A thread protector is a member of a family of disposable or reusable parts designed to close, protect, or mask screw threads. They are used to protect threaded parts against damage, corrosion, ingress of contaminants, and as cosmetic finishes. Thread protectors are used to shield threaded ends on pipes, gas cylinders, oil refinery equipment, and firearm barrels. Thread protector designs range in complexity from simple soft rubber sheaths designed to pull over a thread to multifunction machined steel caps incorporating several ancillary features.
Screw threads are generally fairly sensitive to physical damage and corrosion. When threaded parts or items with exposed threaded fittings are stored or transported, they need to be protected. The humble thread protector not only serves to ward off damage to the threads themselves but also stops dust, moisture, or other contaminants from entering containers via exposed fittings.
Corrosion protection is another important role of a thread protector. Threads cut into galvanized pipes remove the surface protection; as a result, they can be particularly susceptible to corrosion and should be covered with a thread protector. They also prevent oil from contaminating the thread and posing an explosion risk. Often a thread protector is used to mask threaded connections when newly fabricated parts are painted.
Thread protectors also serve a mechanical purpose on threaded components in environments such as the petroleum industry. Here protectors may have additional features such as lifting rings included in their design. These caps not only protect the threads on casings and drill string pipes but also serve as connection points for lifting them. These thread protectors are heavy duty cast steel items typically featuring integral projections which aid in tightening them onto the pipes.
Protective caps are also used on firearm barrels which are threaded to accept sound and flash suppressors. These thread protectors are generally better finished than their utilitarian industrial siblings and offer both protection and a cosmetic treatment. They are often knurled to facilitate tightening and sometimes include integral front sight mounts. Gun barrel protectors are generally made of steel or aluminum and typically stamped or laser engraved with the relevant thread pitch information.
Thread protectors are not always threaded and many are no more than simple, extruded silicone rubber sleeves. These are most commonly used to cover the threads on precision bolts, CO2 cylinders, and small diameter threaded pipes. Materials used for push on protectors are generally silicone rubber, vinyl, and polyethylene. These caps can include integral stoppers and may afford a degree of pressure sealing in addition to protecting the threads. This type of protector is often used in the air conditioning and refrigeration industry to seal pipes and service points against contaminant ingress.