– and the data to prove it.

Fluid Power Institute puts Zero-Leak Gold Plugs to the test

For a few years now, EPCO Products, Inc. of Fort Wayne, Indiana has offered its line of Zero-Leak Gold® Plugs and Fittings to the fluid power industry. As you might guess from the name, EPCO claims that Zero-Leak Gold Plugs will not leak under any circumstances. They back up their claim by a lifetime replacement guarantee. For some manufacturers, that proved enough to give Zero-Leak Gold a try. But many specifying engineers wanted to see hard evidence that Zero-Leak Gold Plugs and Fittings can stand up to their claim.

To deliver that evidence, EPCO commissioned a series of tests conducted by the Milwaukee School of Engineering Fluid Power Institute. One of the tests was intended to establish the lowest necessary torque value to achieve a zero leak seal. Not the talked about "zero leak" that is commonly defined as drips or drops within a defined time period, but literally no drips or drops. Also tested were the effectiveness of Zero-Leak Gold Plugs at proof and burst pressure.

The Zero-Leak Gold difference

Zero-Leak Gold Plugs are interchangeable with the SAE J514 plugs currently used in SAE J1926 ports of fluid power systems. They require no retooling or reengineering. What makes them unique is a taper under the head of the plug that forms a metal to metal seal with the existing taper in the SAE 1926 port. By engaging the two tapers, Zero-Leak Gold Plugs achieve exceptionally high unit loading at the interface. An o-ring located below the taper contact point of the plug acts as a backup seal. In contrast, the seal in a standard SAE J514 plug is achieved by forcing an o-ring into the port taper.

Test setup

Zero-Leak Gold Plugs were installed into six specifically designed manifolds. Three of these manifolds were made from standard industry ductile iron with a rated working pressure of 5,000 psi. The other three manifolds were made from standard industry aluminum with a rated working pressure of 3,000 psi. This setup allowed three samples of each Zero-Leak Gold Plug size tested.

To establish the minimum torque value needed for a reliable seal, Zero-Leak Gold Plugs were put through the NFPA 1,000,000 cycle endurance test. Torque values were increased until the endurance test was completed successfully for all Zero-Leak Gold Plugs. The cyclic pressure applied was 3,688 psi for aluminum and 6,156 psi for ductile iron, with a pulse duration of 92 milliseconds for ductile iron and 98 milliseconds for aluminum.

The initial test was conducted with 0.5 ft-lbs. of torque applied to each plug. This torque was unexpectedly successful at static rated pressures but predictably failed early in the endurance test. Torque values were then gradually increased. At 60% of SAE published torque values all Zero-Leak Gold Plugs passed the 1,000,000 cycle test without leaks. Furthermore, each plug was scribed across the top and onto the manifold before the test to indicate its position. At the end of the test, all plugs were still in their original position, meaning they had not backed out at all. That’s especially remarkable considering that except for brief maintenance shut downs, the Zero-Leak Gold Plugs ran continuously for 1,000,000 cycles.

Proof and burst tests

The final tests conducted on the Zero-Leak Gold Plugs were the proof and burst tests. Again, they were conducted to the NFPA/T2.6.1 R1-1991 standard. To pass the proof pressure tests, three samples must withstand twice the working pressure for a minimum of 60 seconds. The burst test requires three samples to withstand a minimum of four times the working pressure without failing. The proof test was conducted at a pressure of 10,000 psi for ductile iron and 6,000 psi for aluminum. Time at pressure was 120 seconds. All Zero-Leak Gold Plugs passed the test without failure.

The burst pressure test was conducted at pressures ranging from 21,769 psi to 26,453. Again, all Zero-Leak Gold Plugs passed without a detected leak. A manifold thread failure in one of the aluminum manifolds at 23,339 psi, more than seven times the rated working pressure for standard industry aluminum, did result in a leak.

Zero-Leak Gold – a new industry standard of performance

The FPI tests provide conclusive proof that zero leak performance is not a theoretical standard anymore – Zero-Leak Gold has made a longtime goal of the fluid power industry reality. It is reasonable to assume that if EPCO’s Zero-Leak Gold Plugs can withstand the rigors of the 1,000,000 cycle test without any leaks or even backing out by a fraction of an inch, they should perform exceptionally well in the field. What’s more, Zero-Leak Gold Plugs proved to be effective at assembly torques well below SAE recommendations. Which leads to one final question: When will Zero-Leak Gold Plugs become the product of choice? We suppose the answer is up to you.

Reprinted with permission from Fluid Power Journal, Jan. / Feb. 2001

Phone EPCO at 800/879-3726 • 260/747-8888