Why power isolation matters
TT Club’s Laurence Jones draws attention to a little understood danger in cargo handling facilities
The tragic death of a worker in Balboa recently highlights the need to ensure the establishment of, and adherence to, safe and effective workplace isolation procedures. It is understood that this particular incident was the result of a conveyor belt starting while the deceased was carrying out maintenance repairs.
Unfortunately, it appears either adequate isolation procedures were not in place or were not correctly followed.
An isolation procedure is a set of predetermined steps that should be followed to keep plant and its components from being set in motion, or to prevent the release of stored energy, in order to protect the safety of personnel during plant inspection, repair, maintenance or cleaning activities.
Reference to plant in this context covers equipment, machinery, appliances, tools and implements. In a cargo handling facility of course it primarily includes cranes, mobile handling equipment and vehicles, but in the Balboa case it was a conveyor belt. Every year, workers are injured, sometimes fatally, when plant is inadvertently activated or stored energy is released; increased attention to preventative measures can significantly improve the situation.
Isolation procedures at each individual facility will of course vary because of different plant, power sources, hazards and processes. However, every isolation procedure should include the following basic steps in every case:
· Before shutdown the authorised worker must be aware of the type and magnitude of the energy involved, the specific hazards and the means to control it. All affected must be notified of the intended lockout.
· Shutdown should be carried out by the normal stopping procedure.
· Identify all energy sources that may potentially re-activate the plant and place people doing the work at risk. These could include: electricity (mains, solar or generator), fuels, heat, steam, fluids under pressure (such as water, air or hydraulic oil), stored energy, gravity and radiation. Emergency stop buttons, lanyards and similar stop devices on their own will not necessarily achieve isolation. It is extremely dangerous to rely solely on such emergency devices, as they are not designed for frequent use and cannot be locked out in all cases. They may also allow energy to be inadvertently re-activated or for control circuits to remain live. Don’t forget remote control rooms and process computers.
· Isolate the main power switches, circuits, or additional sources of energy, moving them to the off position or otherwise making inoperative. Except in the case of equipment connected via a plug and socket, a competent person (eg an electrician) should isolate and disconnect all electricity supply to an item of plant (not just the control circuit) so that equipment cannot be inadvertently energised via another source or control system.
· Lockout ensures that locks are placed on switches or other energy sources in the “safe” or “off” position. During a group lockout, all members of the group must add their own locks to the group lockout devices and should never place a lock inside another individual’s lock. Warning or danger tags should be placed with each lock.
· Release energy from all potentially hazardous stored or residual energy sources. Such making safe includes springs, elevated parts, rotating flywheels, hydraulic systems, electrical systems and air, gas, steam, or water pressure
· Personal danger tags for each worker on the plant must put on the isolation lock. This is a warning that the equipment is in an unsafe condition and that operation of that equipment may endanger the person who attached the tag.
· Out of service tags provide notice that distinguishes appliances or equipment out of operation for repairs and alteration or plant that is still being installed. Clearly, while an out of service tag is attached to the appliance or equipment, it should not be operated.
· Testing should be carried out by trying to re-activate the plant without exposing the worker or others to risk. This ensures that the isolation procedures are effective and all stored energies have been dissipated.
Adequate isolation procedures must be established and followed at all times. Additional information about lock out, tagging and isolation procedures can be found on many government websites such as this: http://www.worksafe.vic.gov.au/forms-and-publications/forms-and-publications/lock-out-and-tagging-of-plant.
Laurence Jones is risk assessment director at the TT Club.
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