Tuesday, August 18, 2020

Engine Balancing

  • To  make  small  adjustments  to  each  unit  make  uniform power  generation
    in every unit.
  • Pmax  by  timing  of  fuel  pump(vit  or  by  shims  to  pump  or  cam  floating
    and readjusting)
  • Pcomp in ME engines by exh valve timing change.
  • Pmax- Pcomp not more than 35 bar to avoid piston ring failure.
    Pi adjusted by fuel index.
    (But limits are The peak pressure difference can't be more than 3 to 5
    for AE And max 10 for ME. Exhaust gas temp diff 40deg C.
    Fuel  rack  should  not  be  adjusted  more  than  10% Otherwise  we  have  to
    change the plunger and barrel)

Saturday, August 15, 2020

Self locking nuts

  • lf-locking nuts provide tight connections that will not loosen under vibrations. 
  • They meet critical specifications as to strength, corrosion resistance, and heat-resistant temperatures. 
  • New selflocking nuts must be used each time components are installed. There are two general types of self-locking nuts. 
  • They are the all metal nuts and the metal nuts with a nonmetallic insert to provide the locking action.
  •  The elastic stop and the nonmetallic insert lock nut are examples of the nonmetallic insert type. 
  • All metal self-locking nuts are constructed either of two ways. The threads in the load-carrying portion of the nut that is out of phase with the threads in the locking portion is one way. 
  • The second way is with a saw-cut top portion with a pinched-in thread. The locking action of these types depends upon the resiliency of the metal.

Thursday, August 13, 2020

4 stages of Ship Construction at yard

  • The block stage
  • Pre-erection stage
  • Erection stage
  • Quayside and commissioning

Advantages of MLC

  • A comprehensive set of basic maritime labour principles and rights
  • Simplification of international requirements
  • A strong enforcement regime, backed by a certification system
  • Verifiable compliance with basic minimum employment and social requirements
  • Application to all ships including those of non-ratifying Members
  • Improved working and living conditions for seafarers
  • A more secure and responsible maritime workforce
  • A more socially responsible shipping industry
  • Improved social dialogue at all levels
  • Seafarers better informed of their rights and remedies
  • Improved supervision at all levels: the ship, the company, the flag state, the port state, and the ILO
  • Global and uniform compliance and verification
  • Improved possibilities of keeping labour conditions up to date
  • Permanent review of maritime labour situation
  • Positive impact on safety at sea
  • Positive impact on the protection of the environment

Wednesday, August 12, 2020

Angle of Repose

  • Angle of Repose is the maximum slope angle of non-cohesive (i.e. free-flowing) granular material
  • It is the angle between a horizontal plane and the cone slope of such material
  • The angle of repose is a characteristic of non-cohesive bulk cargoes, which is indicative of cargo stability, and the purpose of which is to minimize the risk of bulk material shifting; 
  • The cargo should be trimmed reasonably level to the boundaries of the cargo space
    Jn

Tuesday, August 11, 2020

Safe Manning

SOLAS CHAPTER V, REG 14
The principles of minimum safe manning set out in section 3 to ensure the safe operation of ships to which article III of the 1978 STCW Convention, as amended, applies, and the security of ships to which chapter XI-2 of the 1974 SOLAS Convention, as amended,
Principle:
The capability to
  •  Maintain safe navigational, port, engineering and radio watches in accordance with regulation VIII/2 of the 1978 STCW Convention, as amended, and also maintain general surveillance of the ship;
  •  Moor and unmoor the ship safely;
  •  Manage the safety functions of the ship when employed in a stationary or near-stationary mode at sea;
  • Perform operations, as appropriate, for the prevention of damage to the marine environment;
  • Maintain the safety arrangements and the cleanliness of all accessible spaces to minimize the risk of fire;
  • Provide for medical care on board ship;
  • Ensure safe carriage of cargo during transit;
  • Inspect and maintain, as appropriate, the structural integrity of the ship; and
  • Operate in accordance with the approved Ship's Security Plan; and
The minimum safe manning of a ship should be established taking into account all relevant factors, including the following
  • Size and type of ship;
  • Number, size and type of main propulsion units and auxiliaries;
  • Level of ship automation;
  • Construction and equipment of the ship;
  • Method of maintenance used;
  • Cargo to be carried;
  • Frequency of port calls, length and nature of voyages to be undertaken;
  • Trading area(s), waters and operations in which the ship is involved;
  • Extent to which training activities are conducted on board;
  • Degree of shoreside support provided to the ship by the company;
  • Applicable work hour limits and/or rest requirements; and
  • The provisions of the approved Ship's Security Plan

Sunday, August 9, 2020

Maritime TORTS and types

Maritime law torts is a term covering cases where injury, loss or damage is caused to a person or their interests by another party’s action or negligence.
Types of torts 3 types
Intentional torts
An intentional tort is a civil wrong that occurs when the wrongdoer engages in intentional conduct that results in damages to another.
Negligence
Careless conduct that results in damage to another is negligence
Strict liability
Generally, liability because of a tort only arises where the defendant either intended to cause harm to the plaintiff or in situations where the defendant is negligent.  However, in some areas, liability can arise even when there is no intention to cause harm or negligence.
For example, in most states, when a contractor uses dynamite  which causes debris to be thrown onto the land of another and damages the landowner’s house, the landowner

Saturday, August 8, 2020

Reamer and types

The function of a reamer is to produce a smooth accurate surface in a bore such as that of a bearing or bush, for the shaft, pin or bolt to enter with a very good fit. In engine room Reamers are used for
  • The stern tube hole in stern frame is cast/fabricate roughly under size. When Main Engine is aligned with centre line of the stern frame hole, this hole is reamed to required diameter to fit the stern tube.
  • Fitted bolts on rudder palm and rudder carrier bearing housing for the press fit. They are to be reamed to exact diameter to avoid relative movement.
  • If a hole is drilled for internal threads then before we start with the procedure of making threads (tapping) we have to make sure we get a smooth finish for the threads.
In this respect, a reamer is a much better tool than a drill and can also produce finishes superior to normal machining on lathes. In fact, bores machined on lathes are often finished with reamers to improve the surface and bring them to size. Holes to be reamed must be drilled or machined undersize, the amountof material left depending on the roughness of the surface. Reamers are reaming tools which can be used on lathe machine for drilling purpose.
Total 8 types of reamers are- Adjustable hand reamer, Straight reamer (precision), Hand reamer, Machine reamer, Shell reamer, Tapered reamer, Morse taper reamer & combination reamer.

Thursday, August 6, 2020

How will you repair the coating in FWG & what coating is there on FWG?

  • The internal of the Fresh Water Generator is coated with 2 layers of Nordtec Ceramic 2212 FDA (Food grade coating). 
  • It is developed for Freshwater generators. It is designed as an abrasion resistant and fluid flow ceramic coating. 
  • It coating is reinforced with ceramic and carbide particles to obtain a high level of abrasion and erosion resistance and physical, mechanical strength.
  • The outside of the Fresh Water Generator, is primed and coated with two component paint.
  • As per manual – shell is coated with Neoprene coating and top cover- pure epoxy coating & bottom cover- Neoprene coating

Wednesday, August 5, 2020

Ship security alarm system (SSAS)

International Maritime Organization (IMO) legislation states that the ship’s security alert system shall:
  • Be initiated by pressing a dedicated SSAS button and transmitting a ship-to-shore security alert to a competent authority designated by the administration, which may include the company, identifying the ship, its location and indicating that the security of the ships is under threat or has been compromised
  • Not send the ship security alert to any other ships
  • Not raise any alarm on board the ship, and
  • Continue the ship security alert until deactivated and/or reset.
SSAS is not part of the GMDSS communication requirements but its equipment can be used to support the system.
Ship security alerts can be sent using Inmarsat C and Mini C,
SSAS regulations is that security alerts are required to be routed only to the Company Security Officer and the Flag.
SSAS resetting after take over with change vessel particulars email address and flag contact address

Tuesday, August 4, 2020

Load line survey items in engine room

  • Ship side valves and distance pieces
  • Sounding pipes and its closing arrangement
  • Stern tube sealing
  • Rudder sealing
  • Duct keel manhole water tightness.

