Locking Wires Best Practice

Lock / locking wire (also known as indicator wire) should only be applied by competent persons specifically trained in its correct use.

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.

Examples of locking wires in practice

Split Pins / Cotter Pins

A split pin is a metal fastener with two 'tines' that are bent during installation. Also known as a ccotter pin or cotter key (USA), These are used to secure other fasteners such as bolts, nuts and clevis pins

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/safety pin

Some best practice recommendations:
Securing pins of the type shown in the images 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

Securing Devices

Wires Chains and Connectors

Best practice recommendations

  • Securing devices must be dimensioned in accordance with the equipment supplier’s calculations. The quality of materials used must be consistent throughout the entire assembly
  •  Only use acid-proof securing wire (AISI 316, type 7x19 IWRC)
  •  All connectors/snap hooks/carabiners must be made of acid proof steel (AISI 316), include screw lock or self-lock gates and include captive eyes
  • Chain must be made of acid-proof (AISI 316) or galvanised steel
  •  Shackles for use with securing devices should have nuts and cotter pins
  • The length of the securing wire must be as short as possible to minimise the potential fall energy
  • Securing devices must be installed, maintained and inspected in accordance with the instructions provided in the supplier’s user manual or maintenance instructions
  • Ensure devices are suitable for the operation and the environment, with due regard to potential galvanic corrosion
  • Where self assembly securing wires are used, these must be assembled and crimped by a competent person
  • All securing devices and all attachments to tools and equipment shall be documented and have traceability information. As a minimum this shall include batch marking, the name of the manufacturer/importer, production year, and information about the maximum load/ WLL
  • In addition, information about the material type, product standard and an installation / maintenance guide must be available.

Always check design ratings of equipment before installing securing devices as integrity may be compromised.Never re-use securing wires, connectors or chains that have sustained shock loading.

All securing devices and all attachments to tools and equipment shall be documented and have traceability information. As a minimum this shall include batch marking, the name of the manufacturer/importer, production year, and information about the maximum load/WLL.

Installation of Wire Clamps

Incorrect installation of wire clamps is a challange in de thindustry

Best practice reommendations:

  • Wire clamps must be of the correct number and sized to the dimension of the wire.
  • It is a requirement that wire clamps are assembled, inspected and maintained in accordance with the manufacturer’s user manual / maintenance instructions
  • Bull-dog style clamps should not be used. 
  • Wire clamps of the u-bolt type must not be used in connection with lifting operations

Correct installation of iron grip wire clamps

Wire rope diameter
mm                          inch
3-9                           1/8 - 3/8
10-16                       3/8 - 5/8
17-20                       5/8 - 3/4                     
21-26                       3/4 - 1
27-37                       1 - 1 1/2

This displays the number of wire clamps needed to secure a wire rope with a specific diameter.

Minimum number of wire clamps
per piece