post construction codes overview of asme pcc-2.pdf

10/7/2010

N. Al-Khirdaji, AZTech Sr. Consultant 1

5.3 Post Construction Codes

• Overview 0f ASME PCC-2

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Integration Of In-service Inspection and Repair Codes and Standards

Scope of PCC-2 Standard• Covers equipment within the scope of API and ASME

Pressure Equipment Codes and Standards including:Pressure Equipment Codes and Standards, including:– Piping and pipelines including piping components (such as

valves, flanges and fittings)– Boilers/Heaters– Pressure vessels (including heat exchanger bundles)– Storage tanks.

• Coverage is not limited to equipment built to ASME Codes• Covers repairs after equipment has been placed in service. • Repairs during construction are covered by the new

construction codes.

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Organization of PCC-2 Standard

• This Standard is divided into five Parts.Part 1 covers the scope organization and intent and is applicable to all– Part 1 covers the scope, organization, and intent and is applicable to all articles in this Standard. Table 1 provides guidance for the applicability of repair methods listed in this Standard.

– Part 2 covers repair methods and techniques that include the use of welding, brazing, soldering, or other methods involving metal deposit.

– Part 3 covers mechanical repairs, with or without sealant, such as bolted clamps or fixtures and includes all repair methods not covered in Part 2 or Part 4Part 2 or Part 4.

– Part 4 covers repairs using nonmetallic means, such as nonmetallic liners and wraps, and bonding (e.g., joining by epoxy), including bonding of metallic components.

– Part 5 covers examination and testing methods and techniques.

Table 1 Guide for the Selection of Repair Technique

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Organization of PCC-2 Standard

Standard Outline/Format for Each Article:• Description of the repair• Limitations and Precautions associated with the repair• Design/Fabrication issues associated with the repair• Examination and Testing QA/QC practices following

the repairp• Additional references

PCC-2: Welded Repair Articles• Repair Method for Butt Welded Insert Plates in Pressure Components• External Weld Overlay to Methods for Internal ThinningExternal Weld Overlay to Methods for Internal Thinning• Seal Welding Threaded Connections and Seal Welded Repairs• Full Encirclement Steel Sleeves for Piping• Welded Leak Enclosures • Fillet Welded Patches with Reinforcing Plug Welds• Alternatives to Traditional Welding Preheat• Alternatives to Post Weld Heat TreatmentAlternatives to Post Weld Heat Treatment• In-Service Welding onto Carbon Steel Pressure Components or

Pipelines• Weld Buildup, Weld Overlay and Clad Restoration• Fillet Welded Patches• Threaded or Welded Plug Repairs

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PCC-2: Mechanical Repair Articles• Replacement of Pressure Components• Freeze Plugging• Freeze Plugging• Repair of Damaged Threads in Tapped Holes• Flaw Excavation and Weld Repair• Flange Refinishing• Mechanical Clamps• Pipe StraighteningPipe Straightening• Repair Guidelines for Damaged Anchors in Concrete• Hot and Half Bolting Removal Procedures• Inspection and Repair of Shell and Tube Heat Exchangers

PCC2: Non-Metallic Repair Articles

• Non-Metallic Composite Wrap Systems for Pi i d Pi li Hi h Ri k A li tiPiping and Pipelines: High Risk Applications

• Non-Metallic Composite Wrap Systems for Pipe: Low Risk Metal Pipe

• Non-metallic Internal Lining for Pipe-Sprayed Form for Buried PipeForm for Buried Pipe

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PCC-2: Examination & Testing Articles

• Examination and testing requirements for each ifi t f ifi i d ispecific type of specific repair are covered in

the last section of each article• However, Two Separate Generic Examination

and Testing Articles are also included:– Pressure and Tightness Testing of Piping andPressure and Tightness Testing of Piping and

Equipment– NDE in Lieu of Pressure Testing

•

Repair LifeM f th i t h i i l d d i thi St d d• Many of the repair techniques included in this Standard are considered to be permanent, intended to remain in place for the life of the repaired component. Others may only be suitable for short-term service, and should be replaced with a more permanent repair at the appropriate opportunity.

• The anticipated life of the repair depends on many circumstances, and could include consideration of risk.

