Annex B In-service Welding- CWI Part C

Quiz- Annex B In-service Welding- CWI Part C- 9 Questions

1.

The two main concerns with welding on in-service pipelines are:

 
 
 
 
 

2.

For in-service welds on a full encirclement fitting:

 
 
 
 
 

3.

All welders performing repair work should be familiar with the safety precautions associated with cutting and welding on piping that contains or has contained crude petroleum, petroleum products, or fuel gases. Additional guidance can be found in:

 
 
 
 
 

4.

For the qualification testing of in-service branch and sleeve weld procedures, each macro section test specimen:

 
 
 
 

5.

For in-service welder qualification for longitudinal seam welds on pipe with a 0.375 inch wall thickness, the type and number of test specimens required are:

 
 
 
 
 

6.

For the qualification of in-service fillet weld procedures, specified minimum yield strength (SMYS) is:

 
 
 
 
 

7.

When the maximum allowable heat input to avoid burning through is insufcient to provide adequate protection against hydrogen cracking, an alternative precaution that can be used is:

 
 
 
 
 

8.

When qualifying the welding procedure for in-service welding, the face bend specimens from branch and sleeve welds should not be tested:

 
 
 
 
 

9.

For hydrogen cracking to occur, how many conditions must be satisfied simultaneously?

 
 
 
 
 


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Annex B: In-service Welding

B.1 General

This annex provides welding practices for making repairs to and installing appurtenances on piping systems that are in service. Of particular importance are the welds that melt into the carrier pipe since they cool at an accelerated rate due to the quenching effect of the fluid flowing through the carrier pipe.

The welds that melt into the carrier pipe are either fillet welds or branch connection welds. Fillet welds are used to join the ends of encirclement sleeves to the carrier pipe. These fillet welds are also referred to as “sleeve welds” and “circumferential welds.” Groove welds are used to join split sleeves using longitudinal welds, but these, unlike sleeve welds and branch connection welds, do not melt into the carrier pipe.

Welding attachments onto in-service pipelines pose two major risks: (1 ) burning through the pipe wall and (2) hydrogen cracking. Burning through the pipe wall is unlikely when the wall thickness is 0.250 inches or greater, although many companies successfully weld onto thinner wall pipe with regularity. Although Annex B explains how to prevent both of these problems, the major focus of Annex B is on the prevention of hydrogen cracking.

For hydrogen cracking to occur, three conditions must be satisfied simultaneously:

(1 ) Hydrogen in the weld,

(2) A crack susceptible microstructure, and

(3) Tensile stress acting on the weld. Conversely, to prevent hydrogen cracking, one of these must be reduced or eliminated. Since these welds are made on pipelines that have been in service, hydrogen is always present and cannot be reduced to sufficient levels. In addition, residual tensile stresses are present in every weld due to the inherent shrinkage resulting from solidification and subsequent cooling from high temperatures. As a result, the primary technique used to prevent hydrogen cracking in in-service welds is the prevention of a crack-sensitive microstructure.

To make matters worse, in-service welds are made onto pipe carrying flowing fluids which accelerate the cooling rate and, therefore, promote the formation of crack-sensitive phases in steels, particularly martensite. Because of this combination of factors, the most effective approach for preventing hydrogen cracking in in-service welds is the use of a welding procedure that has a high enough heat input to overcome the quenching effects of the fluids flowing through the carrier pipe. As an alternative, temper bead welding sequences are also effective at producing multi-pass welds in which the heat-affected zone in the carrier pipe has a tempered microstructure, known to be more resistant to
hydrogen cracking.

B.2 Qualification of In-service Welding Procedures

This subsection lists the essential variables and tests required to qualify in-service welding procedures.

Paragraph B.2.1 refers the reader to Section 5 for the basic requirements for qualifying welding procedures for making fillet welds and states that the requirements and exceptions in this annex will then be added to those requirements.

Paragraph B.2.2 lists the additional information required to be addressed on the procedure specification. One of these variables is the carbon equivalent of the carrier pipe to be welded. For determining the carbon equivalent, the following equation is provided:

CEIIW = %C + %Mn/6 + (%Cu + %Ni)/1 5 + (%Cr + %Mo + %V)/5

Also included here is the provision that carbon equivalents may be grouped for the purposes of procedure qualification, as will be discussed shortly.

The pipeline operating conditions must also be addressed on the procedure specification. This can be addressed by specifying the fluid type and its flow rate. Again, conditions may be grouped.

