Marine Knowledge

سلام عرض ادب و احترام خدمت همکاران و بزرگواران اگر اینترنت ملی شد و تلگرام از دسترس خارج شد سعی میکنم تمام مطالب و جزوه ها و کتب رو انتقال بدم به کانال ربیکا تو این کانال عضو بشید تا همیشه مطالب در دسترس شما قرار بگیرد هر کجا که هستید موفق باشید و پیروز https://rubika.ir/Marineer

Navigation Equipment 1. Steering wheel  2. Gyro repeater  3. Magnetic compass  4. Telegraph  5. Radar  6. ARPA  7. SART  8. VHF  9. Clear View Screen  10. Anemometer  11. Tachometer  12. Rudder Angle Indicator  13. EPIRB  14. Alarm panel  15. GPS  16. Aneroid Barometer  17. Inclinometer  18. Navtex  19. Fire detector  20. General alarm  21. Echo sounder  22. Course recorder  23. Public address System  24. ECDIS  25. VDR 26. Bridge navigational watch alarm system 27. Binoculars  28. Ship Security Alert System  29. Portable two way VHF GMDSS 30. INMARSAT C 31. MF / HF RADIO  32. CHRONOMETER  @Marine_Engineer

Reasons for Failure and Misalignment of Crankshaft in Marine Engines Crankshaft is the intermediate part of a marine engine, which transfers the power of a firing cylinder from the reciprocating piston to the rotating propeller (or alternator in case of a generator). The working of other components of the engine depends upon the correct rotation of the crankshaft such as camshaft for fuel timing, firing order of units etc. Failure of a single part of the crankshaft can stall the engine as well as the ship. As a marine engineer working on a ship, one should know various reasons which can lead to failure of this important component. Reasons for failure of crankshaft *Fatigue Failure: Majority of steel crankshaft failure occurs because of fatigue failure, which may originate at the change of cross-section such as at the lip of oil hole bored in the crankpin. *Failure due to Vibration: If the engine is running with heavy vibration especially torsional vibration, it may lead to crack in the crankpin and journal *Insufficient lubrication: If the lubrication of bearing in the crankshaft is starved, it may lead to wipe out of the bearing and failure of the crankshaft *Over Pressurised Cylinder: It may happen that there is hydraulic lock (water leakage) inside the liner and due to extreme pressure the crankshaft may slip or even bent (if safety valve of that unit is not working). *Cracks: Cracks can develop at the fillet between the journal and the web, particularly between the position corresponding to 10 o’clock and 2 o’clock when the piston is at T.D.C. -Reasons for Crankshaft Misalignment Crankshaft of a marine engine is a massive component when fully put together in the engine. Initially the complete crankshaft is aligned in a straight line (connection drawn from the centre of the crankshaft makes a straight line) before setting it on the top of main bearings. But with time due to various factors, the straight line may deviate and misalign. A degree of misalignment is acceptable within limits but if the value goes beyond that rated by the manufacturer; it may lead to damage or even breakage of the crankshaft. Following are the reasons for misalignment of crankshaft- *Damage or wipe-out of the main bearing *Loose engine foundation bolt leading to vibration *Deformation of ship’s hull *Crack in the bearing saddle *Loose main bearing bolt leading to damage of main bearing *Very high bending moment on the crankshaft due to excessive force from piston assembly *Grounding of the ship *Crankcase explosion or fire *A defective or worn out stern tube or intermediate shaft bearings *Loose or broken chokes in the foundation *Bearing pockets cracked *Bedplate deformed – transverse girder damaged *Tie bolts slack or broken *Weakening of structure due to corrosion

