The best connection

The LOKRING® Single Ring technology is a method for connecting metallic refrigerant lines without brazing so that they are permanent and hermetically sealed. For this purpose, VULKAN constructs customised LOKRING tube connectors for any application based on the tube materials, dimensions and tolerances and the associated assembly tools.

Whether it is a matter of optimising costs, improving quality, or solving a problem – LOKRING® Single Ring is the answer!

Areas of application for LOKRING SINGLE RING-technology

The primary area of application is the manufacture of the refrigerant circuit in the series production of refrigerators and freezers. There are other applications for the manufacture of evaporators for automotive air-conditioning systems, for heat exchangers in refrigeration and air-conditioning technology (e.g. manufacture of heat pumps) or with the serial installation of refrigeration and air-conditioning technology (e.g. air-conditioning for buses). 


This is where the use of LOKRING has been proven a billion times over for the last 40 years. Nonetheless, it is in this segment that many LOKRING SINGLE RINGs are being constructed at present for new applications so that an increasing number of brazed connections are being replaced by LOKRING.


VULKAN has been a supplier of tube connections for the initial fitting of air-conditioning components to leading suppliers in the automotive industry for many years. The LOKRING SINGLE RING is being used for the series manufacture of evaporators and heat exchangers made of aluminium.


Would you like to cut costs, improve the quality, or solve a problem while manufacturing a refrigerant circuit? Would you like to dispense with brazing at a specific connection or dispense with it completely?


Situations may arise while installing heat exchangers into a refrigerant circuit, resulting from construction-related or material related constraints that make brazing impossible or uneconomical.


Aluminium lines are increasingly being used in the installation of bus air-conditioning systems due to cost and weight considerations. This is facilitated by the use of LOKRING SINGLE RING as an efficient and reliable alternative to brazing.


  • No heat generation
  • Higher tightness rate
  • Clean
  • No fumes
  • No combustion
  • No carbon emission
  • Fast and easy assembly within 10 sec.
  • Can join any metal material combination (copper, steel, aluminum, stainless steel, titanium...)
  • Does not require certified operators

Material Combinations

As LOKRING can join any tube materials with the same level of quality, you can switch the components and tubes of the cycle system to the most feasible and most cost-effective material – regardless of brazing standards.

Functional Principle

Thanks to the conical inner contour of the LOKRING, the diameter of the outer tube is reduced during assembly to such an extent that the inner tube and the outer tube create a hermetically sealed metal-to-metal connection. The lifetime gas-tightness of the fitted connection is ensured by the state of permanent elastic pretension, which is produced by the radial forces of the LOKRING acting in the opposite direction to the connection between the outer tube and the inner tube.

For our various Single Ring applications, we have made dedicated Best Practice documents, which are available on request.



Solder free tube connections for refrigerant lines

Lokring Single Ring technical specification

Approvals TÜV / UL (File SA12004)
Reference standards EN 378-2 and ISO 14903
Max. operating pressure Al 25 bar (360 psi) with 5 times safety: 125 bar (1800 psi)
Max. operating pressure Cu 40 bar (580 psi) with 5 times safety: 200 bar (2900 psi)
Max. operating pressure St 50 bar (725 psi) with 5 times safety: 250 bar (3600 psi)
Admissible refrigerants HFC, HC, not suitable for NH3
Temperature range -50°C up to 150°C (-58°F up to 302°F)
Tube diameter range 1.6 mm up to 28 mm (1/16“ bis to 1 1/8“)
Min. tube wall thickness 0.3 mm
Max. tube wall thickness 1.5 mm
Max. roughness of the tube surface Rt 40 Microns

The German standard of quality management is the benchmark for the international production of LOKRING. The certified quality management and the deployment of highly advanced industrial image processing systems facilitate 100% quality control.

Via the following link you will find and overview of all our products for OEM applications.

Link to products ​​​​​​​


Since our tube connections are hermetically sealed, we can ensure that no climate damaging refrigerants leak into the environment. Furthermore, LOKRING makes the use of environmental friendly but flammable refrigerants (HC) safer and allows the use of CO2 (R744). Thus, by using LOKRING tube connections you make a contribution to the active protection of the environment.