Monday, August 3, 2020

High voltage

Voltages up to & Including 1000V is known as Low voltage system and Voltages 1001 and above is called as High Voltage system in maritime practice for ships.
Why High Voltage in Ships
  • Higher power requirements onboard vessels is the foremost reason for the evolution of HV in ships.
  • Higher power requirements have been necessitated by development of larger vessels required for container transort particularly for reefer containers.
  • Gas carriers needing extensive cooling electrical propulsion.
  • For ships with a large electrical power demand it is necessary to utilize the benefits of a high voltage HV installation.
  • The design benefits relate to the simple ohms law relationship that current (for a given power)is reduced as the voltage is increased. 
  • Working at high voltage significantly reduces the relative overall size and weight of electrical power equipment.
As per Ohms law, POWER = VOLTAGE x CURRENT
For a given Power, Higher the Voltage, Lesser is the Current
440 KW = 440,000 watts              
               = 440 Volts x 1000 Amps              
                -1100 volts x 400 Amps              
               -11000 volts x40 Amps 
When large loads are connected to the LV system the magnitude of current flow becomes too large resulting in overheating due to high iron and copper losses.
P= V I cosĪ¦
Copper Loss = I2 R
Advantages:
  • For a given power, Higher voltage means Lower current, resulting in Reduction in size of generators, motors, cables etc.
  • Saving of Space and weightEase of Installation
  • Reduction in cost of Installation
  • Lower losses — more efficient utilisation of generated power.
Disadvantages:
  • Higher Insulation requirements for cables and equipment used in the system.
  • Higher risk factor and the necessity for strict adherence to stringent safety procedures.
  • Trained crew.

Sunday, August 2, 2020

Different types of Ballast water exchange

Sequential:
In this method the ballast tanks are emptied until the ballast pumps lose suction and then the tanks are further stripped by eductor systems. This is followed by taking fresh ballast into the tank.
Flow through method: 
In this method water in pumped into the tank and to allow it to overflow through the air vent or dedicated overflow vents. Three times the volume of the tank is to be pumped through to get a 95 percent efficiency of exchange.
Dilution Method: 
In this method the tank has two openings; water is pumped in from one opening and flows out through the other.

Saturday, August 1, 2020

TriboPack

The design measures incorporated in TriboPack are:
  • Multi-level cylinder lubrication
  • Liner of the appropriate material, with sufficient hard phase
  • Careful turning of the liner running surface and deep-honing of the liner over the full length of the running surface
  • Mid-stroke liner insulation, and where necessary, insulating tubes in the cooling bores in the upper part of the liner
  • Pre-profiled piston rings in all piston grooves
  • Chromium-ceramic coating on top piston ring
  • RC (Running-in Coating) piston rings in all lower piston grooves
  • Anti-Polishing Ring (APR) at the top of the cylinder liner
  • Increased thickness of chromium layer in the piston-ring grooves.

Friday, July 31, 2020

Port of Refuse

Port of refuse is a port or a place that vessels divert to when her master considers it unsafe to continue the voyage due to peril that threatens the common safety
  • Situation in which u call a port of refuge are
  • Dangerous shift of cargo
  • Serious breakdown of machinery
  • Serious fire on board
  • Shortage of bunkers
  • Rough weather
  • Collision
  • Grounding
  • Any other damage affecting seaworthiness of vessel
 HOW A SHIP CAN CALL A PORT OF REFUGE?
As soon as the decision is taken to discontinue the voyage and make for a place for refuge, inform the owner and the charterer (if any) stating the reasons for deviation. Give relevant details to attending superintendent. He will inform the necessary insurance manager and class.
  1. Record the ship’s position. Sound tanks for quantity for bunker on board. From the point until departure from the port of refuge, keep accurate records of events and expenditure.
  2. Request the owner to arrange the appointment of an agent at the port of refuge to handle the vessel’s visit.
  3. Call the agent as soon as his identity is known. Pass ETA and information necessary for making preparation for vessel’s arrival, including tonnage, length, flag, P&I club, classification society etc. 
Request the agent to notify :-
  • Port state administration if vessel is damaged or seaworthiness is affected.
  • Harbor master or port authority.
  • Pilot station, linesman, boatman, customs, port health etc.
  • Local correspondent of the owner’s P&I club.

Thursday, July 30, 2020

Engineroom Crane safeties

  • Limit switch for all 6 directions-fwd, aft, port, starboard, lowering and hoisting.
  • Mechanical stoppers in case limit switch fails.
  • Overload trip.
  • Electromagnetic brake. Release by availability of electric power.- Fail safe arrangement
  • Rail guard over the pulley
  • Mechanical locking arrangement for rough weather
  • Locking arrangement and hook for safe carriage of load.
  • Clear marking of Safe working load on crane.
  • Breakers at various places. One in engine room and another in ECR.
  • It shall be operate in 50 list and 20 trim.

Wednesday, July 29, 2020

What are the checks carried out after Over speed trip? .

  • Check over speed device.
  • Check governor
  • Check fuel pump rack
  • Open crankcase and check the condition inside 
  • Check bottom end bolts. It is better to change them once over speed trip has taken place. 
  • Over speed limits for AE-15% and for ME-20%

Tuesday, July 28, 2020

Scuffing

Piston ring scuffing is consists of local micro welding, or material adhesion, between a piston ring and a cylinder liner. Various causes of Scuffing are following

Lack of Lubrication
If the engine doesn't have enough oil, the cylinders will not be properly lubricated. As the ring rubs against the liner of the cylinder, dry spots will cause it to scuff. Symptoms of scuffed piston rings include dirty exhaust and excessive oil consumption.
Engine Dry Starts
If an engine has sat idle for even a short time, it may have a "dry start" when next used. This occurs because the existing lubricant sheen in the engine has dried up, and these dry parts of the engine run without lubricant in the first few seconds after the engine starts before lubricant is fully circulated. If an engine is dry-started after a new piston ring is installed, scuffing could result. To avoid this, lubricate the ring before installing it or add a secondary engine oiler that squirts oil into the engine before start-up.
Liner Surface Glaze
Engine cylinders that are overheated by insufficient lubrication can break down the little bit of oil that is present, which then accumulates as a glaze on the interior of the cylinder. This glaze can scuff the edges of a piston ring as it scrapes by, as the glaze won't allow oil to flow properly in the cylinder. Getting rid of this may require a professional reconditioning of the cylinder.
Liner Roundness Faults
If the liner of a cylinder is uneven, some points will rub against the piston ring and cause it to scuff. Here, too, a reconditioning of the cylinder may be necessary.

Monday, July 27, 2020

4-stroke connecting rod Specialty.

  • Big end and big end bearings are of split type
  • Big end is in an oblique direction to reduce the width of big end, reduce the load on bolts and increase the crankpin diameter
  • Top end is having bush type bearing
  • Rectangular or I-shaped is expensive to manufacture but necessary to resist high transverse inertia whip load, gas loads and to fulfill the weight to strength requirement
  • Connecting rod is forged from Magnesium Molybdenum.
  • Edges are serrated
  •  It is subjected to high compressive and low tensile bending stress as well as of axial type
  •  It connects crank pin direct to gudgeon pin

Sunday, July 26, 2020

Boiler Bulging

  • Formation of layer of scales on the furnace wall at the water side can cause overheating and bulging defect on the furnace shell.
  • Bulging in water tube is due to calcium scale deposition on tube walls which cause improper heat transfer.
  • In smoke tube due to carbon deposits bulging is caused.
  • Low water level in boiler.
  • Misalignment of burner can cause overheating which will further cause bulging.

Saturday, July 25, 2020

Hydrophore pump short cycling.

