What should be done after closing the branch pipe cutout cock when cutting out a control valve?

Answer: B — Drain the air reservoirs completely

When a control valve is cut out by closing the branch pipe cutout cock, the next step should be to drain the air reservoirs completely. This action is essential because it ensures that the air pressure in the system is safely and effectively managed. By draining the air reservoirs, you reduce the risk of pressure build-up that could lead to unsafe conditions or equipment damage while maintenance or inspection is being performed. The process of draining the air reserves is a precautionary safety measure to maintain control over the air system's pressure. This practice helps ensure that the components are functioning properly and reduces the likelihood of any accidental releases of air that could occur if the system were to remain pressurized. Proper pressure management is crucial in air brake systems, as it directly contributes to the safe operation of trains. This procedure also enables maintenance personnel to inspect and service the control valve effectively, knowing that the associated pressure is diminished. Such maintenance protocols adhere to safety standards and practices that are critical in railroad operations.