Have you ever wondered why semi trucks make so much noise when they stop? If a car makes that much noise, we know there is a problem. It’s quite different with big rigs. The noise does not mean the vehicle needs semi truck repairs in Duncan, OK. The hissing and squealing you hear is the complex air brake system designed for such large vehicles. That noise simply means the brakes are working properly. To get a better idea of what’s going on during this clamor, we must answer a few questions.
How do air brakes work?
The most common air brake systems are foundation brakes. These work the same way as the systems in rail cars, operating on a triple-valve system. This involves three steps. First, charging pressurizes the system with air. The brakes cannot be released until the system reaches optimal pressure. Second, applying the breaks decreases air pressure and puts air into air reservoir tanks. Third, releasing happens when the air escapes after braking. The increased pressure releases the brakes. Most road vehicles are equipped with a graduated release system which creates a partial increase in pressure relative to a partial release of the brakes.
What are the main components of air brakes?
A foundation air brake system in a truck consists of:
- Air compressor: This pumps air into the storage tanks
- Air compressor governor: As the name implies, this controls the air compressor to regulate the amount of air in the tanks
- Air reservoir tanks: These hold the pressurized air used by the system
- Drain valves: When the vehicle isn’t in use, these are used to drain the air tanks
- Brake pedal (foot valve): This releases air from the reservoir tanks when depressed
- Brake chambers: This houses a slack adjuster which moves a diaphragm mechanism
- Push rod: Similar to a piston, this steel rod connects the brake chamber to the slack adjuster
- Slack adjusters: This adjusts the distance between the brake shoes
- Brake S-cam: The s-shaped cam pushes brake shoes apart
- Brake shoes:These create friction with the brake drum for stopping
- Return spring: Connected to the brake shoes, this reopens the brake shoes when needed
What maintenance is commonly needed for air brakes?
It is important to regularly check an air brake system to ensure proper maintenance of the following:
- Air pressure: For safe operation, drivers must ensure air pressure is optimal. The minimum operating pressure is 100 psi for a truck. The air pressure buildup rate should not take longer than two minutes. The correct cut-out and cut-in pressure for the governor must also be confirmed.
- Water: Condensed air can leave water in the air brake system. In cold weather, this can freeze, blocking air and causing the system to lock up. Proper operation of automatic drain valves can prevent this potentially disastrous problem.
- Air couplers: If the rubber seals on the air couplers are worn, air can escape. The compressor will have to run harder, putting more strain on the system. If this fails, the truck is stuck.
Whom should I contact for air brake repair?
If you are in need of parts for your air brakes or have further questions about semi truck repairs in Duncan, OK, contact the professionals at Heavy Truck & Trailer Parts. Experienced technicians await your call.