Samson foundation 3787, Mounting And Operating Instructions, Page: 25 / 96

3.1.2 Supply air pressure
The required supply air pressure depends
on the bench range and the operating direc-
tion (fail-safe position) of the actuator.
The bench range is mentioned on the name-
plate as spring range or signal pressure
range.
Actuator stem extends:
Required supply air pressure =
Upper bench range value + 0.2 bar,
min. 1.4 bar.
Actuator stem retracts:
The required supply air pressure for tight-
closing valves is calculated from the maxi-
mum signal pressure pst
max
pst
max
= F +
d 2
⋅ π ⋅ ∆
p
4
⋅
A
[bar]
d = Seat diameter [cm]
∆
p = Differential pressure across the valve [bar]
A = Actuator area [cm
2
]
F = Upper bench range value of the actuator [bar]
If there are no specifications, calculate as
follows:
Required supply air pressure = Upper
bench range value + 1 bar
3.2 Electrical connections
For electrical installation, you are re-
quired to observe the relevant elec-
trotechnical regulations and the acci-
dent prevention regulations that
apply in the country of use. In Ger-
many, these are the VDE regulations
and the accident prevention regula-
tions of the employers’ liability insur-
ance association.
The following standards apply for in-
stallation in hazardous areas:
EN 60079-14: 2003 (VDE 0165
Part 1)
"Electrical apparatus for ex-
plosive gas atmospheres" and
EN 50281-1-2: 1999 (VDE 0165
Part 2)
"Electrical apparatus for use
in the presence of combustible
dust"
.
For the interconnection of intrinsi-
cally safe electrical equipment, the
permissible maximum values speci-
fied in the EC type examination certi-
ficate apply (U
i
or U
0
; I
i
or I
0
; P
i
or
P
0
; C
i
or C
0
, and L
i
or L
0
).
For EEx nA equipment (non-spark-
ing apparatus), the standard
EN 50021: 1999 specifies that con-
necting, interrupting, or switching
circuits while energized is only
allowed during installation, mainten-
ance or repair work.
For EEx nL equipment (energy-
limited apparatus), the standard
EN 50021: 1999 allows this type of
equipment to be switched under nor-
mal operating conditions.
EB 8383-1 EN
25
Connections