Section 11 Procedures for Nondestructive Testing (NDT)

Quiz – Section 11 Procedures for Nondestructive Testing (NDT)- CWI Part C- 10 Questions

1.

Prior to radiography of any production weld, the radiographic procedure should be established and agreed upon by whom?

 
 
 
 
 

2.

NDT Level III UT personnel:

 
 
 
 
 

3.

Using the ISO 1 9232-1 wire type IQI, the smallest wire required to be visible on the radiograph of a full penetration weld in a pipe having a weld thickness of 0.432 inch is identified by what number?

 
 
 
 
 

4. Using the ASTM E747 wire type IQI, the essential wire diameter required to be visible on the radiograph of a weld in a pipe with a weld thickness of 0.550 inch is:

 
 
 
 
 

5.

What conditions must be considered when using ultrasonic testing on in service welds?

 
 
 
 
 

6.

During radiographic examination of a weld, the image of the essential wire shall:

 
 
 
 
 

7.

Who shall interpret the radiographic images of production welds?

 
 
 
 

8.

When using an ISO wire type IQI, what is the essential wire diameter required to be visible on the radiograph of a pipe weld whose weld thickness is 0.750 inch?

 
 
 
 
 

9.

The procedure to be used for ultrasonic testing must:

 
 
 
 
 

10.

DWE/SWV is an acronym for which of the following ?

 
 
 
 
 


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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.

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Section 6 Qualification of Welders – CWI Part C

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Section 6: Qualification of Welders

6.1 General

The purpose of welder qualification is to prove the welder’s ability to make sound welds using qualified procedures. Welders must qualify by testing before they perform any production welding. A welder who satisfactorily completes a welding procedure qualification test is also qualified as long as all of the test specimens required by subsection 6.5 are successfully tested. These standards also require qualification to be conducted in the presence of a representative acceptable to the company.

The essential variables for welder qualification are different than the essential variables for procedure qualification. The essential variables for welder qualification are listed in paragraphs 6.2.2 and 6.3.2 and will be discussed in detail below.

There are two options for qualifying welders: (1 ) a single qualification and (2) multiple qualifications.
The multiple qualifications qualify the welder for the widest range of variables and is generally preferred.

6.2 Single Qualification

Single qualification requires separate qualification tests for fillet and groove welds. Note that a fillet weld qualification will qualify for welding both socket welds and branch connection welds. However, butt welds do not always qualify the welder to make fillet welds in API 1104.

Paragraph 6.2.1 describes the requirements for the single qualification. In this test, the welder qualifying to make butt welds will make a butt weld in either the fixed or rolled position with the axis of the pipe either horizontal, vertical, or inclined from horizontal at an angle of no more than 45 degrees. The welder qualifying to make branch connections or fillet welds will make a branch or socket connection weld in the position and orientation specified by the welding procedure. The test welds shall meet the requirements of subsection 6.4 (visual examination) and either subsection 6.5 (destructive testing) or 6.6 (nondestructive testing for butt welds only).

Paragraph 6.2.2 is entitled “Scope,” but it really just lists the essential variables for the single qualification of welders. The welder who has completed the single qualification test must requalify if he changes any variables outside the following ranges:

(a) A change in the welding process or combination of welding processes (with the exception that a welder qualified separately for each process used in the combination is also qualified to use the processes in combination).
(b) A change in the direction of welding from uphill to downhill or vice versa.
(c) A change in filler metal classification from Group No. 1 or Group No. 2 to any other group or from any Group No. 9 filler metal to a Group No. 1 or Group No. 2 filler metal. Note that this implies that a welder qualified for SMAW may switch between Group No. 1 electrodes (E601 0, E6011, E701 0, and E701 1 ) and Group No. 2 electrodes (E801 0, E801 1, and E901 0) without having to requalify. However, if a welder qualifies for SMAW using a low-hydrogen electrode (Group No. 3), he must requalify to weld using an E601 0 electrode (Group No. 1 ). In addition, each filler metal classification not listed in Table 1 requires a separate qualification.
(d) A change from one OD group to another (note that OD group was NOT an essential variable for the qualification of welding procedures).
(e) A change from one wall thickness group to another.
(f) A change in position with the following exceptions: a welder who qualifies for fixed (position) welding is also qualified to perform roll welding; a welder who qualifies for making butt welds is also qualified to make lap fillet welds (socket welds), but NOT branch connection welds; a welder who qualifies by making a butt weld in the fixed position at a 45 ° angle is qualified to make butt welds and lap fillet welds (but NOT branch connection welds) in all positions.
(g) A change in the joint design, such as the deletion of a backing strip or a change in edge preparation from a V bevel (i.e. V groove) to a U bevel (i.e. U groove), although this variable is rather
vague.