  • Pressure switch faulty- check pressure switch
  • Pressure switch wrongly set
  • Non return valve after pump leaking, hence water under pressure going back to storage tank- that would be indicated by monitoring of the concerned pump if reverse rotation is taking place.
  • Check on/off controller from pump main panel-contacts opening/closing
  • Check if system is overcharged
  • Check if system in undercharged- Since water is incompressible as soon as water is filled up pressure rises but just on little consumption pressure will drop drastically and pump restarts
  • Check for any air leaks
  • Faulty automatic air volume control
  • Not enough water in tank due to clogged pipelines
  • Air  leaking from relief valve
  • Tank is about to empty

Friday, July 24, 2020

Actions in case of Main Engine liner cracked

The engine cannot be run long in this condition. The leaking water is finding its way into the lubricating oil. The liner has to be changed.
The most logical step to take then is to isolate the faulty cylinder. It can be done.
  • Stop engine, isolate systems and allow to cool
  • Ensure a procedure is written that minimises the risk to personnel during the operation.
  • Discuss the task and written procedure with the engine room personnel to ensure they are familiar with the risks, and the methods to be used to minimise these risks.
  • Ensure the fuel pump is de-activated by lifting roller and locking.
  • Lift exhaust valve actuators so exhaust valve remains closed during running. (Note: the air spring supply to be left open)
  • Dismantle air start supply line, and blank with suitable steel plates, the main and control air pipes
  • Blank off main lube oil inlet to crosshead within the crankcase with a blanking plate.
  • Isolate the cylinder lubricator for that cylinder by placing all lubricators on no stroke.
  • Blank cooling water inlet and oulet.
The usual practice is to open up the cylinder head, remove the piston, and close back the cylinder head. All the passages that are connected to other parts of the engine will have to be blanked, so that the whole cylinder is completely isolated from the engine systems.
Since there is no piston in one of the cylinders of the engine, the crankshaft will be temporarily off-balanced. The engine has to be run at a much slower speed to avoid excessive vibration and unnecessary stress that can cause further damage.

Thursday, July 23, 2020

Propeller slip

  • When the vessel is moving ahead the propeller exerts pressure on the water to create the forward motion. 
  • Propeller slip occurs because water is not a solid medium and there is some slip related to it.
  • Slip may be considered as the difference between the speed of the vessel and the speed of the engine. 
  • It is always expressed as a percentage.
Propeller Slip = Actual forward speed/ Theoretical forward speed.
  • The calculated value of slip will be increased when the wind and sea are ahead and if the vessel has a fouled bottom. 
  • The differing values of slip are especially noticeable after a vessel has been cleaned in drydock.
  • Theoretically a vessel should never have negative slip, but this may occur in one or more of the following conditions:--  A strong following sea.
                                                                         A following current or a strong following wind

How to find the Propeller Slip
Mean Apparent slip = Distance run by propeller - distance run by ship per day
                                                             Distance run by propeller

Distance run by propeller in nautical miles = Pitch(m) x total engine revolution per day
                                                                                       1852

Wednesday, July 22, 2020

Engine room procedure to follow after grounding

The engineering staff may not be in a position to ascertain that the ship is aground and in normal circumstances will be informed by the bridge. However any grating noises along the ships hull in the machinery space should be considered a possible grounding or collision. In the event of grounding no attempt to re-float the ship will be made without first carrying out a thorough inspection to ascertain any damage.The following actions should be taken if the bridge informs the engine room that the ship is aground.

The initial response may be to Stop the Main Engine as quickly as possible and secure it, simultaneously with this start the Main Diesel Generator. Please note though with regard to the Main Engine it is our duty to obey Telegraph Orders as long as it possible and sensible to do so.
  • Stop and secure the steering gear, be aware that the Rudder may be aground/damaged.
  • Carry out a thorough inspection of the machinery space for structural damage and ingress of water. Due to the double bottom structure in the machinery space it may not be possible to see any structural damage clearly.
  • Sound all the machinery space tanks that have the ships hull forming part of there boundary. Careful when unscrewing any caps, as there might be water pressure present. This should include Fuel, Water, L.O. and double bottom tanks and dry spaces.
  • Inform the bridge of your findings and take further soundings at regular intervals.
  • Record all actions taken in the Engine Log book.
  • Check all sea inlets/outlets, their associated pumps and coolers are working correctly and not fouled.
  • Keep a close eye on the stern tube L.O. tank for loss of oil.
  • Engage turning gear and try to turn shaft. If any strain is shown by the turning gear it must be assumed that the propeller is also aground and the bridge informed of this. No further attempt to turn the shaft should be made until the propeller is clear. check crankshaft deflection to check bearing alignment.
  • A grounding could cause rapid fouling of Sea Suctions, Pumps and Coolers, with silt, resulting in a Blackout, as such the only power available would be that from the Diesel Generator and the Emergency Generator. Staff must be prepared to respond to situations and priorities which may change quickly.
When the ship is afloat and the engines are ready for use again a close eye should be kept on the shaft bearing and stern tube for
overheating or unusual vibrations in case the hull structure has been deformed, causing misalignment.

Monday, July 20, 2020

Functional requirements for a Safety Management System (SMS)

Every company should develop, implement and maintain a Safety Management System (SMS) which includes the following functional requirements:
  • A safety and environmental protection policy;
  • Instructions and procedures to ensure safe operation of ships and protection of the environment in compliance with relevant international and flag State legislation;
  • Defined levels of authority and lines of communication between, and amongst, shore and shipboard personnel;
  • Procedures for reporting accidents and non-conformities with the provisions of this Code;
  • Procedures to prepare for and respond to emergency situations; and
  • Procedures for internal audits and management reviews.


Thursday, July 2, 2020

Variable Exhaust Valve Closing (VEC)

  • In order to optimise the exhaust valve operation over the normal load range, the closing point of the exhaust valve is changed over 70-85% x MCR. During VEC operation the exhaust valve is closed EARLIER which means that the compression stroke of the piston is increased. This will lead to higher compression pressures and temperatures.
  • For instance if the normal closage of the exhaust valve is 130o BTDC, and this gives a compression ratio of 10.6, then by closing the valve 10o earlier, the compression ratio will increase to 11.2, and the compression pressure will rise by 4 bar, for the same scavenge air/load setting.
  • The unit achieves this by leaking some of the oil contained in the high pressure pipe when the valve is in the OPEN position. This will cause the valve to slightly close, but will mean that the exhaust valve will be fully closed EARLIER than normal. Hence the piston can start to pressurise the cylinder contents earlier. The amount the valve closes is dependant on the position of the VEC shaft and eccentric mounted on the side of the exhaust valve actuator.

Certificate of registry. What all it contains.

  • Name of a ship
  • Port of registry
  • IMO number
  • Call sign
  • Type of vessel
  • Owner name and address
  • Registration number
  • Ship particular like gross and net tonnage, length, breadth, builder name, hull material, type of engine and its builder, power
  • Date of issue
  • Any mortage on ship in record page.

Ballast Water Managment plan

  • Ship particulars
  • Explain of ballast water management plan like purpose, usage, crew training, port state requirements
  • Ballast water tank, its line, pump capacity
  • Safety consideration like hazards in sequential method, condition under which Ballast water exchange shouldn't  be carried out.
  • Duties of ballast water management officer.
  • Control and disposal of sediment
  • Ballast water reporting form.
  • Crew training
  • Ballast water exchange procedure
  • Ballast water record book, BWTS

Steam trap

  • Steam is formed when water vaporizes to form a gas. 
  • This is done by giving latent heat of vaporization to water. 
  • By this water will convert into vapor. 
  • When the work is done (i.e. steam has given up its latent heat), steam condenses and becomes condensate. 
  • Now the condensate will not be able to work same as the steam. 
  • So now the thermal efficiency will reduce as efficient steam is mixed with the condensate.

