Weir type flow meters are used to measure open channel flow where the level of the channel is measured against a weir opening.
The flow meter is based on gravitational impact of an open weir. If the rate of flow exiting the weir is same as the flow entering the system, the level will remain constant
Ultrasonic and bubbler type flow meters are typically used for measuring the height of the weir level
If ultrasonic level measurement is used, typically, a PVC pipe will be provided to minimize false echos
The wet leg measured DP is 0 at full and negative at empty vessel
The wet leg manifold does not have any equalizing valve to eliminate the effect of valve parsing. A parsing equalizing valve would cause the low side filled product to drop down, reducing the low side pressure. If this occurs, we would expect a higher DP (high minus low) and would of course result in a higher level measurement
To verify 100% level i.e. 0 dp, vent both high side and low side manifolds
To verify 0% level i.e. lowest dp (negative), vent high side manifold first. Then, the lowside must me vented at the top tapping point. By this way you measure atmospheric pressure at high side and wet leg pressure at low side. This low dp should be equal to the LRV
Some transmitters allow the setting of 0% level at 0 dp and 100% level at made-positive lowest dp. This is done be adding an offset or zero
Open-Plant is a revolutionary Industrial IOT Platform software, used to create and deploy Industrial IT apps/solutions. It is an all-encompassing solution offering both back-end and front-end components i.e. the full stack. From our user's experience, creating and deploying Industrial IT apps became 10x faster and 10x less cost. We serve the mining, energy, oil & gas, construction and manufacturing industry.