Abstract: A valve, in particular of an extrusion blow moulding machine or a stretch blow moulding machine for manufacturing hollow bodies, has a movable piston, a process fluid region and a compensation chamber. The piston has a free front face which faces the process fluid region with a circumferential outer sealing region. At least one connecting channel connects the process fluid region to the compensation chamber. The free front face of the piston has an elevation, which is surrounded by the outer sealing region. The elevation protrudes over the outer circumferential sealing region. The valve permits a rapid and precisely timed opening.

Abstract: In a method for monitoring a blow-moulding device for producing a hollow body, the blow-moulding device includes at least one process valve unit for feeding a process fluid into a preform of the hollow body under process pressure, wherein the process valve unit includes at least one electrically operated valve. During a blow-moulding process, at least one value of an electric current of the electrically operated valve is detected. The method and the device allow early recognition of an ageing process of the process valves, in particular their pilot valves, and/or the recognition of the status of valve properties.