Boiler Survey

  • Boilers are inspected to maintain the regulatory requirement.
  • Regular internal and external examination during such survey constitutes the preventive maintenance schedule the boiler goes through to have a safe working condition.
Interval:
  • Boilers require to be surveyed at 2-year intervals until they are 8 years old, thereafter they become due for survey annually.
Procedures:
Planning:
  • Discuss with Master and Chief Engineer to confirm time available, manpower and time required and steam requirement for next port.
  • Checks before shutting down boiler:
  • Sufficient spares (joints, packing, gauge glass, etc)
  • Past reports and manual for special attention need to be take care
  • Special Tools required
  • Meeting and brief with all engineers involved
  • Mark all valves, safety valve setting and spigot clearance
 Before shutting down boiler
  • Inform Chief engineer
  • Inform duty deck officer
  • Top up DO service tank
  • Change over M/E, A/E and boiler to Diesel oil
  • Stop all purifier
  • Shut all heating and tracing steam valve
  • Soot blow the boiler
 Shutting down Boiler
  • Change over to manual firing
  • Stop firing
  • Purge boiler for 5 minutes
  • Shut main steam stop valve
  • Switch off power, off the circuit breaker and remove fuses for FD fan, FO pumps, feed pumps and control panel.
  • Put a notice on the circuit breaker mentioned above
  • Shut all fuel valve and atomizing valve and lock them in shut position, blank the line if necessary
  • Allow boiler to cool down slowly
  • Scum blowdown follow by bottom blowdown when the boiler cooled
  • Open air vent when boiler pressure drop until 2 bar to prevent vacuum formation
  • Further cooling of boiler
  • Prepare to open top manhole door when boiler is cooled and at atmospheric pressure
  • Slacken the dog nut and secure manhole with rope
  • Knock manhole door gently with long stick. Do not open fully because hot steam or water might gush out.
  • Open full when is safe
  • Allow further cooling of boiler before open the bottom manhole door. This is to prevent thermal shock
  • Confirm no large quantities of hot water lying in the bottom
  • Open the bottom manhole door with the same precaution as with the top manhole door
  • Open the furnace door slowly
  • Ventilate the boiler both water and fire side for 12-24 hours
  • Enclose space entry permit obtained
  • Check Oxygen, flammable gas and toxic gas content
  • Prepare to entry
Preparation for entry
  • Prepare safety torch and safety hand lamp
  • Investigate from outside make sure it is clear from obstruction before entering boiler
  • Oxygen analyzer is carry with the person entered boiler
  • Personnel entering must wear all safety gears
  • Clear pocket contents and tools to be carried in a bag and accounted
  • A responsible engineer to be standby outside with clear emergency order
  • Keep breathing apparatus ready
  • Remain communication
  • Ensure proper lighting at all time
 Boiler Inspection
  • Thoroughly cleaned before boiler is surveyed
  • Wire brush and hose down may be sufficient to prepare for survey in well maintained boiler
  • Chipping off scale is necessary
  • If traces of oil are found in boiler, chemical means may have to be adopted to remove them
  • Route of inspection
Gas Side
  • Exterior of drums for signs of tube roll, leakage, corrosion, soot erosion and overheating
  • Condition of outside drum insulation
  • Drum seals for sign of air leakage
  • Inspect drum support for crack and expansion clearance
  • All blowdown connections for expansion and flexibility of support
  • All piping and valve for leaks
  • Water wall tubes and fins for crack
  • Exterior of all tubes for corrosion, carbon build up, erosion, blisters and sagging
  • Tubes near soot blowers for steam impingement
  • Condition of refractory
  • Around burner assembly, refractory and accumulation of soot or carbon
  • Soot blower for distortion, worn bearings, rubbing of tubes, condition of nozzles, cracks, freedom of movement and effective lubrication
 Water side
  • Steam drum for corrosion scaling and pitting
  • Manhole seats and surface
  • Condition of all fee, chemical feed, blowdown lines and inside pressure parts for choking, security and leaks
  • Tubes for corrosion, excessive deposits, flare cracking and pitting
  • Hand hole plates and stud threads
Safety Valve
  • Condition of valve internal parts for signs of corrosion, galling and wear
  • Check for pitting, crack, resiliency and condition of springs
  • Check spindle for straightness and adjusting ring thread for freedom of movement
  • Check discharge and drain piping
  • Check dampers to ensure that linkage are secured and well greased
  • Condition of burners, swirler and air register
  • Wind-box dampers and vanes for sign of corrosion and erosion
  • Check condition and operation of all valve
  • Check feed water controller and control valve connection lines and ensure proper functioning
  • Examine the foundation and bracing bolts of boiler for corrosion, fretting and rustin
Closing
  • Inspect internal surface to ensure they are clean
  • Counter check all tools are out from boiler
  • All opening of the mounting are cleaned properly
  • Mountings to be fixed back with new set of gasket/joint
  • Replace the header handhole and the bottom manhole door
  • Operate all mounting valves to ensure they work freely and leave all valves in close position
  • Replace top manhole door
  • Sootblower are correctly fitted
  • Air control dampers move freely for their full travel
Preparation flashing up:
  • Open gauge glass steam and water cocks and shut drain cock
  • Open vent, alarm and pressure gauge connection valve
  • Shut all drain valve
  • Switch on power for control panel, feed pump, FD fan and FO pump
  • Fill boiler with hot distilled treated water
  • Fill until water level below normal level
  • Check control air is available
Flashing Up
  • Start FD fan and purge boiler for 5 minutes
  • Start FO pump and check all parameters
  • Fire boiler with minimum firing ratio
  • Continue firing intermittently e.g. 1min. fire, stop 10min. for 1st hour, 2min fire, stop 10min. for 2nd hour and so on….
  • As boiler heats up, water level will rise to normal level, top up if necessary
  • Continue fire until a continuous stream of steam comes out from air vent
  • Shut air vent
  • Blow through gauge glass when boiler pressure raised
  • Open valve to remote level indicator
  • At 7 bar, all securing buts to be retighten
  • Open steam line drains to drain off condensate
Starting the boiler for a normal operation:
  • Warm up the steam line
  • Gag 1 safety valve, raise the steam pressure slowly and check safety valve operation and if need adjust it.
  • Repeat the procedure for other safety valve
  • Ensure no condensate at the drain line
  • Crack open main steam stop valve, slowly open until its full open
  • Keep firing as steady as possible
  • Check all safety cut outs and alarms before putting boiler on Auto
  • Final round check on boiler
  • Start tanks and tracing steam heating
  • Open steam to all heaters
  • Start all purifier
  • Change over from DO to HO for boiler and Generator
  •  M/E change over during departure
 EGE Safety valve
  • C/E to set the safety valve when the ship is at sea
  • Report to surveyor in writing to confirm safety valve operation

Wednesday, July 1, 2020

Shell Expansion Plan

  • It is a two dimensional drawing of a three dimensional surface of the ship’s hull form.
  • This plan is very useful for the following information:It is used for marking the location of a hull Damage on this plan by identifying the strake number , letter and frame number so that the exact location of the damage and also suggested repairs are marked in a localised copy.
  • The shell expansion can be used for finding areas of painting surfaces such as topside, boot topping and bottom areas by applying Simpsons rules directly. 
  • In the shell expansion the vertical scale used is different from the horizontal scale and a suitable adjustment has to be made when calculating areas.
  • This becomes useful in solving disputes concerning areas of preparation and painting.
  • It gives information on the thickness of the original strake which is indicated by the number in the circle shown in the strake. 
  • The quality of steel used is also shown by letters A,B,D E and AH, BH,DH, EH.


