Quiz – Section 11 Procedures for Nondestructive Testing (NDT)- CWI Part C- 10 Questions
Read Carefully and Take a Test
Section 11 Procedures for Nondestructive Testing (NDT)
Written procedures are required for all NDT procedures.
1 1 .1 Radiographic Test Methods
Paragraph 11 .1 .1 addresses requirements for radiographic examination of welds using flam or other media. It describes the flam characteristics (appropriate density, clarity, and contrast) necessary to produce the requisite images. Images produced by other systems shall have the necessary sensitivity to clearly define the essential wire diameter of the proper image quality indicator (IQI ), sometimes referred to as a “penetrometer.”
All image quality requirements apply equally to images produced by x-rays or gamma rays. Paragraph1 1.1.2 reiterates the fact that written procedures are required and refers the reader to paragraphs 11 .1 .2.2 for the details to be addressed in procedures for flam radiography and to paragraph 11 .1 .2.3 for the details to be addressed in procedures for techniques that use other imaging media.
Paragraph 1 1 .1 .3 addresses exposure geometry, which is the relationship between the radiation source, the part being inspected, and the flam or other medium. Three exposure geometries are defined. Single wall exposure/single wall viewing (SWE/SWV) is an exposure where the radiographic source is centered inside the pipe with the flam on the outside of the pipe so that, at all locations on the flam, the radiation goes through a single wall thickness before it reaches and exposes the flam and the flam only shows one wall thickness. When the radiographic source is outside the pipe, but no more than ½ inch from the weld surface and the flam is on the opposite side of the pipe, three exposures separated by 120 degrees are required to examine all 360 degrees of the weld. This is referred to as double wall exposure/ single wall viewing or DWE/SWV, in which radiation passes through two pipe wall thicknesses before it reaches and exposes the flam, but only the flam -side portion of the wall thickness is visible on the flam and can be read for evaluation of the weld. This is also sometimes referred to as a “contact shot.” When the radiographic source is outside the pipe and more than 1 /2 inch from the weld surface, at least four exposures 90 degrees apart are required to examine all 360 degrees of the weld. This is also referred to as DWE/SWV. However, for pipe having diameters of 3-1 /2 inches or less, a double wall exposure/ double wall viewing (DWE/DWV) technique may be used, in which the source is offset from the plane of the weld so that the weld appears as an ellipse on the flam. In this case, two exposures separated by 90 degrees are required, as a minimum, for the evaluation of the full 360 degrees of the weld.
Paragraph 1 1 .1 .4 introduces image quality indicators (IQIs) and gives basic information about their characteristics and use. IQ is shall be either the ASTM E747 wire type or the ISO 1 9232-1 wire type. The wires shall be “radiographically similar” to the pipe and weld material being examined, meaning that they must have the same or very nearly identical density to that of the materials being examined. The company will decide which IQI type is to be used.
The “essential” wire diameter is the smallest wire that must be seen clearly across the area of interest on the flam. Since the wires are placed across the weld, the area of interest is, obviously, the weld. The essential wire diameter is specified, based on weld thickness, in Table 8 on page 58 for ASTM E747 wire-type IQIs and in Table 9 on page 59 for ISO 1, 9232-1 wire-type IQ Is. Note that the essential wire diameter is based on weld thickness, not just nominal wall thickness, so this means that the thickness to be used in these tables is the nominal wall thickness plus weld reinforcement on both the outside and inside of the pipe weld. At the company’s option, smaller wire diameter IQIs may be used, as long as the minimum required sensitivity is obtained.
The details of IQIs to be used are addressed in paragraph 1 1 .1 .5. The ASTM E747 wire-type IQI has six wires while the ISO 1 9232-1 wire-type IQI has seven wires, both of which arrange the wires in order of increasing diameter. These tools are used to ensure the radiographic technique’s minimum sensitivity, which is usually the ability to resolve any indication whose maximum dimension is 2 % of the weld thickness or greater.
