Diesel Generator Overhauling Procedure-21-22 Best Practice [PDF]

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25/9/2021

Diesel Generator Overhauling Procedure-21-22 Best Practice

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21-22 Best Practice Of|Diesel Generator Overhauling January 15, 2021 by Marinediesel

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Introduction to Diesel Generator Overhauling Procedure In this post, we shall explain the Diesel Generator Overhauling Procedure. The diesel generating schedule has presented in a simplified way and language.

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The DG Sets (Diesel generating sets) are the only source of Power on board a ship. It is not possible to operate any machinery without the Diesel generating sets. As per the power requirement, various types of Diesel Generators are used. For the proper maintenance of Diesel generators, Engineers should understand the the following. https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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1.  knowledge of design, construction 2. Working of the machine. 3. Overhauling Procedure and the maintenance works: There are standard procedures for the Diesel Generator Overhauling Procedure and maintenance of these machines, irrespective of their design and manufacturing.

Diesel Generator Overhauling Procedure–Major Overhauling/De-carbonisation: The process of dismantling, cleaning, and removal of carbon deposits from the following parts. Piston Cylinder Liner Cylinder head

Major maintenance/ Decarbonisation is carried out on the following occasions. Completion of running hours as per the planned maintenance program of OEM (Original equipment manufacturer). Accident/Breakdown. Before continuous survey in which process of change of running parts like and piston rings etc. There are standard procedures for the maintenance of these machines, irrespective of their design and manufacturing. Planning;- Planning of maintenance is to done keeping the following points in view.

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MakeShift arrangements for the emergency in the event of Power failure Special Tools and tackles to be beforehand in proper operating condition. Measuring Instruments and tools: All measuring tools gauging and measuring devices should be in suitable working conditions with a reasonable calibration period. Spare Parts: check and ensure the availability of spares needed to accomplish the maintenance. To ensure the working of Power Packs if available on board. Engineers/technicians to be involved in the care should know the procedure as per the Operating manual. The maintenance team should have Knowledge of symbols and signs used to indicate the safety of machinery.

Real Life Incidences Onboard, a ship inventory of the spares was not taken by the engineer in charge. While the maintenance on the way, during the inspection, it came to the light that the Con-rod bolts were elongated and needed replacement. Since the bolts were not available in the ship’s stock and the overhauling period was extended. Due to this delay company has to lose the revenue for not taking the container with perishable goods because of lack of power. Before the hydraulic tool’s maintenance pump for loosening the Cylinder head, Main Bearing and Con-rod nuts were not building pressure. During the maintenance engineer –in charge found out that the nuts were not getting loosened up, and hence dismantling work couldn’t be started. Ultimately it caused the delay in maintenance. Very often has been observed that due to the proper upkeep and maintenance of Measuring instruments/ calibration of the same in the stipulated period, many instruments fail to operate or lead to inaccurate measurements.

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Preparation Prior to maintenance following preparation is essential. Quarantine Tagging Out Inspection of special tools supplied by Manufacturer. Knowledge of functioning and procedure for operating the devices. Referring to the correct tightening torque and hydraulic pressure values. Complete understanding of parts assembly. Preparation of safety regulations for safe working. Quarantine: – Before the maintenance start, the machine is to be quarantined for care to avoid any operating fluids spilling and injury/accidents. Both the Prime mover and alternator are to be quarantined. Following steps are to be taken to isolate the Electrical and mechanical system. Open the ACB ( Air Circuit Breaker) to cut off the link between the Alternator and the bus bar. The power supply of Pre-Lube oil Pump. Oil supply to Engine Cooling water supply Lube oil Fuel oil supply Air supply A checklist of all the isolated areas is to be prepared, and the same is to be referred to before reopening the systems. During the isolating process/opening procedure, a slow action with close observation is to be adhered to to ensure other equipment is not https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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affected during this process. Add on safety: While the maintenance work is in progress, additional tagging out is to be carried out to prevent any opening up of Valves or Electrical breakers resulting in an accident of serious nature. The following special tools: supplied by the engine manufacturer are to check for their correct working, calibration, and leakage on the hydraulic device. Injector and starting valve opening tool Spanners Cylinder head opening tool Cylinder liner Removal Tools Cylinder Liner Holding Tool Cylinder head lifting tool Piston Lifting tool Bearing removal tool Cylinder Head and con rod nuts loosening and tightening hydraulic tool Valve grinding tool Valve seat grinding machine/tool Injector testing tool Rope and ceilings with proper size D shackles. Overhead cranes. Engine Barring arrangements Cylinder Liner Brushing tool Piston Ring removal tool Piston guide tool for inserting the piston. All the pressure and temperature calibration instruments. Electrical measuring instruments.

