1. Lubrication features of a large diesel engine
In some engines such as long and superlong stroke engines, the piston is not directly connected to the crank pin via a connecting rod.
The piston has a piston rod extending from the bottom of the piston.
The piston rod is then connected to the connecting rod at the crosshead bearing.
The crosshead bearing has a to and fro motion and therefore a continuous hydrodynamic film cannot form.
Therefore oil has to be pumped to the crosshead bearing at a predetermined pressure in order to take the loads of compression and combustion.
The crosshead is connected to the crank pin via a connecting rod.

2. Platform separating cylinder from crank case
Piston
Ref:
Piston rings
Piston skirt
Piston rod
Platform separating cylinder from crank case
Stuffing box
Crosshead, crosshead bearing (reciprocating)
Oil pumped at a certain pressure
Connecting rod
Crank pin, bottom end bearing (rotatory motion)
Journal, journal bearing (rotatory motion)
Web

3. Cylinder liner lubrication
In some engines, lubricating oil in the cylinder is different from the oil supplied to the other bearings.
The cylinder oil contains additives to withstand the high temperatures and contaminants from combustion products.
The oil is slightly basic in nature to counter the acids formed from combustion.
Scraper rings spread the oil over the liner surface.
Lub. oil is usually injected between the two scraper rings.
Oil is injected at a predetermined period during the downward stroke.
Before starting, oil is pumped into the liner by manual priming methods.
After starting, the oil pump is driven by the engine through a cam shaft.

4. Cylinder liner
Compression rings
Scraper rings
Oil injection passage
Piston
Injection points
Cylinder oil pump/lubricator
Handle
Camshaft

5. Trunk type engine (no piston rod)- Splash type lubrication
Cylinder liner
Piston rings
Oil is picked up by the webs while rotating, and splashed onto the piston and liner
Gudgeon pin
Connecting rod
Crank pin, bottom end bearing (rotatory motion)
Journal, journal bearing (rotatory motion)
Web extension
Oil
Web

6. CROSSHEAD LUBRICATION
Piston rod
Telescopic pipes (one moves inside the other)
Oil supply
Movement of crosshead
Crosshead bearing
Movement of bearing
Stationary pipe
Connecting rod

7. Journal bearing Journal Bearing Oil supply
The journal bearing may undergo hydrodynamic lubrication or a combination of hydrodynamic and hydrostatic (externally pressurized) lubrication.
The oil supply may be from any one or number of positions, depending on the design.

8. Oil passage between bearings in a unit
TRUNK TYPE ENGINE
Gudgeon pin
Connecting rod
Crank pin
Web
Journal
Oil passage (drilled)

9. Lubrication system TG- Temperature gauge PG- Pressure gauge ENGINE
Shaft
Bearings PG
Cooler TG PG
Storage tank
Pump
Filter 9 9

10. Engine sump ENGINE Shaft Bearing Connection for filling the tank Pump
Storage tank/sump
strainer
The storage tank usually forms the bottom-most compartment of the engine.
It is also sometimes known as the sump.
Oil from the sump is usually transported to the bearings by an engine driven pump or an independently electric motor driven pump that transports the oil to the journal bearings.
Through passages drilled in the crank shaft and webs, it is transported to the crank pin.
Usually a strainer is provided on the suction side of the pump to prevent large contaminant particles from damaging the pump and bearings.

11. Oil cooler- tube and shell type
Oil in PG TG TG TG
Water in
Water out PG PG PG TG
Oil out
In this case, cooling water flows through the tubes.
Oil flows in the shell around the tubes and passes the heat to the water.
The in/out temperatures of the oil and water are to be monitored.
Oil pressure is always kept above water pressure to prevent water contamination of oil
However, if there is a leak oil is lost and the sump level is therefore to be monitored regularly

12. Engine lubrication system
Some adverse situations:
Oil inlet pressure to engine LOW
Oil outlet temperature from engine HIGH
Oil outlet temperature from cooler HIGH
TG- Temperature gauge
PG- Pressure gauge TG PG
ENGINE
Shaft
Bearings PG
Cooler TG PG
Storage tank
Pump
Filter 12 12

13. Adverse situations and reasons
All pressure and temperature values in a lubrication system have to be constantly monitored
Oil inlet pressure to engine LOW
Filter may be choked blocking flow.
Pump defective.
Oil outlet temperature from engine HIGH
Bearing maybe running hot due to excessive friction.
Leakage of gas from combustion space past piston rings.
Oil outlet temperature from cooler HIGH
Water flow may be restricted due to choked tubes.
Surface of tubes maybe coated with dirt.
Temperature of oil outlet from cooler too LOW (excess viscosity)
Water temperature may be too low- restrict water flow by partially shutting valve.

14. Other maintenance and problem issues
With engine is shut down
Oil filters should be cleaned regularly
Cooler tubes to be cleaned
Oil level in the sump is to be monitored regularly
Low level is indicative of oil leakage somewhere in the system
Can be at the cooler (oil flowing into water side)
At the pump
At the valves
Check constantly around the engine spaces for accumulation of oil

15. Lubricating oil pumps
Lubrication pumps are positive displacement pumps-
They supply a definite amount of fluid for each cycle of rotation regardless of resistance which may oppose the transfer.
They do not need any initial priming
Different types are:
Reciprocating
Piston, plunger
Rotary
Vane, piston, screw, gear, lobe and screw

16. Reciprocating piston pump
Ref:
In a reciprocating pump, a volume of liquid is drawn into the cylinder through the suction valve on the intake stroke and is discharged under positive pressure through the outlet valves on the discharge stroke.
The discharge from a reciprocating pump is pulsating and changes only when the speed of the pump is changed.
Often an air chamber is connected on the discharge side of the pump to provide a more even flow by evening out the pressure surges. Reciprocating pumps are often used for sludge and slurry.

17. Gear pump
Consists of two meshing gear wheels housed in a tight fit casing.
The gears rotate in opposite directions and the vacuum created due to this, draws the fluid into the inlet side of the pump.
The fluid is trapped in the spaces between the teeth and casing to be carried round from the suction to the delivery side
Fluid is displaced when gear teeth mesh
Therefore there is a continuous transfer of liquid from suction to delivery side
The theoretical volume displacement is given by
do = outside diameter
dr = root diameter
N = rps
w = depth of gear perpendicular to the screen