Mid-Atlantic Services sells a broad line of pumps and we deliver quite a few of them during our busy season. We also carry a wide variety of parts as most of our customers use their equipment during a very short window of time during the spring and can’t afford down time due to a lack of repair parts.
Some of the most common parts we sell are ceramic and carbon rotating pump seals. Usually I don’t give them much thought when a customer orders a set. However, the other day a customer asked me how to install one. This made me think that there are probably many other pump users who would appreciate a definitive set of instructions on how to replace a seal. For the purpose of this discussion, we are talking about centrifugal pumps only and not roller type pumps.
Every new pump we sell comes with a detailed parts and instruction booklet which outlines the procedures which I will explain. But, after a few years, when the seal quits its job of keeping liquid from leaking around the pump shaft, often these instructions can’t be found. Another good source of information is the website of the pump manufacturer. Instructions are usually found under specifications or literature for the particular pump in question.
Most centrifugal pumps have very similar seal assemblies consisting of a stationary seal with a ceramic face and a rotating seal with a carbon face. Many companies also offer severe service seals made of silicon carbide at a much higher cost. All of these kinds of seals replace in the same way.
Once the volute housing and impeller are removed, the rotating portion part of the seal can be removed from the shaft, being careful not to scratch or damage the shaft. Inspect the shaft at this time where the seal rides for any scratches or grooves which would damage the new seal. If found, replace the shaft.
The stationary portion can now be removed with a screwdriver or two if necessary on some pumps, while others require the shaft be removed completely. This is also a good time to inspect any bearings on the shaft for wear and roughness. At this point, it is very important to clean the machined area where the stationary portion will be pressed into. This can be done with a screwdriver or a rotating wire brush. If there is an O-ring or rubber gasket on the shaft behind the seal, this is the time to replace it also.
Next, apply non-hardening Permatex II or Rector seal pipe dope to the sides of the stationary seal and place in seal recess of pump. Some manufacturers also recommend LPS or WD40. All will work fine. You can use a plastic pipe nipple to tap seal into recess evenly. Now, slide rotating seal onto shaft, being very careful not to damage seal on leading edge of pump shaft. Re-install impeller, being sure to install key in shaft. Replace volute housing and tighten bolts.
One point worth mentioning here is that when you disassemble your pump, be sure to keep the model/serial number tag and replace at final assembly. This makes it much easier to supply the proper parts for the pump in the future. Identifying similar pumps from only a description is very difficult and time consuming, not to mention the problem of having wrong parts shipped back and forth.
Running a pump dry is the biggest cause of seal failure, so be sure the pump is well primed with liquid before initial start-up. It would be a shame to burn up your new seals right from the beginning.
And finally, there is an excellent video of seal replacement on www.acepumps.com. On the left navigation bar, choose Product Literature. Scroll down until you see Instruction Sheets. The last one is the one you want: Field Seal Replacement Service Video.