Installation, Operation and Maintenance Manual
MAN712 Rev. 9
June 2021
Working Principle and Detailed Description
Section 5: Working Principle and Detailed Description
23
5.1.2
Details of the Valve Control Operating Mode
5.1.2.1
Safety Action on Pressure Drop Rate
When "Drop Enabled" = "Yes" (see Section 6) and the pressure drop rate exceeds the
"Valve Control Pressure Drop Rate" (EVENT 6), the ELBS-20 c)ommands the selected
SOV Control Outputs and the actuator strokes the line valve to the fail-safe position.
5.1.2.2
Safety Action on High or Low Pressure
When the pressure value is lower than the “Low Pressure Limit” (EVENT 2), or is higher than
the “High Pressure Limit” (EVENT 4), the ELBS-20 commands the selected SOV Control
Outputs and the actuator strokes the line valve to the fail-safe position.
5.1.2.3
Safety Action for Simulation Test (Pressure Drop)
The ELBS-20 provides a Self-Test routine (see 6) that allows entering a pressure drop rate in
place of the pressure transducer value, in order to verify the output command signal to the
solenoid valve and the correct operation of the device.
The test function forces the valve control (VC) operating mode. The simulated pressure will
start to the high pressure limit or to the Pressure Max. (if the high pressure limit is greater
than the Pressure Max.) and goes to 0 bar according with the set pressure drop
(“T.Pr.Drop”). The test function can be stopped by pressing the ENTER push button.
If the condition of EVENT 2 or EVENT 6 (*) are reached or if the Pressure value becomes 0.0
bar, the Safety Action is performed and the test is finished.
The event generated during the Self-Test routine is not stored.
At the end of the test (both if interrupted and if Safety Action is performed) the ELBS-20
goes to the SLOW operating mode.
(*) The Drop must be enabled. “Drop Enabled” = “Yes” (see Section 6).
5.1.2.4
Safety Action for Simulation Test (Safety Action)
The ELBS-20 provides a routine for forcing the Safety Action, in order to verify the output
command signal to the SOVs or to perform a “manual” Safety Action.
This test can be performed only if the operating mode of the ELBS-20 is VC or VC+ACQ.
This command performs a Safety Action and at the end of its operation the ELBS-20 goes to
the SLOW operating mode.
5.1.2.5
Safety Action for Digital Input Command
The ELBS-20 provides a dedicated function of the Digital Inputs (DI) to perform the Safety
Action through a hard-wired command.
This command performs a Safety Action and at the end of its operation the ELBS-20 goes to
the SLOW operating mode (see Section 6.3).
