect the inlet and outlet pipes. Remove the covers (manifolds) of the liquid chamber by unscrewing the fastening bolts. Inspect the condition of the sealing rings.
3. Cleaning or replacing check valves: Remove the valve balls and seats. Inspect for foreign objects, corrosion, or wear. Clean the saddles. If the saddles have visible damage (scratches, chips), replace them. Do not use sharp tools to clean saddles.
4. Membrane replacement: Unscrew the outer membrane plates on both sides. Remove the old membrane. Clean the stem. Install the new diaphragm following the manufacturer's instructions for correct orientation. Critically important: Tighten the diaphragm fastening bolts with a clearly defined tightening torque (for example, 15-20 Nm, depending on the model). Incorrect tightening torque will lead to premature failure of the membrane.
5. Ripple damper service: Remove the damper cover. Inspect the internal diaphragm/bladder for integrity. If necessary, replace it. Check the damper charging pressure (usually 60-80% of the operating fluid pressure).
6. Reassembly: Reverse reassembly using new seals. Use the recommended O-ring lubricant.

6. Inspection after maintenance

7. Troubleshooting

8. Maintenance schedule

9. List of spare parts

To order original spare parts, visit our online catalog: https://www.unitecd.com/e-catalog/

10. Links

• ISO 8573-1: Compressed air quality.
• EN 809: Pumps and pumping units for liquids.
• Relevant technical documentation of the pump manufacturer.