Analysis and suggestions on welding procedure qual

Analysis and suggestions on welding procedure qualification standards for long-distance pipelines

Abstract: Based on the analysis of ASME b3118 "gas transmission and distribution pipeline system", it is found that the welding procedure qualification in sy/t4103-1995 "welding and acceptance of steel pipelines" does not consider impact toughness, so it is not completely applicable to long-distance pipelines. After comparing the welding procedure qualification standards for pressure pipelines, it is considered that the reference of JB4708 in ASME section IX is comprehensive, scientific and reasonable. If it is incorporated into long-distance pipeline materials, it will comply with the provisions of gb50251 code for design of gas transmission pipeline engineering and be used for welding procedure qualification of long-distance pipeline

key words: long-distance pipeline; Welding procedure qualification

1 preface

the design specifications for long-distance pipelines mainly include gb50251-1994 code for design of gas transmission pipeline engineering and gb50253-1994 code for design of oil transmission pipeline engineering, Using high activity San (acrylonitrile styrene copolymer) in gb5 can improve the above problems. The welding procedure qualification in the current version and revised version (Draft) of 0251 shall comply with gb50236-1998 code for construction and acceptance of industrial pipeline welding engineering of field equipment. In the current edition and revised edition (Draft) of gb50253, JB4708-2000 "welding procedure qualification of steel pressure vessels" is adopted for the welding procedure qualification of pressure vessels, while the welding procedure qualification of pipelines is implemented in accordance with gb50236-1998. However, in the construction of long-distance pipelines, many engineering projects independently implement the welding procedure qualification in sy/t4103

which standard should be implemented for the welding procedure qualification of long-distance pipelines and how to specify the welding procedure qualification of long-distance pipelines are issues to be considered by the design, construction, supervision and owners of long-distance pipelines. Gb50251, gb50253, JB4708 and other standards are facing revision or are about to be revised, so this is also an issue that standard preparers should seriously consider

2 analysis of the differences and characteristics of the three standards

gb50251-94 is compiled with reference to ASME b3118; Gb50253-94 is compiled with reference to ASME b3114 oil transmission and distribution pipeline system; JB4708 and GB50236 are prepared by referring to ASME section IX; Sy/t4103-1995 is equivalent to API std1104 welding of pipelines and related facilities

in ASME b3118 (1999 edition), the regulations on welding procedure qualification and welder qualification are as follows:

(1) for pipes operated under the condition of circumferential stress less than 20% smys (minimum yield strength), only welders are proposed to be evaluated according to ASME section IX, API 1104, or appendix G, and there are no provisions on welding procedure qualification; The welding process and welder for welding under the condition of circumferential stress equal to or greater than 20% smys shall be qualified according to ASME section IX or API 1104

(2) the welding process for offshore pipeline welding and welding under atmospheric pressure shall be qualified according to API 1104 or ansi/AWS a316

(3) the welding procedure qualification and welder qualification of sulfur-containing gas pipeline welding construction shall be in accordance with ASME section IX or API 1104

the welding procedure qualification of gb50251 and gb50253 shall comply with GB50236. JB4708 will replace GB50236 in terms of pressure pipes after revision. However, sy/t4103 is implemented in the actual construction of long-distance pipeline. Then, G Jinmin provides customers with a spray free scheme specially developed for the household appliance industry. What are the differences between b50236, JB4708 and sy/t4103 and their inherent differences? Is very important. The comparison of evaluation factors in these three standards is shown in Table 1 ~ Table 3

Table 1 is a common rule for welding procedure qualification, which is applicable to all kinds of welding methods. There are five common rules: welding methods. After comparing the common rules in Table 1 in detail, it can be seen that the welding methods listed in JB4708 include the welding methods in GB50236 and sy/t4103. There are 53 steel grades in JB4708, which are divided into 8 categories and 15 groups. The substitution relationship is clear, and it can completely contain the steel grouping of sy/t4103. JB4708 divides post weld heat treatment into five categories, and formulates evaluation rules according to temperature and time range. Sy/t4103 does not consider post weld heat treatment. The relationship between specimen thickness and weldment thickness is the key content of welding procedure qualification. JB4708 divides the thickness of the test piece into four cases, and specifies the scope of application for the weldment respectively. In particular, there are eleven kinds of scope of application, while sy/t4103 divides the test piece into three groups, and changing the group requires re evaluation

from table 1 and the above analysis, it can be seen that JB4708 public welding procedure qualification rules can be replaced more scientifically and reasonably, but the prospect is not optimistic, replacing sy/t4103 and GB50236

