Compressors, hydraulic piston

The slide is located in the compressor casting below the rotors, allowing internal gas recirculation without compression. Slide valve is operated by a piston located in a hydraulic cylinder and actuated by high-pressure oil from both sides. When the compressor is started, the slide valve is fuUy open and the compressor is unloaded. To increase capacity, a solenoid valve on the hydraulic hne opens, moving the piston in the direction of increasing capacity. In order to increase partload efficiency, the slide valve is designed to consist of two parts, one traditional shde valve for capacity regulation and other for built-in volume adjustment. 

In high-pressure applications (70-8,250 bar = 1,000-120,000 psi) and in the capacity range of 3-1,200 kg/d (1-350 scfm), intensifiers are often added to the compressor. In these oil-free, nonlubricated gas pistons/ the pressure of a hydraulic fluid moves the piston as it compresses the GH2 (Figure 1.51). Both the flow and the discharge pressure of the H2 are controlled by the hydraulic drive. This way, the rate at which the electrolyzer generates the H2 is matched to the H2 flow in the compressor. 

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