TABLE OF CONTENTS Initially, I was going to create separate chapters to cover the subjects of bolts and gaskets for process piping systems; however, because they are so closely linked, I decided to place them in the same section. Bolts and the accompanying gaskets form a huge subject from an industrial perspective; however, I discuss their function only within the context of the jointing method for process piping systems. A set of bolts and gaskets are used to achieve a pressure-retaining seal when two flanges are mated together.
For ASME flanges, bolts, sometimes called fasteners, are used in sets, which come in multiples of four bolts, with four the minimum number. The bolt spacing is carefully calculated, taking into consideration the nominal pipe size of the flange, the design temperature, the pressure to be encountered, and the material of the flange to ensure good sealing characteristics. The outside diameter of the bolt, its length, and the thread engagement are also important factors to consider. The material of the bolt must be of sufficient strength to allow the correct bolt loads to be applied; however, a high-strength stud bolt combined with a lower strength flange results in deformation of the flange when bolt loads are applied. It is also important that the nuts have full engagement with the thread of the stud. Some companies specify that 1.5 to 3 threads must be exposed above the crown of the nut, to guarantee that full engagement has been achieved. Too many threads exposed...
