Prequalified external weld buildup for repairing internal thinning.

The method of using 𝐞𝐱𝐭𝐞𝐫𝐧𝐚𝐥 𝐰𝐞𝐥𝐝 𝐛𝐮𝐢𝐥𝐝𝐮𝐩 to 𝐫𝐞𝐩𝐚𝐢𝐫 𝐢𝐧𝐭𝐞𝐫𝐧𝐚𝐥 𝐭𝐡𝐢𝐧𝐧𝐢𝐧𝐠 in pressure vessels or pressure piping is accepted and described in 𝐀𝐒𝐌𝐄 𝐏𝐂𝐂-𝟐, 𝐀𝐫𝐭𝐢𝐜𝐥𝐞 𝟐𝟎𝟐. What makes this process 𝐩𝐫𝐞𝐪𝐮𝐚𝐥𝐢𝐟𝐢𝐞𝐝?

𝐈. 𝐈𝐧𝐭𝐫𝐨𝐝𝐮𝐜𝐭𝐢𝐨𝐧

  𝐄𝐱𝐭𝐞𝐫𝐧𝐚𝐥 𝐛𝐮𝐢𝐥𝐝𝐮𝐩 can be a highly effective solution for 𝐜𝐨𝐫𝐫𝐞𝐜𝐭𝐢𝐧𝐠 𝐢𝐧𝐭𝐞𝐫𝐧𝐚𝐥 𝐭𝐡𝐢𝐧𝐧𝐢𝐧𝐠 and restoring the 𝐦𝐞𝐜𝐡𝐚𝐧𝐢𝐜𝐚𝐥 𝐢𝐧𝐭𝐞𝐠𝐫𝐢𝐭𝐲 of equipment, provided it is implemented properly. It is important to note that this method is suited for general thinning issues and is not applicable to localized corrosion, such as pitting or crevice corrosion, or to cracks.

 For any welding repair, certain minimum requirements must be met:

𝐚) The deposited weld material must have a 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑡𝑒𝑛𝑠𝑖𝑙𝑒 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝐞𝐪𝐮𝐚𝐥 𝐭𝐨 𝐨𝐫 𝐠𝐫𝐞𝐚𝐭𝐞𝐫 than that of the base metal.

𝐛) The chemistry of the 𝐟𝐢𝐥𝐥𝐞𝐫 𝐦𝐞𝐭𝐚𝐥 𝐦𝐮𝐬𝐭 𝐦𝐚𝐭𝐜𝐡 the chemistry of the base metal.

𝐜) 𝐇𝐞𝐚𝐥𝐭𝐡, 𝐒𝐚𝐟𝐞𝐭𝐲, 𝐚𝐧𝐝 𝐄𝐧𝐯𝐢𝐫𝐨𝐧𝐦𝐞𝐧𝐭𝐚𝐥 (HSE) requirements must be strictly followed, especially when welding on equipment that is in operation.

• All technical 𝐝𝐞𝐭𝐚𝐢𝐥𝐬 regarding the design are outlined in 𝐀𝐒𝐌𝐄 𝐏𝐂𝐂-𝟐, 𝐀𝐫𝐭𝐢𝐜𝐥𝐞 𝟐𝟎𝟐. However, we want to emphasize that this repair process is considered 𝐩𝐫𝐞𝐪𝐮𝐚𝐥𝐢𝐟𝐢𝐞𝐝 (meaning it does not require engineering design) under certain conditions. For the process to be deemed 𝐩𝐫𝐞𝐪𝐮𝐚𝐥𝐢𝐟𝐢𝐞𝐝, all of the following conditions must be verified.

𝐈𝐈. 𝐏𝐫𝐞𝐪𝐮𝐚𝐥𝐢𝐟𝐢𝐞𝐝 𝐞𝐱𝐭𝐞𝐫𝐧𝐚𝐥 𝐰𝐞𝐥𝐝 𝐛𝐮𝐢𝐥𝐝𝐮𝐩 𝐟𝐨𝐫 𝐫𝐞𝐩𝐚𝐢𝐫𝐢𝐧𝐠 𝐢𝐧𝐭𝐞𝐫𝐧𝐚𝐥 𝐭𝐡𝐢𝐧𝐧𝐢𝐧𝐠.

