Originally Posted by sameercnn
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Refer to 2007 ASME BPVC SECT VIII DIV. 2 add. 2008a
sect 18.104.22.168 Required Impact Testing Based On the MDMT* Thickness* and Yield Strength
a) If the governing thickness (see paragraph 22.214.171.124.b) at any welded joint or of any non-welded part exceeds 100 mm (4 in.) and the MDMT is colder than 32°C (90°F)* then impact testing is required.
b) Unless specifically exempted in Figure 3.7 for parts not subject to PWHT or Figure 3.8 for parts subject to PWHT and for non-welded parts* materials having a specified minimum yield strength greater than 450 MPa (65 ksi) shall be impact tested.
126.96.36.199 Exemption from Impact Testing Based On the MDMT* Thickness* and Material Specification
a) Figure 3.7 for parts not subject to PWHT or Figure 3.8 for parts subject to PWHT shall be used to establish impact testing exemptions based on the impact test exemption curve for the subject material specification and grade or class of the steel* MDMT* and governing thickness of a welded part. If an MDMT and thickness combination for the subject material is on or above the applicable impact test
exemption curve in Figure 3.7 or Figure 3.8* then impact testing is not required except as required by paragraph 3.11.8 for weld metal and heat affected zones.
b) The governing thickness* g t * of a welded part is determined using the following criteria. Examples of the governing thickness for some typical vessel details are shown in Figures 3.9* 3.10* and 3.11.
1) For all product forms except castings:
i) For butt joints except those in flat heads and tubesheets* the nominal thickness of the thickest
welded joint [see Figure 3.9* sketch (a)]*
ii) For corner* fillet* or lap welded joints* including attachments as defined in paragraph 188.8.131.52*
the thinner of the two parts joined*
iii) For flat heads or tubesheets* the larger of paragraph (ii) above or the flat component thickness
divided by 4.
2) The governing thickness of a casting shall be its largest nominal thickness.
3) The governing thickness of flat nonwelded parts* such as bolted flanges* tubesheets* and flat heads* is the flat component thickness divided by 4.
4) The governing thickness of a nonwelded dished head is the greater of the flat flange thickness divided by 4 or the minimum thickness of the dished portion.
c) Components such as shells* heads* nozzles* manways* reinforcing pads* stiffening rings* flanges* tubesheets* flat cover plates* backing strips* and attachments that are essential to the structural integrity
of the vessel when welded to pressure retaining components shall be treated as separate components.
Each component shall be evaluated for impact test requirements based on its individual material
classification* governing thickness (see paragraph 184.108.40.206.b)* and the MDMT. For welded assemblies
comprised of more than two components (e.g.* nozzle-to-shell joint with reinforcing pad)* the governing
thickness and permissible MDMT of each of the individual welded joints of the assembly shall be
determined* and the warmest MDMT shall be used as the permissible MDMT of the welded assembly.
d) Figure 3.7 limits the maximum nominal governing thickness for welded parts not subject to postweld
heat treatment to 38 mm (1-1/2 in.). Some vessels may have welded non-postweld heat treated
pressure parts whose thickness exceeds the nominal governing thickness of 38 mm (1-1/2 in.).
Examples of such welded and non-post heat treated pressure parts are thick tubesheets* flat heads* and
thick insert plates (with beveled edges) with nozzles or load carrying structural attachments. Such
welded non-postweld heat treated pressure parts shall be impact tested and shall meet the impact test
requirements of this Division.
e) Impact testing is not required for materials with a thickness of 2.5 mm (0.099 in.) and thinner* but such
exempted materials shall not be used at design metal temperatures colder than -48°C (-55°F). For
components made from DN 100 (NPS 4) pipe or smaller and for equivalent size of tubes of P-No. 1
materials* the following exemptions from impact testing are also permitted as a function of the specified
minimum yield strength (SMYS) of the material for metal temperatures of -104°C (-155°F) and warmer:
1) For SMYS between 140 - 240 MPa (20 -35 ksi)* inclusive* the thickness exemption for impact
testing is 6 mm (1/4 in.).
2) For SMYS between 250 - 310 MPa (36-45 ksi)* inclusive* the thickness exemption for impact
testing is 3.2 mm (1/8 in.).
3) For SMYS higher than 315 MPa (46 ksi)* inclusive* the thickness exemption for impact testing is
2.5 mm ( 0.099 in.).
f) Note that the rules in this paragraph for the exemption of impact testing do not provide assurance that
all test results for these materials will satisfy the impact test acceptance criteria of paragraph 220.127.116.11.b.
18.104.22.168 Exemption from Impact Testing Based On Material Specification and Product Form
a) Impact testing is not required for the ferritic steel flanges shown below when supplied in heat treated condition (normalized* normalized and tempered* or quenched and tempered) and used at design
temperatures no colder than -29oC (-20oF) and no colder than -18oC (0oF) when supplied in the as forged condition:
1) ASME B16.5 flanges*
2) ASME B16.47 flanges*
3) Long weld neck flanges* defined as forged nozzles that meet the dimensional requirements of a flanged fitting given in ASME B16.5 but have a straight hub/neck. The neck inside diameter shall not be less than the nominal size of the flange* and the outside diameter of the neck and any nozzle reinforcement shall not exceed the diameter of the hub as specified in ASME 16.5.
I hope these paragraph will help you*