Samson 2357-3, Mounting And Operating Instructions, Page: 14 / 40

14 EB 2559 EN
Design and principle of operation
3 Design and principle of oper-
ation
See Fig. 2.
The regulator consists of a valve with three
ports (A, B and C), a spring-loaded operat
-
ing bellows (3) with set point adjuster (10)
and a tubular plug (2.2).
The process medium flows from port A to
port B in the Type 2357-3 Pressure Regulator
used as a build-up pressure regulator with
safety function.
The regulator is open when relieved of pres
-
sure. The pressure downstream of the regula -
tor is transmitted to the operating diaphragm
(3). The positioning force produced by this
pressure moves the pressure build-up plug
(2.1), which is firmly attached to the plug
sleeve, depending on the spring force adjust
-
able at the set point adjuster (10). The regu -
lator closes as soon as the downstream pres -
sure has assumed the adjusted set point.
Functioning as a pressure build-up regulator,
the regulator also operates as a safety valve
for the pressure chamber upstream of port
A. When the pressure rises above the set
point by approx. 5 bar, the positioning force
overcomes the force of the closing spring
(16), causing the pressure build-up plug
(2.1) to open and the pressure is relieved to
ports B and C.
Functioning as an excess pressure valve, the
medium flows from port B to C. The tubular
plug seals off the operating bellows when
there is no pressure drop across port B and
C. The pressure at port B acts on the operat
-
ing bellows (3). The positioning force pro -
duced by this pressure opposes the adjust -
able spring force of the set point spring (8)
and opens the tubular plug (2.2) when the
pressure rises above the set point by approx.
0.5 bar. The pressures are equalized and the
medium escapes through the inside of the tu
-
bular plug over port C.
As an excess pressure valve, the regulator
can be optionally equipped with a non-re
-
turn unit (12). It prevents the medium from
flowing back to port C and allows mainte
-
nance work to be performed on the regula -
tor without having to empty the tank first.
EC type examination
An EC type examination according to the
Pressure Equipment Directive 97/23/EC,
Module B has been performed on the regu
-
lators.