Volume-2 Api510 Exam

3. API RP 572 Recommended

Practice

-

-.-_ L-.-_L•._JI!!!!IIIHI _l j ,._ ••••~_~~~_

VOLUME - II

1. ASME

SEC.

VIII Drv.1 Pressure Vessel code

2. API 510 Pressure Vesse! Inspection code

4. API RP 576 Pressure Reliving Devices

5. ASME Sec. IX Welding Qualification

Code

STUDY OF CODES AND STANDARDS

I

I

l ,

~ i.,;l ~

t,;)

~

,;J

-.J

;,;) ~ ~

;,:,

~

.~

~ ~ ~ ~ ~ ~ ~ ~ ~

o

o

,

,

,

,

r>

~

r>

,

~ ) ) ~ ) )

,

) )

•

~~I

~ ~ ~

'W

'W

W

~ ~ ~ ~ ~ ~ ;;) I

::)\

.;)

~

o

o

o

o

:)

:>

o

o

~

o

:>

:>

o

~

:>

o

o

;:)

:>

~

::>

,

"'

:>

~

;)

:>

')

-API -. 510 COURSE NOTES

VOLUME

-

I I

~--STUDY OF

ASME See,

VIrI

Div, 1

CONTENTS

3 .

MATERIAL

OVERVIEW

6.

INSPECTION

&

TESTING

7.

NDE OF PRESSURE VESSELS

STUDY OF

ASME See.

VIII

Div. 1

1.

AS~1E BOILER

&

PRESSURE VESSEL CODES

2.

INTRODUCTION

TO ASME SECTION VIII DIV.

4.

DESIGN

OF PRESSURE VESSEL

5.

FABRICATION

REQUIREMENTS

8.

CODE STAMPING AND REPORTS

::---~---==..

_._=__h_ .._

-~ \) \) ~ ~ ~

-.)

~ ~ ~

D

:>

,

~

:)

,

,C

,

,

:>

,

) )

>

•

)

•

•

,

9.

TOPICS FROM ASME SEe. VIII ON. 1 FOR

1.

ASME BOILER & PRESSURE VESSEL CODES

11 INTRODUCTION ASME Codes give stipulations and guidelines for !he design, materials, manufacture and testing of pressure vessels. These are issued by the American Society of Mechanical Engineers, New York. The codes were first issued in 1915. Since then, many changes have been made and new sections added to the code as need arose. It is a LIVE code and is revised and updated periodically. It keeps pace with time and is responsive to its users.

In its present from the ASME Code System is a follows:

Material specifications. Ferrous materials, Non Ferrous Materials

Welding rods, electrodes, filler metals. Material properties. " Power Boilers. Section I Section II Part A Part B Part C Part D 2) CODE SYSTEM Section 111 Section IV

Nuclear Power Plant Components.

Heating Boilers. Section V

Section V/

Section V/I

SecUo" VII/

Non destructive Examinations.

Care and operation of Heating Boilers.

Rules for care of Power Boilers

Division 1 - Pressure Vessels

Division 2 Alternative Ru!es ( Pr Vessel) Division 3 Rules fer constructive of High

Pressure Vessels

\fl'e/ding and Brazing Qualifications

r--'~)erglass reinforced Plastic Prc:s::;urc

\ '.':;sols

, ,':S for in service; IfIspectlon ,,' r011Cli::21

-~ ~ ~ , ~ ~

-.;

~

3) ISSUE FREQUENCY : ASME Issues complelely new edilion of all Sections aftor

three years on 1" of .July of the year 01issue. Latest edition was issued on : 1sl July 2001. Addenda to the latest edition are

issued on 1slJuly every year.

2001 Edition with 2001 Add. _1slJuly 2001 .

. 2002 Addenda - 1stJuly2002 .... (A 02)

2003 Addenda 1slJuly 2003 ... (A03)

A fully revised edition incorpOraling all above addenda would be issued on 1sl July 2004.

4) APPLICABILl1Y The editions and addenda become applicable after six months

from date of issue. Thus, for 1" Jan. 2004 to 31 Jan,200A, Ihe construclion of Pressure Vessels shall be as per 2001 edition

and 2001 +2002 addenda. However, for old C<Jntracls s pi IIing

OVer beyond 1" Jan 2004, the applicable edition and addenda which were valid at the date 'of signing contract are valid till end of contract.

5) CODE INTERPRETATION: ASME issue Wrilten replies know as "Interpretations"

to

the inquiries concerning technical aspects of the code These are issued twice in a year (July and December) and are sent to "Edition - SubsCribers" as up-date service.

6) CODE CASES

Boiler and Pressure Vessels Committee meets regulany to consider propOsed additions and reVISions to Ihe Code. At the

same lime iI may formulate Code cases to clanly , Intenl' of eXlsl"'9 requlrenlenls These are Published as COde.Case bOOks "is PubliShed along with ne".' editions and Supplemenls arc .. "IOnlallcally Sent '0 subscnbers of Code case book iiIl new eeJ/tlon ISPUb/IS/led

7) Co () E SlAMe' , C "cllfiel I,' of ""If """ atIon 10 US2 S 12"'.0S IS granled by /. S M [

Mani.Jfacturei".s· 1;::lcilXties. and organization are subj,ected to joint review by representative of inspection agency and ASME Designee before granting authorization.

---n

(

I

i

The ASME Codes have attained legal status in most of the American States, who have adopted them and made them mandatory Codes of practices in tfle interest of safety. All the boilers and pressure vessels niade to ASME Code Section I (power bailers), Section VIII Div. 1 & 2 (unfired pressure vessels) and Section III (nuclear vessels) . need to be fabricated by approved Works who hold code stamps in recognition of their operating quality system. These equipments are inspected and certified by qualified ASME Authorized Inspectors.

SALIENT FEATURES OF ASME CODES

(

(

Every ASME COde starts with specifying the scope of the code in terms of capacity, size and pressure and other limitations if any. It 31so deals with and the battery limits and the areas of code jurisdictions.

The Codes categorize and classify acceptable grades for materials of construction, for specific applications covered by the codes. The codes also idei1tify and categorize various methods of construction Ifabrication.

The codes specify the required N.DT. and other inspections. They also specify the accept I reject criteria

What is most important about the ASME Code is that is covers a vast field of manufacturing activity without sermonizing. They are user friendly. and keep pace with changing technologies No wonder - the Users and the Manufactures wond over have adopted the ASME codes whole heatedly There are more boiler 2;ld pressure vesse:s built under ASME codes than those ur1der all other codes taf-:entogether

The participants are advised to refer the actual code clauses and extract If1formatlon from ti,e latest codes applicable ASME code is even evoivllig docUm2!lt and one h2s (c, refer to tile lalr;st Zlppllcable edltloll and addenda nlese notes Will help III

""Scope ; £xclusions

Following pressure vessels are not inciuded in the purview of ASME Sec.vl/l

Div.1

I. those covered by other sections.

II. Pressure containers whiCh are integral parts (or components) of rotating

machinery.

III. Piping System beyond battery limits

IV Pipe fitlings, valves, pipe components and other accessories, beyond

battery limits.

v. Vessels with incident loading of external or internal operating pressure not

exceeding 15 psi (No lirnitations on size).

Vessels having inside diameter or width/heighUcross section diagonal not

exceeding 6" (No limitations on length or pressure) Vessels for pressures exceeding 3000 psi.

Vessels for Human OCCupancy

2.

INTRODUCTION TO ASME SECTION Viii Diy. 1

Scope of the Code; ASME Section VII Div. 1 ;

199J!:

Definition of a pressure vessel as per Code:

Containers for containment of pressure (external or intemat), obtained from an external source, or by application of heat (through direct or indirect Source), or by combination thereof. ASME Sec. Vtll Oiv 1 covers mandatory requirements

specific prohibitions, and non - mandatory gUidance for pressure vessel

materials, design, fabrication, examination, inspection, testing and certification.

VI. VII VIII

(

~ ~ lll,) ~ ~

.J

..'>

.,) ~

;J

;,

;,

,

~

:>

)

)

(

) ) ) ~ ~:

Un;" 'octSleam 80d,,,s (W"11 press"," rehef devices as per ASME See II

['i'::;);)rators & 1-i'22t f:::XC!1dilCj8/S

Unfircci (Prucess i~c.Jt generated) steam boilers.

Responsibilities:

Code Composition:

General Requirements:

ii. Inspector's:

(a) Monitoring quality control.

