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How does an air dryer in a pneumatic brake work?
08.10.2024
Pneumatic braking systems are essential for heavy vehicles such as trucks and buses, as well as construction and agricultural machinery. Unlike light vehicles, which use hydraulic power, pneumatic braking systems harness compressed air to ensure reliable, powerful braking force.
How a pneumatic braking system works
The operation of an air braking system is complex and involves several key components working together to ensure effective vehicle deceleration. Here's a detailed explanation:
- Air compressor: Driven by the engine, the compressor draws air from the atmosphere and compresses it, increasing its pressure before sending it into the system.
- Air desiccant: The compressed air then passes through an air desiccant containing drying granules to absorb moisture, preventing the system from corroding or even freezing. Depending on the model, this same filter can also trap oil and solid contaminants.
- Non-return valve: This device prevents compressed air from flowing back into the compressor.
- Air reservoir: As long as the brake pedal is not operated, compressed air is stored in a reservoir where its pressure is regulated. If the pressure becomes too high, a regulator releases the excess air to prevent damage. This regulator guarantees constant pressure, ensuring that the brakes work properly.
- Brake pedal: When the brake pedal is depressed, a valve opens, releasing compressed air to the brake chambers at the front and rear axles of the vehicle. Depending on the pressure applied to the pedal, more or less compressed air is released.
- Brake cylinder: Under the effect of pressure, compressed air activates the braking mechanism. When the driver releases the brake pedal, the air used is released into the atmosphere through exhaust ports.
The importance of filtering compressed air
The compressor draws in air that naturally contains moisture, which condenses when compressed, potentially causing corrosion or freezing of the system. The oil in the circuit can also mix with this water vapour, creating a viscous substance that affects the valves, slows brake response and causes premature wear of the brake linings.
Pneumatic braking systems require a large quantity of clean, dry compressed air per minute to operate correctly. The installation of an air dryer is therefore essential to maintain decontaminated air in the system, guaranteeing your safety and braking efficiency.
Pneumatic braking systems require a large quantity of clean, dry compressed air per minute to operate correctly. The installation of an air dryer is therefore essential to maintain decontaminated air in the system, guaranteeing your safety and braking efficiency.
How an air dryer works
Replacing the air dryer
Over time, the desiccant filter elements become saturated and lose their effectiveness, requiring regular replacement. The frequency of replacement depends on the manufacturer's recommendations and the vehicle's operating conditions.
There are a number of signs that a replacement is required, such as an excessive amount of water at the bleed valve, meaning that the desiccant material is saturated, or a bleed valve stuck in the open position, slowing down the build-up of pressure in the system. A visual inspection may reveal damaged cartridges or twisted hoses, also indicating the need for a change. To prevent costly breakdowns and ensure safe operation, it is therefore crucial to follow manufacturers' recommended maintenance practices, use quality spare parts and carry out regular inspections.
There are a number of signs that a replacement is required, such as an excessive amount of water at the bleed valve, meaning that the desiccant material is saturated, or a bleed valve stuck in the open position, slowing down the build-up of pressure in the system. A visual inspection may reveal damaged cartridges or twisted hoses, also indicating the need for a change. To prevent costly breakdowns and ensure safe operation, it is therefore crucial to follow manufacturers' recommended maintenance practices, use quality spare parts and carry out regular inspections.
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