Machine Safety and Maintenance Bypass

So I was contemplating an interesting topic today. What is your guy's take on having a maintenance bypass switch to bypass machine safety functions while the switch is engaged to manually move the machine without the use of an HMI and password?

I know that I would prefer to use a keyed type switch for this function at the minimum.

Maybe if it takes a key that is locked up and has to be signed out. We have some stuff kinda like that, it is under tight lock down and you can only use it with the proper paperwork and conditions. It just does machine safety though no e stops or guarding or anything that involves personal safety.

Also they are in the control cabinet so no operators even see it to wonder what does that do.

Its a sketchy deal, I wouldn't want to be the guy that set it up.

Just my two cents,

sparkie said:

What is your guy's take on having a maintenance bypass switch to bypass machine safety functions while the switch is engaged to manually move the machine ...

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We use maintenance (control room engages 'maintenance mode') to bypass process interlocks and allow belt scales to be calibrated, bucket elevators to be run, compactors, etc. Nothing is bypassed that prevents maintenance people from poking their fingers where it is dangerous, or jamming their tools..

No Emergency stops, pull cords, tamper switches ... for that stuff we lock out the 600V (Canada) and power up the control circuit so they can mess with that sort of stuff.

In our mill, any password is posted on a sticky on the side of the monitor within a week. I don't trust passwords for *ANYTHING*

Perhaps I mis-understood 'machine safety'?

I feel like I work in the wild west compared to most of you guys, from what you post.

We have a big fish splitter that we nicknamed "Sputnik"

Last week the cover safety went bad during production so Sputnik stopped.

They came and got me to fix it........but only after they had one guy hold the contactor in with a screwdriver while another guy finished the run of fish that was in the bin already.

I guess being at sea, everyone has the "Get-er-Done one way or another" mentality.
(Even though doing things like this is totally against company policy)

BCS

It is a nice idea, but in my experience if maintenance needs to find a way around a safety interlock for troubleshooting, they will work that problem out just fine on their own.

Bubba.

Bering C Sparky said:

I feel like I work in the wild west compared to most of you guys, from what you post.

.......but only after they had one guy hold the contactor in with a screwdriver while another guy finished the run of fish that was in the bin already.
I guess being at sea, everyone has the "Get-er-Done one way or another" mentality.
(Even though doing things like this is totally against company policy)

BCS

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Safety first unless it takes too long or costs too much. Then it's a really close third. I have never worked at a place that didn't follow this unwritten, and often denied rule.


Bubba.

Oh no no no no no no no no no
You do something like that, even if you do it perfectly, you will get blamed for WHATEVER goes wrong with that machine from that day forward. You will be tried and convicted in the court of public opinion, even if it has nothing to do with what you did.
And Heaven forbid, somebody does get hurt on that machine...
DON'T DO IT! Unless you are a glutton for punishment.

I have seen an older machine that had a bypass mode for the door safety's so that you could cycle the machine one cycle at a time with the doors open, but it would not actually run product like that (the vacuum wouldn't work). So you could cycle all of the mechanical parts, but the machine wouldn't run product.

It also had a big warning/disclaimer on the machine that let you know the heads would close and the belt would move without the door closed. It was absolutely necessary for troubleshooting the machine, but could not be used "in a pinch" to run.

Of course, in that plant everyone was very good about not giving maintenance passwords to production. If it was discovered that production had the password an email was sent out to maintenance supervision about the password change and why and it was written up in policy to not share maintenance level passwords or you could be subject to termination.

There were a few points on certain processes that had a "jog" button but all of these were up on catwalks or had to be used from 10ft or greater ladders as well to prevent production from using them. The code was also commented on who made the change and at which person's request. It has always been my policy to require written documentation which I will take a copy of home and store to do anything that could be considered as unsafe. If the person in upper-management was unwilling to take the liability then it couldn't be that safe, right?

I worked in offshore drilling for a while and the only bypass was to allow machines to move freely without being controlled by an anti-collision system. If for example a sensor failed in one, all others would stop. To get past this, you could either fix the sensor or flick a switch to move the machine out of the way.
The key was in the ship's safe and only to be released under a work permit signed by the day or night manager.

Bering C Sparky said:

I guess being at sea, everyone has the "Get-er-Done one way or another" mentality.
(Even though doing things like this is totally against company policy)

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I've spent a fair share of time at sea and I understand this... especially when, due to logistics and customs, the parts are weeks away.
The worst I saw was a mechanic jumping on top of a machine to operate an hydraulic lever and running the risk of being sandwiched inside the machine.
Turns out that the position feedback of the machine was screwed and they did not know what to do to move the machine.
A couple of bits forced in the CPU and the machine was where it was needed safely.
And yes... until I figured that one out (a short cable at a gland) I'd be called day or night to move it and keep production.