(b) Verification of design calculations. (c) Conducting specified inspections. (d) Code stamping.

(e) Certification.

Battery Lir:!lJ!:~

(a) F~r externai :.;onnections

I. Welding ends, for welded external connection II. Threaded joints for screwed connections III. First Flange face for bolted connections

IV. Sealing surface for proprietary connections (b) Weldment of pressure part to non-pressure part. (c) Manhole and handhole covers - fOr vessel openings. (d) Sealing surfaces for instruments, gauges, etc.

The code content is organised in 3 sub-sections and two Appendices as follows:-i) Sub-section A - General Requirements

ii) Sub-section B - Requirements pertaining to methods of fabrication Iii) Sub-section C - Requirements pertaining toclasses of materials IV) Mandatory Appendices

v) Non-Mandatory Appendices

Desiqn

The User shall assure hiniself that the design. matprial and constn.ictioll of the vessel. will be suitable for Intended service, with respect to s8fety, intended penar'mance, retention of satisfactory mechanical properties, and protected from (jetC:'flOratlon during t:le vessel's Illtended service life /.1., relatively 111gh"factor of I. Manufacturer's:

(a) Compliance of all requirements of Code by himself, and by all others (ie. Vendors)

(b) Providing proper certification of materials and construction. (c) Providing applicable design calculations.

(d) Establishing a mandatory Quality System.

b

...

_..__. __

....

__

.. __

...

_..

b

~

w

~ ~ ~ ~ ~ ~

;)

;)

,

~

:>

;)

;)

(

o

:>

D

:)

~

l)

:>

~ ) )

)

(

) ~ ) ) ) ) i j-~

General Principle:

A vessel may be manufactured by any process which shall not unduly impair the inherent material properties or jeopardize tl1e safe, reliable and optimum

performance of the vessel.

•

₎ ) ~ ~ ) > ) ) . --.--.'-.. -., --"- ---...-..,~

safety" (previously 4, prQ~ently 3.:5) is ddQr.:.~(.;

material abuse: during construction and serviCE:.

;.::' :.a'-l.ecare of the incidental

(

Methods of fabrication: requirements are Getailed in subsection B UW for welded vessels

UF for forged vessels UB for brazed vessels ULW - for layered construction

[Alternative Rules]

ReqUirements based on materials:

Requirements based on materials adopte-J and other specifications are referred to in the following clauses of subsection C of the ASME Code Section VIII Divn.1. The stress values have been tabulated in the Part '0' of Section II.

UCS - for Carbon and low alloy stecis UH.~ - for high alloy (stainless) steels UNF - for non-ferrous materials UCL - for clad materials

UHT - for high tensile, heat treated Ferritic Steels (such as Q & T) UCI & UCO - for Cast Iron & Cast Ductile Iron Steels.

UL T for low temperature appliC3tion using materiais of permissible stress values

(

/

3.

MATERIAL OVERVIEW

COMMON ASTM SrECS. FOR C.S. PLATES

Sr Plate

No Spec. Composition % En~~. properties

C (max) P (max) S (max) Si Mn _{T.S. Y.S.} (x1000 (x1000 psi) psi) Elog 0/0 A36 0.26 0.04 0.05 _{58 - 80 36 20} ') A283Grc 0.24 0.04 0.05 _{55 - 65 30 25} L 3 A285Grc 0.28 0.035 0.045 0.90' 55 - 75 30 28

(

(max) 4 A515Gr60 0.24 0.035 0.04 0.15 - 0.90' 60 - 80 32 25 0.30 (max) Gr70 0.31 0.035 0.04 0.15 - 0.90' 70 - 90 38 21 0.30 (max) 5 A516Gr60 0.21 0.035 0.04 0.15 - 0.8 - fiO - 80 32 25 0.30 1.25 Gr70 0.27 0.035 0.04 0.15 - 0.8 - 70 - 90 38 21 0.30 1.25 Remarks:

-Structural Quality Plates & Shapes. (

l

,..,

/

Structural Steel for Bending I Forming (Low & Med T. S )

Plates may be ordered as rolled or norm (P V plates, Low & Med. T. S)

Plates >= 2" thk Must be normalized for < 2" purchaser's option

(P V plates, High & Med Temp service)

f'lates >= 15" ttlk Must be normailled for < 1 5" purchaser's option

W V plates, Moderate & Low Temp service)

~ ~ ~ ~

SELECTION OF

CARBON & ALLOY STEELS

BASED ON

~

.

SERVICE TEMPERATURE

~ ~ !~ STEEL TYPE SPECIFICA TIONS TYPICAL TEMP. ~ LIMIT (DEG. F)

i;)

MODERATE TEMP.

0

_1. C - Steels SA 285 grC (3/4 in. thk max) 600 (max)

0

SA 515 All Grades

0

SA 516 All Grades 775 (max)

~

0

.ELEVATED TEMP

:"

2. _{C - 1/2 Mo} SA 204 gr 8, C 875 (max) ~ 3. _{C - 5/4 Mn - 1/2 Mo} SA 302 gr 8 875 (max) ~

(

~ 4. _{1/2 Cr - 1/2 Mo} SA 387 gr 2 1000 (max) ~ 5. _{1Cr - 1/2 Mo} SA 387 gr 12 1100 (max) ~

,

6. 5/4 Cr- 1/2 Mo - Si SA 387 gr 11 1150 (max) ,,

,

,

7. _{9/4 Cr - 1 Mo} SA 387 gr 22 1200 (max) ~ LOW TEMP

,

8. C - Steel (F. G.) SA 516 A.II Grades ( -50 ) ~ (Impact tested) ~ _9. 5/4 Ni Steels SA 203 gr A or 8 ( -90 ) ~

(

~ 10 _{7/2 Ni Steels} SA 203 gr C or 0 ( -150 )

,

~ ~RYOGENIC TEMP ~ 1 1 _{9 Nr Steel} SA 353 ( -320 )

,

~ p :'c;s:cnilrc SS S/\ 240 Type 304.3041,347 ( -425 ) ~ ~ o

~ ill '"

.,

~

••

.,

••

••

••

... 1/

"-••

•.. rI •.. rI

••

~ •• , '" ,I

"

, ~

,

₍

~ MA TERIAL REQUIREMENTS: GENERAL:

1. Material subject to stress due to pressure (i.e. pressure parts) shall conform to one of ttle specifications given in ASME Code Section II, ,md shall be limited to those that are permitted in the applicable Part (such as UCS,UNF,UHT etc.) of the subsection C.

2 Permitted Specifications for Plates, Forqinqs, Castinas, Pipes & Tubes, Fasteners, Rods and Bars are covered in the ASME Code Section II Part A (for ferTous materials)

& Part 8 (for non- ferrous materials). These are designated by a suffix SA for ferrous materials, and SB for nonferrous materials respectively. Materials are to be identified \Nith Certified Mill Test Certificates issued by Steel I Raw Material I Product

Manufacturer, and verified whether all requirements of the Specification and grade are complied with, before correlating with identification markings as required bythe relevant material specification.

3. "Partially" identified materials, where identification markings can be ascertained as being authentic, but material certificate is not available, or is certified to a Specification ilot permitted or not recognized by ASME Sect. VIII Div I, may bs accepted provide'd check analyses I tests are carried out on representative sample/s and satisfy Code appr'oved specifications. In such cases Vessel or part manufacturer needs to re-certify the material to the Specification and grade, based on the findings.

4 The maximum allowable stress values for different service temperatures for these

material specifications and grades are stipulated in ASME Code Section II Part D _ Properties of Materials.

5. Permitted Specifications for Weldinq ConsumaQles are covered by ASME Code Section II Pari C These specifications are give:l a designation number with a suffi\:

S:::.:\ or SFl3 for sUltat)le classification and grading

G. Preforned or Prefabricated Pressure Paris when made

by

otttcr litcHI tile=:pressure

Form U2. with .For welding con~urnabl"f., tht: marking or tagging of the materials, containers or packages, jf done as per the app.licable Consumable Specification, may be accepted in lieu of Certified Test report.

7.

Materials for pr.vessels (Section viii Div.1 stipulations)

General Requirements are discussed here for understanding purpose only. For specific query one should refer to applicable code book and addenda.

General Requirements Material types

(

a)

b) c) d)

Steel & Low Alloy Steels with max. 0.35% Camon High alloy steels ( stainless steels and alloys) Non ferrous (AI, Cu, Ni, Cu Ni, Ni Cu etc.)

