Lockout/Tagout

The first step is to prepare before shutting down the device.

Don't underestimate this step, it involves a lot of content. An important step is to communicate with those who may be affected. Why is this step important? You can watch the video below.

For some companies, production is a production line and equipment is not separated from other equipment. If only energy isolation is carried out for equipment that needs to be cleaned or repaired without notifying the operators of upstream equipment, the materials of upstream equipment may be transported to the equipment that needs to be repaired or cleaned. At this point, the personnel working on the equipment may be in danger (as shown in the figure below). In this situation, energy isolation of upstream equipment is also required. So, the judgment and communication of the affected personnel are very important. Including downstream equipment, if the equipment you are working on has materials transported to downstream equipment, it is also necessary to communicate with the affected personnel downstream. For example, during the cleaning operation of a tank containing chemicals, the downstream pipeline did not receive the chemical material, and some operators forgot to close the discharge valve of the downstream pipeline when completing the operation. When the material tank completes the operation of feeding, the downstream pipeline is also filled with chemical materials, and the discharge valve is not closed, at this time, chemical leakage will occur.

Of course, in addition to notifying the affected personnel, there are also some other preparatory work, such as preparing the tools, locks, etc. required for the operation, and cleaning the work site.

Step two, turn off the device.

Turning off the device here does not mean isolating the energy source. It simply refers to the shutdown of the device, which means stopping the running equipment. Many advanced devices nowadays do not have buttons, they only have start and stop buttons on the control panel. After the electrical isolation switch is turned off, the device start button on the operation screen will also display 'off'. After closing the isolation switch again, the device will not start directly, and you need to press the start button again to turn it on. Some old devices have buttons that, if not turned off or the switch is not turned off to isolate the energy source, may cause the device to start directly when re turned on or connected to the energy source, which could pose a danger. For example, some simple mixing equipment or manual tools in the laboratory. In addition, some devices have heating devices, such as thermal oil heating devices, which cannot be turned off directly. They need to be cooled down to a certain degree before shutting down, otherwise it will cause equipment damage. So, the second step of shutting down the device should be done according to the correct device shutdown process, and cannot simply turn on the power or press the emergency stop button.

Step three, isolate the energy.

Find the energy isolation device and cut off the energy. Many companies will develop LOTO SOPs or operating instructions specifically for each device, identifying potential hazards and energy isolation points that may exist in the equipment, and even displaying the specific locations of isolation points in a visual manner for operators to easily locate. At the isolation point, labels should also be properly labeled to facilitate employees' search and reduce the risk of mistakes. For example, the label number on the isolation switch of each motor matches the motor number. It should be noted that emergency stop devices, button switches, etc. should not be used as energy isolation devices in principle. Generally, isolation switches are switches with visible breakpoints that can physically isolate energy.

Step four, lock and tag.

Lock and tag the energy isolation device. Nowadays, many power isolation switches have lock holes that can be directly locked with a lock. But there are still many energy isolation devices, such as compressed air ball valve switches, gate valve switches, etc., that do not have lockholes to lock, which requires the use of some locks to fix and lock the switches. There are many specific lock introductions online, such as Bedi, Masters, etc. You can find them online, so I won't go into detail here. When locking, remember to attach the tag and fill in the contact information, so that if the locking time is long and other departments urgently need to restore use, they can contact to unlock, avoiding the risk of forced unlocking in unknown situations. It should be mentioned here that after locking, the key must be carried by the operator themselves and cannot be handed over to others or placed in isolation points. The so-called 'one's own life should be controlled by oneself'. Refer to the following video:

Step five, release or control residual energy.

For some assignments, isolating hazardous energy sources alone cannot completely eliminate risks. The equipment may still have residual hazardous energy sources, such as high temperatures, pipeline pressure, or harmful chemicals inside the pipeline. If cleaning or maintenance operations may come into contact with these residual hazardous energy sources without prior release or control, they may pose a hazard during the operation process. For example, when dismantling pipelines, chemicals or pressurized materials may spray out and injure people. For example, in a hydraulic device located at a high place, if the hydraulic pipe ruptures, the device will lower and injure the personnel working below. The following video may be more convenient for everyone to understand this point.

Step six, verify the effectiveness of energy isolation.

This step is the most important and often overlooked by many people. Sometimes the homework site is quite complex, with many isolation points, and people's minds can also get confused. At this time, if the isolation switch is locked incorrectly, it is also possible. If the switch is locked incorrectly and someone accidentally starts the device, the operator may be in danger. So, before starting the formal assignment, it is important to verify if the lock is correct. The most common way is to press the device start button again to see if the device can be started. For pipelines, some can determine whether the pipeline isolation is complete by opening the emptying bottom valve to see if there is still material flowing out. Of course, pipeline isolation in the chemical industry is often complex, requiring blind disconnection, even double isolation and emptying, which will not be elaborated here. The following video reflects the importance of verifying isolation. Here, it should be noted that for some simple control switch devices, remember to turn the switch to the off state after verification to prevent the device from suddenly starting up and causing danger when the power is turned on, such as some mixing equipment.

The seventh step is to officially start the homework.

Step eight, restore the protective device of the equipment.

Some tasks require the removal of equipment protective covers or protective devices. After the task is completed, the corresponding protective devices must be restored before the equipment can be started to resume production. In addition, it is necessary to clean up the tools in the workplace and not leave them inside the equipment, otherwise it may cause danger or damage to the equipment. For example, if a maintenance personnel misses a wrench inside the equipment, it may be thrown out when the rotating part of the equipment is opened, causing injury to surrounding personnel. Here, it is also necessary to count the number of people involved. Many large equipment may have many people involved in the operation at once, and it may be difficult to detect if one or two people are missing. For example, when working in a large reactor, if someone doesn't come out before starting the equipment, it can lead to a big problem. So why do we require every worker to lock it? Once someone hasn't come out yet, the device won't turn on.

Step 9, unlock. When unlocking, be careful that if you haven't completed your work, don't let others unlock it for you. Unlock your own lock yourself. Why do you say that? You can watch the video below.