The placement of IQIs is described in paragraph 1 1 .1 .6. Wire-type IQIs are typically placed on top of the weld with the wires transverse to the weld. The location (source side vs. film side) is a function of the exposure geometry. When a weld is radiographed in a single exposure with the radiation source inside of the pipe (SWE/SWV), a minimum of four IQIs, equally spaced around the outside of the pipe, is required. For DWE/DWV procedures, a single IQI on the source side of the pipe is required. For DWE/ SWV and SWE/SWV procedures requiring multiple exposures or films to cover all 360 degrees of the weld and where the length of the film to be interpreted exceeds five inches, two IQIs located on the film side are required.
When placing IQIs across the weld is impractical due to weld reinforcement or profile, the IQI may be placed on a separate block of similar material, also called a “shim,” is used to elevate the IQI to a height level with the top of the weld reinforcement.
Paragraph 1 1 .1 .7 limits the interpretation of radiographic images of production welds to Level II or Level III radiographers. Radiographers are required to report all defects to the company unless the company specifically requires all imperfections to be reported. The radiographers shall state whether the welds meet the requirements of Section 9 of API 1104, but the company shall determine the final disposition of the welds.
Paragraph 1 1 .1 .8 requires that lead letters, numbers, or markers be placed on the weldment to identify the radiographic image relative to the weld. This will allow the defects identified on the film to be located on the weld so that repairs can be accurately located.
Improper storage of unexposed film can render it unsuitable for use. Paragraph 1 1 .1 .9 recognizes this hazard and requires an unexposed film to be stored in a clean, dry place and it also explains the characteristics of the damaged film.
All flam must exhibit the same level of quantitative blackening, referred to as “transmitted density,” when exposed to the same intensity of radiation. This transmitted density can be limited by pre-ex postures fog on the unexposed flam. There is a limit to the amount of pre-exposure fog permitted on unexposed flam. For transparent-based flam, the pre-exposure fog cannot exceed 0.30 H & D transmitted density; for opaque-based flam, this pre-exposure fog can be no more than 0.50 H & D reflected density, where “H & D” is the Hurter-Dry Feld method of defining the quantitative blackening of flam.
Paragraph 1 1 .1 .1 0 gives the flam quality requirements for the areas of interest for developed flam. Except for small areas on the flam corresponding to irregular weld configurations, the transmitted H & D density of transparent-based flam shall be between 1 .8 and 4.0, inclusive; the reflected H & D density of opaque-based flam shall be between 0.5 and 1 .5, inclusive. Paragraph 1 1 .1 .1 0.4 states that, when requested by the company, the flam or other imaging media must be processed, handled, and stored so that the images are interpretable for at least three years after they are produced.
1 1 .2 Magnetic Particle Test Method
A procedure for magnetic particle testing (MT) must be written, qualified by demonstration, and accepted by the company prior to use. The MT procedure must comply with ASTM E709, Standard Guide for Magnetic Particle Testing.
1 .3 Liquid Penetrant Test Method
A procedure for liquid penetrant testing (PT) must be written, qualified by demonstration, and accepted by the company prior to use. The PT procedure must comply with ASTM E1 65, Standard Test Method for Liquid Penetrant Examination.
1 1 .4 Ultrasonic Test Methods
A detailed procedure must be developed, qualified by demonstration, and agreed upon by the contractor and company. The use of ultrasonic testing (UT) shall be at the option of the company. The pipe being inspected with UT must be uncoated and the inspector should be aware of surface conditions that can interfere with scanning. Pipe seams should be ground fuse.
Paragraph 1 1 .4.2 describes the elements required to be addressed in the written procedures for ultrasonic testing of welds. This includes calibration requirements.
Paragraph 1 1 .4.3 states that only NDT Level III UT personnel are permitted to develop application techniques and prepare and approve the procedures. However, both Level II and Level III UT personnel are permitted to calibrate equipment and interpret the test results. Similarly, both Level II and III UT personnel are permitted to perform the tests and evaluate the results per the acceptance criteria.
The company has the right to require personnel to demonstrate their ability to perform to the requirements of the procedure as described in paragraph 1 1 .4.4.
Paragraph 1 1 .4.4 requires that the UT procedure, as well as the system/equipment to be used, must be demonstrated and this demonstration must be accepted by the company. This demonstration must also be documented in a report which must address the following:
(a) Welds containing defects and acceptable discontinuities must be prepared from actual production material using a qualified welding procedure.
(b) Radiographs shall be made of the welds and the results documented.