Compatible welding Consumables ( ASME Section II Part C )

Product Forms and Typical Specifications

a) Plates (SA 515/516/240/285) b) Castings (SA 216/351/217/352) c) Forgings (SA 181/105/182 etc.)

d) Pipes & Tubes (SA 106/312) (SA 179/213) e) I=asteners (SA 193/194/307)

f) Bars & Shapes (Sections) SA 36/283/479

Max. Allowable Stress Values (MASVs):

MASVs at various service temperatures for each acceptable material specification are given in ASME Section 11- Part D.

f~or vessels designed to operate at low temperature, generally the MASV at 100 Deg F is used

TillS IS provlderj over and above tile thicknesses calculated for pressure vessels,

I;:, sed Ofl service experience All design calculations are required to be made

"lith V(~ss('1dimensions in corroded condition

, , , ,

(

(

Use of Structural Steels for pre$su,-e parts (Typica!ly. SA 36/ SA 283 )

a) Limitations:

i) not pennitted for lethal service

ii) should not be used for unfired steam boilers

iii) Design temperature only (-) 20 Deg.F. to (+) 650 Deg.F. iv) for thicknesses below 5/8" (160101) only

b) Testinq:

Each plate to check test for chemistry and physical properties.

( Tensile strength, Y.S., % Elongation and severe Bend test as per SA-6 requirements ).

a.Check Tests for materials used for pressure parts

a) Check test allowed only in the case of partial identification: b) Check test requirements

:-Each piece is tested for chemical composition & mechanical properties. Acceptance criteria as per pemlitted specification for which the material is being qualified.

Cast, forqed, rolled and die-formed pressure parts:

These shall be made from materials of permitted specifications; and should meeUor be suitable for design conditions of completed vessel. NOT [RT/PT/MT] and Heat treatment (Nonn/SR) as applicable must be conducted prior to its release for attachment to the pressure vessel. Partial data report (form U2) needs to be issued for such components. in ev:dence of code compliance.

f\rUJlundertolerance

a) Plates with 0.01 inch or 6% under tolerance (whichever is smaller) may be used for full desigr. ~ressure,

However If material specification allows greater under tolerance (eg

o

3mm for a 10mm thick plate), then ordered thickness for the matenal

SllOlilcJ IlC suffiCiently <:]reater'

'J I.

b) ::or pipe or tube

-·6j"der~tl

by'its nominal Well thickness, the manufacturing under tolerance shall be taken into account. For S.S & M.S. pipes, th0. manufacturing under tolerance is -12.5%. For M.S. tubes, it is zero (tolerance +20/-0). For S.S. tubes. The tolerance Iimit~ are given in a separate chart.

9.

MATERIALS FOR LOW TEMPERATURE SERVICES:

a) Carbon and low alloy steels : Impact test requirements with respect to minimum design metal temperature in service are explained in UCS-66 of ASME VIIl-1 See Fig. UCS-66 and UCS-66.1 for Carbon Steel and low alloy steel materials and weldments of comparable chemistry.

b) !JNF 65 : Non ferrous materials have marked resistance to lowering In impact values at subzero temperatures. As such no impact tests required upto:

i) ii)

iii)

Wrought aluminium :alloys Copper and copper alloys } : Nickel & Ni alloys }

Titanium and zirconium

-4250eg.F. (-254 Oeg. C) -3250eg.F. (-198 Oeg. C)

- 75 Oeg.F. (-60 Oeg. C)

c) UHA 51 : Austenitic Stainless Steels too exhibit notch toughness at cryogenic temperatures.

- For Types 304,304L,316,316L&347, upto -425 Oeg.F.(-254 Oeg. C) impact tests are waived.

- For Ferritic Stainless/High Alloy Steels like Types 409,410,430, etc, impact tests are required at any service temperature below -20

Deg F (-29 deg C)

(

(

A.

1 )

2)

3) --'-'---"'-'---' - •• '--- ••••.• • __ u__ ••• _

4. DESIGN OF PRESSURE VESSEL

BASIC REQUIREMENTS:

Minimum thicknesses of shell and

heads:-i) After rolling and forming - in qeneral 1.6mm (1/16") + corrosion allowance

(a) above not applicable to UHT materials & PHE Plates

(b) for unfired steam boilers: 6.4mm (1/4") + corr. allow. (c) for compressed air service: 2.4mm(3/32") + corr. allow. ii) Mill under tolerance

a) Plates with 0.01 inch or 6% under tolerance (whichever is smaller) may be used for full design pressure, instead of at the given design thickness ordered.

However if material specification allows greater under tolerance (e.g. 0.3mm for a 1Omm'thick plate), then ordered thickness for_, the material should be sufficiently greater.

b) For pipe or tube - ordered by its nominal wall thickness, the manufacturing under tolerance shall be taken into account. For S.S-& MS. pipes, the manufacturing under tolerance is -12.5%. For M.S. tubes, it is zero (tolerance +20/-0). For S.S. tubes it is given in separate charts.

Quality factor for Castinqs

A quality factor of 80% is multipled to allowable stress values for castings when computing design thicknesses.

Shapes covered by the Code:

For Vessels of cylindrical and spherical shapes, ASME Code Section VIII Div.1 provides design rules in the general sub-section [Part UG] For vessel ends, hemispherical, ellipsoidal, and torispherical shapes are preferred over flat ends For transitions, loriconical or conical shapeS are preferred (in that order)

Other s!lapes arc corlsidered unconventionClI and condltioflS for design, construct/orl :lflcj safe operation are set forih in Clause U-2 (g)

4) COjrn~i.':.!ll':~'"'\:=E~c.~-:

The US(;:" shall specify corrosion allowance tor vessels subject to thinning by

corrosion, erosion or mechan:cal abrasion - to be provided for the desired life of the vessel, by a suitable increase in the thickness of the matenal over that detennined by the design formulae.

5) Tell Tale Holes:

Tell Tale holes are used to provide some positive indication when the thickness has been reduced to a dangerous degree. Tell Tale holes of 1/"(6" to 3/16" diameter and to a depth of not less than 80% of the thickness of the seamless shell, are provided on the Opposite surface to that where deterioration is expected.

In clad or lined vessels, through-thickness tell tale holes of 1/16" to 3/16" dia are provided, and are also used for leak tightness of welds attaching linings to the parent metal.

For lethal service vessels, tell tale holes are prohibited.

Note: Vent holes are made for lug attachment pads, bearing pads etc. to allow welding gases to escape. Test holes made for example on reinforcing pads, have internal threads for fitting nipples for air tests, and also act as Vent holes. , 6) Openinqs for Drain:

Vessels subject to corrosion shall be provided with a suitable draiil opening at the lowest point practicable in the vessel; or_a pipe may be used extending inward from any other location to within 1/4" of the lowest paint.

7) Lininqs:

Corrosioil resistant or abrasion resistant linings, whether or not attached to the wal! of the vessel shall not be Considered as contributing to the strength of the vessel wall.

Exception: Vessels designed to Part UCL of the Code 8) Desian Temperature of V~ :

i) Maximum Temperature is the rT:eanmetal telnperature-through th:cKness-eXpected under operating conditions.

iii) iv) ( _v)

"

vi) viii)

10) Maximum Allowable Stress Values:

a) These are the maximum unit stress permitted in a given material used in the / construction of the vessel as per the Code.

In ASME Code Section VIII Div.1, the maximum allowable stress values for temperatures of minus 20 Deg.F.to 650 Deg.F., [and in particular for 100 Deg.F. ] are generally equivalent to Ultimate Tensile Strength divided by a factor of safety of 3.5 (approx). or t\vo-third of yield str~ngth whichever is lower, refer ASME Section 11-0

(

9)

11 )

Desiqn'Loadinqs :

i) Internal or ExtArnal Design Pressure.

ii) IJead Weight of the Vessel: Weight of the vessel and normal contents of the vessel undAr operating or test conditions [including additional pressure due to additionarwei~Jht due to static head of liquids].

iii) Super imposed static reactions - from weight of attached equipment [such as motors, machinery, other vessels, piping, linings, insulation].

iv) Loading due to attachment of internals, vessel supports, lugs, rings, skirts, saddles and legs.

Loadings due to cyclic and dynamic reactions owing to pressure variations or

temperature variations, or from equipment mounted on the vessel and mechanical loadings.

Wind,snow,and seismic reactions,where applicable. Impact loadings due to fluid shock.'

Loadings due to temperature gradients and differentiai them1al expansion.

