Hydrogen Bakeout
Hydrogen Bakeout
(OP)
Does anyone know where I can find some good rules of thumb regarding when hydrogen bakeout should be performed when welding to piping that has been in hydrogen service? Some data regarding hydrogen diffusivity as a function of partial pressure and temperature would be fantastic, but even some general guidelines would be appreciated.
RE: Hydrogen Bakeout
I have never seen anything on this. I have always thought of it as service identifying. I know this doesn't help but if there is any thing on this then I would be interested to!
RE: Hydrogen Bakeout
RE: Hydrogen Bakeout
GENERALLY SPEAKING hydrogen embrittlement is not a problem if the steel alloy is HT to, or less than, 160KSI FTU UTS. IF steel alloy is HT to less than 160KSI FTU, then don't worry about it.
IF You are REALLY concerned, perhaps You could do either of the following:
Bake same as for cad-plating hydrogen embrittlement relief [ref ams-qq-a-416]
and/OR
weld on a valve, then cut-it up for metallurgical sampling and testing.
Regards, Wil Taylor
RE: Hydrogen Bakeout
I have recently read something that is just what you are asking for, but I can't remember where I read it. However, I do have a book here with a chart regarding "methanization", which causes blistering in steel due to hydrogen diffusion. It uses curves based on partial pressure of H2 vs. temperature for various steels. The book is called "Corrosion Control in the Chemical Process Industies" and is available from NiDi (Nickel development institute) at no charge. "Weldability of Steels" by Stout also has a chart for solubility of Hydrogen in Iron. I don' think these are exaclty what you are looking for, but if I can remember where I got that other information, I will post it.
G Roberts
RE: Hydrogen Bakeout
why not read NACE MR 01 75. it deals with means to avoid hydrogen embrittlement of various grades of steel in sour service. formulas, charts, and heat treatment; I think it will help.
RE: Hydrogen Bakeout
Why not read NACE MR 01 75 . It deals with means to avoid hydrogen embrittlement of various grades of steels in sour service. It provides formula for H partial pressure, charts and h/t required vs steel grade. I think it will help.
RE: Hydrogen Bakeout
RE: Hydrogen Bakeout
EN 12329:2000 has been mentioned to me but none of the standards, I have come accross help me deide the baking process necessary, baking time, maximum time to oven post-plating etc.
Anyone any ideas
RE: Hydrogen Bakeout
SAE AMS 2759/9 HYDROGEN EMBRITTLEMENT RELIEF (BAKING) OF STEEL PARTS
http://www.sae.org/servlets/productDetail?PROD_TYP=STD&PROD_CD=AMS2759/9A
SAE USCAR-5 AVOIDANCE OF HYDROGEN EMBRITTLEMENT OF STEEL
http://www.sae.org/servlets/productDetail?PROD_TYP=STD&PROD_CD=USCAR5-1
SAE USCAR-7 DEEMBRITTLEMENT VERIFICATION TEST
http://www.sae.org/servlets/productDetail?PROD_TYP=STD&PROD_CD=USCAR7
Ford, GM, and DaimlerChrysler all developed their own internal standards that were the basis for the two USCAR documents. ASTM also has a number of standards on the subject:
http://www.astm.org/verity_highlight.cgi?UserQuery=HYDROGEN+EMBRITTLEMENT&SEARCH_COLLECTION=STANDARDS&SEARCH_STATUS=ALL&MARKETING_CODE=GP1&NS-search-type=Free+text&NS-max-records=1000&NS-search-type=boolean&NS-query=HYDROGEN+EMBRITTLEMENT&CART_NAME=nxuy5900&STORE_NAME=mystore&NS-collection=ASTM_STANDARDS&NS-collection2=ASTM_WITHDRAWN_HIGHLIGHT
ISO 9588 is the worldwide standard to which ASTM B 850 is the US equivalent. ISO document can be obtained directly from ISO at http://www.iso.ch or from Global Engineering Documents at http://global.ihs.com/ .