Reduce Shrinkage And Accidental Spills

Hydrostatic level measurement continues to be the most commonly used principle for level measurement in the food and beverage industry. However, it is important to understand the capabilities and limitations.

Hydrostatic level sensors work on the principle of measuring the pressure exerted by the column of liquid above the sensor membrane, usually expressed in inches of water column (pressure = height x density). Many times the influence of density is forgotten leading to measurement errors or overspill situations. Temperature fluctuations not only can cause density variations but can also result in zero point error of the level transmitter, which is often seen after CIP when the sensor is heated up.

For smaller balance tanks the temperature effects on the sensor can be very visible and lead to overspills, or cause air to be sucked into the system if the transmitter is not capable of quickly compensating for rapid temperature swings. In large tanks and silos the temperature effect after CIP usually prevents the use of the silo until the sensor has cooled down and show empty tank. If the transmitter zero point is adjusted while hot, it will likely show empty tank while these is still product in the tank, causing unnecessary product loss.

Many hydrostatic level sensors are also damaged during manual cleaning of thanks or due to mishandling during calibration: the thin membrane is easily deformed or pierced.

The solution
Installing other technologies such as load cells, capacitance, radar or other principles may be an option, but usually this involves major changes in the tank. An easier way is to use the Endress+Hauser Deltapilot S FMB70, which has been developed specifically for these applications. Utilizing a specially developed sensor with advanced temperature compensation and extra thick membrane, the FM70 is suitable for balance tanks with measuring span down r" H20 and ranges up to 150 psi for large silos and pressure applications. The FMB70 is available with all common. Process connections including Tri-Clamp® and Anderson style flush weld connections.

SOURCE: Endress+Hauser, Inc.