SUBJECT: The rubber bellows seal 11-11

Available from a number of seal companies (the Crane #1 is typical), and manufactured in a variety of materials, it looks like the following illustration:

You will find this seal used in water pumps and oil pumps, but it is seldom used with chemicals in the process industry. In recent years one manufacturer is mounting the seal on a cartridge sleeve and promoting it as a slurry seal.

To the casual observer the seal appears to have several real advantages:

Let's look at each of these features in detail and see if they really are an advantage:

Cost

Easy to install

Availability

Non Fretting

Here are some additional things you should be aware of:

What is my personal opinion of this type of product ? It is probably the best original equipment seal (O.E.M.) made and the worst replacement seal ever designed. I do not like it for the following reasons:

If you are willing to invest in a high priced, balanced design, cartridge mounted version of this seal; then there is something to be said for its performance in slurry applications where you are trying to cut down on water flushing.

Given the choice you will probably be better off with the stationary version, but you will still have to contend with all of the points mentioned above.

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