PRE-APPLIED THREAD LOCKING & SEALING

Threadlocking is used to prevent fasteners becoming loose under conditions of vibration or no load. There are two basic concepts for pre-applied thread locking,

*The jamming action of a wedge of material (a prevailing torque patch)

*The chemical locking action of an adhesive (a micro-encapsulated adhesive patch)

A Prevailing Torque Patch is a reusable nylon or polyester patch, applied to the thread of the fastener. When the fastener is assembled into a mating thread, the patch forces the threads of the fastener to be wedged tightly against the mating thread, thus providing resistance to loosening. The amount of nylon applied is closely controlled and is designed to ensure a good lead-in and provide a uniformly gradual development of locking torque to a pre-determined specification.

This type of patch is usually better known by their proprietary brand names and they can be supplied with 180' or 360° thread coverage. A Micro Encapsulated Adhesive Patch is a `one-time' use adhesive bond, which offers a lower assembly torque than a nylon prevailing torque type patch, but gives a high breakaway torque and the locking reliability of most other self-locking fastener types.

Pre-applied adhesives are a dry to touch, two part epoxy system in micro-encapsulated form. The material is positioned in a 360° band around the threads of the fastener, which when rotated against its mating thread, causes the capsules of adhesive to burst, releasing the material in and around the thread flanks, which then cures and forms the locking bond. Various types of patches are available, each offering different strength and temperature performance and because of the 360° thread coverage, they also give excellent sealing properties as well as thread locking.

A Sealing Patch is also available, which comprises a pre-applied PTFE type sealant, commonly used to pre-coat threaded parts like plugs and pipe threads. These patches offer no locking properties, but upon installation, give instant sealing against gases and liquids and they can be readjusted after assembly, without affecting sealing ability.