Marine Engineering

A ship will be subject to the following surveys: Initial survey before the ship is put into service Renewal survey at intervals not exceeding five years Annual survey within 3 months either way of the anniversary date of the load line certificate.  The   surveyor will endorse the load line certificate on satisfactory completion of the annual survey. The period of validity of the load line certificate may be extended for a period not exceeding 3 months or the purpose of allowing the ship to complete its voyage to the port in which it is to be surveyed.  Load Line Certification(5 years): All ships must be issued with a load line certificate for a period specified by the administration, which shall not exceed 5 years from the date of issue.  The form of the certificate will depend upon the  Assigning Authority as follows:  If the certificate is an International Load Line Certificate it shall be in the form prescribed by  the 1966 Convention...

Close the water and steam cocks on the gauge glass and open the drain. Then open the steam cock-a strong jet if steam should be seen from the drain. Close the steam cock. Open the water cock-a strong jet of water should be observed from the drain. Close the water cock and then close the drain. Then open the water cock, the water will rise in the gauge above the normal level. Then open the stem cock, the water should then settle down, finding its correct level.

Prior to a ship's departure from any port, the steering gear should be tested to ensure the satisfactory operation.  This tests should include, Operation of the main steering gear Operation of auxiliary steering gear or the use of the second pump which acts as an auxiliary Operation of the remote control system from the main bridge steering positions Operation of steering gear using the emergency power supply The radar angle indicator reading with respect to actual radar angle should be checked The alarms fitted to the remote control system and steering gear power units should be checked for correct operation. Steering gear header tank levels should be checked. During these tests the radar should be moved through its full travel in both port and starboard and the various equipment items, linkages etc visually inspected for damage or wear. The communication system between the bridge and steering gear room should also be checked.

An option available to reduce the specific fuel consumption of diesel engines is derated or so-called "economy" ratings . This means an operation of an engine at its normal maximum cylinder pressure for the design continuous service rating, but at lower mean effective pressure and shaft speed. By alternating the fuel injection timing to adjust mean pressure/ maximum pressure relationship the result is a worthwhile saving in fuel consumption. The horsepower required for a particular speed by a given ship is calculated by the naval architect and once the chosen engine is coupled to a fixed pitch propeller, the relationship between engine horsepower propeller revolutions and ship speed is set according to the fixed propeller curve.   A move from one point on the curve to another is simply a matter of giving more or less fuel to the engine.  Derating is the setting of engine performance to maximum cylinder pressure at lower than normal shaft speed...

Bunkers should not be taken when the ship is on the blocks. In cases where ships sail out immediately after dry-docking. Bunker is to be supplied after the ship has undocked and is floating. Shore power cables are to be connected after the ship has docked and the dock is dry. The cables should be disconnected before flooding the dock. During the flooding of the dock, the flooding is stooped when the level of water in the dock reaches just above the high suction box. All the sea suction valves under the floor plates should be checked for any leaks. In this situation, the ship is not floating and is still sitting firmly on the blocks. This verification is necessary to avoid any mistakes made by shipyard staff whereby some valves have not been fitted their cover joint sand gland packings. A second docking can be avoided by this check. The Master and C/E should visit the dry dock before flooding and verify the following before giving orders for flooding:  ...

Soft foot is a common term used for machine frame distortion. The distortion is caused when one or more feet of a machine differ in height from the others. This, in turn, may be due to differences when the machine was manufactured, a squishy footage with oil film etc. between foot and base, a bent foot, or it may be induced by a pipe to which the machine is attached (e.g. a pipe on top of a pump), which prevents the machine from touching all its feet to its base. Types of Soft Foot Air Gap or Parallel Soft Foot: The most common explanation of soft foot is parallel or straight soft foot. When the hold-down bolt is loose, the foot simply does not reach the base, leaving a gap between the foot and the base. The bottom of the foot is parallel to the baseplate though. This condition is easiest to detect using either a feeler gauge or dial indicator. Downward Bent Foot: A common situation is known as a bent foot. Here the foot is touching the base on the outside portion, but t...

