impact testing requirements

Impact TestingDetermination

ASME Section VIII,

Division 1

Impact Testing Determination

o Failure of materials and fabricated assemblies can occur In one oftwo ways:

Ductile or Brittle

o ASME impact testing rules determine ability to resist brittle failure.

Characteristics Affecting Resistance To Brittle Failureo Mechanical properties and chemical composition of:

Base material , Weld material, Weldmentso Thicknesso Applied Stress

o Metal Temperature

o Impact testing is required unless exempted by Code.

o Requirements for IT exemptions are described in Subsection Cfor a given class of material.

o Exemptions may appear either directly in Code paragraphs, or byparagraph reference to Code figures and notes.

ASME Code Rules

o When not exempted, impact testing shall be by the charpy V notchtesting method & shall meet the requirements of UG-84 whichmay include testing of:

materials, including welding material,PQR materialweldments fabrications

UG - 84 Addresses:

(a) general

(b) test procedures

(c) test specimens

(d) IT of materials

(e) procedural requirements

(f) IT of welds

(g) specimen location, orientation, testing temperature andacceptance values

(h) IT of PQR specimens

(i) Vessel (Production) IT test plates

(j) rejection

ASME Code Rules

o Rules for the performance of impact testing appear in UG-84.I.T. procedures and apparatus shall conform to 5A-370.Calibration of IT. Equipment calibration shall be performed in accordance

with ASTM E23.

Charpy V Notch Impact Testing Method

Principles of the Charpy V Notch Method

The height to which the pendulum rises in its swing after breaking the specimenis measured and used to determine the residual energy of the pendulum. Thespecimen is supported horizontally as a simple beam with the axis of the notchvertical. It is struck in the middle of the face opposite the notch.

SA-370, 21.1.1: A charpy impact machine isone in which a notched specimen is brokenby a single blow of a freely swingingpendulum. The pendulum is released from afixed height so that the energy of the blow isfixed and known.


Fig. UG-84 Simple Beam Impact

Test Specimens (Charpy

Type Test)

O = original width before breakF = final width after break

NNotch Original cross section

Determining Lateral Expansion

o One "set" is composed of 3 specimenso Specimens are tested at or below the MDMT of

the vessel.o Testing determines

• Ft/lb's of force required to break thespecimens,

• lateral expansion (mils), measured afterbreaking,

• brittle or ductile fracture.


Section VIII, Div. 1Flow Diagram for

Determining Impact Testing Exemptions

o UG-20(f) Impact testing per UG-84 is not mandatory for pressure vessel

materials which satisfy all of the following.(1) The material shall be limited to P-No. 1, Gr. No. 1 or 2, and the

thickness, as defined in UCS-66(a) [see also General Note (1) in Fig.UCS-66.2], shall not exceed that given in (a) or (b) below:

(a) 1 / 2 in. (13 mm) for materials listed in Curve A of Fig. UCS-66;(b) 1 in. (25 mm) for materials listed in Curve B, C, or D of Fig. UCS-66.(2) The completed vessel shall be hydrostatically tested per UG-99(b)

or (c) or 27-4.(3) Design temperature is no warmer than 650°F (345°C) nor colder

than −20°F (−29°C). Occasional operating temperatures colder than−20°F (−29°C) are acceptable when due to lower seasonalatmospheric temperature.

Thermal or mechanical shock loadings are not a controlling designrequirement, cyclical loading is not a controlling designrequirement.22

Exemptions by Code Paragraph

UCS-66 Materials

o (a) Figure UCS-66 shall be used to establish impact testingexemptions for steels listed in Part UCS.

o Unless otherwise exempted by the rules of this Division, impacttesting is required for a combination of minimum design metaltemperature (MDMT) and thickness which is below the curveassigned to the subject material.

o If a MDMT and thickness combination is on or above the curve,impact testing is not required by the rules of this Division,except as required by:

UCS-66Q), and UCS-67(a)(2)o Pressure parts shall be evaluated as separate components (e.g.,

