TechArchive

Original article date: September 1998

Interlocks can be incorporated into rotary switches control units exchange boxes and door locking devices to govern many types of industrial equipment. Here’s how to specify them correctly.

Safe operation of plant and machinery can only be ensured by following a correct procedure. Actions carried out incorrectly or in ignorance of the potential dangers can lead to injury or death or damage to plant and equipment. Instructions or safe working practices alone do not guarantee correct operation.

Fitting interlocking imposes effective physical controls which lead an operator through a safe and predetermined sequence of events. By eliminating the potential for human error interlocking ensures that the correct action is performed in the correct way every time the equipment is used.. Interlocks can be applied to most items of machinery and plant that must be operated in a pre-determined or controlled manner. Other common applications include robot production lines HV and LV switchgear food slicing plant transfer machines presses paint plants moulding machines dryers shot blasting machines shredders saw mills palletisers and guillotines.

For example interlocking a machine tool will ensure that it is switched off and has come to rest before access to moving parts is permitted. Similarly interlocks fitted to electrical switchgear will ensure that the power supply is isolated before allowing entry to a high voltage area. Not only does key transfer interlocking impose safe conditions of access to dangerous machinery it also ensures that equipment cannot be restarted until all personnel are clear of the hazard and the key sequence has been reversed.

Key interlocks use a special type of lock mechanism which traps or frees an operating key when associated machinery or plant is in a certain condition. Typically one key is supplied to operate each pair of interlocks. The transfer of keys from one interlock to another ensures that equipment can only be operated in a safe predetermined sequence.

Interlocks can be incorporated into rotary switches control units exchange boxes and door locking devices to govern many types of industrial equipment. Fortress Interlocks uses a high security radial pin tumbler mechanism that is robust secure and easily maintained. The design allows over 100 000 non-masterable lock combinations plus an additional series of masterable locks for special applications. Each different key combination is allocated a code number of up to 10 characters by which the lock and key are identified.

Fortress Interlocks has published a new brochure to guide safety engineers through the step-by-step specification of customised access equipment using simple table diagrams.

• Fortress Interlocks

September 1998