ES : FIVE STEPS TO ENSURE ELECTRICAL SAFETY

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Chapter : Electrical Safety

 

FIVE STEPS TO ENSURE ELECTRICAL SAFETY

STEP 1: Disconnect Power Supply completely

1. 

   
   

   Safe procedures for de-energizing the equipment shall be determined before circuits are de-energized.
2. Ensure ALL electrical energy sources are identified and disconnected including elevator main switch, lighting switches, auxiliary supplies, emergency batteries, and emergency generators.
3. All stored energy must be released. Do not attempt to discharge capacitors, this is highly dangerous and will damage the equipment. Allow capacitors to discharge normally and then test to ensure that they are safely de-energised. Secure any machinery that may be capable of producing electrical energy from moving.  
• WARNING!
  When rotated manually, for example when moving the car/counterweight by releasing the brake, machines will act as generators and may recharge the intermediate circuit to some extent even though the power is turned off.
4. Depending on the work task it may be necessary for other non-electrical stored energy to be made safe, (counterweight / car may need supporting.) Ensure there is no other possibility of moving equipment that may cause, trapping, falling or crushing hazards.

STEP 2: Secure against Re-connection

1. A lock and tag must be placed on each switch. Always lock the switch. If this is not possible agree an alternative safe method with your supervisor.
2. The tag must state clearly:

• The equipment MUST NOT be turned on.
• The name of the person responsible for removing the tag.
• If it is not possible to fit a lock one additional safety element to the tag must be provided, (e.g. removal of fuses and storage in a secure place).

STEP 3: Verify that the Installation is De-energized
 
Test and inspect that the circuit is safely de-energized using suitable approved test equipment.
 
The test must verify that:

• There are no energized circuits.
• There are no related risks from capacitance, induced voltages or otherfeedback.

WARNING
Inverter drives usually remain energised for about 5 minutes after the power has been disconnected. DO NOT work on the drive, hoisting motor or braking resistors until you have verified that this energy has been discharged.

Where voltages above 600V DC or 400V AC are tested the test equipment must be checked before and after the test.
 
STEP 4: Check the requirements for Earthing in special circumstances

1. Emergency Back Up Supplies (in the event of mains power failure)
 
Some buildings such as hospitals and large computing facilities are equipped with emergency power supplies, usually these are generators but sometimes a completely independent power source is utilized.
It is essential that you, together with your supervisor, liaise with the building owner or his appointed representative to verify that the emergency back up supply is also safely disconnected from the elevator equipment and that this disconnection has not impaired the function of other essential facilities in the building.

2. Bonding of Conductors

• This is employed in very rare cases where the isolation of electrical equipment is made at a remote location and it is considered necessary for safety reasons.
• This technique is not normally used with low voltage (below 1000v ac) supplies.
• The operation may only be carried out by qualified personnel in co-operation with the person responsible for the building electrification who must ensure that the technique can be safely employed in this situation.
• When this technique is employed all conductors supplying the elevator equipment should be bonded together and to the MAIN EARTH of the building. Earth bonding may be achieved by connecting conductors of suitable size to carry the potential short circuit currents to the electrical installation earthing system.

STEP 5: Provide protection against adjacent live parts

If there are parts of an electrical installation in the vicinity of the work location,that cannot be de-energized, then special additional precautions are necessary and shall be applied before work starts.

1. Provide protection by screen, barrier, enclosure or insulating covering.
2. If the measures above cannot be carried out, protection shall be provided by maintaining a safe distance to bare live parts and when necessary, providing appropriate supervision.

WARNING
When working in the vicinity of moving parts (For example, a neighbour elevator left in use), the additional protections may be needed.