The device shown in the illustration may be closed by using pressurized air on some recently built large low speed engines and would replace the component identified as ____________. See illustration MO-0066.
• Study how the valve is forced closed in this mechanism (what provides the closing force?). • Notice which labeled parts are springs and which are hydraulic pistons or guides. • On some large low-speed engines, a pressurized air “spring” replaces the mechanical spring that normally closes the valve.
• First, decide whether the question is talking about the exhaust valve assembly on the left or the fuel valve/injector on the right. Which one is normally opened hydraulically and closed by a spring? • Look along the valve stem and ask: which labeled part is clearly the coil spring that pushes the valve closed when hydraulic pressure is removed? • Compare the two visible springs in the figure. Which one directly acts on the main exhaust valve head, and which one acts on a smaller internal part in the injector body?
• Identify which letter points to the main mechanical closing spring for the exhaust valve (not the stem, seat, or guide). • Verify that the component you choose is actually a spring providing closing force, not just a guide, collar, or hydraulic piston. • Make sure your choice is the part that would logically be replaced if the closing function were provided by pressurized air instead of a metal spring.
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