An inlet valve for regulating the pressure at the inlet channel of a vacuum pump comprising: a first chamber defined by a housing having at least one inlet channel connected to a first supply of a fluid, comprising a movable element defining two cavities fluidly sealed from each-other and means for exerting a force on the movable element; a second chamber separated from the first chamber by a wall and defined by a housing, being in direct communication with a process channel of a second supply of a fluid; a valve body slidably mounted in the wall to prevent a fluid flow between the second chamber and the second cavity of the first chamber, the valve body having a distal end and a proximal end, wherein the valve body comprises a fluid channel extending through the valve body allowing a fluid flow between the first cavity and the inlet channel.

A flow stop valve positionable in a downhole tubular, and a method, in which the flow stop valve is in a closed position when a pressure difference between fluid outside the downhole tubular and inside the downhole tubular at the flow stop valve is below a threshold value, thereby preventing flow through the downhole tubular. The flow stop valve is in an open position when the pressure difference between fluid outside the downhole tubular and inside the downhole tubular at the flow stop valve is above a threshold value, hereby permitting flow through the downhole tubular.

In the relief valve, an annular convex portion 16a that is convexed in a direction in which a valve element 5a moves away from a valve hole 17 along a center axis of the valve hole 17 and that is arranged around the valve hole 17 is formed in a valve chamber 16, an annular concave portion 5d that is concaved in the direction in which the valve element 5a moves away from the valve hole 17 is formed in the valve element 5a, and in a shut-off state, the annular convex portion 16a is accommodated in the annular concave portion 5d, and an annular channel 19 that extends in a direction of the center axis is formed between an outer peripheral surface 16b of the annular convex portion 16a and an inner peripheral surface 5e of the annular concave portion 5d.