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Up Topic Welding Industry / Metallurgy / PREHEAT TEMP REQUIREMENTS
- - By mujibali_m_a (*) Date 05-07-2008 07:53
FOR A WELDING PROCEDURE QUALIFICATION (AS PER ASME SECTION IX) WITH PREHEAT I NEED THE PREHEAT TEMPERATURE FOR CS MATERIALS. WHERE (WHICH STANDARD/CODE) I WILL GET THIS INFORMATION?
Parent - - By 3.1 Inspector Date 05-07-2008 12:33
WHY DO YOU NEED PREHEAT?
WHAT IS THE WELDING METHOD?
WHICH KIND OF CS?

JUST WELD IT AT AMBIENT TEMP. AND RECORD THE INTERPASS TEMP.
AN INCREASE OF 100F IS ALLOWED IF CHARPY IS SPECIFIED
Parent - - By mujibali_m_a (*) Date 05-08-2008 05:59
WELDING PROCESS GTAW+SAW; MATERIAL A 516 GR 70 THICKNESS-35MM; IMPACT REQUIRED @ -29 DEG C. NO PWHT. WHERE I WILL FIND THE PRE HEAT & INTERPASS TEMPERATURE LIMITS (PROCEDURE QUALIFICATION AS PER ASME SECTION IX)
Parent - By G.S.Crisi (****) Date 05-08-2008 22:25
If the material is A 516 Gr 70 plate, chances are (great chances, I'd say) that it'll be used to make a pressure vessel. In this case, the applicable Code is ASME VIII. Depending on the pressure, it'll be Division I, II or III. If it's required impact at -29C, it means that the vessel will work at less than zero C temperatures. 
If the thickness is 35 mm, it'll definetely require preheat. I don't have the Code at hand, but I'd guess (guess, I repeat) that the preheat temperature will be about 150 C.
Now, mujibali, are you sure that a carbon steel plate 35 mm thick doesn't require PWHT? If I were you, I'd check and double check the Code.
Giovanni S. Crisi
Parent - By sea Date 05-13-2008 11:07
i think that PWHT has relation with p number (read b31.3 table PWHT° AFTER YOU CAN REFER TO  ASTM (ACORDONG YOUR MATERIAL° FOR DETRMINING  all what you need
don't forget asme section II  (SFA....) for determinig interpass temperature
and notion of carbon equivalent eq= c%+.......5FOR DETERMINIG T.PREHEATING BY USING CURVES)
i think that i give you key
Parent - - By G.S.Crisi (****) Date 05-07-2008 19:38
The preheat temperature for carbon steel material depends on the thickness. For a thickness of half an inch (12,7 mm) for example, it just need to be "warm to the hand", which in practice means about 35 - 40 °C.
For this reason, I don't agree with Inspector. Ambient temperature could be as high as plus 40 °C here in Brazil and as low as minus 40 °C in Alaska.
Applicable Codes in the USA and also here in Brazil:
Power plant piping: ASME B 31.1
Chemical plant and oil refinery piping: ASME B 31.3
Oil transportation: ASME B 31.4
Gas transmission and distribution: ASME B31.8
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By 3.1 Inspector Date 05-08-2008 04:44
OK,
I will reword it - so everybodt understand it
I dont expect anybody to weld at -40 degrees celcius!
Ambient temperature = 20-30 degrees in a workshop, in case your workshop is in Alaska and dont have any forms of heat
you will want to heat it to 20-30 degrees and drive the moist out - please dont make welding of CS into something its not.
If the coupon is above a certain thickness you will have to preheat it, I thought a certain knowledge was in place if you are about to make a PQR

J
Parent - By jon20013 (*****) Date 05-09-2008 09:35
As Professor Crisi indicates, it will be your constructing code that will specify both the preheat (either recommendation OR requirement) and PWHT, if required or exempted based on elevated preheat, in some cases.
Parent - By gwg (*) Date 05-19-2008 16:11
Preheat requirements are normally listed in the code of construction.
Parent - By sandip140 Date 05-31-2008 09:01
Please go through UCS-56 of ASME SEC VIII Div-1 . It describes 100 deg C preheating.
Up Topic Welding Industry / Metallurgy / PREHEAT TEMP REQUIREMENTS

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