Thickness of shells under internal pressure:

A cylindrical shell is Subject to, a circumferential stress along its longitudinal seams, and a longitudinal stress along its circumferential seams. The incidental CirCumferential stresses are almost t\vice as much as the longitudinal stresses in any given v~ssel. Tnercfore we need to calculate only the thickness required to sustain the Circumferential stress, along the longitudinal seams, for tile given deSign conditions [design pressure Jnd design temperature] Ttle formula is valid

I .

(

12)

when P does not exceed 1/25SE and thicKness does not exceed one-half of the inside radius.

a) For cylindrical shells: (Using inside dimensions)

t, inches = P x Ri / (SE - 0.6P) or P = SEt I (Ril + 0.6t) where - 'f is the corroded min. thickness of shell, inches

'Ri' is the inside radius of the shell, inches (corroded) 'Ro' is the outside radius of shell, inches (corroded)

'P' is the design pressure in psig

oS' is the maximum allowable stress value in tension, psi .E' is the Joint Efficiency [Refer to Table UW-12 ]

Di is Inside diameter of shell (corroded) Do is Outside diameter of shell

b) Alternate Formula for cylindrical sh.ells : (Using outside dimensions)

t, = P x Ro I (SE + OAP) or P = 2SEt I (Ro - OAt)

c) For spherical shells: (Inside dimensions)

t, = P x Ri / (2SE - 0.2P) or P = 2SEt / (Ri + 0.2t)

[ Limitations: thickness shall not exceed 0.356R P shall not exceed 0.665 SE ]

d) Alternate formula for spherical shells: (Outside dimensions) t, inches

=

P x Ro / (2SE +O.8P) or P-= 2SEt / (Ro _ 0.8t)

Spherical shell formulas are valid when thickness does not exceed O.356R, or P does not exceed 0.665 SE.

Thickness of shells and tubes under external pressure:

Cylindrical shells, tubes and spherical shells under external pressure are subject to buckling loads, either owing to internal vacuum and extern a! almospheric V'?Ssllre, or owing to a differential pressure acting externally.

S,;C!l vessels need stiffening supporis, and the unsupported span between the c,'ffc:lr;rs (I), deCij0:S tlie vessel tllickness Ti,e I\ppenciix-') of ti,e Code

14) ,LQintEfficiencies

b) For Torispherical Heads: (when r== 0.06 xL)

t, == 0.885 x P x L / (SE - 0.1 P) or P== SEt! (0.885L +0.1t) - Alternate Formula for Torispherical Dished Ends (when r> 0.006L) t, == P x L x M / (2SE - O.2P) or P== SEt / (LM + O.2t)

where L== inside spherical crown radius M == 1/4

x

[3 + (L /

r )

1/2

. r== is the inside knuckle radius in inches.

Limitations Knuckle radius shall nol be less than 6% of inside crown radius [ Ri ], nor less than three times knuckle thickness. Ri shall be less than Do. 13)

-pmvid0.s V~n·::'·.",:....::;:ui:: ~liV;;1g 'la!Lit, (·f Do !t, piolted agai:l':it I .•• Do, '{{here' Do' is the outer diameter of tt;e v~$seLiRefer UG-28

or

ASME Section VIII Oiv.1

J

Thickness of FORMED HEADS with Pressure on Concave Side

The required thickness at the thinnest point after forming of ellipsoidal, torispherical & hemispherical heads under pressure on the concave side shall be computed by under noted formulae:

a) For Ellipsoidal Heads: ( 2 : 1 type)

t, == P x Oi / (2SE - 0.2P) or P== 2SEt / (Do+0.2t)

Alternately.

t== Poo / (2SE + 1.8P) or P== 2SEt/ (0 _1.8t)

A good approximation of 2 : 1 Ellipsoidal head is one with knuckle radius of 0.17oi and spherical radius of 0.90oL\

c) For Hemispherical Heads: The formula Hemispherical shell can be adopted

Joint Efficiency 'E' referred to above are chaned out in T2ble UW-12 as :opplicable to weld jOints completed by an arc or' gas welding process. Joint efficiency depends on Ihe Iype of joint and on Ihe degree of radiography -2Xamlnatlon of the jOint. Table UV"'~2 of ASME Code See. Viii Div. 1 details !Olnl deSCriPtion, IIOlilations, JOint categories and degree 01 rOdiography ·::examination for each type number [Type 1 to Type 6 ) of the \','eld seam. Fig

b) ~

,

'(

) ) ) ) )

•

>

---.- ....--_ .. _h __ ._. ._._....~

15) Formed Heac.s, Pressure on Convex Side,

The required thickness at the thinnest point after forming of ellipsoidal, tori spherical or hermispherical heads shall be greater of the following ._. thicknesses

a) The thickness as computed for heads with pressure on the concave side as given in (13) above, and,

b) Thickness as computed by the procedure given in UG-28 and Mandatory Appendix-5 for Heads.

16) Minimum Thickness of Unstayed Flat Heads and Covers: t,

=

0

x [

CP I SE ] 112

where C

=

a factor depending upon the method of attachment of the flat head

o

=

Inside diameter of shell inches.

The above formula is applicable to both welded and bolted methods of attachments. Extra moments applied to the cover by bolting, are to be incorporated.

17) Openinqs in Pressure Vessels:

a) Shape of the openings: Openings in cylindrical and conical portions of" vessels, or in formed heads, shall preferably be circular, elliptical or obround. Openings of other shapes shall be provided with a suitable radius at all comers.

Size of the openinqs : Properiy reinforced openings, in cylindrical shells of diameter of upto 60 inches, shall not exceed half the vessel diameter, and in any case not over 20 inches. For vessel diameter of over 60 inches, the openings shall not exceed 1/3rd the vessel diameter and in no case eXceed 40 inches. For larger openings, supplemental rules apply.

18) ~nforcement of Openirlqs :

a) Beinfo~ent required f~in!:]sifls!lell~_§<JJeads

The principle is that material removed shal! be equal to material added. T/lis IS achieved by providmg doubling plate either outside or inside the

"

rI "-•.. ••• r ~

~(

,

,

,

)

,

~

,

b)

c)

d)

The limitatior.s am, on the .out6:- diameter of the doubling plate,; which shall not be greater than twice the size of the fini:;hed 9pening, and its thickness shall not be greater than the provided thickness of the shelllhead.

Credit is given to corroded size of the nozzle neck of the opening, fillet welds provided inside and outside, and at the outer edge of the reinforcing pad, to the additional thickness available in the shell and the nozzle neck, and to 2 1/2 times the thickness of the nozzle neck protruding outside and/or inside the shell.

Reinforcement waived for sinqle openinQs, in the case of,.

finished opening size 3 112" diameter in shell or head of thickness 3/8" or less;

finished opening size 2 3/8" diameter in shell or head of thickness

over 3/8";

Threaded studded or expanded connectio.ns where hole cut in the shell or head is f!Ot more than 2 3/8" diameter.

Openinq may be located throuqh a welded circumferential seam ioints, provided the weld is fully radiographed for a length equal to three times the diameter of the opening with the center of the hole at mid-length.

Openings ( without added reinforcement

J

in a shell plate, shall not be placed near the edge of the weld in the main joint, closer than 1/2 inch, for plates 1 1/2 inch thick or less.

Reinforcement of Multiple Openinqs: ::

Combined reinforcement can be provided for multiple openings, provided the minimum distance between centers of any of these two openings is 1 1/3rd times their average diameter and the area of reinforcement between any two openings is atleast equal to 50% of the total required fo, the two openings.

When the distance between the centers of any two openlllgs is less thall

; i13rd times their average diameter, then no credit for reinforcement is a:lowed for materials between these openings, and supplemental rules ne,,":cJ to be applied

For larger openings, higher value of

C

(in 16 above) and increased thickness of flat heads shall be provided.

Nozzle Neck Thickness:

Wall thickness of a nozzle neck shall not be less than, the GREATER of the following (a) or (b) :_

e) Reinforcement for OpeninQs if Flat Hea~ :

i) So far as the opening in a flat head does not exceed one half of the flat head diameter (or the shortest span),it shall have a total cross

sectional area of reinforcement not less than that given by 'A', where, A = 0.5 x d x t;

d

=

finished Qiqmeter of the circular opening

& t= nominal thickf)~ss of the vessel wall

In olher words, the fial head may be required to be thicker by the amount of reinforcement required.

