9 - Control circuits and control functions
Last update 01/12/2021
Chapter 9 of the Standard details control circuit and control functions.
In the control function, the Standard summarizes the three categories of stop functions:
- Stop category 0;
- Stop category 1;
- Stop category 2.
Paragraph 9.2.3 details the functions of the machine, where we find:
- Start: the start function shall operate by energizing the relevant circuit
- Stop: stop function shall override related start functions
- Emergency operations (emergency stop, emergency switching off)
- Emergency stop: it shall function as a stop category 0 or as a stop category 1. The choice of the stop category of the emergency stop depends on the results of a risk assessment of the machine.
- Emergency switching off: it is accomplished by switching off the relevant supply by electromechanical switching devices, effecting a stop category 0 of machine actuators connected to this incoming supply.
Paragraph 220.127.116.11 describes the operating modes and the protective measures to provide when the machine is design and constructed to allow its use in several operating modes. In particular, the Standard specifies to fit a mode selector which can be locked in each position. Each position of the selector shall be clearly identifiable and shall correspond to a single operating mode. The Manufacturer shall improve protective measures for each operating mode.
It is clearly specified that mode selection by itself shall not initiate machine operation.
The Standard describes in the following paragraphs hold-to-run control [§ 18.104.22.168]; two-hand control [22.214.171.124]; enabling control [§ 126.96.36.199]; combined start and stop controls [§ 188.8.131.52].