Rubber gaskets fail for a variety of reasons. MTAP, an acronym that helps engineers design better gaskets, explains four common causes of gasket failure. If you want better rubber seals, design them with media (M), temperature (T), application (A), and pressure (P) in mind. Otherwise, you risk sealing failures that can have expensive, inconvenient, dangerous, or even tragic consequences.
The M in MTAP stands for media, which includes substances such as fuels, chemicals, and cleaners that come into contact with rubber gaskets. This contact may be sporadic and incidental, or continuous and long-term. When it comes to the M in MTAP, remember to consider both the type of media and the nature of the contact. Over-engineering a gasket adds unnecessary expenses, but gasket failure can be costly.
Consider this mobile equipment example. Gaskets made of the wrong rubber were installed on the fuel doors of a fleet of vehicles. Because the rubber couldn’t resist petroleum products, the seals deteriorated quickly and caused small pieces of rubber to enter the fuel lines. The vehicles were removed from service and engine maintenance was required. It was an expensive lesson about compound selection.
The T in MTAP stands for temperature, which covers the entire range of temperatures to which a rubber gasket is exposed. This includes the normal range of operating temperatures as well as extremes. Even if a seal doesn’t fail, performance becomes less predictable when rubber reaches the limits of its service temperature range. Rubber softens at high temperatures, but cold can make it hard and brittle.
The Space Shuttle Challenger Disaster from January 1986 provides a tragic example. Florida winters are usually mild, but the overnight temperatures at Cape Canaveral were below freezing – and NASA had never tested the Challenger’s rubber O-rings at extreme cold. The O-rings cracked and permitted an exhaust leak that caused a tank full of liquid oxygen and hydrogen to rupture shortly after takeoff.
The A in MTAP stands for application, a term that encompasses more than just gasket installation and use. To avoid seal failure, think about a day in the life of your rubber part – as well as what happens to it over the course of weeks, months, and even years. As an example, consider the case of a rubber gasket that’s used with underground mobile equipment.
A company had installed a nitrile rubber part on a drill that’s used with wells. Nitrile offers excellent oil resistance, but incidental contact with petroleum products wasn’t the biggest problem. Although the equipment was used underground, it was stored aboveground and outside. Because nitrile is attacked by ultraviolet (UV) light, the sun’s rays destroyed the rubber gaskets.
The P in MTAP stands for pressure, which also includes vacuum levels. With high-pressure seals like the ones used in hydraulic systems, gasket failure can cause the seal to break-off or even fly-off. Smaller, less noticeable leaks may also occur. Vacuum pressures are considerably lower than atmospheric pressure, but that doesn’t mean vacuum seals aren’t susceptible to failure.
Consider the example of a thermoplastic part that was used aboard airplanes. This part required a rubber gasket, but the gasket was too soft to create an adequate vacuum. Consequently, leaking occurred. Inflatable seals that are filled with air also need to maintain adequate pressure to ensure sealing action during manufacturing operations.
Other Reasons That Rubber Gaskets Fail
MTAP describes four reasons why rubber gaskets fail and provides easy-to-remember guidelines for better seal design. Yet media (M), temperature (T), application (A), and pressure (P) aren’t the only reasons that a gasket project can fail. Overengineering a gasket is also a failure of sorts since paying too much for a material that you don’t really need is a form of manufacturing waste.
Two examples show how to avoid this. An autoclave manufacturer thought it needed Viton®, an expensive fluoroelastomer, for rubber mats. Elasto Proxy shared that less expensive EPDM USP Class VI rubber would suffice instead. Similarly, when a bicycle manufacturer asked about using an aerospace grade nylon for a molded parts, Elasto Proxy explained that nylon 6/6 would cost less and still meet the requirements.
Ask Elasto Proxy for Sealing Success
As an experienced fabricator and distributor of industrial rubber products, Elasto Proxy has the technical knowledge and application expertise to support your gasketing project. Talk to our solutions providers about MTAP. After all, it’s a term we invented. To ensure your sealing success, we can also help you with calculations such as bend radius and perform compression, stretch, and pull testing at our in-house lab.
Are you ready to get started? Contact Elasto Proxy.