Liquid Level Instrument - Which Type 3

[pmover]

I'm a gearhead and i've been asked this question without really knowing an appropriate response. i thought my GPSA data book might have some information, but i could not locate any - may have overlooked too. for you instrument gurus . . .

for a vessel (Design P/T = 1100-psig/250°F respectively) that captures/filters liquids, which could be glycol, heavy distillate, &/or water, what type of liquid level instrument (switch or transmitter) would be best for this application?

currently looking at a guided radar wave instrument transmitter ($). the application is not liquid level control, but to drain the liquids from the vessel (open drain valve at 50% and close at 10%).

thanks!
-pmover

 

[danw2]

The two that come to mind for that pressure and temperature are differential pressure (DP) and bypass sight gauge with accessory switches.

DP is problematic with unknown or changing liquid densities. Error is directly proportional to ratio of liquid's specific gravity (Sg) to water's SG.

Bypass gauge is what's been used on boilers for eons, but I'm not sure of float design for varuing densities, bit the manufactirers can help you there. I use Wika's BNA line.

 

[biff44]

There are a couple of types.

There is one where either a two conducotr or coaxial transmission line is sent into the tank, and a head unit sends microwave or pulse energy down the line and measures the time delay from a return from the top level of the liquid.

Then there is a type that acts more like an actual radar, where an antenna beams a wireless microwave signal downward, and receives the wireless reflected signal.

Issues you might need to address are if there is a homogeneous liguid top level, or if there is foaming/sludge on the top confusing the true liquid level. The wireless radar type is easy to install, but can be fooled by stantions/ladders/pipes inside of the tank.

Magnetrol is one of numerous companies making this stuff. All of it is pretty expensive.

http://www.MaguffinMicrowave.com

Maguffin Microwave wireless design consulting

 

[waross]

I have been out of the loop for awhile and can't recommend a specific instrument, but I would be looking at float based switches, one mounted at the 50% level and the other at the 10% level.
This may turn out to not be feasible but it is certainly worth a brain storming session.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

This function would commonly be done with a magnetic float in a stainless steel tube with switches outside the tube.

 

[waross]

That sounds good Compositepro.
LPS

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[danw2]

These level indicators go by different names: magnetic liquid level, bypass liquid level, armored bypass liquid level.

They're all a pipe/tube rated to contain the pressure (at whatever temperature) that is piped to the pressure vessel which has a float containing a magnet inside.

The accessories are all outside the pipe/tube: scale, flags for indication, switches and even 4-20 analog.

Dozens of manufacturers: Wika, Kobold, Gems, Penberthy. K-tek, Magnetrol, and more.

 

[pmover]

All,

thanks for the useful responses. will investigate and then decide.

-pmover