SUBSECTION B

SUBSECTION B 

REQUIREMENTS PERTAINING 

TO METHODS OF FABRICATION 

OF PRESSURE VESSELS 

My Self Study Note 

Fion Zhang/ Charlie Chong 

Sub-B

PART UW 

REQUIREMENTS FOR PRESSURE VESSELS 

FABRICATED BY WELDING. 


UW

PART UW 

Overview 


UW

Vessel 

Service limitations? UW-2 

How ASME-UW works: 

Joint type, UW-12 type 1~8 

RT UW-11 

Joint efficiencies, E 

Joint Categories 

UW-3 

A vessel is to be built, next is to determine the intent of the vessel (UW-2), UW-2 set 

the limitations on type of joints, and the NDT requirements. Next proceed to UW-12, 

UW-12 provide a combinations of joint categories and extents of radiographic testing 

which give the value “E”, the joint efficiency. 


UW

Type 

number 

Joint description 

Limitations 

Joint 

Categories 

Degree of Radiographic 

Examination. 

Full 

Spot 

None 

1 

•Butt joints as attained by 

double-welding or by other 

means which will obtain the 

same quality of deposited weld 

metal on the inside and outside 

weld surfaces to agree with the 

requirements of UW-35. Welds 

using metal backing strips 

which remain in place are 

excluded. 

A, B, C & D 

1.00 

0.85 

0.7 

2 

•Single-welded butt joint with 

backing strip other than those 

included under (1) 

(a) None except as in 

(b) below 

(b) Circumferential 

butt joints with 

one plate offset; 

see UW-13(b) 

(4) and Fig. 

UW-13.1, sketch 

(i) 

A, B, C & D 

A, B & C 

0.90 

0.90 

0.80 

0.80 

0.65 

0.65 


UW

ASME design codes are built around the 

idea of a joint efficiency factor denoted 

by the symbol “E”. The factor “E” 

appears in the internal pressure 

equations and depends on: 

• The amount of NDE carried out on the 

weld. 

• The weld joint arrangement (single or 

double groove, etc.). 


UW

UW-2 SERVICE RESTRICTIONS. 


UW-02

UW-2 gives guidance on which types of pressure vessels / parts have 

restrictions on what type of weld should be used for each joint category. 

The four types of vessels referenced are: 

(a) Vessels for lethal service (containing a lethal substance). 

(b) Low-temperature vessels that require impact testing. 

(c) Unfired steam boilers. 

(d) Direct-fired vessels. 


UW-02

UW-2 SERVICE RESTRICTIONS 

Class 

a 

b 

c 

d 

Description. 

vessels are to 

contain lethal 

substance. 

Low-temperature 

vessels that require 

impact testing 

Unfired steam boilers 

Direct-fired vessels 

Service restrictions 

Following key points: 

• Butt-welded joints must be fully radiographed. 

• Carbon or low alloy steel vessels need PWHT. 

• Cat “A” joints need to be type 1(double “V” or 

equivalent) welds (the types are given in table 

UW-12). 

• Cat B joints can be either type 1 or type 2 (single 

“V” with backing strip). 

• Cat D joints must be full penetration welds. 


UW-02

Lethal 

service 

Cat. C 

Cat. B 

Cat. D 

Cat. A 


UW-2

UW-2 

Class 

a 

Description. 

Vessels are 

to contain 

lethal 

substance. 

Service restrictions 

Following key points: 

1. Butt-welded joints must be fully radiographed. 

2. Carbon or low alloy steel vessels need PWHT. 

3. Cat A joints need to be type 1 welds (double 

welded) (the types are given in table UW-12). 

4. Cat B joints can be either type 1 or type 2 

(single welded - single V with backing strip). 

5. Cat D must be full penetration welds 

.* note1 

Note1: For radiography joints only type 1 & 2 

are allowed. 


UW-02

UW-3 WELDED JOINT CATEGORY. 


UW-03

WELDED JOINT CATEGORY 

ASME VIII pressure vessel welded joints are given a letter 

designation A, B, C or D depending on their location in the 

vessel. 


UW-03

FIG. UW-3 ILLUSTRATION OF WELDED JOINT LOCATIONS 

TYPICAL OF CATEGORIES A, B, C, and D 


UW-03

• Cat “A” includes all longitudinal welds and critical circumferential 

welds such as hemispherical head to shell welds. 

• Cat “B” includes most circumferential welded joints including 

formed heads (other than hemispherical) to main shells welds. 

• Cat “C” includes welded joints connecting: . flanges to nozzles or 

shell components. one side plate to another in a flat-sided vessel. 

• Cat “D” includes welded joints connecting nozzles to shells, heads 

or flat-sided vessels. 


UW-03

• Cat A includes all longitudinal welds and critical 

circumferential welds such as hemispherical head to shell 

welds. 


UW-03

Non-hemispherical 

head 

Critical Circumferential weld: 

Hemispherical head 


UW-03

A 

Hemispherical 

Heads 

A 

Critical Circumferential weld: 

A 


UW-03

• Cat B includes most circumferential welded joints including 

formed heads (other than hemispherical) to main shells welds. 


UW-03

• Cat C includes welded joints connecting: . flanges to nozzles or 

shell components. 

Flange Joint 


UW-03

• Cat D includes welded joints connecting nozzles to shells, heads 

or flat-sided vessels. 


UW-03

UW-9 DESIGN OF WELDED JOINTS 


UW-09

The main content relates to two areas: 

• Taper transitions between welded sections of unequal thickness 

• ‘Stagger’ of longitudinal welds in vessels 


UW-09

(c) Tapered transitions requires that tapered transitions must have a 

taper of at least 3:1 between sections if the sections differ by the 

smaller of: 

• more than ¼ of the thickness of the thinner section or 

• 1/8 in. (3.2 mm). 

1 ∆t > .25t 1 . 

3 

t 1 

t 2 

∆t > 1/8 in. 


UW-09

(d) Except when the longitudinal joints are radiographed 4 in. (100 mm) 

each side of each circumferential welded intersection, vessels made up 

of two or more courses shall have the centers of the welded longitudinal 

joints of adjacent courses staggered or separated by a distance of at least 

five times the thickness of the thicker plate. 


UW-09

d≥5t 

if d

staggered or separated by a 

distance of at least five times the 

thickness of the thicker plate. 


UW-09

UW-11 Radiographic & Ultrasonic 

Examinations 


UW-11

Based on the ASME Code requirement UG-116, manufacturers have to 

mark the type of RT i.e. RT1, RT2, RT3 and RT4 in the pressure vessel 

name plate and state the same in Pressure Vessel Data Report. 

We have seen many professionals, from inspectors to quality control 

engineers who are confused between RT1 and RT2, specifically when 

they see ASME Pressure Vessel Joint Efficiencies for both RT1 and 

RT2 is the same and equal to 1(E=1).They say both RT1 and RT2 are 

categorized in the “Full Radiography” part in UW-11 clause ... 

So why are some joints in RT2 radiographed in spots? We are making 

spot radiography, but it is categorized in full radiography!!! So in this 

"ASME Pressure Vessel Joint Efficiencies" article we want to answer 

this question in very simple way, but before this, we need review joint 

categories and summarize them as below: 

RT1, RT2, RT3 and RT4 


UW-11

Category A: All longitudinal welds in shell and nozzles All welds in 

heads, Hemisphere-head to shell weld joint 

Category B: All circumferential welds in shell and nozzles Head to 

shell joint (other than Hemisphere.) 

