Common problems encountered while using an AODD

Here we define the common problems encountered while using an AODD (Air Operated Double Diaphragm) pump:

• Air passes directly through the exhaust without any diaphragm/shaft movement – The cause of this stalling is mainly due to damaged shaft or piston O-rings. There might also be a chance that there is not enough lubrication in the air side. To resolve this, put in a couple of spoons of oil at the air inlet and start the aodd pump at low pressure. As the pump begins to stroke, gradually increase the pressure.
• Material or chemical leakage observed from the air side or exhaust – The main reason is damaged diaphragms, which allow the chemical to enter the air side of the diaphragm pump. To resolve this, open the liquid side, clean the aod pump, and replace the diaphragm. Then open the air side, clean the piston, shaft, and spool. If needed, replace the O-rings, apply grease, and refit everything.
• AODD pump is running, but there is no suction or very low suction – There are two reasons for this:
1. There might be an air gap either in the suction line or in the chemical pump at the liquid contact parts. Check and tighten the nuts to resolve the issue.
2. The suction line might be more than a couple of meters, making it difficult for the AODD pump to create suction. Try reducing the suction height by keeping the double diaphragm pump close to the chemical.
• Insufficient flow rate or output pressure – This is mainly caused by low air pressure, or because the delivery line is too long with many bends in the liquid line, leading to frictional and gravitational losses. Wrong aodd pump size selection is also one of the major reasons.
• Diaphragm pump stops intermittently during operation – This might be due to back pressure from the liquid line, which causes the aodd pump to stall, or due to low air pressure/air volume. The required air pressure is generally 2–6 kg, and air volume depends on the air operated double diaphragm pump model:
• 1/2 inch AODD Pump – 8–12 SCFM
• 1 inch AODD Pump – 18–20 SCFM
• 1.5 inch AODD Pump – 30–35 SCFM
• 2 inch AODD Pump – 40–45 SCFM
• Choking or blockage – This is generally observed with viscous chemicals (e.g., cream, paste, etc.) or chemicals that dry over time (e.g., glue, fevicol, paint, etc.). To avoid this, always flush the diaphragm pump after every use. Whether the aod pump is used for one shift or for seven days non-stop does not matter—once the pump is stopped, flushing must be done. Use a cleaning agent, solvents, warm water, or normal water, and run it through the double diaphragm pump for 3–4 minutes.