Readers ask: What Are The Hoses Connected On Tractor Trailers?


For air brake hoses and tubing, DOT certification is required; however, certain applications for fittings and tubing, such as air horns, air-ride seats, axles, and others, do not require DOT certification.

Selecting the right DOT air brake fittings for your application

For a wide range of vehicles, from pickup trucks to commercial vehicles, dot conforming air brake fittings are essential.

Brass compression fittings

While they are priced competitively, installation is more labor-intensive than other types of fittings; however, once installed, they are considered excellent in terms of forming joint connections.

Brass push-to-connect fittingsĀ 

Brass push-to-connect fittings reduce fitting assembly time and complexity by up to 90% while maintaining the performance profile of brass compression fittings. The unit cost is higher, but the labor savings more than compensate for the difference.

Composite push-to-connect fittingsĀ 

Composite push-to-connect fittings have all of the labor-saving features of brass fittings, but are lighter in weight and less expensive due to the polymer. Customization is also enhanced because the polymer is formed using a variety of injection molding processes.

Higher temperatures and elastomeric sealsĀ 

In high-heat areas, some manufacturers have chosen brass compression fittings, while others have modified the elastomeric seal used in push-to-connect fittings and designed new DOT-rated fittings.

Assessing port-end thread options

STO fittings have been found to be more reliable connections, but they come at a higher cost for truck OEMs, and they may require some customization of the fittings or their respective components. The added reliability must be weighed against the increased cost by the truck OEM.

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To learn more about what to consider when choosing DOT air brake tube fittings, download Parker’s guide. Truck OEMs want to avoid performance issues with air brake assemblies at all costs, so careful consideration should be given to selecting the right type of DOT fitting.

Related content

For hydraulic hose assembly, truck manufacturers prefer brass hose fittings.

What are the red and blue lines on a tractor trailer?

Before moving the trailer, connect these lines to the corresponding couplers and sockets on the trailer. The red line is the air line for the trailer’s emergency brake, the green line is the electrical line, and the blue line is the air line for the trailer’s service brake.

What connects the tractor and trailer?

The fifth-wheel coupling connects a semitrailer to its towing truck, tractor unit, leading trailer, or dolly.

What are the things on the back of tractor trailers?

Aerodynamic panel skirts, side panels, or side skirts are the panels under the truck’s body; rear tail fairings, trailer tails, or sometimes boat tails are the panels that hang off the back; whatever you call them, their purpose is to reduce drag and save fuel.

Which glad hand goes where?

The glad hands (connectors) are usually color coded, red to red, etc., but if they aren’t, the supply (RED) is usually on the driver side of the trailer, or on the back of the tractor. The blue is called the “service” line, and it is used as a “signal” line to activate the trailer service brakes (but not the PARK brakes).

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What color is the emergency line on a tractor trailer?

The tractor protection valve closes when the emergency line loses pressure (the air supply knob pops out). Emergency lines are often coded with the color red (red hose, red couplers, or other parts) to avoid being mixed up with the blue service line.

What color is the supply line on a tractor trailer?

If the trailer connectors are not color coded, the emergency line will connect to the receptacle closest to the driver’s side on the front of the trailer. If the trailer connectors are not color coded, the emergency line will connect to the receptacle closest to the driver’s side on the front of the trailer.

What is the bar on the back of a tractor called?

The steel bars hanging from the truck’s platform bed are called “rear underride guards” or “rear impact guards,” and they’re designed to keep vehicles from sliding underneath a trailer during a rear-end collision. Unlike most cars, truck trailers and straight trucks don’t have rear bumpers.

What are the lights on a tractor trailer called?

Side marking u2013 Also known as “retroreflective sheeting,” these are the alternating red and white stickers lining the bottom of each side of the trailer, which are designed to reflect headlights and alert approaching drivers that a trailer looms ahead of them.

What do you call a tractor without trailer?

Bobtail u2013 A tractor without a trailer, also known as a straight truck.

What is the back of the trailer called?

A tractor unit, a detachable front-axle assembly known as a dolly, or the tail of another trailer support a large portion of a semi-trailer’s weight, while its own wheels only support the semi-trailer’s rear.

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What are the little doors on the back of tractor trailers for?

When a “vent door” is left open, it allows air to circulate throughout the trailer; if the door is left open, the trailer is most likely empty and being “aired out,” which helps to prevent mold and mildew from growing inside.

How much fuel do trailer skirts save?

According to Stemco, among the devices studied, u201cside- skirts and boat-tails provide the greatest drag reductions,u201d and that using both a rear fairing and a side skirt can save nearly 1,400 gallons (5,300 liters) of fuel per truck, per year.

What is a glad hand rubber?

Gladhand seals fit standard gladhands to prevent air from escaping air lines that connect trucks or semi-tractors to trailers. Seals are sometimes colored blue or red to match service or emergency gladhands, while silver/black is universally used.

Why is it called a glad hand?

Gladhand connectors, also known as gladhand couplers, are interlocking hose couplings used to connect hoses supplying pressurized air from a tractor unit to air brakes on a semi-trailer or from a locomotive to railway air brakes on railroad cars. Gladhand connectors resemble a pair of “shaking hands” when interlocked, hence the name.

What are the glad hands on a tractor trailer?

This is the coupling device that connects the trailer’s service and supply lines to the truck or tractor, and it has a snap-lock position and a rubber seal to prevent air from escaping.

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