Table 2 is the detailed rules of welding procedure qualification related to welding methods, in which the welding procedure qualification factors are divided into important factors, supplementary factors and secondary factors. Important factors refer to the welding process factors that affect the tensile strength and bending properties of welded joints. Additive factors refer to welding process factors that affect the impact toughness of welded joints; Secondary factors refer to the welding process factors that have no obvious influence on the properties required to be measured

it can be seen from table 2 that JB4708 has complete important factors, supplementary factors and secondary factors. GB50236 only lists important factors and supplementary factors, while sy/t4103 only lists important factors. It can be seen that JB4708 and GB50236 consider the impact toughness of welded joints, while sy/t4103 does not consider the impact toughness. When the impact toughness test is required in the design drawing of long-distance pipeline engineering, and the welding process evaluation factor of impact test is not considered in the welding construction standard at all, and the impact test is not conducted on the test piece, how to ensure the impact toughness of the long-distance pipeline engineering is worrying

it can also be seen from table 2 that JB4708, GB50236 and sy/t4103 have different evaluation rules: joint form (groove form), welding position and specimen position, shielding gas flow; There are significant differences: upward (downward) vertical welding and upward (downward) welding, interlayer temperature and time interval, linear energy and welding speed; In sy/t4103, there are also filler metals, electrical characteristics and technical measures in which several welding process factors are not included (such as solid wire and flux cored wire, droplet transfer, single wire welding and multi wire welding)

Table 3 shows the comparison of inspection requirements of welding procedure qualification test pieces. JB4708 stipulates that the appearance and internal defects of the test piece are not required to be inspected except for cracks, and the mechanical property samples can be prepared without defects. However, sy/t4103 stipulates that Notch hammer breaking test shall be carried out to check the defects and dimensions on the sample. It is understandable for the welder to inspect the weld section defects of the sample, but it is inappropriate for the welding procedure qualification, which is not the purpose of the welding procedure qualification. JB4708 and GB50236 stipulate that the bending center diameter D is 4 times of the sample thickness a, and the bending is 180 °, while sy/t4103 stipulates that D ≥ 7 A, and the bending is 180 °, and the bending test requirements are obviously not high. Q/syxq4-2001 "code for welding construction and acceptance of west east gas pipeline project" issued by PetroChina west east gas pipeline branch has added the requirement of - 20 ℃ impact test in the test piece inspection, but the welding process qualification factors affecting the impact test and the rigid rules for re evaluating this part of consumer demand have not been clearly put forward in the provisions, which is obviously insufficient

sy/t0452-2002 "welding procedure qualification of oil and gas metal pipelines" issued by the State Economic and Trade Commission is applicable to onshore oil and gas projects. This standard refers to JB4708 and GB50236, which is a step further than sy/t4103 and q/syxq4, clearly puts forward the welding procedure qualification factors and evaluation rules that affect the impact test, and stipulates the requirements of impact test

3 conclusion

(1) welding procedure qualification in ASME b3118, and ASME section IX and api1104 are cited at the same time. However, the execution is conditional. When the impact test requirements are specified, ASME section IX shall be adopted; When there is no impact test requirement, ASME section IX or api1104 shall be adopted

(2) impact toughness is an important performance in the engineering design drawing of long-distance pipeline, which should be guaranteed in the construction specification. Sy/t4103 does not consider impact test, so it cannot be used for the welding procedure qualification of long-distance pipeline with impact test requirements

(3) JB4708 is compiled and revised with reference to ASME section IX, with detailed content, scientific regulations and reasonable substitution, including all the conditions in sy/t4103. When the materials for long-distance pipelines are supplemented, it can be fully used for the welding procedure qualification of long-distance pipelines. (end)