- Minimum 2 number of blower to be fitted in I.G system.
- The capacity of each blower must be 1.25 times the overall capacity of the cargo discharge system fitted on board. This is to ensure that Inert Gas is always present in the cargo hold.
- Only 1 blower may be permitted by the administration if it fulfills the requirement stated in above point i.e. capacity must be 1.25 time cargo pumps and required spares are always available.
- A shut off arrangement must be provided in the suction and discharge connection side of the blowers.
- Generally the blowers are used for gas freeing hence an n air inlet with blanking arrangement must be provided. At normal operation, blanking arrangement is to be secured.
- Cargo tanks are pressure tested at 2500 mm water gauge and 700mm water gauge on the vacuum side. The blower pressure must not exceed the test pressure else the tank will get damage.
- Minimum pressure to be maintained by blower is 200 mm water gauge in cargo tank.
- There must be high temperature alarm (@ around 65 deg c) and a high temperature trip (@ around 75 deg c) to safeguard the blower.
- The driving media for blower can be either steam or electrical power.
- The blowers must be located at aft of the cargo tanks and cargo pump room of the ship.
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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