Shells, heads, nozzles, manways, reinforcing pads, flanges,tube sheets, flat cover plates, backing strips [remaining inplace] and attachments essential to the structural integrity ofthe vessel when welded to the pressure containing component).

o UCS-66(a) continued... Each Component shall be evaluatedfor impact test requirements based on its individualmaterial:

ClassificationThicknessMDMT

UCS-66 Materials

Governing Thickness UCS-66(a)(1)

o The following thickness limitations apply when using Fig. UCS-66.Excluding castings, the governing thickness (tg)of a welded partis as follows:

o(a)(l)(a) For butt joints (except those in flat heads andtubesheets), the nominal thickness of the thickest welded joint[see Fig. UCS-66.3, sketch (a)],

o(a)(l)(b) For corner, fillet or lap welded joints, includingattachments, the thinner of the two parts joined,

O(a)(l)(c) For flat heads or tubesheets, the larger of (b) above orthe component thickness divided by four,

O(a)(l)(d) for welded assemblies comprised of more than twocomponents (e.g., nozzle-to-shell joint with reinforcing pad), tand MDMT of the individual welded joints of the assembly shallbe determined, and the warmest of the MOMTs shall be used asthe MDMT of the welded assembly, [see Figure UCS-66.3,sketch (b)]


o If the governing thickness at any welded joint exceeds 4 inchesand the MDMT is colder than 120°F (49° C), impact testedmaterial shall be used.

o (4) The governing thickness of a nonwelded dished head [Fig. 1-6sketch (c)] \s the greater of the flat flange thickness divided by 4or the minimum thickness of the dished portion.

o (5) If the Governing thickness of a nonwelded part exceeds 6inches (152 mm) and the minimum design temperature is colderthan 120°F (49°C), impact tested material shall be used.


o (2) The governing thickness of a casting shall be its largestnominal thickness.

o (3) The governing thickness of flat nonwelded parts, such asbolted flanges, tubesheets, and flat heads, is the flat componentthickness divided by four.

o (b) When the coincident ratio defined in Fig. UCS-66.1 is less thanone, Figure UCS-66.1 provides a basis for the use of componentsmade of Part UCS materials to have a colder MDMT than thatderived from UC5-66(a) without impact testing.

UCS-66(b), Reduction In MDMT WithoutImpact Testing

o (b)(l)(a) For such components, and for a MDMT of -55°F (-48°C) andwarmer, the MDMT without impact testing determined in (a) abovefor the given material and thickness may be reduced as determinedby Fig, UCS-66.2.

o If the resulting temperature is colder than the required MDMT,impact testing of the material is not required.

o (b)(l)(b) Fig. UCS-66.1 may also be used for components notstressed in general primary membrane tensile stress (defined inAppendix 3).

o (b)(l)(c) In lieu of using (b)(l)(b), the MDMT determined in UCS-66(a) or (c) may be reduced for a flange attached by welding, bythe same reduction as determined in (b)(l)(b) for the neck or shellto which the flange is attached.

UCS-66(b), Reduction In MDMT WithoutImpact Testing

o (b)(2) For minimum design temperatures colder than -55°F (-48°C), impact testing is required for all materials, except asallowed in (b)(3) and in UCS-68(c).

o (b)(3) When the MDMT is colder than -55°F (-48°C) and no colderthan -155°F (-104°C), and the coincident ratio (Fig. UCS 66.1) is< 0.35, impact testing is not required.

o If postweld heat treating is performed when it Is not otherwise arequirement of this Division, a 30°F (17°C) reduction in theimpact testing exemption temperature may be given to theminimum permissible temperature from Fig. UC5-66 for P-No. 1materials. The resulting exemption temperature may be colderthan -55°F (-48°C).

UCS-68(c) Exemption when PWHT is Performed

o No impact testing is required for the following flanges whenused at MDMTs no colder than -20°F (-29°C):

(1) ASME B16.5, ferritic steel(2) ASME B16.47, ferrltic steel(3) split loose flanges using SA-216 GR WCB(4) Carbon and low alloy steel long weld neck flanges

o Unless specifically exempted in Fig. UCS-66, materials having aspecified minimum yield strength greater than 65KSI (448MPa)must be impact tested.