Drydock Stability

  • When the ship enters a dry dock, it must have a positive metacentric height; and is usually trimmed by stern. The floor of the dry dock is lined with keel blocks, which are so arranged such that they can bear the weight of the ship. When the ship enters the dry dock, her centerline is first brought in line with the centerline of the keel blocks by using a combination of plum lines and Leica theodolite.
  • The dock gates are then closed and the water is pumped out of the dock in stages. Since the ship has a trim by stern, the stern of the ship will first sit on the keel blocks. The rate of pumping out water is reduced as the stern is almost about to touch the keel blocks. The reason is, it is from this stage of the docking procedure when the stability of the ship starts getting critical. The interval of time from when the stern takes the blocks to the moment when the entire ship’s weight is borne by the blocks is called Critical Period. We will understand the details a little later.
  • When the stern of the ship takes the blocks, it is fixed to the shores (sides of the dock). This is carried out from aft to forward so that by the time the entire ship takes the blocks, it is fixed to the shores. When the ship is completely borne by the blocks, water is pumped out quickly from the dock.
  • When the ship’s stern just touches the keel blocks, part of the ship’s weight is being borne by the keel blocks. The contact between the stern and the keel block creates a normal reaction or upthrust. The magnitude of this upward normal reaction increases as the water level in the dry dock reduces. It is this upthrust that creates a virtual reduction in the metacentric height of the ship. Hence it is very crucial to maintain sufficient positive metacentric height before docking, lacking which, the ship may heel over to either side, or even slip off the keel blocks and capsize.
Three vertical parallel forces acting on the ship:
  • Weight (W) acting downward.
  • Keel block upthrust (P) acting upward.
  • Buoyancy (W-P) acting upward.
The upthrust force (P) can be considered to have an effect similar to that of removal of a weight from the ship. This has the virtual effect of rising the center of gravity of the ship from the point ‘G’ to ‘G1’. The metacentric height therefore reduces from GM to G1
H            Virtual rise in CG during dry docking.
The virtual reduction in metacentric height at any stage of the docking process can be calculated by the following expression:

  • This calculation must be carried out for the condition when the ship has just touched the keel blocks throughout its length. 
  • It is at this point that the keel block upthrust is maximum, and the risk of tipping over or slipping from keel blocks is most likely if the metacentric height is too low or negative

ODME

A step by step guide of how to operate ODME and principle of its operation

How does ODME do it
ODME controls the operation of two valves
  1. Valve to slop tank.
  2. Valve to overboard tank.
These two valve will never be open or close together. If one is open, the other will be in close position.

The formula for Instantaneous rate of discharge is
Now if ODME need to measure IRD, it surely need values for oil content in PPM and Flow rate.
  • Speed connection is usually given either from log or GPS.
  • All these values are fed to the computing unit of the ODME. 
  • Computing unit does all the mathematical calculations to get the required values. 
  • Most of the times you will find the computing unit in Cargo control room.
Flow rate
  • ODME computing unit gets the flow rate from flow meter. 
  • A small sample line goes from the main line, pass through the flow meter and goes back to the main line. 
  • Flow meter calculates the flow in m3/Hr and gives this value to the computing unit through a signal cable.
Measuring PPM
  • Measuring cell is the component that measures the amount of oil (in ppm) in the water. Measuring cell is located in a cabinet called “Analysing unit”. Most of the times you will find “Analysing unit” in the pump room.
  • The measuring principle relies upon the fact that different liquids have different light scattering characterstics. Based on the light scattering pattern of oil, measuring cell determines the oil content.
  • The sample water is passed through a quartz glass tube. And the oil content is determined by passing this sample water in different detectors in series.
  • But to measure PPM in a water sample, a sample from the discharge water need to pass through the measuring cell. This job is done by a sample pump.
  • Sample pump draws the sample from the discharge line before the discharge valves. This sample is sent to the measuring cell (in analysing unit) for measuring the oil content and then sent back into the same discharge line.
  • To clean the measuring cell, ODME runs cleaning cycle in pre-defined interval during its operation. The cleaning cycle involves flushing the cell with fresh water.

If the ODME has provision for detergent injection, the required amount of detergent will be injected during the cleaning cycle
We need to make sure that the detergent tanks is not empty and we use maker recommended detergent only.
Operation of ODME
  • Allow minimum 36 hours settling time
  • We will wash the tanks and collect the slops in slop tank. But before we can start pumping out oily water through ODME, we need to allow a minimum of 36 hours settling time. This settling time ensures that the oil has separated completely from the water.
  • We may argue that if our discharge is limited to 30L/NM, then what difference does it make with settling time ? But the fact is that even when we can use the ODME to discharge oily water, we must ensure that the oil is minimum in the water

Which certificate is valid for Life time of ship

  • Tonnage certificate 
  • Safe Manning certificate 
  • Enhanced survey report 
  • International Energy efficiency certificate
  • CSR
  • SEEMP
  • Certificate of registry
  • All are permanent until and unless any major conversions are done

Measures for improving ship efficiency

  • Maintaining the Engine and equipment in order as Per PMS.
  • Fuel injector, T/C, EGB routine maintenance, proper  Injection timing , VIT adjustment.
  • Regular Propeller and Hull cleaning .
  • ICCP proper use of right amp and current to avoid the fouling.
  • Avoid unnecessary running of DG unless safety requirement.
  • Achieve optimum trim (not by head down)
  • Efficient operation of deck cranes
  • Closing boiler steam for undesirable bunker tanks

Power to weight ratio

  • Power to Weight ratio is the ratio of horsepower produced to the weight of the engine itself.
  • With high-speed or high-performance vessels, it is the most important criterion to use when comparing engines between two different makers since weight on these vessels is often critical, with vessel speed being the most important aspect of many military missions.
  • Higher weight always equals higher displacement equals lower speed On commercial vessels, displacement is critical due to cost.
  • Higher displacement requires more fuel to move the vessel.
  • More fuel means higher cost of operation.

Carbon foot print

  • The total amount of greenhouse gases produced to directly and indirectly support human activities, usually expressed in equivalent tons of carbon dioxide (CO2).
  • Carbon dioxide is a so called greenhouse gas causing global warming .
  • Other greenhouse gases which might be emitted as a result of your activities are e.g. methane and ozone.
  • These greenhouse gases are normally also taken into account for the carbon footprint.
  • They are converted into the amount of CO2 that would cause the same effects on global warming (this is called equivalent CO2 amount).
  • Your carbon footprint is the sum of all emissions of CO2 (carbon dioxide), which were induced by your activities in a given time frame.
  • Usually a carbon footprint is calculated for the time period of a year.

Water Ingress Alarm

  • The water ingress alarm is in place seeing as the ingress of water may taint or corrupt the cargo/commodity being carried on a bulk carrier.
  • For example, SOLAS states that “In each cargo hold, giving audible and visual alarms, one when the water level above the inner bottom in any hold reaches a height of 0.5m and another at a height not less than 15% of the depth of the cargo hold but not more than 2.0 m”.
  • Also, check and maintain water ingress alarm in the area located at the forward of the cargo area.

Actions in case of Main Engine liner cracked

The engine cannot be run long in this condition. The leaking water is finding its way into the lubricating oil. The liner has to be changed.
The most logical step to take then is to isolate the faulty cylinder. It can be done.
  • Stop engine, isolate systems and allow to cool
  • Ensure a procedure is written that minimises the risk to personnel during the operation.
  • Discuss the task and written procedure with the engine room personnel to ensure they are familiar with the risks, and the methods to be used to minimise these risks.
  • Ensure the fuel pump is de-activated by lifting roller and locking.
  • Lift exhaust valve actuators so exhaust valve remains closed during running. (Note: the air spring supply to be left open)
  • Dismantle air start supply line, and blank with suitable steel plates, the main and control air pipes
  • Blank off main lube oil inlet to crosshead within the crankcase with a blanking plate.
  • Isolate the cylinder lubricator for that cylinder by placing all lubricators on no stroke.
  • Blank cooling water inlet and oulet.
The usual practice is to open up the cylinder head, remove the piston, and close back the cylinder head. All the passages that are connected to other parts of the engine will have to be blanked, so that the whole cylinder is completely isolated from the engine systems.
Since there is no piston in one of the cylinders of the engine, the crankshaft will be temporarily off-balanced. The engine has to be run at a much slower speed to avoid excessive vibration and unnecessary stress that can cause further damage.