(c) The UT procedure shall be applied to the welds and the results documented and compared with the radiographs.
(d) Differences in detection results shall be documented. Destructive testing will usually be necessary to confirm the results or document discrepancies. This, however, is at the option of the company.
(e) The use of the UT procedure on production welds is then based on the capability of the method/ systems to:
1 ) Circumferentially locate,
2) Size for length,
3) Determine the depth from the OD surface, and
4) Axially locate (across the weld cross-section) the discontinuities/defects in the test welds.
Paragraph 1 1 .4.5 requires the sensitivity of the UT process and equipment to meet minimum requirements. This is accomplished by applying the procedure to known reference standards and specifying the minimum magnitude (screen height) of return echoes produced by standard geometric conditions. The reference block used for this is shown in Figure 27 on page 64. The block must be made by introducing a standard N1 0 notch, as shown in the figure, into a sample of the pipe material to be inspected. The highest point of the distance-amplitude-corrected (DAC) or time-corrected gain (TCG) echo produced by this notch shall not be less than 80 % of the full-screen height on the UT display. Adjusting the equipment to meet this requirement will ensure proper calibration. Requirements for the
sensitivity of the automated UT procedure follows a similar approach, except that fat-bottomed holes must be machined into a sample of the pipe to be inspected, in addition to the N1 0 notches.
Paragraph 1 1 .4.6 requires that parent material be screened for flaws that may interfere with the weld inspection. Before ultrasonic testing of a completed pipe weld is begun, a compression wave test must be conducted on both sides of the weld to locate any refactors in the parent material that may interfere with the weld inspection. Once the parent material is determined to be sound or any refactors in the parent metal are located and documented, the weld may be inspected.
Paragraph 1 1 .4.7 identifies the reference scanning sensitivity and screen height requirements for manual compression wave and the automatic testing of the parent material and the scanning and evaluation sensitivities for the manual and automated testing of welds. Determination of the reference sensitivity for the parent material and inspection of the weld must be performed and documented independently.
Paragraph 1 1 .4.8 requires UT technicians to report only defects unless the company specifically requires that all indications (evaluation level and above) be reported.
Paragraph 1 1 .4.9 specifies that the UT report shall list the weld number, datum location, length, depth from the OD surface, and the defect classification (linear, transverse, or volumetric) for each reported indication.
Section 5 Qualification of Welding Procedures with Filler Metal Additions
5.1 Procedure Qualification
AWS A3.0 defines a welding procedure as “the detailed methods and practices involved in the production of a weldment.” These methods and practices are communicated to the welder in the form of a document referred to as a welding procedure specification. Some codes and standards refer to a welding procedure specification as a “WPS,” but API 1 1 04 does not use that acronym. AWS A3.0 further defines a welding procedure specification as “a document providing the required welding variables for a specific application to assure repeatability by properly trained welders and welding operators.” The welding procedure specification should provide meaningful instructions to the welder for the successful completion of a production weldment.
These definitions set the stage for a detailed discussion of welding procedure qualification, which involves:
(a) Qualifying a welding procedure by testing to prove that welds with suitable mechanical properties can be made by the procedure. (b) Documenting the results of the procedure qualification test. (c) Establishing conditions under which requalification of the welding procedure by testing is required.
Note that Section 5 covers only manual and semi-automatic welding using filler metal additions; mechanized welding with filler metal additions is addressed in Section 1 2, while automatic welding without filler metal additions is addressed in Section 1 3 of the standard.
Subsection 5.2 requires the company to record the complete details of each procedure qualification and to keep that record as long as the welding procedure specification is in use. The record of the procedure qualification is the record of the pipe grade and wall thickness, as well as all of the other required welding variables, used to weld the test coupon; this record also includes the results of the tests (tension, bends, and/or nick breaks) performed. Some codes refer to this document as a procedure qualification record or “PQR,” although API 1 1 04 does not use that term. API 1 1 04 provides sample forms for this purpose. Figure 2 on page 1 1 shows a Sample Coupon Test Report, which can be used to document the results of the procedure qualification test. When the form is used in this manner, the box on the left side of the form, in the middle of the page, labeled “Procedure,” should be checked. This form can be referred to as either a “Coupon Test Report” (“CTR”) or a “Weld Test Report” (“WTR”), although API 1 1 04 does not use these terms.
