Any crack on the surface of pressure vessel can lead to a fatal accident during operation, so it needs to be crack analysis. The present work has done on a horizontal type of thin walled pressure vessel. It was designed to work for an internal pressure of around 150 bars and external pressure of one atmospheric. Its maximum working temperature is 70⁰C. Hence procedure has been developed to analyse the crack extension over the surface of pressure vessel due to operating parameters by using techniques like SIFs and J-integral supported by the results of FEA.