/

"Ole pe, ten square feet or a rraclion II'", eof of inrerna' veSsel s",face

a) thickness computed for applicable design,mnrlitions .as per the formulae, plus corrosion allowance, .

t=PRi/SE-O.6P,OR t= PRO/SE+O.4p

b) the smallest of the following:

(i) calculated thickness (plus corrosion allowance) of the vessel or head on which nozzle is located with E :: 1.0.

(ii) the minimum thickness of the standard wall pipe (Schedule 40 of ANSI 8 36.10) plus corrosion allowance.

Insp~n OpeninQs :

All pres su, e vessels for use with compressed Gir, and Ihose subject to internal ca'Tosion, erosion or meChanical abrasion are reqUIred to be prov'ded \<;th SUitable manhole, handhole, or other inspection openings ror examination and

Cleaning

Inspection openings are waived.

a) fo, vessels upto 36" II), if lell-tale hales a'e provided at a spaCing of one 19) 20)

,

j ) ) ~ ~ ~ ~ ~ ~ ~ ~

;,

j ~

;:)

'(

,

,

~

-.?'~----'.'--'---~--~_

.. -. --.-..

-.--.-.-Welded Joint Efficiency Values (UW -12)

a/2a, with a minimun: 01 ~';'-ii'l,~ifr..nnly SP<lc(;.J holes. This excejJtion is not for compressed air vess'els.

b) for shell side of fixed tube heataxchangers; c) other exceptions are detailed in ~G-46 C, 0 & E.

.

d) for sizes of mandatory inspection openings: see UG-46F. Permissible Out-Of Roundness for Shells and Formed Heads: a) For internal pressure,

(Oi Max - Oi Min) divided by Oi Nom = 1% Max.

b) For external pressure, Refer Fig.UG-80.1 : Max. plus/minus deviation' e', from true circular form, shall be between 0.020 t to 1.0 t, as plotted on the curves with Do / t on Y axis a,nctu Do on X axis, where L = design length. c) Heads: out of profile + 1 1/40/ _ 5/8 0

for Hemispherical Head, use L=0.50 in the ratio UOo.

~ ~ >'t.) ~ ~ l~

,.;>

~ ~

.;>

;)

~ ~

:>

:>

,

,(

) ) ) ) ) ) )

(

21 )

Type of joint and radiography

1) Double-welded butt joints (Type 1)

Fully radiographed Spot-radiographed No radiograph

2) Single-welded butt joints

(backing st;-ip left in place) (Type 2)

Fully radiographed Spot-radiographed No radi8gr2ph

3) Slr1gle-welded butt jOints (Type 3)

Efficiency allowed percent 100 85 70 90 80 65

b .__

._

~ ~ ~ ~ ~

5.

FABRICATION REQUIREMENTS

1. GENERAL (UW - 26)

(a) The rules in the following paragraphs apply specifically to the fabrication of pressure vessels and vessel parts that are fabricated by welding. These shall be used in conjunction with the general requirements for Fabrication in Subsection A, and with the specific requirements for Fabrication In

Subsection C that pertain to the class of material used.

(b) Each Manufacturer or parts Manufacturer shall be responsible for the quality of the welding done by his organization. He shall conduct tests not only of the welding procedure to determine its sUitability to ensure welds 'Nhich will meet the required tests, but also of the welders and welding operators to determine their ability to apply the procedure properiy.

~ .

(c) No production welding shall be undertaken until after the welding procedures which are to be used have been qualified. Only welders

_,

and welding operators who are qualified in accordance with Section IX shan be used in Production.

(d) Welders not in the employ of the Manufacturer (Certificate of Authorizatr;~ Holders) may be used to fabricate pressure vessels constructed in accordance with this Division, provided all the following conditions are met.

(1) All COde construction shall be the responsibility of the Manufacturer. (2) All welciing shall be performed in accordance with the Manufacturer's

welding procedure specifications vvhich have been qualified by the Manufacturer in accordance with the requirements of Section IX.

(3) All welders shall be qualified by the Manufacturer in aCQxdance with the requirements of Section IX.

(4) The Manuf8cturer's Quality Controi Sysiern shall include as a minimum:

(0) a reqlcirement for complete and exclusive administrative and technical supervision of all welders by the Manufacturer;

(I)) evidence of the Manufacturer's authority to assign and remove welders at his discretio:l without involvc:rnr:nt of211y other or!C3ni?3!ir

n,:

.

~

'->

_')..l ~

'->

,.~ "~

.

..,) ~

;;.)

;;,

~

::;

;;J

;:,

~ ,r ~ ~

,

,

:>

,

:>

) )

•

•

l(

I

IC"

(c)

a

requirement for Assignment of Welder Identification sy1!111bQts: (d) evidence that this pro~ram has been accepted by the Manufacturer's

Authorized Inspection Agency which provides the inspection service. (5) The Manufacturer shall be responsible for Code compliance of the vessel

or part, including Code Symbol stamping and providing Data Report Forms propeny executed and countersigned by the Inspector.

2. QUALIFICATION OF WELDING PROCEDURE (UW-28)

(a) Each procedure of welding that is to be followed in construction shall be recorded in detail by the manufacturer.

(b) The procedure used in welding pressure parts and in joining load-carrying nonpressure parts, such as all permanent or temporary clips and lugs, to pressure palis shall be qualified in accordance with Section IX.

(c) The 'procedure used in welding non pressure-bearing attachments which have essentially no load~carrying function (such as extended heat transfer surfaces, insulation support pins, etc.), to pressure parts shall meet the following requirements.

(1) When the welding process is manual, machine, or semiautomatic, procedufE~/ qualification is required in accordance with Section IX.

(2) When the welding is any automatic welding process performed in accordance with a Welding Procedure Specification (in compliance with Section IX as far as applicable), procedure qualification testing is not required .

(d) Welding of all tes~ coupons shall be conducted by the Manufacturer. Testing of all test coupons shall be the responsibility of the Manufacturer. Qualification of2 welding procedure by one Manufacturer shall not qualify

that procedure by one Manufacturer except as provided in QW - 201 of Section IX

Wtiere. ~ ~ ~

:')

~ ~ ~ ~ ~

~C

~ ~ '~ ~ ~ ~ ~ ~ ~ ~ .~ '~ i~ i~ J~ .

.,

'~

,"'

J"

"j

,

'3

;~ ~

3. FORMING SHELL SECTIONS AND HEADS:

Thr: following provisions shall apply in addition to the general rules for fanning

UG-79,-• Carbon and low alloy steel plates shall not be formed cold by blows.

C) Vessel shell sections, heads, and other pressure boundary parts of carbon and low

alloy steel plates fabricated by cold forming shall be heat treated subsquently when the resulting extreme fiber elongation is more than 5% fonn the as-rolled condition and any of the following conditions exist.

(1) The vessel will contain lethal substances either liquid or gaseous (see UW-2). (2) The material requires impact testing.

(3) The thickness of the part before cold fonning exceeds 5/8 in. (16 mm). , (4) The reduction by cold forming from the as-rolled thickness is more than 10%.

(5) The temperature of the material during forming is in the range of 2500F to 9000F (

121°C to 482°C).

The extreme fiber elongation shall be detennined by the following fonnulas :

For double curvature (for example, heads),

% extreme fiber elongation

=

(75t1R) (1 - Rtr)

for single curvature (for example, cylinders),

% extreme fiber elongation

=

50 tlR) ( 1 - Rtr)

T = plate thickness, in.

Rr = final center line radius in.

R = original center line radius (equals infinity for flat plate), in

VVhen 'lesser shell sections, heads, or other pressure boundary paris of canJon or low alloj' steel plate are cold formed by other than the Manufacturer of the vessel, the rCOurr8d cerLlfication for tll8 pari sllalllndlcate wllCther or not the pari tldS been heat

')(~ '. J

4. GENERAL PRECAUTiUj\lS IN FABRICATION

(

I. ii. III. IV. v. VI. VII. viii. Tests

Structural discontinuities should be avoided. Square comers of pads should be fOunded off before fitment and welding . Unweldeci faces of-flame cut edges should be ground smooth and sharp edges ground round.

Welding of minor items direct to structural and pressure parts should be avoided. Use of intermediate I doubling pad is preferred.

Toes and brackets and ends of stiffeners should land on stiffened plating Fillet welds should be carried around attachments to avoid points of stress concentration.

Weld sequence should be planned before hand. Welding should progress towards free edges all the time to avoid shrinkage stresses. Back step welding, s~<ipwelding, low heat input, minimum weld deposits will prevent deformation and local bulking.