Figure 1 on page 1 0 is a Sample Welding Procedure Specification Form. The contents of this form are dictated by paragraph 5.3.2 of API 1 1 04.
5.3 Welding Procedure Specification and 5.4 Essential Variables
These subsections list the variables and the ranges thereof required to be specified on a welding procedure specification. Paragraph 5.3.2 describes the variables that must be listed on the welding procedure specification and paragraph 5.4.2 identifies which of those variables are essential variables and the ranges permitted on the welding procedure specification for each of those essential variables.
There are some variables that are listed in paragraph 5.3.2 that are not listed in paragraph 5.4.2. Paragraph 5.4.1 states of those variables, “Changes other than those given in 5.4.2 may be made in the procedure without the need for requalification, provided the welding procedure specification is revised to show the changes.” In other words, the variables that are listed in 5.3.2 that are not listed in 5.4.2 are not essential variables and may be changed by a simple editorial revision of the welding procedure specification. However, in all cases, the welder must ALWAYS weld within the ranges of all of the variables specified in the welding procedure specification.
In the discussion that follows, each variable in 5.3.2 will be described, followed by a reference to the corresponding provision in paragraph 5.4.2 if it is an essential variable. If it is an essential variable, the range qualification rule from 5.4.2 will be explained. Variables listed in 5.3.2 but not listed in 5.4.2 will be so identified. Some codes and standards refer to these types of variables as “nonessential” variables, but API 1 1 04 does not use that term.
18.104.22.168 Process – States the welding process or processes to be used shall be identified and whether they are manual, semiautomatic, mechanized, or automatic.
Paragraph 22.214.171.124 indicates that this is an essential variable.
126.96.36.199 Materials – The materials to which the procedure applies shall be identified by SMYS. The materials may be grouped; but to achieve a “group” qualification, the procedure shall be qualified on the highest SMYS material in that group, resulting in qualification for that SMYS material and all pipe grades below it in that particular group. SMYS groupings are provided in paragraph 188.8.131.52 as follows:
a) SMYS ≤ 42,000 psi. b) 42,000 psi < SMYS < 65,000 psi. c) For pipe having a SMYS of 65,000 psi or greater, each pipe grade shall receive a separate qualification test.
For example, qualification on API 5L Grade X42 pipe would qualify for welding Grades X42, B, A, and X25 pipe. Furthermore, qualification on API 5L Grade X56 pipe would qualify for welding Grades X56, X52, and X46, but not Grade X60 because Grade X60 is a higher SMYS grade than that used for qualification. Qualification on API 5L Grade X70 would only qualify for welding Grade X70 pipe. However, a welding procedure specification for API 5L Grade X70 pipe could be used for welding Grade X70 to Grade X56 pipe (see paragraph 184.108.40.206).
Paragraph 220.127.116.11 indicates that a change in the base material, group, or SMYS, as applicable, is an essential variable.
18.104.22.168 Diameters and Wall Thicknesses – The welding procedure specification shall specify the range of outside diameters (ODs) and wall thicknesses that may be welded.
API 1 1 04 provides suggested groupings for outside diameters and wall thicknesses in paragraphs 6.2.2 d) and e), respectively. The OD groups are:
(a) OD less than 2.375 inches. (b) ODs from 2.375 through 1 2.750 inch. (c) ODs greater than 1 2.750 inches. ` The wall thickness groups are:
(a) Wall thickness less than 0.1 88 (3/1 6) inch. (b) Wall thicknesses from 0.1 88 (3/1 6) inch through 0.750 (3/4) inches. (c) Wall thicknesses greater than 0.750 (3/4) inches.
Paragraph 22.214.171.124 indicates that a change from one specified wall thickness range to another is an essential variable. Outside diameter is not listed in paragraph 5.4.2, so it is not an essential variable.
126.96.36.199 Joint Design – The welding procedure specification must provide a sketch showing the angle of the bevel, the size of the root face, the root opening, as well as the shape and size of fillet welds. If a backing material is used, the type shall be identified.
Paragraph 188.8.131.52 states that a major change in joint design is an essential variable, but a minor change in the angle of the bevel or the size of the root face is not. These definitions are vague, at best.
