27
Installation and Commissioning
Control Valve with Welding Ends
Control Valve with Welding Ends
Requirement:
The valve housing must be dismantled for welding.
WARNING
Spring tension in the valve
Danger of injury when releasing the hinged clamps (2, 4) as the released spring preten-
sion will suddenly lift the actuator.
Therefore, release the spring tension before detaching the hinged clamps by pres-
surizing the actuator with compressed air at max. 6 or 7 bar (depending on the type
of positioner) or by mechanically adjusting the control cone.
IMPORTANT NOTE
Damage caused by welding
The control valve can be damaged by distortion due to welding and when the position of
the grooves is altered.
Before starting any welding work, remove all built-in parts from the valve.
To ensure that a proper weld is formed when the valve is welded into the pipe, make
sure that the root side of the weld is protected against oxidation by forming gas.
Use welding filler if necessary.
Carry out the following steps:
1.
Release the spring tension.
2.
Remove the valve insert, see chapter “Maintenance“ > “Disassembly“ (page 38).
3.
Weld the housing, without sealing rings, into position as follows, ensuring that the
connection is free of stress.
4.
Fit the housing into place and tack it.
5.
Always close the housing before welding.
6.
Flush the housing with forming gas from the inside to push the oxygen out of the
system.
7.
Weld the housing into the pipe system; use welding filler if necessary. Use the TIG
welding with pulse method.
8.
Passivate the seam after welding.
9.
Fit the seals.