Difficulties during manoeurvring with M/E one unit isolated

  • Ln one engine cylinder is isolated, then one problem that may occur is a “dead spot” during manoeuvring. 
  • This is due to the air start valve being isolated for that unit, and is more likely when a smaller number of cylinders are present. 
  • The Master must be informed that this could occur, and the remedy would be to kick the engine in the opposite direction, and then restart in the required direction

Overheating of Main Engine Piston

Reasons: 
  • Inadequate circulation of cooling media and or supply not sufficient
  • Excessive deposit in cooling space (scale or carbon)
  • Lubrication not sufficient
  • Faulty piston ring : clearance inadequate. 
  • Too high temperature 
  • top ring groove area – blow by.
  • Distorted cylinder liner
  • Misalignment of piston
  • Overloading of unit – excessive fuel
  • Excessive water content in fuel
  • Insufficient air from turbocharger or manifold
  • Late injection of fuel – timing or fault injectors
  • Engine running slow speed – full flow of coolant not maintained
Action:
  • Slow down the engine to a very low speed but NOT complete shutdown. This results in considerable reduction of heat in the relevant piston.
  • Since not all pistons would likely develop this fault simultaneously (unless you are totally out of luck that day) so first identify the particular cylinder in which the problem has occurred using parameters such as temperatures, sound etc.
  • The fuel supply to the affected cylinder should be cut-down from the fuel pump
  • Lubrication to that cylinder should be increased from the appropriate arrangement depending on the specific engine under consideration
  • Only stop the engine when it is sufficiently cooled to avoid any thermal stresses. Even after stopping the turning gear should be used to keep it moving for some time while cooling and lubrication is continued.
  • Finally the piston needs to be dismantled and checked and this is a detailed procedure which we might take up in future

Double evaporation boilers

  • A double evaporation boiler uses two independent systems for steam generation and therefore avoids any contamination between the primary and secondary feedwater.
  • The primary circuit is in effect a conventional watertube boiler which provides steam to the heating coils of a steam-to-steam generator, which is the secondary system.
  • The main reason for the adoption of this design of boilers is to allow use of modern high efficiency watertube boilers witghout fear of damage through contamination by cargo or fuel oils.The basic design consists of a D-Type boiler design upon which is mounted a Steam/Steam generator drum.
  • The steam generated by the main boiler heats water in the Steam/Steam generator which produces steam requirements.
  • The primary drum is initially filled with high quality feed water and suitably dosed.
  • The  main  reasonfor  the  adoption  of  double  evaporation  boilers  in  tankers are  concerned  of  damage  caused  by  oil  and  sulphur  which  enters  the  feed  systems  through  leaky  steam  heating  coils  used  for  heating  the  oil  in  cargo  tanks.

Regulations and Requirements for IG Blowers

  • 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.

Condition Monitoring

  • Condition monitoring (or, colloquially, CM) is the process of monitoring a parameter of condition in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of a developing fault. It is a major component of predictive maintenance. 
  • The use of condition monitoring allows maintenance to be scheduled, or other actions to be taken to prevent failure and avoid its consequences. 
  • Condition monitoring has a unique benefit in that conditions that would shorten normal lifespan can be addressed before they develop into a major failure. 
  • Condition monitoring techniques are normally used on rotating equipment and other machinery (pumps, electric motors, internal combustion engines, presses),
Condition monitoring techniques
  • Vibration and shock pulse data measured from all machinery. On the spot analysis and interpretation of results.
  • Thermo graphic inspection of all electrical and some critical mechanical systems.
  • Pressure and vacuum leak detection using passive ultrasonic frequency methods.
  • Thickness measurement of critical machinery systems.
  • Main and auxiliary engines performance test and power balance analysis.Detailed machinery health assessment report.
Benefits:
  • Help maximize the availability of your critical and auxiliary machinery
  • Simplify maintenance and reduce maintenance costs
  • Give an early indication of possible problems
  • When a machine is operating properly, the vibration is small and constant, however, when faults develop and some of the dynamic process in the machine changes, there will be changes in vibration spectrum observed.
When a fault takes places, some of the machine parameters are subjected to change. The change in the machine parameters depends upon the degree of faults and the interaction with other parameters.
In most cases, more than one parameter are subjected to change under abnormal condition.
Condition monitoring can be carried out when the equipment is in operation, which known as on-line, or when it is off-line, which means when it is down and not in the operation.
While on-line, the critical parameters that are possible to monitor are speed, temperature, vibration, and sound. These may be continuously monitored or may be done periodically. Off-line monitoring is carried out when the machine is down for whatever reason.
The monitoring in such would include crack detection, a thoroughly check of alignment, state of balancing, the search for tell-tale sign of corrosion, pitting, and so on.
Vibration signals are the most versatile parameters in machine condition monitoring techniques.
Periodic vibration checks reveal whether troubles are present or impending. Vibration signature analysis reveals which part of the machine is defective and why.
 Although a number of vibration analysis techniques have been developed for this purpose, still a lot of scope is there to reach a stage of expertise.

Wear rate of liner

  • For Two Stroke engine a wear rate of 0.1 mm per 1000 hour is normal.
  • Maximum acceptable rate is 0.25 mm per 1000 hr.
  • Maximum total wear is acceptable is 0.75% of bore.
  • Useful life span: 70,000 - 80,000 hours
  • For Four Stroke engine the wear rate is 0.02 mm per 1000 hours

Heating Rods for Refrigeration Compressor Oil Heating

  • The refrigeration compressors are delivered in a standard execution with built-in heating coils or rod in the crankcase.
  • The purpose of the heating coil or rod is to keep the oil in the crankcase warm even during standstill of the compressor. This ensures a low content of refrigerant in the oil.
  • Too much refrigerant in the oil makes it loose its lubricating properties. This may lead to damage of the movable parts in the compressor.
  • Further, the danger exists that the oil, during start-up of the compressor, foams so vigorously that the lubricating pressure will disappear.
  • Before start-up the heating rod should be switched on for at least 8 hours.
  • The heating coil or rod must not be switched on if the oil level in the vessel is below minimum in the sight glass. While the compressor is operating, it is usually switched off.
  • Further, remember to switch off the heating rod if the compressor crankcase is opened for inspection.

Destructive and Non-Destructive test

Destructive test
  • Test on test pieces Damaged after test.
  • Determine mechanical properties of test piece under test.
  1. Tensile test 
  2. Impact Test   
  3. Fatigue Test
  4. Bend test 
  5. Hardness Test 
  6. Creep Test
Non-Destructive Test
  • Test on components. Not damaged after test
  • Determine flaws or imperfection during manufacture (or) service.
  1. Liquid penetrating  
  2. Electrical test method
  3. Ultrasonic method  
  4. Radiographic inspection
  5. Magnetic crack detection

Destructive test
Tensile Test

  • Tensile test is used to determine the behaviour of a material up to its breaking point.
  • A special shape specimen of standard size is gripped in the jaws of a testing machine. A load is gradually applied to draw the ends of the specimen apart such that it is subject to tensile stress up to yield point.
  • The highest value of stress is known as the ultimate tensile stress (UTS) of the material.
Bend Test
  • Specimen is bent through an angle of 180 with internal radius of 1.5 times the thickness of the specimen without cracking at edges.
Impact Test
  • Testing machine basically consists of a pendulum which is raised and allowed to fall, striking and rupturing the specimen.
  • In swinging through its arc of travel past specimen, pendulum assume a lower position at end of its travel due to loss of   energy when it strikes the specimen.
  • Energy given up to the specimen is its impact strength.
Hardness Test
  • Hardness test consist hardened steel ball impressing into metal at given pressure for predetermine time.
  • Load is 3000 kg for steel and 500 kg for soft metals such as brasses and bronzes.
  • Diameter impression indicates the hardness number.
Fatigue Test
  • 'Fatigue' is defined as the failure of a material due to repeatedly applied stress.
  • The specimen is rotated under load in a testing machine. So it is subject to tension and compression stresses alternately.
  • The number of cycles imposed before is recorded.
Creep Test
  • Creep test use to find safe working stress for material working at high temperature
  • It is permanent deformation resulting from loading over long period of time
  • Test piece mount vertically and constant tensile load under constant temperature.
  • Temperature range between 600’C to 1000’C and test period is 1000,10000,100000 hours

