Why an Air-Operated Diaphragm Pump's Diaphragm Stops Moving, and How to Fix It
2024-10-12
Air-operated diaphragm pumps offer advantages such as safety, built-in self-priming capability, and a wide range of available materials. In recent years, more and more customers have begun adopting air-operated pumps in place of other pumps. Every pump, whatever its type, needs maintenance and repair. The diaphragm pump is a positive-displacement pump and differs greatly from the centrifugal pumps most people are familiar with.
So when operating and servicing one, please follow procedures based on how the pump actually works. Starting today, our team will share knowledge about the use and repair of various pumps through articles and videos.
When an air-operated diaphragm pump fails to work, based on years of customer feedback collected by pump manufacturers, the problem falls into two categories: in the first, the diaphragm does not move, meaning there is no sound of normal positive-displacement action; in the second, the diaphragm moves back and forth, but no liquid is discharged from the outlet. The second case is classified as a "no power" problem in positive-displacement pumps. Today we will first show you how to quickly diagnose the first case.
If you encounter a situation where the diaphragm does not move after air is supplied to the pump, first inspect the pump's muffler. The muffler will show one of two symptoms: leaking liquid or leaking air:
When the air supply is connected and the muffler leaks liquid, it indicates that the seal between the motor (air) end and the liquid end of the air-operated diaphragm pump has failed, because the diaphragm has ruptured or the diaphragm clamping plate bolts have loosened. In this case, simply remove the diaphragm, inspect it, and replace it.
When the air supply is connected and the muffler leaks air, it indicates a problem with the internal seal of the pump's motor (air) end. In this case, simply open the motor cover and inspect the internal O-ring.
We should remind you, however, that the O-ring may be obviously worn or cracked; alternatively, it may simply be fouled with too much dirt, in which case you only need to remove and wipe it clean.
What are the possible causes when an air-operated diaphragm pump won't start?
1. The air-operated diaphragm pump runs, but the flow is low or no liquid is discharged at all:
1. Check the pump for cavitation, and reduce the pump speed to allow liquid to enter the liquid chamber.
2. Check whether the valve balls are stuck. If the process fluid is incompatible with the pump's elastomers, the elastomers will swell. Replace them with elastomers of a suitable material.
3. Check that the fittings at the pump inlet are fully tightened and leak-free, especially the clamp near the inlet-side valve ball, which must be tight.
2. Product flows out of the air exhaust port:
Check whether the diaphragm has ruptured, and check that the diaphragm and the inner and outer clamping plates are clamped tightly on the shaft.
Valve rattling: increase the outlet or inlet head.
Common air-operated diaphragm pumps are mainly classified as: engineering-plastic diaphragm pumps, aluminum-alloy diaphragm pumps, and QBY-type air-operated diaphragm pumps.
3. The air valve of the air-operated diaphragm pump freezes:
Check whether the moisture content of the compressed air is too high, and install air-drying equipment.
4. Bubbles appear at the outlet of the air-operated diaphragm pump:
Check whether the diaphragm has ruptured, and check that the clamps are tight, especially the inlet pipe clamp.
Warning: Before servicing the diaphragm pump, first disconnect the compressed-air supply line from the pump and bleed off the air pressure inside the pump. Disconnect all lines connected to the pump's inlet and outlet, then drain the fluid inside the pump into a suitable container. Wear a protective cap, safety glasses, and gloves.
5. The air-operated diaphragm pump does not move or runs very slowly:
1. Check whether the screen or air filter at the pump's air inlet is clogged with debris.
2. Check whether the air valve is stuck, and clean the air valve with a cleaning fluid.
3. Check whether the air valve is worn, and replace parts as necessary.
4. Check the condition of the sealing parts in the center body. If they are severely worn, an effective seal cannot be achieved and air will escape from the air exhaust port. Because of the special design, use only GLYD rings.