Category C and D are flange welds and nozzle attachment welds 

respectively. 

Longitudinal welds (Category A) are more critical than 

Circumferential welds (Category B) because they are under double 

stress. This the reason why in different part of ASME code we have 

stringent rules in category A joint compared to category B joint. See 

the following Fig. for joint categories: 


UW-11


UW-11

Now let's get back to the ASME Pressure Vessel Joint Efficiencies 

subject, to remove the above confusion about RT1 and RT2. We 

need to know: When and where is there a code requirement for full 

radiography? 

Item 1: All butt welds in vessels used to contain a lethal substance 

(UW-11(a)).Lethal substances have specific definitions in ASME 

Code in UW-2 and it is the responsibility of the end user to 

determine if they ordered a vessel that contains lethal substances. 

Item 2: All butt welds in vessels in which the nominal thickness at 

the welded joint exceeds 1 ½ in. (38 mm), or exceeds the lesser 

thicknesses prescribed in UCS-57,etc. For example, this value for P- 

No.1 in UCS-57 is 1 ¼ inch. 


UW-11

Item 3: All butt welds in an unfired steam boiler with design 

pressure > 50 psi (UW-11(a)). 

Item 4: All category A and D butt welds in vessel when “Full 

Radiography” optionally selected from table UW-12(column (a) 

in this table is selected); and categories B and C which intersect 

Category A shall meet the spot radiography requirement (UW- 

11(a) (5) (b)). 


UW-11

The point is this: item 1, 2 and 3 are similar, but item 4 is completely 

different. In item 1, 2 and 3 it is mandated by code; to do full 

radiography in all butt welds in vessel so it means it is mandatory for 

designer to select column (a) in UW-12 table. 

But in item 4, there is no mandating rule. A manufacturer with its own 

decision has chosen to use column (a) in table UW-12 for full 

radiography. So here there is a concession or bonus to manufacturers for 

categories B and C. 

RT2- categories B and C which intersect Category “A” 

shall meet the spot radiography requirement (UW-11(a) 

(5) (b)), instead of radiography of full length. 


UW-11

RT 

Item 

Note 

Joint 

Efficiency 

(Type-1) 

Radiography details 

1 

1,2,3 

Required 

by code 

1.0 

All butt welds-full length 

radiography. 

2 

4 

Optionally 

selected 

1.0 

Category A and D butt welds full 

length radiography and category 

B and C butt welds spot 

Radiography. 

3 

0.85 

Spot radiography butt welds. 

4 

0.7 

Partial / No radiography. 

http://www.inspection-for-industry.com/asme-pressure-vessel-joint-efficiencies.html 


UW-11

Item 2: 

All butt welds in vessels in which the nominal thickness at the 

welded joint exceeds 1 ½ in. (38 mm), or exceeds the lesser 

thicknesses prescribed in UCS-57,etc. For example, this value for 

P-No.1 in UCS-57 is 1 ¼ inch. 

UCS-57 RADIOGRAPHIC 

EXAMINATION 

In addition to the requirements 

of UW-11, complete 

radiographic examination is 

required for each butt welded 

joint at which the thinner of the 

plate or vessel wall thicknesses 

at the welded joint exceeds the 

thickness limit above which full 

radiography is required in 

Table UCS-57. 


UW-11


EXAMINATION 





joint at which the thinner of the 



thickness limit above which 

full radiography is required in 

Table UCS-57. 


UW-11

RT 1 

RT 2 

RT 3 

RT 4 

UG-116(e1) “RT 1” 

when all pressure-retaining butt welds, other than Category B and C butt welds 

associated with nozzles and communicating chambers that neither exceed NPS 10 

(DN 250) nor 1 1⁄8 in. (29 mm) wall thickness [except as required by UHT-57(a)], 

satisfy the full radiography requirements of UW-11(a) for their full length; full 

radiography of the above exempted Category B and C butt welds, if performed, may 

be recorded on the Manufacturer’s Data Report; or 

UG-116(e2) “RT 2” 

when the complete vessel satisfies the requirements of UW-11(a)(5) and 

when the spot radiography requirements of UW-11(a)(5)(b) have been 

applied; or 

UG-116(e3) “RT 3” 

when the complete vessel satisfies the spot radiography requirements of 

UW-11(b); or 

UG-116(e4) “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. 


UW-11

UW-11(a2) all butt welds in vessels in 

which the nominal thickness [see (g) 

below] at the welded joint exceeds 1 

½ in. (38 mm), or exceeds the lesser 

thicknesses prescribed in UCS-57, 

UNF-57, UHA-33, UCL-35, or 

UCL-36 for the materials covered 

therein, or as otherwise prescribed in 

UHT-57, ULW-51, ULW-52(d), 

ULW-54, or ULT-57; however, 

except as required by UHT-57(a), 

Categories Band Cbutt welds in 

nozzles and communicating 

chambers that neither exceed NPS 

10 (DN 250) nor 11⁄8 in. (29 mm) 

wall thickness do not require any 

radiographic examination; 


UW-11

UW-11(a2) …Categories Band Cbutt 

welds in nozzles and communicating 

chambers that neither exceed 

• NPS 10 (DN 250) nor 

• 1 1/8 in. (29 mm) wall thickness 

do not require any radiographic 

examination; 


UW-11

UW-11 RADIOGRAPHIC AND ULTRASONIC EXAMINATION 

UW-11 (a) Full Radiography. The following welded joints shall be examined 

radiographically for their full length in the manner prescribed in UW-51: 

UW-11(a5) all Category A and D butt welds in vessel sections and heads where the 

design of the joint or part is based on a joint efficiency permitted by UW-12(a), in 

which case: 

UW-11(a5a) Category A and B welds connecting the vessel sections or heads shall be 

of Type No. (1) or Type No.(2) of Table UW-12; 

UW-11(a5b) Category B or C butt welds [but not including those in nozzles or 

communicating chambers except as required in (2) above] which intersect the 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 in 

accordance with UW-52. Spot radiographs required by this paragraph shall not be 

used to satisfy the spot radiography rules as applied to any other weld increment. 


UW-11

UW-11 (a8) exemptions from radiographic examination for certain welds in nozzles 

and communicating chambers as described in (2), (4), and (5) above take 

precedence over the radiographic requirements of Subsection C of this Division. 

This means that even though P- 

No. 5 for example requires RT in 

all thicknesses the small/thin 

nozzles are exempt. 


UW-11

UW-11(a) 

Full Radiography 

(1) all butt welds in the shell and heads of vessels used to contain lethal substances. 

(2) all butt welds in the shell and heads of unfired steam boilers having design pressures 

exceeding 50 psi (350 KPa). 

(3) all butt welds in nozzles, communicating chambers, etc., attached to vessel sections 

or heads that are required to be fully radiographed under (1) or (2) above; 

• however, except as required by UHT-57(a), Categories B and C butt welds in 

nozzles and communicating chambers that neither exceed NPS 10 (DN 250) nor 1 

1⁄8 in. (29 mm) wall thickness do not require any radiographic examination; 

Keywords: 

contain lethal substances 

unfired steam boilers having design pressures exceeding 50 psi 


UW-11

Full radiography: 

all butt welds in the 

shell and heads of 

unfired steam boilers 

having design pressures 

exceeding 50 psi 

(350 KPa). 


