7 steps to gear up for plant shutdown -List of Safety Precautions for Shutdown Activities of Chemical Plants

7 steps to gear up for plant shutdown

Written by  Michelle Morra 31 August 2011

Preparing for your next plant maintenance should start with a solid lockout program to keep workers safe from the hazards of energized machinery. Safety experts offer best practices for safe shutdown procedures.

You would never clean a meat slicer without first unplugging it and making it impossible for anyone to plug it back in. Safety in this case is simple: place the plug in a lockout device and hold onto the key until the job is done and you are safe from the machine’s moving parts.

The risk is similar but a hundredfold in a manufacturing plant or other facility with multiple machines and equipment. Shutting down the entire plant for cleaning, service or maintenance requires that every part with the potential to move be rendered completely inanimate.

Many occupational injuries and fatalities are the result of power sources being inadvertently turned on, or valves opened mistakenly before the work is completed. That’s why it’s important to not only lock out all energy sources, but keep them locked out until the work is completed.

Energy control is a big job that must be done meticulously, with no room for error. Probably the biggest challenge, says Jamie Button of Brady Canada, is a lack of resources.

“Companies that are trying to follow ‘lean’ or ‘5s continuous improvement’ have got things so pared down,” he says, “that often people tasked with developing a lockout/tagout program have many other things in their job description. They also have to be experts in being engineers or ‘continuous improvement’ people.”

On the brighter side, he has observed that since the Ontario Ministry of Labour stepped up its inspections over the past five years, and since CSA Standard Z460-05 Control of Hazardous Energy – Lockout and other Methods came into effect, he has seen far more requests for lockout products and services than before.

Every plant should have written procedures for a safe plant shutdown. According to the Industrial Accident Prevention Association (IAPA), the procedure should state that: supervisors must be notified of lockouts in their areas; all lockouts must be authorized by a work permit; lockout stays in effect if work is not completed at the end of the shift; and completed work must be reported to the person in charge of signing off the work permit.

As for the lockout process itself, every machine being cleaned, maintained, adjusted or repaired must have its own written lockout procedure.

“I’ve seen some do generic shutdown procedures, and you could see that it was for another plant,” Button says. “It’s important to indicate that it’s for this machine, for this plant. Inspectors want to see you be specific.”

He says that if machines have very few or just one energy source, (like pulling out a plug), it might be enough to put a lock or tag on it. But a generic procedure won’t do if you have multiple sources of energy feeding it. “If you’ve got hydraulic, pneumatic, gravity or electricity or any combination of those things, obviously you’ve got to get into multiple steps to isolate the energy,” Button says.

Every machine, device or process needs its own written lockout procedure that states who will perform the lockout, who is responsible for ensuring it is done right, which energy sources need to be controlled, where to find control panels, valves and other components, and the steps for removing the lockout.

While every machine’s lockout procedure is different, here are the essential steps:

Conduct a risk assessment. Identify all energy sources connected with the work. The machine’s written lockout procedure must indicate all hazards.

Turn it off. Unplug, switch off and disable the equipment and redirect, or stop all energy. Much more than a flick of a switch, though, powering down means releasing all stored energy.

Some machines have several sources of energy. You can’t always see them, but they lurk in hidden places such as springs, pistons, air surge tanks and loose machine parts and have been known to injure or kill workers who thought the machine was disabled. For example, gravity can cause the raised arm of a press to drop, even if the machine’s hydraulic and electric power are locked out. “Stored energy” could be anything with potential to cause the machine to spontaneously or unexpectedly move.

All potential energy must be relieved, disconnected and restrained. A “competent person” — one who has the knowledge, training and experience to safely perform the task and is familiar with applicable hazards and safety regulations — must stop all energy flows. This step might require tracking wires, lines, and piping in and out of the equipment to identify all energy sources.

Lockout: Keep it off. Apply restraint devices to prevent the system from starting up while you work on it. Each person working on the equipment must padlock the disconnect switch in the off position, remove the key and hold onto it. The person in charge, or who is doing the work, should be the first to install a lock and the last to remove it.

Tagout. Each worker who is working on the machine needs his or her own tag. Tagout is a way of communicating the danger to anyone in the vicinity — in plain language: Do not start. Do not close. Do not energize. Do not operate.

The tag indicates who locked out the machine, directs people not to start or operate the machine, and notes when the lockout procedure was applied. Some companies use colour-coding, where each department uses a different colour. Barricade tape or floor stands are also effective visuals to convey the message that an area is off-limits. Some even put the employee’s picture on the tag.

