ASME VIII Div. 1- 2 Joint Efficiency

Cairo Inspection Company

Eng. Ibrahim Eldesoky

ASNT –NDT-LEVEL III

ASME AUTHORIZED INSPECTOR

2 Cairo Inspection Company (CIC) Www. CIC-Egypt.com Eng. Ibrahim Eldesoky

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


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)


UG-27 Thickness of Shells Under

Internal Pressure

An efficiency value "E" applies only to shells

under internal pressure.

Shell in tension Shell in compression

Pressure


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.

Cairo Inspection Company (CIC) Www. CIC-Egypt.com Eng. Ibrahim Eldesoky 6

E = lowest efficiency of any joint in

the head; for hemispherical heads,

this includes head-to-shell joint compression tension Pressure

Convex Concave

UG-32 Formed Heads and

Sections,

Pressure on the Concave Side


Example: Vessel subject to internal pressure

Convex Head Concave Head

UG-32 Formed Heads and

Sections,

Pressure on the Concave Side


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.



(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.


Head attachment Category A joint

examples

any joint in a sphere hemi head to shell

Category B joint

Cylindrical

straight flange

(skirt) formed head other than hemi


(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


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.


Joint Types

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" backing left in place


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


Examples: Type 5, single full fillet lap joints

with plug welds

Plug Weld

Examples: Type 6,single full fillet lap joint

without plug welds


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.


(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


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


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.


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.


UW-12(a) Full Radiography

Use column (a) of Table UW-12, except when UW-

11(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 Hemi head


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


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


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



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

Hemi head



RT-3, when the complete vessel satisfies the spot

radiography rules of UW-11(b).

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

Hemi head

Formed head,

Other than

Hemi

Hemi head


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ASME VIII Div. 1- 2 Joint Efficiency

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