The authors and editors have made every possible effort to ensure the accuracy of the information provided in the book. Insufficient lubrication: If the bearing lubrication on the crankshaft is starved, it can lead to bearing wear and crankshaft failure.
Crankshaft Inspection Crankshaft should be frequently
Crankshaft Deflection
If the ship is located in the tropical sunny zone (high temperature) on one side of the ship, taking. The deflection meter reading should be recorded on the measuring sheet (provided with the e-book).
Material
The connecting rod in a two-stroke marine engine is used to connect the crankshaft and piston (via the cross and piston rod) for transmitting the force of the piston to the crankshaft.
Reasons Behind Failure of Connecting Rod
Inspection of Con- Rod
The guide and guide shoe run on the guide rail to support the cross head pin and to. Each crosshead consists of a steel casting into which the crosshead pin is crimped, with the sidebar screwed into the top of the casting.
Inspection
Clearnaces
Difference Between MAN B&W and SULZER Crossheads
Design and Material
In MAN engine: The cooling oil comes from main bearing to the cross heads and then reaches the crown through the bores provided in the piston rod. In SULZER engine: The cooling oil comes to the piston from an articulated or swing arm which supplies lubricating oil against system pressure.
Types of 2 Stroke Piston
The new MAN engine uses simple cooling piston and jet nozzles, which consist of oil passage in the piston crown for uniform cooling. The latest development in MAN engine pistons is the OROS Piston, which has a topland with double convex valleys.
Common Problems in Piston
Inspection of Piston
Measurement and Test
Piston top wear is measured using a template placed on top of the piston and the clearance between the template. It is important to pressure test a piston that has been removed from the unit and cleaned for reuse. Place the pressure test tool on the palm of the piston and make sure there is no water leaking from the fitting.
Connect the air hose to the test instrument and supply air pressure up to 7 bar Max. Keep the piston pressure charged for 2-3 hours and check that the pressure is stagnant indicating no leakage.
Difference Between SULZER and MAN Piston
The main function of piston rings in the combustion chamber is to seal the space and prevent the escape of gases to the lower part of the engine. That is, if the rings seal the combustion chamber properly, it will help the piston compress the air fuel. efficient mixing.
Types
The main task of the piston rings in the combustion chamber is to seal the space and prevent gases from leaking into the lower part of the engine, i.e. under the piston area and engine cover.
Construction of Piston Rings
The oval pot cam turning method is expensive, but the rings produced using this method retain their tension while operating in the heat of the engine. By changing the cam shape and the oval shape, the pressure distribution around the ring is changed and a stress is induced. After the pot is machined, a gap of about 7-13% diameter is cut in the ring and rings are milled on the flanks to ensure good sealing in the piston ring grooves.
The piston rings used in marine engines must be harder than the lining material in which they are used. It is generally used on the piston ring treads and on the landing surfaces, i.e.
Inspection of Piston Rings
Clearances in Piston Rings
Butt Clearance: It is the clearance between the end of the ring in the liner. The ring is placed in the liner and the impression can be made on paper by applying Prussian blue paste to the ends. The lining in the combustion chamber of the marine engine carries the piston and transfers the heat generated in the process.
Since the upper part of the liner is always exposed to combustion gases, it is subjected to it the most. This design allows increased liner thickness without increasing thermal stress and also aids durability.
Liner Material
With the use of a turbocharger and an increase in engine power, the mechanical stresses on this thin liner resulted in cracks and other mechanical failures.
Problems in Liner
Corrosion: The wear due to corrosion is caused due to the burning of heavy fuel oil in the combustion space. Corrosion due to sulfur will be high due to the presence of water in fuel and condensate in the air. Abrasion: This type of wear is due to the hard particles present and formed during combustion.
As a result of this type of wear, the liner loses its ability to adhere the cylinder oil to the surface. Varnishing: Varnishing is caused by organic and inorganic salts that cause the accumulation of calcium deposits in.
Liner Inspection
Liner wear rate: The wear rate can be described as the wear surface in mm per 1000 engine operating hours. Cloverleaf - corrosive wear between the lubrication ports if the cylinder oil cannot neutralize the acidic combustion products.
Liner Calibration
Cylinder liner wear is measured using a standard template, which consists of strategically placed holes, into which the micrometer is placed and the. If the wear is not the same in both directions, the ovality of the liner is checked. Wear will be greater in the upper third due to the high combustion temperature and pressure.
Difference Between MAN B&W and SULZER Liners
One of the main functions of the cylinder head is to seal the combustion chamber and accommodate other auxiliary parts such as the fuel injector, air start valve,.
