February 4, 2019
Guarding is a legal requirement in the UK; HSE guidance and PUWER 1998 (as amended) assists towards compliance and highlights the requirements to prevent people from entering a ‘danger zone’. ‘Danger zone’ means any zone in or around machinery in which a person is exposed to a risk to health or safety from contact with a dangerous part of machinery or a rotating stock-bar.
Employers must ensure measures are in place to prevent employees from being exposed to dangerous parts of machinery. A ‘dangerous part’ of machinery is determined by risk assessment; if the hazard could present a reasonably foreseeable risk to a person, the part of the machinery generating that hazard is a ‘dangerous part’.
The hazard to be overcome is mechanical contact or being caught by the dangerous moving part. Mechanical contact is divided into the categories including:
The main regulation considering this is PUWER 1998 Regulation 11 Dangerous Parts of machinery states:
(1) Every employer shall ensure that measures are taken in accordance with paragraph (2) which are effective-
(2) The measures required by paragraph (1) shall consist of –
(3) All guards and protection devices provided under sub-paragraphs (a) or (b) of paragraph (2) shall –
Looking specifically at rotary drilling rigs we can apply a hierarchy of control measures so that compliance is met.
1 Provide a fixed guard.
A fixed guard is a physical barrier that prevents a person from coming into contact with dangerous moving parts. The guard may be shaped to fit the machine quite closely (enclosing guard), or it may be more like a fence around the machine (perimeter guard). It may have openings in it, but these must be designed in such a way that it is not possible to reach in and contact dangerous parts (distance guard). The basic principles are;
2 Moveable Interlocked Guards.
An interlocked guard is designed to be removed or opened as a normal part of routine machine operation. When the guard is removed, a safety interlock system prevents machine operation. The basic principles are;
3 Pressure Sensitive Equipment
Pressure Sensitive equipment is a range of protective devices that do not put a physical barrier between the operator and the dangerous part of machinery. Instead, some form of sensor is used to detect the presence of the operator and stops the machine. The use of sensitive protective equipment is intended to minimise the severity of an injury and is often used as an additional control measure for example in combination with an interlocked access gate. Examples of sensitive protective equipment:
To explain the relationship between regulation 11 and the hierarchy:
Advanced protective devices -are available but are not in widespread use. They are defined in the Machinery Directive (2006/42/EC) in that they must stop moving parts of machine before a person can touch them and moving parts can only be operated in ROM while they are within the operator’s reach. Protective devices are still a developing technology with radar, light, infrared, ultrasonic, proximity/RIFD being investigated. (Note that systems which depend on the person carrying a transponder do not provide collective protection). Current UK research suggests that some proximity devices can be effective at preventing someone reaching into or entering the protected zone, whilst coping with small pieces of spoil and water spray. Inspectors may find drilling rigs fitted with proximity devices undergoing field trials in the UK and Construction Sector Safety Unit would like to receive any observations. Once the technology is proven in practice these systems may move up the hierarchy.
It should be noted the use of Pressure Sensitive Equipment instead of fixed or moveable interlocked guards is the lowest in the hierarchy and must be robustly justified in a written risk assessment with evidence of why guards are not practicable. Machines supplied from 2014 should only be fitted with Sensitive Protection Equipment as a secondary or additional protective device.
The guard must be positioned not more that 500mm above the drilling table or the ground, if it is higher than this the drill string must be guarded, potentially using casing, however the casing itself would need to be guarded should it rotate. Please note casing clamps should be provided in such a condition that prevention of crushing or entrapment (dangerous moving part) is controlled.
It must extend to a minimum of 1600mm above the ground and / or working platform, attention should be paid the Operators standing on working platforms the guard should extent to such a height that the rotating part cannot be touched from the working position.
Application: When the guard is open;
‘Hold to run’ controls require the operator to hold the control at all times to operate the machine. Releasing the control for whatever reason will stop the machine from operating and within half of a revolution.
To return to full rotation or feed the guard must be closed and a separate positive action from the operator must be carried out.
The guarding should at all times fail to safe. If the guarding is not working correctly the rig must be rendered inoperable with immediate effect.
Daily checks to ensure compliance;
NONCOMPLIANCE WITH ANY OF THESE CHECKS THEN DRILLING MUST NOT COMMENCE.
Author: Jon Christie, Chair of Safety Committee, British Drilling Association
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