Control panels

[silva.foxx]

I've been in the industrial maintenance 'game' since mid '94 so seen a fair few panels, main control panels that is. As some here may recall, I'm larking around trying to outdo C&G in creating a structured electrical apprenticeship program for our recruit, so am looking back over my time.

I'm still learning so this is an opportunity for me to reinforce my understanding of things and also to remember most of what I've forgotten!

Ventilation! What's the general view on forced-air ventilation? Fan to blow in or suck out?

Drives (VFDs). Low for cool air or high up where heat rises before expelling out through vent?

PLCs. Low down in cooler air or at top (seems to be quite common with a viewing window!)?

.

 

[netblindpaul]

Manuf' instructions 1st mate!

Which ever air removal method you use you need to allow for make up air.

IMHO the air in or air out depends on your environment.

VFD's/Inverters.Servo drives, again manuf' instr, but, do you want the hot air of the heat sinks affecting the rest of the panel ir high up being sucked straight out?

PLC's bit more difficult, out of any humid air stream caused by panel air con.

This is more of a thermal engineering Q than an electrical, and I don't think this is taught on ANY electrical course TBH!!!

 

[Darkwood]

One of lives biggest cunumdrums anyone just starting out, to suck or blow :nono:

 

[Knobhead]

I prefer filtered air forced in. Any leaks around doors or panel sections have air forced out and not drawing dust in. I’ve always worked in dusty environments so it’s been a constant battle. We had a new engineering manager and he couldn’t understand why I’d banned the use of switch grease on one plant, he found out at the next shutdown when a combination of grease, heat and cement dust had glued main switches closed.

VFD’s near the top so there’s room for associated control gear in the relative cool at the bottom.

PLC’s at eye level. OK maybe not my eye level.

 

[pmac10]

was called to a brand new machine tonight and it took longer to find the electrical enclosure than it did to rectify the problem, but this enclosure was the opposite of what Tony prefers, air out, VFD's at the bottom and PLC above eye level, (i'm a short ---), guess it depends on the enviroment, have worked around industrial ovens where you certainly wouldn't want to blow air in because of temperature but also because baking flour hung in the air.

 

[Knobhead]

Hot environments are a nightmare. I’ve worked on over 40 kilns and furnaces, all panels would be remote to protect them. But sometimes a local panel couldn’t be avoided but if possible air would be ducted to them or low-pressure compressed air blown in. Dust has always been the bane of my life!

BTW how’s the new job going?

 

[silva.foxx]

BTW how’s the new job going?

Thanks for asking... I chose to remain with the Black Stuff... long story cut too short but this apprentice thing was a huge factor in me staying put! Also 'better the devil...' in the current climate!

Back to these control panels...

We have a KHS filler. The panel fan is blowing air in at the base of the right hand door. There is a filter in the grille. The air is then expelled at the top of the left hand door. Immediately in front of the fan (obviously when door closed) is the main drive motor protection and supply isolation transformer. After recent floor work the fan had drawn in a concrete mist so everything was covered in crud.

Another thing in the bevvy-boxing industry is the ability for the panel ventilation to draw in a tar-like air and coat the gubbins. Everything becomes sticky!

One of the things I'll be doing with the App. initially is to go around parts of the plant and open up a number of panels. So that he becomes familiar with layouts and components we'll note locations of devices and collate some evidence that we'll look over at the end of the task. We'll test some voltages within the panel and basically get him quickly accustomed to potential dangers and have him become "respectfully confident" around live equipment (safety being paramount and extreme supervision being a novice!).

Thanks so far guys.

 

[lman_271860]

New to the forum, my background is in industrial electronics,

I have attached a good guide by hoffman on the subject

the main issue is that if the cabinet overheats the life span of the electronics can end up being severely degraded, usually they just get through the warranty period and fail !

we use the battery powered usb loggers by lascar which log the temperature at settable sampling rates. these things are worth their weight in gold for spotting problems.

there are many panel manufacturers who have fan sizing software to calculate airflow on their web sites.

as an exercise for your apprentice, get one of the loggers from rs or farnell and get him to do preventative maintenance on all the electrical cabinets, it will save you an absolute fortune !


regards
lman_271860

 

[silva.foxx]

Welcome to the forum and thanks for the info... good suggestion is that. We do (are supposed to) panel temp & humidity checks... yawn... yeah I know.

.

 

[netblindpaul]

silva,
The panels we built had thermostats built into the panel and wired into the PLC, high panel temp warning, and then high panel temp shut down, that stopped the machine.

 

[silva.foxx]

I replaced a load of obsolete interface relays in said Filler panel approx. 18 months ago. You know the Siemens slim-line ones. A nice battleship grey colour with the signature bluey-green logo and label strip. They have since turned a shade of beige.

A colleague replaced some other type of relays the other night. He said they just crumbled when he attempted to undo the terminals!

 

[lman_271860]

I have been working on the same reliability and maintainability project across quite a few automotive and aerospace companies and have seen some infant failures on very expensive machine tool spindle and servo systems.

when the manufacturers specify a maximum ambient temperature for drives most people assume that would be related to the average cabinet temperature but .............................
you really need to read the small print !

you will find a maximum air inlet temperature at the bottom of the heat sink at the drive !!!!

when we monitored the inlet temperatures they exceeded manufacturers specification therefore NO WARRANTY CHACHING

in this case the cabinet was completely sealed and being chilled with rittal air conditioning units set to 35 Celsius and was happily reporting everything was aok.

the solution to the problem was simple we made some ducting to route the chiller air straight under the drives

regards
lman_271860

 

[netblindpaul]

lman,
You may well have worked with my previous employers kit then, two of them in fact.
One was an automotive machine tool builder, the other was a manufacturer of CNC/PLC/Servo & inverter systems.
Yes we did specify a maximum inlet temperature for the heat sink.
Oh, we could tell too, or at least our workshop guys could.
A lot to do with electrolytics drying out at elevated temperatures.

 

[lman_271860]

NetBlindPaul,

electrolytic capacitor degradation is a very interesting subject and is usually the root cause of a very high % of all electronics failure

the temperature rating on high frequency low ESR caps is only valid for 2000 hours only IE about 3 months !

lman _271860

 

[netblindpaul]

Exactly!