Types of Heads
Some models of SULZER engines (RTA series) also have a two-part cylinder cover - an inner and an outer part. The inner piece is also known as the cylinder wing, which is made of cast iron and the outer cylinder is made of cast steel; both are connected in one piece. SULZER and MAN high KW engine covers use three fuel valves located on top of the cylinder head, forming a triangle.
Problems in Cylinder Head
Inspection of Cylinder Head
The exhaust valve of a 2-stroke marine engine is installed centrally over the top of the cylinder head to allow all exhaust generated within the chamber during the combustion process to be transferred to the exhaust trunk. Exhaust valve body: The outer body of the exhaust valve consists of holes for the passage of cooling water, guides for. Spindle Exhaust Valve: The spindle valve can be separated from the body so that it can be ground and rebuilt after a period of time or when required.
When the exhaust gases pass through these vanes, it rotates the valve to avoid local distortion of the valve and valve seat. Exhaust Valve Seat: The exhaust valve seat is a detachable part that can be rebuilt or replaced if damaged.
Types of Exhaust Valves
With better operating conditions and reduced wear, this system is now used in modern marine engines. Hydraulic exhaust valve with mechanical spring: Some exhaust valves have springs mounted on top of the hydraulic actuation system. Hydraulic exhaust valve with pneumatic spring: In modern engines, the mechanical spring is replaced by.
Problems in Exhaust Valve
Inspection of Exhaust Valve
Latest Technology and Development
Variable exhaust valve closing: In this system, the valve closing time is varied without disturbing the valve lift. This is done to optimize the performance of the exhaust valve in the normal load range where the closing point is.
Clearances in Exhaust Valve
MAIN BEARING
- Bridge with Depth Gauge
- Bridge With Feeler Gauge: In some engines, after removing the shell and the
- Telescopic or Swedish Feeler Gauge
- Dial type Depth Gauge: This method is used in new MAN B&W engines (SMC-
Steel back: The steel back is the final and supporting part of the bearing used for form and support, on which all the layers are bonded together. The main function of the bonding layer is to obtain a good bond between the shell and the top layer. Measuring the main bearing clearance determines the amount of wear the bearing has undergone.
The total depth on the scale is measured and . compared to the previous reading and the reading in the manual to calculate bearing wear. On engines such as MAN B&W this is the most commonly used method to measure the bearing clearance of the upper shell.
Difference Between SULZER and MAN Main Bearings
In some models, jack bolts are used to hold
Waisted stud bolts are used to hold the main
Upper half of the keep is lined with white metal
A separate shell is installed in the upper
White metal thin shell bearing is used
Tri metal thin shell bearing is used
Locating dowel is
Counter sunk screw is provided to hold the
Crosshead bearing
The top clearance between the journal and the new bearing shell is the result of a compilation of the manufacturing tolerances of the bearing assemblies. In the MAN engine, the grooved lower shell is made of SnAL40 and the upper shell is made of white metal. Whereas in SULZER, the bearing shell is thin-walled in white metal for high bearing capacity.
Measure the clearance in the crosshead bearings through the thrust piece inspection hole by inserting a feeler gauge into the top of the upper bearing housing. When checking the clearance, the deviation between the actual and measured values is determined, and if it exceeds 0.1 mm, it is necessary to inspect the cross bearing.
Crank Pin Bearing
Measure the play in the crankpin bearing by inserting a feeler gauge into the bottom of the bearing shell on both sides. When checking the clearance, the difference between the actual and measured value is noted and if it is greater than 0.1 mm, the crosshead bearing should be inspected. The wear limit for the crankpin bearing shells is based on an assessment of the bearing condition at that time.
Thick-walled shell bearings fitted in some engines have clearance adjusted by fitting shims between the bearing halves.
Thrust Bearing
At the bottom of the bearing is an oil pan with an outlet to the oil pan. The clearance in the release bearing is measured during pilot testing of the engine. With the SULZER engine, reversing the engine is done by changing the direction of rotation of the camshaft.
The most important part of the camshaft is the CAM, which controls or operates the exhaust valve and the fuel pump. Turn the camshaft using a tool until the mark lines up with both sides of the pin gauge.
Fuel Pump
Hold the dial gauge above the suction valve with a pre-tension of 1 mm and set it to '0'. Place a dial indicator over the top of the overflow valve with a preload of 1mm and set it to '0'. The fuel pump cable is the distance from the top of the fuel pump plunger when lifted above the top edge of the upper cut-off holes of the fuel pump cylinder, when the piston of the same unit is at TDC.
Rotate FORWARD until the lower edge of the cross bore in the piston reaches the exact position where it closes the upper edge of the lower cut holes. Adjust the bracket of the measuring tool until the piston of the dial gauge is almost in the bottom position.
Conclusion
