During a minimum brake pipe reduction, how many psi is reduced?

During a minimum brake pipe reduction, how many psi is reduced?

• A. 4-6 psi
• B. 2-4 psi
• C. 6-8 psi
• D. 8-10 psi

Answer: (C)

In an air brake system, brakes are applied by lowering the brake pipe pressure. The minimum brake pipe reduction is the smallest drop that will reliably produce a service brake application across the train. Six to eight psi is used as the standard minimum because this amount is large enough to overcome tolerances, temperature effects, and minor leaks so every brake cylinder can receive enough air to apply smoothly and consistently. Drops of only two to four psi can be insufficient for a reliable, uniform application, while larger drops risk triggering an emergency brake or causing excessive braking. So, six to eight psi best fits the requirement for a minimum, reliable service brake application.

In an air brake system, brakes are applied by lowering the brake pipe pressure. The minimum brake pipe reduction is the smallest drop that will reliably produce a service brake application across the train. Six to eight psi is used as the standard minimum because this amount is large enough to overcome tolerances, temperature effects, and minor leaks so every brake cylinder can receive enough air to apply smoothly and consistently. Drops of only two to four psi can be insufficient for a reliable, uniform application, while larger drops risk triggering an emergency brake or causing excessive braking. So, six to eight psi best fits the requirement for a minimum, reliable service brake application.