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The seal in your Banjo pump is a wearable part. The pump seal has to be able to move and still keep the product from leaking. The standard seal that we install into our poly pump is made of carbon and ceramic, with EPDM rubber and a stainless steel spring and cup. We also offer FKM (viton type) and Buna as an alternative when pumping a material other than a water base material. The standard seal for our cast iron and stainless steel pumps is FKM (viton type). An EPDM seal option is available.

Before you start your pump, make sure to fill the pump first with the material you are pumping. This will keep the seal lubricated and cool until the product starts to pump.

If you run your pump dry, this can damage the seal and cause the pump to leak. When the pump is run dry, the ceramic seal will heat up. When the product starts to ow across the ceramic, it will cause it to cool very quickly. When the ceramic cools like this, it will get very small cracks and will no longer seal.

You can also damage the seal by “DEAD HEADING” the pump. When you have a valve on the outlet side of the pump and you close it while the pump is running, this is called dead heading. When you do this, there is not any uid going across the pump seal to cool it. What little liquid that is in the pump will dramatically increase in temperature and not be able to cool the seal ef ciently. Once you open the valve and let the material ow again, it will be much cooler than the seal, thus cracking the ceramic.

Another cause of the seal going out is using the wrong type of seal for the material you are pumping. If you are going to pump a different material other than water, please check the chemical chart for compatibility on our website Chemical Resistance Chart to see what type of rubber would be best.

Chris Thompson
...and cavitation.

I would even offer one more common cause kray.....cavitation.   Pumps will cavitate due to a number of reasons, but the most common one I've seen is a reducer on the intake side of the a 3" pump reduced down to a 2" inlet hose.   The starved suction causes cavitation which is actually water "boiling" when the pressure is so low on the intake side that air bubbles come out of the water.   As soon as those bubbles reach the higher pressure side of the impeller, they burst and you get a million little water hammers going on.   Those shock waves wear out seals quickly!   I've seen it too many times.