If a machine can start or move and endanger the safety of any worker, it must be taken to a zero-energy state and locked out. Simple to say but harder to carry out. Let’s step through a new machine installation and map how to get there.
Historically it often has gone like this: a new machine comes in and compressed air and electricity are hooked up. The plumber runs piping from the most convenient place to the machine hook up. A ball valve with a lockable handle is plumbed in, or maybe the machine came with a lock-out valve. The electrician wires to the main panel of the machine relying on the disconnect switch/handle built into the door of the cabinet to serve as a lock-out point. Then HR sends the safety resource person out to document a lock-out procedure. The operator is left to walk around to the electrical cabinet, usually at the back of the machine, to lock-out the electrical, and then walk the length of the machine to lock-out the air. All while being responsible for the lost production time involved in all that walking and at the same time legally obligated to do the lock-out. And who has determined that the machine is now at zero energy?
Let’s look at a map towards ‘productive lock-out’. Production, maintenance and HR meet before the machine comes in to plan the lock-out procedure. Maintenance determines what will be required to achieve zero energy. All forms of energy must be taken into consideration. Air and electrical power are obvious. Gravity, hydraulic accumulators, air tanks on the machine, and capacitors in variable speed drives are not obvious. Then all the lock-out points are determined on a machine schematic. The production staff determine where the lock-out should be located to minimize downtime. Wherever possible the lock-out points should be located right at the operator station. Easy to do during installation. Not so easy to retrofit. Maintenance or the project staff then take that information and include it in the installation plan. It is the law that a machine specific written procedure be given to the employees involved in locking out the machine and that each employ be specifically trained to perform the steps.
Some things to watch out for:
The lock-out switch supplied by the equipment manufacturer is always inside the panel, so there is still live electricity in the panel when the switch is closed and locked out. If the switch is on the electrical cabinet door, it is possible to open the door, and turn the power back on with the lock still in place.
It is best to turn off and lock out power before it gets to the equipment electrical panel. An unfused lockable disconnect switch at the operator station will accomplish this. This takes away any concern for arc flash as there is no power in the panel when the machine is locked out.
Beware of lock-out valves for compressed air that are located inside fencing or guarding. You must lock-out before you go in, which you cannot do if the lockout point is located inside the guard.
If there is a ‘control reliable’ safety system, such as interlocking or light curtains it may be used as an alternative to full lockout for minor servicing. (See CSA Z460-05, Control of Hazardous Energy - Lockout and Other Methods) These systems trigger a Pre-Start Health and Safety Review, so ask your safety engineer doing the PSR about this.
Be aware that every person (including a contractor) that is potentially in harms way from a machine starting unexpectedly must have their own personal lock on all lockout points to ensure their safety. One lock does not do for multiple people.
LOTO is the short form name for this exercise but it leaves out the ‘Verify’ function. Every person putting their lock on must verify that the machine is depowered. So, lets change the short form to LOTOV.
Lastly, if the person in charge of plant maintenance must sign all lock-out procedures, then they will be sure that any technical changes to the machine or installation will automatically trigger a revision of the lock-out procedure. This feed back loop is critical in keeping the lock-out procedures accurate and up to date.
Time and planning invested in Lock-out will save a great deal of production time over the life of the machine and help ensure the safety of all employees. And your operators will thank you for it.
For more information and training EMC offers please contact Amy Edwards at firstname.lastname@example.org