Same Size Clamshell Bellows

The best way to replace a leaking expansion joint element is to replace the entire expansion joint assembly or at least a portion of the expansion joint that includes weld ends. In this way, the installers can avoid making the delicate bellows attachment weld in the fifi eld. However, this approach requires that the pipe be cut to replace the leaking bellows. When replacing nuclear containment penetration bellows and many other critical expansion joint bellows, it is not practical to cut the pipe to which the bellows is attached. The “same size clam shell” is one approach to replacing these expansion joint elements.

The first step in the “same size clamshell” is to verify the dimensions of the existing bellows and then manufacture a replacement bellows identical to the original. The replacement bellows is cut in half longitudinally and match marked for reassembly.

The existing bellows is removed by grinding off the attachment weld and then cutting the bellows element in half longitudinally. The bellows attachment surface is ground to prepare the surface for the new “same size clamshell”.

The factory made “same size clamshell” is then fifi tted to the prepared bellows attachment surface on the existing pipe. The inside of the new clamshell bellows is purged with the proper welding gas to insure a good weld. Then the bellows is welded back together. The bellows attachment weld completes the assembly.

It is recommended that all finished welds be dye penetrant inspected.

All fi eld work should be performed by a crew that has been fi eld qualifi ed for clamshell work on the required bellows thickness. Senior Flexonics Pathway continuously trains and qualifi es welders to perform clamshell work under simulated job site conditions.

The same size clamshell cannot be performed while the system is pressurized. All clamshell bellows must be single ply construction. A clamshell bellows can be fi t with reinforcing rings for high pressure service. Clamshell bellows can be certifi ed for use in ASME Section VIII code stamped pressure vessels.