12 Industrial Pipeline Welding
389
• Transported medium:
Oil and gas with presence of more than 1.5% H 2 S dictates the application of super
clean steel grades free from inclusions. Additionally, high dislocation density
and a very refined microstructure can create hydrogen-induced cracking (HIC)
related failure and is usually tricky to avoid when high strength micro-alloyed
very refined thermo-mechanically controlled rolled steel grades are used for the
pipeline construction.
• Welding conditions:
Melting and instant solidification under unprotected atmosphere redefine the
fusion zone and its surrounding microstructure. Oxidation phenomena related to
the exposure of the melt to the oxygen of the atmosphere lead to oxide penetrators
within the fusion line (weld zone) and limit the pipelines toughness especially in
low temperatures (arctic environment), reeling applications, strain- and stressrelated constructions, and pipeline operation.
In order to meet these challenges, pipeline manufacturers rely on two main factors,
the steel grades to be used and the forming and welding conditions during pipe
construction.
Pipeline steel grades for the next decade (2021–2030) conform to the following
main standards:
• API 5L—Specification of line pipe,
• EN ISO 3183 (PSL 1–3) for steel pipe for pipeline transportation systems and
• DNV-OS-F101 for offshore standard—Submarine pipeline systems.
Steel and pipe need to withstand high stress, strain, and corrosive environments.
Sour service, deep-sea applications with off shore construction methods including
reeling demands in combination with low temperature, and/or service under arctic
conditions set the prerequisites for both steel and pipeline operations in the years
to come. These extreme conditions and the fact that manufacturers need to face the
unknown challenge both industrial pipeline welding and steel manufacturers urge
them to work closely together to match these conditions and to overcome material
and construction limitations.
The next paragraphs elaborate briefly on these conditions.
12.2.2 Sour Service
Process conditions related with oil and gas that contains high levels of hydrogen
sulfide (H 2 S) or sulfuric acid (H 2 SO 4 ) are called sour service. Oil and gas contain
various concentrations of H 2 S [2]. In combination with moisture, atomic hydrogen
(H) is generated, which diffuses easily in the steel matrix. Figure 12.1 illustrates
the adsorption, diffusion, and desorption phenomena resulting in hydrogen-induced
cracking (HIC) initiation and propagation [3]. Interstitial sites, voids, and dislocations
represent trapping sites for atomic hydrogen [3].
389
• Transported medium:
Oil and gas with presence of more than 1.5% H 2 S dictates the application of super
clean steel grades free from inclusions. Additionally, high dislocation density
and a very refined microstructure can create hydrogen-induced cracking (HIC)
related failure and is usually tricky to avoid when high strength micro-alloyed
very refined thermo-mechanically controlled rolled steel grades are used for the
pipeline construction.
• Welding conditions:
Melting and instant solidification under unprotected atmosphere redefine the
fusion zone and its surrounding microstructure. Oxidation phenomena related to
the exposure of the melt to the oxygen of the atmosphere lead to oxide penetrators
within the fusion line (weld zone) and limit the pipelines toughness especially in
low temperatures (arctic environment), reeling applications, strain- and stressrelated constructions, and pipeline operation.
In order to meet these challenges, pipeline manufacturers rely on two main factors,
the steel grades to be used and the forming and welding conditions during pipe
construction.
Pipeline steel grades for the next decade (2021–2030) conform to the following
main standards:
• API 5L—Specification of line pipe,
• EN ISO 3183 (PSL 1–3) for steel pipe for pipeline transportation systems and
• DNV-OS-F101 for offshore standard—Submarine pipeline systems.
Steel and pipe need to withstand high stress, strain, and corrosive environments.
Sour service, deep-sea applications with off shore construction methods including
reeling demands in combination with low temperature, and/or service under arctic
conditions set the prerequisites for both steel and pipeline operations in the years
to come. These extreme conditions and the fact that manufacturers need to face the
unknown challenge both industrial pipeline welding and steel manufacturers urge
them to work closely together to match these conditions and to overcome material
and construction limitations.
The next paragraphs elaborate briefly on these conditions.
12.2.2 Sour Service
Process conditions related with oil and gas that contains high levels of hydrogen
sulfide (H 2 S) or sulfuric acid (H 2 SO 4 ) are called sour service. Oil and gas contain
various concentrations of H 2 S [2]. In combination with moisture, atomic hydrogen
(H) is generated, which diffuses easily in the steel matrix. Figure 12.1 illustrates
the adsorption, diffusion, and desorption phenomena resulting in hydrogen-induced
cracking (HIC) initiation and propagation [3]. Interstitial sites, voids, and dislocations
represent trapping sites for atomic hydrogen [3].