I'm searching for level measuring system, for liquefied hydrogen storage tank. Tank is Dewar type. Tank inner diameter=23m, height=38m, temp=-253°C. Most instruments are not suitable for these temp. Any suggestion?
Bela Liptak's Instrument Engineering Handbook, Process Measurement and Analysis, Vol 1, has a description of the use a DP pressure transmitter on a level bubbler that employs impulse tubing in a configuration to allow the liquid to boil to its vapor phase, which is what the DP's high side senses.
In the 2003 edition, it's in Chapter 3.6 Differential Pressure Level Detectors in the section on cryogenic applications.
If I remember correctly it's just a regular DP cell at the bottom of the tank, not a direct mount seal type. The head of liquid oxygen pressurizes the gas in the tubing which is above the connection point at ambient temperature.
Sort of like a condensate pot upside-down.
Thank you David & RoyMatson for your kind informations.
As per your suggestions, I also want to use DP with other alternatives as well like servo, radar or capacitance type. But I have heard some cases of Liquid oxygen (-183 degC) using DP and Float level, unfortunately their float level was broken down and DP having inaccuracies. So I am afraid to use servo.
I found in a book (Hydrogen: Its Technology and Implication: Transmission and Storage - Volume 2,pg 65, sec. 18.104.22.168) capacitance gauge has been used frequently for LH2 (-253 degC). Then I talked with EH (Endress Hauser) about capacitance type but they said their capacitance type are not suitable for LH2. Then i asked them about displacer type. Will displacer (with its guide wire and pulley mechanism) sustain such low temperature? But they don't have any experience installing them in LH2. I don't know if radar will be suitable for LH2 or not.
I have used servo and radar for LNG (-162degC) project too. But for LH2 I don't have any experience, any specific code & standards or any other guidance.
Could you please suggest about using servo or radar or capacitance type? Also vendors if possible especially for capacitance type.
Thank you in advance.
For large ground based storage (low pressure), double walled, vacuum insulated storage tanks, just monitor the hydrostatic head with a d/p transmitter.
One connection at the bottom and and the other in the vapor space topside.
Lots of design issues involved, requiring close coordination with your vessel design team. d/p transmitter selection is a minor issue.
There are a number of engineering firms that specialize in the take design and code requirements. You'll have to work closely with them.
link intended for earlier posting:
contains a partial p&id with instrumentation
As I suspected they use a regular DP LI(T)page 10
The vertical line from the bottom of the tank up to valve 4 is full of gas but at the same pressure as gas phase plus the liquid head.