Knowledge · Fundamentals
Energy isolation in the LOTOTO process
A single machine often has several energy sources, and each is isolated differently, at a different point and sometimes by a different trade. This page explains which energies need to be considered, what an isolation point is and why it is useful to confirm each energy separately.
Equipment is secured only once all of its energy sources are isolated.
What is energy isolation?
Short answerIt is disconnecting equipment from an energy source at an isolation point so that energy cannot reach it, and releasing or securing any energy that remains inside.
Isolation is the core of the whole LOTOTO procedure. The lock and tag protect it from being undone; verification (Tryout) confirms that it is effective. If isolation is done at the wrong point or only partially, neither the lock nor the tag will protect the worker.
Isolation deals with the energy source, not with machine controls. Pressing a stop button, turning a selector switch or switching off through the control system stops the equipment, but does not separate it from its energy. A control circuit can fail, be bypassed or be activated by mistake.
Which types of hazardous energy are isolated?
Short answerBesides electrical energy, mainly mechanical, gravitational, hydraulic, pneumatic, thermal and chemical energy, as well as pressurised media in pipework.
| Type of energy | Example sources | Example isolation and release |
|---|---|---|
| Electrical (LV, HV) | drive supplies, control circuits, capacitors | disconnector, circuit breaker, racking out, discharging, earthing as per the rules |
| Mechanical | rotating parts, flywheels, compressed springs, belts | waiting for run-down, mechanical block, releasing springs |
| Gravitational | raised parts, loads, material in hoppers and silos | lowering to the bottom position, propping, securing, emptying |
| Hydraulic | cylinders, accumulators, pressure lines | closing a valve, depressurising, checking the gauge |
| Pneumatic | compressed-air lines, cylinders, receivers | closing and venting, lockable valve |
| Thermal | hot surfaces, steam, hot material | shutting off the supply, cooling down, draining |
| Chemical and pressurised media | process substances, gases, steam, water in pipes | closing and blanking, draining, flushing |
This overview is illustrative only. The actual energy sources, isolation points and methods of securing them are set by the procedure for each piece of equipment.
When identifying sources, the greatest risk lies in energy that is not obvious at first glance: a second supply, a backup source, a pressure accumulator or material that can slide down in a hopper. That is why every piece of equipment should be handled according to a procedure prepared in advance, not on an estimate made on the spot.
What is an isolation point?
Short answerAn isolation point is the specific place where an energy source is separated by an isolating device and where the lock and tag are applied – for example a disconnector in a switchboard or a valve on a pipe.
An energy-isolating device physically separates the energy: a disconnector with a visible break, a manually operated circuit breaker, a shut-off valve, a blank or a mechanical block. Push buttons, selector switches and other control-circuit devices are not regarded as energy-isolating devices.
An isolation point must be clearly labelled and assigned to the equipment. If a switchboard has dozens of outgoing feeders and their labels do not match reality, even a careful worker can lock the wrong one. The quality of labelling on site is therefore as important as the quality of the documentation.
The isolation procedure for a specific machine – which isolation points, in what order and how to verify the result – is a natural candidate for a digital work instruction available to the worker right at the equipment.
Why record each energy separately?
Short answerBecause different energies are often isolated by different people at different times. The equipment is secured only when all of its energy sources have been isolated.
An electrician disconnects the electrical supply in the switchboard, a fitter depressurises the hydraulics at the power unit and another worker closes the compressed-air supply. A single signature saying “equipment secured” merges these actions and loses the information about who did what.
In digital lockout tracking, each type of energy is therefore handled separately. Each isolating person confirms their own energy and enters the number of their lock. The system shows the overall “locked” status only once all required energies have been confirmed. A worker can also be permitted to secure only the types of energy they are assigned to – for example, an electrician only electrical energy.
ReadRoles and authorisationsHow do you recognise a partially completed process?
Short answerBy tracking status energy by energy. Instead of a general “the equipment is being secured”, you can see which energies have been confirmed and which action is still outstanding.
Partially secured equipment is more dangerous than it looks. It appears shut down and some locks are in place, yet one energy source may still be connected. If that state is not clearly visible, someone may start work too early.
The same principle applies to unlocking. Each isolating person confirms the release of their own energy, so equipment that is being returned to service is visible too.
Why is a good equipment register the foundation?
Short answerBecause isolation records are only as good as the data they rely on. A faulty equipment register leads to a faulty list of energies.
The equipment register holds the equipment code used by the plant, a description, the assigned types of energy and photographs. When introducing a digital process, these data must be checked, as must the links between equipment and isolation points. This often reveals that labels on site and in the documentation do not match.
A list of energy types for a machine does not, however, replace the procedure for securing them. It says what needs to be isolated, not how or where. That is defined by the approved work procedure and the competence of the worker.
Equipment and energies typical of individual sectors are covered in our industries overview.
Do digital records replace physical isolation?
Short answerNo. Digital records capture workers’ confirmations of completed actions. Isolation, lockout, tagout and verification must always be carried out physically at the equipment.
The “locked” status in the application is a recorded status based on workers’ confirmations, not a measurement of the equipment’s state. Verification of the isolation – Tryout – remains a separate task on site; how it is recorded is something we design according to the rules of each plant. What digital LOTOTO offers and where its limits lie is described on the digital LOTOTO page.
Frequently asked questions
Is it enough to switch off the machine’s main switch?
Not always. The main switch disconnects the electrical supply if it is an isolating device, but it does not deal with pressure, gravitational energy, momentum or other sources. The procedure for the specific equipment is what counts.
Can one isolation point secure several machines?
Yes – a shared compressed-air supply, for example. That is why the register should capture the links between equipment and isolation points, and it should be clear who is working on them.
Who decides which energies a machine has?
The plant, usually when preparing the procedure for the equipment and assessing its risks. A digital system takes over this data; it does not create it.
Next step
How do you record energy isolation today?
We will look at your equipment register, energy sources and isolation procedures with you and show how they could be managed energy by energy in a digital process.