1

GUIDE TO PRESSURE VESSEL CODES

BHARAT HEAVY ELECTRICALS LIMITED CORPORATE QIALITY ASSURANCE

2

BHARAT HEAVY ELECTRICALS LIMITED

CORPORATE QIALITY ASSURANCE

INTRODUCTION

There is an increasing use of national and international codes on unfired pressure vessels in BHEL‟s Plants as well as in the works of BHEL‟s Vendors. While interpretation of the Codes is possible by going through the actual codes, it is felt necessary that salient features of some of the regularly used national and international codes will be useful in concise form and in the form of a comparative statement.

Some work in this regard was already done by Bhopal and Hyderabad Plants. This Publication is an attempt to assist the Specialists, Executives and Supervisors at Shop Floor level as a reference document. The efforts put in by the Quality Services Group of Bhopal and Ramachandrapuram in compiling this useful booklet is acknowledged.

Secunderabad (P.S.THILAK) May 5, 1984. Dy. General Manger Corporate Quality Assurance

3

B.S.5500 : 1976 ASME SEC VIII : 1980 (Div .1)

A. SCOPE OF THE COSES

Covers design, constructions, inspection, testing and certification of unfired fusion welded pressure vessels.

Covers minimum construction requirements for design, fabrication inspection and certification of unfired pressure vessels.

Sections include: Sections Included:

1. General (Definitions and responsibility of purchaser, manufacturer, inspectors etc.)

Subsection A (Covering general requirements applicable to all types of vessels)

2. DESIGN SUB-SECTION B (Covering requirements separately for welded riveted forged or brazed methods)

3. MANUFACTURE & WORKMANSHIP

SUB-SECTION C (Covering requirements applicable to different classes or materials i.e., cast iron, clad and lined material and nodular iron etc.,)

4. INSPECTION & TESTING MANDATORY APPENDICES (including design formulas, porosity charts, methods, for Magnetic particle inspection, Q.C. systems etc.,)

5. APPENDICES (all non-mandatory)

NON-MANDATORY APPENDICES (Some suggested good practices e.g. in ultrasonic examinations for bolted flange connection).

This standard does not cover the following:

This standard does not cover the following:

1. Storage tanks designed for the storage of liquids near atmospheric pressure (i.e. 140m-bar above and 6m-bar below atmospheric pressure). Low pressure storage tanks with one vertical axis of revolution with pressure less than I bar.

i) Vessels with design pressures exceeding 3000 Psi (20, 670K Pa).

ii) Vessels with I. Dia width, height or cross section diagonal less than 152 mm.

iii) Vessels for internal/external pressure operation not exceeding 15 Psi (103 K Pa)

2. Vessels where stresses calculated are 10% of the design stress permitted by section 3.

iv) Vessels subjected to federal control

3. Scrip wound compound or other special designs of vessels for very high pressures.

4

B.S. 5500 : 1976 ASME SEC VIII : 1980 (Div.1)

4. Transportable vessels

5. Vessels for specific applications which are covered by BSI year book

5. Unfired steam boilers excluding evaporators heat exchangers and vessels in chemical. Petroleum industries where steam is generated incidental to operation of a processing system containing a number of pressure vessels.

. 6. Vessels used for hot water supply storage tank heated by steam within the following limitations:

a. Heat input of 20,000 Bt.U/hr. (58.6 Kw).

b. Water temp. of 210 o F (99o C).

c. Nominal Water capacity of 120 gallons (454 liters)

7. Pressure containers which are integral parts of rotating or reciprocating mechanical devices e.g. pumps, turbine generators, hydraulic or pneumatic cylinders where primary design consideration and / or stresses are derived from functional requirements of the device.

8. Vessels with a nominal water containing capacity of 120 gal (454 liters) or less containing water under pressure including those containing air the compression of which service only as a cushion.

9.Piping components such as pipes & valves,

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IS 2525 : 1969 I.B.R

Covers minimum construction requirements for design, fabrication, inspector, testing, and certification of fusion welded unfired pressure vessels, in ferrous and non-ferrous materials.

Covers design, construction, testing and certification of boilers mainly. However chapter XV Heat exchangers etc., and similar vessels recommended that heat exchangers and similar vessels be constructed following the applicable regulations, covered under different chapters.

Usually Chapter XII shell type boilers of welded construction is being followed. Also regulation – 523A stipulates that feed water heaters may be constructed as per chapter XII.

Hence reference is mostly made to chapter XII shell type boilers of welded constructions is being followed.

Also regulation- 523 A stipulates that feed water heaters may be constructed as per chapter XII.

Hence reference as per chapter XII ONLY. For workmanship various chapters covered are:

1) General, material & design.

2) Fabrication and welding

3) Inspection test, marking and records.

4) Appendices (both mandatory and non-mandatory)

Chapter I General requirement

II Material for construction

XII Shell type boilers of welded construction.

Equipments governed by I.B.R. are as noted below:

1) All boilers.

2) Steam pipes with pressure 3.5 Kg/ SQ. Cm. Or with dia exceeding 254 mm in I.D and with out limitations of pressure.

3) Equipments like feed water heaters etc connected after boilers etc connected after boiler feed pump in which steam is the medium.

This standard does not included the following:

1.Vessels which design pressure exceeding 210 KG/Cm2

2.Vessels with O.D/I.D > 1.5

3.Vessels operating under internal pressure below 1 Kg/Cm2

4.Vessels with I.D. > 150 mm

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IS 2525: 1969 I.B.R

5. Equipments under I.B.R. per view

6. Vessels where internal pressure is only due to static head of liquid

7. Vessels with a nominal capacity of 500 liters or less for containing water under pressure including those containing air, the compression of which services only as a cusion.

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B.S. 5500: 1976 ASME SEC VIII: 1980

(Div.1)

B. CLASSIFICATION OF VESSELS

Vessels are classified into three construction categories, on the bases of material, NDT temperatures etc., These are as follows:

Welded joints are categorized into A, B, C, D according to their location and special requirements are specified at different places in the code. No classification of vessels in line with the other codes.

Construction category.

1 2 3

It may be recalled that the entire code has been classified as per the materials, methods of manufacture of the vessels, quality control etc.,

N D T permitted material

100% all

Spot

M0 & M1,M2 M 3, M4

Austenitic steels.

Visual only M0, Austenitic steels

A. Category A Long welded joints in main shell, nozzles et. Any welded joint within a sphere, with in a formed or flat head, side plates of flat sided vessel, circumferential welded joints connecting hemispherical heads to main sheets, to transition in diameters, to nozzles etc.

Max, thickness (mm)

None except

M0, M1-40

M2-30

M3-20

M4-15

Austenitic none

M0-25

Austenitic steels none.

Category B Circumferential welded joints within the main shell, nozzles or transitions in diameter, circumferential joints in connecting formed heads other than hemispherical to main shells, nozzles etc.

Upper Temperature limits

Values to be based on design life time etc., as per table 2.3

Same as category

350o C Category C Joints connecting flanges, tube sheets or flat heads to main shell, to formed heads, to transitions in diameter, to nozzle etc., to transition in diameter, to nozzle etc.

Lower temperature limit

Note For M0 For M0 Category D joints connecting communicating chambers of nozzles to main sheels, to heads, to transitions in diameters

Note M1, M2, M1, M2,

M3, M4 M3, M4

Less than 10oC above

Less than 20oC above

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IS 28 25 : 1969 I.B.R

B. CLASSIFICATION OF VESSELS

Classification: Class I limits of Application: No limits Minimum thickness: ¼ inch

Classification: Class II

Limits of Application: When the following limits are not exceeded:

a. Working pressure – 105 psi

b. Working pressure in psi multiplied by ID in inches - 5250

Minimum thickness: Boilers upto 36 inches I D – 5/16 inch.

Classification: Class III

Limits of Application: when the following limits are not exceeded:

Vessels are classified in three groups on the bases of use, thickness. Joint design and efficiency materials of construction and Quality Control requirements.

a. Working pressure – 30 psi

b. Working pressure multiplied by I D in inches – 3000.

Joints have been categorized as in ASME Sec. VIII in to A, B, C, D.

