Crank case safety arrangements

 

Basic rules of crank case Safety arrangements

• Crank case and inspection door should be exhibiting strengthen construction.
• Should be fitted with one or more non return  relief  valves in each cylinder of crank case. And these valve should be arranged as their outlets protected from flame discharge in case of explosion 
• Total clear area  through the relif valves should not less than 9.30cm2/m3 gross crankcase volume.
• If engine is  not more 300mm cylinder bore with strongly constructed crankcase. 
• If such engine not more than 150mm cylinder bore. No needs to fitted with relief valves.
• Lub oil drains pipe from the sump to drain tank must be extended to well below the working oil level in the tank.
• If multiple engine installation. Drain and vent  arranged  so that flame of explosion can't pass from one engine to another engine.
• Diaphragm must be fitted near mid length to prevent the passage of flame.if the engine having more than 6 cylinder. 

Centrifugal pump troubleshooting

 Doesn't Deliver liquid

•  Priming liquid is insufficient.
• Pump speed is insufficient.
• Discharge pressure is excessive
• Direction of rotation is wrong
• Suction line ruptured
• Pressure loss in suction.

Insufficient capacity, crackling noise from the pump casing,

• Air leaking in suction line 
• Pump speed is insufficient
• Suction lift is excessive
• Clogged in impeller passage
• Worn wearing or impeller or stuffing box packing or sleeves 

Doesn't develop enough discharge pressure

• Speed of the pump is insufficient.
• Air or gas in the liquid being pumped.
• Mechanical defects such as worn in wear rings or Leak in seals , impeller damage,

Working for while and suddenly fails to deliver liquid

• Air leaking in suction line .
• Air leaking in stuffing box
• clogged water seal passage.

MOTOR NAME PLATE DETAILS MMD ORALS

1.  Rated full load current.
2. Ip number (indicated the degree of protection)
3. Rated speed.
4. Rated frequency
5. Rated voltage
6. Power rating
7. Type 
8. 3phase indication motor 
9. Connection (delta)
10. Weight
11. Serial number
12. Bearing (drive end non drive end)

EARTH FAULT mmd oral

1. 440v Earth fault is considered as a emergency onboard 
2. For some ships have trips for 440v earth faults.
3. For 3000v and  above its mandatory to to fit the trip protection against earth fault.

How to find the earth fault in 440v?

• When you hear the earth fault alarm, inform the electrical officer if he is board.
• Check the alarm, sometimes false alarm will rise. Test the alarm using test button,
• Or if we have integrated automation system, we can check by  software.
• Now isolate the whole 440v system (but its not possible to isolate 440v, is because some machinery can not we isolate like steering gear & lub oil pumps. 
• So we can use standby options. 
• Keep checking on the system one by one, we will find the earth fault machinery.

HOW WILL YOU FIND THE EARTH FAULT IN 220 V?

•  For 220 v earth fault is not consider the major emergency onboard. But any way we have to find the faulty lighting circuit.
• First of all check the alarm which is working properly or not using test button.
• Then isolate the whole lighting system.check the it one by one.using breaker.
• For after finding the the particular area of earth fault in 220v.
• We will check the particular section one by ine circuits.
• Finally we will found the earth fault .

Eart fault detected why we are isolating  system?

•  To Prevent from over heating 
• To prevent from  short circuit.

FUSES meo class4

 Types of fuses

•  High reputuring  capacity fuses.
• Cartridge fuse 
• Semi enclosed fuse.

SURVIVER MAY ASK HOW WILL YOU ORDER FUSES?

•  CURRENT RATING
• VOLTAGE
• BREAKING CAPACITY
• FUSE TYPE 
• FREQUENCY
• PRODUCT TYPE.

CIRCUIT BREAKER ACB meo class4

 MCB - Miniature circuit breaker- 5- 50 amp

MCCB -  moduled case circuit breaker 50-1500amp

ACB- Air Circuit breaker- 400-2000amps

Acb safeties 

• Arc runner arc chutes 
• Breaker open fast before taking out acb 
• Simultaneous closing of all 3 units of each phase.
• Breaking speed as High as possible.