Decentralised i/o and high amb temperatures ?

JesperMP · Mar 9, 2009

Hi.

We are considering to spread out decentralised i/o to a much higher degree than we have before.
Then someone asks the fine question "what if the project is in a tropical location ?".
For the main control panels, we could stick an aircon module on each panel, or place the panels in a central control room with aircon.
But all the little boxes with Profibus or Profinet i/o, what about them ?
Some of our projects are where the amb temperature is 40+ degr. And in a production plant the temperature may be even higher. And inside the boxes, the temperature will be even higher still. It gets awfully close to the 55 degr. that is the typical max.

Has anyone experience with using decentralised i/o in really hot locations ?

widelto · Mar 9, 2009

Hi Jesper:
We live in the tropics and amb. temeperature is about 85 - 90 degrees farenheit all year long, I saw and equipment the other day that used a kind of high speed turbine ( more than 10000 rpm )that convert pressurized air ( 80 psi) into a nicer temperature about 65-70 Defgrees F. It is appropiate for small enclosures.

JesperMP · Mar 9, 2009

Yeah, I know that one already. I think it is called a venturi cooler.
But I really cannot connect pressurised air out to all the places we need an i/o box.
I see some people use that device when there is an operator panel. I guess a panel generates more heat, and panels or normally not rated so high. Only to 50 degr.C.

shooter · Mar 9, 2009

Please join me one time on board of a commercial ship.
today outside is +5, in control room 40 celsius.
when outside is 30 inside of control box (with the BIG switches) it is 60
in the engineroom where the big engines are blasting a normal temp is 50 celsius . I use a lot of wago out there with loydds approval and as the plc itself is not getting very hot i have seen temps of 70 celsius, however a small blower to circulate only inside the box does help enough not to derate the power supplies too much. It is not the temp but the aircirculation.
in still air (or when the box is packed full you see high temps.

JesperMP · Mar 9, 2009

Thanks shooter.

So you are saying that you have Wago i/o in areas where the temperature 50 degrees or higher ?
And you dont have problems with the Wago i/o, but you do have with the power supplies ?

diat150 · Mar 9, 2009

Ive been around alot of different PLC's in stainless steel enclosures, middle of the gulf of mexico, out in the open(direct sunlight all day long), no vents at all, and never ran across any problems. I would think the ******t temp in those boxes could get 110-120 degrees f easy.

Nick B · Mar 9, 2009

Siemens has Siplus rated ET200 I/O which would work in those extremes.

JesperMP · Mar 10, 2009

Thanks all.
I am beginning to think that it is not such a big problem.

Nick B said:
Siemens has Siplus rated ET200 I/O which would work in those extremes.

We are using ET200S everywhere, but not the SIPLUS variant. SIPLUS costs a mere 100% more than regular ET200S, so to begin with I would like to start with the regular types. But is is nice to have as an option, in case that we do get temperature problems.

BTalbot · Mar 10, 2009

How about getting rid of the enclosure? Turck's BL67 is rated to 55 C. Could also save on install cost.
http://www.turck-usa.com/Products/Networks/BL67/index.htm

They also have a nice IP67 24Vdc power supply

http://www.turck-usa.com/Products/Networks/Power_Supplies/PSU67_power_supply.htm

Binaural · Mar 10, 2009

The heat is probably not so much of a concern as humidity. 50° is unlikely to harm your equipment but regular heating-cooling cycles with boxes that are not well sealed could cause condensation and all the evils that stem from that. I like BTTalbot's idea too, open control boxes are not a bad idea for very distributed systems.

JesperMP · Mar 10, 2009

I would prefer to keep it as ET200S.
It is our standard, there is the greatest diversity of modules, and the cost is reasonable - even if you factor in the enclosure.
And, that everything must be connected via M12 or M8 connectors is also a leap we are hesitant to take.
And, I dont think that there is much heating from the modules themselves. It is the extreme amb temperature that is the problem. So getting rid of the enclosure wont make such a big difference.

Thanks anyway

shooter · May 5, 2009

I only overrate the power supplies about 3 times as they dissipate lots of heat. and have a derating curve in their manual.
wago has lloyds and can withstand higher temps.
they are all tested in factory.
I always try to have the power supplies outside the small boxes and central in a cooled area. The power i bring out to the plc in same cable as comms.
even a simple utp cable can have 1 amp, i am using bigger ones however.
standard is 0.75 is minimum in ships.

Sparkz · May 5, 2009

Hi Jesper, You've probably already made up your mind, but just to let you know:
I have installed 4 industrial crate washers over the last 3 years. They all were equipped with 2 ET200S-Profibus racks (approx. 20 modules DI/DO/AI/AO each), mounted in stainless steel boxes near the heated water reservoirs. The average temperature inside the enclosures is 59°C. These machines are running 16 hours a day, up to 6 days a week.

Haven't had any temperature related problems yet. But the long term effect? Keeping my fingers crossed...

JesperMP · May 8, 2009

Thanks sparkz.
That is valuable information.
What is the amb temperature ?
Do you have a PSU in the enclosure, or do you bring in 24V from an ouside source ?

Sparkz · May 8, 2009

Amb temperature is approx. 30°C during shifts, humidity is up to 95%.
There's no power supply inside the cabinets (didn't want to push our luck...).

Decentralised i/o and high amb temperatures ?

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