Bolt fastening method
2022-09-28
Torque-free ring wrench or hammer wrench: applicable to general equipment and pipeline flange fastening, according to the bolt size and flange pressure rating. The fastening requirements are as follows:
1) The maintenance unit shall formulate the fastening scheme, fasten the flange symmetrically, and number the fastening sequence. Refer to Figure 1 and Figure 2 for numbering.
2) Position the gasket with 4 bolts at positions 1 , 2 , 3 and 4 to ensure that the center of the wound gasket is within the flange edge.
3) Tighten the positioning bolt by hand, then insert other stud bolts and tighten them by hand to balance the load, ensuring that at least 2 threads are exposed at each end of the nut.
4) According to the field equipment and flange, the fastening times (at least 3 times) and the hammering load (strength) for each fastening shall be reasonably determined according to the calculation of one fastening circle. The fastening hammering load (strength) shall be fastened from small to large (e.g. 50% , 80% , 100% in increments). The unloadable load shall be too fast and too large to prevent gasket sealing failure.
5) No torque ring wrench or hammer wrench tightening sequence:
Tighten two diametrically opposite bolts to a given hammering load (force) of the bolt;
Tighten another pair of bolts that are about 90 degrees away from the previous two bolts along the circumference;
Continue tightening until all remaining bolts are tightened to the given hammer load.
6) Finally, tighten all bolts clockwise or counterclockwise according to 100% hammer load (strength).
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