Non-Destructive Test
Liquid penetrate test
  • Industrial method, indicate presence crack, lamination lap and surface porosity.
  • Fluorescent dye method and Aerosol dye method.
Fluorescent dye method
  • First, the surface is cleaned using a volatile cleaner and degreaser.
  • Then a fluorescent dye is applied and a certain time allowed for it to enter any flaws under capillary action.
  • Then the surface is wiped clean using the cleaning spray.
  • An ultra violet light is shone on the surface, any flaws showing up as the dye fluorescent.
Aerosol dye method
  • The more commonly used dye penetrant method is similar in application.
  • The surface is cleaned and the low viscosity penetrant is sprayed on.
  • After a set time, the surface is cleaned again.
  • Then a developer is used which coats the surface in a fine white chalky dust.
  • The dye seeps out and stains the developer typically a red colour.
Ultrasonic Test
  • Probe of test equipment transmits high frequency sound waves about 0.5 MHz to 20 MHz which reflected by any flaws in object
  • Reflected sound waves displayed on monitor screen of cathode ray oscilloscope.
  • Suitable for detection, identification and size assessment of a wide variety of both surface and sub-surface defects in materials.
  • Measured thickness of material or to detect internal or surface defects in welds, casting or forging either during manufacture or when in service.
Radiographic Test
  • Image produced on film.
  • X rays and gamma rays are used for inspection of welds, castings, forging and pressure vessels etc.
  • Exposure time for x-rays and gamma rays vary with type of material, thickness and the intensity of rays.
  • Faults in the metal effect the intensity of rays which passes through the material
  • Film exposed by the rays gives the shadow photograph
  • Used on both metallic and nonmetallic material, both ferrous and non-ferrous metal

Consequences of running an engine with slack Tie bolts:

  • Cylinder beam would flex and lift at the location of the slack bolt landing faces of the tie bolt upper and lower nuts, landing faces of the cylinder beam on the frame would fret and machined faces would eventually get destroyed.
  • The fitted bracing bolts between the cylinder jackets will also slacken and the fit of the bolts would be lost.
  • If fretting has occurred in an uneven pattern where the cylinder beam lands, and the tie bolts are tightened, the alignment of cylinder to the piston stroke will be destroyed. The fitted bracing bolts between the cylinder jackets will also slacken and fit of the bolts will be lost.
  • Fretting may make the nut landing face out of square and if tie bolts are tightened on the damaged face, a bending moment will be induced in the tie bolt, this may cause an uneven stress pattern in the tie bolt which could lead to early fatigue failure. Damage may take place in the bedplate in way of cross girder.                                                          
  • Rigidity of the whole structure will be destroyed. Guide force will have to be absorbed by the frame bolts and dowels, which may stretch and slacken allowing the structure to ‘work’.  This may destroy the piston alignment.   Guide faces and bars may get slackened (these are bolted to the supporting structure)

Difference between Slow speed , Medium speed and High speed engines


Operating Cycles

OTTO CYCLE (Constant Volume Combustion Cycle).
  • It is the ideal air standard cycle for Petrol engine, the gas engine and the high-speed oil engine.
  • The engines based on this cycle have high thermal efficiency but noisiness results particularly at higher power due to higher pressures in the cylinders.

DIESEL CYCLE (Constant Pressure Combustion Cycle).
  • It is the ideal Air standard cycle for Diesel Engine, especially suitable for low speed Diesel Engine but not for high speed Diesel Engine.
  • The thermal efficiency is lower than Otto cycle engines but engines run smoothly due to lower pressures in the cylinder.

DUAL COMBUSTION CYCLE (Constant Pressure and Constant Volume Combustion Cycle).
  • Modern Diesel Engines do not operate purely on constant pressure combustion cycle but some part of combustion process takes place at constant volume while the rest is completed at constant pressure.
  • In general, this cycle resembles Constant volume combustion Cycle more than constant pressure combustion cycle. It is suitable for modern Medium and High Speed Diesel Engines.
  • The thermal efficiency is more than Diesel Cycle but less than Otto cycle. Also noise level is in between the two. This is a more practical engine.

p Alkalinity and m Alkalinity

What is p Alkalinity?
  • The  term  p  Alkalinity  stands  for  “Phenolphthalein  –  Alkalinity”. 
  •  It  is  the  measurement  of Hydroxide and carbonate ion amount. 
  • It is determined by titrating a water sample with an acid of a known concentration in the presence of phenolphthalein as the indicator.
 What is m Alkalinity?
  • The  total  measurement  of  Hydroxide  bicarbonate  and  carbonate  ions amount is given by m Alkalinity. The letter m refers to Methyl orange.
  • It is the indicator that is used to determine the total alkalinity given by the above hydroxide and carbonate species.
  • When methyl orange is added, it gives its color change only  in its pH range which is, 3.1  –  4.4. Since only  trace  concentrations  of  other  acids  are  dissolved  in  water  except  for  carbonic  acid,  m Alkalinity can be considered as the total alkalinity because it gives the total carbonate alkalinity.
What is the difference between p Alkalinity and m Alkalinity?

p Alkalinity vs m Alkalinity
  • p alkalinity is the measurement of alkalinity given by hydroxide ions and half of the carbonate alkalinity.
  • m alkalinity is the measurement of alkalinity given by hydroxide ions and total carbonate alkalinity.
Indicator
  • Phenolphthalein indicator is used to determine p alkalinity.
  • Methyl orange is used to determine m alkalinity.
pH Range
  • p alkalinity is measured at a range of 8.3 –10.0 pH.
  • m alkalinity is measured at a pH range of 3.1 – 4.4.

Sunday, June 28, 2020

Timing diagram and Power card of 4 stroke cycle

  • The timing diagram shows the closing and opening of the valves. The working cycle is illustrated as a ‘P - V’ diagram (pressure-volume). The line ‘l – l’ represents atmospheric line. The piston is considered to have just moved over the ‘top dead centre’ and is on its way down. The air inlet is already open and because of the partial vacuum created when the piston moves towards its bottom position, fresh air is sucked into the cylinder. This process is represented in the 'p-v' diagram by the line ‘1-2’ which is termed suction line. This movement of the piston is called 'Suction Stroke".
  • After the piston has moved over bottom dead centre, the suction valve closes and the volume of air in the cylinder is compressed during the course of the up stroke of the piston. This is represented by the line ‘2-3’ in the above diagram and termed as compression line. This movement of piston is compression stroke.
  • The ignition takes place at point 3 and combustion continues for the duration of fuel injection, ending at point 4. After this combustion products expand to point 5 when the exhaust valve opens. Power is produced between point ‘4 – 5’.
  • The pressure drops in the cylinder to the exhaust line from 5 to 6. The exhaust valve remains open till after piston passes over the top dead center. The combustible gases are expelled. The line 6 to 1 represents this. The pressure is slightly above atmosphere, because of the resistance in the exhaust pipe. This stroke is 'exhaust stroke'.
  • A 4-stroke engine requires two complete revolutions of the crankshaft to finish working cycle.
  • This means inlet, exhaust & fuel valve must only function once for every two revolutions of the crankshaft.
  • In order to activate those valves in the correct sequence, it is necessary to operate them from a shaft, which rotates at half the speed of the crankshaft. This is called camshaft.