UW-11

Except as required by UHT-57(a), Categories B and C butt welds in 

nozzles and communicating chambers that neither exceed NPS 10 (DN 

250) nor 11⁄8 in. (29 mm) wall thickness do not require any radiographic 

examination; 

neither exceed NPS10 nor 

t >11⁄8 in. NO Radiography 


UW-11

• all butt welds in vessels in which the nominal thickness at the welded 

joint exceeds 1 ½ in. (38 mm), or 

• exceeds the lesser thicknesses prescribed in UCS-57, UNF-57, UHA- 

33, UCL-35, or UCL-36 for the materials covered therein, or as 

otherwise prescribed in UHT-57, ULW-51, ULW-52(d), ULW-54, or 

ULT-57; however, except as required by UHT-57(a). 

• Categories B and C butt welds in nozzles and communicating 

chambers that neither exceed NPS 10 (DN 250) nor 1 1⁄8 in. (29 mm) 

wall thickness do not require any radiographic examination. 

Keywords: 

Any vessel with welded joint exceeds 1 ½ in. (38mm). 


UW-11

Any vessel with welded joint exceeds 1 ½ in. 


UW-11

(5) all Category A and D butt welds in vessel sections and heads where the design of 

the joint or part is based on a joint efficiency permitted by UW-12(a). 

Joint 

Type 

1 

Joint 

Categories 

A, B, C & D 


Examination. 

Full 

1.00 

Spot 

0.85 

None 

0.7 

2 

A, B, C & D 

0.90 

0.80 

0.65 

A, B & C 

0.90 

0.80 

0.65 


UW-11

in which case: 

(a)Category A and B welds connecting the vessel sections or heads shall 

be of Type No. (1) or Type No. (2) of Table UW-12; 

(b)Category B or C butt welds [but not including those in nozzles or 

communicating chambers except as required in (2) above] which 

intersect the 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 in accordance with UW-52. 

Spot radiographs required by this paragraph shall not be used to 

satisfy the spot radiography rules as applied to any other weld 

increment. 


UW-11

(6) all butt welds joined by electrogas welding with any single pass greater than 1 ½ in. 

(38 mm) and all butt welds joined by electroslag welding; 


UW-11

(7) ultrasonic examination in accordance with UW-53 may be substituted 

for radiography for the final closure seam of a pressure vessel if the 

construction of the vessel does not permit interpretable radiographs in 

accordance with Code requirements. The absence of suitable radiographic 

equipment shall not be justification for such substitution. 

(8) exemptions from radiographic examination for certain welds in 

nozzles and communicating chambers as described in (2), (4), and (5) 

above take precedence over the radiographic requirements of Subsection 

C of this Division. 


UW-11

Full Radiography means UW-11(a-1, a-2, a-3, a-4)- lethal, unfired 

steam boilers having design pressures exceeding 50 psi and nominal thickness at the welded joint 

exceeds 1 ½ in. (38 mm). 


Radiographically for their full length. 

Requirements for spot radiography. 

No radiography. 

Except as required by UHT-57(a), 

Categories B and C butt welds in 

nozzles and communicating chambers 

that neither exceed NPS 10 (DN 250) 

nor 11⁄8 in. (29 mm) wall thickness do 

not require any radiographic 

examination; 

UW-11

Full Radiography means UW-11 (a-5): non lethal, non unfired steam boilers 

having design pressures exceeding 50 psi, nominal wall thickness less than 1 ½ in. 


Radiographically for their full length. 

Requirements for spot radiography. 

No radiography. 

Except as required by UHT-57(a), 

Categories B and C butt welds in 

nozzles and communicating chambers 

that neither exceed NPS 10 (DN 250) 

nor 11⁄8 in. (29 mm) wall thickness do 

not require any radiographic 

examination; 

UW-11

UW-11(b) 

Spot Radiography 

Except when spot radiography is required for Category B or C butt welds 

by (a)(5)(b) above, butt welded joints made in accordance with Type No. 

(1) or (2) of Table UW-12 which are not required to be fully 

radiographed by (a) above, may be examined by spot radiography. 

Spot radiography shall be in accordance with UW-52. If spot radiography 

is specified for the entire vessel, radiographic examination is not required 

of Category B and C butt welds in nozzles and communicating chambers 

that exceed neither NPS 10 (DN 250) nor 1 1⁄8 in. (29 mm) wall 

thickness. 


UW-11

Radiographic examination is not required of 

Category B and C butt welds in nozzles and 

communicating chambers that exceed neither 

NPS 10 (DN 250) nor 1 1⁄8 in. (29 mm) wall 

thickness. 


UW-11

(c) No Radiography. 

Except as required in (a) above, no radiographic examination of welded joints is 

required when the vessel or vessel part is designed for external pressure only, or when 

the joint design complies with UW-12(c). 

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

1 




same quality of deposited 

weld metal on the inside and 

outside weld surfaces to 

agree with the requirements 

of UW-35. Welds using metal 

backing strips which remain 

in place are excluded. 

A, B, C & D 

1.00 

0.85 

0.7 


UW-11

UW-11(d,e,f) 

Special welding processes. 

Welding 

Process 

Electrogas 

Electroslag 

Conditions 

ferritic materials with 

any single pass 

greater that 11⁄2 in. 

(38 mm) 

ferritic materials 

ultrasonic examination examined 

throughout their entire length and 

shall be done following the grain 

refining (austenitizing) heat treatment 

or postweld heat treatment. 

Electron 

beam 

Friction 


In addition to the 

requirements in (a) 

and (b) 

When radiography is 

required for a welded 

joint in accordance 

with (a) and (b). 


throughout their entire length 


throughout their entire length 

UW-11

(g) For radiographic and ultrasonic examination of butt welds, the 

definition of nominal thickness at the welded joint under consideration 

shall be the nominal thickness of the thinner of the two parts joined. 

Nominal thickness is defined in 3-2. 


UW-11

http://www.mechanicalengine 

eringblog.com/3635-weldingtechnology-electro-gaswelding-egw/ 


UW-11


UW-11


UW-11


UW-11

UW-12 JOINT EFFICIENCIES 


UW-12

Weld Types: 

Here is some clarification about the different type of welds that have 

specific definitions in ASME Code SEC VIII DIV 1 and related to the 

pressure vessel RT test. 

The concept is to define the different types and then introduce some 

restriction for using them. 

For example, a Type 1 weld is defined as a full penetration weld, 

typically double welded and Type 2 is welds with backing strips. 

So when you go to service restriction for a vessel containing a lethal 

substance, you see there is a restriction there that says all category A 

joints shall be weld Type 1 and Category B and C shall be type 1 or 

type 2.You should take this point in to account, which is this: the same 

joint category with different weld types have different joint efficiencies. 


UW-12

Summary of weld types: 

Type 1: Full penetration welds (Typically Double welded). 

Type 2: Welds with backing strip. 

Type 3: Single welded partial penetration welds. 

Type 4, 5 and 6: Various Lap welds (rarely used) 


UW-12

TABLE UW-12 

MAXIMUM ALLOWABLE JOINT 

EFFICIENCIES FOR ARC AND GAS 

WELDED JOINTS 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

1 










excluded. 

A, B, C & D 

1.00 

0.85 

0.7 

2 





(b) below 




see UW-13(b) 

(4) and Fig. 


(i) 

A, B, C & D 

A, B & C 

0.90 

0.90 

0.80 

0.80 

0.65 

0.65 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

2 





(b) below 




see UW-13(b) 

(4) and Fig. 


