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cracked bolts on heat exchanger

cracked bolts on heat exchanger

cracked bolts on heat exchanger

(OP)
Hello guys,
after instaling new tube bundle of water coller of LPG on crude destilattion unit , bolts on floating head were cracked after few hours of operation (first time 5 hours, second 36 hours).
LPG leaks to the cooling water. Exchanger was hidrotested succesfuly after installation. With old tube bundle we operated ten years without problem.
Do any of you have some esperience with these problem?
Maintance guys think that problem is corrosion and inadequate bolts...process engeneers suppose problem with inproper instalation of tube bundle or inadequate geometry of tube bundle - no space to thermal expansion - floating head does not "floate"
What you think?
Thank you
R.

RE: cracked bolts on heat exchanger

What is the bolting material, the floating head material?

rmw

RE: cracked bolts on heat exchanger

Seeing as how the hydrotest had no issues, there shouldn't be any problem at all at the operating pressure, Bolts may have been over torqued or the floating head did not float, either of these could cause them to fail quite quickly as fixed thermal expansion forces are quite massive.

RE: cracked bolts on heat exchanger

Normal B7 bolts can crack if the LPG (shellside?) is sour.  Is it sour?  Did the bolts fail in a brittle fasion, without elongation? Was bolt hardness checked?

RE: cracked bolts on heat exchanger

Send the failed bolts to a metallurgical lab. They will tell you if they failed from fatigue, over-stress, environmentally induced cracking (Chloride stress corrosion cracking, hydrogen embrittlement, etc.).

Johnny Pellin

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