- Close the section isolating valve, this will raise an alarm indicating zone isolation
- Now, open the test valve, if no water comes out, then it means the NR valve placed after the section isolating valve is not leaking.
- Since, the section after the NR valve remains pressurized, opening of the drain valve will cause the water pressure in the section line to decrease. A pressure switch sensor senses the decreased pressure & raises an alarm.
- Now, close the drain valve, open the section isolating stop valve. To check the flow switch, open the flow test switch to activate an alarm.
- Allthe above alarms will be indicated on the navigation bridge, E/room as well as in the Fire Control Room. The alarm will also indicate the particular zone from where it has risen.
- Ifall the alarm conditions are satisfied, close all the testing valves, open the section isolating valve, purge the sprinkler line by air and again keep the line pressurized. Check from the pressure gauge, that proper pressure has been maintained or not
1. High cost: Manganese bronze is a costly alloy, making it less economical for large propellers. 2. Low strength-to-weight ratio: Compared to other propeller materials like nickel-aluminum bronze or stainless steel, manganese bronze has a lower strength-to-weight ratio. 3. Susceptible to corrosion: Manganese bronze can corrode in seawater, especially when exposed to high velocities and turbulence. 4. Poor cavitation resistance: Manganese bronze is more prone to cavitation damage than other materials. 5. Difficult to cast and machine: Manganese bronze is challenging to cast and machine, making it less desirable for complex propeller geometries. 6. Limited weldability: Manganese bronze has poor weldability, making repairs and modifications difficult. Nickel-aluminum bronze or stainless steel are commonly used for propellers due to their: - High strength and durability - Excellent corrosion resistance - Good cavitation resistance - Ease of casting and machining - Weldability
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