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WHAT IS IT?
This is a proportional flow control valve operated by a linear proportional SERVOID® driver. The driver is used to regulate a variable orifice which controls flow to the outlet port. By infinitely varying the orifice size, the flow can be regulated throughout the full range from minimal flow up to maximum rated flow. |
The SERVOID® driver is the "intelligent" portion of this assembly, enabling the valve to provide infinite variability. The proven SERVOID® technology offers precise control and repeatability throughout its range, while simultaneously providing extraordinarily linear output. The valve is useful for a wide range of viscosities and fluids due to the knife edge variable orifice.
HOW DOES IT WORK? This valve is driven by a SERVOID® driver, our name for a DC linear proportional solenoid. This driver is an electromagnetic device, converting a current input to a linear motion output. The SERVOID® is designed to provide linearity of + or - 4% F.S. in the output position when compared with the electrical input signal. The total moving mass of the armature assembly is approximately 7 grams and is supported by springs with a total mechanical spring rate of 600 pounds per inch. With this stiffness, minimal shift in control set point is expected even under heavy acceleration conditions. This valve is configured to use a 35 ohm coil and operate to 100% rated flow capacity at 600 milliamps. Alternate coil resistance and current requirements are possible, although power requirements will remain in the 10 to 12 watt range. The coil is dry, electrically isolated and epoxy encapsulated.
The armature of the SERVOID® driver operates and positions a pilot actuated spool, which is an integral part of the poppet type metering orifice. The spool moves to track the armature position. The effective servo gain is near 60,000 PSI/inch and the effective servo spring rate for the spool is approximately 40,000 pounds/inch. The net available "chip shear" force acting on the servo spool is approximately 36 pounds opening and 30 pounds closing. Linear output of the driver armature translates to linear spool positioning and area control of the main flow port. For a constant regulated delta-p across the valve, the resulting performance is linear flow control versus input current.
All wetted areas within the assembly are either stainless steel or nickel plated, providing compatibility with a variety of fluids. Offset adjustment is possible to provide a given flow value at zero electrical signal or shutoff and minimal leakage under the same electrical conditions, depending on application requirements. The gain is also factory adjustable to provide a control range to match the application. |
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HOW IS IT USED?
This proportional flow control valve may be used to control a variety of both liquid and gaseous fluids. The particular configuration shown here is a liquid configuration which might be used to precisely control the flow of either hot or cold fluid in a cooling system. Another successful application would have this valve regulating the flow of fuel to a turbine engine from extremely low flow values up to about 7,000 pph. With a turn down ratio in excess of 500 to 1, the valve provides smooth control during startup and idle with capacity for responsive performance up through full flow rating of the valve.
The SERVOID® can be equipped with customer specified electrical connectors in addition to the pigtails shown. This valve offers optimum performance where precise flow control is needed throughout the range from minimal flow through the higher flow capacities possible here. |
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