Installation, Operation and Maintenance Manual
MAN712 Rev. 9
June 2021
Working Principle and Detailed Description
Section 5: Working Principle and Detailed Description
25
In any condition, the “Duration” parameter determines the interval of time during which
the ELBS-20 considers the Safety Action as “active”.
The Pressure and the Position values are not updated during the execution of the
Safety Action.
The AO is disabled (0 mA transmission) during the execution of the Safety Action.
After the execution of the Safety Action the ELBS-20 goes to the Slow Sampling Operating
Mode and for exiting from this status it is necessary to “manually” change the operating
mode by using the available interfaces.
(*)
only if the Drop is enabled; “Drop Enabled” = “Yes” (see Section 6).
(**)
the test function forces the valve control (VC) operating mode.
5.1.3
Examples of Pressure Drop Rate Control
The following figure shows the ELBS-20 behavior in presence of a continuous pressure
drop rate.
Figure 12
NOTICE
Before than the valve control action takes place, it needs that the EVENT 6 condition is
confirmed during the “Delay time”.
Start of the
Safety Action
Safety Action considered as “active”
t0 - “Duration”
time
tm (second)
= ((((Pres. Max/VLC PDR)*60)/200)/S.Rate +1)*S.Rate
delay (# of Samples)
= 4 Samples
t_del (second)
= 4 * S.Rate
t_dur (second)
= Duration
*Pressure
drop greater
than set-point
EVENT6
Sampling rate
(S.Rate)
Valve
control mode,
no alarm
Time
t0-tm
Present time
t0
Time
t0+t_del
Time
t0+t_del+t_dur
Slow sampling
rate
Time
Pressure
curve
Safety Action
Measuring time
of pressure drop
t_del (Delay time)
t_dur
(Solenoid control duration)
t0
