The role of ERW pipe in gas pipeline

ERW (Electric Resistance Welded) pipes are widely used in gas pipelines, mainly because they are efficient, economical and can meet the safety and technical requirements of gas transportation. The following are the specific roles, performance characteristics and advantages of ERW pipes in gas pipelines:

The core role of ERW pipes:

Gas transportation carrier:
As the core material of the main line, branch line or household pipeline, it safely transports natural gas, liquefied petroleum gas (LPG) and other gas media.

Pressure adaptability:

It can withstand the pressure of medium and low pressure gas systems (usually ≤4.0MPa) and meet the needs of urban pipelines, industrial users and other scenarios.

Why do gas pipelines prefer ERW pipes?

(1) Economic and efficiency advantages
Low production cost: ERW welded pipes are welded by coil forming. Compared with seamless pipes (piercing and rolling are required), ERW welded pipes have high production efficiency, which can reduce the waste of raw materials and reduce production costs (the price is usually 20%~30% lower than seamless pipes).

Scaled production: Continuous production lines can achieve high-speed welding (speeds can reach 20~100 meters/minute), which is suitable for large-scale demand for urban gas pipelines and shortens project cycles. Suitable for large-scale procurement of long-distance gas pipelines and shortens construction periods.

Mature technology and reliable quality: High-frequency welding (HFW) technology has advanced. Modern ERW technology heats the welding edge through high-frequency current. The weld has no filler and a narrow heat-affected zone. The strength can reach 90%~95% of the parent material, and non-destructive testing (UT/RT) is used to ensure that there are no defects.

(2) Performance meets gas demand

a. Pressure matching: Urban gas pipelines are mostly medium and low pressure systems (≤4.0MPa), and the pressure bearing capacity of ERW welded pipes fully meets the requirements (such as GB/T 3091 covers PN1.6MPa, API 5L PSL1 covers Class 150). However, in high-pressure scenarios (such as long-distance pipelines >10MPa), seamless pipes or LSAW pipes are still required.

b. Flexible diameter: ERW pipes can be produced in common diameters of DN15~DN600, covering the needs of household branch lines (DN20~DN50) and trunk pipelines (DN100~DN400).

c. Reliable strength: Low-alloy high-strength steel (such as L245, L290) is used, and residual stress is eliminated through cold expansion process, and the strength is close to that of seamless pipes.

d. Good sealing: Modern ERW processes (such as high-frequency welding) have no filler in the welds, a narrow heat-affected zone, and eddy current testing (ECT) is used to ensure no leakage.
e. Corrosion resistance: It can be matched with anti-corrosion coating (such as 3PE anti-corrosion layer) or galvanized to resist trace corrosive media in soil and gas.

(3) Standard compliance
Comply with gas-specific standards:
National standard (GB/T 3091-2015 "Welded steel pipe for low pressure fluid transportation")
American standard (API 5L "Pipeline Steel Pipe Specification")
European standard (EN 10217-1)

Key technical requirements for ERW pipes for gas:

Material selection:
Mainly carbon steel (Q235B, L245), sulfur content must be ≤0.02% (to prevent hydrogen-induced cracking).
Low-temperature toughness steel (such as L290N) is required in cold areas.

Weld quality control:
100% non-destructive testing (UT/RT) to ensure that there are no defects such as unfused and pores.
The weld excess height needs to be smoothed to reduce flow resistance.

Anti-corrosion treatment:
External anti-corrosion: 3PE (three-layer polyethylene), FBE (fusion-bonded epoxy powder) coating.
Internal anti-corrosion: epoxy resin coating (anti-corrosion of gas impurities).

4. Typical applications of ERW pipes in gas systems
Urban medium-pressure pipeline network: DN100-DN600 ERW pipes are the main transmission lines.
Branch lines for industrial and commercial users: DN50-DN200 pipelines, connecting the pressure regulating station and the terminal.
Household pipelines: small-diameter (DN15-DN40) ERW pipes, which must meet the requirements of thin-walled and lightweight.

5. Precautions
1) Prohibited use scenarios
When high-pressure gas (such as gate station outlet > 4.0MPa) or acidic gas containing hydrogen sulfide is used, the applicability of ERW pipes needs to be evaluated.

2) Installation points
Welding should be carried out with inert gas shielded welding (such as TIG) to avoid weld oxidation.
Sacrificial anode protection is required when laying underground to extend the service life.

3) Common market problems

Beware of non-standard ERW pipes (insufficient wall thickness, material adulteration), and a third-party test report (such as CMA certification) must be requested.

Conclusion:
ERW pipe has become the first choice for medium and low pressure gas pipelines due to its cost-effectiveness, mature technology and reliable performance. However, under special working conditions such as high pressure and strong corrosion, it is necessary to combine seamless pipes or LSAW pipe (straight seam submerged arc welded pipes) for comprehensive selection. When purchasing, it is necessary to strictly control the materials, weld quality and anti-corrosion standards to ensure the safety of gas transportation.

Read more: SAW vs ERW and EFW Welded Steel Pipe or API 5L ERW Line Pipe Standard & Grade