What is the preload charge for the emergency brake accumulator?

• A. 1000 PSI + or - 100
• B. 500 PSI
• C. 2000 PSI
• D. 0 PSI

Answer: (A)

The concept being tested is how much preload pressure an emergency brake accumulator should have. The preload charge is the fixed initial pressure stored in the accumulator so there is immediate, ready energy to actuate the brakes when an emergency is called for. For this system, the preload is set around one thousand psi with a tolerance of about one hundred psi. This level provides enough stored energy to deploy the brake quickly and effectively, while staying within the system’s design limits. A preload of about five hundred psi would likely be insufficient to fully actuate the emergency brakes; a preload around two thousand psi could exceed safe operating pressures and cause wear or damage; and a preload of zero would leave no stored energy, defeating the purpose of the accumulator.