Shrinkage allowance for main seam should be provided for at the fitup stage, in order to obtain final dimensions within tolerance limits.

Avoid all kinds of metallurgical and mechanical notches.

/

Structures are subjected to direct or compressive proof load to check their buckling strength. Pressure vessels are subjected to tensile loading by means of a test pressure. Ability to withstand such loading is the proof of their integrity. Equipments under test should be adequately supported. P(essure gauges should be c31ibrated and verified for accuracy, with a "master" traceable to national standards.

5. CRITICAL AREAS IN WELDING FABRICATION

1. Climatic Conditions for Weldino

hio welding of any kind shall be done beloVi base metal temperature of 0 deg F. Between 0 dcg F and 32 dcg F, pretleating to 60 deg F - i.e warm to hand, is recommended prior to vicldlilq

(

ALIGNMENT TOLERANCES (Table UW-33)

Section Thickness, in.. _{: Joint categories}

A 8,C&D

Upto 1/2, inc!.

1/4 t _{1/4 t}

Over 1/2 to 3/4 inc!. _{1/8 in.}

1/~t

Over 3/4 to 1 1/2 inc!. _{1/8 in.}

3fi 6 in

/'

Over 1 1/2 to 2, inc!. _{1/8 in.}

1/8 t Over 2 Lesser of _{Lesser of} 1/16t or 3/8" _{1/8t or 3/4"}

(

2. 3.

Further, wht=:nsurfaces are wet or covered with ice, or when snow is falling on the surfaces to be welded, or during periods of high wind, no welding should b..:~ done unless welders and the wort< are properly protected and covered.

Cuttinq, Fittinq and Aliqnment

Gas cut edges for welding should be smooth, uniform, free of loose scale, slag, oil, paint\ etc. prior to welding. Preferably they should be ground down to bright metal and slightly preheated.

Welding edges of plates should be aligned and retained stress-fr~ in position during welding operation, by using tack welds, clamps, etc. Tack welds should be examined visually for defects, which if found shouJd be removed.

NOTE: Offsets within allowable tolerance shall be given a minimum of 1:3 taper transition, if necessary, by adding additional weld metal.

Finish of the Lonqitudinal and Circumferential Seams:

Butt welded joints shall have complete penetration and full fusion. Seams shall be free from coarse ripples, grooves, overlaps, abrupt ridges and valleys, undercut or underflush.

Mat'I Nom.Thk,in

Maximum Reinforcement, in.

C.Seam in pipe & tubing Other Welds

i i -!

(

Less than 3/32 3/32 to 3/16, incl. Over 3/16 to 1/2,incl Over 112 to 1, incl. Over 1 to 2, incl. Over 2 to 3, incl. Over 3 to 4, incl. Over 4 to 5, incl. Over 5 3/32 1/8 5/32 3/16 114 1/4 1/4 1/4 5/16 1/32 1116 3/32 3/32 1/8 5/32 7/32 1/4 5/\6 6_ ( , 4. Fillet Welds:

Fillet welds shall have adequ'ate penetration into the base metal at the root and side Viall of the weld joint. Reduction of the base metal thickness at the fillet weld toe is not permitted.

1_ Distortion Control: /'

One has to keep a close eye on distortion of the weldments, as many times, a good and sound weld with all NOT cleared in first go leaves the product rejected from distortion point of view.

Control of weldinq -- a Special Process

In short, there is a vast difference in Quality Control of Welding fabrication inspection and other inspection activities. In welding fabrication, systematic monitoring of activities from material procurement to packing and delivery stage has to be ensured byQ_ C_personnel to achieve the results_

6_ VVELD REPAIRS

Vessel or parts of vessel which are to be weld repaired may need to be postweld heel treated after the repairs have been made, if it is the design or service requirement _.:.., fOI-mal Repail Procedure needs to be written down, with step by step instructions d,:J

This Weld Repair Procedure ShOUld b'e approved' by the Customer I User and -the Authorized Inspector (AI), ana recorded on Data Report. For Carbon Steeis, "cosmetic ",_ or minor surface restorations after removal of tack-welds etc. are not viewed seriously. __ But conducting MT of affected area is in order. For Low Alloy steels MT after cosmetic repairs is a must.

For Carbon and Low Alloy Steels, weld repairs are pennitted provided relevant WPS I PQR I WPQR are established, and subject

tq

obtaining permission of ultimate User and

AI.

A Typical Repair procedure for CS and LAS :

1. Remove defect completely by trepanning (boat shaped groove)

2. Magnetic Particle Inspection (MT) of the area, to ensure that defect is completely removed.

(

(

3. 4. 5. 2. 7. 8. 9.

Preheat the area to 150 Deg C, and maintain the temperature during weld repair. Build up the area employing appropriate WPS and Welder, and using large (5mm dia) low hydrogen type electrodes with routine precautions such. as interpass cleaning.

Upon filling up the groove fully, weld over one more run, known as temper bead, to grain refine the undenying layers.

Maintain postheat of about 250 Deg C, for about an hour (by using asbestos blankets etc), and cool down slowly.

Dress down the temper bead, and carry out MT to ensure there are no surface defects.

Apply NOT (RT or UT as required by Design, Service or Repair Procedure). Post Weld Heat-treat as per requirement.

Notes: A Repairs to Castings and Forgings of pressure vessels would be govemed by applicable Material SpeCifications and Parts UCI & UF, of the Code's subsection 8 Repairs to stainless steel will iilvolve trepanning, dye chec~:, low heal input in welding, complete filling up with compatible electrodes/ filler wires, using optimally low currents Final NDT \'.'Quld be PT (dye checL;) and RT where applicable PWHT - ifa( all, only solution annealing, with Clien:'s concurTence

7. POSlWELD HEAT TREATMENT

f~Oi ',0,:1)' llsed materials given beIIJ'.'.',PWIIT !lccomcs 111211-::::,01\above nominal

tilIC-,S flW/l(:O!1ceJ below

When such surface weld metal build up is used in welded joints, which require full or spot radiographic examination, the weld metal build up also shall be included in the examination.

Table UCS-56 tor carbon and low ailoy steels UHA-32 for high alloy steels

UHT -56 tor territic steels with enhanced tensile properties and UNF-56 for specific non-ferrous materials

Surface Weld Metal Build Up

Deposits of weld metal are applied to the surface of base metal for the purpose: a. Restoration of base metal thickness for strength consideration; or

b. modifying the configuration of weld joints in order to provide tapered transitions as follows:

I. Butt weld procedure qualification is required as per ASME Section IXfor

the thickness of weld deposited.

". All weld metal build up must be examined over the full surface of the deposit by either MT or PT to acceptance criteria App. 6 & 8 respectively.

All welds in the Pressure Vessels or Pressure Vessel parts '-=:u're to be given a Pastweld Heat Treatment at a soaking temperature not less th2:-: :~,a~specified in under noted Tables,when the nominal thickness [as defined bei:;w] of the weldment" including carTosion allowance, exceeds the limits given in these Tabies ..

The 2bo\'e Tables specify the minir,1Umnominal thicknesses above which the postweld heat :re2tment is mandatory. These Tables also specify holding (soaking) temperatures and nOicjlllg times for different thicknesses and different tj';J8S

or

materials classified Into::' h!:.:nlbers & Group Nos by the Code

---====~-_.-.-...-....

"

D

~ ~

L>

b

~ ~ ~

D

~

D

~ l)

:»

)

DC

1)

i)

j)

l)

l)

1»

i)

)

l)

>

),

,,(,

~ )

t

~ ) ) ) )

>

) ) )

•

~ )

For carbon steels, nominal t~ickness above 31.i'5mm

For low alloy steels ot grades 1 Cr 1/2 Mo, 2 1/2 (.r.-1 Mo etc., at nomin~l_ thickness above 16mm, and for grades such as 5 Cr. 1/2 Mo and 9 Cr. 1 Mo. PWHT is required for all thicknesses.

For austenitic stainless steels [Type 304,316, etc.] PWHT is neither required nor prohibited.

For non-ferrous materials, PWHT is normally not necessary nor desirable, except for alloys like CDA-954, Zirconium grace R60705 alloy N08800, etc.

For UHT materials (territic steels with enhanced tensile properties], PWHT is required tor all thicknesses.

