Home Links


This guidance has been produced by a working group of QNJAC which comprises of industry experts from varied backgrounds, the Trade Union and HSE. 

This document does not consider the implications for isolation and lock-off procedures posed by systems which incorporate trapped key or captive key elements.  An interlock system should not normally be used as a means of isolation, unless it has been specifically designed for the purpose, such as some trapped key systems.  For this reason, care is needed, and the advice of a competent person should be sought to ensure your isolation and lock-off procedure for such systems is fit for purpose.  Further guidance is available in PD 5304:2014 “Guidance on safe use of machinery” available from BSI.

The purpose of this document is to provide a structured framework to enable organisations to carry out self-audits of isolation procedures to prove their effectiveness as well as identifying weaknesses in the system that could lead to serious injury or loss of life.  It can be used and adapted by any organisation operating machinery that needs to be isolated from sources of power, typically for maintenance purposes.

Serious accidents can and do occur.  There have been numerous serious accidents, many resulting in fatal injury, where machinery has not been isolated from all sources of energy and has started either intentionally or unintentionally.  Systems for achieving effective isolation consist of many elements including;

  •       Provision of suitable means to isolate equipment and test the effectiveness of isolation that is available and clearly and unambiguously labelled
  •      Maintenance of equipment 
  •      Training and competence of individuals
  •      On the job assessment of knowledge
  •      Supervision and refresher training
  •       Audit and review of effectiveness of control measures

All elements combine to form a safe system of work.  A failure of one or more critical elements may lead to a complete failure of an isolation system and the consequences can easily be fatal. Therefore, it is essential to consider all of the individual elements that make up the system and routinely monitor their effectiveness.  To help achieve that, this guidance provides a useful set of questions to ask in order to check the integrity of systems provided to ensure safe isolation including consideration of the people who work within those systems and procedures.  Human error is a significant factor in many accidents involving failure to isolate correctly.  A procedure in itself will not prevent an accident.  Do not ignore the people who are required to make isolations or supervise the work of others that may involve isolating plant.

The findings of the audit can be recorded and used to write an action plan and a record made of the actions taken as a result of the audit.  The question set can never be totally comprehensive in all circumstances, but it represents a good starting point that will be adequate in many situations.



The self-audit is not exclusive to the quarry industry.  The same risks exist across a wide range of industries and the guidance therefore has a use in many industries in the mineral products sector.

The guidance is biased towards isolating electrical power simply because this is the most common source of power for machinery and equipment in the mineral products industry.  However, it is important to consider all sources of energy and include them in the audit process.  The questions in the self-audit do provide prompts to consider all sources of energy.