The freshwater cooling systems serving the main engines on your fishery research vessel are arranged as shown in the illustration. If the fresh water thermostatic control valve fails in the position where 100% of the flow from flange "A" is permanently ported to flange "C" and flange "B" is permanently blocked, while starting and warming the engine with no load, what would be the resulting warm up time period? Illustration MO-0137
• Flow paths between flange A (from engine), B (to heat exchanger), and C (bypass/return) in the thermostatic valve • How a thermostatic control valve normally regulates jacket water temperature during warm-up • Effect of bypassing the heat exchanger on engine warm-up time when the engine is at no load
• Trace the coolant path on the diagram for both NORMAL operation and the FAILED condition described. Where does the hot water from the engine actually go in each case? • Think about heat transfer: if the coolant does or does not pass through the raw‑water/fresh‑water heat exchanger during warm-up, what happens to how quickly the jacket water temperature rises? • During no‑load operation, is the engine generating more, less, or the same amount of heat compared to loaded operation, and how does that interact with increased or decreased cooling?
• Be sure which flange, B or C, connects to the raw water/fresh water heat exchanger and which one is a bypass/return line back toward the expansion tank/engine. • Confirm whether, in the failed position, any flow from flange A is going through the heat exchanger or if it is all being bypassed. • Ask yourself: with cooling reduced or eliminated at low load, would the jacket water tend to warm slower, the same, or faster than when cooling is working normally?
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