EHSR 1.2.4 Normal Stop Requirements

[kamenges]

We are finishing up a machine for delivery to the England. Since we don't do this very often we had a CE consultant in to evaluate the machine relative to several directives.

One of the items he found that we were not compliant with was concerning the normal stop function relative to the EHSR directive. According to EHSR 1.2.4.1, "Once the machine or its hazardous functions have stop, the energy supply to the actuators concerned must be cut off". The way the consultant seemed to be treating it, a normal stop is just an e-stop with a more gradual decel rate. That just seems a little odd.

I guess the question would be what constitutes energy being cut off from an actuator? For example, if a drive is disabled but not put into STO, is that considered having the energy cut off? If an air cylinder is retracted by a 2-position valve that is turned off as part of the stop, is that considered energy cut off?

OR are we talking about a contactor or relay (as appropriate) interrupting the energy source to the actuators? This would seem to be what is done in an e-stop.

Then, to add a little more latitude to the situation, you have EHSR 1.2.4.2, which talks about an operational stop. But this requires monitoring of the stopped condition. What are the requirements of this monitoring?

The thing that adds a little more frustration is that the whole machine is enclosed in a guard enclosure with monitored access points (doors with safety switches). We can easily bring the machine to a full stop before an operator could get to any hazards if a door is opened while the machine is running. We feel confident that the safety portion of the guard system is effective and reached the needed performance level. But relative to 1.2.4.2, this really wouldn't be monitoring the stop condition. It would be preventing access to the machine in an operational stop condition and rendering it safe if the guarding is violated. That doesn't seem to directly satisfy 1.2.4.2 but it logically seems safe?

How do you guys approach this problem? Is my consultant reading too much into the intend of the directive?

Thanks,
Keith

[James Mcquade]

please correct me if I am wrong on this, but isn't a CE consultant regarding Canadian standards and EU the European standards? they are similar, but different.

james

[kamenges]

In this case, CE is relative the the EU. From Wikipedia:

"CE" originated in 1985 as an abbreviation of Conformité Européenne (French for European Conformity),[3] but is not defined as such in the relevant legislation. The CE marking is a symbol of free marketability in the European Economic Area (Internal Market).

Keith

[Rob...]

A stop would be the disconnection of all forms of energy in the system. So, as you say contractors or STO, in pneumatic dump valves etc etc..

How you achieve the stop is up to you.

However it is your responsibility to ensure it meets at minimum the following standards:

En 69204-1

This standard will refer to others as to whatever the specific machine does, special regulations for e.g lifting equipment, rotating machination, press breaks etc..

Without this documentation you cannot have the machine CE marked, an without that, illegal for sale on the European market.

[JesperMP]

The text
"Once the machinery or its hazardous functions have stopped, the energy supply to the actuators concerned must be cut off."Means that as a minimum the power must be cut off by contactors, of if electronic devices are used they must have STO functionality.
The "once .. have stopped" means that if there is a risk due to the motor coasting to standstill, then some measure like electronic braking may be used, which also must be safe, Safe Stop (SS1), Safe Brake Control (SBC), or some other variant.
Regarding pneumatic actuators, then yes you have to consider how there are stopped/deenergized safely.

All of the EHSR entries are to be understood as requirements that may be relevant to your machine.
What we do when we make the risk assessment, is that we list it under the EHSR entry that may be relevant to the risk. So if for stopping, it would be either 1.2.4.1 or 1.2.4.2, but not both.
Every single risk may be noted under several EHSR entries.
For example one risk may be countered ("risk reduction by ..") by safe stopping, emergency stop monitoring, fixed guarding, removal of energy sources, instructions to operators etc.
It is a chore, but you get used to it.