Differential Pressure Measurement for DCS Cabinet Room

Yes

Yes, there are numerous ways.

But, why would you care? The control system doesn't!

Yes, there is. However, without any detail of the application, it is practically impossible to advise further.

It is not possible to give this detail within a single sentence, so try making as detailed a description as possible about the issue in, say, three or four paragraphs, please.

We have to maintain a positive pressure inside the room (DCS cabinet room) which is located away from DCS control room & it should be monitored by the operators .

Hence i need differntial pressure transmitter which can measure upto 0 to 1 mbar with accuracy . This transmitter should be able to measure the positive pressure inside room with respect to outside atmosphere.

Cut a hole in a wall and put a fan in it. Just make sure the fan blows INTO the room.

There is more to it than that, but it would part of a solution. The fan's air source would need to be clean(ed), for instance. A DP transducer could serve as a blanket monitor for fan failure, filter clogging, or too many doors/windows left open.

Of course, any reasonable person would know this and at least acknowledge those needs, as well as many others. Space cadets would not.

Needing pressure higher inside a cabinet than outside, ignores so many other details as to be useless.

So what? Are they the only numbers available? What size is the room - a broom cupboard or an Olympic stadium? That sort of thing. Three or four paragraphs is what the forum needs to come up with something approaching a useful answer to a post.

And please don't let the forum play "20 Questions", as to do so is the best way of annoying other contributors.

I think we have someone here who has no appreciation/understanding of the requirements of the "room".

WHY positive pressure is needed?

If it's 50°C hotter outside the room, is positive pressure still needed?

What inside the room needs to be at just higher that the pressure outside the room? The circuit board? The electrons doing the work?

<Beam me up, Scottie. AP#1 is lost in space>

There are circumstances where a positive pressure is not only desirable, but necessary. Having worked in the mining industry, having mineral laden dust in electronics cabinets will wreak havoc.

However, it doesn't require nano control, or even monitoring. That should have been taken care of during the original build.

Unfortunately, we are dealing with a clueless poster, so we may never know the application.

Agreed. When a control panel, MCC or even complete control room is in a hazardous area it's likely to be cheaper to keep it slightly pressurised using air from outside the area than to install zone-rated kit (if that's an option for eg traditional contactors).

But as you say, fancy pressure control seems OTT. Usually pressure switches are OK, maybe one to give an alarm on falling pressure, another to trip a breaker on low-low.

As far as I know pressure difference is NOT depending on room size. But of course I may be wrong, as usual.

Maybe Dwyer.

The inquiry is reasonable, so don't be discouraged by irrelevant criticisms.

Why do I sense (pun intended) that this "room" is located in a classified area, and AP wants to pressurize it to get around a potential costly hazardous classification problem for all the equipment in it.

Positive pressure systems are one of our banes down here.

If that is the case then the facility has a serious process materials containment problem. Which needs solving first.

Great answer!

I worked with DP transmitters when I was with a flowmeter manufacturing company. It was very straightforward using these in our systems. I had the job of programming the PLC with temp and pressure inputs. We were using modified patented pitot assemblies that worked quite well. We used Dwyer DP transmitters as low as 0.1 InH2O.

The highlight (NOT!) of that job was going into the field to calibrate the flowmeters in 5ft diameter ducts with contents at 575ºF using a traversing technique (which you probably know about). It was a coal fired power plant and the atmosphere was choking.

Anyway, a nice, very understandable, succinct post! GA!

It is very curious how participants react to a simple question.

They give the feeling that the one who asked is a stupid person who in fact does not know all the depth hidden behind his inquiry.

The question is about a differential pressure transmitter for Δp=1mbar. Does the reason for which the question was put have any impact on the answer? The only one would be if the transmitter can be "normal" or has to be for ex conditions. The rest has no reason neither to be mentioned nor discussed.

Matter of fact is not always present in our discussions.

Such devices are available either as mems or ceramic sensors for very low prices.

Is it possible to use a plumbing 'S' trap with a stand pipe of "tuned" length to maintain a set pressure in cm of water. A clear stand pipe can show the level from some distance if the water is coloured. Of course a stand pipe higher than the outside one would need to be on the inside to contain the water in cases of pressure loss or reversal. The 'S' trap would not be necessary just convenient.

In other words a water manometer large enough to be seen from a distance installed on the outside wall.

Jim