Diaphragm valve troubleshooting

Diaphragm valve troubleshooting

The two figures below show the parts of a diaphragm valve.

Figure: Components of a diaphragm valve.

Ruptured diaphragm

  • Rubber or fluoroplastcis on the diaphragm have aged. Replace the diaphragm.
  • Too much fluid pressure damages the diaphragm. Operate the valve at the pressure recommended by the diaphragm valve manufacturer.
  • Solids or foreign materials are stuck between the valve seat and the diaphragm. This causes wear or damage to the diaphragm and the valve seat. Open the valve according to the diaphragm valve manufacturer’s instructions and remove embedded foreign materials. If the diaphragm and or the seat is worn out or damaged, replace it.
  • Exceeding the opening height causes damage to the diaphragm. Do not exceed the recommended opening height of the diaphragm.

The diaphragm valve does not operate

  • Disc and diaphragm have fallen off. Avoid opening the valve diaphragm too high. Also, check the diaphragm; if it is damaged, replace it.
  • Valve disc and stem worn out or damaged. Avoid opening the valve past the dead point indicated by the manufacturer. Replace the valve stem and disc as necessary.
  • Jam and wear on the moveable stem nut, stem joint, or valve cover. Clean the valve stem and cover frequently.
  • Solids embedded on the valve stem. Remove the valve stem according to the diaphragm valve manufacturer’s instructions and clean off unwanted solids.

Handwheel is not flexible

  • A bend on the stem. Replace the stem.
  • Damaged stem thread. Repair the stem threads and lubricate them.

Leakage through the valve-pipe joint

  • Loose bolts and nuts. Tighten the bolts and nuts connecting the valve and the pipe to the torque recommended by the diaphragm valve manufacturer.
  • Worn-out seals. Replace the seals on the valve-pipe joint.
  • Fluid flowing at higher pressure. Ensure the fluid flow is at the level recommended by the manufacturer. A diaphragm valve is usually designed for a specific level of fluid pressure.

For automated valves, the valve cannot open and close

  • Low power on the actuator. Increase the power supply on the actuator.
  • Damaged diaphragm. Replace the diaphragm.
  • The glue layer on the valve body is cracked. Replace the valve body.

Fluid leakage through the valve bonnet

  • Loose connection. Tighten the bolts connecting the valve body and the bonnet.
  • Excess fluid pressure. Ensure the fluid flowing through the valve is at the pressure the diaphragm valve manufacturer recommends.
  • Worn-out seals. Replace the bonnet seals.

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