(i) 

A, B, C & D 

A, B & C 

0.90 

0.90 

0.80 

0.80 

0.65 

0.65 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

3 

Single-welded butt joint 

with out used of backing 

strip. 

Circumferential butt joints only, 

not over 5⁄8 in. (16 mm) thick 

and not over 24 in. (600 mm 

outside diameter) 

A, B, C 

NA 

NA 

0.6 

4 

Double full fillet lap joint. 

(a) Longitudinal joints not over 

3/8 in. (10mm) thick 

A 

NA 

NA 

0.55 

(b) Circumferential joints not 

over 5/8 in. (16mm) thick. 

B, C [note 3] 

NA 

NA 

0.55 

5 

Single full fillet lap joints 

with plug welds 

conforming to 

(a) Circumferential joints [Note 

4 (exclude hemispherical) ] for 

attachment of heads not over 24 

in. (600 mm) outside diameter to 

shells not over 1⁄2 in. (13 mm) 

thick. 

B 

NA 

NA 

0.50 

(b) Circumferential joints for the 

attachment to shells of jackets 

not over 5⁄8 in. (16 mm) in 

nominal thickness where the 

distance from the center of the 

plug weld to the edge of the plate 

is not less than 1 ½ times the 

diameter of the hole for the plug. 

C 

NA 

NA 

0.50 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

6 


without plug welds 

(a) For the attachment of heads 

convex to pressure to shells not 

over 5⁄8 in.(16 mm) required 

thickness, only with use of fillet 

weld on inside of shell; or 

A, B 

NA 

NA 

0.45 

(b) for attachment of heads 

having pressure on either side, to 

shells not over 24 in. (600 mm) 

inside diameter and not over 1⁄4 

in. (6 mm) required thickness 

with fillet weld on outside of 

head flange only. 

A, B 

NA 

NA 

0.45 

7 

Corner joints, full 

penetration, partial 

penetration, and/or fillet 

welded. 

As limited by Fig. UW-13.2 and 

Fig UW-16. 

C, D 

[Note (5)] 

NA 

NA 

NA 

8 

Angle joints 

Design per U-2(g) for Category 

B and C joints 

B, C, D 

NA 

NA 

NA 


UW-12

Summary Maximum Weld Joint Efficiency: Joint Type 1~6 


UW-12

Summary of weld types: 

Type 1: Full penetration welds (Typically Double welded) 

Type 2: Welds with backing strip 

Type 3: Single welded partial penetration welds 

Type 4, 5 and 6: Various Lap welds (rarely used) 

http://www.inspection-for-industry.com/asme-pressure-vessel-joint-efficiencies.html 


UW-12

Butt joints as attained by double-welding or by other means 

which will obtain the same quality of deposited weld metal on 

the inside and outside weld surface. Backing strip, if used, shall 

be removed after completion of weld. 

Single-welded butt joint with backing strip which remains 

in place after welding. 

Type 2: For circumferential joint only 

Single-welded butt joint without backing strip. 

Double-full fillet lap joint. 

Single-full fillet lap joint with plug welds. 

Single-full fillet lap joint without plug welds. 


UW-12


UW-12

TABLE UW-12 

MAXIMUM ALLOWABLE JOINT 

EFFICIENCIES FOR ARC AND GAS 

WELDED JOINTS 

With 

illustrations 

UW-13 ATTACHMENT 

DETAILS 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

1 










excluded. 

A, B, C & D 

1.00 

0.85 

0.7 


UW-12

Weld type number 1: Single “V” with back-gouge. 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

2 





(b) below 




see UW-13(b) 

(4) and Fig. 


(i) 

A, B, C & D 

A, B & C 

0.90 

0.90 

0.80 

0.80 

0.65 

0.65 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

3 

Single-welded butt joint 

with out used of backing 

strip. 

Circumferential butt joints only, 

not over 5⁄8 in. (16 mm) thick 

and not over 24 in. (600 mm 

outside diameter) 

A, B, C 

NA 

NA 

0.6 


UW-12

If the type number 3 weld was radiographed the full 

length, could it be grouped as type 1 weld? 

Type 

number 

1 


•Butt joints as attained by double-welding or by 

other means which will obtain the same quality of 

deposited weld metal on the inside and outside 

weld surfaces to agree with the requirements of 

UW-35. Welds using metal backing strips which 

remain in place are excluded. 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

4 

Double full fillet lap joint. 

(a) Longitudinal joints not over 

3/8 in. (10mm) thick 

A 

NA 

NA 

0.55 

(b) Circumferential joints not 

over 5/8 in. (16mm) thick. 

B, C [note 3] 

NA 

NA 

0.55 


UW-12

Type 

number 


Limitations 

Joint 

Cat. 


Examination. 

Full 

Spot 

None 

5 

Single full fillet lap 

joints with plug welds 

conforming toUW-17 

(a) Circumferential joints [Note 4 (exclude 

hemispherical) ] for attachment of heads not 

over 24 in. (600 mm) outside diameter to 

shells not over 1⁄2 in. (13 mm) thick. 

B 

NA 

NA 

0.50 

C 

NA 

NA 

0.50 

(b) Circumferential joints for the attachment 

to shells of jackets not over 5⁄8 in. (16 mm) in 

nominal thickness where the distance from the 

center of the plug weld to the edge of the plate 

is not less than 1 ½ times the diameter of the 

hole for the plug 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

6 


without plug welds 

(a) For the attachment of heads 

convex to pressure to shells not 

over 5⁄8 in.(16 mm) required 

thickness, only with use of fillet 

weld on inside of shell; or 

A, B 

NA 

NA 

0.45 

A, B 

NA 

NA 

0.45 

(b) for attachment of heads having 

pressure on either side, to shells not 

over 24 in. (600 mm) inside 

diameter and not over 1⁄4 in. (6 mm) 

required thickness with fillet weld 

on outside of head flange only. 


UW-12

Type 

number 


Limitations 

Joint 

Categories 


Examination. 

Full 

Spot 

None 

7 

Corner joints, full 

penetration, partial 

penetration, and/or fillet 

welded. 

As limited by Fig. UW-13.2 and 

Fig UW-16. 

C, D 

[Note (5)] 

NA 

NA 

NA 

8 

Angle joints 

Design per U-2(g) for Category 

B and C joints 

B, C, D 

NA 

NA 

NA 


UW-12

GENERAL NOTES: 

(a) The single factor shown for each combination of joint category and degree of 

radiographic examination replaces both the stress reduction factor and the joint 

efficiency factor considerations previously used in this Division. 

(b) E = 1.0 for butt joints in compression. 

NOTES: 

1. See UW-12(a) and UW-51. 

2. See UW-12(b) and UW-52. 

3. For Type No. 4 Category C joint, limitation not applicable for bolted flange 

connections. 

4. Joints attaching hemispherical heads to shells are excluded. 

5. There is no joint efficiency “E” in the design formulas of this Division for 

Category C and D corner joints. When needed, a value of E not greater than 1.00 

may be used. 


UW-12

(i) Butt Weld With One Plate Edge Offset 

NOTES: 

(1) See UW-13(b)(4) for limitation 

when 

weld bead is deposited from inside. 