UCS-66(f), Impact Testing Based On YieldStrength

UCS-66(g), Material Specification Impact Testing

o Materials produced and impact tested in accordance with therequirements of the specifications listed in Fig. UG-84, GeneralNote (c), are exempted from impact testing by the rules of thisDivision at MDMTs of not more than 5°F (3°C) colder than thetemperatures required by the specifications.

o No impact testing is required for metal backing strips which remainin place made of materials:

assigned to Curve A of Fig. UCS-66;with thicknesses not exceeding 1/4 inch (6.3 mm);and the MDMT is -20°F (-29°C) and warmer.

UCS-66(h), Exemptions for Metal BackingStrips

UCS-66(i), Part UCS Impact Tested Materials

o Fig. UCS-66.1 provides a basis for the use of impact testedmaterial at MDMTs colder than the IT. temperatures, provided thecoincident ratio (Fig. UCS-66.1) \s less than one and the MDMT \snot colder than -155°F (-104°C).

(1) For such components, the MDMT shall not be colder than theimpact test temp, less the allowable temp, reduction as determinedfrom Fig. UCS-66.2.

o When the base metal Is exempted from impact testing by UCS-66(g)(material specification required IT.), Or by Fig. UCS-66 CurvesC or D, -20°F (-29°C) is the coldest MDMT to be assigned forwelded components that do not meet the requirements of UCS-67(a)(2) [SFA material classed by IT. at a temperature not warmerthan the MDMT].

UCS-66(j), Base Metal Exemptions

UCS-67, Impact Testing Of Welding Procedures

o Except as exempted in UG-20(f), the Welding ProcedureQualification shall include impact tests of the welds and heataffected zones (HAZ) made in accordance with UG-84 whenrequired by the following provisions:

o The MDMT used below shall be that stamped on the nameplate orthe exemption temperature of the welded component beforeapplying the temperature reduction permitted by: UCS-66(b) [reduction in MDMT based on material thickness ratio] UCS-68(c).[non-mandatory PWHT]

o UCS-67(a) Welds made with filler metal shall be impact tested inaccordance with UG-84 when any of the following apply:

(a)(l) when either base metal is required to be impact tested by therules of this Division,

(a)(2) when joining base metals exempt from impact testing by UCS-66(g) or Fig. UCS-66 Curve C or D and the MDMT is colder than -20°F (-29°c) but not colder than -55°F (-48°C), unless the weldingconsumables which have been classified by impact tests at atemperature not warmer than the MDMT by the applicable SFAspec. are used; or

(a)(3) when joining base metals exempt from impact testing by UCS-66(g) [materials produced and impact tested LAW the materialspecification] when the MDMT is colder than -55°F (-48°C).


o UCS-67(b) Welds in UCS Materials made without the use of fillermetal shall be impact tested when the thickness of the weld exceeds

1/2 inch (13mm) for all MDMTs; orwhen the thickness of the weld exceeds 5/16 inch (8mm) and the

MDMT is colder than 50°F (10°C).o This requirement does not apply to welds made as part of the

material specification.


o UCS-67(c) Weld heat affected zones produced with or without theaddition of filler metal shall be impact tested whenever any of thefollowing conditions apply:

(c)(l) when the base metal is required to be impact tested,(c)(2) when the welds have any individual pass exceeding 1/2

inch (13mm) and the MDMT is colder than 70°F (21°C): or(c)(3) when joining base metals exempted by UCS-66(g) when

the MDMT \s colder than -55°F (-48°C)

o UCS-67(d) Vessel (production) impact tests made in accordancewith UG-84(i) may be waived for any of the following:

(d)(l) weld metals joining steels exempted from impacttesting by UC5-66 for MDMTs of -20°F (-29°C) andwarmer: or


(d)(2) weld metals defined in (a)(2) above; or(d)(3) heat affected zones (HAZ) in steels exemptedfrom impact testing by UCS-66, except when (c)(3)above applies.

impact testing requirements

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