One of the most important parts of pump setup is making sure that the pump and the drive motor are carefully aligned. Misalignment may account for over 50% of malfunctions in rotating machinery, leading to problems such as worn or broken couplers, vibration, and excessive wear of bearings, seals and wear rings. Excessive misalignment can even cause breakage of mounts or pump/motor casings. Once the pump set has been properly installed, the final alignment can be checked and, if necessary, corrected. Obviously, re-alignment is needed whenever the pump or motor are moved or replaced. What do we mean by ‘alignment’? Long-coupled pumps have a separate pump and motor shafts that are connected through a coupler. Ideally, these two shafts will be exactly parallel and have exactly the same centre-line. Flexible couplers can tolerate small alignment errors, but for smooth, trouble-free running, it is important to ensure that these two shafts are lined up to within the tolerances specified...

There are two methods to reduce NOx emissions; Primary and secondary measures.  Primary measure aim at reducing the amount of NOx formed during combustion by optimizing engine parameters with respect to emissions. As read in previous article , the  main factors influencing NOx formation  are the concentrations of oxygen and  nitrogen and the local temperature in  the combustion process. Therefore,the  primary measures focus on lowering the  concentrations, peak temperature and the  amount of time in which the combustion  gases remain at high temperatures. Miller cycle is employed in 4-stroke  engines. It uses higher than normal  pressure turbocharger. The inlet valve is  closed before the piston reaches bottom  dead center on the intake stroke. The  charge air then expands inside the engine  cylinder resulting in reduced temperature. On the other hand, secondary measures remove NOx from the exhaust ga...

Nitrogen oxides are the major air pollutants and pose a challenge to engine manufacturers to meet the limits set forth by the MARPOL Annex VI.  Combustion of fuels is the primary anthropogenic source of formation of nitrogen oxides, While Nitric oxide (NO) and nitrogendi-oxide are usually grouped together as NOx emissions, nitric oxide is the predominant oxide of nitrogen produced by combustion process. Therefore, it is an important minor species in the combustion because of its contribution to air pollution.  The principal source of NO is the oxidation of atmospheric (molecular) nitrogen. However, if the fuel contains  significant  nitrogen, the oxidation of the fuel nitrogen-containing compounds  is an additional source.  In the combustion of fuel that contains  no nitrogen , nitric oxide is formed by  three chemical mechanisms  that involve nitrogen from the air.  The  three principal mechanisms are: i) The th...

MARPOL Annex VI requires all diesel engines installed after 1st January 2000, with a power output of more than 130 kw to be tested and issued with an Engine International Air Pollution Prevention (EIAPP) certificate and an approved NOx Technical File.  The approved Technical File provides details of the allowable engine components settings, operating values and allowable adjustments which ensure the engine will continue to operate within the acceptable NOx emission limits.  This EIAPP certificate and approved Technical File stays with the engine and remains valid for its marine life.  Periodic verification surveys are carried out by the classification to confirm the engine continues to operate within the on-board NOx emission limits. If any adjustment, part replacement and modifications are carried out, which influences NOx emission characteristics should be recorded chronologically in an engine’s record book of engine parameters. ID numbers of all such compon...

In order to reduce the harmful effects on the marine environment that are spread through aquatic micro organisms transferred from one area to another through ballasting operations of the ship, the International Maritime Organization (IMO) adopted a convention in order to control and manage ships ballast and sediments ion on 13th February 2004. Which entered  into force on 8 September 2017. Port state authorities from around the world implemented their own requirements for ballasting and de-ballasting operation for ships sailing in their terrestrial water. To simplify the requirement of the control of ballast water problem, a “ballast water management plan” was introduced which was to be used and implemented on board sailing vessels entering international waters. Contents of Ballast Water Management Plan: The ballast water management plan includes the following: International rules and regulations for different port state controls all over the world. Location of ports p...

The manufacturer of the equipment should submit information regarding the design, construction, operation and functioning of the ballast water management system. This information should be the basis for a first evaluation of suitability by the Administration. The ballast water management system should be tested for type approval; the testing body performing the tests should have implemented appropriate quality control measures acceptable to the Administration. The electrical and electronic section of ballast water management systems should be subjected to the programme of environmental tests set out in Guidelines (G8) at a laboratory approved for the purpose by the Administration. Successful fulfilment of the requirements and procedures for type approval should lead to the issuance of a Type Approval Certificate by the Administration. When a type approved ballast water management system is installed on board, an installation survey should be carried out. It should be noted t...

