Oil lubricated stern tubes

In the name of Allah who is the most beneficient and merciful

Progress from sea water to early oil lubricated stern tubes involved exchange of the wood lined bronze carrier
for a while metal lined, cast iron bush. oil retention and exclusion of sea water. necessitated the fitted of an
external face type seal. The stuffing box was returned in many early oil lubricated stern tubes at the inboard end.

the latter designs with an extended length boss built into the stern frame provide better support for the white metal lined
bearing. A minimum bearing length of two times the shaft diameter will ensure that bearing load doesnot exceed 0.8 N/MM2

the tube is fbricated and welded direct to the extension of the stern tube frame boss at the after end and to the aft peak bulkhead at the forward end.

oil contaminated with in simplex type stern tube by lip seal. The elastic lip of each nitrile rubber seal liners at outboard and inboard end of the steel propeller shaft.
The outboard liner additionally protects the steel shaft from sea water contact and corrosion.

Heat produced by the friction will result in hardening and loss of elasticity of the rubber, should temperature of the seal material exceed 110c. cooling
at the outboard end is provided by the sea. Oil circulation aided by convention, is arrranged to maintain low temperature of seals at the inboard end.
connections  are fitted top and bottom between the two inboard seals.

The chrome steel liners act as rubbing surfaces for the rubber lip seals and grooving from fricitional wear has occurred. The problem has been overcome by using a ceramic
filler for the groove or alternately a distance piece to axially displace the seal and ring assembly. Allowance must be made for relative movement of shaft and stern tube due to
differential expansion. New seals are fitted by cutting and vulcanizing in position.

Lip seals will accept misalignment but a floating ring design was introduced by one maker.


WRITTEN BY S/C ZEESHAH AHMED
LECTURE BY: CHIEF ENGR. Tahir jamil
Phone no. 03344011232
EMAIL: ZEETEC4@YAHOO.COM
date: 03.nov.2009

Microbial degradation of oil

In the name of Allah who is the most beneficient and merciful

Microbial degration of oil is the possible infection of an oil system by micro organisms. these live
by consuming hydrocarbons in the base oil togather with nitrogen, sulphur and phosphorus from additives.
if water is present they will multiply rapidly in the warm, agitated conditions in the oil system. contamins is
humids climates or accidental entry of dirt and water during overhaul.

infection by microorganisms will form organic acids and more water while depleting the additives. This will cause
corrosions and wear of metal surfaces(particularly bearing metals) and will create sludge and slime that choke oil filters.
The oil may be prone to emulsification and saponification.

Test for microbial infection make use of a special gel which is either dipped in the oil or has oil poured over it and is then
incubated to develop a growth or culture. the appearance of this culture is then compared visually with a standard coloured
chart, to indicate the degree of contamination if any. If the oil doesnot wet the get, it may be necessary to mix the sample with a
small quantity of sterile water.

contamination doesnot commonly occur if cleanliness and care are exercised and water is eliminated from the sytem. Recommendations are that a
maximum of 0.2 % of water content must not be exceeded when using detergent oils.


WRITTEN BY S/C ZEESHAH AHMED
LECTURE BY: CHIEF ENGR. Tahir jamil
Phone no. 03344011232
EMAIL: ZEETEC4@YAHOO.COM
date: 03.nov.2009

Crankcase oil mist detector

In the name of Allah who is the most beneficient and merciful               

This device is fitted to monitor the presence of an oil mist in the crankcase. In this monitoring process samples of the air and vapours mixture taken continually from the crankcase of a diesel engine. This device will detect the level of oil mist concentration which must remain below level. At which explosion may occur. In case of coming to this level a warning is given to allow avoiding action to slow the engineer and prevent serious damages and explosion.

The presence of an oil mist in the crankcase is the result of oil vaporization caused by a “Hot spot” this hotspot is produced by other heating of any engine bearing or overheating of any other moving parts of the engine time chain or gear drives. Explosive condition can result if build up of oil mist is allowed. Hence continuous monitoring of vapours intensity is required. A diagrammatic view of an oil mist detector is shown in the sketch.

