Samson 3760, Mounting And Operating Instructions

Page: 13 / 36

3 Connections
3.1 Pneumatic connections
The pneumatic connections are designed as
1
8
-18 NPT or ISO 228/1-G
1
8
tapped holes.
The supply input (SUPPLY 9) is fitted with a
filter to clean impure air. The filter is fixed
on a support and can be removed using a
screwdriver for cleaning or replacement, if
necessary (filter order no. 1400-6897).
The customary male fittings for metal and
copper pipes or plastic hoses can be used.
Note: The supply air must be dry and free of
oil and dust.
Observe maintenance instructions of up-
stream pressure reducing stations.
Thoroughly blow out all air lines before con-
nection.
3.1.1 Signal pressure indication
To precisely adjust the positioner, we recom-
mend attaching a pressure gauge to the
positioner to measure the signal pressure
(OUTPUT 36).
The attachment kit is listed in the accessories
table on page 12.
3.1.2 Supply pressure
The required supply pressure depends on
the bench range and the direction of action
(fail-safe action) of the actuator.
The bench range is indicated as spring
range or signal pressure range on the
nameplate; the direction of action is speci-
fied by a symbol.
Actuator stem extends:
Fail-safe action "valve CLOSED"
(with globe and angle valves)
Required supply pressure = upper bench
range value + 0.2 bar, at least 1.4 bar.
Actuator stem retracts:
Fail-safe action "valve OPEN"
(with globe and angle valves)
The required supply pressure for tight-clos-
ing valves is roughly calculated from the
equation for the maximum signal pressure
pst
max
:
pst
max
= F +
d p
4 A
2
×p × D
×
bar
d = seat diameter [cm]
D p = differential pressure at the valve [bar]
A = effective diaphragm area [cm²]
F
= upper bench range value of the
actuator
If no values are specified, calculate as fol-
lows:
Required supply pressure = upper bench
range value + 1 bar
3.1.3 Degree of protection IP 65
To increase the degree of protection from
IP 54 to IP 65, replace the vent plug on the
actuator casing with the filter check valve
(accessories). For details, see Fig. 2.
EB 8385 EN
13
Connections