How to measure water level in a vacuum...

[drbitboy]

So now we know the 20 torr is relative to atmospheric.

What? Where did you get that idea?

 

[Peter Nachtwey]

What? Where did you get that idea?

There is contradictory information on what the absolute pressure is in the vessel. Some posts mention 760-20=740 torr others mention 20 torr absolute. Torr is an absolute scale.



SO WHAT IS THE F#$%ING ABSOLUTE PRESSURE IN THE VESSEL?
It makes no difference. I don't care anymore.


Again, I think there have been a lot of good suggestions that have all be rejected except mine, not yet at least.


I have wasted too much time on this thread. I could have got further ahead with a five minute talk with Mas01 and whomever is his mechanical engineer is. At least I would know what they are really trying to test which we don't know yet but now I don't care anymore.

 

[AkaHammer]

Sorry but this post is why I don't answer any posts anymore on this site because then i get email everytime someone posts, get tired of deleting emails. some times we kinda over due it partially because people don't read all the posts jump in in the middle and ask questions already answered other times we have not thought thru what op said and other times op does not give enough information other times we have not thought thru what we are saying. I like answer above 5 minutes on phone talking at 200-400 words per minute versus typing for me at about 15 words per minute this could have been solved or at least a better understanding of what op wants. But we really beat it up sometimes, I personally if it is not my area of expertise, going sit on side lines and observe where as some folks want to be the hero and are way off track, that said in less i know exactly what is up meaning probably done it before(47 years of this stuff), this topic is not my area of expertise, but if was to hazard a guess radar probe with some tweaking, used in a lot of tanks of different purposes flawlessly. (I did what I am railing against)

I still enjoy reading posts but sometimes it is like this one just get it done. There is probably more than one way to solve this but we all know based on circumstances sometimes we don't get do or get to best solution for what ever reason, application unique or specific.

Sounds like you need level control in a tank +/- CM under vacuum with water and vapor or steam, referenced internally certainly will have the issues describe with reference tube Blown down might be a idea like in boiler world a lot of sensor have to be blown down at periodic intervals. also might add this have used some different pressure transducers in similar boiler condensate return tank (pressure tank not vacuum)with external blow downs to remove water vapor or sedimete from sensor system, when this is done usually takes sensor offline from sometime until temperature in dp sensor stabilize, did not like this again not my area of expertise but radar sensor?

So good luck getting what you need/want

 

[drbitboy]

SO WHAT IS THE ... ABSOLUTE PRESSURE IN THE VESSEL?

As I noted before, I am the flailing guilty party who wrongly assumed the absolute pressure was 740torr.

The only authoritative statement from OP is that the pressure is 20torr absolute.

Also, the vessel shell is several inches thick and is large enough to contain a commercial aircraft engine; I am not going to do the calculations, but even for a vessel that large, I don't think that thickness would be required to withstand a mere 20inHg of vacuum relative to atmospheric.


The liquid level is what is being measured and compared to discrete pre-set levels to make discrete choices when to start and stop a savaging scavenging pump.


The vessel pressure does not matter: liquid water, having a density much higher than the vapor plus any air, will accumulate in the bottom of the vessel. Some of the available techniques to measure it are floats, non-contact (radar, ultrasonic, etc.), and differential pressure, the latter of which can be achieved through two separate, atmospheric-relative measurements, one of the vacuum (which is already going to the PLC), and the other via a tap somewhere in the pump suction line.

 

[drbitboy]

I don't answer any posts anymore on this site because then i get email everytime someone posts, get tired of deleting emails.

I get it; not everyone has too much time on their hands.

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[TWS]

I am going to jump into this one time.
E&H
The FMD71/FMD72 consists of 2 sensor modules and one transmitter. One sensor module measures the hydrostatic pressure (high pressure) and the other one the head pressure (low pressure). The level (electronic differential pressure) is calculated in the transmitter using these two digital values.

 

[AkaHammer]

The point is Dr. Bit Man sometimes we beat somethings to death on here #1, #2 again people say things not thought out or have no experience with topic.

So again the guy that said with phone call 5 minutes, to get a handle on understanding or even to provide a solution if you done it before it good.

Rather than beat it up for days with out the proper information.

an example car repair I have 2 BMW's and a Mercedes some time I will research something about a car problem and actually read like 700-800 posts all bull and then find one that one sentence in a paragraph solved. again people say things with no experience or no clue for some reason, this makes things worse.

So thanks for the tips on forum but I should have to do that, I should be able to participate normally without 100 post on something with no information or ridiculous.

Don't get me wrong I was happy to find the one sentence in 800 posts to fix my BMW, scared to death of BMW dealer.

The internet and social is showing it's problems.

If can can offer real advice to someone stuck great but if it is bs spare us.

Not pointed at you Dr Bit Man because you have proven yourself on this forum to be a very smart fellow and thank you I have learned a lot.

Hope everyone gets where I am coming from.

not trying to offend anyone, let's stick to business don't want this to become like BMW forums or other forums doing this waste of time stuff.

 

[NetNathan]

Maybe this unit? It works from -1 to 4 bar environment.
https://www.ifm.com/us/en/product/LR8000