down through the valve port opening 16 and the inlet opening 21 when this is done as shown in fig4 it is first necessary to remove the roll pin 62 and valve stem cap 61 so that the entire valve poppet 49 can be removed through the inlet opening 21 when the valve is installed in a sootblower or other device the valve is opened by an actuator which engages the valve stem cap 61 and moves the valve downward until the valve head 51 is far enough off the valve seat to allow maximum flow through the valve while the valve is open the valve stem is rotated by turning the valve stem cap 61 until the throttle ring 71 moves far enough downward to reduce the flow through the outlet opening 24 to the desired rate of flow since the restriction required to reduce the flow now takes place between the edge 77 of throttle ring 71 and the upper edge of the valve port opening any erosion caused by pressure drop occurs at these points and not at the sealing faces 19 on the valve seat and at the valve poppet since the wear takes place at non sealing portions of the valve a certain amount of mechanical erosion or metal removal can occur and if large enough be compensated for by adjustment of the position of the throttle ring 71 without any loss of sealing when the valve is closed however during the initial opening of the valve as the head 51 moves away.