Installation; Quick-Check; Startup; Valve Maintenance - Flowserve Valtek Mark Six Installation, Operation & Maintenance Instructions Manual

Installation

Mark Six valves with a vented plug should be installed with the extension
and actuator at an angle ≥25° from horizontal. Mark Six valves with
the spring-energized plug seal design may be installed on an angle
<25° from horizontal. For any questions or clarification, please contact
the factory.
1. Before installation, clean the line of all dirt, scale, welding chips and
other foreign material.
2. Check flow direction to be sure the valve is installed correctly. Flow
should be over the plug for fail-closed valves, and under the plug for
fail-open valves. Flow direction is indicated by an arrow on the bonnet
flange.
3. Provide proper overhead clearance above the actuator to allow
for actuator removal and trim inspection, should it be necessary.
Disassembly clearance depends on the length of the cold box
extension and the valve size. To estimate required clearance, add the
length of the extension to the appropriate distance (shown in Table 1)
for the particular valve size.
Table 1: Disassembly clearance (in)

Quick-check

Prior to startup, stroke the control valve. As the instrument
signal is changed, observe the plug position as shown by the
stroke indicator plate.
1. Check for full stroke by making appropriate instrument signal
change (such as 3-15 psi or 4-20mA).
2. Check all air connections for leaks.
3. Evenly tighten packing nuts to 3 to 6 flats over finger-tight.
CAUTION: Do not overtighten packing. This can cause
excessive packing wear and high stem friction, which
may impede stem movement.
4. After valve has been in operation a short time, readjust pack ing to
3 to 6 flats over finger-tight.
5. Stroke valve to make sure that it fails in the right direc tion in case
of air failure, and that the combined actions of the controller,
positioner and valve will provide control of the flow.

Startup

WARNING: On valves with spring-energized seals, it may
take hours or even a day for enough liquefied gas to pass
into the bonnet area to effectively "balance" the pressure
across the plug seal. In the event of air failure in a fail-closed
valve during this time, fluid forces may tend to open the valve
rather than close it because the effective area of the plug seal
is greater than the effective seat area. Once enough vapor
has accumulated in the bonnet area, the pressures on each
VLENIM0006-03 (AQ) July 2019
side of the plug will equalize and normal valve operation
results. Valves with vented designs are available that do not
require time to "balance" the pressure across the plug head.

Valve maintenance

The Valtek Mark Six top-entry design allows for easy trim
inspec tion and service without removing the valve body from
the line or the insulation from the valve to get at the bonnet
and the trim.
Routine maintenance consists of tightening the gland flange
nuts to compensate for packing wear. Do not overtighten
packing nuts, since this will shorten packing life and may
prevent smooth valve performance.

Disassembly and reassembly

WARNING: Depressurize the line to atmospheric pressure and
drain all fluids before working on the valve. Failure to do so
can cause serious injury.
Removing the actuator and plug assembly
1. Fully retract plug until stroke indicator is pointing to the open
position (air to the actuator may be required).
2. Remove the bonnet bolts and lift the actuator, bonnet and plug out
of the valve.
CAUTION: The plug head seals may cause the plug to bind
in the body, making it difficult to remove the actuator/plug
assembly. To remove the plug in this situation, apply air to the
top of the actuator pis ton, moving the actuator cylinder and
bonnet away from the plug head. Place soft (such as wood)
blocking of equal thickness in at least three positions between
the valve body and the bonnet. Apply air underneath the
actuator piston to retract the plug.
3. Lift the plug carefully out of the body. Any scraping of parts while
removing the plug may cause damage. Heavy actuators may
require a hoist. If the actuator is not equipped with a lifting ring, use
lifting straps around the yoke legs.
Disassembling the plug from the actuator
1. Loosen the stem clamp.
2. Loosen the gland flange.
3. Remove the yoke clamp (or yoke bolts if used).
4. Rotate the actuator in a counterclockwise direction to disen gage
the plug stem from the actuator stem.
CAUTION: To avoid scoring guides and stem, do not turn plug
stem in bonnet. Flats are machined on the plug stem so it can
be held with a wrench.
5. Carefully remove plug by pulling it through the bonnet.
6. Push out packing and guides from the bottom of the bonnet, using
a dowel.
7. Inspect guides for scratches and scoring. Damaged guides should
be replaced and new packing should be used upon reassembly.
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