A valve (13a) is described comprising: a housing (50) having a fluid inlet for (54) receiving a flow of compressed fluid and a fluid outlet (55); a flow duct (60) movably mounted with respect to the housing, the duct (62) having a fluid inlet (62) for receiving a flow of compressed fluid and a fluid outlet (65), the fluid outlet being positioned around at least a part of the circumference of the duct and being dimensioned to provide a different flow rate at different sections or positions around the circumference of the duct; the fluid outlet of the housing being alignable with a portion of the fluid outlet of the duct to provide a flow rate related to the relative position of the portion of the fluid outlet of the duct and the fluid outlet of the housing; and, a drive element (70) for moving, e.g. rotating, the duct with respect to the housing such that a desired portion of the fluid outlet of the duct aligns with the fluid outlet of the housing. The valve may operate as a so-called throttle valve. It is an advantage that the valve is quickly movable into a desired relative position in order to regulate fluid flow through the valve. The valve is designed to have a long operational lifetime as, even if the outer surface of the duct wears, the outlet will not substantially change in size and the throttling effect will remain substantially the same.