FREE Air Brake MCQ Question and Answer

Question 1

How much force is applied to the push rod in a type 30 brake chamber when a 40 PSI brake application is made?

Accepted Answer

1200 PSI

Answer

The force applied to a brake chamber's push rod is calculated by multiplying the chamber's effective diaphragm area by the air pressure. A Type 30 brake chamber has an effective area of 30 square inches. Therefore, a 40 PSI brake application generates 30 sq. in. * 40 PSI = 1200 pounds of force.

Question 2

When the air system reaches operational pressure, what does the compressor do?

Accepted Answer

Goes into an unloaded stage

Answer

When the air system reaches its maximum operational pressure, the governor signals the compressor to enter an 'unloaded' stage. In this stage, the compressor continues to run but stops pumping air into the reservoirs. This prevents over-pressurization of the system and reduces wear on the compressor, conserving energy until the pressure drops again.

Question 3

Between what two pressures should reservoir pressure be maintained?

Accepted Answer

80 (552 kPa) psi to 135 psi (930 kPa).

Answer

For most heavy-duty vehicles equipped with air brakes, the air pressure in the reservoirs should be maintained within a specific operational range to ensure sufficient air supply for safe braking. This range typically falls between 80 psi (552 kPa) and 135 psi (930 kPa), which is crucial for vehicle safety and regulatory compliance.

Question 4

When conducting a build-up test on the compressor, what pressure do you start at?

Accepted Answer

50 psi (345 kPa).

Answer

When conducting an air compressor build-up test, the procedure typically begins with the air pressure in the system at a specific low point. Starting at 50 psi (345 kPa) allows for an accurate measurement of how quickly the compressor can build pressure to the governor cut-out point, ensuring it meets minimum performance standards and verifies its efficiency.

Question 5

What is the lowest pressure at which the governor should trigger the compressor to resume its pumping phase?

Accepted Answer

80 psi (552 kPa).

Answer

The air brake system's governor is designed to control the compressor's operation, ensuring adequate air pressure. It should trigger the compressor to resume pumping air into the reservoirs when the pressure drops to approximately 80 psi (552 kPa). This 'cut-in' pressure ensures that there is always sufficient air for safe braking, preventing the pressure from falling too low.

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FREE Air Brake MCQ Question and Answer