TABLE UCS - 56

POSTI'JELD HEAT TREA Trv,ENT REQUIREMENTS FOR CARBON AND LOW ALLOY STEERLS

I

Normal

Minimum Holding Time at Normal Temperature

I Holding

For Nominal Thickness [See UW - 40(f)]

I

Temperature, Material _{OF, Minimum}

Up to 2 in _{Over 2 in to 5 ir}

Over 5 in P - No. 1 11100 _{1 hrlin.,}

15. 2 hr plus _{15 2 hr plus 15} Gr. Nos. 1, 2,

min minimum _{mln for each}

min for each 3

additional inch _{additional inch} lover 2 in _{over 2 in} Gr. NO.4

--NA _None None _~~one NOTES: '"

(1) When it is impractical to postv.'eld heat treat at the temperature specifi~d in this Table, it IS permissible to carry out the postv,teld heat treatment at lowe,

temperature for longer periOds of time in accordance Wltll T;Jble UCS _ 5G 1

(. Post\'/eld ilcat treatmcnt IS rnanciatory under the following condltlollS .

(e') for welcjed Joints over 1 1/) IIIflOrninal tllickness

thickness is,

(

(

(b) for welded joints over 1 1/4 in nominal thickness through 1 1/2 in nominal. thickness unless preheat is applied at a minimum temperature of 2000 F during

welding.

(c) for welded joints of all thickness if required by UW _ 2, except postweld heat treatment is not mandatory under the conditions specified below:

for groove welds not over 1/2 in size and fillet welds with a throat not over 1/2 in that attach nozzle connections that have a finished inside diameter not greater than 2 in.

Nominal thickness is defined in clause No. UW-40(f) of ASME Code Section Viii Div.1. For pressure vessels or parts thereof, it is the greatest weld thickness of the equipment or part of the equipment which has not been previously post weld heat treated.

Thus, the nominal thicknesses in the following cases are:

1. In a full penetration weld joining materials of same thickness, it is a total depth of the weld, exclusive of any permitted weld reinforcement.

2. In groove welds, norn;nal thickness is the depth of the groove

3. In a groove and fillet type of weldment, nominal thickness is the depth of the groove, or the throat thickness of the fillet, whichever is greater.

4 In a fillet weld, nominal thickness is Its throat dimension. S !n stud welds, nom. thickness is the diameter of the stud.

6. When parts of unequal thicknesses are Joined together, then the nomin2!

· thinner of the adjacent parts butt welded. · the thickness of the shell in a corner joint

· th~ de~th of actual \,/cldment acros~ the nozz:e neck, includlrlg througll the r"ernforcementpa(j

" tl18thickness of tile n~nl.le fleck butt welded to a Weld Neck FIClnge

Q-..--.-~ ~ \)

\)

lW

W

~

-..)

~

=»

;)

:)

~

:)

)

'J(

,

)

r>

~ ) ) ) ) ) ~

~(

•

Operation Of PWHT

The PWHT can be r:-presented as a time and temperature cycle, recordf'd on a chart. The heating and cooling rates as well as the soaking temperature and its holding time are important, and are specified in the Tables above.

PWHT should be performed preferably by heating the equipment as a whole in an enclosed furnace. The equipment may be heated in more than one heat in a furnace, with an ovenap of atlas 5 feet of the heated sections of the vessel shall be provided. At the same time, the portion outside the furnace shall be shielded in such a manner that temperature gradients are not harmful.

Local postweld heat treatment , for example, of a heavy section, or a circumferential seam individually, may also be done in more than two or three heats, provided the heating is done uniformly and the portion outside the heated band is suitably protected from likely harmful temperature gradients. In such cases, the heated band on either side of the locally heat treated area shall be atleast twice the thickness of the shell.

For carbon and low alloy st-2-2!s,the maximum heating rate is specified as 200 Deg.C.per hour per inch ~~:·:·~-~ss.·...~i!e the maximum cooling rate allowed, after the

soaking period, is 278 Deg.C C-2~hour per inch thickness. /

The maximum loading and unloading temperatures should preferably be 300 Deg.C., to avoid thermal shock, though a temperature upto 400 Deg.C. is allowed by the Code.

The minimum holding temperature, or what is known as the soaking temperature, varies for different types of materials, designated by ~p Numbers in ASME Code. For carbon steels the minimum soaking temperature is 593 Deg C. For low alloy steels the soaking temperatures ranges from 630 to 720 Deg C, depending upon the content of Cr & Mo

The spatial variation in holding temperature during soaking period in a furnace or heating chamber, should not be more than 30 degrees betwepn the highest and lowest temperature, throughout the portion of the equipment being heated. The Code however allo\\'s a difference of upto 83 Deg C

During t~18 ~:'~atl"lg ::;nd ho:r!in~; periods the fumace atmosphere ~hOLiid bE: ~~) controlled, as to avoid excessive oxidation of the vessel ski'n surface. Neutral or reducing atmospheres are recommended. Bumer locations should be designed to prevent direct flame impingement on vessel surface.

Benefits of PWHT

1. Stress Relief: Relieving of locked up stresses in weldments, dispersal of peaks & valleys of stress levels homogeneously in a welded structure, and affording it a dimensional stability.

2. Tempering: Softening hard zones, such as at HAl and in cold formed components 3. Providing escape route 10 nascent Hvdroaen entrapped in welds, thus preclUding

possibility of underbead cracking. All of the above assure a safe and reliable welded equipment.

Summary of Postweld Heat Treatment Requirement

All carbon-and lOW-alloy steel seams must be postweld heat-treated if nominal Ihickness eXceeds 1 1/4 in or 1 1/2 in if preheated to 200' F before welding. Some materials must be postwe!d heat-treated at lower thickness.

Vessels containing lethal substances must be postweld heat-treated: Unfired steam bailers (oP more than 50 psig)

Carbon-steel vessels for service at lowered temperature must be posrNeid heat' treated unless exempted from impact test.

For welder vessels the details of PWHT temperature and hOlding time are describe in fOllOWing table of the code.

earbon- and low-alloy steel vessels

p----.

-..'-'--"-P

b

\ ~

-~ ~ .) ~ ~

i)

~

;)

) ) ) ) ~ ~ ~

•

•

•

I

High-alloy steel vessels

ueS-56,

UeS··85 UHA-32

UCS-66, UeS-67, UeS-79,

3. PRESSURE TESTING OF VESSELS:

A) HYdrostatic Test

Tesl mUsl be al leasl 1 3 limes Ihe maximum Al;oWdble working pressure multiplied by the lov;est ratio of the stress value for the test temperature to that for the design ternperature

Test pro = 1.3 x MAWPX rw' ~

t"

[\)

\i

'"

\)

\) ~ \)

\)

~ ~.

-3

~

.>

:»

3(

~

:)

:)

:)

) ) ) ) ~ ) )

"

-If the allowable sircs$ at design lerr.i)erature is less than the allowable stress at test temperature the hydros;tatic test pressure must be increased proportionally.

Allow.stress at test temp.

AlIow.stress at design temp.

Inspection must be made at a pressure not less than Test pr.divided by 1.3. Corrosion allowance may be considered in calculating test pressure. The maximum allowable working pressure may be assumed to be the same as the design pressure when calculations are not made to determine the maximum allowable working pressure.

Max.lnspection temp. = 120 dec F,. Min. Test temp.= MDMT+30 deg.F

,.

Test gauge range limit = 1.5X Test Pr: (Minimum)

= 4X Test Pro ( Maximum)

B) Pneumatic Tests

Pneumatic test may be used instead of hydrostatic test when:

Vessels are so designed dndsupported thai they cannot safely by filled with water.and Vessels for service in which traces of testing liquid cannot be tolerated Prior to Pneumatic test, Testing of attachment wells asper WU-50 must be performed

Test pressure must not be less Ihan 1.1 limes maxImum allowable working pressure multiple by the ratio of stress value Sfor test temperature oi vessel to the stress value Sfor design temperature. Min. Test temp.= MDMT +30 deg.F

-The pressure in the vessel shall be gradually increased to not more than one-half of the test pressure. Thereafter, the test pressure shall be increased in steps of approximately one-tenth of the test pressure until the required test pressure has been reached Then the pi€Ssure shall be reduced to avalue equ21 t09/1 0 of the test pressure and held for a sufficient time to permit inspection of the vessel. Leakage is not allowed at the time 0;the required visual inspectioil.

Test gaug9 range limil = 1 5X Test Pr. (MillimUill) = 4X Test Pr

( Maximum)

,r ),)

L

I

•

L)

D

•

b

~ ~ ~ ~ ~ ~

>

~ ~

»

»(

t

•

(

6.

