Who should decide on the method of pre-tightening the container flange bolts?
Thread Content
There are many ways to pre-tighten container flange bolts. The pre-tightening effects achieved by different pre-tightening methods vary to some extent. Currently, the original designs for nuclear power pressure vessels are primarily based on foreign drawings, and the bolt installation methods follow foreign standards, with few modifications made. For ordinary pressure vessels with identical functions, different manufacturers may use different methods for tightening flange bolts; so, is it determined by the designer? Did the owner decide it too? Is it still specified by the standards?
The designer shall perform calculations in accordance with the standards, record them in the design documents, and specify the method of use.
Generally, design engineers only verify the strength of bolts and flanges based on the compression force required for sealing, without specifying the preload during actual installation, and standards also do not provide such specifications. The owner can simply tighten the bolts themselves. The designer guarantees the bolt strength.
For ordinary pressure vessels, it is the owner who determines these details, but for some special types of equipment, the relevant units must make such decisions; for high-pressure vessels such as hydrogenation reactors and ammonia towers, the method and sequence of tightening the bolts must be specified.
Don’t rely on the design firms or the clients; we have built N units of high-pressure equipment – for hydrogenation, urine treatment, and ammonia production – and we had to calculate everything by ourselves, damn it. There are some special gaskets, and it’s unclear what values were used for the gasket coefficient and sealing pressure ratio during design by the design team. If those values are chosen incorrectly, the tightening force will also be wrong, resulting in an inability to achieve a proper seal during the hydrostatic test; in addition, the gaskets may get damaged, which is extremely frustrating. If the design firm and the owner are willing to come up with a plan, I would be over the moon.
That should be the job of the equipment designers! I think it should be determined by the equipment designers in accordance with standards, along with technical requirements for installation; this will help clarify responsibilities!
It depends on which company is responsible for the design and overall project management. If it’s a company that takes its future seriously, it will meet the requirements mentioned on the second floor; otherwise, it’s hard to say.
This post was last edited by yakui on 2009-10-20 13:01. It should be decided by the design department.
We have a hydrogenation reactor produced by Yizhong, and it seems there are no specifications regarding preload. It’s not possible to know during construction what the appropriate level of pre-tensioning should be
The design institute specifies the tightening torque for the bolt connections of the containers; however, there are generally no rules regarding how to achieve this torque – it is up to the manufacturer to decide!