We did metallography at affected portion and the finding are as below:- Both (massive) grown up carbides and fine particles of globular carbides in the ferrite matrix were observed. No creep cavities are seen.Mostly of grain boundary carbide precipitation and distribution of fine carbide particles in a ferrite matrix. No creep cavities are present. For your view please. For information we have replced the affected tubes with new one.

Chakra For HT, you have to go as per ASA B 31.3 pressure-temp curve (i.e, allowable stress at design temp) is taken for calculating the ratio of HT at room temp. In this case 50 KSC is likely to be HT pressure. Trust this helps you C.V.Srinivasan Nishi Engineers Pvt Ltd India Aug 7 E-mail: nishi@vsnl.com >Hi Krish, > >It is a good decision that you have replaced the tubes. >Although Vacuum furnace tubes rarely ruptures in service. > >I hope you go for a destructive mechanical strength testings >(UTS/YS etc.) of the failed tube. If possible, go for ASRT. >This would provide very good base-data for future uses. > >Regarding the hydrotest pressure of 50 kg/cm2 - the logic is >not very clear. > >Generally, the feed pump shut-off pressure is taken as the >design pressure of the furnace. That is why you get 14 >kg/cm2 pressure as the design pressure. The operating >pressure at the outlet would be almost a vacuum. > >We generally go for hydrotest at 12-20 kg/cm2 pressure range >with same design pressure. > >Regards

Dear chakra, What is meant by ASRT?