6.3 Multiple Qualification

Multiple qualifications qualify a welder to weld in all positions, on all wall thicknesses, joint designs, and fittings. However, the widest range of pipe diameters qualified depends on the diameters he welded during the test.

Paragraph 6.3.1 describes the requirements for the multiple qualifications, which require the welder to complete two test weld joints. They are:

(a) A butt weld in the fixed position with the axis of the pipe either horizontal or inclined from horizontal at an angle of no more than 45 degrees. The weld shall be made on pipe with a minimum outside diameter of 6.625 inches and a minimum wall thickness of 0.250 inches. The weld is also required to be welded without a backing strip.

The weld must meet the requirements of API 1 1 04 subsection 6.4 (visual examination) and either subsection 6.5 (destructive testing) or 6.6 (nondestructive testing).

(b) A branch-on-pipe connection weld, for which the welder is required to layout, cut, fit, and weld two pipes of equal diameter together in the form of a T (see Study Guide Figure 5.1 ). The weld shall be made with the axis of the run pipe horizontal and with the branch connection extending vertically down, such that the weld is made in the overhead position.

In addition to the workmanship requirements of paragraph 6.3.1, four nick break specimens shall be removed from the weld as shown in Figure 1 0 and they must also meet the nick break test requirements of subsection 5.8.3.

Paragraph 6.3.2 describes the essential variable rules for multiple qualifications. A welder who successfully completes the butt weld test on pipe 1 2.750 inches in diameter or larger and the branch connection weld on pipes 1 2.750 inch in diameter or larger is qualified to weld in all positions, on all wall thicknesses, joint designs, fittings, and on all pipe diameters. Successful testing on pipes smaller than 1 2.750 inches in diameter qualifies for welding in all positions, on all wall thicknesses, joint designs, fittings, and on all pipe diameters equal to or less than that on which he tested.

A welder holding multiple qualifications shall be required to be requalified if any of the following are changed:

(a) A change from one welding process to another process or combination of processes (aging with the exception that a welder qualified separately for each process used in the combination is also qualified to use the processes in combination).
(b) A change in the direction of welding from uphill to downhill or vice versa.
(c) A change in filler metal classification from Group No. 1 or Group No. 2 to any other group or from any Group No. 3 through 9 to Group No. 1 or Group No. 2. Also, a change in filler metal classification not listed in Table 1 to any other filler metal or vice versa.

6.4 Visual Examination

Visual examination of the test weld must precede any preparation of samples for mechanical testing. If the visual examination reveals cracks, inadequate penetration, burn-through, or unacceptable amounts of undercut, rejection is automatic and another test weld must be prepared. In addition, an inspector may reject the weldment if it does not present a neat, workman-like appearance. Welds made by semiautomatic (e.g. GMAW) or mechanized (e.g. SAW) processes may be rejected if too much filler wire protrudes into the interior of the pipe (sometimes referred to as “bird’s nests” or “whiskers”), although API 1104 offers no definition of what “shall be kept to a minimum” means.“

6.5 Destructive Testing

Paragraph 6.5.1 details the testing requirements for butt weld qualifications. Test specimens shall be cut from the test welds at the locations shown in Figure 1 2 on page 28. The number and type of specimens required are listed in Table 3 on page 30. Figure 1 2, Table 3, and paragraph 6.5.1 should be used together for determining welder qualification test requirements. The test specimen locations are exactly the same as those required for procedure qualification, shown in Figure 3 on page 1 8. The number and type of specimens required for welder qualification, however, are slightly different. Table 3 for welder qualification on page 30 is arranged the same as Table 2 for procedure qualification on page 1 9. The only difference is in the number of specimens required. The similarity of these two tables makes them easy to confuse. Make sure you are referencing the correct table in API 1104: Table 2 on page 1 9 when welding procedures are being qualified and Table 3 on page 30 when welders are being qualified.