(2) For joints connecting 

hemispherical heads 

to shells, the following shall apply: 

(a) t or t 1 = 3/8 in. (10 mm) 

maximum 

(b) maximum difference in thickness 

between t or t 1 = 3/32 in. (2.5 mm); 

(c) use of this figure for joints 

connecting hemispherical heads to 

shells shall be noted in the “Remarks” 

part of the Data Report Form. 


UW-12

UW12(d) Seamless vessel sections or heads. 


UW-12

UW12(d) Seamless vessel sections or heads shall be 

considered equivalent to welded parts of the same geometry in 

which all Category A welds are Type No. 1. For calculations 

involving circumferential stress in seamless vessel sections or 

for thickness of seamless heads, E = 1.0 when the spot 

radiography requirements of UW-11(a)(5)(b) are met. E = 

0.85 when the spot radiography requirements of UW- 

11(a)(5)(b) are not met, or when the Category A or B welds 

connecting seamless vessel sections or heads are Type No. 3, 

4, 5, or 6 of Table UW-12. 


UW-12

UW12(d) 

• all Category A welds are Type No. 1. 

- hemispherical head- Category “A” 

- non-hemispherical head- Category “B” 

• E = 1.0 when the spot radiography requirements of UW- 

11(a)(5)(b) are met. 

- non-hemispherical head- Category “B” as 11(a)(5)(b) applicable to category 

“B” and “C” only. 

• E = 0.85 when the spot radiography requirements of UW- 

11(a)(5)(b) are not met, or when the Category A or B welds 

connecting seamless vessel sections or heads are Type No. 

3, 4, 5, or 6 of Table UW-12. 

- non-hemispherical head- Category “B” 


UW-12

UW-11(a)(5)(b), Category B or C butt welds… 

which intersect the 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 in accordance 

with UW-52. … 


UW-12

Q. Given a seamless head or shell section, other than a 

hemispherical head (see UG-32), what is the design 

efficiency of the seamless section? 

A. Paragraph UW-12(d) answers this question with a 

question, as follows: Was the weld(s) joining the seamless 

head or seamless shell spot examined per the rules given in 

UW-11(a)(5)(b)? If yes, the seamless head or shell efficiency 

is set at 100 percent E=1. If no, the seamless head or shell 

efficiency will be set at 85 percent E=0.85. 

http://www.nationalboard.org/PrintPage.aspx?NewsPageID=144 


UW-12

Q. Given a seamless head or shell section of hemispherical 

head (see UG-32), what is the design efficiency of the 

seamless section? 

• 100% RT UW-51, E= 1 ? 

• Spot RT UW-52, E= 0.85 ? 

• No RT, E= 0.7 ? 


UW-12

Hemispherical head 

• 100% RT UW-51, E= 1 

• Spot RT UW-52, E= 0.85 

Ellipsoidal & Torispherical 

• Spot RT UW-52, E= 1 

• No RT, E= 0.85 

• No RT, E= 0.7 


UW-12


UW-12


UW-12


UW-12


UW-12


UW-12


UW-12


UW-12


UW-12

UW-16 MINIMUM REQUIREMENTS FOR 

ATTACHMENT WELDS AT OPENINGS. 


UW-16

FIG. UW-16.1 SOME ACCEPTABLE TYPES OF WELDED NOZZLES AND 

OTHER CONNECTIONS TO SHELLS, HEADS, ETC. 

UW-16.1 sketches (i), (j), (k), and (l). 


UW-16

These are variables that will apply to the Exam. 

t = nominal thickness of vessel shell or head, in. 

t n = nominal thickness of nozzle wall, in. 

• t min = the smaller of 3/4 in. or the thickness of the thinner of the 

parts joined by a fillet, single-bevel, or single-J weld, in. 

• t c = not less than the smaller of 1/4 in. or 0.7t min 

• t 1 or t 2 = not less than the smaller of 1/4 in. or 0.7t min 

• t c = t 1 or t 2 


UW-16

t c = not less than the smaller of 1/4 in. or 0.7t min 


UW-16


2 conditions to satisfied; 

• t 1 or t 2 ≥ smaller of ¼ in. or 0.7 t min 

• t 1 + t 2 ≥ 1 ¼ t min ( not applicable to all sketched) 

UW-16(d) Neck Attached by Fillet or Partial Penetration Welds 

(1) Necks inserted into or through the vessel wall may be attached by fillet or 

partial penetration welds, one on each face of the vessel wall. The welds 

may be any desired combination of fillet, single-bevel, and single-J welds. 

The dimension of t1 or t2 for each weld shall be not less than the smaller of 1⁄4 

in. (6 mm) or 0.7tmin, and their sum shall be not less than 11⁄4tmin. See Fig. 



UW-16

Exercise: 

Problem: A nozzle is being attached to a shell as shown in Fig.UW-16.1 (i) 

using two equal size fillet welds. The shell's thickness is 7/8 in. and the 

nozzle's thickness is 1/2 inch. The fillet welds are 3/8 inch in leg size. Does 

this meet Code? 

t min = smaller of ¾ in. or ½ in. ( used ½ in. in this case). 

Fillet throat sizes t 1 = t 2 = 0.707x0.375 = 0.265 in. 

Conditions to satisfied; 

1. t 1 or t 2 ≥ ¼ in. or 0.7 t min ( used 0.25 in. in this case) 

2. t 1 + t 2 ≥ 1 ¼ t min ( equal to 0.625 in.) 

Actual; 

t 1 & t 2 = 0.265 in. (condition 1 – ok) 

t 1 + t 2 = 0.53 in. (condition 2 – Not ok) 

Conclusion: the fillet leg sizes are undersized.# 


UW-16

Fillet 

Leg size ≠ throat size 


UW-16

FIG. UW-16.1 SOME 

ACCEPTABLE TYPES OF 

WELDED NOZZLES AND 

OTHER CONNECTIONS TO 

SHELLS, HEADS, ETC. 


UW-16


UW-16


UW-16


UW-16


UW-16


UW-16

• t = nominal thickness of vessel shell or head 

• t n = nominal thickness of nozzle wall 

• t e = thickness of reinforcing plate 

• t w = dimension of attachment welds (fillet, single-bevel or single-J), 

measured as shown in figure UW-16.1 

• t min = the smaller of ¾ in (19 mm) or the thickness of the thinner of 

the parts joined by a fillet, single-bevel or single-J weld 

• t c = not less than the smaller of ¼ in. (6 mm) or 0.7 t min 

• t 1 or t 2 =not less than the smaller of ¼ in. (6 mm) or 0.7t min 

t w = 0.7t min 

(see fig.UW-16.1) 

t c = t 1 or t 2 =not less than the smaller of ¼ in. (6 mm) or 0.7t min 


UW-16

t min = the smaller of ¾ in (19 mm) or the 

thickness of the thinner of the parts joined by a 

fillet, single-bevel or single-J weld 

tc =t 1 = t 2 = not less than the smaller of ¼ in. (6 

mm) or 0.7t min 


UW-16

where it meets a set-on nozzle, by a full 

penetration butt weld plus a fillet weld with 

minimum throat dimension t w = 0.7t min 

if it does not meet the nozzle. The 

fillet weld will have a minimum 

throat dimension of ½ t min . 


UW-16

Integral reinforcement (also known as self-reinforcement). 


UW-16

Q3. ASME VIII section UW-16 (c) figure 16.1(a) A vessel is manufactured from P1 

Grade 2 material. It has a shell thickness of 18 mm and is used to contain lethal 

substances. A set-on (abutting) nozzle of 12 mm thickness is attached using a 

category D full penetration weld with reinforcing fillet. What is the minimum 

required throat thickness of the reinforcing fillet weld? 

