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Identifying a mechanical Seal

Every day we receive mechanical seals from mechanics that either needs us to identify the seal so we can replace it, or need us to repair it. In either case, the procedure is the same. Identifying the pump, impeller, suction and discharge sizes is of little help. Pumps are placed in a wide variety of applications. The seal has to be designed for the application more so than the pump. Pump manufactures will place multiple configurations of seals into the pumps they sell so the pump model alone is not the answer.

To start, it’s always helpful if you can get part numbers off of the seal. Major manufacturers such as John Crane, Flow Serve, and Chesterton will place part numbers on the seal that reflect the Elastomer, Seal Faces and metallurgy of the seal.

If there is no part number or the part number has been worn away by the service, it’s still possible to identify some of the components. Start with the weakest link elastomer. Deductive reasoning will get you in the right ballpark. First investigate the rubber components. Do they look chemically attacked, melted or are they brittle or hard? If they are still flexible and in good condition, we know at least that the elastomer was compatible with the service. If they are not, we know we need a different elastomer anyway. Starting with Temperature, and the Application, you can narrow down the compatible elastomers. If it’s over 325 F it’s likely Viton or Aflas. If it’s over 325 F and a chemical application a chemical compatibility chart will get you there.

Next, you want to consider the seal faces. If you are not color blind, this is pretty straight forward. If the seal face is white, it’s Ceramic. A metal seal face like brass, bronze or Aluminum bronze, it will look it. If it’s Silicon carbide it will be grey and light in weight. Silicon Carbide is in the same family as Ceramic. If it’s Grey to silver grey and heavy it’s Tungsten Carbide. If it’s Black it’s Carbon. Most seal faces are one of the above. One exception is if you have a spray on coating. These are rarer than they used to be simply because they fail faster and as a result, have fallen out of favor.

Each seal has a method of energizing the seal faces together. Usually, it’s a spring. There are 3 types of spring sets: a single spring, multiple springs, or a wave spring. Wave springs are the least common. But are used when minimal space is available in the pump. Single springs are the most common, and often used in 80 % of seal applications (water service). If it is not a spring, it will be a metal bellows. Metal Bellows are more expensive but effective in difficult applications like boiler feed pumps.

The least critical component (because it takes a while to fail) is the metallurgy. Most seals are made of brass or bronze & 304 or 316 Stainless. Monel is used in seawater applications, and Hastelloy is used in high-temperature applications.

Armed with your identification of materials, an e-mailed digital image, a description of the service parameters and a few dimensions we should be able to identify the seal you need. Of course, you can always shoot us an e-mail for help at or call 714-361-1435


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