184.108.40.206 Filler Metal, Flux, and Number of Beads – The size (diameter) and AWS classification number of the filler metal and flux must be identified. In addition, the number and sequence of beads shall be listed.
This means that the welding procedure should be developed by welding a coupon using the smallest number of beads possible; then, as a result, the welding procedure generated can specify a weld schedule having that number of beads or greater.
Paragraph 220.127.116.11 states that a change from one filler metal Group Number in Table 1 to any other Group Number is an essential variable. It is important to restate here that API 1 1 04 uses a different grouping system for electrodes than the F-Numbers used by AWS and the rest of the welding world. API 1 104 uses Group Numbers, which are different than F-Numbers. So a SMAW procedure specification qualified by welding a coupon with an E601 0 electrode could list E601 0, E601 1, E701 0, and/or E701 1 electrodes because these are all Group No. 1 electrodes. However, a SMAW procedure qualified by welding a coupon with an E701 8 electrode could not list E601 0 or E701 0 or E801 0 electrodes because E701 8 electrodes are Group No. 3 electrodes while the E601 0, E701 0, and E801 0 electrodes are Group No. 1 and No. 2 electrodes. For Group No. 1 through Group No. 3, any change in suffix designator is an essential variable. Also, for any filler metal with a G suffix only, a change in the manufacturer or trade name is an essential variable.
Furthermore, paragraph 18.104.22.168 states that, for welding pipe having a SMYS of 65,000 psi or higher, a change in the electrode classification is an essential variable. So, for welding a Grade X70 pipe with SMAW, a change in electrode classification from E801 6 to E801 8 requires requalification, even though the specified minimum ultimate tensile strength of the weld deposits made by these two low-hydrogen electrode classifications is the same.
Also, the general note at the bottom of Table 1 states that electrodes, filler metals, and fixes other than those listed can be used, but each would require a separate qualification. This includes commonly used higher-strength SMAW electrode classifications, such as E901 5 or E1 001 8.
Filler metal size (diameter) is not listed in paragraph 5.4.2 and, therefore, is not an essential variable.
22.214.171.124 Electrical Characteristics – The type of current used shall be identified. Specify either alternating current (AC) or direct current (DC). For DC, the polarity must be identified as well. Either reverse polarity [electrode positive or (EP)] or straight polarity [electrode negative or (EN)] must be listed. A range of voltage and current values must also be specified for each size and type of electrode or filler metal to be used. Typically, the amperage and voltage ranges should provide reasonable flexibility for the welders while being narrow enough to ensure the production of an acceptable weld. The inspector should always verify that these ranges are consistent with the manufacturer’s recommendations.
Paragraph 126.96.36.199 states that a change in current type or polarity is an essential variable. However, changes in the voltage and current ranges are not essential variables.
188.8.131.52 Flame Characteristics – For oxyacetylene welding, designate the type of fame being used. Three options exist. They are:
(a) Carburizing (also referred to as reducing fame), in which an excess of acetylene results in unburned acetylene at the tip of the fame that can deposit carbon on or “carburize” the surface of the base metal. (b) Oxidizing, in which an excess of oxygen results in unburned oxygen at the tip of the fame that can oxidize the surface of the base metal. (c) Neutral, in which there is no unburned acetylene or oxygen at the tip of the fame. Also, the size of the orifice in the torch tip must be specified for each size of rod or wire. The inspector should always verify that tip sizes and gas pressures are within manufacturers’ recommendations.
This variable is not listed in paragraph 5.4.2 and, therefore, is not an essential variable.
184.108.40.206 Position – Designate whether the pipe is rolled or fixed during welding (roll or position welding).
Paragraph 220.127.116.11 states that a change from roll to a fixed position, or vice versa, is an essential variable.
18.104.22.168 Direction of Welding – Designate whether welding is to be performed in the uphill or downhill direction. Sometimes this is referred to as the “progression” of welding.
Paragraph 22.214.171.124 states that a change in the direction of welding is an essential variable.
126.96.36.199 0 Time Between Passes – The maximum time between the end of the root bead and the start of the second bead (hot pass) must be specified as well as the maximum time between the completion of the second bead (hot pass) and the start of other beads.
