Performance seals for batching mixers, dryers and agitators

Citation

(2002), "Performance seals for batching mixers, dryers and agitators", Pigment & Resin Technology, Vol. 31 No. 6. https://doi.org/10.1108/prt.2002.12931fad.006

Performance seals for batching mixers, dryers and agitators

Performance seals for batching mixers, dryers and agitators

Keywords: Seals, Batch processes, Mixing drying, Agitation

The Mixerpac M-series, from the Flowserve range of mechanical shaft seals, can be configured to operate wet, dry, or with the latest non-contacting gas barrier technology. They are claimed to offer a genuine engineering breakthrough, providing the utmost in performance, application flexibility and economy (Plates 3 and 4).

They are designed for use with mixers, dryers and agitators used in the batch processing of pharmaceuticals, food, polymers, thermoplastics, adhesives, silicones and many other products. The Mixerpac M-series is claimed by Flowserve to be the only dual pressurised cartridge canister seal platform specifically engineered to accommodate the lower speeds, higher pressures and increased temperatures associated with modem mixing and processing equipment. The modular design reportedly permits adaptation to meet changing production requirements, eliminating unnecessary investment in additional seals.

Plate 3 The latest Mixerpac M-series mechanical shaft seals from Flowserve Ltd which accommodate wet, dry or gas barrier seal technology, suitable for mixers, dryers and agitators used in batch processing applications

Plate 4 Typical dry running VRA seal from Flowserve Ltd which offers dry running without cooling and can now be supplied with an optional sanitary gland for steam cleaning and sterilisation of interior components

The pre-engineered package permits interchangeability of seal housing, sleeves and glands for applications on liquid lubricated, dry running or full fluid film face technology. The simple changing of face seals enables the easy transfer from a liquid lubricated condition to a contacting gas seal, or even a non-contacting gas seal which allows operation down to 0 rpm. A full shaft run-out of up to 0. 1 25″ (3 mm) can also be accommodated, or whenever shaft wobble and other eccentricities are most severe.

The outside seal design is said to make it simple for both installation and inspection whether mounted directly on the shaft or as a cartridge design. The construction also distributes the drive torque to eliminate high stress areas with a flexibly mounted stationary insert reducing the potential of seal face distortion from gland bolt overtightening.

New features also incorporated in these seals include:

• •

  Fully pre-assembled rotating unit for easier assembly and handling with higher reliability.

• •

  A PTFE gasketed version, with improved carbon grades permitting dry-running without humidification up to 6 bar vessel pressure.

• •

  Reverse rotation permissible up to 0.4 m/sec, together with reverse pressure for enhanced safety in the event of barrier failure.

The seals can be supplied for shaft sizes from 2.000″ to 6.500″ imperial (50 to 160 mm metric). DIN versions for steel and glass lined vessels can also be supplied from 40 mm up to 220 mm (1 60 mm glass lined), together with a version suitable for sterilisation.

Flowserve also announce a range of VRA dry running seals, it describes as an economical, no- nonsense seal designed specifically for use with top entry mixers and agitators.

These products are single, outside mounted, balanced mechanical shaft seals which reportedly eliminate the need for buffer fluid systems, so preventing potential product contamination. A flexible rotor design compensates for shaft misalignment, while clearances, drive design, seal face dimensions and O-ring configurations have been optimised for a high run-out tolerance up to 0.150″ FIM. A double O-ring mounted stator prevents distortion, with various configurations also available to suit different host equipment types.

The seals are manufactured from self- lubricating carbon or filled PTFE which accommodate dry running without cooling. Long life and reliability are achieved by running in the dry vapour space at the top of the vessel, with heat quickly dissipated to ensure that seal face temperatures do not reach critical levels. Seal face flatness is also important to reduce gas leakage, while face deflection resulting from pressure or thermal variations is also limited to prevent leakage or seal failure.

The outside seal design is said to make it simple for both installation and inspection whether mounted directly on the shaft or as a cartridge design. The construction also distributes the drive torque to eliminate high stress areas with a flexibly mounted stationary insert reducing the potential of seal face distortion from gland bolt over tightening. Operating limits are stated to range from full vacuum to 200 psi (13.8 bar) at shaft speeds up to 350 rpm and temperatures up to 149°C (300°F).

Seals can be provided for shaft sizes 1.000″ - 7.000″ (25 mm to 178 mm), and an optional sanitary gland can be fitted which permits in-situ steam cleaning and sterilisation of interior parts.

Furthet details are available from Flowserve Limited. Tel: +44 (0) 161 869 1200; Fax: +44 (0)161 869 1235; E-mail:fsd-sales-uk@flowserve.com; Web site: www.flowserve.com