If you're a factory manager who is replacing some old air line fittings with new quick-connect models, be sure the fittings can handle the amount of air pressure expected in the line -- and be very sure you have good flow control and pressure release measures in place. Shock and surge are two phenomena that can blow a fitting apart. As tough as quick-connect fittings can be, you can't leave them to handle extreme increases in air pressure by themselves. If you do, you could be setting your machinery up for a disastrous failure.

Shock and Surge a Problem in Air Lines

Shock and surge are problems in any system that requires something to flow through lines. They're more often used in examples involving fluid lines, but air lines can suffer from them, too. In surge, fluid and air flow pressure can begin to grow, becoming stronger and stronger, before reaching a maximum point and then dying back down to normal. Shock is similar, but as the name implies, it is much more sudden, with a fast jolt of extra-high pressure hitting the connector.

Different quick-connect fittings are made to withstand certain pressures, just like different picture hooks are made to hold specific weights. If you get fittings that are made to withstand only the regular air pressure in the system, then if a surge or shock hits, the connection can break because it's just too weak to handle the extra pressure.

Even if the connection doesn't break, a phenomenon called socket brinelling can occur. This is basically an etching of one part by another part, usually when one of those parts is made of a harder material than the other. It's not unusual to have different materials, including different metals, making up a line fitting.

Flow Control and Pressure Release Needed

The amount of surge or shock in a line can be calculated, but it depends on the materials used in the piping, the setup of the machinery, the amount of flow control devices you have, the equipment creating the air pressure in the first place, and so on. As a general precaution, when you order the fittings, look back at previous surge issues your company has experienced and order fittings that will withstand surges and shocks greater in size than those previous ones.

Then turn your attention to flow control. These can monitor and modify -- and smooth out -- air flow in the system so that anything moving through them has a more consistent air pressure. Release valves are also necessary because they let you avoid shock and surge if you get enough warning that a pressure increase is occurring.

If you have more questions about fittings versus shock and surge, talk to a fittings and pipe supply company like Fittings Inc. They can help you calculate potential surge given your setup.