When you're running tubes and connections for delicate pneumatic equipment, it only takes a small problem with a single component to make the entire system break down. For years, only brass and aluminum fittings and seals were reliable enough for using in high stress situations like small plane hydraulics. Find out why the newest plastic seals from companies like Seal Pneumatics are a better option for difficult sealing situations.
Resistance to Corrosion
Installations in corrosive environments are particularly prone to failure if plain metal fittings are used, especially for sealing the ends of pressure lines. While coated metal fittings are available that are corrosion resistant as long as the coating is intact, these specialty parts are still relatively rare and tend to cost a lot more than basic plastic seals and other fittings. A plastic seal won't corrode from the interior or exterior, allowing you to install pneumatic lines in a wider range of inhospitable environments.
It's best to stick with compatible materials when working with pressurized tubing. If you're using a nylon or plastic line to run liquids or air through your equipment, why turn to aluminum or brass fittings that are primarily designed for metal pipes? Since most plastic lines are designed for pressure fittings that stay in place due to the friction between the fitting and the line, plastic seals offer the best fit for preventing leaks.
In the case of an aviation design or similar transportation project, every ounce counts. While a small brass line seal may not weigh very much on its own, you're likely to use hundreds or even thousands of them in a large piece of machinery where there are plenty of pressurized tubes to terminate or connect to other lines. All those small parts add up, so switching to plastic could trim off a few pounds from a project where reaching an exact weight is essential.
Less Reaction to Temperature
Finally, consider the basic reliability of plastic when it comes to temperature fluctuations. All materials shrink and expand due to heat gain and loss, but metals like brass tend to distort in size a lot more than a plastic material. In fact, the heat expansion of brass is so extreme that it's put to good use in bi-metal thermostat components. Why use a metal known for shrinking and expanding in a setting with a lot of temperature fluctuations when those size changes could result in a loose seal that leaks or falls out entirely?