• As such, this Standard does not classify repair methods as permanent or temporary.

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Highlights of ASME PCC-2

• Welding - Requirements for welding, including qualification of welding procedures welders andqualification of welding procedures, welders, and welding operators, should generally follow an applicable code of construction or an applicable post-construction code, except when otherwise specified herein.

• Allowable Stress - Calculations involving theAllowable Stress Calculations involving the allowable stress use the allowable stress from the original code of construction or an applicable post-construction code, unless otherwise specified in specific articles.

ASME PCC-2 Article 2.1 - Butt-Welded Insert Plates in Pressure Components

• The repair of pressure components by butt-welded insert plates involves the replacement of pressureinsert plates involves the replacement of pressure boundary material in a pressure component with an insert plate attached by full penetration butt welds. This repair method is applicable to cylindrical, spherical, and conical shells and to flat pressure components. It may be used for single and double p y gcurvature shells. It may also be used on other pressure components (such as formed heads) if the curvature of the replaced section matches the curvature of the original pressure part.

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Fig. 1 Flush Insert in Pipe or Tube

NOTES:(1) Side view of cutout in pipe or tube

ith d b l (Fi 1 h i lwith edge bevels. (Fig. 1shows single-grooved joint detail with 25 deg to 35 deg edge bevel in pipe or tube. Other joint details and edge bevels may be used, as appropriate for a particular weld joint.)

(2) Plan view of insert with edge bevels. (Fig. 1 shows an insert with one-sided joint detail.)

(3) Side view of the insert with edge bevels. (Other joint details and edge bevels may be used, as appropriate for a particular weld joint.)

(4) Side view of welded insert in pipe or tube.

Table 1 Guide for the Selection of Repair Technique - Notes

(1) This method may apply to replacement of nozzles, flat spots, and dents.(2) See Part 2, Article 2.1, Limitations.(3) This repair technique applies to seal welded threaded joints for leak tightness.(4) Welded leak box repair applies to leaking flanges, valves, pipe components, and welded and mechanical joints.(5) For internal defects, the cause of defect shall be understood or arrested or a Type B sleeve is recommended.(6) Alternative provisions for weelded repair.(7) Also may apply to new construction or to all methods requiring welding.(8) Generally appropriate for surface welding on carbon steel substrates.(9) This technique is used for isolating sections of pipes.(10) R i f d d th d i t d h l(10) Repair of damaged threads in stud holes.(11) Also applies to the repair of hardened surfaces.(12) Radial cracks.(13) Gasket and packing leaks p Y.(14) Pipe straightening.(15) Repair of damaged anchor in concrete.(16) This is not a repair technique; however, it may apply to most methods of repair.(17) This is an alternative to pressure testing.

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Fig. 2 Flush Insert Plate (With or Without Nozzle/Manway) With Its Butt Weld Intersecting

Existing Butt Weld in Shells or HeadsNOTES:(1) Existing butt weld in vessel shell or head (Fig 2 shows buttshell or head. (Fig. 2 shows butt weld in a cylindrical shell.)(2) Thirty deg minimum angle.(3) Full RT or UT, or MT or PT both sides of existing butt weld, 100 mm (4 in.) min. each side of intersection with insert plate.(4) Insert plate butt weld. Full RT or UT, or MT or PT both sides of weld.(5) For nonpostweld heat-treated carbon and low alloy steel nozzle/manway assemblies, 150 mm (6 in.) minimum between the toe of the

ASME Post Construction SubcommitteeOn Repair And Testing

• Traditionally, International Codes and Standards have ad t o a y, te at o a Codes a d Sta da ds avefocused on new construction because these standards are essential for both domestic and international trade.

• In the past, maintenance and inspection of fixed equipment have been handled on a local, regional or industry sector basis.

• In some cases, rules for maintenance and inspection are t bli h d b l t th itiestablished by regulatory authorities.

• More recently, it has been recognized that broadly based international standards for maintenance and inspection are desirable to ensure worldwide acceptance of the best available approaches.

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ASME PCC-2: Repair of Pressure Equipment and Piping

• Provides methods for repairs of equipment & piping within the scope of ASME Pressure Technologywithin the scope of ASME Pressure Technology Codes & Standards after they are placed in service.

