Article Safety

Drilling down into industry safety

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Site investigation companies should expect increased HSE attention following the recent successful prosecution of CET Limited following an accident where a drill rig operator was forced several times through a 24cm gap between the mast and the auger. Guarding and stopping devices were considered inadequate and not in compliance with the Provision and Use of Work Equipment Regulations 1998 (PUWER).  CET were fined £20,000 (plus costs of £30,000) under Section 2 of the Health & Safety at Work etc Act 1974.

A second, recent, incident, were the operator suffered a broken shoulder and two broken arms in similar circumstances only serves to underline the seriousness of ignoring the PUWER requirements.

Many AGS Members will already have received a letter from the HSE clarifying the legal responsibilities of employers to safe guard their employees.

Legal Requirements

Under current UK legislation employers’ legal duties include the following:

  • To ensure, so far as is reasonably practicable, the health & safety of their employees.
  • To undertake a suitable & sufficient assessment of the risks to health & safety to which their employees, as well as other people, are exposed arising from their undertaking or work.  The significant outcomes of the assessment will normally have to be recorded.
  • To provide effective measures to prevent access to any dangerous part of machinery.
  • To ensure that, where appropriate, work equipment is fitted with one or more readily accessible controls to bring the machine to a complete stop where necessary for health & safety reasons (an emergency stop).
  • To ensure that, apart from where necessary, no control for work equipment is positioned where it would cause a risk to the health & safety of the operator.

Common Failures

Recent investigation by HSE has shown that people may be being placed at risk due to one or more of the following reasons:

  • A risk assessment has not been done & acted upon.
  • A risk assessment has been done but is neither suitable & sufficient in that it does not correctly identify the measures that could reasonably be taken to eliminate or reduce the risks identified.
  • Access to the dangerous rotating parts of the drilling machinery is not effectively prevented in line with the hierarchy of protective measures given in the Provision & Use of Work Equipment Regulations 1998 (PUWER) & backed up in the BDA guidance.
  • Insufficient or inadequate emergency stops are provided.
  • The operator position places them in close proximity to the rotating part of machinery.
  • The nature of the work undertaken requires close approach to a rotating part of machinery.
  • Operators are not adequately trained or supervised.

Risk Assessment

The purpose of a risk assessment is for an employer to identify the risks his employees, & others affected by his work, may be exposed to.  Once this is done the employer should identify the measures that need to be taken to deal with these risks.

The primary aim should always be to completely eliminate any risk identified e.g. by effective guarding; where this is not practicable the risk must be reduced as much as possible by safe systems of work & the provision of information, instruction & training.

HSE has found that drilling equipment frequently requires close approach to the rotating drill string whether to operate controls, to take samples, backfill or for other reasons.  This obviously increases the risk of people becoming entangled if access to the dangerous part of machinery is not effectively prevented.  Any risk assessment needs to recognise the implications of this risk & ensure that the protective measures chosen offer the highest practicable level of protection.  Large piling rigs are covered by separate guidance produced by the Federation of Piling Specialists in liaison with HSE taking into account the different nature of the risks.

Levels of Protection

PUWER lays out a clear hierarchy of protective measures that is further clarified with direct reference to the drilling industry in the BDA guidance*.  In simple terms the hierarchy for preventing access to the rotating parts of a drilling rig is as follows:

  • A fixed guard that requires physically unbolting.
  • A moveable guard with an interlock cutting rotational power when opened.
  • An adjustable guard (i.e. a fixed or moveable guard with adjustable parts or whole), the adjustable part must be interlocked. These are commonly described as “telescopic”.
  • A caged working area that is interlocked thus preventing risk from rotation when anyone is in the area.
  • Trip wires or bars.
  • Proximity sensors or light beams.
  • Training & supervision.
  • Appropriate clothing with no loose attachments.

The last two points are not “stand-alone” measures but should be provided in all cases.  

Where access to the rotating drill string is to be prevented by a guard it should extend from 0.5 metres above ground level in all cases to 2 metres above ground level or 2 metres above the operator position if elevated.  The rotating drill string, even at relatively low speeds, is an extremely dangerous part of machinery.  The law demands that the highest practicable level of protection should be supplied to prevent access to the dangerous part.  As the BDA guidance quite correctly states in the “protective devices selection” section the actual decision must be made impartially & with safety, not time or cost, as the overriding concern.

In HSE’s opinion, given the practical operational difficulties a fully fixed guard would give, the best practicable solution in the majority of cases will be some form of moveable, interlocked guard.

It should be remembered that the rotating drill string is always to be considered a dangerous part of machinery from which people require the highest practicable means of protection.  This will not always be the most convenient or cheapest option available.

Where manufacturers are no longer trading, or effective guards are not yet available, bespoke guarding options can be retrofitted easily in most cases.

Trip Wires, Stop Bars & Light Beams

Trip wires & stop bars are included in the hierarchy but they are clearly a lower level of protection than a physical guard be it interlocked or fixed.  In order to activate a trip wire or stop bar the person is usually already entangled given the proximity of the device to the drill; plus due to the “wind-down” time further injury is likely once the device is activated.

PUWER requires access to be prevented – trip wire, stop bar or light beam type fixtures positioned in close proximity to the drill string will not usually prevent access to it.  They may reduce the level of injury once a person is entangled but they do not prevent the accident occurring.

Only where a physical guard which effectively prevented access was evidently impracticable would HSE consider a trip wire, light beam, pressure pad or stop bar arrangement a realistic option; further additional measures may also be needed to lower the risk to an acceptable level, for example, relocating operator positions, the fitting of devices to remove spoil automatically preventing repeated activation, a strict regime of maintenance & testing & close supervision.

Emergency Stops

At least one emergency stop should be fitted to each rig, one being next to the operator position.  Such stops must be separate from the usual off switch & require manual re-set so that they cannot fail to danger once activated.  They should be so designed as to bring the part of the operation causing the danger to a complete halt in the shortest achievable amount of time.

Other Considerations

Whilst the risk of injury arising from entanglement is a major risk in operating drilling rigs it is not the only area of concern for the industry.

Risk assessments should also address other associated risks to safety & health.  For example, risks from overhead power lines, underground services, vehicle movements, noise, falling objects, manual handling, soil contamination, the availability of proper welfare facilities to name but a few.


The entanglement risks faced by those operating, or working in close proximity to, drilling rigs are well known.  The legal requirements to protect people are similarly well known & the guidance clear.

The key factor in protecting people from these dangerous machines is a realistically robust risk assessment & the provision of a truly effective means of preventing access to the dangerous part.

HSE will expect to see the highest practicable level of protection in place with full justification for measures from further down the hierarchy where they are found.

We hope that the above guidance is clear enough to leave you in no doubt about the level of protection required.  If HSE has to investigate any further accidents of this kind we will take into account the additional guidance in this annex & letter we have provided to you/your Company in deciding what enforcement action may be appropriate.



*  “Guidance Notes for the Protection of Persons from Rotating Parts & Ejected or Falling Material Involved in the Drilling Process” can be supplied by the. British Drilling Association (BDA)  Tel: 01327 264 62