For procedures designed to overcome the quenching effect of the flowing contents by using a sufficiently high heat input, the heat input range should be specified. The minimum value of this range should be that used to weld the procedure qualification coupon. Heat input is given in the Note as Heat Input = Amps x Volts x 60 / Travel Speed.

For procedures designed to overcome the quenching effect of the flowing contents by using a temper bead sequence, the weld deposition sequence, including bead size and overlap, should be specified. The required heat input range for each temper bead layer should also be specified on a temper bead procedure specification.

Paragraph B.2.3 lists additions and changes to the essential variable rules specified in Section 5. For in-service welds, specified minimum yield strength is no longer an essential variable, meaning that in-service welding procedures are valid for all pipe grades. However, since hydrogen cracking is more likely on pipe materials having greater hardenability (as measured by the carbon equivalent), an increase in the carbon equivalent over that used to qualify the procedure is now an essential variable. So, for in-service welds, the MTR of the carrier pipe to be welded should be available so that the carbon equivalent can be calculated from the listed composition. When the in-service welding procedure is qualified, the carrier pipe used in the test coupon should have a carbon equivalent no less than that of the production carrier pipe. Ideally, the carrier pipe used for the qualification test should have a very high carbon equivalent. In that case, the in-service welding procedure would be qualified for a large range of carbon equivalents, up to and including that used in the qualification test weld.

For in-service fillet and branch welds, pipe wall thickness is no longer an essential variable, so these procedures are qualified for all wall thicknesses; however, the note in paragraph B.2.3.1 .3 provides an exception, which states that, for weld deposit repairs, the welding procedure is qualified only for wall thicknesses equal to or greater than that used in the qualification test.

Finally, for in-service welds, pipeline operating conditions are an important essential variable, with an increase in the severity of the conditions being a cause for requalification. So, the procedure should be qualified under the most severe quenching conditions. This can be accomplished by making the test weld on the water canister set up at a 45 ° angle as shown in Figure B.2 on page 1 05. By implication, this variable rule also suggests that the use of a heat input value less than that used to qualify a “heat input the procedure” is also an essential variable and would require the requalification of the procedure. By the same logic, paragraph B.2.3.1 .4 states that, for a temper bead procedure, a change in the deposition sequence or the bead spacing (or overlap) from that qualified is also an essential variable and would require requalification of the procedure.

Paragraph B.2.4 addresses the welding of the test joints and refers to Figure B.2 on page 1 05 showing the carrier pipe coupon filled with flowing water with the sleeve being welded to it using fillet welds or branch connection welds as appropriate. This condition has been shown to produce thermal conditions more severe than typical in-service welding applications. Therefore, a procedure qualified under this condition qualifies for all in-service conditions.

Paragraph B.2.5 addresses the testing of the welded joints. In general, in-service welds that melt into the carrier pipe, including repairs to weld depositions, will be tested using the nick break tests described in subsection 5.8, except that the test locations are shown in Figures B.3 and B.4 on pages 107 and 108, respectively, and the number of specimens required is specified in Table B.1 on page 109. The additional tests required in this table are macro section tests, detailed in paragraph B.2.5.4, and face bend tests, detailed in paragraph B.2.5.5, and both are described below.

Longitudinal seam welds of full-encirclement sleeves should be tested with the tension tests, bend tests, and nick break specimens required in subsection 5.6, as a function of sleeve wall thickness and diameter. Branch and sleeve welds should be tested with the nick break tests in Section 5.8 plus the additional required tests in B.2.5.1.

Paragraph B.2.5.4 gives details about the macro section tests to be removed from the in-service branch and sleeve welds. These are shown schematically in Figure B.5 on page 1 09. They may be machine-cut or oxygen cut oversized.

When they are oxygen cut, the oxygen-cut surface must be machined by a non-thermal process to remove at least ¼ inch from the side to be examined. These weld cross-sections shall then be ground, polished, etched with a suitable etchant, and examined visually without dye penetrants and with little or no magnification (typically at 1 0X or less).

Two of the four micro etch specimens for branch and sleeve welds and both of the specimens for weld deposition repair shall be examined by hardness testing in accordance with ASTM E384. At least five indentations shall be made in the coarse-grained HAZ at the toe of each weld cross-section using a Vickers indenter and a 1 0 kg load to determine the maximum hardness.