Minimum thickness: Boiler 36 inches I d – 3/8 inch

Class 1 vessels are those intended for lethal substances or for operation below 20o C or when mutually agreed upon by purchaser & manufacturer. Category A & B joints in such vessels to meet requirements of Table 1.1, class 2.

Class 2 Vessels are medium, = duty vessels and shall meet the requirements of table 1.1, class2.

Class 3 Vessels are light duty vessels here plates are less than 16 mm thick & working pressure less than 3.5 Kgf/Cm2 hydrostatic design pressure at temperature less than 250o C and unfired.

Class 3 Vessels: are not recommended below 0oC.

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B.S. 5500: 1976 ASME SEC VIII: 1980 (Div. 1)

1 2 3

Minimum specified in a Appendix D None austenitic steels

Minimum specified, None austenitic steels.

Other classifications are made on the bass of joints efficiency & extent of radiography. A short summary of the classification is as follows:

A. Efficiencies: Double welded butt joints 0.7, 0.85, 1.00 (depending) on no radiography, spot or full joint with back strip (0.65, 0.8, 0.9) and without back strip 0.6 double full fillet lap joint 0.55.

B. Radiography: A list of joints where full radiography (e.g. all butt welds in vessels containing lethal substances), spot radiography (e.g. double welded butt joints not required to be fully radio graphed) and no radiography is required is given.

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I.S. 2825 : 1969 I.B.R.

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B.S. 5500: 1926 ASME SEC. VIII DIV. 1: 1980

C. MATERIAL REQUIREMENTS

Materials should take into account the fabrication and operating conditions. Special consideration should be given for use below 0

o C. Any special limits

e.g. w.r.t. Composition, heat treatment should be agreed upon at the time of enquiry or order.

Materials subjected to stress due to pressure shall conform to one of the specifications given in ASME Sec. II and shall be limited to those that are permitted in the applicable part of subsection c- expect as permitted UG-10 (procedure for material not fully identified) and UG-II (misc preformed or prefabricated pressure parts like pipe fittings, valve flanges etc.,)

All material normally to conform to BS unless otherwise mentioned Welding material shall conform to the requirements of section 4 & 5.

Material not conforming to the above will require special approval of boiler and pressure vessel committee.

For casting, a quality specification is to be draw for acceptance standards between manufacturer and material supplier. As a minimum, fillets and changes of section to be Dye penetration or magnetic crack detection tested.

Carbon or low alloy steels having a carbon content or more than 0.35% by ladle analysis shall not be used in welded construction or oxygen cut List of approval specs, given in UGS-23 along with stress values at various temperatures. For service temperatures above 850

o F (454

o C) it is

recommended that killed residual silicon be used. The stress values in table are to be multiplied by a “ casting quality factors” given in UG-24.

Bolts and nuts to conform to BS 4882. Lugs, baffles and non-pressure parts to be of established.

High alloy steels are listed in Table UHA-23 and appendix HA given suggestions on the selection and treatment of austenitic chromium Nickel steels. High alloys steel casting are mentioned in Table –23. The stress values are to be multiplied by casting quality factor of UG-24.

Materials used should be covered under Table 2.3 (specs for C, c. – Mn Low alloy, high alloys steels. In case some other material is used it should comply with the general requirements mentioned and should be covered by a written specification, at least as comprehensive as the nearest equivalent materials).

In recognition of controversial opinion relative to the effects of post-weld heat treatment on austenitic stainless steels, mandatory requirement have been omitted. However, for maximum corrosion resistance, a suggested heat treatment 1850-20 50

o F (1010-1121

o C) and

Nominal design strengths and methods of calculations are given in Table 2.3 & Appendix K. Details to be agreed upon by manufacturer and purchaser and recorded. Non-destructive testing requirements for plates, forgings, pipes and castings are given in Art 5.6.2.

General requirements for materials not covered under Table 2.3.

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IS 2525 : 1969 I.B.R

For class 1 & 2 vessels this standard prohibits for pressure parts the use of structural steels standard, high tensile, fusion welding or ship building verity (IS 226, 961, 2062 & 339). The materials used for the above classes should conform to table given in Appendix A.

R-537- Platters elt used in the construction of these Boilers shall comply in all respects with the requirements of chapter II and V, where, however, the tensile strength exceeds 32 Tons per SQ. in, the full details of welding and post heading, and the plate preparing to be used, shall be submitted to the inspecting Authority for approval before manufacture commences.

Class 3 vessels may use the above mentioned “ prohibited” materials and also IS 2041 (steel plates for pressure vessels), IS 1570 (wrought steels general engineering purposes), IS 2002 (Steel plates for boilers).

Electrodes (R: 538) – They shall comply with the regulations of 94 to 98.

Nothing in the foregoing precluded the use of otherwise suitable material agreed upon. Special care to be taken for weld ability and ductility. No such material shall have an elongating (on 5.65 50) of less than 100-Rm where Rm is the tensile 2.2

strength in kgf/mm2 subjected to a minimum of 16% fore carbon manganese steels. 14 % for alloy steels other than austenitic and 25% for austenitic steels. Material for lugs, baffles, etc. to be weldable quality All materials shall be supplied in accordance with IS 1387 –1967, and threaded fasteners in accordance with IS 1369-1967.

Tubes: They shall comply with the regulations of 36 to 63. The tubes shall be seamless and made by an open hearth or Electric Process, acid or basis, and shall be certified as such by the makers of the steel by the tubes. The material of the tubes shall shoe on analysis not more than 0.05 percent of sulphur and 0.05 percent phosphorus and the manufacturer shall supply a certificate of the analysis when required to do so.

Stress safety factors to calculate allowable values are given in Table 2.1 (varying from 1 to 3) and values calculated on these criteria given in Appendix A. Shear and bearing stress to be 50% of Appendix A values. Compressive stresses to be calculated as per appendix C, . For castings, the factor of Table 2.1 shall be divided by 0.75, except when the casting has been radio graphed, dye or magnaflux tested.

Note: Where the materials used for designed temperature for design temperature above 750o F (399 O C) the steel shall be of non-segregated or fully killed type.

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B.S. 5500: 1976 ASME SEC VIII DIV. 1: 1980

Material spec. Should at least specify making process. Compositional limits deoxidation practice. Heat treatment and appropriate mechanical properties.

“ One hour per inch” of soaking time and rapid cooling from 700 o F to 1000 o F (371 – 538 o C ) has been given.

For forritic steels for welding C > 0.25%. For C> 0.25 % special agreement between manufacturer and purchaser. Phosphorus & sulphur < 0.05%.

Deoxidation practice should be appropriated to the type of steel ordered, particularly when high or low temp. Properties are affected. Following are permissible.

Semiskilled steel-plates, seamless & welded tubes in C.C. Mn steels for U.T.S. < 640 N/mm2 and thickness < 100 mm

Rimming steel- only for welded tubes in C, C-Mn, steels with U.T.S. < 490 N/mm2 temperature 0-1380 o C. 2

Mechanical properties (BS 18) UTS, Lower stress or 0.2 % proof stress (1% for austenitic), minimum elongation at fracture (L= 5.65 so, Charpy V-Notch (B.S. 131 Pt.2).

Permitted % elongation is 16% for plates, > 15% for casting > 14% for tubes and forgings.

For materials used over 20o C , a certifiable lower Y.P. or proof, stress (ref. BS 3688) to be specified.

Stress reputed properties for materials in creep range.

Plates fro hot forming to be supplied condition as agreed between suppliers & manufacturer

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I.S. 2525 : 1969 I.B.R

15

B.S. 550 : 1976 ASME SEC VIII DIV .1 : 1980

B. C, C-Mn plates for cold forming to be normalized for thickness > 25 mm unless post weld heat treatment is sufficient

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I.S. 2525 : 1969 I.B.R

17

B.S 5500: 1976 ASME SEC VIII (DIV.1) 1980

D. MANUFACTURE AND WORKMANSHIP

GENERAL GENERAL

1. Fully dimensional drawings giving material specn, welding procedures, NDT and test plate requirements, pressures corrosion allowance etc., to be submitted by the manufacturer.

