Skip to main content

Air Compressor requirements

  • 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.

Comments

Popular posts from this blog

Why is a man hole door elliptical in shape?

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.

Shell Expansion Plan

It is a two dimensional drawing of a three dimensional surface of the ship’s hull form. This plan is very useful for the following information:It is used for marking the location of a hull Damage on this plan by identifying the strake number , letter and frame number so that the exact location of the damage and also suggested repairs are marked in a localised copy. The shell expansion can be used for finding areas of painting surfaces such as topside, boot topping and bottom areas by applying Simpsons rules directly.  In the shell expansion the vertical scale used is different from the horizontal scale and a suitable adjustment has to be made when calculating areas. This becomes useful in solving disputes concerning areas of preparation and painting. It gives information on the thickness of the original strake which is indicated by the number in the circle shown in the strake.  The quality of steel used is also shown by letters A,B,D E and AH, BH,DH, EH.