(a) 12 mm (t min ) 

(b) 8.4 mm (0.7t min ) 

(c) 6 mm (t c ) 

(d) 12.6 mm 

t min = 12mm (the smaller of 3⁄4 in. (19 mm) or the 

thickness of the thinner of the parts joined.) 

t c = 6mm (not less than the smaller of 1⁄4 in. (6 mm) or 

0.7t min ) 


UW-16

Q4. ASME VIII section UW-16 (c)(2)(c) 

A vessel has a shell thickness of 3 4 in (19 mm). A set-on (abutting) 

nozzle of ½ in. (13 mm) thickness is attached using a category D full penetration 

weld. A reinforcing plate of 1/4 in. (6 mm) is required. What welds will be 

required to attach the reinforcing plate to the nozzle? 

(a) A full penetration weld plus a fillet with a 4.2 mm throat & 

(b) A full penetration weld plus a fillet with a 6 mm throat & 

(c) A fillet weld with a 3 mm throat & 

(d) A full penetration weld plus a fillet with a 3 mm throat & 

• t c =4.2 (not less than 

the smaller of 1/4 in. (6 

mm) or 0.7t min.) 

• t min = 6 mm. 


UW-16

Q5. ASME VIII section UW-16 (d)(1) 

A nozzle of NPS 10 (DN 250) is inserted through a vessel wall and protrudes into the 

vessel by an amount equal to the nozzle thickness. The nozzle thickness is one half of 

the shell thickness. Which of the following weld combinations are acceptable to attach 

the nozzle? 

(a)Partial penetration groove or fillet weld on inside and outside face 

(b)Partial penetration groove with reinforcing fillet on outside face 

(c)Partial penetration groove with reinforcing fillet on inside face 

(d)Any of the above is acceptable 

• t 1 + t 2 ≥ 1 ¼ t min . 

• t 1 or t 2 not less 

than the smaller 

of ¼ in. (6 mm) 

or 0.7t min . 


UW-16

UW-40 PROCEDURES FOR POSTWELD HEAT 

TREATMENT. 


UW-40

UW-40(f ) The term nominal thickness as used in Tables UCS-56, 

UCS-56.1, UHA-32, and UHT-56, is the thickness of the welded 

joint as defined below. For pressure vessels or parts of pressure 

vessels being postweld heat treated in a furnace charge, it is the 

greatest weld thickness in any vessel or vessel part which has not 

previously been postweld heat treated. 

See also: UCS-56 REQUIREMENTS FOR 

POSTWELD HEAT TREATMENT 


UW-40


UW-40

UW-40(a), the soak band shall contain the weld, heat affected zone, 

and a portion of base metal adjacent to the weld being heat treated. The 

minimum width of this volume is the widest width of weld plus 1t or 2 

in. (50 mm), whichever is less, on each side or end of the weld. 

widest width of weld plus 1t or 2 in. 

(50 mm), whichever is less 


UW-40

Mr. “t” the nominal thickness UW-40(f) 

1. it is the greatest weld thickness in any vessel or 

vessel part which has not previously been postweld 

heat treated. 

2. Same thickness, using a full penetration butt weld, 

the nominal thickness is the total depth of the weld 

exclusive of any permitted weld reinforcement. 

3. For groove welds, the nominal thickness is the 

depth of the groove. 

4. fillet welds, the nominal thickness is the throat 

dimension. 

5. If a fillet weld is used in conjunction with a groove 

weld, the nominal thickness is the depth of the 

groove or the fillet throat dimension, whichever is 

greater. 


UW-40

fillet welds, the nominal 

thickness is the throat 

dimension 


UW-40

the nominal thickness is 

the total depth of the weld 

exclusive of any 

permitted weld 

reinforcement 


UW-40

The nominal thickness 

6. When a welded joint connects parts of unequal thicknesses 

(a) the thinner of two adjacent butt-welded parts including head to shell 

connections; 

the thinner of two adjacent butt-welded 


UW-40

The nominal thickness 

(b) the thickness of the shell or the fillet weld, whichever is greater, in 

connections to intermediate heads of the type shown in Fig. UW-13.1 

sketch (e); 


UW-40

Mr. “t” the nominal thickness 

(c) the thickness of the shell in connections to tubesheets, flat heads, 

covers, flanges (except for welded parts depicted in Fig. 2-4(7), where 

the thickness of the weld shall govern), or similar constructions; 


UW-40


(d) in Figs. UW-16.1 and UW-16.2, the thickness of the weld across 

the nozzle neck or shell or head or reinforcing pad or attachment fillet 

weld, whichever is the greater; 


UW-40


e) the thickness of the nozzle neck at the joint in nozzle neck to flange 

connections; 

f) the thickness of the weld at the point of attachment when a non 

pressure part is welded to a pressure part; 

g) the thickness of the weld in tube-to-tubesheet connections. 


UW-40

(6) For repairs, the nominal thickness is the depth of the repair weld. 

Nominal thickness 

Defects 

Depth of 

excavation 


UW-40

UW-50 NONDESTRUCTIVE EXAMINATION OF 

WELDS ON PNEUMATICALLY TESTED VESSELS. 


UW-50

On welded pressure vessels to be pneumatically tested in accordance 

with UG-100, the full length of the following welds shall be 

examined7 for the purpose of detecting cracks: 

a) all welds around openings; 

b) all attachment welds, including welds attaching non-pressure parts to 

pressure parts, having a throat thickness greater than ¼ in. (6 mm). 

Note: 

7 

Examination shall be by magnetic particle or liquid penetrant methods 

when the material is ferromagnetic, or by the liquid penetrant method 

when the material is nonmagnetic. 


UW-50

UW-51 RADIOGRAPHIC EXAMINATION OF 

WELDED JOINTS. 


UW-51

• UW-51 (a1) A complete set of radiographs and records, as described 

in Article 2 of Section V, for each vessel or vessel part shall be 

retained by the Manufacturer, as follows: 

a) films until the Manufacturer’s Data Report has been signed by the 

Inspector; 

b) records as required by this Division (10-13). 

RT films; After signing of MDR 

Records; 

(10-13) at least 3 years 

MDR 


UW-51

10-13 RECORDS RETENTION 

a) The Manufacturer or Assembler shall have a system for the 

maintenance of radiographs (UW-51), Manufacturer’s Data Reports 

(UG-120), and Certificates of Compliance/Conformance (UG-120) as 

required by this Division. 


UW-51

10-13 RECORDS RETENTION 

b) The Manufacturer or Assembler shall maintain the documents outlined 

below for a period of at least 3 years: 

1. Manufacturer’s Partial Data Reports. 

2. manufacturing drawings. 

3. design calculations, including any applicable Proof Test Reports. 

4. Material Test Reports and or material certifications. 

5. Welding Procedure Specifications and Procedure Qualification Records. 

6. Welders Qualification Records. 

7. RT and UT reports. 

8. repair procedure and records. 

9. process control sheets. 

10.heat treatment records and test results. 

11.postweld heat treatment records. 

12.non-conformances and dispositions. 

13.hydrostatic test records. 


UW-51

(c) For manufacturers of UM stamped vessels or vessels constructed 

under the provisions of UG-90(c)(2) rules, the records listed in (b) 

above, for six representative vessels per year, shall be maintained as 

follows: 

1. UM stamped vessels for a period of 1 year. 

2. vessels constructed under the provisions of UG-90(c)(2) rules for a 

period of 3 years. 

