Electro-hydraulic valves
Dresser-Rand recently introduced its new Gimpel Electro-
Hydraulic Valve or Electro-Hydraulic Trip-Throttle Valves (EHTTV).
Developed to allow users to upgrade latch-type, oil operated
or any other OEM trip or trip-throttle valve without the use of
the shared turbine lube oil system, the EHTTV is a microprocessor
controlled trip-throttle valve, with a self-contained electro-
hydraulic actuator.
Designed specifically for emergency shutdown and throttling
on steam turbines, the EHTTV will have a trip time of 0.3 secs or
less. It incorporates most of the features that are on the current
valves plus the added feature of being independent of the steam
turbine lube oil system.
It is important to note that the Gimpel EHTTV is not designed
to replace the steam turbine governor. The EHTTV will use the
same steam section design as the traditional valves, with a new
electro-hydraulic actuator.
This actuator contains a highly efficient method of pumping
hydraulic fluid from one side of a double acting cylinder to the
other. Once the correct position is reached, the motor shuts off.
Therefore, only minimal power will be required to maintain the
actuator position.
The hydraulic system is controlled by a dedicated
microprocessor contained within a control panel. The control
panel interfaces with an integral motor, which is connected to a
hydraulic pump that will supply the hydraulic pressure to open,
close and exercise the valve.
The EHTTV is controlled by two major components: the
actuator (cylinder, feedback and electro-hydraulic power module)
and the control panel. The actuator is installed on the valve, while
the control panel is mounted remotely. A module and feedback
cables will connect the actuator and control panel.
Pre-programmed software, designed into the controller, allows
Dresser-Rand to set the valve operating parameters by factory-
trained personnel. The standard features that will be supplied on
the EHTTV will be the option to exercise, trip, reset, and throttle.
In addition, the EHTTV has CSA Class I Division 2 area
classification. The steam section is built to ASME/ANSI B 16.34 and
B 16.5 standards and has a SIL-3 Certification from Lloyd’s Register.
The actuator
At the heart of the EHTTV is the electro-hydraulic actuator
(Figure 6). This consists of a motor, gear pump, make-up oil
reservoir, thermostat, and bypass solenoid. The power module
delivers oil to a dual-acting hydraulic cylinder. The actuator’s rated
output is calculated based on a maximum working pressure of
2000 psi. However, the power module will only generate enough
oil pressure to initiate motion to open the valve.
The actuator also contains an integral active feedback
assembly. This assembly contains a position sensor, which will
provide accurate valve position feedback to the control panel.
The feedback assembly is sealed in a NEMA 4X cover and
mounted within or adjacent to the dual acting cylinder. The
connection of the position sensor is by direct mechanical means.
This allows the user to control the valve within
±
0.1% of total
stroke.
The scope of supply for the electro-hydraulic actuator is as
follows:
)
)
Anodised aluminium power module, which requires up to
2000 W (110 VAC or 220 VAC).
)
)
Self-contained lube oil system with a capacity of less than two
quarts of oil.
)
)
Active integral feedback position signal.
)
)
115 VAC or 24VDC integral high-speed solenoid trip valve(s)
with quad solenoid trip systems available for API 612
applications.
)
)
Single or dual-nested springs.
)
)
Carbon steel yoke.
Steam section
The steam section of the EHTTV is designed to the current Gimpel
valve body specifications and available in straight-through, corner-
body and offset globe designs.
The scope of supply for the steam section is as follows:
)
)
Multiple stem orientation options available to meet most
applications.
)
)
ASTMWCB, WC6 or WC9 alloy steel, globe type valve body
with bolted yoke/cover.
)
)
Above and below seat drains.
)
)
Low-pressure and high-pressure leak off connection(s), as
applicable.
)
)
Integral replaceable steam strainer basket.
Figure 4.
Contamination, such as particle or condensate, can
be introduced into the valve’s actuator and cause it to stick
open, resulting in an unsafe condition.
Figure 5.
Dresser-Rand Gimpel
®
latch-type valves.
60
World Pipelines
/
MARCH 2016
