Hollow-Section Structural Pipes For Underground Natural Gas Lines

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When constructing underground natural gas pipelines, material selection is critical to ensuring the safety and efficiency of the infrastructure. Hollow section structural tubes, especially spiral submerged arc tubes, are becoming increasingly popular due to their superior strength, durability and corrosion resistance. In this blog, we will explore the importance of hollow-section structural pipes in the construction of underground natural gas pipelines and the key advantages they offer.

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Spiral submerged arc pipes are widely used in the construction of underground natural gas lines due to their unique manufacturing process. The pipes are formed by forming coils of hot-rolled steel into a spiral shape and then welding them using a submerged arc welding process. This produces high-strength Spiral submerged arc pipes with uniform thickness and excellent dimensional accuracy, making them ideal for underground natural gas transportation.

Table 2 Main Physical and Chemical Properties of Steel Pipes (GB/T3091-2008, GB/T9711-2011 and API Spec 5L)
Standard	Steel Grade	Chemical Constituents (%)						Tensile Property						Charpy(V notch)Impact Test
		c	Mn	p	s	Si	Other	Yield Strength（Mpa）		Tensile Strength（Mpa）		（L0=5.65 √ S0 ）min Stretch Rate （%）
		max	max	max	max	max	Other	min	max	min	max	D ≤ 168.33mm	D ＞ 168.3mm
GB/T3091 -2008	Q215A	≤ 0.15	0.25 ＜ 1.20	0.045	0.050	0.35	Adding Nb\V\Ti in accordance with GB/T1591-94	215		335		15	> 31
	Q215B	≤ 0.15	0.25-0.55	0.045	0.045	0.035		215		335		15	> 31
	Q235A	≤ 0.22	0.30 ＜ 0.65	0.045	0.050	0.035		235		375		15	>26
	Q235B	≤ 0.20	0.30 ≤ 1.80	0.045	0.045	0.035		235		375		15	>26
	Q295A	0.16	0.80-1.50	0.045	0.045	0.55		295		390		13	>23
	Q295B	0.16	0.80-1.50	0.045	0.040	0.55		295		390		13	>23
	Q345A	0.20	1.00-1.60	0.045	0.045	0.55		345		510		13	>21
	Q345B	0.20	1.00-1.60	0.045	0.040	0.55		345		510		13	>21
GB/T9711-2011（PSL1）	L175	0.21	0.60	0.030	0.030		Optional adding one of Nb\V\Ti elements or any combination of them	175		310		27		One or two of the toughness index of impact energy and shearing area may be chosen. For L555, see the standard.
	L210	0.22	0.90	0.030	0.030			210		335		25
	L245	0.26	1.20	0.030	0.030			245		415		21
	L290	0.26	1.30	0.030	0.030			290		415		21
	L320	0.26	1.40	0.030	0.030			320		435		20
	L360	0.26	1.40	0.030	0.030			360		460		19
	L390	0.26	1.40	0.030	0.030			390		390		18
	L415	0.26	1.40	0.030	0.030			415		520		17
	L450	0.26	1.45	0.030	0.030			450		535		17
	L485	0.26	1.65	0.030	0.030			485		570		16
API 5L （PSL 1）	A25	0.21	0.60	0.030	0.030		For grade B steel,Nb+V ≤ 0.03%;for steel ≥ grade B,optional adding Nb or V or their combination, and Nb+V+Ti ≤ 0.15%	172		310		（L0=50.8mm）to be calculated according to the following formula:e=1944·A0 .2/U0 .0 A:Area of sample in mm2 U: Minimal specified tensile strength in Mpa		None or any or both of the impact energy and the shearing area is required as toughness criterion.
	A	0.22	0.90	0.030	0.030			207		331
	B	0.26	1.20	0.030	0.030			241		414
	X42	0.26	1.30	0.030	0.030			290		414
	X46	0.26	1.40	0.030	0.030			317		434
	X52	0.26	1.40	0.030	0.030			359		455
	X56	0.26	1.40	0.030	0.030			386		490
	X60	0.26	1.40	0.030	0.030			414		517
	X65	0.26	1.45	0.030	0.030			448		531
	X70	0.26	1.65	0.030	0.030			483		565

One of the main advantages of hollow-section structural pipes is their excellent corrosion resistance. When buried underground, natural gas pipelines are exposed to moisture, soil chemicals and other corrosive elements. Spiral submerged arc pipes are specifically designed to withstand these harsh underground conditions, ensuring the longevity and reliability of natural gas pipelines.

In addition to corrosion resistance, hollow-section structural pipes offer superior strength and stability, making them suitable for underground installations. The spiral design of these pipes provides excellent load-bearing capacity, allowing them to withstand the weight of soil and other external forces without compromising their structural integrity. This is particularly important in areas with challenging geology, where pipelines must be able to withstand ground movement and settlement.

Additionally, hollow section structural pipes are known for their versatility and cost-effectiveness. They come in a wide range of sizes and thicknesses and can be customized to meet the specific requirements of underground natural gas pipeline projects. This in turn reduces the need for additional fittings and welding, resulting in faster installation and lower overall costs. The lightweight nature of these pipes also makes transportation and handling more efficient, further contributing to cost savings.

When it comes to the safety and efficiency of underground natural gas lines, material selection is critical. Hollow-section structural pipes, especially spiral submerged arc pipes, combine strength, durability, corrosion resistance and cost-effectiveness, making them ideal for underground natural gas transmission. By investing in high-quality pipelines designed specifically for underground facilities, gas companies can ensure the reliability and longevity of their infrastructure while minimizing maintenance and repair costs in the long term.

In summary, hollow cross-section structural pipes play a vital role in the construction of underground natural gas lines. Its superior corrosion resistance, superior strength and cost-effectiveness make it the first choice for natural gas transportation projects. By choosing the right materials for underground facilities, natural gas companies can maintain the safety and reliability of their infrastructure, ultimately helping to deliver natural gas efficiently to consumers.