1. Manufacturer must have ASME Certificate of Authorization and must have in force a valid inspection contracts. Inspector must be qualified by state. Manufacturer must supply drawings and a host of other documents listed in UG 90 (e.g. design calculations written QC System etc). to the inspector.

2. A position identification system for pressure parts is necessary so that they can be traced back to their origin.

2. Material must in general conform to action II of ASME Boiler and pressure vessel code unidentified material may be used for non-pressure parts e.g. skirts, baffles, and lugs. For all such parts 3/8” thick double-welded butt joint shall be made from each lot and guide bend tested.

3. For vessels made in two or more courses longitudinal seams to be completed before starting adjoining circumferential seams and longitudinal seams to be staggered wherever possible.

Partially identified, material may be used as per a procedure given. A table or sketch showing location on vessel of items and their identifications. Marking to be steel die stamped as specified in ASME sec. II.

Where more than two seams meet at a point, intermediate stress relief is desirable.

3. Except when radio graphed 4” (120 mm) on each welded intersection, vessels made up of two or more courses, shall have centers of longitudinal joints staggered on separated by a distance of five (5) times the thickers plate.

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I S 2525 : 1969 I.B.R

GENERAL GENERAL

1. Manufacturer shall normally submit drawings material specn. Welding processes weld designs design parameters, amount and location of allowances etc., to purchaser

1. Manufacturer shall be submit the detailed drawings including weld details, calculations and materials to the inspecting Authority for approval prior to the construction.

2. Procedure for identification and its transfer on cut items for pressure parts is given.

2. MATERIALS (Procedure for identification):

All plates, rivets and bars used in the construction of boilers shall be tested and found to conform with the regulations to conform with the regulations. A certificate in form II, III, III-A and IV.

3. Concentration of joints should be avoided such that no two main seams come together under an acre angle or cross each other. Where unavoidable, the intersections should be radio graphed 100 mm on each side of inter section be staggered by five (5) times the thickness of thicker plate.

Welding of attachments near main seams to be avoided. If unavoidable welds should cross rather than stop abruptly near seams.

3. Shall Courses assly etc (R 543)

The longitudinal seam or seams may be placed in any suitable position but the seams in successive rings shall not fall in line.

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B S 5500: 1976 ASME SECI VIII: 1980 (Div.1)

CUTTING FORMING & TOLERANCE

1. Cold shearing may be used for plates < 25 mm but edges to be ground at least 1.5 mm. Grinding not required for sheared plates < 10mm.

1. All cutting methods may be used in general Exposed inside edges to be rounded off to a radius at least 1/8 “(4mm) flat.

Thermal cutting on machining are preferable. For materials requiring preheat during welding, thermal cutting should be done with preheat.

For plates over ½ “ (12.5 mm) thick used for corner joints (joints at approx, 90o), edges to be tested by D.P. or M.C.D

Thermal cut ferritic alloy steel shall be dresses by grinding or machining.

All materials to be impact tested shall be inspected for surface cracks.

Visual examination for laminations, crackers, slag inclusions may be supplemented by N.D.T.

Adjoining edges of longitudinal joints to be preliminary formed to avoid flat spots after rolling.

2. Prior to forming, visual examination of plates, followed by thickness measurement, to be done.

3. Austenitic steels for hot working shall be heated uniformly in neutral or oxidizing temp. Deformation below 900o C and local heating is prohibited. After hot working, softening to be carried out by heating, at a recommended temp, hot less tan 30 minutes. Descalling to done.

3. For P.W.H.T (post weld heat treatment) of austenitic stainless steels mandatory requirements have been omitted. However for maximum corrosion resistances, a suggested heat treatment (1850o – 2000o F) (1010O-1104o C) and one hour per inch of thickness as soaking time with rapid cooling from time (1000o F) has been given.

Austenitic steels after cold working shall be subsequently softened & descabed unless thickness is less than 10 mm or the purchaser waives this requirements.

4. All plates after being formed shall be check visually and checked for thickness. Places where attachments are to come may be non-destructive tested if specially called for in design.

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IS 2825: 1969 I.B.R

1. Where thickness < 25 mm, cold shearing may be used provided edges are chipped or machined one quarter of plate thickness or minimum. 3 mm.

1. Chapter XII. Regulation 541 plates which are to flame- cut by machine without subsequent heat-treatment, grinding or machining, shall not have or machining, shall not have a carbon content higher than 0.26 percent. Where the carbon content exceeds 0.26 percent. Heart-treatment grinding or machining shall be carried out.

Caron steels may be mained, chipped ground or flame cut but alloy steels and non-ferrous materials shall not be flame cut unless agreed upon.

Preheating may be required and visual examination for flaws laminations, inclusions shall be made special inspection may be required for cracks on cut surfaces and HAZ in high carbon and alloy steels

Hand flame cut edges shall be chipped or machined 3 mm minimum or one quarter plate thickness

2. Seams may be welded prior to forming but must be radio graphed fully after wards. In carbon steels < 25 mm and alloy steels DP or MCD to be done.

2. Examination of Tubes before forming: (R 338):

a. Where tubes are bent, the deviation from circularity at any cross section shall not exceed

20D/R.

where,

D nominal out side diameter and R: radius of bend on the center line of the bend.

b. Where the tubes are bent resulting thickness of the tubes at the thinnest part shall not be less than that required for plain tubes. Tolerance on thickness shall be – 5, + 10% of the specified thickness.

c. All pipes shall be commercially straight, free from longitudinal seaming, grooving blistering or other injurious surface marks – (R 35).

3. Ref I S D – R-831

4. Ref I S D – R-831

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BS 5500: 1976 ASME SEC VIII: 1980 (Div.1)

5. TOLERANCES

I) Assembly Tolerance:

a. Longitudinal joints and spherical joints for plate thickness “e”.

I) Alignment tolerance

Thickness Longitu-

dinal

Circumfe-

rential

e Middle line alignment

Upto ½ in (12.5 mm)

¼ t ¼ t

<10 mm

>10 and 50 mm

1 mm

10% of “e” or 3 mm (whichever smaller)

Over ½ into ¾ mm (125-19 mm)

1/8 in (3 mm)

¼ t

>50 and 220 mm

e/16 or 10 mm (whichever smaller )

Over ¾ to 1 ½ in (19-38 mm)

1/8 in (3 mm)

3/16 in (5 mm)

> 200 mm As agreed upon Over 1 ½ to 2 in (38-50 mm)

1/8 in (3 mm)

1/8 t

Over 2 in (50 mm)

Lesser of 1/16 t or 3/8 in (9.5 mm)

Lesser of 1/8 t or ¾ in (19 mm)

b) Circumferential joints:

e Middle line alignment

The above are the alignment at the edges to be but welded. Surface alignments are not given

10 mm 1 mm Any off set within the allowable range shall be faired at a 3.1 taper over the width of the finished weld. Build up may be done.

> 10 and

60 mm

10% of „e‟ of the thinner plate + 1mm or 6 mm (whichever smaller).

>60 and 200 mm 10% of „e‟ or the thinner part.

> 200 mm As agree upon.

Permissible surface alignments are as shown below: If these are exceeded a taper of 1:4 to be given which should include the weld. The lower surface may be build up to given the 1:4 taper.

a. Longitudinal joints

e 12 mm

13 < 0 50 mm

e> 50 mm

E/4 mm

3mm

Lesser of e/16 or 10mm.

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I.S. 2525 : 1969 I.B.R.

I) Alignment tolerance 5. TOLERANCES:

Defects in alignment at surface shall be less than the followings:

(R-250) and (5-544)

For plated less than 5 mm thick t/6 for long seams and t/4 for circumferential seams, subject to a maximum of 1 mm.

5.1.a) Before welding of the joint is commenced it shall be ascertained that the edges are in alignment and the defects in alignment shall not exceed the following limits:

For plates more than 3 mm thick 10% of nominal thickness wit a maximum of 3 mm for long. Joints. But for plates upto 10 m / for circumferential joints, the values are 10% of max. nominal plate thickness plus 1 mm subject to a maximum of 4 mm.

1. 10 % of the nominal plate thickness with a maximum of 3 mm for long seams.

