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Machinery Safety - System Implementation

We can help you understand your compliance to internationally recognized standards and regulations. Compliance and Safety is such a huge very broad topic, that most of the employees in companies that are involved in safety – having such a lot to attend to – they don`t have the time to be informed or comply.

The harmonised European Standard EN 954-1 for the design of safety related parts of the control system lists 5 categories for the required behaviour

of that part. It is deemed the designer`s responsibility to objectively assess the risk and identify what level is required for the safety related control.

The following information is a guide to determine those levels. It must be stressed that it is only intended as a guide for the designer, and must be used together with quantified risk assessment data.


S. Severity of injury
S1 Slight (normally reversible)
S2 Serious (normally non-reversible)
Take account of the worst case injury. If this is no more than a slight cut or bruise, then select S1. If the consequences are more severe, up to and including death, then select S2.
F. Frequency and/or exposure time to hazard
F1 Seldom to quite often and/or short exposure
F2 Frequent to continuous and/or long exposure
Select F2 if a person is exposed to the hazard point frequently. It is irrelevant whether it is the same person or a different person. Select F1 if access is only required from time to time and the exposure time is short.
P. Possibility of avoiding the hazard
P1 Possible under specific conditions

P2 Less possible
This is generally related to the speed at which the hazard arises, proximity to the hazard point, level of training and expertise of operators. If, in your opinion, the operator could recognise the hazard and avoid injury, select P1. otherwise, select P2.

Periodically operated safety gate of a lathe. A finished workpiece is removed manually from a collet chuck and a new one inserted. Then the lathing job is started. At the end the workpiece is removed again by hand.

Workpiece is inserted manually

S2 Danger of non-reversible injuries caused by the rotating parts.
F2 Since a workpiece must be removed and inserted manually into the hazardous area for each tooling process, there would be great danger to attempt this before the drive has come to a complete stop, if the safety gate was not monitored.
P2 The only possibility to avoid this is to monitor the safety gate because routine tasks provoke negligence.

Category 4

EN 1088 defines the design of limit switches and how they must be attached to a safety gate.

EN 60 204-1 instructs us that these limit switches must be monitored.

As you can see, these regulations are like a gearbox with each gear meshing in with every other.

Also see: emergency stip units, HMI, light curtain monitors, motion control, power monitoring relays, programmable safety systems (PSS), safe bus systems, safety mats, safety relays, safety switches, voltage monitoring relays