Safety Circuits Round two

[stef]

Afternoon Ladies and Gents,

Due to another accident overseas all ongoing and planned projects on site need to have failsafe tamperproof safety contactors in the safety circuit. Great.:bulb2: Probably retrofit as well, knowing my luck.


I have come across Allen Bradley, they also do the safety relays (Ex guard master products). However, the two suppliers I found are RS (limited range in rating) and a distributor called Routeco (very limited stock and long waiting time on certain ranges)

I know Pilz, Omron and Sick and others do safety relays as well, but I cant seem to find an alternative to Allen Bradley
safety contactors. I don't believe that such a product is a sole brand. There must be other manufacturers.

Anyone knows any alternatives? or encounter the same problem?

Thanks.

 

[joel89]

what are you wanting an ESR?? why do you need a safety contactor? need more info

 

[stef]

what are you wanting an ESR?? why do you need a safety contactor? need more info

Hi Joel,

I don't want it, believe me. I am a contractor and do what the customer wants. This is a group wide thing and was initiated, amongst other safety measures, from the US. If a machinery has the potential that moving parts can be accessed without removing fixed panels then a two channel safety relay with tamper proof safety contactor has to be implemented. Now I am looking for Allen Bradley alternatives.

hope this explains it.

 

[Darkwood]

You may need to get a risk assessment to be done this will give the Category of Relay required to meet the requirements of the control system, you cant just retrofit a safety relay into the controls and think that will do.
In some cases a complete redesign of the control system may be required in other cases it can be a small integration but as the original design is been altered you will have to ensure it is up to BS60204.

Ensure you don't get caught up as the responsible party as it sounds like this isn't your field thus I heed strong warnings that you bring in an Electrical Engineer familiar with machine controls and the standards to apply.

From your posts it seems the machine didn't meet standards in the first place and someone is now trying to prevent it from happening again which is why Im concerned your going to dig yourself a big hole here, if further incidents occur after fitting the safety relays then regardless of what caused the accident a full assessment will be done on the design of the safety system and the measures taken to make the machine safe, if you miss anything or under categorise it then you'll be in the firing line.

 

[stef]

Thanks for the reply, darkwood.

The risk assessments are don by a contracted company called Rockwell. They assess the category and design a safety circuit to be implemented. You are right, most of the machines don't meet todays standards. They are mainly Mazaks and Hitachi Seiki machines from the nineties.

i know this is awkward stuff, that is why Rockwell was brought in to take off the responsibility. I do what they recommend but I am the one who needs to source the parts. Once the mod is made, Rockwell comes in again and check my work.

 

[Darkwood]

Rockwell are a supplier of safety equipment surely if you have used them to do the risk assessment they can supply the correct gear to meet the assessment they have spec'd, i take it you were unaware of this?

 

[stef]

Yes, darkwood, I was aware of it. The issue I have is the limited rage at RS and the low/no stock at Routeco. So I was looking for alternatives to Allen Bradley (which is part of the Rockwell group by the way). I was hoping for Pilz but they don't do the contactors.

I am already expecting a nightmare ...

 

[Darkwood]

Have you tried Scattergoods and Johnsons they have a bigger range of ESR and wider choice.

 

[stef]

No! Thanks for that, certainly will look into this

 

[SheffSimon]

Your other issue will be Rockwell will have done their calcs based on Rockwell components, using the data (mean time to failure etc) for those specific components. If you starting chucking other manufacturers, or indeed different Rockwell components into the mix (Siemens do safety contactors with fixed auxiliaries, use loads of em) Rockwell will want to re-do their calcs, which equals more money......

 

[stef]

Your other issue will be Rockwell will have done their calcs based on Rockwell components, using the data (mean time to failure etc) for those specific components. If you starting chucking other manufacturers, or indeed different Rockwell components into the mix (Siemens do safety contactors with fixed auxiliaries, use loads of em) Rockwell will want to re-do their calcs, which equals more money......

Good point SheffSimon, more to worry ...

 

[gnuuser]

heres a link to rockwell distributors in the UK
Rockwell equipment is rock solid and dependable even though it is more expensive
If rockwell is doing the assessment rest assured the design will be top notch.
seimans does make safety equipment as well but our plant uses rockwell so Im more familiar with it than seimans
Rockwell Automation United Kingdom

generally these devices are installed like an e-stop circuit (all door switches, light screen's, tamper switches wired in series)
but your contactors will interrupt the power to machine motors, and heaters or they may completely isolate the power depending on how they are configured