Paragraph 188.8.131.52 states that an increase in the time between the end of the root bead and the start of the hot pass is an essential variable. If the welding procedure is qualified by welding a coupon in which the hot pass is begun 1 0 minutes after the completion of the root bead, the welding procedure specification should state, “Ten minutes, maximum, permitted between the end of the root bead and the start of the hot pass.” Obviously, it could state a length of time shorter than ten minutes may pass between the end of the root bead and the start of the hot pass, but it could NOT state a period of time longer than ten minutes. This is an ingenious way to control the inter pass temperature for the hot pass, as generated by the root pass, during field welding
The time between the completion of the hot pass and the start of other beads is not listed in paragraph 5.4.2, so this is not an essential variable and, although it is required to be listed on the procedure specification, it may be changed to any value by a simple editorial revision of the procedure specification without requalification by testing.
184.108.40.206 1 Type and Removal of Lineup Clamp – Specify whether a lineup clamp is required, and if so, what type (external or internal) is to be used and how much of the root bead must be deposited before the clamp is released. Typically, a prescribed amount of the joint must be welded before removing the clamp so that the partially welded joint is not subject to undue stress prior to completion of the weld.
This variable is not listed in paragraph 5.4.2 and, therefore, is not an essential variable.
220.127.116.11 2 Cleaning and/or Grinding – Describe whether hand tools or power tools are to be used when cleaning or grinding is necessary. This applies to pre-weld cleaning, inter-pass cleaning, and post-weld cleaning.
This variable is not listed in paragraph 5.4.2 and, therefore, is not an essential variable.
18.104.22.168 3 Preheat and Postweld Heat Treatment (PWHT) – For preheat, specify the minimum required temperature at the start of the weld, the minimum temperature below which preheat is required, and the method of preheating required. For PWHT, specify the temperature range, the time at temperature, the method of heating, and the temperature control methods used to measure the temperature.
Paragraph 22.214.171.124 3 states that a decrease in the minimum preheat temperature is an essential variable. As a result, if a welding procedure is qualified by welding a test coupon at 70 °F, using this welding procedure specification when the temperature outside is 50 °F would require the welder to heat the joint to 70 °F before welding, regardless of pipe grade.
Paragraph 126.96.36.199 4 states that the addition of PWHT or a change in the range of values for the time, temperature, or technique specified in the welding procedure specification are all essential variables.
188.8.131.52 4 Shielding Gas and Flow Rate – The composition of the shielding gas and the range of flow rates permitted shall be specified.
Paragraph 184.108.40.206 0 states that a change in the nominal composition of the shielding gas is an essential variable. In addition, an increase or decrease in the flow rate of more than 20 % of the nominal value is also an essential variable.
220.127.116.11 5 Shielding Flux – The type of shielding flux must be specified. This variable only applies to submerged arc welding (SAW).
Paragraph 18.104.22.168 1 refers the reader to Table 1, footnote a for changes in shielding flux that constitute essential variables. Table 1, footnote a applies to Group No. 4 filler metals, which are those for SAW. This footnote states that any combination of electrode and flux can be used to qualify a welding procedure specification and that the combination is identified by its complete AWS classification, which, by definition in AWS Specifications A5.1 7, specifies both the flux and the electrode. Only substitutions that have the same AWS classification (for both flux and electrode) can be used without requalification.
So, if the welding procedure was qualified by welding a test coupon using a SAW consumable whose AWS classification was F7A0-EL1 2, any flux with the “F7A0” designation could be used with that welding procedure specification, whether it was made by the same manufacturer as that used on the test coupon or not. Conversely, the use of a flux whose AWS classification is different from that used during qualification would require the requalification of the welding procedure by testing.
22.214.171.124 6 Speed of Travel – The range for speed of travel for each pass must be specified on the welding procedure specification, but this range is defined by the range(s) of travel speed(s) used on the test coupon used to qualify the welding procedure.
Paragraph 126.96.36.199 2 states that a change in the range for speed of travel is an essential variable. This means that if the test coupon was welded at 1 0 inches per minute, only 1 0 inches per minute can be specified on the welding procedure specification. Fabricators must realize that test coupons for qualifying welding procedures must be welded using a range of travel speeds to allow a range of travel speeds to be permitted on the welding procedure specification.
