Question 25 UFIV01 - Chief Engineer - UFIV
The fishing industry factory ship to which you are assigned has a pneumatic propulsion control system as shown in the illustration. Which control valve is responsible for bypassing the inflation delay orifice to insure rapid and positive reversals and to protect the clutches from excessive slip? Illustration MO-0167
The Correct Answer is C The **H5 boost relay air valve** (Option C) is the component specifically designed to bypass the normal restriction (inflation delay orifice) during rapid maneuvers, such as reversing the direction of the propeller. The primary function of the delay orifice is to slow down the inflation of the pneumatic clutch to allow for smooth engagement under normal operating conditions. However, during rapid reversals, this slow engagement would cause excessive clutch slip, leading to overheating, wear, and potential failure. The H5 boost relay valve senses the demand for rapid change (often triggered by high pressure from the propulsion control system) and momentarily supplies high-volume, unrestricted air ("boost") to quickly and positively engage the clutch, minimizing slip and protecting the clutch components. **Why the other options are incorrect:** * **A) H5 inflation air relay valve:** While the H5 inflation relay valve controls the primary flow of air into the clutch, it generally operates in conjunction with the delay orifice to ensure smooth, slow engagement during normal acceleration or standard maneuvering. It is not the specific valve responsible for the *bypassing* or "boost" function during rapid reversals. * **B) C2 speed-slip relay valve:** The C2 speed-slip relay valve is typically involved in monitoring the rotational speeds of the input and output shafts (or propeller shaft) and adjusting the clutch pressure to minimize sustained slip under normal load conditions, often to protect the clutch from overheating, but it is not the valve that provides the rapid pressure boost for immediate engagement during reversals. * **D) H5 governor limit relay air valve:** The H5 governor limit relay valve is usually involved in limiting the maximum speed or power output of the engine or propulsion system under certain conditions (e.g., preventing overspeed or limiting torque). It does not function as the specific bypass valve for quick clutch engagement during reversals.
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