 Let's denote 𝐓 as the 𝐝𝐞𝐬𝐢𝐠𝐧 𝐭𝐞𝐦𝐩𝐞𝐫𝐚𝐭𝐮𝐫𝐞, 𝐃 as the pipe's 𝐨𝐮𝐭𝐬𝐢𝐝𝐞 𝐝𝐢𝐚𝐦𝐞𝐭𝐞𝐫, 𝐭 as the 𝐧𝐨𝐦𝐢𝐧𝐚𝐥 𝐭𝐡𝐢𝐜𝐤𝐧𝐞𝐬𝐬, and 𝐮 as the 𝐫𝐞𝐦𝐚𝐢𝐧𝐢𝐧𝐠 𝐭𝐡𝐢𝐜𝐤𝐧𝐞𝐬𝐬. For other dimensions, please refer to the attached file.

• The repair process is considered 𝐩𝐫𝐞𝐪𝐮𝐚𝐥𝐢𝐟𝐢𝐞𝐝 under the following conditions: The component must be a 𝐬𝐭𝐫𝐚𝐢𝐠𝐡𝐭 𝐩𝐢𝐩𝐞 𝐬𝐞𝐜𝐭𝐢𝐨𝐧 (not an elbow, mitered joint, or TEE) and must meet 𝐚𝐥𝐥 of the following set of requirements.

1. 𝐓< 𝟔𝟓𝟎°𝐅 (𝟑𝟒𝟎°𝐂).

2. 𝐭 ≥ 𝑡ℎ𝑒 𝑙𝑒𝑠𝑠𝑒𝑟 of (𝐒𝐜𝐡𝐞𝐝𝐮𝐥𝐞 𝟒𝟎, 𝐒𝐭𝐚𝐧𝐝𝐚𝐫𝐝 𝐒𝐜𝐡𝐞𝐝𝐮𝐥𝐞).

3. The taper angle α ≤ 𝟑𝟎°.

4. The buildup metal geometry must be limited to 𝐜𝐢𝐫𝐜𝐮𝐥𝐚𝐫, 𝐨𝐯𝐚𝐥, or 𝐫𝐞𝐜𝐭𝐚𝐧𝐠𝐮𝐥𝐚𝐫 shapes.

5. The maximum dimension along the axis 𝐋:

 • 𝐋 ≤ the lesser of (𝐃 , 𝟖 𝐢𝐧),  [(𝐃 , 𝟐𝟎𝟎𝐦𝐦) ]

6. For rectangular and oval shapes, they must be oriented either 𝐩𝐚𝐫𝐚𝐥𝐥𝐞𝐥 or 𝐩𝐞𝐫𝐩𝐞𝐧𝐝𝐢𝐜𝐮𝐥𝐚𝐫 to the axis:

• For 𝐫𝐞𝐜𝐭𝐚𝐧𝐠𝐮𝐥𝐚𝐫 shapes, 𝐜𝐨𝐫𝐧𝐞𝐫𝐬 must be 𝐫𝐨𝐮𝐧𝐝𝐞𝐝 to a width equal to the 𝑏𝑢𝑖𝑙𝑑𝑢𝑝 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠.

• For oval shapes, the end 𝐫𝐚𝐝𝐢𝐢 must be greater than 𝟑/𝟒 √𝐑𝐭  of the buildup thickness.

7.  𝐖+ 𝐮 ≥ 𝐭.

8. The buildup thickness must be 𝐮𝐧𝐢𝐟𝐨𝐫𝐦, and the 𝐭𝐚𝐩𝐞𝐫𝐞𝐝 𝐞𝐝𝐠𝐞 must be properly formed.

9. If the building code requires a 𝐟𝐥𝐞𝐱𝐢𝐛𝐢𝐥𝐢𝐭𝐲 𝐚𝐧𝐚𝐥𝐲𝐬𝐢𝐬, the effect of the weld buildup must be 𝐫𝐞𝐜𝐨𝐧𝐜𝐢𝐥𝐞𝐝 𝐰𝐢𝐭𝐡 𝐭𝐡𝐞 𝐨𝐫𝐢𝐠𝐢𝐧𝐚𝐥 𝐚𝐧𝐚𝐥𝐲𝐬𝐢𝐬.

𝐀𝐥𝐭𝐞𝐫𝐧𝐚𝐭𝐢𝐯𝐞𝐥𝐲, 𝐚𝐧𝐞𝐧𝐠𝐢𝐧𝐞𝐞𝐫𝐢𝐧𝐠𝐝𝐞𝐬𝐢𝐠𝐧𝐰𝐢𝐥𝐥𝐛𝐞𝐫𝐞𝐪𝐮𝐢𝐫𝐞𝐝