Paragraph B.2.5.4.4 gives the requirements for visual examination of each micro etch specimen:

(a) The weld should show complete fusion at the root of the joint.
(b) The weld must be free from cracks.
(c) The legs of the fillet welds must meet the requirements of the procedure specification.
(d) The fillet weld surface (convexity and concavity) must be fat within +/- 1 /1 6 inches.
(e) The undercut depth should not exceed the lesser of 1 /32 inch or 1 2.5% of the pipe wall thickness.
(f) Heat-affected zone (HAZ) hardness values over 350 HV should be evaluated to determine the risk of hydrogen cracking

Paragraph B.2.5.5 describes the face bend specimens that are required. Specific specimens may be cut for these tests or the remaining portion of the nick break specimens can be used. Both options are shown in Figure B.6 on page 110. They may be machine-cut or oxygen cut oversized. When they are oxygen cut, they must be machined by a nonthermal process to remove at least 1 /8 inch from each side. When remnants of the sleeve or branch welds are used, the sleeve and branch welds must be removed to, but not below, the surface of the sleeve. Undercut should not be removed.

Paragraph B.2.5.5.2 addresses the method of bending the specimens. This is identical to the requirements in paragraph 5.6.4.2 except that the specimens shall not be tested sooner than 24 hours after welding.

The acceptance criteria for these bend specimens is exactly the same as that found in paragraph 5.6.4.

B.3 In-service Welder Qualification

Paragraph B.3.1 requires welders performing in-service welding to qualify by making a single qualification test weld in accordance with subsection 6.2 using the specific procedure (heat input or temper bead) used to overcome the quenching effects of the fluid flowing through the pipeline. A welder with only that qualification is qualified for in-service welding in accordance with the essential variable limits of subsection 6.2. However, this annex modifies those qualification ranges as explained in the next few paragraphs.

If that qualification test is welded on pipe less than 1 2.750 inches in OD, the welder is qualified for diameters up to and including the diameter on which he tested. If that qualification test is welded on pipe 1 2.750 inches in OD or larger, the welder is qualified to weld all pipe diameters.

A welder who meets both the multiple qualification requirements of subsection 6.3 and the additional qualification test of this annex is qualified as an in-service branch or sleeve welder in accordance with the essential variable rules of subsection 6.3. Welders who perform weld deposition repairs are limited based on the positions in which they perform the test welds.

Paragraph B.3.2 states that the qualification test required by this annex should be welded on a coupon that simulates the ability of the flowing contents to remove heat from the pipe during welding. Similar to the weld coupon required for the procedure qualification test, falling the carrier pipe with flowing water during welding should produce conditions equal to or more severe than typical in-service conditions.

Welders qualified on such a coupon are therefore qualified for all typical in-service applications. The coupon should also be welded following either the heat input, temper bead, or weld deposition repair welding procedure, as applicable.

Paragraph B.3.3 requires the test coupon to meet the visual inspection requirements of subsection 6.4 and the mechanical testing requirements of subsection 6.5. For longitudinal seam welds in full encirclement sleeves, the type and number of test specimens required for welder qualification are listed in Table B.2 on page 1 1 1.

Paragraph B.3.4 requires that records of these qualifications be maintained.

B.4 Suggested In-service Welding Practices

When making actual in-service welds, the requirements of Section 7 apply, except for the alternative or additional requirements of subsection B.4. Paragraph B.4.1 reminds the reader that safety is the primary concern when welding onto these in-service lines. Factors such as operating pressure, flow conditions, and minimum wall thickness in the area to be welded should be considered. Ultrasonic testing of the pipe wall in the area to be welded is commonly used to determine minimum wall thickness and/or to verify that there are no laminations in the pipe wall that could compromise in-service weld quality or pressure integrity. Additional safety precautions can be found in API’s Recommended Practice 2201.

Paragraph B.4.2 addresses important alignment and ft.-up issues. For saddle and sleeve welds, the gap between the sleeve and the carrier pipe should be minimized to permit easy fusion of the carrier pipe. Weld metal build-up on the carrier pipe is one way to minimize any gap that might be present. Clamping devices are recommended. For longitudinal butt welds of full encirclement sleeves, the root opening should be sufficient to permit full penetration. Use of a mild steel backup strip or suitable tape may be necessary to prevent penetration into the carrier pipe.

Recommended welding sequences, sleeve designs, and geometries are provided in paragraph B.4.3 and shown graphically in Figures B.7 through B.12 on pages 112 through 115. For full encirclement sleeves requiring circumferential fillet welds, the longitudinal seams should be completed before beginning the sleeve welds to minimize the residual stresses on the sleeve welds. When making the circumferential fillet welds, one sleeve weld should be completely welded before beginning the other.

