Lokring-Coldweld™ fittings — in stainless steel, carbon steel, microalloyed steel, and low temperature carbon steel product lines — are fully qualified to the ANSI/ASME B31 Code for Pressure Piping, covering Power Piping (B31.1), Process Piping (B31.3), Liquid Pipeline Transportation (B31.4), Refrigeration Piping (B31.5), Gas Transmission and Distribution (B31.8), and Building Services Piping (B31.9).
Qualification encompasses the full scope of B31 requirements for nonstandard piping components, including:
- Pressure design: per ASME B31H, Standard Method to Establish Maximum Allowable Pressure for Metallic Piping Components
- Cyclic fatigue design: per ASME B31J, Standard Test Method for Determining Stress Intensification Factors (i-Factors) for Metallic Piping Components
- Fitting design: per ASME Section IX, Welding and Brazing Qualifications for Category D and Normal Fluid Service
- Fitting material: per ASME BPVC Section II
Extensive mechanical and environmental testing across a wide range of pressures, temperatures, and service conditions has consistently confirmed the sealing integrity and mechanical performance of the Lokring ESP® connection.
For engineers specifying Lokring in ASME B31 pressure piping systems, you can download our detailed technical design guide: A Guideline for Designing ASME B31 Pressure Piping Using Lokring™ Fittings with Elastic Strain Preload® (ESP®) Technology.
Pressure-torsion testing
The 1/2″ NPS stainless steel test fitting was subjected to torsional loading high enough to twist the pipe in a spiral without leakage of the joint. Afterwards during hydraulic testing, the pipe ruptured at 22,000 psi (1,497 bar).
Flexural testing
The 2″ NPS carbon steel coupling above has been deflected to 3x the yield strength of the matching pipe without leaking. The performance of this fitting in severe bending, fatigue and vibration loads are comparable or superior to a socket weld fitting.
Fire Testing
The metal-to-metal LOKRING® seal remains intact when subjected to extreme thermal loads, including fire (above). Both stainless and carbon steel LOKRING® fittings are qualified to the Exxon API-607 Rev 4, fire test standards. Stainless steel fittings are also qualified to F1387 (U.S. Navy) fire test standards. Both are widely used on volatile and flammable services.
Are you responsible for designing pressure piping systems according to ASME B31? Contact your authorized LOKRING® distributor for support in designing ASME B31 pressure piping using LOKRING® Elastic Strain Preload (ESP®) fittings.