- Two starting compressors must be fitted, of sufficient total capacity to meet the engine requirements. Each compressor must be able to press up Air receiver from 15 bar to 25 bar in thirty minutes. Two air receivers must to be provided. Total air receiver capacity is to be sufficient for Twelve (12) starts of Reversible engines and six (6) starts for non-reversible engines.
- Additional one Diesel driven or hand operated (or if possible, both) emergency air compressor must be fitted to start auxiliary engines of a “Dead Ship”.
- Safety valves or preferably bursting discs must be fitted on the cooling water casing to give ample relief of pressure, should an air-cooling tube burst.
- Each compressor must have a safety valve designed so that the accumulated pressure, with the outlet valve closed will not exceed 10% of the maximum working pressure.
- The air compressor cylinders, covers, intercoolers and after-coolers, are tested by hydraulic pressure to twice their working pressure.
- The casing of the inter-cooler and after-cooler is hydraulically tested to 1.5 times cooling water pressure. Thus, for 4 bar cooling water pressure, the casing will be tested at 6 bar pressure.
- A water separator or drain should be fitted on the airside of each intercooler. The drain cock should be used at regular intervals to prevent water from one stage being carried into the following stage.
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.