PLC backplane trouble

hairan

Member
Join Date
Jun 2012
Location
delhi
Posts
2
i am using siemens S7 400. The CPU stopped working. I checked the diagnostic buffer but didn't get any fault. I started replacing every DI Do and I/O module, but it din't help. Lastly I went for the backplane. Can anyone suggest me the possible reason behind failure of the backplane of CPU.

after some days the backplane of DI also failed.

Please suggest reasons.....
 
Having installed quite a few S7-400 PLC systems in Delhi I can confirm that heat and humidity are a problem.
Another serious problem is dirt (gritty dirt blows in from the desert West of Delhi).
Another problem is corrossive contaminents used in industry
such as soda ash (caustic soda).
Other contaminents might be conductive such as coal dust, iron oxide and iron cromite.
I installed S7-400's in a glass container factory at Bahadurgarh Delhi where all of these problems exist.

You can probably get the backplane working again by very careful cleaning of the contact pins. However, any "fix" is likely to be temporary.

I battled for years to get good clean control rooms with multiple split system air conditioners.
 
Out of curiosity, are these backplanes passive printed circuits with connectors, or are there active components?
 
Having installed quite a few S7-400 PLC systems in Delhi I can confirm that heat and humidity are a problem.
Another serious problem is dirt (gritty dirt blows in from the desert West of Delhi).
Another problem is corrossive contaminents used in industry
such as soda ash (caustic soda).
Other contaminents might be conductive such as coal dust, iron oxide and iron cromite.
I installed S7-400's in a glass container factory at Bahadurgarh Delhi where all of these problems exist.

You can probably get the backplane working again by very careful cleaning of the contact pins. However, any "fix" is likely to be temporary.

I battled for years to get good clean control rooms with multiple split system air conditioners.

John, do you have any experiance with the S7-300-series in these conditions?
 
I once experienced the total destruction of a complete S7-400 rack and MP370 panel due to that corrosive gases from a melting furnace crept into the control room. The gases were so corrosive that they ate away at galvanized steel, and red copper bars turned coal black.

Dont think that S7-300 will be better than S7-400. S7-300 do not have a real backplane, but links from module to module. The modules are just regular circuit boards on the inside, just like S7-400.
There are special outdoor versions of S7-300, ET200M and ET200S called SIPLUS. Not sure if they also have extra coating. Could be worth investigating.

Maybe bring in fresh air from outside the polluted area. And maybe cool and filter the fresh air separately from the rest of the plant.
 
Sorry ivo.maenen I have had limited experience with S7-300 and that was in pretty much ideal conditions in Tasmania.

Sorry Jesper but there is no reliable clean air outside. I have walked outside at midday and looked at the sun thinking it was the moon.

By the way, this is the reason we never use remote I/O. We try to get a good control room built in the best location available and try to get it sealed with air lock doors. It is most important that the multiple air conditioners cannot possibly introduce air from outside. Even then it is almost impossible to stop people using witches brooms to clean the floor so stirring up the dust.

All cable entry holes should be sealed with expanding polyurethane foam.

One of the real problems in India is the extreme reluctance to have anything ready ontime. Thus it is often necessary to start a new factory before the control room is sealed with lights and air conditioning. Much of the damage to electronic equipment occurs during this start up phase but probably not showing up for a year or two.

I know some of these things apply in other parts of the world but India really is a challenge.
 

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