INSPECTION

&

TESlH~G

From Inspector's Viewpoint, following are the major areas of concern during manufacture of pr. Vessels.

A. MATERIAL INSPECTION:

1. Materials for Pressure .parts and Non.pressure .parts ... ( UG-4 a,b )

2. Scrutiny of Mill-Certificates-compliance with specification, Identification marks, co-relate material with certificate ( UG-93 a)

3. Additional requirements: Impact test results, PWHT etc ... ( UG-84,85 ) 4. Mill Under-tolerance for plates ( UG-16. c)

5. Tolerances on bought-out heads (UG-81. a,d)

B. FABRICATION INSPECTION:

1. Tracability of plate mari<ings/transfer of mari<ing ( UG-n.::: ) 2. Shell forming, out of roundness '" __ ( UG-8G2 ,2\

3. Taper transition, Skirt length of Heads ( UW-9 c: fig.UW-13.1 d,I,m,n,o ) 4. Scrutiny ofWPS/PQR documents __ ( UW-26 J,b; UW-28d)

5. \fVelder Qualifications/Re-qualification of contract welders, caliing and witness the tests ( UW-26c; UW-29 c,d,e; UW- 48 b)

6. Conditions not suitable for welding ( UG-30) 7. Alignment tolerances ( UW-33)

8. Weld reinforcement. ( WU-35)

9. \'\'eld - penetration, welder identification ( UG-37 a.f) 10 ?\,\'~T requirements ( UW --40 a2, UCS-56)

11 1'!DTofPr.Vessels (UW-2a,c; UW-11a-1 t05);UW-11b;UW-57, UG-93d3; UW-50, UW 51, UW-52 App.4,6,8,12) 12 Pressure testing ... ( UG-99, UG-100, UG-102 , UW50 for Pneumatic test) 13 ':':-OJ'2 Stamping.( UG-11 G, UG-118 )

1.

NDE OF PRESSUR~ VESSELS

A. SELECTION OF NOT TECHNIQUE W.R. T. WELDING DISCONTINUITY

Note 1 : a. Surface

b. Surface and slightly subsurface

c. Weld preparation or edge of base metal

. -J

Applicable method .

Marginal applicability depending on othertactors such as material thic"ness, Discontinuity size, orientation and location

~2:

Le2c; testing can reveal only through and through leaks.

Applicable NOT methods I Welding Discontinuities

Applicable _{NOT Methods} Discontinuities RT _UT PT _MT

_vr

ET Porosity

-J

• ..J"

.b

_-Ja

•

Slag Inclusion

_-J

-J

_NA .0 NA • Incomplete fusion

.

\'

NA .0 NA • Incomplete Penetration

_-J

-J

_NA

.

NA

•

Undercut

-J

.

.

•

-J

• Overiap NA

.

-J

_-J

_•

·

Cracks _•

\'

..J" _~

-Ja

_-J

Laminations NA

_\'

_-J3.C

-Jb.c

_-Ja.c

NA Note 1 'J-~APPlicable method

Marginal applicability depending all other factors such as malerial thickness,

DisContinuity size, orientation and location

Applica~le NOT methods for Weld joint types

Joints

NOT-Methods

RT _UT

PT

_MT

VI

_ET

Butt.

-J

\1

_-J

\'

-J

_-J

-

Corner

.

\'

_-J

\1

_I

\'

·

-

T

I

--

--l

.

\1 _-J

Y

·

-~ \ ---;;~

-J-

-Lap

.

\i

_I

\'

·

I.cc~i-; testrflg C21l reveal Oflly tilrougil anl~ UiiOUgh leJks

',-'

,

B. CODE REQUIREMENTS OF NDE-jASf\..1E: Sec. VIii Div.1)

1 RADIOGRAPHY REQUIREMENT: a) Full Radiography

Conditions for which full radiography is specified are the following:

1) All but welds in the shell and heads of vessels used to contain lethal substances must be fully radiographed.

2) If the plate or vessel wall thickness at the weld joint exceeds the thickness given in table UCS-57, UNF - 57, and UHA - 33, then full radiography is required. (e.g. P. No.1, gr 1,2, 3 require full radiography - UCS 57)

3) Butt welds unfired steam boilers with a design pressure exceeding 50 psi. 4) All butt welds in nozzles for vessels 1)& 3) above. In others, category Band

C welds upto NPS 10 and upto 1 1/8 in. thk. do not required radiography. 5) All category A and B welds shall be Type no.(1) or Type no.(2) and shall be

radiographed accordingly.(UW - 12)

6) Category Band C welds (excluding those in nozzles in 4 above) which intersect the Category A welds shall be at least spot radiographed.

7) Weld metal build up ( 1 : 3 taper) to be radiographed same as joint itself.

b) Spot Radiography

1) Butt welded joints Type (1) or (2) of Table UW - 12 if design efficiency is selected for spot radiography.

2) If spot radiography is specified fOL entire vessel then radiographic examination is not required of category Band C butt welds in nozzles less than NPS 10 or 1 1/8 in. thick.

C) No Radiography

No radiography is required if vessel is designed for external pressure or dosign efficiency (Table UW - 12) is selected for no raciography.

(

(

_ UL

;RASONV~: ExAMINATION:

lJarasonic examination may be substituted""' for radiography for the final closure seam of a pressure vessel. (UW-11 a7)

3. MAGNETIC PARTICLE EXAMINATIONS:

1. When a pressure part is to be welded to a flat plate thicker than 1/2 in (13 mm) to form a comer joint (fig. UW 13.2). Then MP examination is required on weld joint preparation prior to welding and also after welding. (few exceptions described in UG - 93).

2. If vessel is to be Pneumatically Pressure tested. All welds around openings and all attachment welds with throat dimension exceeding 6mm ( 0.25 inch)

4, LIQUID PENETRANT EXAMINATIONS:

In case of non-magnetic materials LPE can be substituted for MPE for above examinations.

C. NOT ACCEPTANCE CRITERIA:

iliaanetic Particle Examination

r

MT

1 -

Mandatory Appendix 6

.-Magnetic Particle Examination shall be performed in accordance with the written procedure certified by the Manufacturer to be in accordance with the requirements of T-150 of ASME Section-V.

1.1 NDE Personnel:

a. Shall have a vision, with correction if necessary, to enable reading a Jaeger Type NO.2 Standard Chart at a distance of not less than 12 inches; and shall be capable of distinguishing and differentiating contrast between colours used. This requirement shall be checked annually. b Shall be competent and duly certified in MT techniques

1 2 .l;valuation of Indications:

Indications will be revealed by retention of magnetic particles in the orientation of the possible defects All such indications are not necessarily imperfections 11O·,'IO\ler.Since excessive surface rougtincss, magnetic permeability variations

(

(

- l suctl as at the edg~ of na.;l! ~ije(;t :wnec-.\ (;iC. :'la~'also ri·I.~du(;(.;sia:ilar

indications.

An indication is the evidence of a mechanical imperfection. Indications which have dimensions greater than 1/16th of an inch are considered "relevant".

a) A linear indication is one having a length greater than three times the width.

b) A rounded indication is one of circular or elliptical shape with a length equal to, or less than three times its width.

c) Any questionable or doubtful indications shall be re-examined to determine whether or not they are relevant.

1.3 Acceptance Standards

These acceptance standards shall apply unless other more restrictive standards are specified for specific materials or applications within this Division.

All surfaces shall be free of :

a) relevant linear indications;

b) relevant rounded indications greater than 3/16 inch;

c) four or more relevant rounded indications in a line separated by 1/16 inch or less, edge to edge.

d) An indication of an imperfection may be larger than the imperfection that causes it; however, the size of the indication

IS

the basis for acceptance evaluation.

2. Liquid Penetrant Examination

r

PT

1-

Mandatory Appendix 8

Liquid Penetrant Examination shall be performed in accordance with the written procedure certified by the Manufacturer to be in accordance with the requirements of T-150 of ASME Section-V.

2 1 @E Personnel:

-Cl. Shall have a VISion, with correction if necessary, to enable reading a

Jaeger Type NO.2 Standard Chart at a distance of not less than 12 IIlChes; and shall be capable of distinguis[ling and differentiating contrast betwee;~ colours Used. This requirement shall be checked annually.

i) SI1311 be competent and duly certified in PT techniques 2 2 l~.\l9~13tloll_QLLndic_~o_~ :