Can a modern PLC tolorate that level of abuse?

A simple question:
Can a modern PLC withstand the level of abuse demonstrated below? That system is running at the time the picture is taken.
Respect for the S5. Please share your experiences.

Depending what kind of dust that is, I would probably say yes.

Dust & Moisture?

I worked in a bakery for a number of years. Some of the older less sealed panels looked like that regularly. The good thing about flour is that its non-conductive.

There was also a huge new panel installed that had no air conditioning. Only filters and fans that plugged up almost daily. It was run for months with the doors wide open. We would blow out the panel every few days with compressed air, but there must have been a 16th inch of dust on everything. It was a compact logix with about 8 VFDs, 2 of them being 100HP.

S5-115U was/is a very rugged PLC indeed.
One thing that fails repeatedly on S5-115U is the PSU. Notice how always the plastic on the PSU is less yellow tainted than the rest of the PLC. Its because they fail and get replaced regularly, every 5-10 years or so.


For current PLCs such as S7, I have experienced very few failures due to the environment. Some defects out-of-the-box, but very few once the system is up and running.

I used to work in the Powdered Metals industry, it was plagued with black fine dust like that. Only it was conductive Graphite used in the powdered metals as a die lubricant. If a panel didn't get properly sealed it would usually let us know with a direct short. If we were lucky it was on the secondary not the primary side of things.

That's not even dirty.

You should see some of the places we go into. Yikes!!!

I should start taking pictures and post them. Why is this still working?

Dust, conductive or non-conductive, acts like a blanket so you'd think the extra trapped heat would shorten the lifespan of some of the electronics. I've also experienced a few panels that lost their NEMA rating over time and were pretty filthy.

S5's are great... no doubt

Back in the relay days.... I worked for International Paper in a printing division, we had large offset printers and they had a ton of dust that would be sprayed on the sheets after the print and so that they would not stick together... one of the helpers decided to clean all the dust from the controls cabinet, he took a blow nozzle and blew that non conductive dust into every one of the 500 plus relays, we bought everyone we could find and then started taking apart the rest of the relays and cleaning them by hand, the machine was down for 1 week 2 men 3 shifts doing nothing but opening relays and cleaning them with contact cleaner

in the old days, the coppertrace seperation was a lot bigger, so less creepage.
itink fire is a big risk at contactors

Looking at that picture, I would be less worried about the dust
than the obvious pawprints around the run-stop switch.

I work around circuit board solder mask sprayers (mostly green goo) & everything inside the panel, the parts storage cabinets, the other equipment around, the roof around the exhaust blower (& it's near the parking lot), tables & the inspection PC & monitor are coated with a green overmist that doesn't wash off except with a special solvent that eats anything plastic or rubber - including your belt & shoes.

JesperMP said:

S5-115U was/is a very rugged PLC indeed.
One thing that fails repeatedly on S5-115U is the PSU. Notice how always the plastic on the PSU is less yellow tainted than the rest of the PLC. Its because they fail and get replaced regularly, every 5-10 years or so.


For current PLCs such as S7, I have experienced very few failures due to the environment. Some defects out-of-the-box, but very few once the system is up and running.

Click to expand...

Unfortunately its big brother the S5-135U was a wimp and prone to failure at high temperatures.

Back in the '90s I put an S5-135u in a mine in South Africa. This PLC controlled an ice plant that delivered super cooled water to the mine shafts. I warned the main contractor during the install, that the location of the main rack in a shed was asking for trouble once summer came around. I commissioned this PLC in July - August which is winter in SA. My recommendation about heat issues came after another install we made in a VW plant in Mexico where the S5-135u started to 'flip out' when the plant got hot.

Sure enough, once November came around in SA when summer was about to start, the shed where the S5-135u was located became hot and outputs on the main rack began randomly firing causing equipment damage.

Main contractor tried to blame us, but we had minutes of meetings to prove they were advised. The mine even tried to sue Siemens for damages.

Anyone who has been around packing plants should be familiar with the term "paunch". Imagine a PLC cabinet with some of that moisture and nastiness inside. It lasted a LONG time.

To reduce cost, a lot of places now offer coated and un-coated circuit board versions for PLCs, drives, and IO. If anyone is having trouble with newer equipment failing, talk to your supplier to make sure you are getting the coated equipment.