Removing Code "pedigree" on shell side of Heat Exchanger
Removing Code "pedigree" on shell side of Heat Exchanger
(OP)
Large condensor (horizontal tubular ht xchgr) has over 1400 3/4 OD tubes which contain cooling water at 30 psi. The shell surrounding the tube bundle contains a gas/vapor at less than 5 psi. Both the shell side and tube side are rated at 50 psi and Code (U) stamped.
The shell has developed 2 very serious cracks (180 deg. apart) in the middle shell course propogating from large inlet nozzle in top of shell. Due to the large cracks, best NBIC repair method would be to replace the shell course and inlet nozzle, however the shell portion does operate at less than 5 psi.
Jurisdictional rules require vessels greater than 15 psi and 5 cubic feet be Code stamped...since shell side operates at less than 5 psi, could new saftey valve(s) set at 6 or 7 psi be installed on shell side and the Code stamping for the shell side be obliterated on the nameplate? Then the repair of the cracked shell could be done as "non-code" till new vessel can be received and installed? (Typically, the shell side is operating at about 1 to 2 psi). The Code pedigree for the tube side and channel side would remain since they do exceed 15 psi.
The shell has developed 2 very serious cracks (180 deg. apart) in the middle shell course propogating from large inlet nozzle in top of shell. Due to the large cracks, best NBIC repair method would be to replace the shell course and inlet nozzle, however the shell portion does operate at less than 5 psi.
Jurisdictional rules require vessels greater than 15 psi and 5 cubic feet be Code stamped...since shell side operates at less than 5 psi, could new saftey valve(s) set at 6 or 7 psi be installed on shell side and the Code stamping for the shell side be obliterated on the nameplate? Then the repair of the cracked shell could be done as "non-code" till new vessel can be received and installed? (Typically, the shell side is operating at about 1 to 2 psi). The Code pedigree for the tube side and channel side would remain since they do exceed 15 psi.





RE: Removing Code "pedigree" on shell side of Heat Exchanger
I believe there was a good reason for designing both sides for 50 psi, because in case of failure, the shell side could see 30+ psi. My advice is to not rubbish the good condenser with cheap spin to the code and do the right thing, do the repair as per the code and you will sleep better at night, without keeping vigil waiting for the knock on your door. Murphy says if it could go wron, it will.
Cheers,
gr2vessels
RE: Removing Code "pedigree" on shell side of Heat Exchanger
At the same time you should have a metallurgical F/A done on the cracks. A good failure analyst will include recommendations for reducing the risk of recurrence.
RE: Removing Code "pedigree" on shell side of Heat Exchanger
In my career (40+ years) I've seen one nameplate removed from operating equipment.
Could you post a picture of the vessel and cracked area?
RE: Removing Code "pedigree" on shell side of Heat Exchanger
RE: Removing Code "pedigree" on shell side of Heat Exchanger
RE: Removing Code "pedigree" on shell side of Heat Exchanger