The VG... gas valves with their electrohydraulic SKP... actuators are designed for gas families
Actuator type SKP2... is equipped with an integrated precision gas pressure governor. This type of actuator with gas pressure governor not only reduces the length of the gas train, but usually also permits selection of a smaller valve size. For detailed information about valve sizing, refer to ?Flow chart?. The actuator is also available with limit and auxiliary changeover switches, e.g. for indicating the fully closed position or for stroke limitation in connection with 2-stage gas release, etc.
Therefore – in contrast to conventional gas / air ratio control – air volume changes due to mains pressure variations, soiled fan wheel, etc., have no impact on the quality of the combustion process.
The actuator’s hydraulic drive system consists of a cylinder filled with oil and an electric oscillating pump with piston and relief valve. The relief valve is located in the bypass between the suction and pressure side of the pump. With the actuators of the B-series, it is a valve hydraulically actuated by the pump pressure; with the 2-stage actuators of the A-series, it is a normally open solenoid valve. The cylinder carries a seal which hydraulically separates the inlet from the outlet side of the pump, also serving as a guidance for the piston. The piston is also guided by a rod which is rigidly connected to it. This rod transfers the piston’s travel directly to the valve stem. The rod is provided with a disk the position of which is visible through a window in the console (indication of stroke).
Using a lever system, the disk also actuates
the auxiliary switch for indicating the fully closed position, or
The switching points of these switches are adjustable over the entire stroke. The adjusting screws are located in the terminal compartment.
other positions, as well as the limit changeover switches for positioning the lowand high-fire stroke with the two-stage actuators.