Woodward 3171A, Руководство по эксплуатации продукта, Страница: 11 / 47

Manual 26731 EM35MR1/3171A Gas Valve
Woodward 1
Chapter 1.
General Information
Introduction
The EM35MR1/3171A gas valve is designed for metering gaseous fuel to
industrial gas turbine engines. The EM35MR1 electric actuator is used to drive a
3171A gas valve, closed loop to position demand. Position feedback is provided
by a resolver connected to the valve metering sleeve. Closed loop position
control is accomplished through an EM 24 V Digital Driver. Having the feedback
on the valve allows the motor assembly to be repaired or changed in the field
without the loss of valve calibration.
3171A Gas Valve
The 3171A Gas Valve is a stainless steel valve capable of metering gas flow
between 25 and 20 000 pph (11 and 9072 kg/h). The valve is designed to bolt
into a 1 inch (25.4 mm) line by means of 0.625-11 UNC 2B tapped holes. The
valve inlet and outlet flanges are class 600 per ANSI B16.5. The valve design is
a rotary metering sleeve and a shoe-type throttling valve. The valve shoe is
spring and pressure loaded against the metering port to minimize leakage and to
self-clean the metering port. Metering port area is determined by input shaft
positioning from the actuator. The valve has an internal spring to return the valve
to the minimum fuel position in the event of a power loss to the actuator.
The 3171A valve has redundant seals on all dynamic sealing surfaces. Between
these two seals is an overboard vent which vents any gasses that may leak past
the first seal to safe vent location. The use of an inner-seal vent prevents the
second dynamic seal from seeing any differential pressure and thus offers
protection against the leakage of gasses from the valve into the surrounding
ambient atmosphere.
The valve design incorporates an inlet guide tube to condition the inlet flow and
to direct any gas contaminants through the metering port, minimizing any
accumulation in the valve housing. The metering sleeve support bearings are
positively sealed from the gas. Internal valve parts are made of through-
hardened stainless steel.
The valve has mechanical stop screws installed in the valve flange.
These stops must not be adjusted by the customer. If these stops
interfere with the valve operating region or the electrical stops, it will
cause the EM 24 V Digital Driver to trip out on overcurrent.