Regardless of the type of fitting used, the welding sequence should always be chosen to minimize residual stresses. Heat input limits and/or temper bead sizes and locations as specified in the welding procedure must be followed.

Paragraph B.4.4 recommends that in-service beads should be deposited in the circumferential direction when possible.

B.5 Inspection and Testing of In-service Welds

In-service welds must meet the acceptance criteria of Section 8 except for the additional or alternative requirements in subsection B.5. Since hydrogen cracking is the primary weld quality concern and most hydrogen cracks are located under the weld bead and do not break the surface, the inspection method must be able to detect under bead and toe cracks. A combination of magnetic particle and ultrasonic testing is recommended for inspecting sleeve-to-saddle and branch-to-carrier pipe welds. Radiographic testing is not a good candidate for detecting these types of cracks.

Since it takes time for hydrogen trapped in the weld to diffuse to the coarse-grained region of the HAZ to cause the cracking, it is important to establish a suitable delay time after welding prior to the inspection to ensure that inspection is conducted after the cracking has had adequate time to develop.

B.6 Standards of Acceptability: NDT (Including Visual)

The standards of acceptability in Section 9 apply to imperfections located in in-service welds. For weld deposition repair, the weld length is defined as the maximum weld length in the direction in which the flaw is oriented.

B.7 Repair and Removal of Defects

The requirements in Section 1 0 apply to the repair and removal of defects found in in-service welds. In addition, care should be taken to ensure that excavation of the defect does not reduce the wall thickness of the pipe to less than that required to contain the pipe’s operating pressure.

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Section 12 Mechanized Welding with Filler Metal Additions

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Section 12: Mechanized Welding with Filler Metal Additions

Section 12 provides the rules for qualifying welding procedures and personnel for mechanized welding with filler metal additions. It further addresses production welding along with inspection and NDT of production welds..

12.1 Acceptable Processes

Mechanized welding shall be performed using one or more of the following processes:

(a) Submerged arc welding (SAW).
(b) Gas metal arc welding (GMAW).
(c) Gas tungsten arc welding (GTAW).
(d) Flux-cored arc welding (FCAW) with or without external shielding gas.
(e) Plasma arc welding (PAW).
(f) Any of the above processes combined with a manual or semiautomatic process.

12.2 Procedure Qualifications

The rules in Section 1 2 are basically identical to those in Section 5 with a few additions and exceptions. Only the differences from Section 5 will be discussed here.

The quality of test welds shall be determined by both destructive testing and non-destructive testing and shall meet the requirements of subsection 5.6, except that nick break tests are not required, and Section 9. The use of nondestructive testing is in addition to the destructive tests required in Section 5.

12.3 Record

Identical to Section 5, this subsection refers the reader to Figures 1 and 2 on pages 1 0 and 1 1 for recommended forms that can be used to document a welding procedure specification and the record of the procedure qualification test coupon, respectively. The record of the procedure qualification must be maintained as long as the welding procedure specification is in use.

2.4 Welding Procedure Specification

Subsection 1 2.4 lists the variables required to be recorded on a welding procedure specification for mechanized welding. The list is the same as that in subsection 5.3, with the following additions and exceptions:

(a) This section does not provide suggested groupings for diameters or wall thicknesses.
(b) Paragraph 1 2.4.2.1 requires the welding procedure specification to include a description of the equipment to be used.
(c) Paragraph 1 2.4.2.4 requires that the welding machine used for each bead be recorded on the welding procedure specification.
(d) Flame characteristics are not listed in subsection 1 2.4 because oxyfuel welding cannot be mechanized.
(e) The minimum percentage of root bead welding that must be completed before a lineup clamp can be removed is not listed in paragraph 1 2.4.2.1 1.
(f) Paragraph 1 2.4.2.1 2 includes the requirements for joint end and inter pass cleaning but does not require that the type of cleaning tools (power or hand) be specified on the welding procedure specification.
(g) Paragraphs 1 2.4.2.1 3 and 1 2.4.2.1 4 require the width of material to be heated during preheating and PWHT to be specified on the welding procedure specification.
(h) Paragraph 1 2.4.2.1 9 requires the welding procedure specification to list any other important factors necessary to produce a good weld and gives examples.

