8 | Baker Hughes
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4. Operation
Ensure that operators and fitters are fully trained and familiar
with the procedures to be undertaken. For both electrical and
pneumatic equipment ensure the operator has carefully read the
manufacturer’s instructions.
Never on valves that employ a manual override, shaft mounted
de-clutchable gearbox, engage the gearbox with the valve on
automatic control. The handwheel must be disengaged prior to
the unit being operated under its automatic condition.
Unless the valve is specifically designed for fast operation, valves
should be operated slowly to avoid thermal and mechanical
shocks.
Never use the Mounting Box to support an Actuator; the Mounting
Box is designed to transfer torque through the drive chain not to
fully support the weight of an overhanging Actuator.
Always ensure Actuation is fully supported on installation and
once in position.
Note: The High-Performance Triple Offset Butterfly Valve is
a ‘Torque Seated’ design. To operate the valve effectively
torque must be applied throughout the drive chain to the
sealing components (explanation: effectively the valve is
trying to over-close)
To adequately achieve closure, a Masoneilan Valve requires;
A minimum of ‘5° over-travel’ to be incorporated into the operator
design.
The drive-chain must be rigid through the use of dowel pins or a
calculated bolting sequence.
Sealing components must not be adjusted or removed without
authorization from Baker Hughes in writing. To do so will
invalidate any warranty. Never remove the valve obturator when
the valve is under pressure or in service.
Masoneilan Valve Triple Offset Butterfly Valves are quarter turn
operational valves. Valve users must ensure actuation is set to
prevent the valve from opening past 90 degrees.
Baker Hughes will supply the effective torques required to seal
the Masoneilan valve and MAST / MAVIT figures on request.
Never remove the valve actuation or gearbox when the valve is
under pressure or in service.
The function of a butterfly valve is to isolate or regulate flow.
The closing mechanism takes the form of a disc which allows
for quick shut off. Butterfly valves are generally favored because
they are lighter in weight, meaning less support is required.
The disc is positioned in the center of the pipe, passing through
the disc is a shaft connected to an actuator on the outside of
the valve. Rotating the actuator turns the disc either parallel or
perpendicular to the flow. The disc is always present within the
flow; therefore, a pressure drop is always induced in the flow,
regardless of valve position.
The offset position of the disc increases the valve’s sealing ability
and decreases its tendency to wear. The triple offset butterfly
valve makes use of a metal seat and is therefore well suited to
withstand higher pressure.
Operating specifications such as temperature and pressure are
based on design and material choice.
Valves are manufactured to the Customer’s requirements and
operating parameters; manual or automated and defined in an
order specific Quality Design Plan.
5. Overhaul and
Refurbishment
The ability to undertake valve overhaul and refurbishment will be
hindered by the restraints of the valve repair facilities and tooling
at site of installation. Masoneilan Valve offers a return service.
It is strongly recommended that the services of Masoneilan
Valve be sought for valve overhaul and refurbishment where full
engineering capability and access to specialist equipment exist.
If repair and refurbishment is to be undertaken at site by the
end user, reference should be made to the Technical Instruction
specific to the Butterfly valve type being repaired.
Only genuine Masoneilan Valve spares should be used. All
Masoneilan Valve, valves are identified with a valve serial
number. This serial number should be quoted with any technical
query, spare parts or service inquiry.
For free refurbishment / overhaul quotations please contact
6. Functional Safety
The Safety Function of the valve is to move the disc to a
predefined safe position upon a demand (manual or automated).
The safe position can be to close or open.
Normal operation under a no fault condition where the valve is to
close rather than open (or vice versa) it will behave as follows:
•
The valve will be open allowing the process to flow
•
Demand (manual or automated) is given to close the disc
and isolate the process
•
Shaft rotates
•
Disc rotates with the shaft 90° until flush with the disc seat
•
The valve is now fully sealed by the disc and the process
is isolated