2. 10% of nominal plate thickness plus 1 mm with a maximum of 4 mm for C/ seam joints.

(Welds with backing strip require better alignment).

b) If the edges of unequal plate thickness are abutted and the difference between the two exceeds the above limits 1 in 4 tapper shall be provided on the thicker plate.

The increase or decrease in root gap at any point in seam after tacking shall not exceed 1 mm.

L a misalignment of 1 mm permitted.

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B.S. 5500: 1976 ASME SEC VIII: 1980 (Div. 1)

b) Circumferential joints

e 20 mm e/4 mm

20 < e 40 mm 5 mm

E > 40 mm Lesser of e/8

or 20 mm

ii) All pads, reinforcing plates man-hole frames lugs, brackets, supports or other attachments. Shall have a gap at exposed edges to be welded < 2 mm or 1/20th of the thickness of attachment, whichever is greater.

ii) All lugs, brackets, saddle type nozzle, manhole frames etc, shall conform reasonably to surface to which they are attached.

Except where shown otherwise on drawing maximum gap between outside of branch & in side of edge of hole in shell, flange reinforcing ring or backing ring shall be < 1.5 mm for opening up to 300mm and 3mm for openings above 300mm. To achieve this the branch may be machined, but the machined surface should not extend beyond the toe of weld and shall not reduce the thickness of branch below design thickness plus corrosion allowance.

iii) Tolerance for ends

a) Circumference as calculated from Nominal I.D + Actual thickness and the actual circumference should agree as follows:

a) Circumference not mentioned anywhere.

O.D. Circumference (nominal Tolerance Dia + actual

thickness)

550 mm 5 mm

> 650 mm 0.25%

of circumference.

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I.S. 2525: 1969 I.B.R

ii) All lugs, brackets, saddle type nozzles, manhole frames etc. shall conform reasonably to the curvature of the shell or surface to which they are attached.

5.2 (R-544)

a) The difference between the internal diameter of the drum measured at any cross section shall not exceed 1 % nominal I.D. The departure shall not exceed:

i) Upto and including 36” I.D. 0.375%

ii) Over 36” upto and including 45” I.D. – 0.35%

iii) Over 45” I.D.

a) Circumference same as for shells.

5.3 there shall be no flats at the welded seams and any local departure from circularity shall be graded.

25

B.S 5500: 1976 ASME SEC. VIII: 1980 (Div.1)

b) Circularity shall be same as that for shall.

b) Circularity (out of roundness shall be the same as that for shell i.e. 1% of nominal I.D.)

c) Thickness is that after the manufacture of and shall be uniform over the whole area knuckle. From this point, a gradual thinning of upto 10% is permissible.

c)

*Nor inside of 5/8% of I.D.

d) Profile: the depth of dishing „d‟ should never be less than theoretical or more than that given below:

Knuckle radius shall not be less than theoretical and shall have common tangents with straight flange and dishes profile.

d) The inner surface of head shall not deviate out side of – the specified shape by more than 1 ¼% of I.D. *charge shall be gradual and decimations shall be measured perpendicular to the specified shape.

Dia of end permissible

increase in the

depth of dishing

< 3000 mm 1.25% of dia

3000-7600mm 3.8 mm

< 7600 mm 0.5% of dia

When the skirt of an un-stayed head is machined to make a close fit in to or over a shell, the thickness shall not be reduced to less than 90%. The transition shall be tapered to at least 3 times the thickness difference.

iv) Tolerance for shells

a) Circumference: as for e ends.

a) No mention of circumference.

b) Straightness: Max deviation from straight line 0.3% either of total

26

I.S 2525: 1969 I.B.R

b) Circularity same as that for shall.

c)

d) The inner surface shall not deviate from the specified shape by more than 1.25% of the I.D. of head skirt, such deviations shall not be abrupt, shall be outside of the theoretical shape and measured perpendicular to the specified shape.

When the skirt of an unstayed head is machined to make a close fir into or over shell the thickness shall not be reduced to less than 90% of original. Transition shall be trapped to at least 4 times difference.

a) The external circumference based on nominal I.D. and actual thickness should be within the foll. tolerances:

O.D. Tolerance

300-600 mm 5 mm

over 600 mm 0.25%

Notwithstanding these, the governing factor shall be the misalignment tolerances.

Max. deviation from straightness is to be 0.3% of total length or 5 meters length, for shells over 2 meters long.

27

B.S. 5500: 1976 ASME SEC. VIII. 1980 (Div. 1)

cylindrical length or any individual 5 meters.

c) Circularity - Max and Min. dia difference at any cross section shall be less than specified below.

c) out or roundness (circularity) to be less than 1% of the nominal dia of cross sec

When the cross section passes through an opening, the permissible difference in I.D. given above may be increased by 2% of the opening.

For vessels under external pressure out of roundness shall be as above, but the plus or minus deviation from the true circular form measured radially inside or out side shall be within values of „e‟ obtained from graph UG-80.1.

A segmental circular template with specified dimensions to be used. Templates are to be made by manufacturer.

<1900mm 1% of I.D.

1900- 4750mm 19 mm

> 4750 mm 0.4% of I.D.

D=shell O.D. < .05e +

.002 D

(Max.25mm)

= Irregulari- ties in profile checked with 20 o gauge.

e= thickness pf plate.

This maximum value may be increased by 25% if the length of irregularities does not exceed ¼ of length of shell between two circumferential seams with a max. of 1 meter.

At nozzle positions, greater ovality is permitted if justified by calculations.

Sharp bends, flat spots etc, are not permitted.

Measurement must be made to surface of parent plate and not to a weld, fitting or raised part.

For vessels to be vertically installed but checked horizontally dia, should be measured twice 90o a part after turning the shell through 90o. The sets should be averaged and ovality calculated.

28

I.S. 2525: 1969 I.B.R.

b) Out of roundness is to be less than 1% of I.D. on

D1 + 1250 ; (D1 = I.D.)

200

Whichever is smaller.

At nozzle positions greater values may be permitted. Irregularities in profile (checked by 20o gauge) shall not exceed 3 mm + 5% of min. plate thickness. The max. value may be increased by 25% if the length of irregularity is less than ¼ of length of shell ring.

When out of roundness is measured with shell lying on its side, the measurement shall be repeated after tuning 90 o.

No flats at welded seams are permitted, and departures from circularity must be gradual.

29

B.S. 5500: 1976 ASME SEC. VIII: 1980 (Div.1)

Cold rolling after forming permitted (for small rectification) but N.D.T. must be done. For vessels made of pipes, pipe standards are applicable.

For vessels made or pipes, pipe standards are applicable.

6. WELDED JOINTS

Welding procedures and welders to be qualifies. Test plates to be used only on purchaser‟s request. Consumables used shall be those used in qualification tests.

Welders, welding operators and procedures to be qualified to ASME Sec. IX before any commencement of production welding.

Tack welds if made to approved procedured procedure may be retained.

The areas of removal of attachments may be made through intermediate pieces.

Permanente backing strips not permitted in longitudinal joints but permitted in circumferential joints.

No less than two runs to be used for attachments expect where a agreed by purchaser.

Welding procedures restricted to SMSSW, SAW, GMAW, Oxy-hydrogen. No mechanical pressure or below to be applied except peening, pressure welding pricesses are limited to flash, introduction, resistance, pressure, thermit & pressure gas.

Tack welds to be either removed or their ends grounds. Whether removed on retained they should be made by a qualified welder and procedure

30

I,S, 2525: 1969 I.B.R

Cold rolling for small rectification is permitted but then N.D.T. is essential.

For vessels made from pipes, pipe standards are applicable.

6. WELDED JOINTS (R 604 and R 607)

6.1 a) No welder shall be engaged on welding of boilers or steam pipes unless he is qualified and possesses a certificate.

b) The certificate shall be valid for 2 years.

c) The test specimens shall be examined under X-ray. One tensile test, forward bend test, one reverse bend test two macro examinations shall be conducted. For fillet welds one root bend and one face bend test shall have to be conducted.

d) Record of all welding personnel engaged on welding of boiler or steam pipes particulars of each welder qualification shall be maintained.

