To prove this, EPCO tested the design without the O-ring in place (a similar test can be viewed on EPCO's Sealing Systems Video). The fitting experienced zero-leakage in these tests, despite removing the O-ring. "The real seal is the metal-to-metal," Aichele notes. "If you take the O-ring out of other conventional, SAE standard fittings, there is no seal period."

Why it works

The design allows for higher unit loading, gap minimization, invocation of elasticity and longer-term sealing integrity. To demonstrate how it works, Aichele asks people to visualize a door jamb and how it works. If you put a door jamb at the base of a door and pushed on the door, which would give first? The door and the frame would give first, he explains, because the tapered door jamb is wedged tightly into place. "That's exactly what happens with this," he says. "Because of the taper, the tighter you tighten it, the greater the seal, resulting in maximum gap minimiation. Furthermore, the seal is achieved without the use of any type of sealing or locking chemical. The absence of chemical additives makes it possible to disassemble and reassemble as needed without the possible contamination of the fluid system."

And because there is really a small area that comes into contact to create the metal-to-metal seal, the design dramatically increases unit loading on those surfaces. "The area of contact is very small," Aichele says, "but the torque on those areas is dramatically increased."

One way to visualize the effect of this on the fitting, is to imagine two people standing on a putting green, one in golf shoes, the other in high heels. The person wearing golf shoes is going to leave next to no impression on the green while the person in high heels is going to sink into it.

"What you have done is dramatically increase the loading on the end of those high heels," says Aichele. "That's exactly what we have done here. We call it unit loading. You don't have to apply as much force but you get a more dramatic, unit

This is what makes the technology unique, he notes. The geometry of the design does all the work, whereas other designs may need force or brute force applied to form the seal. "Other designs require applying a lot more torque to force the O-ring into the cavity to hold it. And there's still no assurance that it will hold," Aichele says.

The Zero-Leak Gold Plug's unique gap minimization design allows for the use of a standard metric O-ring that is smaller than the O-rign used in comparable SAE plugs, using the O-ring as the only seal. The effects of the taper prevent the O-ring from extruding into the port interface.

"In our design, when you start bringing those mating tapers together, you invoke gap minimization," Aichele explains. "That gap is so close that it doesn't take a very big diameter of anything to form a seal."

And Williamson notes in his discussion of Adjustable Fittings in EPCO's sealing system video, "Each (the metal-to-metal and O-ring seal) works independently of the other. We believe metal-to-metal will fail eventually. The O-ring will also fail without metal-to-metal backup."

The result: Zero leakage

EPCO fittings are just as effective at low pressure as they are at high pressure. They won't ramp up under high pressure and then relax under a lower pressure.

And the fittings, which are available with hexagon and socket heads in sizes -02 to -32 in mild steel, stainless steel, aluminum and brass, are interchangeable with SAE J514 and ISO 6149 standard ports because they correspond to the standard SAE taper. But the EPCO fitting design is the only one that uses two seals.

Because of the interchangeability of EPCO fittings, a company can try the fittings without enormous design changes in its product. "They aren't forced into having a bastard design to mate with our component. They aren't retooling," says Aichele. "And if for some reason, they aren't satisfied, what's the downside? All the have to do is go back to the part they were using. No other change is involved."