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Environment Determines Seal Type

Guide to Mechanical Seal Types and Component Properties - Page 4

The balanced seal has the same opening area as the unbalanced seal, but the closing area has been reduced in relation to the face area. Because force = pressure x area, reducing the closing area reduces the closing force: less heat is generated, and the seal generally has a longer life.

Seals can be further classified in a number of ways. There are four additional classifications of mechanical seals which can be described by distinct characteristics:

  • Rotary spring, springs or bellows rotate with the shaft.
  • Stationary spring, springs or bellows do not rotate with the shaft.
  • Non-Metallic, no metal parts come in contact with the fluid being pumped.
  • All Metal, metal parts are used exclusively where application temperatures require it.

Temperature Chart

Temperature Inside Outside
Balanced Unbal. Balanced Unbal.
Up to 250 °F
Up to 120 °C
* * * *
250 °F to 400 °C
120 °F to 205 °C
* * *
Up to 400 °F
Up to 205 °C

Pressure Chart

Pressure Inside Outside
Balanced Unbal. Balanced Unbal.
Up to 150 psi
Up to 3.5 kg/cm2
* * * *
150 psi to 300 psi
3.5 kg/cm2 to 21.1 kg/cm2
* *
Over 300 psi
Over 21.1 kg/cm2

Speed Chart

Speed Inside Outside
Balanced Unbal. Balanced Unbal.
Up to 1500 fpm
Up to 7.6 rpm
* * * *
1500 to 3000 fpm
7.6 to 15.2 rpm
* * *
Over 3000 fpm
Over 15.2 rpm
  • fpm = Feet per Minute
  • rpm = Revolutions per Minute
  • psi = Pounds per Square Inch
  • kg/cm2 = Kilograms per Centimeter Squared

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