5. Check whether the piston inside the air valve moves normally.
6. Check the type of lubricating oil. If the lubricant added has a higher viscosity than the recommended oil, the piston may stick or run abnormally. We recommend using a light, anti-freeze lubricating oil (anti-freeze oil of ISO grade 15 / 5WT).
So when operating and servicing one, please follow procedures based on how the pump actually works. Starting today, our team will share knowledge about the use and repair of various pumps through articles and videos.
When an air-operated diaphragm pump fails to work, based on years of customer feedback collected by pump manufacturers, the problem falls into two categories: in the first, the diaphragm does not move, meaning there is no sound of normal positive-displacement action; in the second, the diaphragm moves back and forth, but no liquid is discharged from the outlet. The second case is classified as a "no power" problem in positive-displacement pumps. Today we will first show you how to quickly diagnose the first case.
If you encounter a situation where the diaphragm does not move after air is supplied to the pump, first inspect the pump's muffler. The muffler will show one of two symptoms: leaking liquid or leaking air:
When the air supply is connected and the muffler leaks liquid, it indicates that the seal between the motor (air) end and the liquid end of the air-operated diaphragm pump has failed, because the diaphragm has ruptured or the diaphragm clamping plate bolts have loosened. In this case, simply remove the diaphragm, inspect it, and replace it.
When the air supply is connected and the muffler leaks air, it indicates a problem with the internal seal of the pump's motor (air) end. In this case, simply open the motor cover and inspect the internal O-ring.
We should remind you, however, that the O-ring may be obviously worn or cracked; alternatively, it may simply be fouled with too much dirt, in which case you only need to remove and wipe it clean.
What are the possible causes when an air-operated diaphragm pump won't start?
1. The air-operated diaphragm pump runs, but the flow is low or no liquid is discharged at all:
1. Check the pump for cavitation, and reduce the pump speed to allow liquid to enter the liquid chamber.
2. Check whether the valve balls are stuck. If the process fluid is incompatible with the pump's elastomers, the elastomers will swell. Replace them with elastomers of a suitable material.
3. Check that the fittings at the pump inlet are fully tightened and leak-free, especially the clamp near the inlet-side valve ball, which must be tight.
2. Product flows out of the air exhaust port:
Check whether the diaphragm has ruptured, and check that the diaphragm and the inner and outer clamping plates are clamped tightly on the shaft.
Valve rattling: increase the outlet or inlet head.
Common air-operated diaphragm pumps are mainly classified as: engineering-plastic diaphragm pumps, aluminum-alloy diaphragm pumps, and QBY-type air-operated diaphragm pumps.
3. The air valve of the air-operated diaphragm pump freezes:
Check whether the moisture content of the compressed air is too high, and install air-drying equipment.
4. Bubbles appear at the outlet of the air-operated diaphragm pump:
Check whether the diaphragm has ruptured, and check that the clamps are tight, especially the inlet pipe clamp.
Warning: Before servicing the diaphragm pump, first disconnect the compressed-air supply line from the pump and bleed off the air pressure inside the pump. Disconnect all lines connected to the pump's inlet and outlet, then drain the fluid inside the pump into a suitable container. Wear a protective cap, safety glasses, and gloves.
5. The air-operated diaphragm pump does not move or runs very slowly:
1. Check whether the screen or air filter at the pump's air inlet is clogged with debris.
2. Check whether the air valve is stuck, and clean the air valve with a cleaning fluid.
3. Check whether the air valve is worn, and replace parts as necessary.
4. Check the condition of the sealing parts in the center body. If they are severely worn, an effective seal cannot be achieved and air will escape from the air exhaust port. Because of the special design, use only GLYD rings.
5. Check whether the piston inside the air valve moves normally.
6. Check the type of lubricating oil. If the lubricant added has a higher viscosity than the recommended oil, the piston may stick or run abnormally. We recommend using a light, anti-freeze lubricating oil (anti-freeze oil of ISO grade 15 / 5WT).