List of checks for deactivation and isolation: What should be inspected in industrial premises?

List of checks for deactivation and isolation: What should be inspected in industrial premises?
Before equipment maintenance, the most dangerous time window is not the moment of shutdown itself, but the period from “thinking the power has been cut off” to “actually confirming that it has been shut down”. Many accidents occur during this gap – someone thinks the power has been cut off, and someone thinks the residual pressure has been released. As a result, when they take action, the machine suddenly starts. 
A reliable checklist for deactivation and isolation should ensure that all these “beliefs” are transformed into “confirmations”. Below, in the order of operations, we will summarize the items that must be checked before each shutdown and maintenance in industrial facilities. 
I. Preparatory Checks Before Shutting Down
Before starting to shut down anything, there are several things that must be clarified first: 
Is the energy list for the equipment complete? Each piece of equipment has an “Energy Source List”, which records all the energy types involved in this equipment – electricity, gas, liquid, heat, gravitational potential energy. If this equipment has just undergone renovation or a change in process, has this list been updated synchronously? This is the first step and also the most easily overlooked step. During the renovation, a pipeline of compressed air was added, but the file was not updated afterwards. When checking, this was overlooked. 
Who is conducting this maintenance? The list of participants needs to be confirmed. Not only the maintenance workers from our factory, but also the outsourced personnel and those providing cross-departmental support should be included. The more people there are, the more communication gaps there will be. There should be a specific column on the inspection checklist to record the names and job types of all the participants. 
Is the downtime window clearly defined? When does the shutdown start and when is the resumption planned? It should be clearly stated. This is not to urge everyone to rush the work, but to confirm: If the work is not completed by the resumption time, who is responsible for notifying everyone of the delay? Many accidents occur under the condition of “lock not removed after exceeding the time limit” – someone thinks the maintenance is over and resumes power supply without authorization. 
II. Energy Isolation Check – Item-by-item Confirmation
This is the core part of the checklist. The isolation methods for different energy types are different, and the inspection points are also different. 
Electrical isolation
Has the main power switch been turned off? To confirm that the switch handle is indeed in the “OFF” position, one must not merely rely on others’ statements that “it has been pulled”.
Is the device locked with a personal safety lock? Is the key to the lock with you?
Are there residual capacitors? After the large frequency converter and servo system are powered off, there may still be electricity stored in the capacitors. It is necessary to measure the voltage with a multimeter to confirm that it drops below the safe level.
If it is a high-voltage device, has the “disconnect + ground” procedure been carried out? Has the grounding rod been installed?
Mechanical isolation
Does the equipment have energy storage components? Springs, counterweights, balance blocks – these may still release energy even after the equipment is shut down.
Is it necessary to use mechanical baffles or support blocks to fix the moving parts? For example, the slider of a hydraulic press must be fixed with mechanical support, not just relying on hydraulic locks.
Is the gravitational potential energy handled? Suspended loads, lifted platforms – must be lowered to the ground or physically locked.
Pneumatic and hydraulic isolation
Has the main valve of the air source/hydraulic source been closed and locked?
Has the residual pressure in the pipeline been released? To open the pressure relief valve, confirm that the pressure drops to zero. Do not just look at the pressure gauge – the pressure gauge may be faulty, or it may show the pressure of another section of the pipeline.
If there is a Energy reservoir (energy storage device)， has the pressure in theEnergy reservoir been released separately？ This is the most easily overlooked point.
Process medium isolation
Has the pipeline for transporting hazardous chemicals been reliably isolated？ Double isolation (closing valves + installing blind plates) is more reliable than relying solely on valves.
Are there any  signs at the isolation points？ To prevent others from mistakenly opening the valves.
If the medium is toxic or volatile， has it been purged or replaced after isolation?
III. Lockout tagout (LOTO) inspection
After energy isolation is completed， Lockout tagout is the second line of defense. The checklist should include these confirmation items： 
Have all the isolation points been locked? Does the number of locks correspond to the number of participants?
Is each person’s lock only accessible with their own key? (Key principle of security: one key for one lock)
Are the lockout tag information complete？ The labels should include： the name of the person who locked it， the date， contact information， and the operation content.
If it’s a group operation， is there a collective Group Lockout Box used？ The advantage of a collective lock box is that the equipment can only be started when the last person unlocks it – no one can restore it in advance.
IV. Zero-energy verification – the most crucial step
After the isolation and locking are completed， verification must be carried out. This step cannot be omitted and cannot be entrusted to others. 
The verification method is as follows: Try to start the device. Press the start button and observe if the device responds. If the device moves, it indicates that the isolation is not thorough and a recheck is necessary. If the device does not respond, it means the isolation is effective. 
This verification action should be carried out by the person who performed the locking, rather than by the shift supervisor or the safety officer. Because only the person who performed the locking is the one who knows best whether he has locked all the necessary energy sources. 
After the verification is completed, mark the verification time and the name of the verifier on the checklist. This signature carries legal significance. 
V. Inspection during Maintenance Period
After the maintenance began, the work on the inspection checklist was not yet completed. 
Every day before starting work, does anyone check if the locks and tags are in good condition? Have they been knocked off or been removed by someone without permission?
If there is a shift change, does the person handing over and the person taking over jointly confirm the lock status during the handover? Both parties sign on the checklist together, which is much more reliable than just giving a verbal explanation.
If the scope of the maintenance expands (for example, originally planned to repair the electrical system, but later it was discovered that the mechanical part also needed to be worked on), does a re-evaluation of the energy isolation range need to be conducted? The original isolation measures might no longer be sufficient.
VI. Inspection before Resuming Operation
After the maintenance is completed and preparations are made to resume operation, the last part of the checklist comes in handy: 
Have all tools, parts and debris been completely removed from the inside and around the equipment? Once there was an accident where a wrench fell into the transmission mechanism, and the equipment got stuck as soon as it was started, causing a chain of damages.
Have all protective covers and safety doors been restored to their original positions?
Have all personnel evacuated to a safe area? It is necessary to count the number of people, and it cannot be done by simply shouting “The machine is going to start” and then leaving.
Was the lock removed by the person who locked it? It cannot be removed by someone else or “helpfully” removing someone else’s lock.
After removing the lock, was the equipment’s condition finally confirmed to be normal, and then did you notify the power supply department to restore the power?