Relay Logic panel from 1968...still going strong?

[Halabicky1]

Hello all, I have been in maintenance at my plant for 5 years now & progressed through the tiers to become a controls tech through several Allen Bradley training courses & on the job training. I am now at the point where I feel comfortable with my programming & PLCs in general.



However there is one panel in my plant where the machinery runs off old relay block controls & the wiring is a disaster (no labels left on wires jumpers everywhere.. ect.) we don't even have the original schematics. I'm not sure if this is even a question I should be asking on this forum, but I'm curious if anyone else has these same issues & what I could do to improve my understanding. Company just turned down a PLC upgrade because it costs too much money


As this is my first post & new to the forum please correct me if this is

 

[goghie]

You should make official writing report and point to the safety issues to supervisors and than do nothing unless they approve modification. If there are not safety issues then you can play if you like.

 

[Ken Moore]

If you are on some type of shift support, and have on occasion a little free time. You could start tracing and labelling wires. Maybe even develop a few hand sketches. Then if you have to support or migrate this panel, you will have a better understanding of how it works.

I bet a big part of the upgrade cost was determining what you have now.

 

[Halabicky1]

I was thinking that same thing.. that panel cant be up to current standards... although I'm not entirely sure what to point out exactly. The training we receive is mainly just programming not really teaching us what is up to code. I know there is multiple (3-4) wires coming off the same terminals for 460V & it looks like they are using the Neutral for grounding in some spots? Super confusing to me.

 

[Halabicky1]

If you are on some type of shift support, and have on occasion a little free time. You could start tracing and labelling wires. Maybe even develop a few hand sketches. Then if you have to support or migrate this panel, you will have a better understanding of how it works.

I bet a big part of the upgrade cost was determining what you have now.

Unfortunately I have little time to do that as the lines are running & usually getting called to other issues around the plant.. the panel has 460 terminals right next to 120 along with cobwebs holding everything together I would definitely want to lock out the panel before tracing anything.

 

[saultgeorge]

However there is one panel in my plant where the machinery runs off old relay block controls & the wiring is a disaster (no labels left on wires jumpers everywhere.. ect.)

This was in a plant where I worked that made small electrical parts. It was on a machine that printed information on the parts. It had a PLC and a lot of conveyors. I had a pair of lineman's and some other tools and I was going to re-wire it on a Saturday morning, but the Maint. tech in the area convinced me otherwise so we got a white board and made a print.

 

[drforsythe]

If you plan to work at this place for a while, I would recommend making a document that points out the risks that will come from a) not upgrading it and b) doing an upgrade. Let your management know the facts, not the emotions. Then make it a priority to learn as much about it as possible so when it fails, you can support the repair or upgrade of it.

 

[celichi]

Hello all, I have been in maintenance at my plant for 5 years now & progressed through the tiers to become a controls tech through several Allen Bradley training courses & on the job training. I am now at the point where I feel comfortable with my programming & PLCs in general.



However there is one panel in my plant where the machinery runs off old relay block controls & the wiring is a disaster (no labels left on wires jumpers everywhere.. ect.) we don't even have the original schematics. I'm not sure if this is even a question I should be asking on this forum, but I'm curious if anyone else has these same issues & what I could do to improve my understanding. Company just turned down a PLC upgrade because it costs too much money


As this is my first post & new to the forum please correct me if this is

Have seen this many many times. I would recommend you very carefully perform a Point to Point "As Built" electrical schematic of the panel (during downtime).

Once you have all the circuits drawn out, you could write the program to replace with a Micro or Unitronics or whatever controller you use currently at the facility (spare parts).

 

[kamenges]

This is likely the engineer in me talking but I would completely separate the execution and rationale of figuring out what you have from figuring out where you want to go.

There is certainly maintenance and support value in figuring out what you have now if you are going to be keeping it that way. More information is always better. But if you are thinking upgrade I wouldn't even glance at what you have now. How you would execute the control system in a plc is MUCH different that how you would do it with relays. Think about a simple single-button toggle. It can be done with nothing but relays but you certainly wouldn't want to code it that way.