6.2 a) If the defects in the weld are distributed over the whole length of the seam the total length of the portions which may be cut out from any longitudinal or circumferential seam, shall not exceed 15% of the total length of the seam.

b) If the defects in the weld are all located in a single continuous length which may be cut out, shall not exceed 10% of the total length of the seam.

c) (R-599) The longitudinal and intermediate circumferential seams shall be made with butt joints of the single or double U or V type or any other type approved by the inspecting Authority.

31

B.S. 5500: 1976 ASME SEC VIII 1980 (Div.1)

E.1. PREHEAT AND OTHER REQUIREMENTS

Ferritic steels may require preheat. Table of temperatures 4.4.1.1 and B.S. 5135 may be used to calculate preheat temperatures. Even tacking to be done with preheat. No welding to be done at tem. < 5 o C. Austenitic steels require no preheat Pre-heat temperatures to be previously decided by manufacturer and purchaser.

Pre-heating requirements given non-mandatory appendix-R.

No welding below 0 O F (-18 O C) Between 0OF and 32OF, preheat to above 60O F required

Vessels shell sections and heads of P 1 Gr.1 & 2 materials fabricated by cold forming shall be heat treatment when resulting max. Fibre elongation is:

Hot-formed parts, if not formed in a range and cooled in a manner to give grain refinement, shall be normalized.

1. More than 40% from as rolled condition.

2. More than 5% when vessel contain lethal substance or requires impact testing or the quires impact testing or the thickness of part before cold forming exceeds 5/8” (16 mm) or reduction in thickness is more than 10%. Formula are given for calculation of extreme fibre elongation.

F.2. POST WELD HEAT TREATMENT (PWHT)

Require for:

a) Ferritic steel vessels where wall thickness exceeds that specified in Table 4.4.3.1. or designed to operate below Oo

C.

b) In general for C and C-Mn steels PWHT is mandatory only above 35 mm thickness.

c) Special Purchaser‟s requirement.

Intermediate stress relief should be carried out at lower temperatures.

No weld repairs allowed after stress relief except on lightly loaded or non-pressure parts. Suitable tests and controls to be instituted to

For carbon steels, lower thickness limit for P.W.H.T. given in notes to Table UCS-56, which also gives the temperatures.

For ferritic vessels enhanced by heat treatment, PWHT requirement given in UHT –56.

PWHT shall be done before hydrostatic test and after any weld repair. A preliminary hydrostatic test to reveal leaks before PWHT is allowed.

In general, for carbon and low alloy steels PWHT is mandatory only for thickness greater than 1 ½”.

32

I.S 2825: 1969 I.B.R

No welding below a base metal temperature of 0o C preheating of 200 mm area to 15o C-20o C to be done before welding in such cases.

(R234 b) plates over 2” in thickness before being fabricated shall be uniformly heat treated to produce gain refinement. Quenching in liquid medium id prohibited.

(R 251) where the plates are bent to a diameter less than 40 times thickness, they shall be heat-treated.

Cold forming over 5% deformation is prohibited unless heat treatment is done. Deformation is calculated as follows:

Deformation = t x 100

D

t= Plate thickness

D= I D bending or forming.

Hot forming out-side normalizing range shall be followed by normalizing.

PWHT- required for ferritic carbon and low alloy steels by normalizing or stress relieving when:

i) It is intended for toxic on inflammable material.

ii) Operation prone to stress corrosion cracking.

iii) There is excessive stress concentration.

iv) There is excessive stress concentration.

v) There is risk of brittle fracture.

vi) Dimensional accuracy id required.

vii) Plate thickness exceeds those given in Table 6.3 (Carbon manganese steels > 30 mm & C-Mn-Cr-Mo on carbon percentage upto 0,35& > 20 mm)

(Regulation No: 562).

All boilers shall be post weld heat treated after completion of all welding and before hydraulic test, when the thickness of the part/welded recess exceeds 50 mm and the carbon content exceeds 0.25%.

Heat Treatment: All boilers shall be stress-relieved by heat treatment after complication of all welding and before hydraulic test, when,

a) Constructed to class I & II requirements

b) The shell thickness exceeds (D/112) + C where D=I.D. of the shell and C=5.6 mm for carbon steel. A stress-relieving heat treatment shall be performed by heating part to at least 600 20oC. When required by the characteristics of the material,

33

B.S.5500: 1976 ASME SEC. VIII: 1980

establish that material is not adversely affected.

34

35

I.S. 2525: 1969 I.B.R.

Different temperatures may be necessary to obtain proper stress relieving. The part to be stress relieved shall be brought slowly upto the specific temperature and held at that temperature for a period proportionate on the basis of at least 2 minutes per millimeter of the maximum thickness of the part (approximately one hour per 25 mm of thickness) and shall be left to cool in the furnace to a temperature to which for the parts with a thickness greater than 20 mm does not exceed 400o C. After withdraw from the furnace the part shall be allowed to cool in a still atmosphere.

A temperature time diagram of the stress relieving process shall be provided for a welded shell or drum and a similar diagram for other pressure parts when the Inspection Authority requires it.

During heat treatment official test plates shall be inside the boiler. Where the shell is subjected to a primary stress relieving treatment identical to the final heat treatment to be given to the boiler, the test shell during primary treatment and hereafter cut up and tested without waiting for the final treatment of the boiler.

Where the shell is not subject to primary stress relieving treatment or is subjected to primary stress relieving treatment, which is not identical with the final heat treatment the test plates may be placed inside any other boiler of comparable dimensions, which is to be heat treated in accordance with this chapter.

Temperature charts shall be submitted to indicate that the test plates and the boiler they represent, have been subjected to identical heating, soaking and cooling treatment.

36

B.S: 5500: 1976 ASME SEC. VIII 1980 (Div.1)

E.3. METHODS OF P.W.H.T

Normally full vessel to be stress relieved but in special cases the following method may be applied.

1. In sections, with minimum 1500

mm or 5 Re overlap, whichever

greater (R= internal radius, e=thickness). The portion outside shall be shielded so that longitudinal temp. gradient is such that the distance between peak and half peak temperature is more

than 2.5 Re .

2) Circumferential seams may be heat treated locally by heating a shielded band round the entire circumference. Width of heated

band should exceed 5 Re is

recommended.

3) Branches/attachment shall be locally heat treated by heating a shielded circumferential band round the entire vessel. The requirements in (ii) apply except that width of circumferential band

(2.5 Re ) shall be measured from

edge of welding which connects nozzle/attachment to the vessel.

iv) Vessel may be internally heated fully encased with thermal insulating material.

v) Vessels with thickness ration not more than 2:1 may be heat treated in the same furnace according to the same furnace according to the requirements of the thickest vessels.

For MO or M1 type materials (carbon and carbon manganese

Whenever practicable, vessels should be PWHT as a whole, if not, they may be heated inspections with 5 feet overlap and adequate shielding of portions outside furnace.

Circumferential seams may be heated locally, but width of band on each side of weld shall be more than two times shell thickness. Shielding to be provided outside the heated bond.

Heating the inside with adequate insulation on the outside and recording and measuring of temperature is allowed provided the internal pressure never exceeds 50% of working pressure.

Heating a circumferential band-containing nozzle on other attachment which should extent round the entire vessel and at least 6 times the plate thickness beyond attachment welding. Circumferential joints in a pipe may be treated by heating a band on each side of center line wider than 3 times the width of weld.

Thermocouples to be attached to top center and bottom of charge and any other zone of possible temp. variation. Gas temp. measurement is not enough.

No limit specified on the ratio of thickness of vessels that can be heat-treated together but cycle should conform to the thickest vessel.

37

I.S. 2825: 1969 I.B.R

More or less same as in BS 5500 except the followings:

i) PWHT mandatory for:

a. Low strength carbon and carbon manganese steels (yield strength 26-38 kgf/mm2) 30 mm and above, high strength carbon and carbon manganese steels (YS 44Kgf/mm2 and containing Cr.V, Mo etc. )20 mm & above.

b. Toxic or inflammable material carrying vessels.

c. Operation below 0o C.

