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Installing trip wires

Contrary to Piling rig confusion may lead to fatalities HSE will accept trip wires when they are properly located and installed.

However, this is rarely found in practice.

Advised by mechanical engineers, HSE has decided that the trip wires should be150 mm from the drill string surface.

HSE inspectors find trip wires up to 1 m from the drill string. On some rigs the wires can even be protected by the feed beam. This renders them ineffective. If the trip wire is not located close to the drill string then it is not providing protection for the drillers and another form of guard is required. This is usually a fixed or interlocked guard.

HSE is aware that adding a steel-framed mesh guard to a rig effects stability. We do not specify what material guards should be made from but encourage contractors to use a material which prevents access. When the guard is opened, the rotation speed should be reduced10 rpm.

At the current time, EN 791 is being revised and when republished is likely to require all rigs to be guarded.

Dr Donald Lamont is head of tunnel and ground engineering for the HSE and a member of the CEN committee for drill rigs

Improving standards

The Provision and Use of Work Equipment Regulations (PUWER) set out requirements for machinery safety. How that is achieved depends on the machine. Compliance levels with PUWER in the drilling industry have been poor but improving.

Machinery must comply with the EC Machinery Directive. CEN standards present manufacturers with a means of demonstrating compliance. Drill rigs, including CFA rigs, are covered by EN 791, whilst EN 996 applies to impact piling rigs.

Clause of EN 791 requires drill rigs to be equipped with trip devices close to the rotating drill string and accessible to operatives. These should be immediately and automatically actuated by a person becoming  entangled.

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