• May be temporary or permanent, depending on the circumstances.

• Provides only technical procedures and information; administrative or policy requirements are outside itsadministrative or policy requirements are outside its scope.

ASME PCC-2: Organization

Section 1 – covers Scope, Organization & IntentSection 2 – repair methods involving welding, brazing,

soldering, or other methods involving metal depositSection 3 – mechanical repairs, with and without sealant,

such as bolted clamps & fixturesSection 4 – repairs using nonmetallic means, such as

nonmetallic liners and raps and bondingnonmetallic liners and wraps, and bonding Section 5 – covers examination and testing methods and

techniques

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Mechanical Clamp RepairO

ther

Longitu

Circum

Cra

Lamina

Blisters

Gouge

Pitting

Local w

Genera

(1) R R N N N Y Y N Mechanical Clamp

udinal cracks

mferential cks ations

s s

wall thinning

al wall thinning

Y = Generally appropriate. S = Although may be acceptable, is not generally used for this condition. R = May be used, but requires special cautions. N = Not generally appropriate. Note (1): Normally, mechanical clamps are used to contain leaks at packings, and at flange and gasketed joints, or to contain leaks/potential leaks due to

Welded Leak Box Repair

Other

Longit

Circum

Cracks

Lamin

Blister

Gouge

Pitting

Local w

Gener

(1) R R N N N Y Y N Leak Repair Box

tudinal cracks

mferential

s ations

rs

es

g wall thinning

ral wall thinning

Y = Generally appropriate. S = Although may be acceptable, is not generally used for this condition. R = May be used, but requires special cautions. N = Not generally appropriate. Note (1) Welded leak repair box applies to leaking flanges, valves, pipe components, welded

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Weld Overlay Repairs on Carbon Steel Piping

The weld overlay repair provides a practical technique for repairing degraded walls of piping components. As shown above, the weld overlay restores the load carrying capability and integrity of the repaired location through the application of external weld material.

External Weld Overlay Repair Methods for Internal Thinning - 1

• When appropriate, applying a weld overlay repair to the exterior of a locally thinning pressure component y g p p(pipe/pressure vessel) will provide the necessary structural reinforcement and will eliminate the need for either total replacement of the component or an internal weld repair.

• A weld overlay procedure may be used to structurally restore steel components (CS, low-alloy, or austenitic SS materials suitable for welded construction) to theSS materials suitable for welded construction) to the appropriate wall thickness without resorting to replacement efforts. In some cases, it may be possible to perform a repair while the component is in operation.

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• A weld overlay shall not be used for structural reinforcement when there is indication of any form ofreinforcement when there is indication of any form of cracking.

• The user shall evaluate the flammability, volatility, or potential reactions of the medium within the pressure component prior to application of any welding process.E l f di h h ld b l• Examples of process media that should be properly flushed from the system prior to repair include hydrogen, hydrogen cyanide, oxygen, alkaline/caustic materials, butadiene, acetylenic compounds, H2S, chlorine and acids.


Other

Longitu

Circum

Cra

Lamina

Blisters

Gouge

Pitting

Local w

Genera

(1) N N N S Y Y Y N Weld Overlay Repair

udinal cracks


s s

wall thinning

al wall thinning

Y = Generally appropriate. S = Although may be acceptable, is not generally used for this condition. R = May be used, but requires special cautions. N = Not generally appropriate. Note (1): Normally, mechanical clamps are used to contain leaks at packings, and at flange and gasketed joints, or to contain leaks/potential leaks due to

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The weld overlay shall meet the following:• The nominal chemistry of the deposited weld metal should

h h b i lmatch the base material.• The tensile strength of the deposited weld metal shall be at

least that of the base metal to which it is applied.• The design of the overlay should not hinder post-repair

examinations and evaluations or any pre-service examinations.

• The weld should extend, at full thickness, a minimum di t B i h di ti b d th ff t d b t ldistance B in each direction beyond the affected base metal (unless otherwise justified by a fitness for service assessment).

B = 3/4 (Rtnom)1/2

R = outer radius of the component, or D/2.tnom = nominal wall thickness of the component.


