can we N+T using induction heating?
can we N+T using induction heating?
(OP)
There is a possiblity that we may need to remove incorrectly heat treated HP main steam line sections ( SA 335 P91) form a commissioned power plant and send them out for N+T, or else replace them.
Is it feasible to N+T at the site using either induction heating or a portable furnace? N+T at 1850 F, typical size is 16 " NPS with bent els, each piece may be 40 ft long?
It is beginning to look like there are a lot of plants with this issue.
Is it feasible to N+T at the site using either induction heating or a portable furnace? N+T at 1850 F, typical size is 16 " NPS with bent els, each piece may be 40 ft long?
It is beginning to look like there are a lot of plants with this issue.





RE: can we N+T using induction heating?
RE: can we N+T using induction heating?
Fro Grade 91 pipe material, I would not recommend induction heating. You should use a furnace for the N&T to assure a uniform austenitizing treatment prior to rapid cooling and tempering.
I would seriously look at sending the Grade 91 pipe spools to a heat treatment shop versus building a portable furnace in the field. For pipe spools up to 40 feet in length you need a rail car type furnace. There are several forging shops around the US that can handle this size, and have quenching and tempering furnaces (BendTec, Scott Forge,,,,).
RE: can we N+T using induction heating?
Rao Yallapragada
RE: can we N+T using induction heating?
Can you share any more info? for example did this affect common main steam piping, or boiler piping on one unit (or both?
RE: can we N+T using induction heating?
I can only say,in a general sense, there are several recent gas fired combined cycle plants , for which the hot bent els were fab'd by a small forge in Mississippi/Louisianna area, have shown low hardness ( < 180 Hb), microstructure shows ferrite/pearlite with nil martensite, P9 instead of P91 creep properties, expected life implies "rejuvenation" via N+T to be scheduled. This mom and pop forge has been supplying hot bent P91 els to these kind of plants for at least 6 yrs, which means some are approaching the life of P9 , instead of a 50+ yr creep life with P91 metallurgical properties.
Unfortunately, it appears that the EPC vendors that were flush with work a few years ago did not know that , according to the ASME , the "designer" is responsible for specifying the hot bending procedure- it is not correct to assume the forge will have a metallurgist that will catch these errors. The correct specification of N+T, correct cooldown rate, and post fab NDT apparently was not uniformly applied in those boom years.
RE: can we N+T using induction heating?
I would be interested in finding out how many other plants that davefitz was referring to has this problem.
RE: can we N+T using induction heating?
Any idea why there is so little info out there on this important topic?
Cheers.
RE: can we N+T using induction heating?
RE: can we N+T using induction heating?
I would advise hardness testing of all purchased fittings and induction bends and that they meet a 190 BHN minimum hardness ( I would actually like to have a minimum hardness of 200 BHN to mitigate effects of PWHT at the spool fabricator and additional PWHT at the site). Our studies have shown that fittings with hardness < 170BHN do not possess the required tempered martensitic microstructure.
We will be performing 1000 hr creep testing on removed P91 induction bends having ferrite microstructures and highly tempered (hardness approximately 175 BHN) martensitic microstructures. I expect to have data this summer to share.
RE: can we N+T using induction heating?
RE: can we N+T using induction heating?
Not possible if the material is Grade 91. Grade 9 material is not supplied in a quenched and tempered condition. Replication would only be useful if the hardness of the Grade 91 material is out of range.
RE: can we N+T using induction heating?
We have also found P9 and P5 fittings (mixed steels) stamped as WP91; PMI should always be done.
When performing replications, it is important to remove the decarburized zone which we have verified as being as great as 0.040-inch; in the majority of cases seen to date, the decarb layers are only 0.005 to .010-inch.