Perform an online zero check while the process is running: 1 Safety & Interlocks, 2 Isolate (Close LP, Open EQ), 3 Zero Trim, 4 Line up (Close EQ, Open LP), 5 Finish. Use the manifold valves to manipulate the pressures safely.
Procedure Map
Hint
1 Safety & Preparation
Before manipulating any valves on a live transmitter, ensure interlocks are bypassed so a zero DP reading doesn’t trip the plant.
2 Isolate for Zero Check
Standard Procedure: Close the LP root valve first, then open the Equalizer valve. Both sides of the transmitter will now see the HP line pressure (static pressure).
3 Check & Trim
The transmitter is equalized at line pressure. The ideal output is 0.0 mbar. Due to static pressure shift or drift, there may be an error.
4 Line Up (Restore)
Reverse the order: Close the Equalizer valve securely, then slowly open the LP root valve. Do not open the LP root while the Equalizer is open, or you will bypass process fluid!
