dp dell level measurement
dp dell level measurement
(OP)
I am trying to measure the liquid level in a vessel that is operated under a vacuum where NaOH is being evaporated from 32% to 50%. The low side leg is filled with Halocarbon, while the high side is tapped near the bottom. We are constantly battling accurate readings. Could this installation be improved to get better results, or would a bridle and radar probe be the best solution?





RE: dp dell level measurement
RE: dp dell level measurement
What level are you working at? 1m? 5m? 20m?
Is the low leg (Halocarbon) a filled capillary or filled impulse tubing?
Is a smart transmitter (low drift) or an older one with zero/span pots?
Dan
RE: dp dell level measurement
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
Correct?
How subject to temperature changes is the low leg? Outdoors? sunlight/clouds? Indoors, radiant heat from a nearby process? Can you coorelate the accuracy changes to temperature changes the low leg sees?
RE: dp dell level measurement
RE: dp dell level measurement
Dan
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
A few thoughts and questions which may help understand the problem, excuse me if some of them sound simple or obvious.
What temperature and vacuum are you operating at?
How is the liquid level in the reference leg maintained. Is it possible that as it does not have a diaphragm seal and is exposed to ambient temperature you may have condensed vapors causing level or density changes in the reference leg.
What is the density of the Halocarbon that you are using? Is it drained and replaced on a regular basis or is it left without checking. Have you tried running it with a dry reference leg with a small drain pot at the bottom that is emptied on a regular basis.
We had a similar problem on a vacuum vessel which was greatly improved by changing to a dry reference leg, also tracing and insulating to stop condensation causing problems.
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
RE: dp dell level measurement
1. As suggested use a diferent type of measurement system, radar/ultrasonic/capacitance that is not affected by the density of the fluid being measured.
2. Use a three point diferential pressure measurement system. The points are, bottom (high), mid, mounted a known distance above the bottom, and vapour space (low). The mid point must remain submerged.
Fluid density is derived from rho=P/g.h where P is the diferential pressure between the bottom and mid sensors and h is height of the mid sensor above the bottom. Tank level is then h=P/rho.g
Cheers
Mark Hutton