High-pressure system bolt tightening issues
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Regarding bolt tightening in high-pressure systems, what is the correct sequence for tightening? What is the tightening force?
The basic principle for tightening high-pressure flange bolts is to do so in a cross-pattern. There is usually an installation procedure guide available; if none is available, it is necessary to number the bolts oneself and tighten them in a cross-patterned sequence； The numbering method is described in ASME-PCC-1 and the Pipeline Handbook. There are two concepts related to tightening force: tightening torque and preload, both of which are determined based on the actual operating conditions of high-pressure flange bolts; it’s not possible to generalize. There are some posts on forums that can serve as a reference.
Regarding bolt tightening in high-pressure systems, it is necessary to avoid uneven force when tightening flanges; the tightening sequence should follow a symmetric and cross-directional pattern
I’m not sure what tools to use; generally, for tightening high-pressure bolts, torque wrenches and hydraulic stretchers can be used! The bolt length requirements vary. The torque value and tensile force must be determined based on the size of the bolt, and the working oil pressure varies depending on the type of tool used.
The tightening sequence generally requires symmetrical tightening; hydraulic tensioners can tighten 2 to 4 bolts at the same time, while torque wrenches usually can only tighten one bolt at a time. However, it requires tightening multiple times, evenly and symmetrically. It must not exceed the yield limit of the bolt.
Generally, important equipment requires tightening bolts. Some are set based on the tightening force, while others are set according to the heating temperature; clear instructions are generally provided in the usage requirements!
Tightening of high-strength bolts in high-pressure systems: Generally, the torque value is determined first based on the specifications of the bolts. The bolts are tightened diagonally using 50% of the specified torque to ensure that the sealing surfaces remain parallel, followed by tightening with 80% and then 100% of the torque. While tightening, it is important to check whether the gaps between the flanges are uniform. At 100 pounds of force, tighten it continuously three times to ensure consistent tightening force for each bolt. For applications requiring heat sealing, seal twice at 100 pounds of force.
I didn’t see any reference standards regarding the tightening torque; who knows?