2.5 Essential Variables

Subsection 1 2.5 lists the essential variables for the qualification of welding procedures using mechanized welding processes. This list is essentially the same as that in subsection 5.4 with the following additions and exceptions:

(a) Paragraph 1 2.5.2.3 adds that any change to the root spacing, root face, or angle of bevel to a value not specified on the welding procedure specification is an essential variable.
(b) Paragraph 1 2.5.2.4 adds that any change in wall thickness beyond the range listed in the welding procedure specification is an essential variable.
(c) Paragraph 1 2.5.2.5 adds that any change in specified pipe OD beyond the range listed in the welding procedure specification is an essential variable.
(d) Paragraph 1 2.5.2.7 adds that a change in the size of the filler metal wire is an essential variable.
(e) Change in welding position is NOT an essential variable.
(f) Paragraph 1 2.5.2.1 0 specifies that a change in the range of flow rates established for the shielding gas is an essential variable (whereas subsection 5.4 addresses a specific percentage change).
(g) Paragraph 1 2.5.2.1 6 adds that, for plasma arc welding, any change in the orifice gas nominal composition or change in the orifice diameter is an essential variable.

12.6 Qualifications of Welding Equipment and Operators

This subsection lists the essential variables and the tests required to qualify the welding operators.

Paragraph 1 2.6.1 provides the general rules applicable to welding operator qualification. Similar to Section 6, welding operators shall be qualified by welding a test coupon which shall be tested either by destructive methods or nondestructive methods, or both and shall meet the requirements of subsection 6.4 (visual examination) and either 6.5 (mechanical testing) or 6.6 (radiographic testing), except that nick break tests are not required. When required, tensile strength tests may NOT be omitted in lieu of nick break tests. In addition, welding operators shall be qualified on the type of equipment to be used in production welding.

Paragraph 1 2.6.2 lists the essential variables for welding operator qualification. They are:
(a) A change from one welding process, mode of transfer, polarity, or method of application to another.
(b) A change in the direction of welding from vertical uphill to downhill or vice versa.
(c) A change in the filler metal type (solid wire, metal-cored, flux-cored, etc. ).
(d) A change from one specified OD group to another where the OD groups are defined as:
1 ) OD less than 1 2.75 inches.
2) OD equal to or greater than 1 2.75 inches.
(e) An increase in wall thickness over that welded during the qualification test.
(f) A change in position from that qualified (a change from rolled to fixed or a change from vertical to horizontal). A welding operator who qualifies in the fixed position shall also be qualified to perform welds in the rolled position.

(g) A change in welding bug manufacturer or model.
(h) A change in the method of applying the root bead (e.g., external root versus internal root).
(i) A major change in joint design (e.g. from a V-groove to a U-groove) or any change beyond the range established for root spacing, root face, or angle of the bevel.
(j) At the option of the company, welding operators whose work is limited to specific passes in a multi-pass butt weld may qualify by depositing only those passes in a joint, with other passes necessary to complete the joint being wielded by others.

2.7 Records of Qualified Operators

A record shall be made of the tests and results required by subsection 1 2.6. A form similar to that shown in Figure 2 on page 1 1 should be used, but any form is suitable as long as it records all of the required information. A list of qualified operators and the procedures for which they are qualified shall be maintained. An operator may be required to requalify if a question arises about his competence.

12.8 Inspection and Testing of Production Welds

Production welds shall be inspected and tested in accordance with Section 8.

12.9 Acceptance Standards for NDT

Acceptance criteria for production welds shall be those found in Section 9 or, at the company’s option, Annex A.

12.1 0 Repair and Removal of Defects

Repair and removal of defects shall be in accordance with Section 10.

12.1 1 Radiographic Testing

Radiographic testing procedures shall be in accordance with subsection 1 1 .1.

12.1 2 Ultrasonic Testing

Ultrasonic testing procedures shall be in accordance with subsection 1 1 .4.

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Section 9 Acceptance Standards for NDT – CWI Part C

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Section 9: Acceptance Standards for NDT

9.1 General

This section presents acceptance standards for imperfections found by radiographic, magnetic particle, liquid penetrant, ultrasonic, and visual testing. NDT shall not be used to select welds that are to be destructively tested for welder qualification.

9.2 Rights of Rejection

The acceptance criteria presented in this Section are based primarily on discontinuity length, given the fact that NDT methods, other than ultrasonic testing, can offer no information about a discontinuity’s depth into the weld. For this reason, the company retains the right to reject any weld that meets the limitations specified in this Section if, in their opinion, the depth of any acceptable discontinuity could be detrimental to the weld.

