3. Weld overlay

3.1 General Requirements.

If specified on the mechanical design drawings, an austenitic stainless steel overlay of either 347 or 317L shall be applied to the inside surface of the pressure vessels.

a. This overlay shall be comprised of two layers.

1) For reactors to be overlaid with 347 stainless steel, the first layer shall be applied with a 309L consumable, and the second layer with 347.

2) For reactors to be overlaid with 317L, the first layer shall be applied with a 309MoL consumable, followed by the second layer of 317L.

b. As an alternative, a single layer overlay may be used, provided technical data verifying the integrity of the overlay process is reviewed and accepted in writing by Purchaser.

3.2 Preheat and Heat Treatments During Weld Overlay

1. Base metal shall be preheated to 220°F (104°C) for the first layer of weld overlay.

2. Maximum interpass temperature shall be 480°F (250°C).

3. Provided that subsequent cooling in still air is completed, ISR and/or DHT may be omitted after overlay welding.

4. No preheating shall be required for the second and any subsequent layers of weld overlay.

3.3 Production Testing of Weld Overlay

3.3.1 Chemical Composition of Weld Overlay

1. Chemical composition of the weld overlay shall be checked by laboratory chemical

analysis of a sample taken at minimum specified thickness.

2. Composition shall meet the required chemistry of the specified overlay material

(C, Cr, Ni, Cb [Nb], Mo, and V, as applicable).

3. At least two analyses shall be required for each shell ring and head.

4. At least one location shall be checked for each nozzle and each Category A, B,

C, and D weld seam.

5. Portable nondestructive instruments may be used, but the procedures must submitted to Purchaser for review and acceptance.

3.3.2 Ferrite Content of Weld Overlay

1. Ferrite content of the deposited weld metal shall be determined before PWHT by a magnetic instrument calibrated according to AWS A4.2.

2. At least ten locations selected at random shall be checked for each shell ring and head. At least one location shall be checked at both ends of each nozzle and each Category A, B, C, and D weld seam.

3. All ferrite readings shall be between 3FN and 10FN.

Exercise 5. Decide if the statements are true or false:

1. Austenitic stainless steel overlay shall be comprised of three layers.

2. Minimum interpass temperature shall be 480°F (250°C).

3. Chemical composition of the weld overlay shall be checked by laboratory chemical analysis.

4. Composition shall meet the certain chemistry of the specified overlay material.

5. All ferrite readings shall be between 1FN and 10FN.

Exercise 6. Match two halves of the sentences:

1. For reactors to be overlaid with 347 stainless steel,	a. to 220°F for the first layer of weld overlay.
2. No preheating shall be required	b. to Purchaser for review and acceptance.
3. Base metal shall be preheated	c. with a 309MoL consumable, followed by the second layer of 317L.
4. Ferrite content of the deposited weld metal shall be determined	d. the first layer shall be applied with a 309L consumable, and the second layer with 347.
5. Portable nondestructive instruments may be used, but the procedures must submitted	e. for the second and any subsequent layers of weld overlay.
6. For reactors to be overlaid with 317L,	f. before PWHT by a magnetic instrument the first layer shall be applied calibrated according to AWS A4.2.

Exercise7. Translate the sentences into English:

1. Если имеются соответствующие указания на механических проектных чертежах, на внутреннюю поверхность аппаратов под давлением наносится наплавка из аустенитной нержавеющей стали 347 или 317L.

2. После выполнения наплавки допускается не проводить промежуточное снятие напряжений и/или дегидрогенизационную термообработку при условии, что выполнено охлаждение в неподвижном воздухе.

3. У каждого штуцера и каждого сварного соединения категории А, В, С и D проверку осуществляют, по меньшей мере, в одном месте.

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