The SAE J2337 port-and-fitting system, Figure 4, is a new concept in fitting design. Design characteristics inherent to its success are:

* a significant reduction of the acting force on the port system due to fluid pressure,
* lighter weight, yet higher strength,
* flow capacities consistent with existing port systems, and
* leak-free performance.

Reducing the pressure-acting area can reduce the acting force from fluid pressure. This means that the O-ring must have as small a diameter as possible, but larger than that of the flow passage. This is accomplished by placing the O-ring in the bottom of the port. The table below shows how pressure capacity performance was increased compared to the O-ring boss system for the same size.

This improvement is significant because all forces acting on the fitting due to pressure are reduced an average of 100.5%. Consequently, the lower stresses that result enable reduction of the cross-section areas and the amount of material used in the fitting and the port. Furthermore, lighter and weaker metals, such as aluminum or cast iron, can be used at higher pressures than before. The result is a lighter product manufactured at reduced cost and with improved performance.

The double seal characteristic greatly improves resistance to leakage. It consists of a conical metal-to-metal seal and a radial O-ring seal. The main advantage of this configuration is the extrusion resistance of the O-ring, which is attributed to zero clearance in the critical corner of the O-ring groove. This is achieved by the firm, even, cold-forged surface contact on the conical surface that occurs when tightening the fitting.

The swivel feature eliminates the need for an adapter and eliminates one potential leak point in a typical tube and/or hose connection to the component body. Figure 6 compares both installations with the same functional features.

This comparison can be extended to any other tube connection such as 24° cone compression, 37° flare, and many others. In addition to cost reduction and simplification, the swivel feature reduces installation time, reduces assembly problems, and simplifies plumbing systems.

Results from cycle testing

Six samples of size 6, 8, and 16 were cycle-tested for 1 million cycles to peak pressure. All samples were in excellent condition after cycling and were 100% usable without damage.

Two SAE J2337 fittings, size 8 and 6, were fatigue-tested and assembled in a hydraulic pump housing made of aluminum. The cycle pattern is shown in Figure 7, below. Higher vibration conditions were also applied during testing.

O-Ring boss ports tested in the aluminum housing did not produce satisfactory results. Cracks and separations occurred at various times up to an average of 400,000 cycles. The SAE J2337 port and fitting, on the other hand, performed without any failure to 26 million cycles. These results reinforce the advantage of the stress pattern of the port and the optimum stress pattern of the SAE J2337 fitting.

Benefits realized

As anticipated, the J2337 fitting provides a number of benefits to both OEMs and users:

* higher pressure capabilities,
* zero leakage,
* elimination of adapter and one potential leak point in a typical hydraulic assembly,
* one-piece construction of adapters, so no brazed or welded joints are needed,
* no-swing assembly,
* no accidental O-ring drop out,
* simple port geometry,
* unlimited reusability,
* minimal influence on the adjacent port structure, and
* minimal chance of becoming over-torqued during assembly.

Summary

Equipment manufacturers and users of hydraulic systems are demanding lighter, more powerful components. Components must be built with a higher degree of power density, which necessitates higher system pressures. Current hydraulic components typically can operate at up to 6000 psi working pressure, limited, to a high degree, by existing port and fitting systems.

The main disadvantage of existing threaded port/fitting systems is the placement of the O-ring on the undercut diameter. Potential for improvement of these designs is limited. Increasing the thread size would result in a stronger cross section, but create a higher load force and increase the pressure acting area.

The new SAE J2337 port and fitting system does not suffer this limitation because sealing occurs in the bottom of the port. Pressure capacity is increased an average of 100%. This innovative design allows for higher-pressure ratings for future requirements.

The swivel feature eliminates the need for adapter fittings when elbow positioning is required. Test results support working pressures up to 12,000 psi with a design factor of 4:1.

The double seal principle ensures much higher leak proof performance. Substantial savings result when replacing 4-bolt flange systems.

Darko Brozovic was product engineering manager at Fluid Line Products Inc., Willoughby, Ohio when this article was originally published. The SAE J2337 fitting design is based on his patent, which was originally developed for Fluid Line Products' Uniport 10K fitting. For more information, click here to visit the website or email flp@fluidline.com.