188.8.131.52 7 Method of Cooling After Welding – When controlled cooling from the welding operation is used, the welding procedure must specify the method used (e.g., water) and the maximum temperature at which the cooling is applied.
This variable is not listed in paragraph 5.4.2 and, therefore, is not an essential variable.
5.5 Welding of Test Joints – Butt Welds
For qualifying a welding procedure for making butt welds (sometimes referred to as girth or circumferential welds), a butt weld shall be made joining two pieces of pipe. Notice that a butt weld procedure is only qualified for making butt welds. For making fleet or branch connection welds, a separate welding procedure must be qualified.
5.6 Testing of Welded Joints – Butt Welds
Paragraph 5.6.1 gives directions for the preparation of the test coupons. The welded test joint is to be cut into sections, as shown in Figure 3 on page 1 8. Table 2 on page 1 9 gives the number of required specimens. Figure 3 and Table 2 should be used in tandem, along with 5.6.1, for procedure qualification testing requirements.
Figure 3 illustrates the locations from which test specimens shall be removed for procedure qualification testing. It contains four-pipe illustrations, each representing a different range of pipe diameters. Think of each illustration as a clock face. For pipe diameters greater than 4.5 inches, the pipe is big enough that specimens can be removed from four locations approximately 90 degrees apart: at the two, four, eight, and 10 o’clock positions. At each location, arrows outside the pipes indicate the locations where the required specimens shall be taken. For pipes smaller in diameter than 4.5 inches, there is simply not enough room to remove samples from four locations 90 degrees apart, so the illustrations indicate that the specimens should be removed from the two and eight o’clock locations instead. In no case shall the specimens be removed from the area of the pipe containing the longitudinal (long seam) weld. Footnote an of Table 2 and paragraph 5.6.1 identify that for diameters less than 2.375 in. with a wall thickness of 0.500 in. or less, two test welds are required to provide the required number of nick break and root been specimens. The same note of Table 2 and Note 2 of Figure 3 specify that for pipe of 1 .31 5 in. diameter and smaller, one full section tension specimen is tested.
Notice that footnote b of Table 2 states that no tension tests are required for pipes having a SMYS of 42,000 psi or less. For such a low-strength pipe, it is not even necessary to determine the tensile strength of the tested coupon – only nick break tests and bend tests are needed.
One other feature to notice about Table 2 is that side bend tests are required in lieu of face and root bend tests when the wall thickness is greater than 0.500 inches. This is because heavier wall pipes can require significantly more force to bend the specimens in the face and root orientation. For thicker pipe, the use of side bend specimens 1 /2 inch wide by the wall thickness thick (see Figure 9 on page 24) allows the thicker pipe to be more easily tested in a field setting. All welding qualification codes have a thickness above which side bends are permitted in lieu of face and root bends. For ASME Section IX and AWS D1 .1, that thickness is 3/8 inch. For API 1 1 04, that thickness is 1 /2 inches.
Subsection 5.6 discusses these specimens and tests in detail, describing the preparation of the specimens, the test methods, and the acceptance criteria for each. The discussion refers the reader to Figures 4 through 9 on pages 20 through 24.
Tensile strength test requirements are given in paragraph 5.6.2. Tension specimens are approximately 9 inches long by about 1 inch wide. They are required to be full-thickness specimens and they may be made to either one of the two configurations shown in Figure 4 on page 20. Note that weld reinforcement is not removed when testing a specimen prepared according to Figure 4 a). However, Figure 4 b) provides an option of removing a full-thickness specimen with a reduced width section, in which case the removal of weld reinforcement is optional.
The specimens shall be broken in any device capable of measuring the load at which failure occurs
The tensile strength of the weld shall be no less than that specified for the base metal. If the specimen fails in the weld metal, then the fracture surface must also meet the requirements of paragraph 184.108.40.206, which is the criteria for evaluating the fractured surface of a nick break specimen. If the specimen fails in the pipe material and produces a tensile strength not less than 95 % of that specified for the pipe material, the test is acceptable.
