Line Pipe for Sour Service

Line Pipe for Sour Service

The line pipes can be used for a wide range of petrol and gas transportation under sour service environment.

Standards:

• GB/T9711.3
• API5l/ISO3183-2007

Application:

• For petrol and gas transportation under sour service environment.

Sizes range

• 1/4 inch Nominal to 24 inchO.D.
• Wall Thickness-Schedule 10 through XXH

Line Pipe Steels Used in Sour Service

Line pipe steels used in sour service are prone to hydrogen-induced cracking (HIC) depending on metallurgical and environmental factors.
The metallurgical factors consist of alloying elements, microstructure, strength, segregation, and shape of non-metallic inclusions. Some environmental factors which influence HIC, also known as stepwise cracking (SWC), are the partial pressures of hydrogen sulfide (H2S) and carbon dioxide, temperature, pH of the medium, and aggressive ions, such as chloride. Many failures of sour gas line pipes have occurred around the world as a result of HIC.

Considerable effort has been expended by steel line pipe producers, users, and research organizations to understand the HIC mechanism, to develop a laboratory test method to identify and quantify material susceptibility to HIC, and to produce steels with greater HIC resistance. NACE International has developed a standard test, TM-02-84, for line pipe steels.

The method describes procedures for evaluating the resistance of pipeline steels to SWC induced by H absorption from aqueous sulfide corrosion. The test is applicable to line pipe with wall thicknesses of 5 mm to 30 mm. The procedure consists of exposing unstressed coupons to synthetic seawater saturated with H2S at ambient temperature and pressure at a pH in the range 4.8 to 5.4 for 96 h. The samples are sectioned, polished metallographically, and etched, if necessary, so that cracks can be distinguished from small inclusions, laminations, scratches, or discontinuities. Crack sensitivity ratio (CSR), crack length ratio (CLR), and crack thickness ratio (CTR) are calculated for each section. The average is determined for each coupon. In recent work by Canada’s Centre for Mineral and Energy

Technology in collaboration with the Canadian Standards Association (CSA) Sour Service Task Force, two parameters were determined experimentally for each of 19 line pipe steels:
(1) threshold H concentration (CthH) or the concentration of diffusible H in the steel above which cracking occurs and
(2) threshold pH (pHth) or the pH below which cracking occurs.

Chemical composition for pipe with t ≤25,0 mm (0.984 in)

Mass fraction, based upon heat and product analyses

Steel grade	Chemical composition for pipe with t ≤25,0 mm (0.984 in)									Carbon equivalent
	%, Max									% maximum
	C b	Si	Mn b	P	S	V	Nb	Ti	Otherc, d	CEllw	CEpcm
L245NS or BNS	0,14	0,40	1,35	0,020	0,003e	f	f	0,04	g	0,36	0,19 h
L290NS or X42NS	o,14	0,40	1,35	0,020	0,003e	0,05	0,05	0,04	-	0,36	0,19 h
L320NS or X46NS	0,14	0,40	1,40	0,020	0,003e	0,07	0,05	0,04	g	0,38	0,20 h
L360NS or X52NS	0,16	0,45	1,65	0,020	0,003e	0,10	0,05	0,04	g	0,43	0,22 h
L245QS or BQS	0,14	0,40	1,35	0,020	0,003e	0,04	0,04	0,04	-	0,34	0,19 h
L 290QS or X42QS	0,14	0,40	1,35	0,020	0,003e	0,04	0,04	0,04	-	0,34	0,19 h
L320QS or X46QS	0,15	0,45	1,40	0,020	0,003e	0,05	0,05	0,04	-	0,36	0,20 h
L360QS or X52QS	0,16	0,45	1,65	0,020	0,003e	0,07	0,05	0,04	g	0,39	0,20 h
L390QS or X56QS	0,16	0,45	1,65	0,020	0,003e	0,07	0,05	0,04	g	0,40	0,21 h
L415QS or X60QS	0,16	0,45	1,65	0,020	0,003e	0,08	0,05	0,04	g,i,k	0,41	0,22 h
L450QS or X65QS	0,16	0,45	1,65	0,020	0,003e	0,09	0,05	0,06	g,i,k	0,42	0,22 h
L485QS or X70QS	0,16	0,45	1,65	0,020	0,003e	0,09	0,05	0,06	g,i,k	0,42	0,22 h