D. Vessels subjected to severe local stress concentration.

e. Dimensional accuracy required

38

B.S. 5500: 1976 ASME SEC VIII 1980 (Div.1)

steels the temp. and time given in 4.4.3.1. to be followed. For other grades, the ranges are advisory. The temp, in general for MO & M1 are 5800 to 6200c.

Normally, the temp, of furnace while charging shall be 4000 C. For complex cases, e.g. thickness > 60 mm temp. is 3000 C.

For carbon and low alloy steels the foll. Hold:

Temp, or furnace while charging shall be less than 8000 F (4270 C)

Heating rates 2200c/hr for thickness upto 25mm.

5500/ e00 /hr on 550C /hr which ever greater, for thickness greater than 25 mm.

During heating, temp, variation to be less than 1500 C with 4500 mm length.

Cooling rates (Cooling TO 4000 C)

275

2750 C /hr for t < 25 mm.

5870 C /e0 C /hr which – ever greater for t>25 mm.

Below 4000 C, cooling in still air.

Temperature re the actual ones determined by thermo couples.

Holding times are given in Table 4.4.5.1. but in general are 2 ½ minutes per mm thickness.

Heating rate- 2200 C/hr divided by the max. Metal thickness in inches. (but not more than 2220 C/hr).

Cooling rate- 2780 C/hr divided by the max. metal thickness in inches.

The heading and cooling rates need not be less than 560 C/hr.

Soaking time-1 hr per inch thickness upto 2 inches.

39

I.S. 2525: 1969 I.B.R.

Cooling rate upto 25mm metal thickness 2750C/hr and over 25 mm, 7000/metal thickness 0C/hr or 550C/hr whichever greater

40

B.S. 5500: 1976 ASME SEC VIII, 1980 (Div .1)

-2 hrs plus 15 min for every inch of ma. Metal thickness above 2 inches

F.1. PROCEDURE AND WELDER QUALIFICATION:

Below 4270C, cooling in still air.

A list of all welding procedure to be supplied by manufacturer. Welding of test plates and testing to be witnessed by purchaser unless previous qualification records are produced.

For low temp, operation, impact testing as per Appendix-D to be done.

Qualification records to be supplied to inspector before commencement of work, Welds to be identified by welder‟s number at every 3 feet. Welder or operator qualified for one manufacturer shall not be used for another manufacturer. Qualification as per ASME Sec. IX.

List of welders to be presented to purchaser. Welder qualified by one inspected authority may be accepted by another. A welder who qualifies a procedure is him-self qualified. Qualification of welder is valid for six months of inactivity. Relevant specification are:

Impact test requirements given in subsection C, (Requirements pertaining to classes of materials) UCS-65 for carbon & low alloy steels UHA-51 for high alloy steels.

Procedure qualification BS 4870 Part I.

Welder qualification BS 4871 Part I.

F.2. PRODUCTION CONTROL TEST PLATES

Not normally required unless insisted by purchaser. The length of plates to be at least 350 mm. Number and size have to be agreed upon. Circumferential joint test plates to be welded separately.

Test plates are not required for production control, but for carbon and low alloy steels, test piece to be made for vessel material and subjected to the same heat treatment as vessel (with slight variation). P-1 Gr.1 & 2 and standard materials listed in UG-11 (a) and excluded.

At the option of the manufacturer N.D.T. to be done on test plates like on the production weld. If defects found somewhere, test pieces may be out from remaining portion.

For vessels constructed of type 405 Material, which vessels constructed of Type 405 material which are not PWHT (post weld heat treated), welding test plates for two face bend specimens required.

41

I.S 2825 : 1969 I.B.R.

Records shall be made available to inspector. Each welder shall stamp his number.

A welder is qualified for 6 months of in-activity. Re-qualification is not necessary if the company proves having made such jobs if (or better jobs) for past 3 years.

Qualification requirements given in art 7.1 of IS 5825 (including impact test requirements).

(604)

a) No welder shall be engaged on welding o boilers or steam pipes unless he is qualified and possesses a certificate.

(607)

b) The certificate shall be valid for 2 years.

c) The test specimens shall be examined under x-ray. One tensile test, forward bend test one reverse bend test, two macro examinations shall be conducted. For filler welds one root bend and one face bend test shall have to be conducted.

a) Vessels subjected to serve duty (efficiency factor 0.9-1.0 ) to be provided with two test plates to represent longitudinal seam of first six shells of vessel. No test plate normally required for circumferential seam- unless welded by a different process.

Test to be conducted are:

All weld metal tensile (1), Reduced section tensile (1)

Bend (2), Notched bar impact (3) Macro (1).

d) Record of all welding personnel engaged on welding of Boiler or steam pipes particulars of each welder qualification shall be maintained.

(561)

2.1 Class 1 Boilers: Test specimen shall be attached to each L-seam.

a)One Tensile test specimen for the weld seam.

b) One all weld metal tensile test.

c) Two bend test specimens.

d) Two impact specimens.

e) One specimen each for micro and macro examinations.

42

B.S. 5500: 1976 ASME SEC VIII: 1980 (Div .1)

Tests specified on production control test plates are, macro examination, hardness survey, transverse tensile, all weld tensile, face, side and root bend and fillet weld fracture.

F.3.DETAILS OF DESTRUCTIVE TESTS FOR ALL APPROVAL TESTS:

a) All weld tensile strength and parent metal strength difference to be agreed upon.

b) Reduction in area for weld metal in Mo & M1 to be > 35% and at least equal to parents metal for alloy steels.

c) In transverse bend (t < 10 mm) cracks upto 1.5 mm allowed.

d) In transverse bend (t> 10 mm) cracks upto 3 mm allowed.

e) An excess of 50 HV over that specified for weld metal (in the procedure) is allowed.

f) For tensile bend tests, two retests allowed.

If tensile specimen breaks in base metal outside the fusion line, then specimen is acceptable provided the strength is not more than 5% below the specified minimum tensile strength for base metal.

43

I.S. 2825: 1969 I.B.R.

b) Vessels subjected to medium duty (efficiency factor 0.8 – 0.85) shall be provided with two plates to represent all long seams. No welds for circumferential seam unless welded by a different process.

2.2 Class II Boilers: Test pieces shall be attached to each (561) L-seam

a) One tensile test specimen for weld seam.

b) One bend test specimen

c) One reverse bend test specimen.

d) One nick break test specimen.

2.3 Pipes

a) Tensile test specimen

b) Flattening test Specimen

c) Bend test specimen

3.1 Tensile tests:

The ultimate tensile stress shall be not less than the lower limits specified for the plates.

3.2 All weld metal: (561)

(a) The UTS shall not be less than the lower limits specified for the plate.

(b) The elongation shall be not less than 20% of the gauge length or four times the square root of the cross sectional area.

(c) Reduction in area shall nor be less than 35%.

Tests to be conducted are:

i) Reduced section tensile (1)

ii) Bend test (2)

iii) Nick break

Production test plates may be radiographed and defective portions discarded in cutting specimen.

Macro examination of fillet weld specimen should not reveal cracks, incomplete root fusion, inequality in leg length more than 1.5 mm.

3.3 Bend Test: (561)

No cracks or defects on the outer surface of the specimen shall be greater than /16” (1.5 mm) measured across the specimen or 1/8” (3 mm) measured along the lengths of the specimen.

3.4 Izod Impact Test: (561):

Impact values shall not be less than 20 FT. Ib.

3.5 Radiography (265)

a) Where defects occur in distributed positions in a seam, repairs to the extent of 15%

44

B.S. 5500: 1976 ASME SEC. VIII: 1980 (Div.1)

45

I.S. 2825: 1969 I.B.R.

of the total length of the seam shall be permitted.

b) Where the defects are located in a single continuous length the permissible extent of repair shall be decided by the Inspecting Authority.

3.6 Additional Tests before Rejection (561):

If the tests show a definite sign of failure, two further tests of the same king shall be conducted in the same manner. The two tests should satisfy the requirements of the standards. If either of the two tests fail the representative weld is liable for rejection.

3.7 Macro and Micro:

A specimen of the full thickness of the plate and not les tan half an inch wised shall be provided from each set be test plates for the purposes of Macro examination.

