What is the first step to test the tractor protection valve?

The first step in testing the tractor protection valve is to charge the air brake system. Doing this ensures that the air tanks are filled with the necessary pressure so that the tractor protection valve has the correct operating conditions to be tested. The air brake system must be charged to an appropriate level, usually around 90-100 psi, to ensure that the system is functioning properly and can respond accurately during the test.

By starting with this step, you allow all components related to the air brake system to operate properly, enabling you to observe how the tractor protection valve reacts under normal conditions. This step is essential for conducting a thorough and effective test of the valve's performance.