Since smaller pipes have less material from which to remove specimens, for pipes less than 2.375 inches in OD, it may be necessary to weld an additional test joint to obtain the required number of test specimens. Furthermore, for pipe 1 .31 5 inches in OD or less, footnote a of Table 3 on page 30 (and Note 2 of Figure 1 2 on page 28 and paragraph 6.5.1 ) provides the option of pulling a single full-section tension test specimen in lieu of performing the required two root bend and nick break tests.

When welders qualify by making butt welds, paragraph 6.5.2 states that the specimens shall be prepared for tensile strength, nick break, and bend tests, as applicable, and the tests shall be performed as described for procedure qualification testing in subsection 5.6. Since the purpose of welder qualification is to determine the welder’s ability to deposit sound weld metal, it is not necessary to determine the tensile strength of the tension test specimens. The tension test may even be omitted, in which case the specimens designated for the tension test shall be subjected to the nick break test.

The tensile strength test requirements for welder qualification are detailed in paragraph 6.5.3. This test is really just a weld metal soundness test. If any of the reduced-section specimens or the full section specimen fails in the weld or at the junction of the weld and the base metal, the fractured surface must meet the soundness requirements of paragraph 5.6.3.3, which is the acceptance criteria for the fractured surface of a nick break specimen. If the specimen fails in the parent material, the weld metal is considered to be acceptable.

Paragraph 6.5.4 gives the requirements for the nick break tests for welder qualification and states that these specimens must meet the same acceptance criteria as those for procedure qualification. See paragraph 5.6.3.3.

The requirements for the bend tests for welder qualification are given in paragraph 6.5.5, which references the same acceptance criteria as those for procedure qualification in paragraphs 5.6.4.3 or 5.6.5.3, as applicable. However, there are two exceptions: Welds in the high-strength pipe may crack or break before they bend to a full U shape. In that case, the specimen is acceptable as long as the exposed surfaces meet the requirements for nick break tests as given in paragraph 5.6.3.3. The other exception is that the company may permit the testing of an additional bend specimen removed from the same test weld to replace a failed bend specimen if, in their opinion, the failure was not representative of the weld. The welder shall be disqualified if this additional specimen fails.

Paragraph 6.5.6 requires that fillet welds be tested using nick break specimens, as shown in Figure 1 0 on page 25. Four specimens shall be removed from locations approximately 90 degrees apart to qualify each welder.

Paragraph 6.5.7 gives the instructions for cutting, preparing, and testing the nick break specimens for welder qualification. When specimens are removed from a complete circumferential test weld, subsection 5.8 and Figures 1 0 and 1 1 on page 25 apply. If the test weld consists of multiple pipe segments (weldments), each segment must supply the same number of specimens. The acceptance criteria for each specimen are given in paragraph 5.8.3.

6.6 Nondestructive Testing (NDT) – Butt Welds Only

At the company’s option, the qualification butt weld may be examined by radiographic testing or automatic ultrasonic testing instead of mechanical testing and meet the requirements in 9.3 or 9.6, respectively. It is not permitted to use NDT methods to purposely locate sound areas or defective areas and subsequently making tests of such areas to qualify or disqualify a welder. Be aware that jurisdictional limitations may override API 1 1 04 and, in doing so, may restrict the use of NDT methods in lieu of mechanical testing for welder qualification.

6.7 Retesting

If a welder fails a test but the company and the welder’s representatives mutually agree that the welder wasn’t at fault, the welder may be given a second chance to qualify. If the welder fails the second time, the welder must submit proof of additional welder training that is acceptable to the company before taking the test for the third time.

