Sizing Single Spring Seals

Finding a replacement seal for your existing single spring seal is not as difficult as you may think.  As much as every seal manufacturer will tell you there seal is by far the best the truth is they are all pretty much the same design wise. The key is getting one that fits onto your shaft and into your pump.  To accomplish that your going to need to know some critical dimensions:

1) Shaft Size (or sleeve size) of your pump

2) Seal Head O.D.

3) Working Length of Rotating portion of the Seal

4) O.D. of the Stationary (or the bore dimension where the stationary press fits into).

5) Thickness of the Seat.

Measure the Seal Head I.D. Add approximately .016" to account for the squeeze the bellows must have to seal the shaft.
Measure the Rotating Units "Free Length"
Measure the Spring "Free Length"
Measure the seal head O.D. to be sure the seal will fit inside the stuffing box bore of the pump.
Determine the "Working length" of the seal.

Spring "Free Length" / 2 = Spring compressed length

Rotating Units "Free Length" - Spring compressed length = Rotating Units "Working Length". 

Because the seal your measuring may be used, or from another manufacturer the working length is considered an approximation.  By examining the dimension listings on you should find a seal that is close to the Working length you calculated from the above formula.


Measure the O.D. of the seat or measure the Bore the seat will press into. If measuring the Outside Dimension of the seat (as pictured) SUBTRACT approximately .016" to account for the rubber squeeze required for the interference fit of the seat.


Once you know the above dimensions,  look at the following index and narrow down which seal is the one you want. The part number will be listed on the right hand side. There may several seals of the same type that vary by the materials of construction.  You will want to know the elastomer type (Buna, Viton, EP) and the seal face materials (Carbon, Silicon, Tungston, Ni-resist, Ceramic).  All of our single spring seals are made of stainless steel.

If you have any questions you can contact our inside sales staff at 714-361-1435.

We also have more detailed information on mechanical seals and their designs at