46

B.S. 5500: 1976 ASME SEC VIII: 1980 (Div.1)

G.NON DISTRUCTIVE TESTING

This is required for final acceptance but may be used before also. The N.D.T. personnel to be qualified (with certificates). All N.D.T. stages, standards and procedure to be written down an agreed upon.

Before examining welds, plate material adjacent to welds shall be ultrasonically tested to establish thickness and defect flaws.

For category 1 vessels final N.D.T. to be done after PWHT and before any pressure test. 100% X-ray or U.T. of pressure welds where thickness part exceeds. Table 5.6.4.11. Welds other than full penetration but shall be D.P/ M.C.D. tested.

For Category 2 vessels, 100% X-ray/U.T. of full penetration butt welds (which shall include each T-joint). For each seam there shall be one radiograph or U.T. for 200 mm.

At least 10% of all welds other than main seams to be D.P/M.C.D. tested. Also when openings occur in or within 12 mm of weld-welded seams, such seam shall be additionally N.D.T. tested on each side of opening for a distance equal to the diameters of opening.

When a particular representative N.D.T. Is found unsatisfactory (with reference to Art 5.7) the whole seam represented by it shall be scrapped.

For Category 3 vessels N.D.T. is not required. However, in so far as M.C.D and D.P. are

The manufacturer shall certify the competence of D.P/M.C.D. testers including their eyesight. For U.T. personnel and radiography personnel qualification to be in accordance with SNT-TC IA. N.D.T. procedures to be outlined in the written QC system ahs to be submitted to inspector.

All material should be examined before fabrication to defect as far as possible defects that would affect the safety of the vessel. Particular attention should be given to the edges and other parts or rolled plates for serious laminations, shearing cracks etc.

Foll. Joints are to be 100% radio graphed

1) All but welds in vessels containing lethal substances.

ii) All butt welds in plates or vessel walls where thinner plate exceeds 1 ½ inches (38 mm) or exceed the lesser thickness in UCS – 57.

III) All butt welds in unfired steam boilers with pressures more than 50 psi (3.5 Kg/Cm2)

iv) All category A& D butt welds with efficiency 1.00 for double welds joints and 0.9 for single welds joints (Ref. UM-11).

For foll joints spot radiography is to be done

i) Double welded but joints with efficiency 0.85 and single welded joints with backing strip and efficiency 0.8.

No radiography required for the following.

1) Double welded butt joints with efficiency 0.70.

47

I.S. 2825: 1969 I.B.R

Stages of inspection are decided by the class vessel. Records of inspection and tests to be maintained for the inspector.

All anstenitic chromium – Nickel alloy steel welds in plates over 20 mm thick shall be examined by dye penetration test.

Radiography

i) For circumferential butt welds in extruded connections, pipes, tubes, hearers etc;

a) No radiography for t < 6mm

b) No radiography fort = 6~12mm and O.D. < 102 mm.

c) Where 12< t< 20mm and 102< random selected from each welder‟s work a maximum of 5% length shall be examined.

d) For constructions exceeding Limits of (c), all welds to be examined.

ii) Butt welds in furnaces combustion chambers and other pressure parts subjected to external pressure to be spot radio graphed. Butt weld in fully supported end plated not to be radio graphed.

iii) Spot radiography is to be at lest 10% of the total length. Each radiograph to be at lest 25 Cm.

Other N.D.T. methods may be agreed upon and used where radiography is not possible i.g. fillet welds or braches etc. or where it is expedient.

(561)

Every portion of the longitudinal and circumferential butt-welded seams or the shell of the boiler shall be subjected to radiographic examinations.

The methods employed in obtaining the radiographs shall be such as to show clearly difference equal to 2% of the thickness at the welded joints. To determine whether this result is being attained an indicator of approved form which includes a portion, equivalent to not more than 2% of the joint thickness shall be placed in the thickness shall be placed in the vicinity of the weld so as to make a record on each radiograph.

Each section of every weld shall be marked so that the radiographs can be easily correlated to the particular part of the seam represented.

The examination shall be made from the original films and the acceptability of the welds shall be decided by the inspecting Authority. The welds deemed unsatisfactory shall be rejected or dealt with under the condition of % R 560 and be radio graphed again. The films shall be retained by the manufacturer for a reasonable period for reference and be available to the Inspecting Authority, if required.

48

B.S. 5500: 1976 ASME SEC VIII: 1980 (Div .1)

aids to visual examination, they may be used

Choice of N.D.T. for Welds

There is a guidance for selection between radiography and U.T. for internal flaws (e.g. the two methods being suitable the two methods being suitable for “Volume “ and Planner” defects repressively and that sensitive U.T. techniques may be given too conservative results.

For surface flaws, difference between M.C.D. and D.P. has been given.

General guidance for N.D.T. Radiography

1. For thickness upto 50 mm X-ray to be normally used.

2. Marking on radiography to indicate work piece reference no.(ORDER NO., S.No. etc.,) joints, selection of joints, arrows or other symbol to identify its position radiographs of repair welds shall be marked R1, R2 (First repair, second repair etc.,)

3. Radiographs should have sufficient overlap.

ii) Single welds/ butt joints (with backing strip) with efficiency 0.65.

iii) Single welded butt joints without backing strip and efficiency 0.6.

iv) Lap joints.

U.T. may be substituted for radiography for the final closing seam of a vessel if the construction does not permit interpretable radiographs.

In addition to radiography electron bean welds should be 100% ultrasonically tested.

Opening that do not meet reinforcement requirements in UG-37 may be located in circumferential joints provided radiographic requirements of UW-51 for a length equal to 3 times dis. Of hole are met.

When a pressure part i.e, head or shall or is to be welded to a forged or rolled plate thicker than ½” to form a corner joint under the provisions of UM-13 (e), all cut edges including by M.C.D. or D.P. Tests. Ultrasonic Testing

i) Before testing weld, the present material shall be ultrasonically tested to establish thickness and any flaws, which might prevent effective weld examinations.

MARKING

Permanent marking beside the weld shall be made to correlate with N.D.T. reports stamping shall not be done vessels fro low temperature service.

49

I.S. 2825: 1969 I.B.R

50

B.S. 5500: 1976 ASME SEC. VIII: 1980 (Div .1)

All material that are to be impact tested shall be inspected for surf cracks.

Pressure vessels, which are to be pneumatically tested, shall have full length of the foll. Welds crack detected by D.P. or M.C.D.

1. All welds round openings.

2. All attachment welds, including welds attaching non-pressure ½ arts to pressure parts having a throat than ¼ inch. (6.5 mm).

Heads attached with one plate off set circumferential joints, which have a longitudinal joint shall be M.C.D. or D.P. tested from the edge of plate tested from the edges of plate through the off set as shown. (See sketch).

All austenitic Cr-Ni alloy steels in plates our ¾” thick and all 36% nickel steel welds shall be D.P. tested after heat treatment (Ref. U.H.A.-34).

All electro slag welding in ferritic materials shall be 100‟ ultrasonically tested after gain refining (austenising) heat treatment or P.W.H.T.

General Guidance for N.D.T

All radiography to be as per ASME Sec. V article 2. A complete set or radiographs and records (T 283(a) & (b) Article 2 ASME SEC V) TO BE retained by manufacturer for 5 years spot radiographs may be discarded after the acceptance of vessel by inspector.

ACCEPTANCE LEVERS FOR N.D.T.

Notations

e - parent metal thickness (thinner part for dissimilar joints)

w - Width of defect

L - Length of defect

h - Height of defect

FULL RADIOGRAPHY

For radiography and U.T. the foll. Are unacceptable.

1. Any crack, zone of incomplete fusion or penetration.

2. Any elongated slag inclusion which is longer than:

51

52

I.S. 2825: 1969 I.B.R

In butt welds concavity in root and excessive penetration may be permitted subject to approval of inspector, but lack of root of side fusion are not permitted.

Undercuts overlaps, abrupt rides or valleys or irregular beads are not permitted.

53

B.S. 5500: 1976 ASME SEC. VIII. 1980 (Div.1)

ø = Diameter of defect. ¼ in (6.5 mm) for t upto ¾ in (19mm).