Measure any increase in oil mist density. The detector consists basically of two parallel tubes of equalize, each having an electric current directly proportional to the intensity of light falling on the surface. Lenses are fitted to seal the tube ends of each tube but allow light to pass. One tube is sealed to contain clean air and is termed the reference tube. The other tube is called Measuring tube, has connections through which samples of the crankcase vapours are drawn by extractor fan. If the concentration of explosive mixture is reached in the oil mist sample, light will be obscured(not clear) before reaching the cell of measuring tube, electrical balance between two cells will be disturbed and an alarm will be operated indicating excess concentrations in oil mist. Sampling points should be fitted to each cylinders crankcase and their connections are brought to a rotating selector valve which is driven from the fan motor. This repeatedly connects each sampling point  to the measuring tube in sequence.

In the event of oil mist being detected the rotator stops to indicate which sampling will commence again its sequence.
The detector should be checked daily and the sensitivity tested. Lenses and mirrors should be cleaned periodically. Two identical beams of light from a common lamp are reflected by mirrors to pass along the tube on to the cells which are then in electrical balance and if light will be obscured before reaching the cells, electrical balance will be distured and an alarm will be operated.


WRITTEN BY: S/C ZEESHAN AHMED
LECTURED BY: CH. ENGR. YASEEN SAHAB
DATE: 23/OCT/2009
TIME: 11:17 AM

oil lubricated stern tubes

oil lubricated stern tubes
Progress from sea water to early oil lubricated stern tubes involved exchange of the wood lined bronze carrier
for a while metal lined, cast iron bush. oil retention and exclusion of sea water. necessitated the fitted of an
external face type seal. The stuffing box was returned in many early oil lubricated stern tubes at the inboard end.

the latter designs with an extended length boss built into the stern frame provide better support for the white metal lined
bearing. A minimum bearing length of two times the shaft diameter will ensure that bearing load doesnot exceed 0.8 N/MM2

the tube is fbricated and welded direct to the extension of the stern tube frame boss at the after end and to the aft peak bulkhead at the forward end.

oil contaminated with in simplex type stern tube by lip seal. The elastic lip of each nitrile rubber seal liners at outboard and inboard end of the steel propeller shaft.
The outboard liner additionally protects the steel shaft from sea water contact and corrosion.

Heat produced by the friction will result in hardening and loss of elasticity of the rubber, should temperature of the seal material exceed 110c. cooling
at the outboard end is provided by the sea. Oil circulation aided by convention, is arrranged to maintain low temperature of seals at the inboard end.
connections are fitted top and bottom between the two inboard seals.

The chrome steel liners act as rubbing surfaces for the rubber lip seals and grooving from fricitional wear has occurred. The problem has been overcome by using a ceramic
filler for the groove or alternately a distance piece to axially displace the seal and ring assembly. Allowance must be made for relative movement of shaft and stern tube due to
differential expansion. New seals are fitted by cutting and vulcanizing in position.

Lip seals will accept misalignment but a floating ring design was introduced by one maker.


WRITTEN BY S/C ZEESHAH AHMED
LECTURE BY: CHIEF ENGR. Tahir jamil
Phone no. 03344011232
EMAIL: ZEETEC4@YAHOO.COM
date: 03.nov.2009

Lubricating oil system

In the name of Allah who is the most beneficient and merciful
Lubricating oil system:
In the lub oil system, oil os supplied to all bearing, pistons cooilng, sprayer, exhaust vv, actuators, controlled system,
guides, gears , chain drivers , and ( cycinder in trunk piston engines). lay out of lubricating system for a large main engine is
shown in the sketch.
lub oil presssure pumps draws oil form engine drain tank (sump tank) through suction strainer and discharge through fine filter
to enigne and distributed to bearings, pisotns, and other parts as mentioned above.
Pressure pumps , strainers and filters are in duplicate, one set is being used while other acts as a standby. Fine filter
should be capable to clean the oil without interupption flow of oil.(mesh size 50 microns).
WRITTEN BY S/C ZEESHAH AHMED
LECTURE BY: CHIEF ENGR. YASEEN SAHAB
EMAIL: ZEETEC4@YAHOO.COM
date: 14.july.2009
link: zeetec4.googlepages.com
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