opening. The valve is opened by filter discharge pres- sure acting under the valve disk. The valve is closed by filter discharge pressure acting with the tension spring on the top of the diaphragm in the valve cover chamber. The pilot valve and an eductor, both located in the actuating line, control the opening and closing of the automatic shutoff valve. The actuating line runs from the inlet to the dis- charge side (by passing the valve seat) of the automatic shutoff valve body. The pilot valve is of the modified globe valve design, having a double-acting diaphragm as its work- ing means. When fuel pressure is applied to the top of the diaphragm, the valve closes (closing off the actuat- ing line). When fuel pressure is applied to the bottom of the diaphragm, the valve opens (allowing flow through the actuating line). The eductor is located in the actuating line between the pilot valve and the inlet side of the shutoff valve. The eductor suction line is connected to the top of the shutoff valve cover chamber. With the pilot valve open, the eductor decreases the fuel pressure on top of the diaphragm of the shutoff valve by educting fuel from the main valve cover chamber. This decrease in fuel pressure on top of the diaphragm allows filter discharge pressure acting under the shutoff valve disk to open the valve. When the pilot valve closes, filter discharge pressure in the actuating line is directed through the eductor suction line to the top of the cover chamber of the shutoff valve. This increase in fuel pressure on top of the diaphragm cover overcomes the fuel pressure being applied on the valve disk and closes the valve. Simply put, if the pilot valve is open, the automatic shutoff valve is open. If the pilot valve is closed, the automatic shutoff valve is closed. Automatic Water Drain Valve.— This valve, lo- cated in the water drain line from the sump, is identical to and functions in the same way as the pilot valve. When fuel pressure is applied to the top of the dia- phragm in the automatic water drain valve, the valve closes and stops the flow from the filter sump. When the fuel pressure is relieved, the valve opens and allows water to be discharged from the filter sump. Vertical filters have two automatic water drain valves. Float Operated Rotary Control Valve.— The ro- tary control valve, located on the side or bottom of the filter sump, is operated by the rise and fall of a capti- vated ball float housed within the filter sump. The ball float is attached to the rotary valve by a float arm and gear assembly. It is designed to float on water and sink in JP-5. The rotary control valve described here is the one typically installed on vertical filters. The rotary control valve has three operating posi- tions: DOWN, HORIZONTAL, and UP. The valve body has four ports. Three of the ports are connected by tubing to the following: 1. A drain (vent) port to the water drain line on the discharge side of the automatic water drain valve 2. A port to the top of the diaphragm in the pilot valve 3. A port to the top of the diaphragm in the auto- matic water drain valve The fourth port is the supply connection. It is on the top of the rotary control valve inside the filter vessel. The port is fitted with a wire mesh strainer. The rotary control valve, through the action of the ball float, controls the opening and closing of the automatic water drain and pilot valves. OPERATION OF THE FILTER HYDRAULIC CONTROL SYSTEM.— AS long as the fuel passing through the falter contains little or no water, the rotary control valve float will remain it its DOWN position. With the float in its DOWN position, the rotary control valve directs fuel to top of the diaphragm of the auto- matic water drain valve (keeping that valve closed), and vents fuel pressure from the top of the diaphragm in the pilot valve. Direct fuel pressure applied to the bottom of the pilot valve diaphragm opens that valve, which allows filter discharge pressure to open the automatic shutoff valve. As coalesced water collects in the filter sump, the float rises to the horizontal position. With the float at its horizontal position, the rotary control valve vents the top of the automatic water drain valve allowing direct fuel pressure to force it open and drain the accumulated water. The top of the pilot valve diaphragm continues to be vented while direct fuel pressure continues to be applied to the bottom of the pilot valve diaphragm, keeping it open, which allows discharge pressure to open the automatic shutoff valve. If water collects in the filter sump faster than it can be drained off, the float will rise to its UP posi- tion. With the float at its UP position, the rotary control valve directs pressure to the top of the pilot valve (closing it) which causes the automatic shutoff valve to close, stopping fuel discharge. The top of the automatic water drain valve continues to be vented allowing direct fuel pressure to keep it open to drain the accumulated water. 4-30