C = Mean nozzle circumference. 1/3/ t for t ¾ in to 2 ¼ in (19-57 mm)

UNACCEPTABLE DEFECTS ¾ in (19 mm) for t over 2¼ in (57mm)

Cracks or lamellar tears. Where it is the thickness of weld.

For radiography, in addition to above, any group of slag inclusions in line that have an aggregate length greater than “t” in a length 12 t, except when the distance between them exceed 6L where L is the longest imperfection.

Porosity charts are given in Appendix IV.

Planar defects

Lack of root, side and inter-run fusion

Lack of root penetration

Not permitted

Isolated pores (for individual pores in group)

ø e/4 and ø

3.0 mm for e up to 50 mm

Spot Radiography

One spot radiograph shall be examined in each 50 ft. of welding in each vessel. Minimum length of spot radiograph is 6 inches. Foll. Are the acceptance levels:

Uniformly distributed localized porosity

ø 4.5 mm for e 50 to 75mm

1. Any type of crack, zone of incomplete fusion on penetration is unacceptable.

Linear Porosity ø 6.0 mm for e > 75 mm

2. Slag inclusion or cavities graters than 2/3 T, where T is the thinner or the two plates welded.

Uniformly distributed localized porosity

2% by area (on a radiography) for e > 50 mm and prorate for higher thickness.

3. The sum of the longest dimensions of imperfections should not be more than T in a length 6 T and the longest imperfections considerate are separated by at least 3I where L is the length of largest imperfection

Linear Porosity Linear porosity parallel to weld axis may indicated lack

4. Porosity is not a factor in spot radiography.

54

of fusion or penetration and thus not permitted.

Worm holes (isolated)

1 > 6 mm, W > 1.5 mm As linear porosity.

LIQUID PENETRANT (D,P) EXAMINATION

Worm holes (aligned) crater pipes

As worm holes isolated

1. Linear indications, with length more than 3 times the width will be unacceptable if longer than 1/16 in (1.6 mm).

Surface cavities Not permitted 11. Four or more rounded defects (I,e. those with length less than 3 times the width) in a

55

I.S 2825: 1969 I.B.R

56

B.S. 5500: 1976 ASME SECI VIII 1980 (Div.1)

Line separated by 1/16 in (1.6 mm) or less

Individual and Parallel to major axis

Individual and randomly oriented (not parallel to axis of weld)

Main butt welds

L=e 100 mm

worm e/10 4

mm

Magnetic particle (M.C.D) Examination

All linear discontinuities are defects unless proved otherwise by re-examination.

Some other criteria of acceptance according to this code are:

Butt joints shall have complete joint penetration & fusion shall be free from undercuts, overlaps, abrupt ridges or valleys.

Fillet welds shall have adequate penetration into the base metal.

Reinforcement not butt welds not be exceed following:

Nozzle & branch welds

Inner half of cross sec

Outer quarter of cross sec

Worth = e/4

4mm

I=c/4

100mm

Worth = e/8

4mm I=c/8

1000mm

As isolated pores

Non linear group

As localized porosity Plate thickness

Up to 1/2 in (12 12.5mm)

Over ½” (12.5 mm)

Over 1” (25.4 mm) to 2” (25.4 mm)

Over 2” (50 mm)

Reinforcement

1/6 in (4 mm)

3/32 in (2.4 mm)

1/8 in (3.2 mm)

5/32 in (4 mm)

Copper inclusions not permitted

Under cut

Shrinkage grooves & root concavity

Excess Penetration

Reinforcement

Overlap

Slight intermitted permitted depth < 0.5 mm

Slight intermitted permitted depth < 1.5 mm

h 3mm

Smoot blending

Not permitted

In U.T defects with „h‟ 1.5 mm or less should be ignored

57

I.S. 2825: 1969 I.B.R

Reinforcement in severe and medium duly vessels shall be:

Plate thickness Max,

reinforcement

Up to 12 1.5

Over 12 up to 25 2.5

Over 25 up to 52 3.0

Over 4 52 4.0

For light duty vessels, reinforcement shall be < 5 mm

58

B.S 5500: 1976 ASE SEC VIII: 1980 (Div 1)

H. PRESSURE TESTING

All completed vessel must pass either of the following tests?

All complete vessels must pass the standard hydrostatic, pneumatic or proof test.

Standard hydraulic test: Where required thickness of pressure parts can be calculated.

Pneumatic test: Where thickness of pressure parts can be calculated, but liquid media are not practicable.

Proof hydraulic test: Where thickness of pressure parts cannot be calculated.

Combined: Hydraulic/pneumatic test.

Method of testing

Pressure to be increased to 50% of test pressure gradually and then in stage of 10% until test pressure is reached before going close for inspection, the pressure is to be lowered below that previously attained.

The pressure is to be maintained for at least 30 minutes expect in case of vessel less than 500 mm dia, and 10 mm thick when the period may be agreed upon.

(No shock loading (hammer testing) allowed.

Test Pressure

Pt= 1.25 (P fa/ft X t/t-c)

Where, P= design pressure

fa= Nominal design stress

at least temperature

ft= Nominal design stress

at design

Hydrostatic test: Except for enameled ones vessels designed for internal pressure, shall be subjected to a test pressure at least 1 ½ time the max. allowable working pressure (to be marked on vessel multiplied by the lowest ratio of stress value „S‟ for the test temperature).

A calculated pressure may also be used by mutual consist between user and manufacturer which is 1 ½ times the “ basis for calculated test pressure” defined in U.S- 60 (e).

Any intermediate value between the two given above may also be used. There is no upper limit, but visible permanent distortion may cause rejection.

Following the application of test pressure any inspection for leaks shall be made at not less than to thirds the test pressure unless specially agreed upon (e.g. when gas leak test is applied. Any non-hazardous liquid at any temp. below its boiling point may be used.)

Pneumatic test: except for enameled vessels, for which the pneumatic test pressure shall be at least equal to the maximum allowable test pressure, the pneumatic test pressure shall be 1.25 times the maximum allowable working pressure multiplied by the lowest ratio of the test value at test temperature to stress value at design temp.

59

I.S. 2825: 1969 I.B.R.

(R 601 Hydraulic and Hammer tests).

The time of holding at the calculated test pressure shall be a minimum of 10 minutes.

a. Class-I-Boilers: Each class boiler shall on completion of all welding and/or repair and after heat treatment be subjected to a hydraulic test of 1 ¼ times the working pressure and while under this pressure the welds shall be given a through hammer test throughout their length. The pressure shall be released and then raised to 1 ½ times the working pressure + 50 psi and steadily maintained for a length of time sufficient to carryout complete inspection but not less than ½ hour.

Vessels shall be well hammered on both sides of welds seam. Materials deleteriously affected by hammering and which have been radio graphed on main seems require no hammer test.

Test pressure:

b. Class ii-Boilers: Each class II boiler shall aster heat treatment be subjected to the same form of test as for class-I boilers, except that every Boiler shall be given a hammer test and hydraulic pressure to be applied for the test shall be 1 ½ times the working pressure. The pressure shall be released and then raised to twice the working pressure.

Test Pressure

Pt= 1.3 x design pressure x f1/f2

fi= allowed material stress at test, temperature.

f2= Allowable material stress at design temperature.

This test pressure includes the amount of any static head acting at a point under consideration.

60

B.S. 5500: 1976 ASME SEC VIII 1980 (Div.1)

temp. exceed the temp, for which elevated temp, proof stress values are available, then ft should be derived from the proof stress at the highest temp, for which values are available.

The pressure shall be increased to half the test pressure and then in steps of one teeth the test pressure. Then the shall be reduced to four fifths of the pressure and held for a sufficient time to permit the inspection of the vessel unless waived by mutual consent (e.g. when gas leak test applied)

t = Nominal thickness of section under consideration.

For proof test, the brittle coating test displacement-measuring test may be used.

c = Corrosion allowance

For proof test, the brittle coating test, displacement measuring test or strain. I measuring test may be used.

61

I.S. 2825: 1969 I.B.R

Vessels designed vacuum or partial vacuum shall be subjected to a pressure of 1.3 times the difference between normal atmospheric pressure and the internal absolute pressure but no in any case less than 1.5 Kg/Cm2

No procedure for proof test given.