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What is a Glad Hand?

Lori Kilchermann
Lori Kilchermann

A glad hand is a device found at the end of an air line that connects to another air line. It is found on railroad cars and slightly resembles a pair of hands involved in a hand shake. The two hands are connected by placing them together at right angles and then twisting them to form a straight line. To remove the air line, the two glad hand assemblies are simply twisted to a 90-degree angle.

While a glad hand is found on many train cars, perhaps the most common location for this assembly is on a semi tractor and trailer. The lines used to supply the semi trailer with air to operate its braking system flows from the semi tractor's air tanks through a glad hand and into the trailer's tanks. While much smaller in size, they are exactly like those used on a train. Assembly and disassembly is the same as well.

Woman holding a book
Woman holding a book

Typically made of cast aluminum, a glad hand has a small rubber gasket located in the center and surrounding the air hole. When coupled together, the two rubber gaskets sit against each other, providing a leak-proof seal for the air system. A small tang cast into the device locks into a clip on the opposing glad hand and snaps the two in place when connected.

On semi tractors, the devices often become dirt filled and debris riddled from driving miles without a trailer hooked up to the tractor. It is imperative that water, dirt and debris be removed from the fittings prior to hooking them up to a trailer. Water is an especially dangerous enemy since the air pressure will force it deep within the trailer's air lines and it could freeze and cause severe problems during inclement weather. Covers should be placed over unused fittings or be attached to the dummy connection on the back of the tractor's cab.

Maintaining the fittings is an easy task. Keep the dirt, water and debris out of the fittings and apply a little grease to the rubber gasket to keep it pliable. Replacement gaskets are readily available at most truck stops and are simply pulled out and pushed in. The air line running to the fitting should also be checked for cracks and abrasions and repaired before they break and cost the vehicle its braking system.

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      Woman holding a book