Slide Valves : Simple things that mean a lot


Exhaust valve Materials and Treatments

Material Requirements.
  • The material should retain its greatest strength at high temperatures.
  • No tendencies to air harden.
  • Critical temperature above 800*C.
  • No tendency of high temperature scaling.
  • Hot and cold corrosion resistant.
  • Able to be forged and machined easily.
  • Capable of consistent and reliable heat treatment.
  • Most diesel engines use an Austenitic heat-resisting alloy steel. The seating surface can be stellited.
Typical heat treatment: 
  • Heat up to 950*C and cool in air to give a Brinnel Hardness of 269.
Surface Treatment:
  • Surface treatment is frequently used to improve or modify valve steel characteristics. Chrome-cobalt-tungsten alloy available in various grades of hardness is widely used.
  • The hardness when deposited is in the order of 375 to 425 Brinnel.
  • The valve head is treated to more than 430*C to reduce contraction stresses.
  • The value face is now sweated by an oxyacetylene flame and the alloy deposited continually by welding (1.02 mm to 1.52 mm).
Valve Seat Inserts:
  • Alloy Irons, with high percentage of molybdenum and Chromium with a Brinnel number of Approx. 500 are best.
  • Alloy steel with stellited seating surface are also in common use.
  • The methods employed for fitting the inserts include screwing and shrinking.
Valve Guides:
  • Valve guides are mostly made of Cast Iron.
  • To avoid scaling etc at high temperatures alloy Irons are preferred.
  • Phosphor Bronze and Gun metal have also been successfully used.
  • Alloy Iron guides with Bronze linings also are in common use.
Valve Housing:
  • Mostly made of pearlitic cast iron and provided with a chamber for cooling water.

Saturday, June 27, 2020

Construction and Working Principle of Indicator

  • An engine indicator consists of a small bore cylinder containing a short stroke piston which is subjected to the same varying pressure that takes place inside the engine cylinder during one cycle of operations.
  •  This is done by connecting the indicator cylinder to the top of the engine cylinder in the case of single-acting engines, or through change over cocks and pipes leading to the top and bottom ends of the engine cylinder in the case of double-acting engines.
  • The gas pressure pushes the indicator piston up against the resistance of a spring, a choice of specially scaled springs of different stiffness being available to suit the operating pressures within the cylinder and a reasonable height of diagram.
  • A spindle connects the indicator piston to a system of small levers designed to produce a vertical straight-line motion at the pencil on the end of the pencil lever, parallel (but magnified about six times) to the motion of the indicator piston.
  • The “pencil” is often a brass point, or stylus, this is brought to press lightly on specially prepared indicator paper which is scrapped around a cylindrical drum and clipped to it.
  • The drum, which has a built-in recoil spring, is actuated in a semi-rotary manner by a cord wrapped around a groove in the bottom of it; a hook at its lower end to a reduction lever system from the engine crosshead attaches the cord, passing over a guide pulley.
  • Instead of the lever system from the crosshead, many engines are fitted with a special cam and tappet gear to reproduce the stroke of the engine piston to a small scale.
  • The drum therefore turns part of a revolution when the engine piston moves down, and turns back again when the engine piston moves up, thus the pencil or stylus on the end of the indicator lever draws a diagram which is a record of the pressure in the engine cylinder during one complete cycle.

Procedure for opening Main Engine Liner

Following Procedure has to be followed when opening Liner
  • Inform company and take permission.Take immobilisation certificate from port state control.
  • Read the manual and have a tool box meeting with everyone involved in the job.
  • Discuss the complete procedure.
  • Prepare important tools and spares required for overhauling liner as given in the manual
  • Prepare risk assessment and make sure all personal safety equipment are used
  • Shut starting air for Main Engine and display placards
  • Engage turning gear
  • Open indicator cocks for all the cylinders
  • Stop main lube oil pump and switch off the breaker
  • Once the engine jacket temperature comes down, shut the inlet water valve for the unit to be overhauled
  • Keep other units in Jacket preheating system to maintain the jacket temperature
  • Drain the jacket water of the concerned unit from exhaust v/v and liner.
  • Shut the fuel oil to the particular unit whose liner is to be removed
  • Dismount the cylinder head using dedicated lifting tools
  • Discard the sealing ring from the top of the cylinder liner.
  • Turn the piston down far enough to make it possible to grind away the wear ridges at the top of the liner with a hand grinder
  • Dismount the piston by following the procedure given in Manual
Liner Removal procedure for MAN engine (MC and ME engines)
Ensure the Liner lifting tool is well maintained. Two lifting screws are used with a lifting hook connected via chain. Ensure chain, screw and lifting hook are fastened together with no deformation
  • Ensure the safety strap in the lifting hook is working properly.
  • Tighten the two lifting tool screws in the liner as per the rated torque is given in the manual on both sides.
  • Measure that there is no gap between liner surface and screw landing surface after tightening, using a 0.05mm feeler gauge.
  • Disconnect the cylinder oil pipe connections. 
  • And screw of the non-return valves.
  • Dismount the four cooling water pipes between the cooling jacket and cylinder cover and clean them carefully.
  • Remove the screws of cooling water inlet pipe.
  • Attach the crossbar to engine room crane. This completes the lifting arrangement for cylinder liner.



Hook the chain from the lifting cross bar on the lifting screws and lift the cylinder liner with the cooling jacket out of the cylinder frame.

What to do if Cylinder Liner is Stuck
  • A common way to remove a stuck cylinder liner is to use hydraulic jacks on the bottom of the cylinder liner and apply hydraulic pressure.
  • Once the liner is slightly moved out of the stuck engine structure, it may be then lifted with the help of engine room crane and lifting tool
After Removing the liner from the engine:
  • Place the cylinder liner vertically on a wooden plank
  • Clean cylinder frame internally paying special attention to the contact surfaces for the cylinder liner at the top of the cylinder frame
  • Discard the O-ring on the cooling water pipe
  • Clean the pipe carefully
  • Make sure to inspect the liner for cracks and other defects

Refrigeration Compressor Starting Unloader

  • At a star-delta start of electric motors it is often considered necessary to limit the compression work of the machine at the starting moment in order to reduce the starting torque of the electric motor. 
  • Usually, a solenoid valve is used in a by-pass arrangement which in the starting up phase short circuits the discharge side to the suction side of the compressor.
  •  At the same time, a non-return valve must be fitted in the discharge line to the condenser preventing the return flow of discharge gas to the compressor.
  • When the electric motor has reached its max. number of revolutions per minute, a switch takes place from star to delta start. 
  • The solenoid valve is closed and the compressor now works under normal conditions.

Sludge formation in Refer system

Acid content inside a system can emulsify with the compressor oil to form an aggressive oil sludge that reduces lubrication properties. This can lead to serious compressor damage.
Sludge can also cause a variety of other problems in a system, such as blockages of strainers, expansion valves and other tiny passage

Corrosion in Refer system

  • Moisture can cause corrosion. However, moisture in combination with a HCFC refrigerant containing chlorine (like for example R-22 or R-409A) creates much more serious corrosion, as the chlorine hydrolyses with the water to form hydrochloric acid (HCl) which is aggressive to most metals. Heat adds significantly to the problem by accelerating the acid-forming process.
  •  For HFC refrigerants (like R-404A or R-407C), it is the polyolester oils that are very hygroscopic and may decompose at high temperatures forming hydrofluoric acid with the moisture which could be introduced to the system through a sub-standard refrigerant.

York Antwerp Rule

There is a general average act when and only when, any extraordinary sacrifice or expenditure is intentionally and reasonably made or incurred for the common safety for preserving from peril the property involved in common maritime adventure

Certificate of Proficiency (COP) and Competency (COC)

Certificate of Proficiency (COP) refers to a certificate, other than a certificate of competency issued to a seafarer, stating that the relevant requirements of training, competencies or seagoing service in the Convention have been met.
Able seafarer deck :Person qualified in accordance with the provisions of regulation II/5 of the STCW Convention
Able seafarer engine :Person qualified in accordance with the provisions of regulation III/5 of the STCW ConventionAble seafarers whether deck or engine are given Certificate of Proficiency (COP)

Competency (COC) refers to the possession and demonstration/application of the knowledge, understanding and proficiency required of seafarers under the Convention.
Electro - technical officer :Person qualified in accordance with the provisions of regulation III/6 of the STCW ConventionETO is given Certificate of competency (COC).