I have seen the following on several machines.

Switch #1 - keyed switch - left position remove key, right position - run
Switch #2 - keyed switch - left position remove key, right position - maintenance mode. the spare key is locked up in case you loose the first key.

when maintenance needs to work on the system, remove key from switch #1 and put into switch #2.
this allows maintenance to manually control the machine without running it.
maintenance does their thing and homes the machine - machine home light "on"
remove key from switch #2 and insert into switch #1

regards,
james

In auto plants, the only thing I've seen allowed is everyone in the non-safe area would have some type of deadman with them (robot teach pendant, or remote HMI with e-stop (Siemens), etc). Clumsy if you're trying to adjust something that requires motion power on but better than a escort out of the building if you're caught not following the rules. I've seen prox replacements done by two electricians; one to hold the prox and the other to turn the wrench.

We put maintenance routines into the programming.


By toggling the switch on the maintenance page you remove all the program routines from the outputs and put in maintenance routine to the outputs. It can operate individual functions without bypassing the safety protocol. And only one function at a time.

Machine must be put back into remote at the HMI.

Agreed, but ...

Bering C Sparky - agreed. We have to curb the 'enthusiasm' of new hires a lot. Many of the most dangerous employees have retired (yay). It takes a generation or two to make changes in the safety culture of a large business.

Bubba - I agree that safety is not top priority in some cases. But it *ALWAYS* has to be mine. The lowest I allow my safety standards to drop is the highest our maintenance guys will raise theirs. It sux, but that's how it is!

Bitmonkey - I agree, but maybe I am a glutten - I usually give them a workable solution. I write up the bypass description, that includes any morbid and dangerous side effects I can come up with, and get a supervisor to 'sign off'. So far, I've gotten 2 signatures in 10+ years. Miraculously, they find a way to shut down the system and fix it instead of signing.

I guess I should have suggested that as a solution. It's not technology based, it's .. psychology based?

Many of the most dangerous employees have retired (yay). It takes a generation or two to make changes in the safety culture of a large business.

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Careful, I am one of the old guys, the only electrician onboard this vessel (when I am here) and before this I owned and ran my own contracting buisness.

So more than likely I resemble the exact people you are cheering because they are gone.

Dont get me wrong, safety has its place.....as long as you take it in moderation.

BCS

At the Risk of over Assessing this...

Safety hat on...

I keep trying to remind people in these situations, and while we should always welcome and appreciate different people's experiences and examples; the OP's case, whether hypothetical, or not, is most likely not the same, or should not be assumed to be the same, as yours, or most of what you have experienced before.

What is missing from the conversation so far is the mention of a Risk Assessment, and more importantly a specific Risk Assessment of the OP's application, if one does indeed exist.

This is what should determine whether a manual, maintenance, or temporary bypass of a Safety Function may be permitted, or not. If the unmitigation of the risk or hazard is deemed acceptable, under certain conditions, then the bypass may be implemented. Other mitigating measures may be introduced to reduce the risk while bypassing, such as cordoning off the exposed area, reducing functionality or speeds using specialised controls to manage the bypass safely. Indication such as warning lights, sounders and signage. Two man team performing the task or observation with a lookout for emergency intervention, etc.

All possible, under certain conditions, but completely dependent on the results of a Risk Assessment. If such a feature was implemented at the original design phase then the original Risk Assessment would have already taken its use into account, stipulating the measures to be used to perform the bypass as safely as possible. If introducing a bypass at a later stage then a new Risk Assessment would need to be carried out to assess it's feasibility.

So looking at this again...

sparkie said:

Machine Safety and Maintenance Bypass

So I was contemplating an interesting topic today. What is your guy's take on having a maintenance bypass switch to bypass machine safety functions while the switch is engaged to manually move the machine without the use of an HMI and password?

I know that I would prefer to use a keyed type switch for this function at the minimum.

Click to expand...

sparkie,

I'm not sure what "guy" you're referring to here but the "guy" whose opinion matters most here is the "guy" that carries out the required Risk Assessment. No one person here can tell you which way to go, in my humble, but educated opinion and that includes me. I'll let you decide for yourself.

BCS said:

...Dont get me wrong, safety has its place.....as long as you take it in moderation...

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That depends a lot on who the Moderator is, my friend!

Regards,
George