General Information about the Triple-Lok® Fitting
The design of the Triple-Lok® fitting is as simple as possible. The creation of a flare, which is easy to produce at the end of the tube, allows for the sealing of fluids under high pressure.
The fitting consists of three parts:
Fitting body, sleeve, and nut.
The tube end is flared to 37° and clamped between the sealing cone of the fitting (seat) and the sleeve (support sleeve) by the nut, which creates a very effective seal in the only leak path between the sealing cone of the fitting and the support sleeve.
The support sleeve fulfills several important functions:
- It provides a right-angled clamping surface for the nut. This reduces the tendency of the tube to rotate during assembly.
- It supports the tube wall, preventing the flaring contour from expanding when the fitting is tightened.
- By simply replacing the sleeve, the fitting can be adapted for both metric and inch OD tubes. This feature helps Triple-Lok® fittings achieve worldwide acceptance.
The Triple-Lok® fitting has the smallest sealing diameter of all designs. The sealing surface is only slightly larger than the fluid's flow area. Compared to the connection's clamping performance, the small sealing diameter achieves compactness and low torques during assembly. The design was initially standardized as J.I.C. (Joint Industrial Council) and later adopted by the S.A.E (Society of Automotive Engineers) and I.S.O (International Organisation for Standardisation) to guarantee interchangeability among manufacturers by defining dimensions. Although many manufacturers adhere to the standardization rules, due to the multitude of manufacturing methods and the quality standards used, there are considerable differences in the actual performance of the fittings. The components of the Triple-Lok® fittings are manufactured with optimal manufacturing methods and state-of-the-art equipment; thus achieving and ensuring the integrity of the design, high performance, a long service life, and high quality.
Straight fitting bodies are made from cold-drawn hexagonal steel. All shaped pieces are forged, preventing potential leak paths in multi-component molded parts, such as brazed parts, from occurring in the first place. Forged Triple-Lok® shaped pieces are made of solid steel for higher pressure resistance and also reduce the risk of deformation on the sealing cone during repeated assembly. This is an improvement compared to the components of brazed designs, as brazed designs usually have lower hardness and therefore greater deformation of the sealing cone.
Triple-Lok® support sleeves are cold-formed to achieve an optimal combination of strength and toughness.
Nuts for all sizes – with the exception of the three largest (20, 24, and 32) – are cold-formed. Cold forming improves material strength and thus the load-bearing capacity of the nut. Larger nuts are hot-formed from high-strength steel.
As seen in the illustration, tightening the nut causes the flare to clamp against the sealing cone of the body, thus creating a leak-free connection. This clamping on the 37° cone gives the connection a certain elasticity, which prevents loosening due to vibrations. The clamping force causes a radial stress ($F_R$) that deforms the sealing cone of the fitting inwards. The resistance of the sealing cone to elastic deformation creates a pre-tension (similar to a spring) and thus a firm connection.
The clamping force of the nut withstands the stresses caused by the pressurized fluid. The connection remains leak-free as long as the clamping force is higher than the opposing pressure force. A Triple-Lok® fitting correctly assembled with the suitable tube seals reliably under pressure until the tube bursts.
The seal in Triple-Lok® fittings is realized between two smooth metal surfaces, the sealing cone of the fitting and the inside of the tube flare. Therefore, the sealing surfaces in the sealing area must be round and smooth and free of any scratches, impact marks, spiral machining marks, cracks, or weld beads.
Due to the simple flaring and the tube bending properties, seamless or welded and seamless drawn, normally annealed tubes are recommended for Triple-Lok® fittings.
Pressure
Triple-Lok® fittings are designed for nominal pressures up to 500 bar with a 4-fold safety factor.
Robust, adjustable stud fittings
Eliminate possible assembly errors caused by excessive screwing in of angle or tee fittings. This reduces warranty claims due to unnoticed assembly errors.
Cr(VI)-free surface
Triple-Lok® fittings comply with the requirements of the European Directive 2000/53/EC.
Corrosion resistance
Triple-Lok® fittings have protection of at least 120 hours against white rust, thus exceeding the industry standard.
Connectable elbow fitting
Increases reliability in dynamic pressure conditions and elevated pressure levels.
Safety
The flared tube provides a firm and clearly noticeable assembly stop for the nut. The flare prevents the tube from blowing out, which is why the Triple-Lok® system is considered very safe.
Reduced sealing points
Triple-Lok® fittings have only one sealing point (between the sealing cone and the tube flare). This results in a highly reliable connection.
Easy assembly
Smaller pressurized sealing diameters mean high-pressure properties with relatively low torques. This allows the use of smaller wrenches for easy installation and maintenance.
Wide temperature range
Triple-Lok® fittings are suitable for use at extremely low to extremely high temperatures. The temperature resistance of the selected material is decisive.
Media compatibility
Triple-Lok® fittings and seals are available in various materials. This means that almost all media and environmental conditions can be covered.
Tube materials
Triple-Lok® fittings can be used with most tube materials; examples include steels of different strengths, stainless steel, copper, and aluminum.
Wide wall thickness range
Triple-Lok® fittings are suitable for very thin to medium wall thicknesses. Tubes with optimal wall thickness can be used to reduce overall system costs.
Easy Installation and Maintenance
A small overlap simplifies installation and minimizes the risk of levering out the tube during system maintenance. This is simple and fast.
Adaptation to metric and inch tubes
Triple-Lok® fittings can be used for inch and metric tubes by simply replacing the sleeve.
Adaptation to hose assemblies
Triple-Lok® fittings are designed for direct connection to the 37° cone hose fitting, which is the most popular hose connection in the industry worldwide.
Shaped pieces
Triple-Lok® fittings do not have any brazed joints that could leak. One-piece shaped pieces are more reliable and have a longer service life compared to designs made of brazed shaped parts.
High-quality shaped pieces
The high strength of Triple-Lok® fittings minimizes the risk of deformation of the 37° sealing cone during assembly, maintains the flow area, and offers good reusability.
Cold-formed sleeves and nuts
Sleeves and nuts in common sizes are cold-formed because the optimal structure offers high resistance and high strength. This gives these parts high reliability and long service life.
International level design
Triple-Lok® fittings are available worldwide and ensure interchangeability; they comply with SAE and ISO standards. 37° fittings are the most commonly used fittings worldwide.
Availability
Triple-Lok® fittings offer the widest range of sizes and fitting bodies of all fittings. This provides users with the optimal selection of connection options. Standard materials are steel, stainless steel, and brass.