Hydraulic Servovalve

The company offers a single-stage hydraulic servovalve for safe operation in hazardous environments such as those permeated by explosive gases that could ignite if unwanted sparks occur. Explosion-proof applications of the valve include closed-loop control of actuators used in industrial turbines and machinery for oil, gas, chemical, and food processing.

The ruggedly built valve, designated Model 27S R-DDV servovalve, is a 4-way flow control valve available with six rated flows ranging from 0.5 gpm up to 10.5 gpm at 1000 psi. Maximum supply pressure is 4000 psi. Various bipolar voltages and current inputs, and a 4-20 mA input, provide additional flexibility for tailoring the valve to a wide range of applications. Frequency response is a fast, 150-Hz for excellent positional and motion resolution.

A typical explosion-proof servovalve application is positioning of the variable guide vanes that control an industrial turbine. Industrial turbines usually drive electrical generators. As the electrical load is turned on and off, the turbine tends to change speed and lose efficiency. These effects are minimized by an effective variable-guide-vane system.

The servovalve includes a heavy-duty stainless-steel cover for the motor and electronic controller. The cover threads onto the valve body, and two clamps then provide secondary retention of the cover. Electrical conductors connect to the valve through a threaded valve port. This permits the use of electrical conduit, which maintains the explosion-proof rating of the installation.

The European Committee has granted hazardous environment certifications to Model 27S for Electromechanical Standardization (CENELEC) and the Canadian Standards Association (CSA). It also meets CSA/CENELEC standards for approved electrical noise and interference limits. It is rated dust-tight and capable of operation when sprayed with water jets.

In addition to Model 27S, the R-DDV Rotary-Direct Drive Servovalve line includes Model 27C hydraulic servovalve and Model 27N pneumatic servovalve. A DC motor in these servovalves directly drives a valve spool to control flow independently of supply pressure, eliminating springs, nozzles, filters or the pilot valve required in two-stage units. The electronic controller in the valve housing continuously monitors spool position, as determined by a Hall-effect sensor, and compares it to an input command. The controller automatically drives the motor to return the spool to the commanded position when it detects an error.

HR Textron Inc., 25200 W. Rye Canyon Rd., Santa Clarita, CA 91355-1265. Tel: 661-294-6000; Fax: 661-259-9622.