How many thermocouples are required during PWHT?
For PWHT of pipe, what is the minimum requirement of Thermocouple with respect to diameter and according to which clause of the relevant Code/Standard. If one element is used to carry out PWHT of 4-6 scattered weld joints of small bore then only one thermocouple is sufficient OR not to represent all joints.
What is the use of thermocouple in PWHT?
Thermocouples are used for monitoring PWHT to assure heating rates, cooling rates, and hold temperature is within standard specifications.
What is PWHT requirement?
Post-weld heat treatment is applied to welded steel assemblies, primarily to reduce the likelihood of brittle fracture. PWHT is required where there is a risk of environmentally-assisted cracking. PWHT of C-Mn steels is typically carried out at approximately 600°C, for one hour per 25mm of thickness.
How do you calculate PWHT heat rate?
1) AB: Rate of heating: In WPS it is mentioned as a maximum value. In the graph the rate of heating is the slope of the curve AB. So the value of the slope should not be more than the value in WPS. slope = 80 / (1/2) = 160DegC/hr ; So in this graph the rate of heating is 160DegC/hr.
How many times PWHT can be done?
How many times PWHT is allowed to be done in one weld? and What is the impact on the weld and materia (mechanical/metallurgical properties) if multiple PWHT were done? Hoping to get feedback here as soon as possible. There is no limit, unless imposed by specification, for the number of PWHT’s imposed on a weld joint.
How do you calculate PWHT holding time?
For soaking time general thumb rule is 1 hour soaking time per ( 1 inch thick.) 25 mm thickness. Hence for 38 mm it should be 90 minutes. For 43 mm thick, it could be 2 hrs. or nearest….
| Active Contributor Join Date: May 2009 Location: India Posts: 19 | PWHT Holding Time |
|---|---|
| Login to Reply |
What is the minimum thickness for PWHT as per b31 3?
According to the ASME Section III requirements suggested in Table 1, PWHT for 12mm and 24mm thickness of pipes is not mandatory, but PWHT for 55mm thickness of pipe is mandatory.
What is the minimum thickness required for CS pipe which needs PWHT requirement?
(13 mm) or less that attach tubes to a tubesheet when the tube diameter does not exceed 2 in. (50 mm). A preheat of 200°F (95°C) minimum must be applied when the carbon content of the tubesheet exceeds 0.22%.
Is Pwht required for carbon steel?
1 carbon steel materials. In particular, PWHT is no longer a mandatory requirement for any wall thickness provided that multi-pass welding is employed for wall thicknesses greater than 5 mm (3/16 of an inch) and a minimum preheat of 95°C (200°F) is implemented for wall thicknesses greater than 25 mm (1 inch).
How many thermocouples are required for post weld heat treatment?
The minimum number of thermocouples attached per joint shall be 1 for up to 3″ diameter, 2 for up to 6″ diameter and 3 for up to 10″and 4 up to 12″diameter and above. However, the required minimum number of thermocouples to be attached can be increased if it found necessary.
Is there no.of thermocouples for PWHT?
The no. of thermocouple for PWHT, it is no written any where in the code but ones the procedure is approved, it should be follwed. if you whant change the no of thermocouple you can reverse the procedure.
When to attach thermocouple to pressure part or vessel?
It is stated in ASME sec VIII that it is mandatory to attach thermocouple to the pressure part or vessels when PWHT, if they are more than one part or vessel. In secI nothing is found about this matter. we want to PWHT the drums base on secI and vessels base on secVIII, in a calibrated furnace.
What are the minimum requirements for a thermocpuple, TC?
In all these arguments one imp aspect remains ignored, the very purpose of a thermocpuple, TC. All the requirements given in B31.3, Shell DEP, Aramco SP etc are the minimum requirements. What we have to ensure is that all the area required to be heat treated is indeed heated and soaked as specified.