Valve repair--CRITICALITY OF BOLTING

on Gans, Ph.D., technical training manager at Granite Services, Inc., condensed the information he usually presents during a one-day course into a well-received hour-long presentation on the criticality of torque and load in bolted joints.

He explained how critical the ­common bolt can be.

“Bolts are really the only way to join big pieces of equipment, which allows you to take them apart to maintain the equipment, but there are many factors that must be considered,” Gans said. “Bolted joints must stay together until a decision is made to take them apart. It is inexcusable for a joint to fail because we have the tools available to calibrate and make them 100% fail-safe,” he said.

“What we do not have are the people trained to meet the requirements,” he added. While welders have to be certified, anybody in a plant can pick up a tool and close a joint, he explained. This is despite the reality that there are so many considerations, including enough but not too much tension and the fact the three component groups of a joint, which are flanges, fasteners and gaskets, must operate together as a system. The bolting sequence is critical, he added. Each part must be right to obtain a seal, and you can’t compensate for a problem in one part of the system by overcompensating on another part of the system.

It is absolutely critical that flanges be aligned properly, and even though a system can get up and running, radial or lateral misalignments in that system create the chance for leaks or huge problems later on. Bolts are not flange alignment tools and the proper torque is absolutely essential, he said.

Source form internet