Stainless steel needle valves are used to vary the flow cross section, thus regulating the flow volume. The flow is regulated by a cone-shaped valve that is moved by means of a spindle away from or toward the valve seat. The amount of flow change is determined by the size of the resulting angular gap between the cone and seat. The rate of flow change is determined by how much the valve spindle is turned as well as the pitch of the valve spindle thread.