Oil Mist Detector Alarm: Actions to be taken and what to do or not

Oil Mist Detector Alarm: Actions to be

taken and what to do or not

Oil Mist Detector is equipment which monitors the environment inside a

crankcase space of an internal combustion engine and thus tells the

engineer, in case of formation of any type of explosive vapors occurring in

the crankcase of engine. This is a preventive step avoiding crankcase

explosion taking place. Here is the step by step procedure, to be followed in

case of an alarm.

What Causes Oil Mist Detector Alarm

This piece of equipment is needed to monitor the environment inside the

crankcase. Oil vapors of lube oil are constantly formed inside crankcase and

they possess a hazard of crankcase explosions. So, to avoid that, OMD (Oil

Mist Detector) will keep taking samples of air, from the connected space at

an interval of 1.5 sec to 2 seconds. Then after this it will measure it with the

standard value, plus the values from other units as well. If the

reading is out of limit, alarm comes in.

Measures to be taken After Oil Mist Detector Alarm

Following is the step by step procedure for the same:

1) First thing, first, accept the alarm from the panel.

2) Inform the bridge and chief engineer and side by side initiation of Slow

Down the engine.

3) Press Engineers alarm, to call the required manpower for the same.

4) Check that alarm which has come is true or not. Just reset it and see if it

comes again. Sometimes, false alarms also come in engine room.

5) Next step is to increase the lubrication of the main engine, by starting the

standby lubrication pump.

6) As soon as bridge gives you command for stopping engine, you are ready

to stop it. Bridge can also do that, depending on the situation.

7) Indicator cocks of the units needs to be opened.

8) This will be followed by one man engaging the turning gear and start

turning the engine. This is a counter measure to avoid piston getting stuck.

9) In the mean time, this is happening; other manpower can keep the fire

extinguishers ready. Lubrication should be kept on all the times.

10) As a precautionary measure, make sure that nobody is standing near or

close to the crankcase relief door. As pressure relieve by them can be too

much, which may prove fatal.

11) When the alarm has gone, you can switch off the lube oil pump. With

the back of your hand, feel the crankcase door. If they are cool, then we can

proceed further, otherwise wait for them till the time, they are cooled. You

may also look for any sign of paint color change on the doors.

12) When it is cooled down to normal temperature, open the crankcase door.

Two, three ventilation blower are to be kept for ventilating the crankcase

space.

13) Now it is time to go inside and make few checks. But before that, make

sure that, the light that you are using is flame proof. Also, you boiler suit is

clean and free of any oil. Both the sleeves needs to be rolled down, as there

might be hot surface inside.

14) Check for any sign of local hot spot. Try to see for any sort of metal

particles etc. Rectify the same.

15) Now again start the lube pump and see the flow.

Note: This was all, which you need to do, during an OMD alarm. The

procedure might differ from people to people, as different people have

different approaches. This is just a general approach.

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Marine Engineering Practice Series which deals in questions related to the troubleshooting of the ship machinery etc.

Marine Engineering Practice Series whichdeals in questions related to the troubleshootingof the ship machinery etc.

How will you come to know that EGB is leaking?



Abnormal decrease in Cascade tank water level

White smoke from funnel

Less production of Steam

Exhaust Gas temperature going low.

Rise in the level of soot collecting tank

How to check leakage in lube oil cooler shell and tubetype?

Tube leakage can result from corrosion. This can be checked for, or identified,

by having the shell side of the cooler circulated while the cooling water is shut

off and the end covers removed. Any seepage into the tubes will indicate the

leak. It is also possible to introduce fluorescent dyes into the shell side liquid:

any seepage will show under an ultraviolet light as a bright green glow.

Leaking tubes can be temporarily plugged at each end or removed and

replaced with a new tube.

Main Engine Crankcase inspection and what all checksto be done?

1) After the engine shutdown. Open doors after half hour

2) Start from the bottom. Check for any sign color change of lube oil. Search

for any metal particles etc.

3) Look towards the main bearing and see if any metal paste or particles are

coming.

4) Bottom bearing clearance can be checked here.

5) Then we can take clearance crank bearing.

6) Check for any loose bolts.

7) Check on crank pin for any signs of crack.

8) Check the condition of crosshead guides and their clearances.

9) Piston Rod needs to be checked for any signs of scoring or deep scratches.

10) Run the lubrication pump to see the flow of oil.

Pre bunkering and During Bunkering SafetiesPre bunkering:

1) High level Alarm of all fuel tanks has been checked.

2) Pre Bunker meeting has been carried out.

3) The required amount of SOPEP kit is placed near the bunker manifold.

4) All the deck scuppers have already been checked and plugged.

5) Flag on the Ships is hoisted.

6) Emergency phone numbers are displayed at desired location.

7) Bunker hose is in good condition and properly tightened.

During Bunkering

1) Mooring ropes and distance bunker barge from ship is well maintained.

2) Check on both sides, that no oil is visible on water.

3) Time to time sounding of tanks, manually.

4) At the end of bunkering, blow air from the bunkering hose to clean it.

