FCU 500, FCU 505 · Edition 02.17
37
Valve proving system
Program sequence
The tightness test starts by checking the external pres-
sure switch. If pressure p
Z
> p
u
/2, program A starts.
If pressure p
Z
< p
u
/2, program B starts, see page 38
Program A
Valve V1 opens for the opening time t
L
set in param-
eter 59. V1 closes again. During the measurement
time t
M
, the tightness control checks the pressure p
Z
between the valves.
If pressure p
Z
is less than half the inlet pressure p
u
/2,
valve V2 is leaking.
If pressure p
Z
is greater than half the inlet
pressure p
u
/2, valve V2 is tight. Valve V2 is opened for
the set opening time t
L
. V2 closes again.
During the measurement time t
M
, the tightness control
checks the pressure p
Z
between the valves.
If pressure p
Z
is greater than half the inlet
pressure p
u
/2, valve V1 is leaking.
If pressure p
Z
is less than half the inlet pressure p
u
/2,
valve V1 is tight.
The tightness test can only be performed if pressure p
d
downstream of V2 is around atmospheric pressure.
tL = P59
tM = P56
pZ >
pu
2
+
–
OK
V1
V1
V1
OK
V2
V1
V2
pZ >
pu
2
+
–
tL = P59
tM = P56
V2
V2
tL = P59
tM = P56
+
–
V2 OK
pZ >
pu
2
V1
OK
V1
V2
V2
V2
pZ >
pu
2
+
–
tL = P59
tM = P56
V1
V1
pZ >
pu
2
+
–
PZ
V1
V2
p
z
p
u
/2
Program
A
Program
B
START
▼
