Samson 3730 Series - Page 84

84 EB 8389-1S EN
Full stroke test (FST)
The 'Tolerance limit' parameter denes the
permitted valve positions for the start value
and the end value for the step.
The 'Sampling time' denes the time interval
between which the measured values are re-
corded during the test.
Test cancelation conditions
Various cancelation conditions provide addi-
tional protection against the valve slamming
shut or moving past the end position. The
positioner cancels the full stroke test when
one of the following cancelation conditions is
fullled:
− 'Max. test duration': The test is canceled
when the maximum permissible test du-
ration is reached.
− 'Max. breakaway time': The test is can-
celed when the time entered in 'Settling
time before starting test' has elapsed and
the valve has still not changed its posi-
tion. This cancelation condition only be-
comes effective after it has been activat-
ed ("Activate 'Max. breakaway time" =
[Yes]).
Operating point +
Tolerance limit
Operating point –
Tolerance limit
Operating point
Settling time before
starting test
Waiting time after
step change
∆t
decreasing
∆t
increasing
Waiting time after
step change
Settling time before
starting test
Waiting time after
step change
Waiting time after
step change
100
t [s]
x [%]
∆t
decreasing
‘Lower range value’ – ‘Stop’
x ‘Ramp time (decreasing)’
100
∆t
increasing
‘Step start’ – ‘Step end’
x ‘Ramp time (increasing)’
100
Fig. 20: Course of the full stroke test with step response (left) and ramp function (right), fail-close