๐ Scope of Application
This procedure applies to the safe operation of differential or pressure transmitters equipped with a 3-valve manifold (comprising a High-Pressure Valve [H], Low-Pressure Valve [L], and Balance Valve [B]). Correct sequencing is essential to prevent diaphragm damage and ensure accurate pressure readings.
โ๏ธ Fundamental Principle
Always protect the transmitter by using the balance valve to equalize pressure before applying or removing process pressure.
Never expose the diaphragm to sudden unidirectional overpressure!
โ Start-Up Procedure (Commissioning)
๐ Initial State
High-Pressure Valve (H): Closed
Low-Pressure Valve (L): Closed
Balance Valve (B): Open โ Equal pressure in both pressure chambers of the transmitter
๐ง Step-by-Step Instructions
Open the Low-Pressure Valve (L)
Close the Balance Valve (B)
Open the High-Pressure Valve (H)
๐ Operation Mnemonic
Open L โ Close B โ Open H
โ Shutdown Procedure (Decommissioning)
๐ง Step-by-Step Instructions
Close the High-Pressure Valve (H)
Open the Balance Valve (B)
Close the Low-Pressure Valve (L)
๐ Operation Mnemonic
Close H โ Open B โ Close L
๐ Final State
High-Pressure Valve (H): Closed
Low-Pressure Valve (L): Closed
Balance Valve (B): Open โ The transmitter is safely isolated and pressure-balanced
โ Key Safety Notes
โ ๏ธ Perform All Operations Slowly
Sudden opening or closing of valves can cause pressure spikes, which may rupture the diaphragm inside the transmitter.
โ๏ธ Balance Valve Is Critical
During Start-Up:
Open L before closing B โ Avoid high-pressure shock to the low-pressure chamber
During Shutdown:
Close H before opening B โ Prevent residual pressure from damaging the system
๐งช Handling Hazardous Media
For steam or corrosive fluids:
Depressurize first and wear proper personal protective equipment (PPE)
For crystallizing media:
Flush the impulse lines after shutdown to prevent clogging
๐ง Summary of Mnemonics
| Procedure | Sequence (Mnemonic) |
|---|---|
| Start-Up | Open L โ Close B โ Open H |
| Shutdown | Close H โ Open B โ Close L |
๐ We recommend posting this mnemonic chart near the transmitter for quick reference and safer operation.