Web POLL results: Level with me

Level With Me: Why do your problem level applications give you fits?

1. The application was poorly designed:  34.15%
2. The fluid/solid is very hard to measure:  25.61%
3. The process upsets are very fast and level changes too quickly:  15.85%
4. The measurement technology we use gives bad readings:  14.63%
5. The meter is too high-maintenance to keep going:  9.76%

Which level devices give you the most problems?

1. Differential pressure (DP) sensors:  25.61%
2. Bubbler-type sensors:  18.29%
3. Ultrasonic-type sensors:  23.17%
4. Mechanical-type:  17.07%
5. Radar-type sensors:  4.88%
6. Other:  10.98%

• Most sensors cannot detect foam levels and therefore fail. Once the foam touches the sensors it gives the impression that the tank is always full.
• Our biggest problems come in startup of the refrigeration system and attempting to regulate the level of refrigerant in the low-pressure receiver. During startup the refrigerant changes state rapidly from liquid to gas resulting in instantaneous changes of 25 in. in a 35-in. tank. We’re finally at the point of simply ignoring the level during startup.
• We have used displacers and DP transmitters for level for years, with varying results., However, we now preferentially use TDR (GWR) level devices and problems are fewer and measurement more reliable.
• The LP and HP legs in DP type level measurement systems become empty and we have to manually fill the fluid whose level is to be measured. A special T assembly has also to be made. IF such an application is used in vacuum service then even a slight leakage leads to the emptying of a leg.