Note:

a ) Based upon product analysis (see 9.2.4 and 9.2.5) The CE_llw limits apply if the carbon mass fraction is greater than 0,12 % and the CE_pcm limits apply if the carbon mass fraction is less than or equal to 0,12 %.
b ) For each reduction of 0,01 % below the specified maximum for carbon, an increase of 0,05 % above the specified maximum for manganese is permissible, up to a maximum increase of 0,20 %.
c ) AI _total ≤ 0,060 %; N ≤ 0,012 %; AI/N ≥ 2:1 (not applicable to titanium-killed or titanium-treated steel); Cu ≤ 0,35 % (if agreed ,Cu ≤ 0,10 %); Ni ≤ 0,30 %; Cr ≤ 0,30 %; Mo ≤ 0,15 %; B ≤ 0,0005 %.
d ) For welded pipe where calcium is intentionally added, unless otherwise agreed, Ca/s ≥ 1,5 if S < 0,0015 % For SMLS and welded pipes, the calcium concentration shall be ≤ 0,006 %.
e ) The maximum limit for sulfur concentration may be increased to ≤ 0,008 % for SMLS pipe and, if agreed, to ≤ 0,006 % for welded pipe. For such higher-sulfur levels in welded pipe, lower Ca/s ratios may be agreed.
f ) Unless otherwise agreed, the sum of the niobium and vanadium concentrations shall be ≤ 0,06 %.
g ) The sum of the niobium, vanadium and titanium concentrations shall be ≤ 0,15 %.
h ) For SMLS pipe, the listed value may be increased by 0,03.
i ) If agreed, the molybdenum concentration shall be ≤ 0,35 %.
j ) If agreed, the the chromium concentration shall be ≤ 0,45 %.
k ) If agreed, Cr concentration shall be ≤ 0,45 % and Ni concentration shall be ≤ 0,50 %.

Requirements for the results of tensile tests

Pipe steel grade	Yield strength a Rto,5 Mpa (psi)		Tensile strength a Rm Mpa (psi)		Ratio b Rto,5/Rm	Elongation A %
	minimum	maximum	minimum	maximum	maximum	minimum
L245NS or BNS L245QS or BQS	245 (35 500)	450 (65 300)	415 (60 200)	760 (110 200)	0,93	API SPEL 5L
L290NS or X42NS L290QS or X42QS	290 (42 100)	495 (71 800)	415 (60 200)	760 (110 200)	0,93	API SPEL 5L
L320NS or X46NS L320QS or X46QS	320 (46 400)	525 (76 100)	435 (63 100)	760 (110 200)	0,93	API SPEL 5L
L360NS or X52NS L360QS or X52QS	360 (52 200)	530 (76 900)	460 (66 700)	760 (110 200)	0,93	API SPEL 5L
L390QS or X56QS	390 (56 600)	545 (79 000)	490 (71 100)	760 (110 200)	0,93	API SPEL 5L
L415QS or X60QS	415 (60 200)	565 (81 900)	520 (75 400)	760 (110 200)	0,93	API SPEL 5L
L450QS or X65QS	450 (65 300)	600 (87 000)	535 (77 600)	760 (110 200)	0,93	API SPEL 5L
L485QS or X70QS	485 (70 300)	635 (92 100)	570 (82 700)	760 (110 200)	0,93	API SPEL 5L

Requirements for the results of tensile tests

For intermediate grades, the difference between the specified maximum yield strength and the specified minimum yield strength shall be as given in the table for the next higher grade, and the difference between the specified minimum tensile strength and the specified minimum yield strength shall be as given in the table for the next higher grade, For intermediate grades, the tensile strength shall be ≤ 760 MPa (110 200 psi).
This limit applies for pipe with D <323, 9 mm (12.750 in).
For intermediate grades, the specified minimum tensile strength for the weld seam shall be the same value as was determined for the pipe body using footnote a).
For pipe with D