Leaks are never a good thing, whether you’re talking about a faucet in your kitchen, the engine of your Chevy, or an air-operated double diaphragm (AODD) pump at your plant.
A leak indicates something isn’t working correctly, and in the case of an AODD pump leak, you want to promptly fix it to prevent further damage to pump components. Depending on what type of material you’re pumping, a leak could cause a substance to gum up the pump’s center block and air side, which could ultimately require you to replace the entire center block. A repair like that could take your equipment offline, costing you time and money.
That's why it’s better to find and fix a leak, before it becomes a major maintenance problem—or worse, a safety concern.
The good news is, many AODD pump leaks can be easily identified and remedied, so you can get your machinery back up and running in no time. You just have to know what you're looking for.
COMMON AODD PUMP LEAKS & WHAT CAUSES THEM
There are a few basic reasons an AODD pump may leak in the first place. The most common one is loose hardware. Many people don’t realize that AODD pump hardware may become loose over time due to transportation, expansion and contraction caused by temperature changes, among other factors. The hardware simply needs to be re-torqued to the pump manufacturer’s specifications before pump installation or anytime you suspect it’s loose.
AODD pump leaks can be the result of a flooded suction, which is caused by too much downward pressure coming into the pump. This pressure has the potential to create a leak at the bolt hole locations. If high suction pressures are causing issues or concern, you can move the pump up where the centerline is closer to the fluid level.
Another common leak source is a weakened diaphragm, which can be caused by running a pump dry for a prolonged period of time. Dry running the pump creates an imbalance between the air and wet sides, eventually weakening it and causing a leak. Avoid this situation by not running the pump dry. If needed, a pneumatic controlled liquid level controller is available to help combat dry running.
HOW TO IDENTIFY AODD PUMP LEAKS
Breaking down the pump to look at the diaphragm can help you diagnose common leak-related problems.
|Diaphragm Observation||Potential Issue||What to Do About It|
|Discoloration or cracking||Excessive heat or chemical attack||Check chemical compatibility of elastomers and/or temperature of product.|
|Bubbling around the edge||Excessive heat or chemical attack||Ensure chemical compatibility of elastomers and/or temperature of product.|
|Wear marks on one side||Excessive suction-side pressure or imploded air side||Observe gauge on suction side for increased pressure. Try to keep below 10 psi (0.7 bar) of NPSH.|
|Star pattern cracking||Dry running||Shut pump down when not in use. Potential application for liquid level controller.|
|Outer diaphragm plate imprint||Over-torquing||Follow manufacturer torque specifications.|
The location of a leak also can indicate what the problem may be. For example, exhaust leakage indicates a diaphragm failure or a center bolt hole deformation due to higher pressures or a lower torque used on the outer plate than recommended. A leak where the manifold connects to the chamber may be the result of over torquing (crushing the sealing surface) or under torquing of the manifold hardware.
AVOID LEAKS WITH PREVENTIVE PUMP MAINTENANCE
To prevent AODD pump leaks from occurring, always remember to take the following steps:
- Check pump hardware prior to installation
- Ensure suction conditions are below recommended pressures
- Follow manufacturer’s torque specifications during rebuild
The last step is key. As noted earlier, AODD pump leaks are often caused by improperly torqued hardware upon installation. Right out of the box, it’s vital to follow all of the manufacturer’s recommended torque specifications. After all, leaks typically occur at the pump’s weakest point, so you’ll often see leakage where you haven’t properly re-torqued the hardware, such as bolts and diaphragm plates.
Another important aspect of optimal pump performance and maintenance is to conduct a complete parts replacement when doing a repair. Once you’ve taken your pump apart, it makes sense to reduce the risk of future downtime by replacing all the components together. For example, if you need one new diaphragm, replace both of them, not just the faulty one. If you’re going to replace valve balls or valve seats, replace all four of them as opposed to just the one that’s causing a problem. Most likely the others will need to be repaired soon anyway, so upgrade them all at the same time. For your convenience, Versamatic’s service kits include everything you need to maintain your pump at once rather than one component at a time.
Next up in the AODD Pump Easy Troubleshooting Tips series are articles on suction malfunction and erratic operation. Stay tuned for those blog posts, and remember, Versamatic pumps are some of the most easy-to-troubleshoot AODD pumps on the market.