Air Compressor Unloader Valve: Its Purpose A reciprocating air compressor is a positive displacement mechanical device that relies on a cylinder and crankshaft-driven piston to produce compressed air. An unloader valve is one of the many small but essential parts and components that ensure the effective, efficient operation of a reciprocating compressor. What Is the Unloader Valve? A compressor unloader valve is a small part, typically measuring approximately 4-5 inches in length and width. It performs the critical function of releasing trapped air inside the tank, enabling the motor to restart. An unloader valve malfunction is one of the more common air compressor issues. If the trapped air cannot escape, the accumulated pressure may be enough to keep the motor from restarting. The type of unloader valve found in an air compressor depends on the machine’s make and size. Some operate via a toggle switch on the side of the unit’s pressure switch. Others have an integral valve installed under the pressure switch. What Is the Purpose of an Unloader Valve? During the operation of a typical reciprocating air compressor, the machine’s electric motor-driven tank fills with air. The device contains a pressure switch that responds to the air accumulation by shutting off the motor’s power supply. The compressor pump, which is attached to the motor shaft, also stops. When the motor attempts to restart, the air trapped inside the cylinder generates a load that makes it more challenging to execute the task. By venting the air, the unloader valve reduces the load over the piston, facilitating the restarting process. Where Is the Unloader Valve Located? If you own a smaller reciprocating air compressor, you’ll likely find the unloader valve mounted on or inside the pressure switch. When the switch shuts the compressor off, it actuates the valve. A small tube or pipe runs from the check valve, a device that keeps the entire tank from draining, to the unloader valve. A larger air compressor often features a more sizeable unloader valve controlled by air pressure emanating from a smaller pilot valve. In this arrangement, the valve typically sits next to the compressor. How Does an Unloader Valve Work? When the air pressure inside the compressor’s tank reaches the pressure switch’s cut out pressure (the point when air is no longer delivered), the switch automatically trips off and interrupts the power supply to the motor. This process causes the unloader valve to open and vent the accumulated air. When the tank pressure drops back down to the predetermined setting on the pressure switch, it causes the switch to trip again. This action results in the release of the unloader valve’s pin, preventing the escape of compressed air into the atmosphere.

10 Precautions to Take Before Operating Controllable Pitch Propeller (CPP) on Ships The driving force of a ship comes from the rotation of propeller(s), which is attached to the main engine of the ship. The two main types of propellers that are used in merchant vessels are: 1. Fixed Pitch Propeller (FPP) 2. Controllable or Variable Pitch Propeller (CPP) As the name suggest, in fixed pitch propeller, the blades are fixed with the propeller boss and hence their pitch cannot be changed. However, in Controllable or Variable Pitch Propeller (CPP), the propeller blades are attached to the boss and their pitch can be altered via the hydraulic system. Both the types of propeller systems have their own advantages and disadvantages. In Controllable Pitch Propeller (CPP), the main engine can be started with blade pitch set to 0. This decreases the fuel consumption and also reduces the load on various engine bearings and its shafting during the starting procedure. If you are working on a ship with a Controllable Pitch Propeller (CPP) drive, do ensure to take the below mentioned precautions before operating it: 1. Operation from Remote Position: Operate the CPP from Remote control position for ahead, astern and stop position and check the pitch position indicator located near the stern shaft. 2. Operation from Emergency Position: Operate the CPP from Emergency control position which is located near the stern shaft for ahead, astern and stop position and check the pitch position indicator. 3. Check for Leakages: Ensure their is no oil leakage from the system. Even a small leakage can lead to failure of the system at later stage of operation. 4. Maintain the oil level: Check and maintain the oil level in the hydraulic tank of the system at all times. Also, ensure that all the alarms in the tanks are in working condition. 5. Check the pressure: Ensure their is no loss of pressure once the desired angle of pitch is achieved. 6. Start The Engine At Zero Pitch Angle: Always start the main engine at zero pitch angle as their will be a zero propeller resistance during the start, leading to less load on the shaft bearings. 7. Check all the Parameters: Check all the parameters of the main engine are within limits and check the temperature of all bearings including the shaft bearings. 8. Carry out Hydraulic Oil Analysis: Analysis of hydraulic oil used in the Controllable Pitch Propeller (CPP) system to be carried out onboard to check the condition and water intrusion. 9. Run Engine At Constant Speed: If shaft generator is fitted with power Take off/ Gear constant ratio for power production, the engine with CPP should be run at constant speed even at reduced load. This will ensure the efficiency of Controllable Pitch Propeller (CPP) and engine is maintained. 10. Perform Frequent Overboard Checks: Frequent overboard checks near the stern area to be performed during starting of the Controllable Pitch Propeller (CPP) for oil leakage from the sealing ring. Controllable or Variable Pitch Propeller (CPP) eases the use of other fuel efficient machinery such as shaft generator and also reduces load on the ship’s engine. It is a complex and expensive installation as compared to the Fixed Pitch Propeller (FPP) and hence engineer officers onboard must be skilled enough to ensure no breakdown takes place by knowing the system inside-out.

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