Testing of nick break specimens is described in paragraph 5.6.3. The term “nick break” refers to the hacksaw notch or “nick” cut into each edge of each transverse specimen, such that the reduction of the overall cross-section of the specimen helps facilitate the fracture. These specimens are to be approximately 9 inches long by about 1 inch wide and are shown in Figure 5 on page 21. The specimens may be broken by any convenient method, which may include pulling them apart using a tension-testing machine or hitting one end with a hammer while holding the other end.
Figure 6 on page 22 is a schematic of the exposed surface of such a specimen after breaking and it defines the directions in which discontinuity length, depth, and separation are to be measured.
The exposed weld metal surfaces of a nick break specimen must show complete fusion and penetration. The maximum permitted pore size is 1 /1 6 inch and the combined area of all acceptable pores shall not exceed 2 % (1 /50th) of the fractured surface area. Slag inclusions shall not exceed 1 /32 inches in depth and shall not exceed the lesser of 1 /8 inch or one-half the specified wall thickness. There shall be at least 1 /2-inch separation between the edges of adjacent acceptable slag inclusions.
Root and face bend testing is described in paragraph 5.6.4. These specimens are approximately 9 inches long by roughly 1 inch wide and are shown in Figure 7 on page 22. They may be machine or oxygen cut. A maximum corner radius of 1 /8 inches is permitted in order to help prevent corner cracks that could originate from the rough-cut corner rather than from flaws in the weld. In addition, the reinforcement on both the face and root surfaces is required to be removed flush with the surface of the specimen prior to bending in order to maintain smooth and consistent contact with the contour of the plunger. The bend test jig is shown in Figure 8 on page 23, which shows that the radius of the plunger is the same for all pipe grades.
The maximum few sizes permitted on the convex surface of a bent specimen is the lesser of 1 /8 inch or one-half the specified wall thickness. Corner cracks that are less than ¼ inch shall not be considered unless they contain obvious weld-related imperfections. In that case, the maximum 1 /8-inch few sizes apply.
Side bend testing is described in paragraph 5.6.5. The side bend test is similar to the root and face bend tests, except that the specimens are bent such that one side of these transverse specimens becomes the convex surface instead of the face or root surfaces. The specimens are to be approximately 9 inches long by about 1 /2 inches wide and are shown in Figure 9 on page 24. The remainder of the preparation details, the method of testing, and the acceptance criteria are similar to those for face and root bends.
5.7 Welding of Test Joints – Fillet Welds
Figure 1 0 on page 25 illustrates the two options for qualifying fillet weld procedures. One option is a branch connection weld (see Study Guide Figure 5.1 on the previous page), assembling two pipes in the form of a T; the other is a socket-weld configuration (see Study Guide Figure 5.2 below), where the end of one pipe is inserted into the end of a slightly larger pipe to create a lap joint.
5.8 Testing of Welded Joints – Fillet Welds
Paragraph 5.8.1 describes the details of fillet weld testing. Regardless of the test joint configuration selected, qualification of fillet weld procedures requires four nick break specimens to be removed from the welded coupon at 90° intervals (see Figure 1 0 on page 25).
Figure 1 1 on page 25 shows schematics of the nick break specimens. When a branch connection weld is used, two of the four nick break specimens must be removed from the 90° intersection areas, or “crotches,” of the joint (shown in the bottom right corner of page 25) and two must be removed from the tangential area (shown in the bottom left corner of page 25). Due to the large amount of reinforcement that can be present in these welds, the cut edges of all four specimens are subject to fame cut at the weld edge to narrow the specimen width to ensure failure in the weld in addition to the hacksaw cut (nick) made in the weld direction on the weld face. In the nick break specimens removed from the socket weld, no fame cut is used and the hacksaw cut (nick) in the weld is on the sides of the specimen (not the weld face) and is shown in the top right corner of Figure 1 1 on page 25.
The specimens should be about 1 inch wide and long enough that they can be gripped to be broken. As with the butt joints, if the pipe OD is smaller than 2.375 inches, two pipe joints may be needed to obtain the required number of specimens. In this case, two specimens shall be removed from each of the two test welds.
Paragraph 5.8.2 states that the specimens may be broken by any convenient method.
The acceptance criteria for these specimens is given in paragraph 5.8.3 and is exactly the same as that for nick break specimens used to qualify butt weld procedures in paragraph 220.127.116.11.
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