Clamp shell bellows

Expansion joints are critical equipments in a FCC flue gas piping system. I am looking for any information on the use of outer pre installed clamp shells on new expansion joints. The intention of the outer clamp shell is for quick sealing weld, just in case of a flue gas leak through the inner expansion joint, avoid a big shutdown and keeping the unit running till the next big turnaround for definitive replacement of the inner expansion joint.

luis marques

pipehead

Thank you for your reply. The intention of my posting is to share points of views with others experience on dealing with expansion joint bellows in FCCU units. As you know, expansion joints are critical equipments in FCCU complex flue gas piping systems. The most critical are the ones installed in horizontal position, as the acid flue gas condensate tends to accumulate in lower point of bellows, accelerating the corrosion.
Nowadays, FCCU units are required to support cycle runs of 5 years, for this reason, expansion joints should have great liability and in that sense the actual tendency is to use 2 ply expansion joints with pressure taps to signal leakage of inner ply. Any way, besides the liability improvement with the use of 2 ply bellows, my intention is to have a redundant protection in the case of failure of inner and outer plies.
I think that it would be possible to equip expansion joints with redundant devices such as flexible telescopic boxes around the bellows plies, with stuffing box and solid ring with screw fasteners to push the stuff and stanch the leak when it occurs.
Such a system wouldn’t require any welding. To stanch a leak we only need to slow down the unit until zero pressure, to allow maintenance workers to fast the screw fasteners.

Others input on this discussion is welcomed

Regards

Luis marques

Luis,

Clamshells can and have been installed while on-line, it is not for the faint of heart.

Sealable covers can be supplied with the expansion joints for hard boxing the bellows in during an emergency. This is done while the system is hot, although I suspect that most users forget to cut them lose at the next shutdown before the line cools.

Heating blankets have also been used to keep any acids from condensating on the bellows.

For a good independent view on this issue I would suggest Refinery Technology Incorporated (RTI) in Houston.