ASME certification is symbolized by the “U Stamp” for 

pressure vessels and “UM Stamp” for miniature pressure 

vessels. 


UW-51


UW-51

When do you need full RT 


UW-51

UW-11, (a1) all butt welds in the shell and heads of 

vessels used to contain lethal substances [see UW- 

2(a)]. 


UW-51

UW-11, a(2). All materials; welded joint exceeds 1 ½ 

in. (38 mm) 


UW-51

UW-11, a(2)……… 


EXAMINATION 





joint at which the thinner! of the 



thickness limit above which full 

radiography is required in Table 

UCS-57. 


UW-51

UW-11 (a3) all butt welds in the shell and heads of 

unfired steam boilers having design pressures 

exceeding 50 psi (350 kPa) [see UW-2(c)]. 


UW-51

UW-11 (a5) all Category A and D butt welds in 

vessel sections and heads where the design of the 

joint or part is based on a joint efficiency permitted 

by UW-12(a), ….(RT2) 

Type 

number 

1 

Joint 

Categories 

A, B, C & D 


Examination. 

Full 

1.00 

Spot 

0.85 

None 

0.7 

2 

A, B, C & D 

0.90 

0.80 

0.65 

A, B & C 

0.90 

0.80 

0.65 


UW-51

UW-11 (a6) all butt welds joined by electrogas 

welding with any single pass greater than 1½in. 

(38 mm) 


UW-51

UW-11 (a6) ….. all butt welds joined by electroslag 

welding; 


UW-51

UW-51 (a2) A written radiographic examination procedure is not 

required. Demonstration of (1) density and (2) penetrameter 

image requirements on production or technique radiographs shall be 

considered satisfactory evidence of compliance with 

Article 2 of Section V. 


UW-51

A written radiographic examination procedure is not required. 


UW-51

Demonstration of (1) density and (2) penetrameter image 

requirements on production or technique radiographs shall be 



Density 

Penetrameter 


UW-51

Demonstration of (1) density and (2) penetrameter image 

requirements on production or technique radiographs shall be 




UW-51

Demonstration of (1) density and (2) penetrameter image requirements 

on production or technique radiographs shall be considered satisfactory 

evidence of compliance with Article 2 of Section V. 


UW-51

Repaired weld 

radiographic testing 

substituted by UT? 


UW-51

• Repaired welding, at the option of the Manufacturer, ultrasonically 

examined in accordance with the method described in Appendix 12 

and the standards specified in this paragraph, provided; 

• The defect has been confirmed by the ultrasonic examination to the 

satisfaction of the Authorized Inspector prior to making the repair. 

• For material thicknesses in excess of 1 in. (25 mm), the concurrence of 

the user shall be obtained. 

• This ultrasonic examination shall be noted under remarks on the 

Manufacturer’s Data Report Form. 

Repaired weld 

radiographic testing 

substituted by UT? 


UW-51

UW-51 (b) 

Degree of 

Radiographic 

Examination. 

Full 

Unacceptable imperfections 

(1) indication characterized as a crack or zone of incomplete fusion 

or penetration; 

(2) any other elongated indication on the radiograph which has 

length greater than: 

(a) ¼ in. (6 mm) for t up to ¾ in. (19 mm) 

(b) ⅓ t for t from ¾ in. (19 mm) to 2 ¼ in. (57 mm) 

(c) ¾ in. (19 mm) for t over 2 ¼ in. (57mm) 

(3) any group of aligned indications that have an aggregate length 

greater than “t” in a length of 12t, except when the distance between 

the successive imperfections exceeds 6L where L is the length of 

the longest imperfection in the group; 

(4) rounded indications in excess of that specified by the acceptance 

standards given in Appendix 4. 


UW-51


UW-51 (b1) 

UW-51 (b4) 

UW-51 (b1) indication characterized as a crack or zone of incomplete fusion or 

penetration; 


UW-51


UW-51 (b1) 

UW-51 (b2) 

UW-51 (b1) indication characterized as a crack or zone of incomplete fusion or 

penetration; 


UW-51


UW-51 (b2) 

UW-51 (b2) any other elongated indication on the radiograph which has length 

greater than: 





UW-51


UW-51 (b1) 

UW-51 (b2) 


greater than: 





UW-51



greater than: 





UW-51


UW-51 (b1) 

UW-51 (b3) any group of aligned indications that have an aggregate length greater 

than “t” in a length of 12t, except when the distance between the successive 

imperfections exceeds 6L where L is the length of the longest imperfection in the 

group; 

UW-51 (b2) 


UW-51

UW-51 (b3) any group of aligned indications that have an aggregate length greater 

than “t” in a length of 12t, except when the distance between the successive 

imperfections exceeds 6L where L is the length of the longest imperfection in the 

group; 


UW-51


UW-51 (b1) 

UW-51 (b4) rounded indications in excess of that specified by the acceptance 


UW-51 (b4) 


UW-51


UW-51 (b4) rounded indications in excess of that specified by the acceptance 



UW-51

UW-51 (b1) 

UW-51 (b2) 


UW-51

UW-51 (b2) 

http://www.ndted.org/EducationResources/ 

CommunityCollege/Radiogr 

aphy/TechCalibrations/Radi 

ographInterp.htm 

UW-51 (b2) 


UW-51

UW-52 SPOT EXAMINATION OF WELDED JOINTS 


UW-52

In-progress RT for quality improvement. 

NOTE: Spot radiographing of a welded joint is recognized as an effective inspection 

tool. The spot radiography rules are also considered to be an aid to quality control. 

Spot radiographs made directly after a welder or an operator has completed a unit of 

weld proves that the work is or is not being done in accordance with a satisfactory 

procedure. If the work is unsatisfactory, corrective steps can then be taken to improve 

the welding in the subsequent units, which unquestionably will improve the weld 

quality. 

Spot radiography doe not ensure defect 

free welds. 

Spot radiography in accordance with these rules will not ensure a fabrication product 

of predetermined quality level throughout. It must be realized that an accepted vessel 

under these spot radiography rules may still contain defects which might be disclosed 

on further examination. If all radiographically disclosed weld defects must be 

eliminated from a vessel, then 100% radiography must be employed. 


UW-52

UW-52 (b1) Minimum Extent of Spot Radiographic Examination (1) One 

spot shall be examined on each vessel for each 50 ft (15 m) increment of 

weld or fraction thereof for which a joint efficiency from column (b) of 

Table UW-12 is selected. However, for identical vessels or parts, each 

with less than 50 ft (15 m) of weld for which a joint efficiency from 

column (b) of Table UW-12 is selected, 50 ft (15m) increments of weld 

may be represented by one spot examination. 

Table UW-12 

Type 

number 

2 

1 

Joint 

Categorie 

s 

A, B, C & 

D 

A, B, C & 

D 

A, B & C 


Examination. 

(a) Full 

1.00 

0.90 

0.90 

(b) Spot 

0.85 

0.80 

0.80 

None 

0.7 

0.65 

0.65 

One spot shall be 

examined on each 

vessel (or other 

identical vessels) for 

each 50 ft (15m) 

increment of weld. 


UW-52

This rule also addresses smaller, often machine welded 

vessels such as small air receivers. One is picked at 

random for spot radiography. If it passes, all are 

approved. 

