ARI Armaturen PREDU 700 EN - Manual (Page 10)

Page 2-10 Rev. 0040701000 1714
Operating and installation instructions
PREDU
®
5.2 Requirements at the place of installation
The place of installation should be easily accessible and provide ample space for
maintenance and removing the actuator. Install a stop valve upstream and downstream of
the pressure reducing valve to enable repair and maintenance work, without emptying the
system. A bypass line enables a continuous working by hand. Install manometers upstream
and downstream to control the pressures.
Refer to a system sample under point 5.5 where all valves are shown. The piping before
and after the pressure reducing valve must be dimensioned so that the max. flow speed is
not exceeded, and the pressure reduction should be near to the users.
The nominal diameter of the pipes in front of and behind the pressure reducing valve must
be chosen corresponding to max. allowable flow rates (liquids max. 5 m/s; saturated steam
max. 25 m/s; steam and gases max. 50 m/s). With compressible media (i.e. steam, air) the
downstream piping must be larger because when expanding the volume increase blocks
the flow capacity. The rule 10 x DN is related to the larger downstream piping. When
isolating of the piping, do not isolate the spring room, the actuator, the water seal pot and
the control line.
5.3 Installation instructions concerning actuators
The pressure reducing valve is supplied with mounted actuator.
To alter the pressure range the actuator and spring may have to be changed in the following
sequence:
- Make the system pressureless.
- Remove control piping and empty the water seal pot.
- Loosen lock nut (pos. 30).
- Unscrew actuator away from the valve.
- Relax spring by turning the spring plate (pos. 17).
- Remove sideways pin (pos. 29) and remove the pressure plate (pos. 26), bearing
(pos. 27), spring plate (pos. 28) and spring downwards.
- Remount in the opposite way. The tightning torque for the lock nut is 50 Nm.
- Putting the valve into operation (refer to point 6.0)
-
ATTENTION !
- It is not permitted to mantle / dismantle actuators with valves operating and
service conditions (temperature and pressure) (refer to point 10.0)
-
ATTENTION !
- When disconnecting the control line piping, dangerous media can escape
(hot condensate, steam)!
-
ATTENTION !
- The actuator must be screwed to the end position, then secure with the lock nut
(pos. 30). Reconnect the control line. Do not turn the actuator for a better
position.