Quick answer
Where work could expose people to dangerous movement or energy, follow a machine-specific isolation procedure carried out by authorised, competent people. Identify all energy sources, prevent unexpected reconnection, control stored energy and verify the safe state before access. Plan the handback before returning the equipment to service.
A stopped machine may still contain dangerous energy
A normal stop control does not necessarily prevent restart or release pressure, heat or energy held in raised parts. Cleaning and blockage clearance can put people close to those hazards.
HSE’s maintenance guidance covers safe isolation, locking off where restart is possible and control of stored energy. This is a planning guide for arranging the work; the operating method must come from the equipment-specific procedure and suitable competence.
1. Define the task and who is authorised
Identify exactly what will be cleaned, opened, adjusted or maintained, who may enter the danger area and which connected equipment may affect it. Use the manufacturer’s instructions and the site’s safe system.
Agree the people responsible for isolation, verification, work control and handback. Include contractors and other operators so nobody assumes that another team has made the equipment safe. Complex or high-risk work may need specialist planning and a formal permit system.
2. Identify the energy and the protection needed
| Issue | What must be resolved before access |
|---|---|
| Energy sources | Which electrical, mechanical, pressure, fluid, gas or other sources can affect the task? |
| Stored energy | Could pressure, movement, gravity or hot components remain dangerous after stopping? |
| Unexpected restart | How will the agreed system prevent someone reconnecting or starting the equipment? |
| Verification | Who will establish that the safe state has been achieved, using the approved method? |
| Work boundaries | Who and what are protected, and how will changes or additional people be controlled? |
A tag communicates information; it is not by itself a physical means of preventing reconnection. Use the appropriate isolation, locking and other controls specified for the task. Verification methods must suit the energy and equipment.
For NI electrical work, HSENI requires competence and appropriate isolation and testing. This article does not provide electrical testing, wiring or repair instructions.
Worked example: a conveyor blockage
Hypothetical example. A conveyor stops with material trapped near moving parts. A worker is tempted to reach in because the belt is stationary. The agreed response is to keep clear and contact the authorised person.
The assessment considers the conveyor and any linked equipment, the possibility of restart and energy released when the obstruction moves. The competent person applies and verifies the equipment-specific controls before access. A stop button or an informal assurance that “nobody will start it” is insufficient planning.
3. Control the work and safe handback
HSENI’s maintenance guidance emphasises following the agreed system and making final checks before restarting. Confirm that work is complete, safeguards are restored, people and tools are accounted for and the area is suitable for operation.
Release isolation controls only through the agreed authorised procedure, including any handover between people or shifts. Explain the equipment’s status to affected users. If the work changes or an unexpected condition appears, stop and reassess rather than extending the original arrangement by assumption.
- Cleaning treated as outside the safe system. Assess the actual access and energy.
- Only the obvious power source considered. Include connected and stored energy.
- An unclear team handover. Define who controls the protection and release.
- Restart before safeguards and people are checked. Complete the handback process.
Next steps
- Define the task, affected equipment and authorised roles.
- Use the equipment-specific procedure to identify and control all relevant energy.
- Have the safe state verified before access.
- Maintain control through the work and complete an authorised handback.
Read HSE’s safe-maintenance guidance — Use it to check planning and competence before developing or reviewing the machine-specific procedure.