Purpose of boiler water treatment Prevent corrosion of boiler tubes and shell Prevent scale formation and hence maintain heat transfer rates. Control sludge formation within the boiler. Control foaming and priming. Prevent entry of foreign matter, oil etc. into the boiler via feed system Extend boiler survey to the maximum allowed. FOLLOWING TESTS ARE CARRIED OUT:- Boiler water tests are therefore done to ensure that the chemical levels are maintained as required. Chlorides : This is a measure of presence of Chlorides, usually an indication of contamination of Boiler water with sea water.( Sodium Chloride / Calcium or Magnesium Chloride ) . This results in increased scale formation, acidity and boiler priming.  Normal levels: Chlorides < 300 ppm.   What to do if chloride content increases beyond normal value.? Check for leakages of SW into the system, mainly from atmospheric condenser leak and rectify any leaks found. Blowdown at regular...

Synthetic Lube Oil Mineral Lube Oil Synthetic oils can be a amalgamation of man-made oil + mineral oil or fully man made oil. Mineral oil is basically a derivative of petroleum products which is then refined to its usable form.  Expensive as compared to mineral oil. Less expensive Can withstand high temperatures. Can’t withstand high temperature They are the best, they provide highest level of protection for engine components. They provide the least protection to engine components. Can withstand high temperature & Lasts much longer than mineral oil. Can’t withstand high temperature Synthetic oils do not allow engine components to wear as much as mineral oil thus they are not suitable during break in periods. Suitable for machinery having break in periods. Since it allows engine components to wear evenly

Super long stroke means increased swept volume allowing more mass of air to be drawn into the cylinder which in turn allows more fuel to be burnt, hence increasing power output. Super long stroke increases piston travel time and thereby decreases crank speed so more time for combustion during the stroke. The efficiency of Large dia propellers is best at slower RPM.With super long stroke we can have slower RPM of engine with no change in mean piston speed of the engine. Classification of engine based on stroke/bore ratio: Short stroke : 2.6-3.2 Long stroke : 3.2-4.0 Super-Long stroke : 4.0-4.7 Ultra-Long stroke : >4.7 These engines allow for low quality of fuel to be burnt as there is more time available for fuel combustion. With increase in stroke length we have an advantage of burning dirty fuel/low grade fuel at min rev/low speed with good efficiency. This also results in proper utilization of fuel resulting in reduction of NOx generatio...

• If the Generator has been running, allow it to cool down before opening the crank case doors. • Check the visual condition of crank case walls and the crankshaft and lube  Oil. If the crank case and the oil is black, it means that there is blow past of some units. • Pump out the crank case oil in a drum or whatever arrangements are provided. • Test the oil with the lube  oil testing kit provided on board. • Look for any signs of jacket cooling water leakage in crank case. In doubt, pressure test the system by connecting a hydraulic pump to the inlet of the cooling water and keeping the outlet from the engine shut. • Look for any signs of wiped bearings. • Check the tightness of Main bearing bolts, Crank pin bearing bolts and ensure that all the lube  oil connection pipes in the crank  case are tight. • Check that the crank pin bearing is  floating on the pin.i.e. you should  be able to move the crank pin  bearing side wa...

The Piston is subjected to compressive and tensile stress caused by the bending action due to gas forces and thermal loading. When a piston crown is subjected to high thermal load, the material at the gas side attempts to expand but it is partly prevented by the cooler material under it. This leads to compressive stress in addition to the stress imposed mechanically due to variation in load at the time of compression / ignition stroke and exhaust / inlet stroke of the piston. At very high temperature, the metal can creep to relieve these compressive stresses and when the piston cools, residual tensile stress is set up, hence residual thermal stress. If this stress is sufficiently great, cracking of the piston crown may result

Interlocks are provided so that the engine can be started or reversed only when certain conditions have been fulfilled. (a) TURNING GEAR INTERLOCK :- It prevents the engine from being started if the turning gear is engaged. It blocks the starting air from reaching the engine. (b) RUNNING DIRECTION INTERLOCK :- It prevents the fuel from being supplied, if the running direction of the engine does not match the Telegraph. An interlock also prevents starting of the engine if an attempt is made to start the engine before the reversing has been completed. (c) PARAMETERS REQUIRED MINIMUM :- All the important parameters like Lub. Oil pressure, Cooling water pressure, etc should be above min. required value. (d) AUXILIARY BLOWER INTERLOCK :- Aux. Blower is provided for constant pressure turbo charging. It should be in auto before engine can be started. (e) AIR SPRING PRESSURE INTERLOCK:- If the Exhaust valves are operated by air spring pressure, there should be suffici...