ASME VIII Div. 1- 2 Joint Efficiency

Cairo Inspection Company Eng. Ibrahim Eldesoky ASNT –NDT-LEVEL III ASME AUTHORIZED INSPECTOR

Cairo Inspection Company (CIC)

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Eng. Ibrahim Eldesoky

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Session Objectives  Determine when to apply a joint efficiency "E" in pressure vessel design calculations.  Review and understand the terms joint "category“ and "type".  Determine the correct "E" value based on joint type and degree of radiography.  Review ASME stamping requirements when radiography is performed.  Solve sample problems


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Referenced Code Paragraphs  UG-27 Shells under internal under pressure.  UG-32 Formed heads, pressure on the concave side.  UW-3 Welded joint category.  Figure UW-3 Illustration of Welded Joint Location.  UW-12 Joint efficiencies  Table UW-12 Maximum allowable joint efficiencies  UG-116(e) Required marking (nameplates or direct stamping) Cairo Inspection Company (CIC)

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UG-27 Thickness of Shells Under Internal Pressure An efficiency value "E" applies only to shells under internal pressure.

Pressure Shell in tension Cairo Inspection Company (CIC)

Shell in compression Www. CIC-Egypt.com


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E = joint efficiency for, or the efficiency of appropriate joint in cylindrical or spherical shells, or the efficiency of ligaments between openings, whichever is less.


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UG-32 Formed Heads and Sections, Pressure on the Concave Side E = lowest efficiency of any joint in the head; for hemispherical heads, this includes head-to-shell joint

tension

Pressure

Concave Cairo Inspection Company (CIC)

compression

Convex Www. CIC-Egypt.com


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UG-32 Formed Heads and Sections, Pressure on the Concave Side Example: Vessel subject to internal pressure

Convex Head Cairo Inspection Company (CIC)

Concave Head Www. CIC-Egypt.com


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The term Category as used herein defines the location of a joint in a vessel, but not the type of joint.  Categories are assigned based on the type and degree of stresses imposed at various locations within a vessel.  Joints included in each category are designated as A, B, C or D. 


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 (a) Category A  Longitudinal joints within the main shell, communicating chambers (eg. sumps), transitions in diameter, or nozzles,  any joint in a sphere, formed or flat head or side plates in flat sided vessels,  circumferential welded joints connecting hemispherical heads to shells, nozzles, or to communicating chambers.  (b) Category B  Circumferential welded joints within the main shell, communicating chambers or transitions in diameter,  circumferential welded joints connecting formed heads other than hemispherical to main shells, transitions in diameter, to nozzles, or to communicating chambers.


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 Head attachment

Category A joint

examples any joint in a sphere

Cylindrical straight flange (skirt)

hemi head to shell Category B joint

formed head other than hemi


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(c) Category C  Welded joints connecting flanges, Van Stone laps, tube sheets, or flat heads to:  main shells, to formed heads,  to transitions in diameter, to nozzles or to communicating chambers,  Any welded joint connecting one side plate to another side plate of a flat sided vessel. (d) Category D  Welded joints connecting communicating chambers or nozzles to: main shells, spheres, transitions in diameter, to heads, flat sided vessels, and nozzles to communicating chambers Cairo Inspection Company (CIC)

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Joint Types  8 Joint types are identified.  Type 1 has the highest efficient, type 6 has the lowest efficient. Types 7 and 8 have no assigned efficiency.  Types 1 through 3 are butt joints, types 4 through 6 are lap joints. Type 7 is a corner joint and 8 is an angle joint. Only type 1 and 2 butt joints may be radiographed in order to improve efficiency.


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Examples: Type 1, Butt welded, both sides must be visible

Examples: Type 2, butt welded with backing

Fig. UW-13.1 sketch (k) "joggle joint" Cairo Inspection Company (CIC)

backing left in place

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Examples: Type 3, single welded butt welded without backing

not viewed internally -eg. small diameter pipe or assemblies with space or visibility restrictions Examples: Type 4, double full fillet lap joint


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Examples: Type 5, single full fillet lap joints with plug welds

Plug Weld Examples: Type 6,single full fillet lap joint without plug welds


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UW-12 Joint Efficiencies Table UW-12 gives the joint efficiencies "E" to be used in the formulas of this Division for joints completed by gas or an arc welding process. Except as required by UW-11(a)(5), a joint efficiency depends only on the type of joint and the degree of examination of the joint and doesn't depend on the degree of examination of any other joint.  The user or his designated agent [U-2(a)] shall establish the type of joint and the degree of examination when the rules of this Division do not mandate specific requirements. Cairo Inspection Company (CIC)

