Threaded gas pipe fittings utilize precision-engineered threads that, when screwed together, form a tightly interlocking connection. The threading is designed to achieve a mechanical bond that holds the components securely under pressure. In high-pressure applications, the threads are engineered to a very fine tolerance, ensuring a close fit that minimizes any gaps. Additionally, sealants such as Teflon tape or pipe thread compound are commonly applied to the threads. These sealants work by filling any micro-gaps between the threads, thereby improving the leak resistance. The combination of precise thread geometry and the use of sealants results in a robust, reliable seal that prevents gas leakage, even in systems operating under high pressures.

Compression fittings work by utilizing a compression ferrule or ring that is squeezed around the pipe as the fitting is tightened. This compression forces the pipe against the inner surface of the fitting, ensuring a tight, leak-resistant seal. The key to the effectiveness of compression fittings is the uniform pressure applied by the ferrule, which ensures that the pipe is sealed around its entire circumference. This sealing process is particularly effective in high-pressure gas systems, where pressure might otherwise force a loose fitting to slip or allow gas to escape. Compression fittings also provide excellent vibration resistance, which is important in systems subject to movement, further enhancing their ability to maintain a leak-proof seal over time.

Flare fittings employ a metal-to-metal seal, which is formed when the flared end of a pipe mates with the tapered flare seat of the fitting. This creates a strong, tight seal that is particularly resistant to high pressures. The 45-degree angle of the flare ensures that as the fitting is tightened, the surfaces press together firmly, reducing the potential for leaks. This type of fitting is commonly used in applications where high-pressure gas flow is required because the metal-to-metal contact is more resistant to deformation than elastomeric seals, providing long-term reliability. The flare fitting design is particularly favored in systems where pressure fluctuations and temperature changes are frequent, as it offers excellent stability.

In modern gas pipe fittings, O-ring seals are frequently used to ensure a tight, reliable seal. O-rings are typically made from high-quality elastomers (such as nitrile rubber or Viton) that are specifically chosen for their resistance to pressure, chemicals, and temperature extremes. These seals are placed at the mating surfaces between the pipe and the fitting. When the fitting is tightened, the O-ring is compressed, which results in a hydraulic seal that fills microscopic voids and ensures that gas cannot escape. The use of O-rings offers the additional benefit of flexibility, as they can accommodate slight movements of the pipe while still maintaining a secure seal. This is particularly beneficial in systems where there are temperature changes or vibrations that could otherwise loosen traditional mechanical seals.

Gas pipe fittings are designed and manufactured to high tolerances to ensure that the components fit together perfectly during installation. This precision ensures that the mating surfaces (whether threaded, flared, or O-ring-sealed) are smooth, flat, and aligned, which is critical in preventing leaks in high-pressure systems. Small imperfections, such as thread misalignments or surface irregularities, can lead to gaps that would allow gas to escape. By maintaining tight tolerances and smooth finishes, fittings form a reliable seal that prevents such leakage. The materials used in manufacturing are also selected for their ability to maintain these tolerances over time, especially under stress.