FAQs: Self-Sealing Fasteners & Washers

When using just an O-Ring or deformable washer (regardless of material) as a pressure sealer you sacrifice the ability to fully clamp, plus the degree of thread sealing is not predictable. That’s because the O-Ring or washer interferes with achieving 360° metal-to-metal contact between the underside of the head and mounting surface.
See Comparison Illustrations.

Both technologies share the goal of high-pressure sealing, but that’s where the similarities end. The APM O-Ring washer design provides the user with a pre-assembled, one-piece fastener, ready to be installed in one step—eliminating the dependence of the installer to apply the correct amount of sealant/compound. Its inherent geometric chamber and nested O-Ring creates the perfect solution for maximum sealing and service reusability which is the result of a unique patented asymmetrical-shaped chamber. Sealants and compounds do not allow for easy replacement. They usually require the screw or bolt to be drilled out for replacement which can be problematic. They are really intended for one-time use. And in closed factory environments there is also the question of workers safety from inhaling sealant's fumes. Chemical dispersal is also an issue.

The APM design and patent (U.S. patent no. 3,175,454) was conceived to generate high-pressure fastener sealing to 20,000psi and maximum multiple usage. However, this frequently asked question cannot be answered with a simple number because each application condition is different in terms of reinstallation frequency, in combination with environmental and operating conditions. Because of the asymmetrical annular design, minimum ORing friction occurs producing minimum wear which results in maximum reusability. Repeat orders from many customers confirm satisfaction from their field servicing experiences.

The APM design and patent (U.S. patent no. 3,175,454) was conceived to generate high-pressure fastener sealing to 20,000psi and maximum multiple usage. However, this frequently asked question cannot be answered with a simple number because each application condition is different in terms of reinstallation frequency, in combination with environmental and operating conditions. Because of the asymmetrical annular design, minimum O-Ring friction occurs producing minimum wear which results in maximum reusability. Repeat orders from many customers confirm satisfaction from their field servicing experiences.

Yes. We have a special bonding process which provides excellent paint adhesion.

Yes. For example, you can order an APM SEELSKREW®, SELBOLT® or SEELNUT® with a fully-adjustable, anti-vibration option. Choice of resilient engineered embedded polymer pellets, strips (bars), or standard/high-temperature, surface applied patches can be added to the threaded area for compression and locking action. Eliminates need for costly lock washers, cotter pins, or castellated nuts. Impervious to a wide range of chemicals, water and lubricants. Choice of locking materials.

After patenting the original self-sealing fastener (screws, bolts, rivets) design in 1949, featuring an embedded O-Ring in an symmetrical groove located in the underside of the head – our designers then discovered that  installing an O-Ring on a sealing-nut would NOT be an optimal solution because of a totally different dynamic. The sealing process requires that the first/second thread be removed to accommodate the sealing mechanism. Initially, that step weakens the gripping power and clamp load of a torqued nut. Simply embedding a conventional O-Ring into the newly made groove does not compensate for the lost strength. In fact, there is a critical secondary problem of O-ring surface damage due to the cutting effect from the sharp thread’s edges. This results in diminished reusability as the O-Ring is now degraded. Instead, our engineers designed a bonded elastomeric (typically silicone) insert which also feature its own threads on the ID surface, providing 100% gripping and sealing and  high reusability. We find it strange that any competitor would market a sealing nut that does not meet this established, proven criteria. This superior sealing design allows the SEELNUT® to achieve 6,000psi rating internal/vacuum — a feat that could not be accomplished with a pressed O-Ring.

UL recognized, APM SEELNUTS are reusable and fully adjustable; they resist vibration and are available with additional optional thread locking  capabilities by the incorporation of a strategically embedded Nylon pellet.

This is an important question for several reasons. When using a mechanical sealing fastener, employees are protected from breathing undesirable fumes produced by liquid sealant & adhesives. There are no environmental disposal problems either. With regard to environmental recycling for electrical/electronic products — a mechanical self-sealing fastener is easier to remove and has no chemical residue issues. It’s already a mandated consideration in Europe and is becoming increasingly important in the U.S. All APM fasteners are UL Recognized and RoHS Compliant.

To its advantage, the APM UL Recognized SEELOC® washer looks and performs differently than any other sealing washer. This compressible stainless steel washer, with a bonded silicone seal, features two concentric ridges that function as a barrier-rib — one on the outside edge and the other on inside hole surface making sealing contact with the mating screw/bolt shank creating a perfect high-pressure seal to 100 psi (internal/external).