Mos(maintainance Operating Switch)

Good Evening,
I Am Working On Ab Plc's.in Which Customer Has Told Me To Make Logic For Mos( Maintainance Operating Switch). Can Any One Tell Me How It Works? What Is The Importance Of This Switch?

Thx In Advance.

Best Regards,
Parag Uike

Sounds to me like they want some keyswitch that would let maintainance people run the machine in manual. I would contact the customer first and get a definition from them. This MOS may mean different things to different industries and there may be standards and or safety protocols that you need to look in to.

To me that would mean some sort of lock-out switch, when maintenance is being done, this will disable the equipment...

Mark Buskell said:

I would contact the customer first and get a definition from them.

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Good advise

Automation_Tech said:

To me that would mean some sort of lock-out switch, when maintenance is being done, this will disable the equipment...




Good advise

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No , that is the incoming isolator and a padlock !

I offer most equipment with three modes , Auto/Man/Test
Test allow the mechanics to jam it solid of they require .
But do get advice .

10BaseT. said:

No , that is the incoming isolator and a padlock !...

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YOU ^...

Automation_Tech said:

To me that would mean some sort of lock-out switch, when maintenance is being done, this will disable the equipment...

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ME ^...the key part to this equation is bold and a little larger font in case you did not see it the first time...

disabling switches: these are not to take place of LOTO or any other safety, but they are to isolate one part of a machine, you can not ALLWAYS lockout everything and do your work, so again the key here is TO ME...

Automation_Tech said:

disabling switches: these are not to take place of LOTO or any other safety, but they are to isolate one part of a machine, you can not ALLWAYS lockout everything and do your work, so again the key here is TO ME...

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Then you really shouldn't have refered to it as a lockout switch in your first post (key or not).

allscott said:

Then you really shouldn't have refered to it as a lockout switch in your first post (key or not).

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That would be a opinion…we all are entitled to our own, different verbiage is lost in translation, excuse me if I am from this side of the world and I refer to something oneway…(not yours, another key)

If its not a lock-out then what is it called? a disabling switch? petty if you ask me, the point is WE can not just call something only one thing, the OP hade a question about the verbiage, I gave my opinion, that is all, just a opinion...

Lock outs should be refered to as lock outs and only lock outs... if you start calling other things lock outs, people will get the wrong idea, and could get hurt by relying on this "lock out" to actually lock out the machine, yet it doesn't.

Using multiple names, especially ones shared already by other things, to describe something is not only confusing but can be dangerous.


To me, a maintanence operating switch would be a switch to allow maintanence personel to move a machine in ways that the normal sequence would not allow, to allow maitanence to easily get at places on a machine or to easily check parts. e.g. A press to move up and down without parts being in place, or clamping cylinders to move with commands from the person.

For all the machines at our shop, such switches are either keyed switches, where maintanence personel are the only ones with the keys, or pushbuttons on HMIs that are either passworded, or on passworded screens.

I consider it a little more then petty verbage. A lockout is a means of remove all energy sources from a machine, process, or a specific part of that machine or process.

A keyswitch does not do that (key). Far too often these are mistaken as a means of locking out a piece of equipment.

BTW, I worked on your side of the world for quite a few years.

You are right everyone is entitled to their own opinion in the free world, even if they are wrong.

parag uike said:

.. Can Any One Tell Me How It Works?...

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If you read this thread from the top down....

The answer to your question is NO! we have no idea (or too many) you would think we could help people instead of bickering..

Automation_Tech said:

That would be a opinion…we all are entitled to our own, different verbiage is lost in translation, excuse me if I am from this side of the world and I refer to something oneway…(not yours, another key)

If its not a lock-out then what is it called? a disabling switch? petty if you ask me, the point is WE can not just call something only one thing, the OP hade a question about the verbiage, I gave my opinion, that is all, just a opinion...

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Opinion is super when your fingers are munched .......

You want to work safe , then park the machine safley , and lockout all services - simple as that ! where machinery has local isolators , then these may allow the continued operation of equipemnt while maintenance is carried out -

A key switch or password protected HMI page is not safe for this activity , but may be acceptable to allow operation of equipment out of sequence or without interlocking .