Item Description
1 Seal face
2 Stationary seat
3 Bellows
3a Gasket
4 Spring
5 Ring
5a Locking ring
5b Collar



  • Rubber bellows mechanical seal
  • Unbalanced
  • Single spring
  • Independent of direction of rotation
  • Short axial installation length


Mechanical seal for large-series cold water pumps, produced in millions of units per year. The BT-AR owes its success to the wide range of application, the short axial length (this allows for more economic pump construction and saves material), and the best quality/price ratio. The elasticity of the bellows design enables a more robust operation.

The BT-AR can also be used as a multiple seal in tandem or back-to-back arrangement when the product media cannot ensure lubrication, or when sealing media with a higher solids content. Installation proposals can be provided upon request.

Operating range

Shaft diameter: d1 = 6 … 70 mm (0.24" … 2.76")
Pressure: p1* = 6 bar (87 PSI),
vacuum … 0.5 bar (7.45 PSI) up to 1 bar (14.5 PSI) with seat locking
t* = -20 °C … +120 °C (-4 °F … +248 °F)
Sliding velocity: vg = 10 m/s (33 ft/s)

* Dependent on medium, size and material


Seal face:
Carbon graphite antimony impregnated (A), Carbon graphite resin impregnated (B), Carbon graphite, full carbon (B3), Silicon carbide (Q1, Q6), Tungsten carbide (U), PTFE glass fiber reinforced (Y)
Steatite (X), Aluminium oxide (V, V1), Silicon carbide (Q1, Q6, Q7), Tungsten carbide (U), Cr steel (E), CrNi steel (F), CrNiMo steel (G)
NBR (P), EPDM (E), FKM (V), HNBR (X4)
Metal parts:
CrNi steel 1.4301 (F), CrNiMo steel 1.4401 (G), CrNi steel 1.4057 (F1)

Standards and approvals

  • KTW
  • W270
  • ACS
  • WRAS
  • NSF
  • DM 174/04
  • FDA

Product variants

Seal faces with brazed tungsten carbide (U) for abrasive media. Elastomers and diameter range the same as BT-AR. The BT-AR3 is the right choice of seal for use in high duty applications or when abrasives (e.g. waste water) could damage the seal faces.

Item Description
1 Seal face housing
1a Brazed seal face
2 Stationary seat housing
2a Brazed stationary seat
3 Bellows
3a O-Ring
4 Spring
5 Ring
5a Locking ring
5b Collar