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Consider an interface level transmitter as shown below
This section covers how to line up an interface level transmitter .One of the most frequent problem encountered in a plant is that the level transmitters which is installed in the tank or vessel for PCS and ESD level is not matching. There are many reasons to this like parameters mismatching, choking due to slug, heat tracing not working resulting in leading to choking, ripples in the vessel due to suction and filling of vessels using high pressure pumps, different tapping points for ESD and PCS level transmitters, (technology)types of the transmitters used , their response time, sensing element response time failure due to prolonged use, foam in the interface, sudden temperature changes, trapped pressure in the level transmitter chamber, improper line up of transmitters and many more oceans of reasons……….
But line up of transmitter plays a vital role in the reading matching of both ESD and PCS LT
The line connected to the bottom of the tank may be called as HP tapping point because high pressure is experienced compared to other points due to gravity, the middle tapping point can be called as Medium pressure MP point or interface point and the upper tapping point where generally air or gas is present can be called as LP or low pressure point.
To the point, I will describe “Shore Key Line up” method to line up of interface LT
Assume that the interface LT is isolated from the process line
Initially line up the gas point or LP tapping point
Then line up the interface tapping point or MP point and wait for the 3 or 4 minute to settle
Finally after 5 minutes line up the HP tapping point
Allow the process to settle
Wait for more than one hour to settle and to get a stable reading
Follow the same procedure for both ESD and PCS LT
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