Section 9 defines each discontinuity and, for radiographic testing, clarifies the definition with a figure which shows a schematic. For each discontinuity, this section then provides acceptance criteria, which are typically expressed as both a limit on the size of any single indication as well as a limit on the total length of acceptable discontinuities per weld length. To be acceptable, welds must meet the criteria for each discontinuity as well as for the total accumulated flaws per weld as described in paragraph 9.3.1 2.

Rather than repeat the verbiage in Section 9, this part of the Study Guide will simply point the reader to the applicable paragraphs for the criteria for each discontinuity.

9.3 Radiographic Testing

Paragraph 9.3.1 provides the acceptance criteria for inadequate penetration without high-low, referred to as IP. The schematic is shown in Figure 1 3 on page 35.

Paragraph 9.3.2 provides the acceptance criteria for inadequate penetration due to high-low, referred to as IPD. This condition exists when inadequate penetration is associated with misalignment of the pipe. The schematic is shown in Figure 1 4 on page 36.

Paragraph 9.3.3 provides the acceptance criteria for inadequate cross penetration, referred to as ICP. This discontinuity can only exist in welds made from both the inside and outside of the pipe. A schematic of this is shown in Figure 1 5 on page 36.

Paragraph 9.3.4 provides the acceptance criteria for incomplete fusion, referred to as IF. API 1 1 04’s definition of this limits it to incomplete fusion that is open to the surface. A schematic of this is shown in Figure 1 6 on page 36.

Unlike many other welding standards, API 1 1 04 identifies two categories of incomplete fusion, based on whether it is open to the surface or not. While paragraph 9.3.4 addresses incomplete fusion open to the surface (IF), paragraph 9.3.5 provides criteria for incomplete fusion when it is not open to the surface. This type of incomplete fusion said to be the result of a “cold lap,” is referred to as IFD. A schematic of this is shown in Figure 1 7 on page 37.

Paragraph 9.3.6 provides the acceptance criteria for internal concavity, referred to as IC. A schematic of this is shown in Figure 1 8 on page 37. These criteria are stated in terms of the density of the radiographic image on the radiographic flam. Simply stated, this criterion permits any length of internal concavity as long as the weld thickness is no less than the thinner of the two pipe wall thicknesses being joined. When the minimum wall thickness has been violated, the criteria for burn-through in paragraph 9.3.7 apply instead.

Paragraph 9.3.7 addresses burn-through, referred to as BT. No schematic for this discontinuity is provided. Paragraph 9.3.7.1 defines it and the acceptance criteria are provided for pipe having a specified OD of 2.375 inches and greater in paragraph 9.3.7.2 and for pipe having a specified OD less than 2.375 inches in paragraph 9.3.7.3.

Paragraph 9.3.8 addresses slag inclusions and defines two categories – elongated slag inclusions, referred to as ESIs, and isolated slag inclusions, referred to as ISIs. No schematic is provided for these discontinuities. ESIs are typically linear, separated by approximately the width of the root bead, and usually located between the root bead and the hot pass. ISIs have an irregular shape and may appear anywhere in the weld. The acceptance criteria for slag inclusions are located in paragraph 9.3.8.2 for pipe having a specified OD of 2.375 inches and greater and in paragraph 9.3.8.3 for pipe having a specified OD less than 2.375 inches. The note on page 38 is an exception to the acceptance criteria
and specifies that ESIs separated by approximately the width of the root bead are to be considered a single ESI unless the width of either one exceeds 1 /32 inch, in which case the two indications are to be considered separately as ESIs.

Paragraph 9.3.9 addresses porosity and defines it in paragraph 9.3.9.1. Acceptance criteria are specified based on the types of porosity. Criteria for individual or scattered porosity are given in paragraph 9.3.9.2. Criteria for cluster porosity, referred to as CP, are given in paragraph 9.3.9.3, which only applies to the final or cover (cap) passes. For CP in other than the finish pass, the criteria in 9.3.9.2 apply. Criteria for hollow bead porosity, referred to as HB, are given in paragraph 9.3.9.4.

Paragraph 9.3.1 0 provides the acceptance criteria for cracks. Cracks (previously referred to as ‘C’ ) are prohibited, except for shallow crater cracks or star cracks 5/32 inch in length or less. These cracks are acceptable and it is worth noting that API 1 1 04 is probably the only construction code that explicitly permits cracks of any size. The note at the bottom of this paragraph defines these shallow crater cracks or star cracks as the cracks at the terminations of welds due to shrinkage. These shrinkage cracks are basically solidification cracks that occur when the welding arc is terminated suddenly while the weld puddle surface is still fat. Solidification and further shrinkage cause the weld surface to become concave and pull away from the center, leaving cracks. These cracks, however, can be easily prevented with proper welding techniques.

