Samson 2780-1, Mounting And Operating Instructions, Page: 15 / 52

EB 5840 EN 3-3
Design and principle of operation
pressure connection of the connecting plate
to the actuator diaphragm chamber.
The connecting plate needs to be turned to
align the correct symbol for the fail‑safe ac‑
tion with the marking.
3.3 Fail-safe action
When the signal pressure is reduced or the
control signal fails, the fail‑safe position of
the control valve depends on whether the
springs are installed in the top or bottom di‑
aphragm chamber.
The listed fail‑safe actions apply to
SAMSON globe valves.
Note
Actuator stem extends
Left
attachment
Right
attachment
Actuator stem
extends retracts
Actuator stem retracts
Left
attachment
Right
attachment
Signal pressure input
(left attachment)
Connecting plate Switchover plate
Symbol
Marking for
signal pressure
input
Signal pressure input
(right attachment)
Signal pressure
connection
Fig. 3-3: Signal pressure connection over switchover plate or connecting plate in Type 2780‑2