Regulations for Multiple HMI's

HarleyHetz

Member
H
Join Date
Jun 2012
Location
Memphis, TN
Posts
39
Has anyone heard of any "regulations" regarding multiple HMI's capable of identical control over a single PLC?
The reason I ask is that my boss is telling me that there is a "new OSHA rule" about it...I haven't heard anything, nor can I find anyone yet who has... But, he says that one HMI must "ask for and receive permission to control the machine". Then, when that operator is finished, and the next one wants to control from the other location, the process is reversed.
This all comes about because he wants me to add an HMI to an existing AB PLC that mirrors the existing HMI but is out of sight of the original.
Thanks in advance for any input!!
 
I'm not sure if there are specific rules or regulations about this, but it definitely is a good idea to ensure that the HMIs are not fighting each other or giving contradictory instructions.
 
mk42 said:
I'm not sure if there are specific rules or regulations about this, but it definitely is a good idea to ensure that the HMIs are not fighting each other or giving contradictory instructions.
Click to expand...
Yea, don't get me wrong, I'm not saying that it's a bad idea...just looking to read the exact regulation so that I get dot my "I's" and cross my "T's".
 
FactoryTalktotheHand said:
I highly doubt OSHA would get involved with something like this. OSHA typically deals with more generalized safety requirements.
Click to expand...

True. But if there is a regulation out there anywhere , and you get cited for something, OSHA can ding you for not following that regulation if following it would have prevented the incident.
 
I believe they are bound by the regulatory equivalent of ex post facto. OSHA can't hold you liable for a standard they themselves have not yet recognized in one of their publications. I know OSHA is all about moving targets but even they realize that would be asking too much.

Keith
 
This is backwards. If there is a PLC, the HMI should only monitor it or supply it with data from operators. The HMI should stay out of the way when it comes to control.
JMHO of course, but it should be a regulation. :eek:

HarleyHetz said:
Has anyone heard of any "regulations" regarding multiple HMI's capable of identical control over a single PLC?
The reason I ask is that my boss is telling me that there is a "new OSHA rule" about it...I haven't heard anything, nor can I find anyone yet who has... But, he says that one HMI must "ask for and receive permission to control the machine". Then, when that operator is finished, and the next one wants to control from the other location, the process is reversed.
This all comes about because he wants me to add an HMI to an existing AB PLC that mirrors the existing HMI but is out of sight of the original.
Thanks in advance for any input!!
Click to expand...
 
Can't help you on the regulations, but having multiple HMIs is not a bad practice when done appropriately.

I've seen places with 3 identical HMIs in different areas of the plant that control the exact same equipment. There are no issues if you have all of the logic in the PLC, not the HMI. Always use momentary pushbuttons instead of maintained pushbuttons on the HMI, etc.
 
kamenges said:
I believe they are bound by the regulatory equivalent of ex post facto. OSHA can't hold you liable for a standard they themselves have not yet recognized in one of their publications. I know OSHA is all about moving targets but even they realize that would be asking too much.

Keith
Click to expand...
Except that the General Duty Clause is so open ended that almost anything can be cited.
 
HarleyHetz said:
my boss is telling me that there is a "new OSHA rule" about it...
Click to expand...

Ask him for a specific reference to this "new rule". (Not because you doubt him, but because you NEED to understand the letter and intent of the rule in order to comply with it).
 
jamesau said:
Ask him for a specific reference to this "new rule". (Not because you doubt him, but because you NEED to understand the letter and intent of the rule in order to comply with it).
Click to expand...

This is probably the best solution, although he may just delegate to you the task of figuring out what he is talking about.
 

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