have a great concentration of stress cracks at both ends of the cylinder, so that the crack continue to expand. If we use the hole stopper method to stop the cracks at both ends of the cylinder, not only limited to reduce stress concentration, and not to limit the depth of the crack development. When depth of the cracks more than 1/3 the thickness of the cylinder, Should do strength checking calculation for cylinder, Insufficient strength should open the slot and do welding.