What is the brake cylinder pressure after a full service reduction with a brake system charge to 90 psi?

To determine the brake cylinder pressure after a full service reduction in a train with a brake system charged to 90 psi, it’s essential to understand the relationship between the brake pipe pressure and the brake cylinder pressure during braking operations.

When a full service reduction is made, the brake pipe pressure drops, which in turn causes the pressure in the brake cylinders to increase. The exact pressure in the brake cylinders is derived from the brake pipe pressure minus a certain pressure loss due to the system's inefficiencies and design parameters. Typically, after a full service reduction with a standard train operation, the brake cylinder pressure will be around 70% to 80% of the original brake pipe pressure.

In this scenario, if the system is charged to 90 psi, performing a full service reduction usually results in a brake cylinder pressure that can often be approximated or calculated based on standard operational figures. The answer of 64 psi likely reflects this calculation, as it falls within the typical range expected after a service reduction, adhering to industry standards for brake performance.

In summary, 64 psi is a reasonable figure arrived at through understanding the operational mechanics of air brake systems during a full service reduction.