50 Series Mechanical Seal
50 Series Mechanical Seal

50 Series high pressure mechanical seal

(API 682 Type A)


The latest generation high pressure API 682 50-series mechanical seal is designed for high pressure applications, such as crude oil, hot water, light hydrocarbons, including VOCs, at oil producing, oil tranportation, oil refineries and petrochemical plants, power plants. Depending on the application, it is made single, tandem or double.

50 - series seals are used for the same applications as the followings seals:
H7/H75/SH by Burgmann Germany
QBQ/DHTW by Flowserve, USA
8B/59/58/RREP by John Crane, USA

Typical applications include

  • Main crude oil transportation pumps - single and tandem
  • Boiler feed water pumps - single
  • Multi-phase pumps - double
  • Flashing hydrocarbons under high pressure - tandem or double.

High pressure capability

Tests show that a traditional seal has leakage rate of 150-250 ml/hour at 50 bar, 3000 rpm, oil 35°C. Why? Because of high pressure, seals faces bend, and the small gap between the faces goes out of parallel. The gap becomes conical. Because of this, the fluid film in the gap does not act as in a sliding bearing anymore. Friction and wear encrease. It is clearly seen during testing: when the test rig is swithed off, the shaft stops immediately because of high friction. And when the seal is disassembled after an 8 hour run, initial wear is already seen on the faces.

In the 50-series seal, faces have been carefully designed using FEA (finite element analysis). The good results are immediately seen during testing: when the test rig is swithed off, the shaft rotates for 8-10 seconds because of inertia (it points to low friction). And when the seal is disassembled after an 8 hour run, NO initial wear can be seen on the faces. Leakage rate is as little as 15-30 ml/hour at the same 50 bar, 3000 rpm, oil 35°C. The leakage rate is 10 times less!

Seal advantages

  • Excellent for high pressure applications
  • Stationary springs allow for high speed
  • Special wear resistant, non-sticking materials are available for seal faces (see below).

Special hard faces available

  • Further resist deformation
  • Anti-stick, low wear properties
  • Can operate in non-lubricating fluids such as hot boiler feed water.
  • See the photo of the two seal rings with different wear after similar high PV tests (special non-stick grade on the left vs normal Sic on the right).
Technical Data
Temperature From -50 up to +315°C
Dynamic Pressure Up to 200 bar
Static Pressure Up to 330 bar
Linear Speed Up to 50 m/sec

See also:

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