Screw and Seal Arrangements

Thayer Scale’s highly-experienced engineers design products and solutions with customers in mind. To minimize equipment downtime and to facilitate maintenance, we developed simple, straightforward systems for cleaning and replacing shaft seals—typically the only wear-items in our equipment’s normal service.

Screw seal arrangements are selected based upon the application and physical characteristics of the feeding material. Applications which require frequent changeovers and/or cleaning use the easily-replaceable standard seal arrangement. To minimize leakage and housekeeping, applications feeding fine powders use packing gland seals, while those feeding abrasive materials use purged cinch seals.

Our standard screw and seal arrangements are:

Easy to maintain

  • Our unique shaft and seal design features seals that are mounted or removed from equipment with a quick-release process screw; the design enables immediate seal cleaning, inspection, or replacement without additional tools or disassembly.


  • Seal construction comprises a carbon fiber (graphite) reinforced PTFE with a 302 stainless steel canted-coil energizing spring.

Designed to protect and extend longevity

  • The process screw boasts an adapter which acts as a seal gland surface. This adapter ensures seals do not turn with the process screw (they instead rotate inside the diameter of the non-rotating seals). Should the process screw experience abnormal damage, it can be easily disassembled, and the removable drive-shaft assembly can be reused on a replacement screw. Similarly, the rotating adapter and drive key can be reused or replaced in the field with minimal downtime.

To assemble and disassemble the process screw and adapter:

  1. Slide adapter over the process screw’s round stub shaft.
  2. Insert the process screw (and adapter) into the mating hole on screw-drive shaft. (Assembly and drive-key are now pinned together.)

To disassemble the screw drive shaft assembly, simply drive the pin out and withdraw the shaft assembly and adapter from the round-stub portion of the screw.

Designed to control damage:

  • If the screw becomes jammed, the spring pin will shear and protect the screw, reducer, and drive motor.