It is important to consider the function when selecting a solenoid valve for a fuel application. If it is on a diesel tank and the feed is just gravity – no pumped pressure – we must select a valve which has a zero differential function.
On a smaller valves, say up to 3/8” BSP, this can be direct acting where the armature is operated purely by electromagnetic forces. The core to be pulled up by the electromagnetic field of the coil when the unit is energized. The media can then flow through the valve orifice relying only on the head pressure of the tank. When the coil power is turned off the armature closes off the orifice with the assistance of a spring and the head pressure (the valve is designed to have the flow down through the orifice and this extra pressure also assists on the positive seal). This valve gives up a pressure range from 0 to 10 Bar (150Psi).
From ½” to 2” BSP the orifice is too large for a direct acting valve (the coil would end up the size of a football) so we use a coupled diaphragm to give us the zero differential effect. The armature and diaphragm are one assembly. At drain and low pressures the coil pulls the valve open by lifting the diaphragm (as it is coupled). At higher pressures opening is assisted by the fluid pressure pushing the diaphragm into the roof cavity of the valve. These types of valves are also useful for the suction side of a pump were the supply is from a tank and you want to close off to stop any draining when the pump is turned off. It is important to note that some manufacturers recommend NBR (nitrile) for diesel applications. Although NBR is fine with diesel by itself, it reacts with the additives so it is always best to stick to Viton (FKM). An example of great diesel/fuel valves can be seen in our brass B55 series and our 316 Stainless S55 series.
Feel free if you would like to contact us with any questions.