6.8 Records

A record that documents the test results for each welder shall be maintained. Furthermore, a list of welders and the procedures for which they are qualified shall also be maintained. If the abilities of a welder come into question, the welder may be required to requalify.

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Section 4: Specifications – CWI Part C

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Section 4: Specifications

4.1 Equipment

This subsection calls for good judgment, sound engineering, suitable operating practices, and attention to safety in the operation of welding equipment. Arc welding equipment shall be operated within the voltage and current ranges specified on the welding procedure specification. Gas welding equipment shall be operated with the fame characteristics and tip sizes given in the qualified WPS.

4.2 Materials

Paragraph 4.2.1 says that pipe and fittings must conform to API or any applicable ASME, ASTM, MSS, or ANSI specifications, but it then further states that materials that comply with the chemical and mechanical properties of any of these specifications are also acceptable, even if they are not manufactured in accordance with the specification. This suggests that the chemical and mechanical properties of any such material must be identified, preferably on the welding procedure specification, when used for an API 1104 application.

Paragraph 4.2.2.1 states that filler metals must conform to one of the listed AWS filler metal specifications. Other filler metals may be used as long as the applicable welding procedures are qualified.

Table 1, in Section 5 on pages 1 5-1 6, divides filler metals into nine groups, based on electrode characteristics and the welding processes that use them. It is important to note that the Group Numbers that API 1104 uses are different than the F-Numbers that AWS uses to group filler metals. For instance, the low-hydrogen SMAW electrodes are F-No. 4 electrodes as defined by AWS, but they are Group No. 3 electrodes in API 1104. Table 1 lists:

(a) Group Numbers for filler metals, electrodes, and fluxes.
(b) AWS Specifications.
(c) AWS Classifications for filler metals and electrodes.
(d) AWS Classifications for fluxes.

Group Nos. 1, 2, and 3 electrodes are for SMAW. Group No. 4 electrodes and fluxes are for SAW. Group No. 5 electrodes are for GMAW, GTAW, and PAW. Group No. 6 electrodes are for OFW and Group Nos. 7, 8, and 9 are for FCAW.

Be attentive to the footnotes in Table 1, which modify the requirements for use of certain electrodes, filler metals, or fluxes and may give additional rules.

Paragraph 4.2.2.2 requires protection of filler metals and fluxes from deterioration and excessive changes in moisture, although no definition of “excessive” is provided. Obviously, if the flux coating on a SMAW electrode is damaged, it should not be used because it will not operate properly. Low hydrogen SMAW electrodes (AWS classifications which end in 5, 6, or 8) must be stored in such a way that their coatings do not absorb excessive moisture from the atmosphere prior to use for welding.

Although it is not specifically required by API 1104, there are recommended good manufacturing practices for the storage and use of low-hydrogen SMAW electrodes in applicable AWS filler metal specifications. These include

(a) The storage of these electrodes in a heated, vented oven at a prescribed temperature after removal from their hermetically sealed containers,

(b) Limited exposure to the atmosphere, and

(c) Recommended minimum baking times and temperatures after atmospheric exposure.

Paragraph 4.2.3.1 addresses the various types of shielding gases used for welding. Inert shielding gases do not react chemically with the weld pool; they work by simply shielding the weld pool from interacting with the gases in the atmosphere. An active gas, however, does interact with either the arc, the weld pool, or in some cases, both. Inert gases include argon and helium. Active gases include carbon dioxide and oxygen. In GMAW, sometimes mixtures of inert and active shielding gases are used.

Gases must be relatively pure and dry and the shielding gas or gases to be used shall be qualified in accordance with the applicable essential variable rules for procedure qualification. API 1104 does not reference AWS A5.32 for purity requirements for shielding gases.

Paragraph 4.2.3.2 addresses storage and handling of gases for welding. Gases shall not be fled intermixed in their containers and gases of questionable purity or gases from damaged containers shall not be used.

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