Points to be followed for assembly Engineer in charge should know assembly of parts and doubt Instruction manual/Consult with Senior Engineer. https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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Store all the dismantled components in a separate box with the marking on significant parts. For each unit, a separate container to be used. Mark all the bearings and con-rod bolts and wrap the threads with the cloth to avoid the threads’ damage.

Dismantling of parts Overhauling of Generator is governed by the following factors. No. of Running hours clocked. Company’s policy. Order of wear down of individual parts is as under 1. Cylinder Head & Piston Rings 2. Cylinder Liner and Connecting Rods 3. Bearings. Due to the forthcoming Voyage or defect/incident, all the Dismantle all the significant parts including Main and con-rod bearings. In addition to the above Engine parts, undertake the overhauling of the following components as per the maintenance schedule laid down in the Instruction manufacturer’s manual. Carry out the following jobs.

Cylinder Heads All cylinder heads are de-carbonized. Inspect cylinder heads. Inspect Valve spindles.

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Carry out the Inspection of Inlet, Exhaust valves & Inlet valve guides. Record the measurements. Replace the Corroded & wornout valve guides with the new one. Inspect valve seats and reject the excessively dented, pitted, and uneven working surfaces. Accepted valve seats are to be regrounded with the machine. Dismantle all the valve rotators for inspection. Observe for deep markings on the inclined surfaces of ball pockets. Inspect all the Injector Sleeves and record the observations. Adjust the opening pressure to 170 bars. Inspect Indicator valves. Inspect cylinder head cooling water spaces.  Carry out the lapping of cylinder head seating face. Carry out the pressure testing of all the cylinder heads.  Carry out all Cylinder head valve seat grinding work fo. Old/new seats.  All Water guide jackets are to be removed, clean, inspect and fit back with new O rings. Tighten all the nuts for cylinder heads with prescribed torque as per the OEM instructional manual.

Cylinder Liner Pull out all cylinder liners for inspection. Inspection/ bore measurement and honing to be carried out at workshop as per OEM procedures for Inspection and Honing of Cylinder liner. Enter the records of size into the forms.   Carry out the lapping of the cylinder liner’s upper face. Replace all the flame rings with an excessive worn-out working surface.

Piston and Piston Ring  https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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Withdraw all pistons for inspection and overhauling. De-carbonization of all the pistons (The pistons are to be cleaned both from inside and outside )  Clean all piston and oil scraper ring grooves, inspect and measure for wear with groove measuring tool supplied by OEM. Record the measurements. Replace all piston rings with the new one.  Confirm the piston ring position is offsetting the ring joint 1800 to each other, and the spring joint of the scraper ring also fitted 1800 offset to ring joint while mounting the Pistons. Check the Piston plug tightness on specified torque.

Connecting Rod Inspect all Connecting rod big-end bearing shells and replace if found with the deep grooves and excessive wear down more than the accepted norms for the shell thickness and free spread. Check the Connecting rod big end bore and record the measurements. Check the Small end bearings. Check the clearance between the wrist pin and bush. All the piston pins are to be subjected to an ultrasonic test to check hairline cracks.

Thumb rule for oil clearance calculations ( Important guidelines checks during Diesel Generator Overhauling Procedure ) Thumb rule for oil clearance calculations 0.01905mm to 0.0254 mm. (Three quarter to 0.0254 of a millimeter) of clearance per mm of a shaft diameter is the reasonable starting point.

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For example 2 mm shaft diameter would require 0.0381mm to 0.0508mm (0.01905×2=0381 and 0.0254×2=0.0508mm) For the super performance, engines add 0.0127 to the maximum calculated value. The recommendations for 2 mm shaft will be 0.0508 mm + 0.0127=0.0635mm. ( For the purpose of maintaining hydrodynamic lubrication between the shaft and bearing the maximum ovality should not be greater than the maximum oil clearance. If exceeded then there will be bearing failure due to boundary lubrication.)