“If you have a face on there,” Button says, “you see the person who’s doing the work. And if you see that face and you know who it is, maybe even subconsciously you’ll use a little more care.”

Test. Before starting any cleaning, maintenance or service, check that the equipment has been locked or tagged out, isolated and de-energized. Also make sure the main disconnect switch cannot be moved to the “on” position. Try starting the machine using the normal operation controls and switches to make sure that the power is off. The machine’s lockout procedure should spell out exactly how to test the lockout.

Do the maintenance, cleaning or service work. You may start work on the machine or its parts only when you know there is zero chance that any part of the machine or equipment will move!

Safely resume operations. Before turning the machines back on, alert staff that the lock and/or locks will be removed. Make sure the operational controls are in the “off” position so that the main disconnect switching is done under “no load”. There should be no tools or other foreign materials in the machine.

No lock should be removed until the work is done and the work is completed and the work permit signed off. The person supervising the lockout should be the last to remove his or her lock.

List of Safety Precautions for Shutdown Activities of Chemical Plants

There are two kinds of chemical plant shut down, i.e. planned shutdown and emergency or unplanned shutdown. An example of planned shutdown is as preparation for Turn Around or yearly preventive maintenance programs. Emergency plant shutdown can be triggered by many factors, such like electric power failure, machinery failure, instrumentation trouble and many more.
In both shutdown cases, there are safety precautions for shutdown activities of chemical plants that need to be taken into account. Such safety precautions are required to prevent potential hazards that commonly appear during plant shut down.
In fact, many people may underestimate chemical plant safety in shutdown condition. Of course there may no pumps running, no reactions occur or production process. But various potential hazards such as over pressure, fire and explosion still exist, which could present real danger to the plant and people inside it.
This article is aims to provide safety precautions for shutdown activities of chemical plants. The safety precautions inside this article will not cover all the potential hazards because each plant has different potential hazards. However, they may represent the most common potential hazards during plant shutdown.

1. Release pressure that may be trapped between two closed valves or closed process equipment loops. If liquid trapped inside is decomposing and releasing gas, such as hydrogen peroxide, the condition will be worst.
2. Replace flammable gas inside vessel or piping line to below its Lower Explosive Limit (LEL) with inert gas, for instance nitrogen if hot work is planned to be done surround that area.
3. During normal operation there may be a leak through steam valve. Insert a blind plate to stop process heating by steam, otherwise pressure inside will build up and may create over pressure or over heating condition.
4. Always measure oxygen concentration inside tank or reactor at the safe level, where a job will be conducted.
5. Flammable gas concentration may zero in tank or column, but beware of nitrogen hazard, since nitrogen could make oxygen level less than safer concentration.
6. Maintain nitrogen blanket for tank containing flammable liquid during plant shut down. Flammable vapor is still released.
7. When pressure indication just relies on pressure gauge consider error indication. Seek another one for comparison.
8. Do not just rely on pressure gauge indication to make sure zero pressure. Open all available drain or vent valves to release the remaining pressure. Beware of pressure that trapped in a dead zone.
9. Bring any high temperature process to ambient. It is not only saving energy but also eliminate one hazard source. Except there is a strong requirement keeping that high temperature.
10. During plant shut down period, it is usually performed many jobs in the same time. Be careful not to use same hoses or transferring pump to avoid unintended reaction. Consider material compatibility. Read the MSDS to find out material compatibility.
11. There will be much flammable or combustible material spread around the plant site. Do not dispose used absorbent materials that still contain flammable liquid into trash bin.
12. Utilization of temporary lines or hoses may increase in shutdown period. Dispose damaged hoses and only use good hoses with the right specifications.
13. Several equipments or pipelines are designed to be used only in shutdown time. Be careful, because some part of the equipments or pipes may have been corroded and would not be able to hold certain pressure rating.
14. Used drums are usually used during plant shutdown in order to recover lubrication oils, chemicals or catalysts. Use only used drums that are originally used for those chemicals or ones that have been washed and cleaned up.
15. In yearly preventive maintenance period, there are not only permanent workers involved in plant shutdown activities but there will be contractor workers and temporary workers. Educate them adequately about all the potential hazards that may exist in the area where they work.
16. Temporary electric connections are commonly used for driving portable pumps or exhaust blowers in shutdown time. Put extra care to avoid electric spark generation because many flammable materials exposures.
17. Chemical splash and spill hazards will more likely occur during maintenance works.

The above checking points do not represent all the safety precautions for shutdown activities of chemical plants. Complete the above list based on your actual plant conditions. It had better to include them in safety inspection checklists during plant shutdown.