Are PLCs being replaced more due to failures or lack of spare parts?

A question for the people who work on industrial sites.


A customer complained about having to revamp several premium PLC that worked fine because Schneider stopped manufacturing the brand and they had a whole production line of them.


I was asking myself the question if you were changing the PLC of productions lines or machines because they became too old (failures or risk of failure of the old components), because you wanted to upgrade to new functionalities or just because they stopped being manufactured and you ran out of spare parts.

For me, lately, it has been because management keeps wanting more and more OEE data to be gathered. I've been replacing PLC5 with Contrologix (mostly used L63 and a few L7X), and SLC with L32E. I have changed some PLC5 stuff out because the output cards were individually fused and the tabs were breaking off the little fuse holder and those were getting harder to find on ebay. I must admit, I'm becoming very spoiled with ethernet connectivity.

We are modernising some PLCs because OEM suppliers do not have the capability to program our older PLC5 when we require major changes.

We have a module in a PLC5 PLC that there is only one person in Rockwell UK that remembers how to program them. For us it is a black box, and non-standard as the memory chips were upgraded by the supplier, so our spare is useless. Mind you, it went in around the late 1980s.......

Siemens drives are going to have to be replaced because they cannot support the spares.

We have the capability to program most of our old PLCs, but people want more connectivity and functionality, so we are forced to upgrade.

Iner said:

just because they stopped being manufactured and you ran out of spare parts.

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This is a big one for me driving obsolescence.

Similarly Win7 is no longer supported by Microsoft... but I'd bet my bottom dollar any end user on here has a WinXP (actual or virtual) onsite.

For production, I don't want to have to "ebay" a PLC and be down for more than an hour. Even an hour downtime because of a PLC/module is too much.

In my neck of the woods, we seem to do nothing only hope the old plc's run forever. They wouldn't buy spare modules when they were available, now they won't pay for full new systems.
I mostly hope I retire, before the plc's do, else it's ebay or a a frenzied search in the store "miscellaneous section".

Same here, 90% of our plant uses obsolete/silver series'ed equipment, not to mention nine different manufacturer platforms, any request to upgrade or replace falls on deaf ears, until that is until we get a failure, then it's a huge panic to get replacements sometimes costing 3 times the normal price and paying a premium delivery to have any aquired components delivered by courier.


Steve

I have been in this game for over 35 years and what I have noticed are a number of factors 1. Rohs compliance has forced new hardware so the older was EOL quite quicky, 2. manufacturers have latched onto profiteering by continuously updating versions without backward compatibility. 3. sign of the times must have the latest (like phones), well governments are now realising that we are consuming resources at a rapid rate and I have heard that there may be legislation to manufacture stuff with a longer lifespan. It's amazing, government bodies seem to have a think tank and to justify their jobs they continuously come up with new compliance legislation (under a guise of H&S or other S...T), but these rules are also causing waste. I guess it's a way of modern life, we need to save the planet, but we need growth and of course, companies want to maximise their profits. Look at Sonos & bricking older models.

Change from PLC’s to what?
Don’t DCS or all other electronic devices have similar issues?

Just seems to be part of the territory.

Iner said:

I was asking myself the question if you were changing the PLC of productions lines or machines because they became too old (failures or risk of failure of the old components), because you wanted to upgrade to new functionalities or just because they stopped being manufactured and you ran out of spare parts.

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I see all of them, no particular emphasis on one or the other. Most of my work is on controls for new machines, but we do support clients with older machines where the machine hardware is still fine for some more years but the current controls on new systems offer functionality and improvements that the original controls cannot match. So where applicable and desired by clients we occasionally update older machines with a new PLC. Also every now and then an older control system dies and it is getting harder (and more expensive) to get spares. Whenever we upgrade a machine we keep the old parts so we can also help out our customers with spares if they do not want to do a full controls upgrade.

Being an Allen-Bradley SI we are doing a lot of upgrades. But AB does help with that by giving Step Forward pricing on the older equipment. We have used the PLC5 to ControlLogix conversion equipment a few times and now they have the SLC500 to CompactLogix hardware out now.

I work for a site that still uses Honeywell MFC and AMC controllers, the only reason we still use these controllers is because spares are abundant (and less expensive than a full replacement) and the controllers are still very reliable and can be integrated with modern SCADA solutions despite being tech from the mid 1980s.



I haven't really encountered a PLC that had a high failure rate but have replaced many (Usually GE / Idec / Omron) due to not being able to get spare parts.

Probably the biggest issue I see is mfrs having to obsolete products because of regulatory issues (ie RoHS), and/or the manufacturers of the internal components stop making them, forcing the PLC mfrs to change designs. That’s a big issue with PLC5s and SLCs right now. A-B couldn’t make some PLC5 cards even if they wanted to unless they use secondary market sources for the parts, and they have too much at stake to do that.

In water/wastewater though, a new thing I’ve been seeing is that new DHS cyber security regulations are driving a lot of old control systems out the door because they can’t meet the requirements. (For those not in the US, that’s the Dept. of Homeland Security, who have been assessing larger W/WW systems and discovering foreign actors having accessed them; not doing anything yet, but able to if they wanted to. So DHS are forcing users to change how they do things.).

JaxGTO said:

Being an Allen-Bradley SI we are doing a lot of upgrades. But AB does help with that by giving Step Forward pricing on the older equipment. We have used the PLC5 to ControlLogix conversion equipment a few times and now they have the SLC500 to CompactLogix hardware out now.

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I will always push to just rip the old hardware out and put new and rewire and label from PLC5 to Control. I've done a few, and the headaches they leave behind are terrible. The IO number count is always messed up after 0-7 and people will argue with you that they are off by one. That is why the bit they are trending isn't pulsing.

SLC500 to remote IO has been some of the smoothest upgrades I've ever done. Usually people are very very nervous about it. But, if you mapped it all right and setup your new logic (that is just AOIs) right... It just power ups and goes. Usually no need for an entire IO test, just test a couple easy ones and let it go. Unlike a new install, where every IO point should be tested that it's working.

Our customers usually try to keep the old hardware running until it becomes impossible. Only then, 5 minutes past 12 do they consider to do a proper upgrade.

I have done a few upgrade projects, and they are actually fun to do. The pressure is high partly because you are working on and preparing an upgrade on a working plant that may fall over at any minute. And implementing the upgrade is also intense since we have to keep the actual downtime to a minimum because we are interrupting the production of an already running plant with orders that have to be delivered.

When done, the customers are grateful, and are marvelling at such luxuries as large HMI screens, logging of data, remote support via the internet, much better diagnostics.

For a standard machine, I have made an upgrade kit consisting of new PLC hardware, new PLC and HMI programs, new diagrams, new user manual, and guide for installing the upgrade. It sells very well.

Btw, I find that the greatest issue is old operator panels.
1. They are more prone to fail. Screens go dark or are busted. Keys gets worn. Touch becomes inoperable.
2. They have a much shorter product life span than PLCs.
3. The programs are propietary and you usually cannot merely upload them from an old panel and download to a new.
4. There are many brands, but few that last for more than 2 decades. Dread is when a customer has an operator panel of a brand that doesnt exist or has just dumped their operator panel business.