Relay question

m_paper · Mar 26, 2019

Hi all I have a relay question, we are currently using Allen Bradley tamper proof relays. Two wired in series one set of contacts is used a plc safety input the other set is used for the dc output bus on the plc. My question is with the contractor/relay being in a dusty environment is it possible to replace the relays with an ice cube style relay or will that change the classification of the safety system?

the_msp · Mar 26, 2019

Welcome to the forum!

the other set is used for the dc output bus on the plc

By that do you mean solely the bus plane power for the IO modules, or is it actually giving the field supply to the outputs themselves?

m_paper · Mar 26, 2019

It is the bus that supply’s the output voltage

the_msp · Mar 26, 2019

So the original intention was that these relays being powered off, that the outputs stop in an emergency situation?

m_paper · Mar 26, 2019

To clarify the outputs will still light up on the card but there will be no voltage to the contacts

m_paper · Mar 26, 2019

The_msp that is correct

the_msp · Mar 26, 2019

Then yes it would need to be risk assessed again and a new performance level calculated.

m_paper · Mar 26, 2019

Thank you for your input. I was afraid of that perhaps a positive pressure to the cabinet would be a better solution. Those type of contractor relays do not handle dust very will even though it’s limited amount of dust it’s always been a problem. Thanks again

the_msp · Mar 26, 2019

What is the application and environment?

m_paper · Mar 26, 2019

Bath and kitchen converting (paper towels and toilet paper) a lot of dust. The cabinets are fairly well sealed but the dust manages to find away in

GaryS · Mar 26, 2019

This sounds like it's a safety relay if so it must be replaced with another safety relay
those are Forced Guided Contacts
You may try to place the relay inside a NEMA 4 enclosure to protect it.

sparkie · Mar 26, 2019

Can we get a part number for the relay? A lot of times you can find a product that is very similar but rated for that environment. We had some issues with an AB safety relay and swapped it out for an Omron one in most of our controllers. They only last a little longer, but they are less than half the price. Perhaps you would be able to do the same.

As a side note, and by design, those safety relays are finicky.

Relay question

m_paper

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m_paper

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