1.1 Safety Measures

A rotating electrical machine is dangerous even when it looks idle. It may still be connected to a live supply, its capacitors may hold charge, its rotor may be turned by the load it drives, and its heavy parts can crush hands and feet when they are lifted. Disassembly also exposes sharp edges, hot surfaces, oil, varnish and dust. Safety measures are the fixed steps and habits that protect the technician and the machine before and during the work. This topic covers the preparation for safe work, the protective clothing worn, and the safe handling of tools. The tools themselves are described under disassembling tools and equipment.

Preparing the machine and the work area

Before any tool touches the machine, the following steps are completed in order:

1. Obtain the job card or permission to work and read the machine history.
2. Isolate the machine at the supply: switch off the isolator or breaker feeding the machine and its control panel.
3. Lock the isolator with a personal padlock and attach a tag showing who is working, so that nobody switches it back on.
4. Prove that the machine is dead with a tested voltmeter at the terminals, using the prove, test, prove method.
5. Discharge any capacitor, such as a motor run capacitor, through a suitable resistor before touching its terminals.
6. Disconnect the supply cables and label each one before removing it.
7. Make sure the load cannot turn the rotor: disconnect the coupling or lock the driven equipment.
8. Clear the work area, provide good lighting and place a bench or a clean mat with trays for the parts.

Work on a machine that is connected to a supply is not done during disassembly. If the machine has been running, it is allowed to cool, because the frame, the end caps and the bearings can burn the skin.

1.1.1 Donning of PPEs

Donning means putting on protective equipment. Personal protective equipment (PPE) is the last line of defence and is worn together with isolation and safe methods, never instead of them. It is put on before work begins, checked for damage and worn until the work and the cleaning are finished.

Good practice when donning PPE:

• Remove rings, watches, necklaces and loose items that can touch live parts or catch on moving parts.
• Tie back long hair and secure loose clothing.
• Check each item before use: no holes in gloves, no cracks in glasses, soles of boots not worn smooth.
• Replace PPE that is damaged, and do not share items that must fit the individual, such as respirators.
• Take off gloves before turning or holding a rotating part.

1.1.2 Handling of Tools

Tools are the technician’s instruments, but a wrong or damaged tool damages the machine and injures the user. Safe handling covers the choice of tool, its use and its storage.

Choice and use

• Use the right tool for the job: a spanner of the correct size for the nut, a puller for the bearing, a mallet for the end cap. A screwdriver is not used as a chisel or a lever.
• Inspect before use: a cracked handle, a mushroomed head on a chisel or a spanner with a worn jaw is taken out of service.
• Pull, do not push, on a spanner: if it slips, the hand is not driven into the machine. The jaws are fitted fully on the nut.
• Use soft-faced tools on machine parts: a rawhide, plastic or copper mallet, not a steel hammer, is used on end caps, shafts and housings so that the metal is not marked or cracked.
• Keep sharp edges away from the body: cut away from the hand and carry sharp tools with their points down.

Lifting and carrying

Rotors, armatures and end caps of large machines are heavy and awkward. A part too heavy for one person is lifted with a hoist, a sling and a lifting eye, or by two people. Lift with the legs and keep the back straight. Never put a hand or a foot under a suspended part, and lay heavy parts on wooden blocks so that fingers are not trapped.

Compressed air and solvents

Compressed air is used at low pressure and is never pointed at a person. Solvents are used in a ventilated place away from sparks and flames, and the container is closed after use.

Storage

After use, tools are cleaned, counted and returned to the tool board or box. A missing tool is looked for at once, because a tool left inside a machine can cause a serious fault when the machine runs.