• The edges of the weld overlay should be tapered to the existing pressure component surface at a maximum angle α of 45 degreesangle,α, of 45 degrees.

• The thickness of the overlay should be uniform except for the tapered edges.

• The thickness should be sufficient to maintain the predicted life of the repair.

• All corners of the overlay should have a radius, r, not less than the overlay thickness.e ove y c ess.

• Any corrosion allowance that is determined to be necessary should be added to these dimensions. The predicted maximum degradation of the overlaid pressure component, and the overlay, over the design life of the restoration should be analyzed.

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• In addition, two or more overlays should not be spaced any closer than 3/4 (Rtnom)1/2 between the toe of each overlay.

• The thickness of the completed overlay, W, should not exceed the nominal thickness of the pressure component.

• Configurations not meeting these requirements shall be evaluated based on engineering analysis or testing.

Overlay Qualification Requirements - 1

• Application of weld overlays on straight pipingApplication of weld overlays on straight piping sections and associated welds to correct limited degradation may be considered a pre-qualifieddesign and will be exempt from an engineered design qualification or a proof test qualification if all of the following conditions are met:1 The maximum design temperature does not exceed1. The maximum design temperature does not exceed

340oC (650oF).2. The specified nominal thickness of the existing base

metal is at least Schedule 40 or Standard Wall, whichever is less.

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Overlay Qualification Requirements - 23. The maximum angle of the taper does not exceed 30

degrees (α in Figure 1).4. The finished overlay is circular, oval, full circumferential,

l i hor rectangular in shape.5. For each repair, the maximum dimension (L, length along

pipe axis or C, circumferential width) compensated by a circular, oval, or rectangular overlay does not exceed the lesser of ½ the nominal outside diameter of the pressure component or 200mm (8 inches). A full-circumferential overlay is only limited in the axial dimension, L.

6 Rectangular overlays are aligned parallel with or6. Rectangular overlays are aligned parallel with or perpendicular to the axis of the pressure component, and corners are rounded with radii not less than the overlay thickness.

7. The distance between the toes of adjacent overlays is not less than 3/4 (Rtnom)1/2

Overlay Qualification Requirements - 38. The maximum axial dimension and area of base metal predicted to be below the required thickness over the remaining life of the repair does not exceed that defined by:

L k D kLmax = k1Do + k2Amax = 0.455 Do – k3

Lmax = maximum axial dimension of base metal predicted to degrade below the required thickness over the remaining life of the repair, mm (in.).Amax =maximum area of base metal predicted to degrade below the required thickness over the remaining life of the repair, mm2

(in2)

516mm2 (0.8 –in2) 46.7 mm (1.84-inch)

0.11 DN300 - 600 581 mm2 (0.9 –

in2) 14 mm (0.55 –inch) 0.21 < DN300

k3k2k1Do

(in2).Do = pressure component nominal outside diameter, mm (inches).

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Overlay Qualification Requirements - 4

9. The minimum thickness of the overlay shall be sufficient to restore the nominal wall thickness of the pressure component This can be accomplished by subtracting thecomponent. This can be accomplished by subtracting the remaining thickness from the nominal thickness of the component to obtain the required overlay thickness.

10.If flexibility analysis was required by the original code of construction, the effect of the weld overlay should be reconciled with the original analysis. In this case, for rectangular-shaped overlays on straight pipe, a Stress Intensification Factor (SIF) of 2.1 shall be applied to the

loverlay.• The weld overlay may be qualified by an engineered

design.• As an alternative to the engineered design of weld

overlays, a proof test qualification may be performed through a satisfactory burst test mock-up.

Flaw Excavation

Other

Longitu

Circum

Cra

Lamina

Blisters

Gouge

Pitting

Local w

Genera

(1) Y Y YY Y Y NANA Flaw excavation

udinal cracks


s s

wall thinning

al wall thinning

Y = Generally appropriate. S = Although may be acceptable, is not generally used for this condition. R = May be used, but requires special cautions. N = Not generally appropriate. Note (1): Also applies to the repair of hardened surfaces.

