Lokring Pipe Joining Systems


What is Lokring?

Lokring is a mechanical method for producing permanent weld equivalent pipe connections, eliminating the need for hotwork and the associated health and safety issues.
Lokring are patented fittings, they are permanently join small diameter nominal pipe size (1/4 thru 3) and tube (1/4" thru 2") without threading or welding.

Following insertion of the pipe or tube end into the fitting, hydraulic tooling is used to advance each swage ring axially over the fitting body, radially compressing (swaging) the fitting body on to the outside diameter of the pipe or tube.

Patented Elastic Strain Preload (ESP®) technology

The leak-free seal is the result of LOKRING's ESP installation where the axial movement of the LOKRING driver over the body swages the body onto the pipe's surface. This compresses the pipe wall first elastically and then plastically.

The pipe wall resists this swaging action, generating high unit compressive loads at the contact points between narrow sealing lands inside the fitting body and the pipe surface.
These contact stresses are sufficiently high to plastically yield the tube surface under the sealing lands, forming a 360° circumferential, permanent, metal-to-metal seal between the pipe and fitting body. The driver, which experiences a small increase in diameter (elastic strain) during installation, exerts an elastic, radial pre-load on the metallic seals for the use of the connection.

Lokring Technology LLC


Lokring approvals

LOKRING meets or exceeds the following technical specifications, standards and approvals..

American Bureau of Shipping (ABS)

  • Manufacturing Assessment Certification 2017
  • Stainless Steel (SS)
  • Copper Nickel (CN)
  • Carbon Steel (MAS)
  • Low Temperature Carbon Steel (LTCS)

American Petroleum Institute – API-607 Rev 4 Fire Test

ANSI/ASME B31.1, B31.3, B31.4, B31.5, B31.8, and B31.9

  • LOKRING Fitting Application Guide
  • LOKRING Pressure Piping Design Guide


Association of American Railroads (AAR)

British Ministry of Defence

California Air resource(s) Board (CARB)

Canadian Registration Number (CRN) • OA1195

Canadian Standards Association (CSA) Z7396 1-09

DNV TA – Product Type Approval for elastic strain preload (ESP ™ ) SS40, MAS-3000 and CN Product lines

ISO 9001:2015 – Issued by DNV GL – Business Assurance

Lloyd’s Register

  • Lloyd’s Register #98/60070E4 – Design Approval, Type Approval Certificate and Type Approval List
  • Lloyd’s Register LR21228904TA– Type Approval– and Type Approval Certificate

National Fire Protection Association, standard for health care facilities (NFPA 30)

NSF 61 and 372 Certifications for Potable Water Fittings

  • NSF/ANSI Standard 61
  • NSF/ANSI Standard 372

United States Coast Guard


NFPA 99: Health Care Facilities Code, 2012, 2015 and 2018 Editions.

Louisiana Department of Environmental Quality (LDEQ)

Reference(s) February 1, 2022


Lokring general
  • The handling, installation and inspection of LOKRING™ fittings should be carried out only by qualified trained personnel. The LOKRING Installation Procedure provides the instruction and procedures necessary to qualify an individual as a trained LOKRING installer.
  • Three different source of hydraulic power may be used to install LOKRING fittings. Manual, electric (110 Volt or battery), and pneumatic pumps are available from a number of manufacturers through LOKRING or direct. All pumps must be single acting, automatic dump, with a 10,000 psi rating. When supplied by LOKRING these pumps come equipped with quick disconnect hydraulic fittings that mate to hydraulic hose and LOKTOOLS supplied by LOKRING.

Examples Pressure Rating for Stainless Steel Pipe Fittings..
  • NPS 1/2 Schedule 80 = 4760 Psi / 328 bar (ASME B31.1)
  • NPS 1/2 Schedule 80 = 5060 Psi / 349 bar (ASME B31.3)
  • Maximum design pressure given for temperatures from -60° to 100°F for ASME B31.1, and from -325° to 100°F for ASME B31.3.

Lokring products can bring significant benefits in both new installations and maintenance applications, enabling pipework installations up to 70% faster and cost saving of up to 70% compared to welding.

Reference(s).. www.lokring.com

Remark(s) of the Author...

Lokring.. 4130 Alloy Steel (LTCS-333) Process Fittings

In October 2023, I was asked... are lokring fittings suitable in propane service?

My answer was..

Standard fittings are not suitable for use at low temperatures, but the Lokring fitting 4130 Alloy Steel (LTCS-333) is a process fitting, which is suitable for low temperatures.
The .pdf file below gives you a brief overview about 4130 fittings.

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