4 | Baker Hughes
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Actuator may be pre-loaded with tension from air pressure
or springs. Prior to disconnecting instrumentation read
all instructions for the specific actuator.
Heat Insulation
In case of a heat-insulated installation, do not insulate the valve
bonnet and take protective measures relative to personal safety.
Hydrostatic Testing and Line Cleaning
During this operation, the control valve must not be used as
an isolating valve. This means that the valve must always be
opened before carrying out pressure tests in the process line,
cleaning of pipes, etc. Otherwise equipment damage or failure
of the seal rings could result. Flushing and hydrostatic test
equipment can be purchased from the Masoneilan factory.
Flow Direction
The valve must be installed so that the process fluid will flow
through the valve in the direction indicated by the flow arrow
located on the body.
Welded Connections
Disassembly
Valve Actuation
Access to the internal components of the valve should be
accomplished with the actuator removed. Follow the detailed
instructions below and refer to the appropriate actuator
instruction manuals.
Disconnect Instrumentation
Disconnect all mechanical connections between the positioner
and the other instruments. Disassemble the valve stem and
actuator stem coupling as described in the following sections.
Air-to-Retract Actuators
Apply sufficient air pressure to the actuator to retract the stem
completely. Disconnect the plug stem from the actuator stem
depending on the connection type as described below.
Threaded Connection
Unscrew the plug stem from the actuator stem, making sure the
plug never contacts the seating area (liner or seat ring) at any
time during disassembly.
Split Clamp Connection
Remove the screws and disassemble the stem connector from
the valve and actuator stem.
Air-to-Extend Actuators
For this actuator configuration, the valve plug is already in
the fully retracted position without any air pressure applied.
Disconnect the plug stem and actuator stem as described in
the threaded connection and stem connector sections above
depending on the connection type.
Actuator Removal
Disconnect all electrical and air connections to and from the
actuator. Disassemble yoke nut or yoke attachment screws or
bolted connections, and lift the actuator off of the valve being
careful not to damage the bonnet threads.
Pre-Weld Preparation
Carefully follow the installation steps defined in the sections
noted below prior to performing weld procedures.
Welding Process
Perform welding process in accordance with the standard
requirements for the materials and weld construction of the
specific valve. Apply post weld heat treatment if required.
Post Weld Cleaning and Assembly
Inspect the body, bonnet, and trim components for cleanliness
and surface condition. Remove any foreign materials, such
as weld chips, slag or scale. Make sure there are no nicks,
scratches, burrs or sharp corners on sealing and sliding
surfaces. Clean all gasket interface surfaces and reassemble
using new gaskets to ensure sealing integrity.
Actuator Assembly
Assemble the pneumatic actuator onto the control valve using
the appropriate instructions for the specific actuator model and
type. Connect air pressure lines to the actuator ports to meet
intended operating mode (i.e., air-to-extend, air-to-retract, or
double-acting).
Carefully review the information in this section prior
to welding any valves inline. Refer any additional
questions to the local Baker Hughes Sales Office or
Service Center.
Internal valve components should be removed prior
to performing any post weld heat treatment in order
to prevent damaging any soft goods (such as teflon
®
seals). If unable to remove the elastomeric components,
then other methods must be employed to prevent the
local temperature around the seals from exceeding the
maximum material limits (typically 450°F / 232°C for
teflon based materials).
Contact between the plug and seating area during this
disassembly process may cause damage to the seating
surfaces. It may be necessary to disassemble the actuator
yoke from the valve bonnet and lifting the actuator off the
valve to avoid plug to seating surface contact.
Prior to performing any maintenance on the valve,
isolate the valve and vent the process pressure.