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Flaw Excavation - 2• Material or weld flaws open to the surface

are typically removed by a mechanicalare typically removed by a mechanical (abrasive) method. 1. If the remaining wall thickness of the

excavation, with allowance for future corrosion, is greater than the minimum required wall thickness required by the

t ti t t ti d ( hconstruction or post-construction code (such as the local thin area rules of API 579) the excavated area may be blended to a 3:1 or smoother profile slope, and left as-is for return to service.

Flaw Excavation - 3

2. When the removal of a flaw produces a remaining . W e t e e ova o a aw p oduces a e a gwall thickness below the limit permitted by the construction or post-construction code, including allowance for future corrosion, then the cavity shall be repaired by deposition of weld metal or analyzed for fitness-for-service. – When the depth of material excavated necessitates a

weld repair the cavity shall be prepared for weldingweld repair, the cavity shall be prepared for welding.– Either during or following defect removal, the

excavation shall be shaped to provide adequate access for the welding operation in order to facilitate proper fusion, and avoid slag entrapment, or lack of penetration

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Flaw Excavation - 4• Fabrication - The following steps are generally followed

to excavate a flaw:1. Locate and expose the flaw. Characterize the flaw (size,

depth, orientation) to the extent possible. If the flaw is a crack, the crack tips may be rounded by drilling to preclude crack from propagating during its excavation.

2. Remove the flaw by grinding, machining, honing or thermal gouging. In selecting and applying a removal process refer to the g idance in Sections 2 and 3process, refer to the guidance in Sections 2 and 3..

3. Verify defect removal by inspecting the cavity using visual examination (VT), and liquid penetrant testing (PT), or magnetic particle testing (MT) or eddy current testing (ET) as appropriate.

Grinding Repairs

• Grinding of cracks, arc burns, gouges and grooves is an acceptable method of permanent repair providedan acceptable method of permanent repair, provided the length and depth of metal loss is in accordance with the formula given below.

• For arc burns, confirmation of complete removal of altered metallurgical structures by etching the ground area with a 10% solution of ammonium persulfate orarea with a 10% solution of ammonium persulfate or a 5% solution of nital is recommended.

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Grinding Repairs• Areas to be repaired by grinding shall be thoroughly

cleaned before grinding is initiatedcleaned before grinding is initiated. • Grinding shall be performed to produce a smooth

transition between the surface contour of the repaired area and the surrounding pipe surface.

• External metal loss resulting from grinding to a depth of 40% of the nominal wall thickness of the pipe is

i d id d h h l i di l l h f hpermitted, provided that the longitudinal length of the ground area does not exceed length L as determined by the following formula:

L = 0.441 B1 (Dt)0.5

Grinding RepairsWhereL = maximum allowable longitudinal length of the metal lossL maximum allowable longitudinal length of the metal loss area resulting from a grinding repair, inches.D = nominal outside diameter of pipe, inches.T = nominal wall thickness of pipe, inch.B1= a value equal to 4 for maximum depths up to and including 13% of the nominal wall thickness.= a value determined from the following equation for a value determined from the following equation for maximum depths greater than 13% of the nominal wall thickness up to and including 40% of the of the nominal wall thickness:B1 ={[(c/t)/ (1.1 c/t) – 0.11)] 2 –1} 0.5

c = maximum depth of the ground area, inches.

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Grinding Repairs

• For gouges, grooves and cracks, confirming l t l f th d f t b i dcomplete removal of the defects by using dye

penetrant or magnetic particle inspection and measuring the remaining wall thickness using a mechanical or ultrasonic technique is recommended.

Visual Robotic Welding (VRW)The VRW process allows for free-hand welding in areas inaccessible to a human and where automated welding is not gpossible because of unknown or changing weld conditions. Visual Robotic Welding has been designed for remote internal pipe repair but this technique could be adapted to other situations.

The VRW process combines closed loop control of a specially developed robotic welding arm and an adjacent robotic cameradeveloped robotic welding arm and an adjacent robotic camera arm. Both arms articulate and have the ability to move about five independent axes.

The current prototype is sized to repair pipes from 12 to 24 in. diameter

post construction codes overview of asme pcc-2.pdf

Documents

repair codes

repair examination

repair of shell

repair limitations

weld repair flange

repair of damaged threads

covers repairs

standard covers equipment