Paragraph 9.3.1 1 addresses undercutting, which is divided into two categories depending on whether it is on the outside surface of the pipe, referred to as EU, or whether it is on the inside of the pipe, referred to as IU. The acceptance criteria here provide limits for the length of undercut when it is discovered using radiography. However, the depth of undercut is just as important, if not more so, than the length. As a result, the note sends the reader to subsection 9.7 for undercut criteria when the undercut is accessible for visual and mechanical measurement, i.e., accessible for depth measurement. Subsection 9.7 on page 46 sends the reader to Table 4 also on page 46 for the permissible lengths of undercut as a function of depth.

Paragraph 9.3.1 2 provides acceptance criteria for the sum of all acceptable indications in a single weld, referred to as the accumulation of imperfections (previously referred to as ‘AI ’ ). In addition to the acceptance criteria for each individual discontinuity as provided in paragraphs 9.3.1 through 9.3.1 1, the sum of the lengths of all of the different acceptable flaws, excluding IPD, EU, and IU, in any given weld may not exceed the limits given in this paragraph.

Paragraph 9.3.1 3 requires that base metal (pipe or fitting) discontinuities discovered during radiography of the welds be reported to the company for disposition.

9.4 Magnetic Particle Testing

Paragraph 9.4.1 states that not all indications produced by magnetic particle testing (MT) are the result of weld imperfections. The examiner must be able to distinguish between indications produced by magnetic and metallurgical variations and those produced by imperfections. Indications produced by magnetic and metallurgical variations are to be considered nonrelevant. In addition, indications having a maximum dimension of no more than 1 /1 6 inches are also considered to be nonrelevant unless proven otherwise.

After that, all relevant indications are then considered to be the result of weld imperfections and they are divided into two categories, depending on their aspect ratio. Those whose length is more than three times their width are referred to as linear indications. Those having a length three times their width or less are rounded indications.

Paragraph 9.4.2 provides the acceptance criteria for linear indications and refers the reader to paragraphs 9.3.9.2 (individual or scattered porosity) and 9.3.9.3 (cluster porosity) for the acceptance criteria for rounded indications.

Paragraph 9.4.3 addresses flaws found in base material during MT of a weld and requires that these be reported to the company for disposition.

9.5 Liquid Penetrant Testing

The requirements for liquid penetrant testing (PT) are exactly the same as those stated above for MT.

9.6 Ultrasonic Testing

Paragraph 9.6.1 .1 emphasizes that the indications produced by ultrasonic testing (UT) are not necessarily defects. The difference between relevant indications, which are those that result from weld imperfections, and nonrelevant indications, which are the result of changes in the weld geometry, reinforcement profiles, internal chamfering, or other geometric issues must be understood.

Paragraph 9.6.1 .2 classifies relevant indications as linear when their longest dimension is parallel to the direction of welding.

Paragraph 9.6.1 .3 classifies relevant indications as transverse when their longest dimension is across
the direction of welding.

Paragraph 9.6.1 .4 classifies three-dimensional indications as volumetric.

Paragraph 9.6.2 provides acceptance criteria for indications found by UT based on the definitions in the following paragraphs:

(a) 9.6.2.2 for linear surface (LS) indications.
(b) 9.6.2.3 for linear buried (LB) indications.
(c) 9.6.2.4 for transverse (T) indications.
(d) 9.6.2.5 for volumetric cluster (VC) indications.
(e) 9.6.2.6 for volumetric individual (VI ) indications.
(f) 9.6.2.7 for volumetric root (VR) indications and.
(g) 9.6.2.8 for the accumulation of relevant indications.

Paragraph 9.6.3 addresses imperfections in the base metal found during UT of welds and, similar to RT, MT, and PT, requires disposition of these flaws by the company.

9.7 Visual Acceptance Standards for Undercutting

Paragraph 9.7.1 reminds the reader that these criteria supplement, but do not replace, VT acceptance criteria found elsewhere in the Standard.

Paragraph 9.7.2 refers the reader to Table 4 on page 46 for acceptance criteria for undercut when visual and mechanical means can be used to determine depth. The table states, for instance, that there is no limit on the length of undercut in a weld if it is no deeper than the lesser of 1 /64 inch or 6 % of the wall thickness. As undercut becomes deeper, the length permitted decreases.