If you are thinking upgrade, just watch what the machine does and ask the operators how it is supposed to work. Make a list of the hardware devices that are present. Operate on concept more than what is there. And incorporate operator wants into what you plan to do. In the end I think you will find that is a much better use of your available time. Not only do I think it would be quicker to execute with less impact on the actual machine, it will give you a much better idea of what the machine actually does and how it does it.

Keith

 

[Helliana]

I agree with kamenges. I wouldn't waste my time trying to figure out what was done in the 1960s. I would only invest my time and effort into an upgrade. I would find it hard to believe you cannot financially justify the upgrade when you consider the cost of downtime and the price of relays. Management will either have to make the decision of to invest a little money in hardware, or eat large amount of downtime when there is an issue. It is a waste of time and resources to try to make a schematic or clean up what is there.

 

[celichi]

I agree with kamenges. I wouldn't waste my time trying to figure out what was done in the 1960s. I would only invest my time and effort into an upgrade. I would find it hard to believe you cannot financially justify the upgrade when you consider the cost of downtime and the price of relays. Management will either have to make the decision of to invest a little money in hardware, or eat large amount of downtime when there is an issue. It is a waste of time and resources to try to make a schematic or clean up what is there.

I would like to see your opinion when the machine is down, and you have no idea what you had before.

It is never a bad idea to document what you have, nor a waste of time.

If you are right, just go throw out your existing documentation for every machine, you don't need it, just upgrade it.

LOL

 

[Helliana]

I would like to see your opinion when the machine is down, and you have no idea what you had before.

I continue to do what i have been doing to keep it running. I it like i would other obsolete control system, and repair was is economical and still supported, and upgrade what is not.



For example, if i had a machine with a PLC-5 that didn't have a comment program, i would not waste my time trying to go through by hand and comment every rung in the program. I would spend that time making a new program for a CompactLogix that i know will function and be able to be supported for a long amount of time in the future.

 

[parky]

It certainly does not look complicated, providing you find out exactly how it works, start from scratch do not bother with the existing relays & how they work it will probably confuse you. many old relay systems even put contacts in the cold side of coils to reduce the number of relays.
Talk to the operators, monitor the system running & it would not be difficult to come up with an operational spec, design any new system with at least 20% extra capacity (I/O & space). look for newer parts like drives and such.
Come up with new drawings and safety system that complies to current legislation.
I once was thrown into an upgrade that had over 120 relays in it, had the drawings, but found out that over the years the system had been modified extensively, operators claimed they did not know how it worked, the only info I got was it was a cutting press with about 10 "recipes" as such so the only info I gained was looking at the profusion of switches & timers to set the "Recipe" if you could call it that. But it probably would have taken me as long to try to understand & document the old system as start from scratch.

 

[drforsythe]

If you are the engineer who does no daily support of the machine or you are an OEM of such equipment you only need care about the functionality and upgrade path.

If you are the maintenance person who is responsible for keeping the machine in production, you only care about what is existing and what it will take to get it running as soon as possible.

If you are a controls engineer in the plant that this equipment operates in, then you care about both. You need to know what exists today so you can support it and the maintenance staff until it gets upgraded. You also need to know the process and what is required to create a new system.

The point of all of the above is that it is a matter of perspective what is needed. I have lots of equipment in my plant that I know needs an upgrade but am not given the capital or time to do said upgrades. Therefore it is important to know the existing systems to get them running when something stops them. I also have to be ready with an upgrade plan if given the opportunity for a longer term project.

 

[JesperMP]

I agree with Kamenges.

I would like to see your opinion when the machine is down, and you have no idea what you had before

That is not the situation at hand.

It is never a bad idea to document what you have, nor a waste of time.

In this case it is a question of what is the best use of the time. Trying to document a rats nest of wires without knowing how it is supposed to work, or trying to establish how the machine should or could work and ignore the wiring. The latter is more efficient. Especially if the aim is to replace the old control system.
The actual sensors and actuators must be documented of course, only the 'relay logic' can be ignored.

If you are right, just go throw out your existing documentation for every machine, you don't need it, just upgrade it.

That is not the situation at hand. He has no documentation to throw out.