Threaded shaft seal

Threaded shaft seal (GWD)

The threaded shaft seal is the standard seal for WITTE EXTRU and BOOSTER pumps, however, it can also be used as a special variation for POLY pumps. It is also described as a viscoseal and can optionally have a heated or cooled design. This dynamic seal can also be used for high temperatures. The application area of seals is generally determined by the suction pressure and the viscosity of the pumped medium. The viscosity of the medium, however, may also be influenced by tempering.


Components of the vacuum threaded shaft seal (POLY discharge pump)

  • Threaded shaft seal
  • Adjusting screw
  • Locked stuffing box
  • Pressure gauge
  • Product flange
  • Heating channel casing

  • Threaded shaft seal

    The purpose of the threaded shaft seal is to seal the drive shaft from the atmosphere. It can be combined with other seal types. The following variations are possible:

    • Threaded shaft seal as a stand-alone solution
    • Vacuum threaded shaft seal with stuffing box
    • Vacuum threaded shaft seal with radial shaft seal ring
    • Vacuum threaded shaft seal with double mechanical seal
  • Adjusting screw

    WITTE gear pumps have lubricated friction bearings. In particular for the highly viscous media for which POLY discharge pumps are used, it must be ensured that there is sufficient lubrication. The bearing lubricating flow is throttled through the adjusting screw to ensure a reliable functioning GWD on the suction side with a vacuum condition.

  • Locked stuffing box

    The locked stuffing box prevents the entry of oxygen into the pump and the reactor when the pump stops.

  • Pressure gauge

    The pressure of the throttled lubrication flow is controlled through the pressure gauge.

  • Product flange

    The product flange is equipped with a heating channel. The temperature is controlled through this and is calibrated exactly to the medium and the process. This ensures that the viscosity of the melt remains constant. That is particularly important for highly viscous melts in polymerization.

  • Heating channel casing

    The heating channel in the casing ensures that the melt also has a constant viscosity in the area of the gear wheels.


Variations of the WITTE threaded shaft seal

Vacuum threaded shaft seal with stuffing box

The vacuum threaded shaft seal (vacuum GWD) is a special design of the threaded shaft seal and can also be heated or cooled. The flow to the suction side is stopped through a needle valve so that the throttled product forms a barrier. This makes it possible to operate the pump on the suction side under vacuum conditions. Since it is a dynamic seal, it is often combined with a double locked stuffing box. This combination also prevents air from entering the reactor during a standstill.


Can be used for the following pump types:

Operating parameters

Pressure suction side:
Vacuum up to max 10 bar
Viscosity:
10.000 – 40,000,000 mPas
Temperature:
max. 350 °C

Vacuum threaded shaft seal with lip seal

The vacuum threaded shaft seal can alternatively be used with a leap seal as a static shaft seal. As with the stuffing box packing, the buffering medium forms the required barrier to reliably prevent air from entering through the shaft seal if the pump stops working.


Can be used for the following pump types:

Operating parameters

Pressure suction side:
Vacuum up to max 10 bar
Viscosity
10,000 - 20,000 mPas
Temperature:
max. 275 °C

Threaded shaft seal standard design [GWD]

The threaded shaft seal is the standard seal for WITTE melt pumps from the EXTRU and BOOSTER series. It is a dynamic seal for high viscosities and suction pressures. It can have a heated or cooled design. The dynamic seal is suitable for high pressures and temperatures. Its area of application is restricted through the suction pressure and the viscosity of the pumped medium (at least 10 Pas). If necessary, the viscosity can be increased through additional cooling.


Can be used for the following pump types:

Operating parameters

Pressure suction side:
1 to 120 bar
Viscosity:
10,000 - 40,000,000 mPas
Temperature:
max. 450°C