Bolt tightening will follow a sequence with a diagonal pattern, indicated in the ASME PCC-1 table 3 & 3. Most joints consist of several bolts and since the vast majority of bolts are not tightened simultaneously, the effect of tightening one bolt in the group has an effect on the preload in other previously tightened bolts in the group. Such an effect is called elastic interaction, or alternatively. For proper ANSI flange bolt tightening, follow a sequential “star” or criss-cross pattern, tightening bolts in stages to ensure even gasket compression and a secure, leak-free connection. Bolted flange joint assemblers have been using the Star Pattern since Taylor Forge started standardizing on flanges in 1938.
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