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Section 7 Design and Preparation of a Joint for Production Welding – CWI Part C

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Section 7: Design and Preparation of a Joint for Production Welding

The purpose of Section 7 is to establish requirements for production welding.

7.1 General

Production welding shall be performed only by qualified welders using qualified welding procedures. This paragraph identifies the cleanliness requirements for the surfaces to be welded. Further, any base material or handling conditions (e.g. lamination, tears, etc.) that might adversely affect welding are prohibited.

7.2 Alignment

Ideally, the abutting ends of adjoining pipe lengths should align with little or no axial misalignment. In practice, this is unlikely, so API 1 1 04 suggests a maximum of no more than 1 /8 inch of offset (high-low) between adjoining pipe lengths of the same wall thickness. Larger variations are acceptable if the pipe meets the ovality (maximum and minimum diameter) requirements in the applicable material (or purchase) specifications and the offset is distributed evenly around the outside of the joint. API 1 1 04 suggests that hammering on pipes to obtain proper lineup be kept to a minimum.

7.3 Use of Lineup Clamp for Butt Welds

In production and fabrication, the use of a clamping device or fixture is a common practice to help bring adjoining pipe lengths into proper alignment. If external clamps are to be removed before completion of the root bead, at least half of the root bead must be in place, uniformly distributed around the joint. If internal clamps are to be used and removing them before completion of the root bead would permit movement of the pipe or result in undue stress on the unfilled joint, the internal clamps shall remain until the root pass is completed. When it is permissible to remove any clamp prior to the completion of the root bead, the completed portions of the root bead must be in approximately equal segments spaced approximately evenly around the joint.

7.4 Bevel

Bevels placed on pipe ends by the pipe manufacturer, referred to as “mill bevels,” must meet the requirements of the welding procedure specification. Pipe ends may be beveled in the field by any machine tool or machine oxygen cutting. The company, however, must approve the use of manual oxygen cutting. The dimensions of these manual bevels must also conform to those specified in the applicable welding procedure specification.

7.5 Weather Conditions

Welding shall not be done when the weather conditions, such as airborne moisture, winds, or blowing sands, pose a significant threat to the quality of the completed weld. Responsibility for determining how or whether to conduct welding operations lies with the company.

7.6 Clearance

For pipe welded above ground, the working clearance around the joint should be at least 1 6 inches in all directions. For pipe welded in a trench, the cavity beneath the pipe, sometimes referred to as the “bell hole,” shall be large enough to give the welder or welders adequate working space, but no minimum dimension is specified.

7.7 Cleaning Between Beads

Slag and scale shall be removed from each pass in a multi-pass weld using tools as specified in the welding procedure specification. High spots in beads deposited by semiautomatic or mechanized welding processes shall be removed by grinding to prevent contact between the filler metal and/or electrode and the weld deposit during welding. In addition, surface porosity clusters and bead starts shall be removed by grinding on semiautomatic and mechanized welds.

This requirement to remove slag from weld beads does not address the black “glass deposits” sometimes seen at the ripples of carbon steel weld beads deposited with GMAW. These deposits are black silicon oxide deposits whose black color comes from the manganese and iron in the base metal. Since they do not come from the flux used in flux-shielded processes, they are technically not slag. As a result, these are only required to be removed when specifically requested by the company.

7.8 Position Welding and 7.9 Roll Welding

For position (or “fixed”) welding, the pipes shall be secured against movement and the welders shall have adequate space to work. At the company’s option, roll welding may be used, provided the pipe is adequately supported to prevent sag.

API 1104 has established a target weld profile for all pipe welds, regardless of whether they are welded in the fixed or rolled position. Face reinforcement should be no more than 1 /1 6 inches and the face of the completed weld should be about 1 /8 inches wider than the width of the original groove. Note that this profile is a target, not a requirement. It is commonly referred to as “nickel-wide and dime-high.” In no case, however, shall the crown surface of the weld fall below the outside surface of the pipe. For both position and roll welding, the number of filler and finish ends shall allow the completed weld a substantially uniform cross-section around the entire circumference

In position welding, two beads shall not be started in the same location. Instead, the starts and stops of a multiphase weld should be located so that they do not coincide to avoid the creation of high-stress areas by multiplying the residual stresses associated with weld terminations. This applies to welds made in the fixed position, but not those made by roll welding.

7.1 0 Identification of Welds

Each welder shall identify his welds in a manner prescribed by the company.

7.1 1 Preheat and PWHT

Preheat and PWHT shall be conducted as specified by the welding procedure specification.

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