Integrity of Bolted Joints

[daviwy]

Hi,

I dont have a task in this but it was something i overhead. I am quite interested in how people deal with the integrity of their bolted joints to prevent hydrocarbon releases/leakages etc.

Please do drop more information or knowledge you have on this subject they will all be taken in and appreciated.


David O.
Project Engineer

 

[dcasto]

Once the bolt is torqued correctly, unless some outside force acts on it, nothing will change. An outside force would be vibrations.

Other than that, keeping the bolts from rusting is a must. On the Gulf Coast we went to a grease pump system where a sleave is wrapped around the bolted joint and filled with a wax to prevent salt water from getting to the exposed threads. Some people have used coated bolts whixch changes the torque required.

 

[JJPellin]

More specifically, a well designed bolted joint should not change over time. If the joint is correctly designed, there should be some free length of stud or bolt that is stretched when the fasteners are torqued. Those stretched studs (or bolts) become springs that are pulling the two sides of the joint together. Even if something changes slightly in the loads, forces, temperature or gasket crush, the "spring" of the studs or bolts will keep the two sides pulled tightly together. This spring force is dependent on the stress imposed in the fastener which can be controlled by torquing. But, it is also dependant on the strain in the fastener which is dependant on the free length and the geometry of the joint. This is why you sometime see long spacers built into the bottom flange of a vessel at the location of the mounting studs. Extra free length is needed in order to get enough strain from the imposed stress.

Johnny Pellin

 

[SJones]

Start by reading the Energy Institute Guidelines For The Management Of The Integrity Of Bolted Joints For Pressurised Systems. That's how it should be done; then compare with how it is being done!

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Rotator]

This is a big subject! I think Steve has the right direction.
For some useful info on good fitting practices, read ESA / FSA Publication No. 009/98
Guidelines for safe seal usage
-Flanges and Gaskets -