API 5L PSL1 vs PSL2

Quick Answer

PSL2 is the stricter level of API 5L, requiring maximum yield/tensile limits, mandatory Charpy impact testing, tighter carbon equivalent limits, and traceable mill certificates (EN 10204 3.1/3.2). PSL1 specifies minimum requirements only and is used for less critical services.

API 5L defines two Product Specification Levels for line pipe. PSL1 covers basic quality requirements suitable for standard pipeline service. PSL2 adds enhanced requirements for critical or high-consequence pipelines, including offshore, sour service, and high-pressure transmission.

Comparison Table

Requirement	PSL1	PSL2
Yield strength	Minimum only	Minimum and maximum
Tensile strength	Minimum only	Minimum and maximum
Y/T ratio	Not specified	Max 0.93 (grades ≥ X42)
Elongation	Minimum required	Minimum required (stricter)
Charpy impact test	Not required	Mandatory (pipe body and weld)
Carbon equivalent (CE)	Not specified	Maximum limits per grade
Carbon (max), Gr. B	0.28%	0.24%
Sulfur (max)	0.030%	0.015%
Phosphorus (max)	0.030%	0.025%
Traceability	Lot-based	Heat-based
Mill certificate	Not mandated	EN 10204 3.1 or 3.2
NDT	Per standard	Per standard + stricter acceptance
Sour service (Annex H)	Not available	Optional annex
Fracture toughness	Not specified	CVN at design temperature
Repair welding	Allowed	Restricted

Why PSL2 Matters

The maximum yield and tensile limits in PSL2 control the yield-to-tensile (Y/T) ratio. A Y/T ratio above 0.93 indicates limited strain hardening capacity, which can be dangerous in pipelines subject to ground movement, thermal cycling, or seismic loads. PSL1 does not control this.

The mandatory carbon equivalent limit ensures weldability in the field without excessive preheat. Lower sulfur and phosphorus limits in PSL2 reduce the risk of hot cracking and improve fracture toughness.

When to Specify PSL1

• Low-pressure gathering lines and flow lines
• Non-critical water distribution pipelines
• Temporary or short-service-life pipelines
• Applications where cost is the primary driver and consequences of failure are low

When PSL2 Is Required

• Cross-country oil and gas transmission pipelines
• Offshore and subsea pipelines (DNV-OS-F101 mandates PSL2)
• Sour service pipelines (Annex H requirements for HIC/SSC testing)
• High-pressure gas transmission systems per ASME B31.8
• Any pipeline in a High Consequence Area (HCA) under regulatory codes

Common Mistake

Specifying PSL1 for sour service. Annex H (sour service supplementary requirements) is only available under PSL2. If H2S is present, PSL1 is not an option. Check the NACE MR0175/ISO 15156 requirements early in the design phase.

Cost Difference

PSL2 pipe costs 5-15% more than PSL1 for the same grade and size due to tighter chemistry control, additional testing, and lower mill yield (more rejections). The premium is justified by improved reliability and mandatory quality assurance.

For detailed API 5L grade properties and applications, see the full specification guide.

Read the full guide to pipe types