- In common rail system of fuel injection, common piping supplies fuel to the individual injectors by a branch pipe which is the feature of the common rail system. This pipe and the full system is under high pressure i.e. the injection pressure.
- To control this, a bypass valve is utilized which is fitted at the end of the common pipe.
- By closing or opening this valve, more or less, the fuel is bypassed from the system back to the suction of the pump, thus reducing the pressure.
Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole is lesser in size than the corresponding circular hole. More over it is prime concern to have a smoothed generous radius at the corners to eliminate stress concentration. Hence other geometrical shapes like rectangle and square are ruled out. To compensate for the loss of material in the shell due to opening, a doubler ring has to be provided around the opening. The thickness of the ring depends on the axis length along the dirrection in which the stresses are maximum and the thickness of the shell. It is important to align the minor axis along the length of the vessel, as the stress in this direction is maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t= thickness of the shell plating Circumferential stress: Pd/4t More over a considerable material and weight saving is achieved as minor is along the direction of maximum stress.