What Inspections to be carried out in a Dry Dock of aShip?

1) Propeller inspections like cavitations and drop

2) Rudder, hull

3) All the sea outlet valves

4) Condition of Sea chest

5) All the Cathodes condition

6) Condition of Thrusters if any

What is the composition of inert gas in terms of

Percentage?

2-4%of Oxygen

.2-.4% of Sulphur dioxide

12-14%Carbon dioxide

80% Nitrogen

Function of Inducer, impeller, diffuser and volute

casing in Turbocharger

Function of inducer is to have sockless air flow at the entry of turbocharger.

Inducer is to convert the pressure energy into kinetic energy. Volute Casing as

name suggest, the air will come, and will get rotary motion through the

impeller of the blow and will be forced forward towards the diffuser. Diffuser

helps in converting the K.E at the inlet to P.E at inlet.

Reasons for oil coming out from water side in purifierand remedy?

1) Gravity disc problem

2) Sludge bowl not closing problem

3) Incorrect Rpm

4) Too much feed flow to the purifier.

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Oily Water Separator Construction and Working

Oily Water Separator Construction
and Working

Which is very important auxiliary machinery on board ship. Basically, oily

water separator is used in order to treat the bilge waters, so as to avoid any

type of oil getting into the sea with water. It can be considered as waste water

treatment. So let’s see what we have here.

Marpol Annex 1 says that you cannot discharge water with oil content more

than 15 PPM (Parts per million) in open sea. And the reason why they have

made this rule is that, oily water makes a layer above the water surface and

stops the flow of oxygen into the water. This harms the flora and fauna of the

sea and hence dangerous for the marine life. In order to comply with the

standards of Marpol, oily water separator has been installed on board ship to

treat waste water which may contain oil. Generally the bilge of the ship, below

the engine room accounts for maximum waste oil and water, and it is like

storage place for it.

The oil and water come from leaks occurring at various pumps, engine

machinery etc. So, this bilge water has to be drained out timely and this is the

reason oily water separator is installed to take out the oil present in the water.

Only 15 PPM of oil in water is allowed to go and if it does not meet the

conditions, it is again contained back. So let’s study more about this apparatus

in much detail like principal, construction etc.

Construction of Oily water separator

The construction of oily water is simple and there are very less moving parts

in this device. Below diagram shows you the arrangement of the oily water

separator on board ship. As you can see that there are two separate

compartments in this system. First compartment is like accumulator, and it

accumulates the small oil particles. And other compartments are just for

removing these accumulated oil pockets.

There are several probes which are fitted on the oily water separator like oily

water monitoring system, oil level probe etc. Sometimes in order to facilitate

the oil separation, steam line passes through the oily water separator. In the

first compartment baffle plates are installed and these plates serve as the

means for providing the surface for oil getting collected in larger volumes. A

pump from bilge gives supply to the oily water separator.

Working of oily water separator

Working of oily water separator is quite simple and easy to understand. You

just have to see the diagram once and you will be able to understand the

whole working of the oily water separator. The whole process of separation

starts with the pumping of bilge waters from bilges by the bilge pump. The

discharge of this pump goes to the first compartment. Here there are several

baffle plates are arranged and they act as the surface for accumulation of very

small oil droplets to accumulate and make large mass oil.

When the oil droplets gets bigger they have to be removed from the chamber,

and for this a valve is provided on the right hand compartment to remove the

oil content. This oil sent to the waste oil tank and later it is used in the

incinerator for burning.

But in the first compartment oil is only taken out till the 100 PPM content but

our requirements is to drop the oil content in the water to 15 PPM. So, for this

purpose we pass the remaining liquid into the second chamber. In the second

chamber we have a separate mechanism of taking out the remaining oil. These

materials are like oil absorbing or water absorbing. Generally we have an oil

absorbing material. Now as you can see in the fugue that the oil is entering the

second chamber from the bottom. As oil passes upwards to the chamber, oil

particles start getting absorbed and the oil quantity in the water decreases as it

goes upwards. At the outlet we get the oil which has the oil content less than

the 15PPM.

But this water is not thrown directly into the sea. At the outlet line, we have

an oil monitoring device and this device guarantees us with exact PPM which

we want. Actually oil monitoring is set at a level of around 15PPM and it

allows the liquid to go through till it has the oil content less than 15 PPM. Any

amount more than this will leads to bypass action of the signal control valve

and whole discharge will divert back to the first chamber. And an alarm is

also sounded automatically when this condition occurs.

So you can see that this system is a totally automated system and no moving

part is involved in this process. We just take the help of the gravity and

special absorbing material, and our work is done.

Maintenance required on the oily water separator

There are no specific maintenance required on the oily water separator

because the moving parts in this machinery are very less and hence less wear

and tear, but still some maintenance is always required for running

machinery. Following are the checks and maintenance which are carried out

in the oily water separator:

1) Periodic changes of oil absorbing material.

2) Regular cleaning of the surface of the chambers as oil sticks to them.

3) Regular checking and troubleshooting of the oil monitoring system.

4) Regular cleaning of the valves which are used to regulate the flow.

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