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(a) full radiography (b) spot radiography (c) no radiograph (d) seamless pressure vessel sections and heads (e) welded pipe or tubing (f) welds completed by pressure welding processes Cairo Inspection Company (CIC)

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 UW-12(b) Spot radiography  Per column (b) of Table UW-12  Performed per UW-52* [see UW-11(b)]

* Minimum one film (at least 6 inches long) per welder for each 50 foot increment of deposited weld metal.

 UW-12(c) No Radiography  Per column (c) of Table UW-12


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 UW-12(f) Pressure Welding Processes  A value of E not greater than 0.80 for welds completed by any of the pressure welding processes listed in UW-27(a).

 UW-12( a) Full Radiography  Use the efficiency specified in column (a) of Table UW12, except when the requirements of UW-11(a)(5) are not met, a value not greater than that listed in column (b) of Table UW-12 shall be used. Cairo Inspection Company (CIC)

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 UW-11(a)(5) applies to all Category A or D butt welds in vessel sections and heads designed per UW-12(a), in which case:  (a) Category A and B welds connecting vessel sections or heads shall be Type 1 or 2 of Table  (b) Category B or C butt welds which intersect category A butt welds in vessel sections or heads, or connect seamless vessel sections or heads shall as a minimum, meet the requirements for spot radiography per UW 2.  UW-52(b)(4) Radiographs required at specific locations to satisfy the rules of other paragraphs, such as UW-9(d), UW11(a)(5)(b). and UW-14(b), shall not be used to satisfy the rules for spot radiography. Cairo Inspection Company (CIC)

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 UW-12(a) Full Radiography  Use column (a) of Table UW-12, except when UW11(a)(5) is not met, use column (b) of Table UW-12.

 UW 12(d) Seamless Vessel Sections and Heads  are considered equivalent to welded parts of the same geometry, in which and all Category A welds are type 1.

Formed head other than hemi Cairo Inspection Company (CIC)

Hemi head Www. CIC-Egypt.com


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UW-12(d) can't... For calculations involving circumferential stress in vessel sections or for the thickness of seamless heads, E = 1.0 when the spot radiography requirements of UW 11(a) (5)(b) are met, or 0.85 when they are not met.

Formed head other than hemi

Hemi head

UW-11(a)(5)(b) spot RT performed, E= 1.0 UW-11(a)(5)(b) spot RT not met, E= 0.85


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UW-12(e) Welded pipe or tubing* shall be treated in the same manner as seamless, but with the allowable tensile stress taken from the welded product values of the stress tables, and the requirements of UW-12(d) applied. * Manufactured in accordance with a material specification permitted by this Division, not fabricated by the vessel manufacturer as a vessel part. (eg. ERW pipe)

Welded, but treated like seamless [UW-12(d)]

UW-11(a)(5)(b) spot RT performed, E= 1.0 UW-11(a)(5)(b) spot RT not met, E= 0.85 Cairo Inspection Company (CIC)

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UG-116(e) Required Marking  When a vessel has been radiographed in accordance with UW-11, marking shall be applied under the Code symbol

as follows:  RT-1  RT-2  RT-3  RT-4


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UG-116(e) Required Marking RT-l, Full radiography of all pressure retaining butt welded joints, except Category B & C butt welds in nozzles and communicating chambers that neither exceed IMPS 10 (DN 250) nor 1-1/8 in. (29mm).

RT-2,

when the complete vessel satisfies the requirements of UW 11(a)(5) and when spot RT rules of UW 11(a)(5)(b) have been applied.

Formed head, Other than Hemi Cairo Inspection Company (CIC)

Hemi head

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UG-116(e) Required Marking RT-3,

when the complete vessel satisfies the spot radiography rules of UW-11(b). Formed head, Other than Hemi

Hemi head

RT-4, when only part of the complete vessel has satisfied the radiographic requirements of UW-11(a) or where none of the markings RT-1, RT-2, or RT 3 are applicable Formed head, Other than Hemi Cairo Inspection Company (CIC)

Hemi head

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ASME VIII Div. 1- 2 Joint Efficiency

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