Emergency Stop Pushbuttons

Hello Everyone

Had a question on emergency stop buttons

One of my customers in the oil and gas industry has multiple emergency stop buttons wired into a panel that are then wired into an SIS system. When any one of the buttons is pushed on this panel, it activates certain logic to shut down specific valve/motors associated with it. Actually, a few of those buttons shut down the plant operation, while other only shut down a few devices.

The PHA that they performed did not classify any of those emergency stop buttons as SIL rated SIF's, so they were asking me today if there were any specific ISA, IEC, PSM/OSHA or API standards that required testing of those emergency stop buttons at a specific frequency (event though they are not SIL rated SIF's). Any input that you can provide would be greatly appreciated.

Thanks in advance

It can't be an emergency stop without a SIL rating. The whole design and validation of a safety function involves the SIL rating. This includes the buttons, the logic / safety relay / outputs etc etc

I cannot understand how they have got to that conclusion. Someone has made a mistake or got things very mis-understood.

It's just a general stop button and if it is dressed as emergency stop buttons then they have some problems.

I know it puts food on the table, but I wouldn't put my name to this particular machine without some clarification first.


A good read nevertheless here:
https://machinerysafety101.com/2009/03/06/emergency-stop-whats-so-confusing-about-that/

A SIF could end up with SIL0, no SIL, depending on acceptable risk vs actual risk. The numbers should be found in the risk assesment.

Otherwise I agree with janner. Sounds weird with emergency stop as non-SIL.