
EB 3003 EN 3-1
Design and principle of operation
3 Design and principle of oper-
ation
ÎSeeFig.3-1andFig.3-2
The differential pressure regulators are de-
signed to maintain the differential pressure
between the high-pressure and low-pressure
linestoadenedsetpoint.
Type42-24·Thesetpointcanbeadjusted
as required within the set point range.
Type42-28·Thesetpointisxed.
The regulators basically consist of the
Type2422Valvewithseat(2)andplug(3)
andaclosingactuator(Type2424orType
2428) with an operating diaphragm (13).
Valve and actuator are delivered separately
and must be assembled on site using a cou-
pling nut (11).
Themediumowsthroughtheareareleased
between the plug (3) and seat (2) in the di-
rection indicated by the arrow. The position
of the valve plug determines the differential
pressure prevailing across the plant.
ThestandardType2422Valveispressure-
balanced. The forces acting on the valve plug
created by the upstream and downstream
pressures are balanced by a balancing
bellows (5) or balancing diaphragm 1) (5.1).
Regulators balanced by a bellows or a dia-
phragm only differ in the pressure balancing
principle applied. Valves balanced by a dia-
phragm have a balancing diaphragm (5.1)
instead of the balancing bellows (5). The
downstream pressure p2acts on the bottom
of the diaphragm and the upstream pressure
p1on the top of the diaphragm. As a result,
the forces created by the upstream and
downstream pressures acting on the plug are
balanced out.
The differential pressure across the plant is
transmitted over the high pressure and low
pressure lines to the operating diaphragm
(13) where it is converted into a positioning
force. This force moves the plug according to
the force of the set point springs (16).
The set point springs are mounted inside the
actuatorforaxedsetpoint(Type42-28).
The set point springs can be adjusted exter-
nallyforanadjustablesetpoint(Type42-
24).
Control lines (20) mounted on site transfer
the high pressure and low pressure in all ver-
sions.
Type2424andType2428Actuatorsare
equipped with an overload protection (21). It
prevents a rise in differential pressure during
extreme operating conditions (e.g. vacuum
at the heat exchanger) by opening an inter-
nal excess pressure limiter. As a result, plants
and the regulator itself are protected against
excessively high differential pressures.
1) Type2422Valve,balancedbyadiaphragm,
DN65to250only