)
)
Nitride valve stem/steam bushings.
)
)
Stellite seating contact surfaces.
)
)
Chrome moly steel valve seat and disc.
)
)
Corrosion-resistant materials for outdoor installation.
Control
Included with the EHTTV is a control module/panel. This
control panel contains a microprocessor that has a low dead-
band, with immediate response and a modulating duty cycle.
Four contact features are included on the front of the
control panel, which allows the EHTTV to exercise, trip, reset,
and throttle.
The EHTTV allows the user to ‘exercise the valve,’ or the
process of partially stroking the valve to verify movement
of the critical sliding parts in the EHTTV. Exercising can be
performed during valve operation without affecting the full
load steam supply to the steam turbine. Remote actuation of
the exerciser is available, as an option.
A local trip feature on the EHTTV can be used to trip
the valve offline. The trip feature signals the valve to trip, by
de-energising the solenoids, and is designed trip closed in
0.3 secs or less when the valve is signalled to close.
The reset feature allows the user to reset the EHTTV after
it has been tripped. The EHTTV cannot be reopened after a trip
event until the reset feature has been triggered.
A throttling feature in the EHTTV gives the user a choice of
local (manual) or remote throttling of the valve.
Figure 6.
Electro-hydraulic actuator.
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Conclusion
Dresser-Rand’s Gimpel steam turbine protection valves handle a
wide range of applications and are in operation in petrochemical
facilities and power plants around the world. In addition, Gimpel
valves are used for US Navy steam turbine applications, including
main propulsion, turbine-generator, and main feed pump services.
Beginning with the first nuclear powered submarine Nautlilus, Gimpel
valves have been in operation and protected steam turbines on every
US Navy nuclear powered submarine and aircraft carrier including the
CVN 76 Ronald Reagan and the CVN 77.
Since the trip throttle valve is the ‘heart’ of the turbomachinery
protection system, proper maintenance and service procedures are
essential for reliable operation. Dresser-Rand’s worldwide network of
approved service centres all follow the same strict procedures and
quality standards to ensure that valves returned to site are inspected,
tested, rebuilt, and functionally restored to ‘as new’ condition.