One spot shall be 

examined on each 

vessel (or other 

identical vessels) for 

each 50 ft (15 m) 

increment of weld. 


UW-52

One spot shall be examined on each vessel for each 50 

ft (15 m) increment of weld. 


UW-52

UW-52 (b2) For each increment of weld to be examined, a sufficient 

number of spot radiographs shall be taken to examine the welding of each 

welder or welding operator. Under conditions where two or more welders 

or welding operators make weld layers in a joint, or on the two sides of a 

double-welded butt joint, one spot may represent the work of all welders 

or welding operators. 


UW-52

a sufficient number of spot 

radiographs shall be taken to 

examine the welding of each welder 

or welding operator. 


UW-52

Welder-C 

Welder-B 

Welder-A 

Under conditions where two or 

more welders or welding 

operators make weld layers in a 

joint, or on the two sides of a 

double-welded butt joint, one 

spot may represent the work of 

all welders or welding operators. 


UW-52

Every welder in a given 50’ increment must have his work 

radiographed. It can be a individual radiographed or a group 

picture. Here “welder A” was radiographed alone and 

welders B & C’s work was examined on the same radiograph. 

Welder-A 


UW-52

UW-52 (b3) Each spot examination shall be made as soon as 

practicable after completion of the increment of weld to be 

examined. The location of the spot shall be chosen by the Inspector 

after completion of the increment of welding to be examined, except 

that when the Inspector has been notified in advance and cannot be 

present or otherwise make the selection, the Manufacturer may 

exercise his own judgment in selecting the spots. 


UW-52

The idea of this rule is that each 50’ increment is to be 

a hold point for approval; the next increment is not to 

be started until the previous one has been accepted. The 

drawing below is the simplest case; you will not see this 

often. 

UW-52 (c) L=6” min. 


UW-52

UW-52 (b4) Radiographs required at specific locations to satisfy the 

rules of other paragraphs, such as UW-9(d), UW-11(a)(5)(b), and UW- 

14(b), shall not be used to satisfy the requirements for spot radiography. 

UW-9 DESIGN OF WELDED JOINTS 

(d) Except when the longitudinal joints are radiographed 4 in. (100 mm) 

each side of each circumferential welded intersection, vessels made up of 

two or more courses shall have the centers of the welded longitudinal 

joints of adjacent courses staggered or separated by a distance of at least 

five times the thickness of the thicker plate. 

4 in 

4 in 

five times the thickness of the thicker plate 


UW-52




UW-11 (a5b) Category B or C butt welds [but not including those in 

nozzles or communicating chambers except as required in (2) above] 

which intersect the 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 in accordance with UW-52. Spot 

radiographs required by this paragraph shall not be used to satisfy the 

spot radiography rules as applied to any other weld increment. 


UW-52




UW-14 OPENINGS IN OR ADJACENT TO WELDS 

UW-14(b) Single openings meeting the requirements given in UG- 

36(c)(3) may be located in head-to-shell or Category B or C butt 

welded joints, provided the weld meets the radiographic 

requirements in UW-51 for a length equal to three times the 

diameter of the opening with the center of the hole at mid-length. 

Defects that are completely removed in cutting the hole shall not be 

considered in judging the acceptability of the weld. 

Length equal to three times the 

diameter of the opening with 

the center of the hole at midlength. 


UW-52

UW-52(c) Standards for Spot Radiographic Examination. Spot 

examination by radiography shall be made in accordance with the 

technique prescribed in UW-51(a). The minimum length of spot 

radiograph shall be 6 in. Spot radiographs may be retained or be 

discarded by the Manufacturer after acceptance of the vessel by the 

Inspector. The acceptability of welds examined by spot radiography shall 

be judged by the following standards: 


UW-52

UW-52 (c) Standards for Spot Radiographic Examination. Spot 

examination by radiography shall be made in accordance with the 

technique prescribed in UW-51(a). The minimum length of spot 

radiograph shall be 6 in. Spot radiographs may be retained or be 

discarded by the Manufacturer after acceptance of the vessel by the 

Inspector. 

discarded 

Spot radiographic examination films 

discard after acceptance by the Inspector 


UW-52

UW-52 (c) Standards for Spot Radiographic Examination. Spot examination by radiography shall 

be made in accordance with the technique prescribed in UW-51(a). The minimum 

length of spot radiograph shall be 6 in. Spot radiographs may 

be retained or be discarded by the Manufacturer after acceptance of the vessel by the Inspector. 


UW-52

Spot radiographs may be retained or be discarded 

by the Manufacturer after acceptance of the vessel 

by the Inspector. 


UW-52

UW-52 (c) 

Degree of RT 


Spot 

1. indication characterized as a crack or zone of incomplete fusion or 

penetration. 

2. Welds having indications characterized as slag inclusions or cavities 

are unacceptable when; 

a. the indication length exceeds 2/3 t, where t is defined as shown in 

UW-51(b)(2). 

b. For all thicknesses, indications less than ¼ in. (6 mm) are acceptable, 

and indications greater than ¾ in. (19 mm) are unacceptable. 

c. Multiple aligned indications meeting these acceptance criteria are 

acceptable when the sum of their longest dimensions indications does 

not exceed t within a length of 6t (or proportionally for radiographs 

shorter than 6t), and when the longest length L for each indication is 

separated by a distance not less than 3L from adjacent indications. 

(3) Rounded indications are not a factor in the acceptability of welds not 

required to be fully radiographed. 


UW-52

UW-51 (b2) 

t = the thickness of the weld excluding 

any allowable reinforcement. For a butt 

weld joining two members having 

different thicknesses at the weld, t is the 

thinner of these two thicknesses. If a full 

penetration weld includes a fillet weld, 

the thickness of the throat of the fillet 

shall be included in t. 


UW-52

UW-52(d) Evaluation and Retests 

Spot RT unacceptable, 2 additional 

spots in the same increment 

Spot RT 

acceptable 

Both Spot RT 

acceptable 

Any of the Spot 

RT unacceptable 

the entire weld increment represented 

the radiographic testing is acceptable 

the entire weld increment represented by 

the three radiographs is unacceptable 


UW-52


UW-52(d2b) If either of the two additional spots examined shows 

welding which does not comply with the minimum quality 

requirements of (c)(1) or (c)(2) above, the entire increment of weld 

represented shall be rejected. 

1. The entire rejected weld shall be removed and the joint shall be rewelded 

or, at the fabricator’s option, 

2. the entire increment of weld represented shall be completely 

radiographed and only defects need be corrected. 

UW-52(d2c) Repair welding shall be performed using a qualified 

procedure and in a manner acceptable to the Inspector. The rewelded 

joint, or the weld repaired areas, shall be spot radiographically 

examined at one location in accordance with the foregoing 

requirements of UW-52. 


UW-52


UW-52(d a) If the two 

additional spots examined 

show welding which meets the 

minimum quality requirements 

of (c)(1) and (c)(2) above, the 

entire weld increment 

represented by the three 

radiographs is acceptable 

provided the defects disclosed 

by the first of the three 

radiographs are removed and 

the area repaired by welding. 

The weld repaired area shall be 

radiographically examined in 

accordance with the foregoing 

requirements of UW-52. 


UW-52


(1) 全部拍片 , 修 

复或 (2) 全部清 

除 , 重焊 , 再次执 

行抽样拍片 

UW-52(d2c) 


UW-52

Fion Zhang/ Charlie Chong

SUBSECTION B

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