Camshaft and Camshaft Bearings Inspect all gear wheels bolt and connection as per OEM instructions. Replace all Camshaft bush if found worn-out Check the condition of a camshaft. Check the lubrication of the camshaft. Observe the flow of lube oil from all the bearings and spray pipe nozzles. The oil jet should be hitting at the gearwheel right at the meshing point. Check the tightness of all the fasteners, including locking devices. Inspect all pushrods for straightness. Adjust inlet valve and exhaust clearances as per the OEM recommendations.

Inlet Valve, Exhaust Valve, and fuel injection pumps operating mechanism (Diesel Generator Overhauling Procedure) Inspect the Roller Guide for Event of any marks.  Deformation on the spherical stud.

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Inspect the Surface of rollers for any mark or deformation. Check for free play between the rollers and the bush and the pin. Check the Valve Gear, springs, and Pushrods. Inspect all the valve bridge springs, Rocker arm brackets, and pushrods. Check the Roller Guide for fuel injection pumps. Inspect all the roller guides for any marks. Check the Surface of rollers for any defects and deformation. Check for free play between rollers, bush, and pin. Check the lubrication of all the operating gears.

Governor Overhaul the Governor.                                                                       Change the Governor oil.

Crankshaft and Main Bearings Inspect all the crankpins: Polish all main &CR pins with glossy paper. Inspect & replace thrust bearings if wear is more than the prescribed limit. Re-tighten counterweights at the specified torque. Dismantle all main directions & Polish all the Crank-pin. Check the runout. Carry out the Tightening of main and guide bearing caps at the prescribed torque. Check and replace all main bearing if found with abnormal wear down.

Turbocharger & Charge Air Cooler checks during Diesel Generator Overhauling Procedure https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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Remove the TC cartridge. Change nozzle ring. Dismantle the cartridge and inspect the bush and labyrinth ring, and change if required. Re-assemble the cartridge Check the clearances as per the procedure. Clean the CAC (Charge Air cooler). Pressure tests the CAC.

Engine Frame and Bed Plate (Diesel Generator Overhauling Procedure) Re-tighten of Holding down bolts. Re-tighten the bolts between the engine and base frame. Carry out the functional test of safety covers. Check the AVM paid adjusting screw clearance and adjusts if required.

Fuel oil System Calibrate the Fuel injection valves. Check all high-pressure fuel pipes & replace “O” rings. Check FIP roller, and measure nominal height.  Overhaul all the Fuel Injection Pumps. Replace barrel, plunger & ‘O’ ring kit.

Lube Oil System checks during Diesel Generator Overhauling Procedure Remove the engine-driven Lube oil Pump for inspection. Dismantle  the complete pump and change the bushes.  https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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Apply the correct torque for tightening the self locking nut. Remove old oil from the engine and charge new oil. Overhaul Pre-lube oil pump. Replace the Lube oil filter cartridge. Clean and replace the kit of Glacier (bypass filter). Clean the Lube oil PHE ( Plate Heat Exchanger) by circulation with the chemical.

 Cooling Water System checks during Diesel Generator Overhauling Procedure Dismount LT (Low Temperature) and HT (High Temperature) water pumps from the engine. Carry out the complete overhauling of pumps. Change the rotating sealing and both ball bearings of the HT Water Pump. Change the rotating sealing and both ball bearings of the LT water Pump. Tighten self-locking nuts of both the pumps at the specified torque. Carry out the overhauling of the HT water thermostatic valve. Clean the LT/HT PHE.

Mechanical Over-speed Overhaul the Mechanical over speed device.

Miscellaneous (Diesel Generator Overhauling Procedure) These points are very important for the Diesel Generator Overhauling Procedure. https://www.marinediesel.co.in/diesel-generator-overhauling-procedure-major-maintenance-decarbonization/

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Record Fuel pump index at Governor Index 0. Check the compressed air system of the engine. Check the fuel oil system and nozzle cooling system. Carry out the functional tests of Safety shutdown switches and analog switches. Calibrate all safety switches If required, replace the Alternator bearing. On completion of maintenance work, Start the D.G. Set and follow all moving parts’ sequence as per the standard procedure of Diesel Generator Overhauling Procedure. Carry out the load trials of the D.G. Set as per the OEM protocol. Record the set’s performance in stage load sequence from 25% to maximum available load for the machine prescribed in Manual. Monitor the parameters and record them in Logbook.

Data for pressure and Tolerances

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