- The diesel engine fuel injection piping is subjected to very high pressure, in the range of about 1200bar. Also, there is sudden increase and decrease of pressure which causes the fatigue in the material.
- Taking into consideration these two things it is necessary that the material and the manufacturing process of the piping should be such that it should be able to withstand the high pressure and fatigue.
- It is also of prime importance, from the point of view of safety of the ship and fire hazard, that the fuel pipe should not get cracked under these high pressures. In order to achieve these requirements, it is necessary to use fuel pump pipes made up of seamless, solid drawn tubes.
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.