Locking Wire / Safety Wire
The lock-wiring of bolts is a locking method adopted from the aviation industry. In brief, the method involves threading a special stainless wire through a hole in the bolt head, which is twisted and locked to the next bolt or structure, thus preventing the bolt from rotating and loosening. The wire can be used to lock a maximum of three bolts in a row, as shown in the illustration.
Areas of use:
used extensively for locking external bolted connections on drilling and pipe-handling equipment. Often used where there are no through-bolts and / or it is necessary to be able to easily check the locking visually.
The locking wires may stretch, break or corrode if not properly fitted, allowing fastener rotation and loosening when exposed to dynamic loading. Haven’t you worked with this before? Then it is important to use a safety wire practice board first.
Examples of locking wires in practice.
Best practice reccommendations
- Split pins must be bent sufficiently to prevent them from falling out
- Where there is a danger that personnel will be exposed to the sharp ends
- When hoisting personnel or loads, always use 4-Part shackles (bow, pin, nut and split pin)
- Tractor or hitch pins, hairpins, welding rods or home-made pins must not be used
- Split pins should be made of a stainless steel suitable for the operational environment
- It is a requirement that cotter pins are inspected regularly and replaced when not serving the necessary function
- Linch Pins, R-Clips, Spring or Roll Pins, Nappy Pins, or any other type of pin device that can spring or be knocked out should be avoided when used on lifting equipment or for securing of equipment or structure at height. Carefully assess all applications and follow OEM guidance.
Securing pins of the type shown in the images at the top of this page, should not be used in lifting equipment
Securing pins shall provide secondary retention
Securing pins shall be of the proper size and quality
Securing pins shall be secured by wire (where this is appropriate) to prevent dropping during removal
It is a requirement that securing pins are inspected regularly and replaced when necessary
Areas of use:
Scaffolding bolts, security bolts on removable railings, claw couplings and securing brackets on gas cylinder racks, etc.
The pin in the top image is usually used in the diving and subsea industry