The pitot tube is used were required to measure the velocity of a fluid. It is widely used in aircraft for measurement of the speed. In-plant it is used for measurement of flow rate by calculating the velocity of the gas.
Here in this article, we will discuss the calibration of the pitot tube.
Below is schematic of the pitot tube. For the sake of the explanation, I have considered a transmitter at bottom side.
Follow the below step for successful calibration :
1. First, tell personnel in the control room to put a loop in manual mode and put in Maintenance Override Switch.
2. isolate process using isolation valve.
3. Drain the process using drain valve.
4. Remove the connection of the manifold after releasing pressure and connect pressure calibrator to HP side and keep LP side open to atmosphere.
5. Connect HART and check value like LRV, URV, Tag no., etc.
6. connect a multimeter in series with the signal to measure the mA.
7. Apply pressure as per measuring range we require for LRV and check corresponding mA. If there is an error then adjust zero using HART.
8. Apply high pressure as per URV and check corresponding mA. If there is an error then adjust span using HART.
9. Check the linearity in ascending and descending order at a different point (0%, 25%, 50%, 75%, 100%).
10. If a large error exists then trim the input or output as required.
11. Do connect transmitter again, ask operator to put loop back in auto mode.
(NOTE: BEFORE REMOVE TRANSMITTER FROM THE PROCESS MAKE SURE TO RELEASE PRESSURE, ISOLATE THE VALVE AND DRAIN THE PROCESS.)