ASME BPVC.VIII.

1-2021 UCS-66 – UCS-67

(1) The materials shall be limited to P‐No. 1 Gr. Nos. 1 of maximum design pressure at the MDMT to the maxi-
and 2. mum allowable pressure (MAP) of the component at the
(2) The minimum nominal plate thickness shall be MDMT.
3 (3) In lieu of using (2) above, the MDMT for a flange
/16 in. (5 mm), or the minimum nominal pipe wall thick-
ness shall be 0.154 in. (3.91 mm). attached by welding shall not be colder than the impact
(3) The minimum design metal temperature shall be test temperature less the allowable temperature reduc-
no colder than −20°F (−29°C). tion as determined in (1) above for the neck or shell to
which the flange is attached.
(f) Materials, other than bolting materials, having a
(4) The requirements of (b)(1)(-d) shall be met.
specified minimum yield strength greater than 65 ksi
(450 MPa) shall be impact tested. However, they may (5) The MDMT adjustment as determined in (1)
be used at temperatures colder than the minimum design above may be used for impact tested welding procedures
metal temperature as limited in (1) and (2) below. or production welds.
(1) When the coincident ratio defined in Figure (6) The MDMT for the component shall not be colder
UCS-66.1 (Figure UCS-66.1M) is 0.35 or less, the corre- than −155°F (−105°C).
sponding minimum design metal temperature shall not (j) When the base metal is exempt from impact testing
be colder than –155°F (–104°C). by (g) above or by Figure UCS-66 (Figure UCS-66M),
Curve C or Curve D, −20°F (−29°C) is the coldest MDMT
(2) When the coincident ratio defined in Figure
to be assigned for welded components that do not meet
UCS-66.1 (Figure UCS-66.1M) is greater than 0.35, the
the requirements of UCS-67(a)(3).
corresponding minimum design metal temperature shall
not be colder than the impact test temperature less the al-
lowable temperature reduction permitted in Figure UCS-67 IMPACT TESTS OF WELDING
UCS-66.1 (Figure UCS-66.1M) and shall in no case be PROCEDURES
colder than –155°F (–104°C).
Except as exempted in UG-20(f), UCS-66, and UCS-68,
(g) Materials produced and impact tested in accor- the welding procedure qualification shall include impact
dance with the requirements of the specifications listed tests of the weld metal and heat-affected zones (HAZ) in
in Figure UG-84.1 (Figure UG-84.1M), General Note (c), accordance with UG-84 when required by the following
are exempt from impact testing by the rules of this Divi- provisions. The minimum design metal temperature
sion at minimum design metal temperatures not more (MDMT) used below shall be either the MDMT stamped
than 5°F (3°C) colder than the test temperature required on the nameplate or the exemption temperature of the
by the specification. welded component before applying the temperature re-
(h) No impact testing is required for metal backing duction permitted by UCS-66(b) or UCS-68(c).
strips which remain in place made of materials assigned (a) Welds made with filler metal shall be deposited
to Curve A of Figure UCS-66 (Figure UCS-66M) in thick- using welding procedures qualified with impact testing
nesses not exceeding 1/4 in. (6 mm) when the minimum in accordance with UG-84 when any of the following
design metal temperature is −20°F (−29°C) or warmer. apply:
(i) For components made of Part UCS materials that (1) when either base metal is required to be impact
are impact tested, Figure UCS-66.1 (Figure UCS-66.1M) tested by the rules of this Division; or
provides a basis for the use of these components at an (2) when the thickness of any individual weld pass
MDMT colder than the impact test temperature. For pres- exceeds 1/2 in. (13 mm) and the MDMT is colder than
sure vessel attachments that are exposed to tensile stress- 70°F (21°C); or
es from internal pressure (e.g., nozzle reinforcement
(3) when joining base metals exempt from impact
pads, horizontal vessel saddle attachments, and stiffening
testing by UCS-66(g) or Figure UCS-66 (F igur e
rings), the coincident ratio shall be that of the shell or
UCS-66M), Curve C or D and the MDMT is colder than
head to which each component is attached.
−20°F (−29°C) but not colder than –55°F (–48°C). Qualifi-
(1) For such components, the MDMT shall not be cation of the welding procedure with impact testing is not
colder than the impact test temperature less the allow- required when no individual weld pass in the production
able temperature reduction as determined from Figure weld exceeds 1/4 in. (6 mm) in thickness; and each heat
UCS-66.2. and/or lot of filler metal or combination of heat and/or
(2) Figure UCS-66.1 (Figure UCS-66.1M) may also be lot of filler metal and batch of flux has been classified
used for components not stressed in general primary by their manufacturer through impact testing per the ap-
membrane tensile stress, such as flat heads, covers, tube- plicable SFA specification at a temperature not warmer
sheets, and flanges. The MDMT shall not be colder than than the MDMT. Additional testing beyond the scope of
the impact test temperature less the allowable tempera- the SFA specification may be performed by the filler metal
ture reduction as determined from Figure UCS-66.2. The and/or flux manufacturer to expand their classification
ratio used in Step 3 of Figure UCS-66.2 shall be the ratio for a broader range of temperatures; or

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