oil pollution prevention equipment

8/13/2019 Oil Pollution Prevention Equipment

1/13

Subject : Marine Pollution and Prevention

Topic : Oil Pollution Prevention Equipment

ILOs : At the end of the session, the students

should be able to :

1. Describe the function and operation of ships oily water separator or OWS.

2. Describe the function and operation of ships oildischarge monitoring and control systems orODMCS .


2/13

IntroductionMarpol regulations regarding discharge of oil in sea water are becoming stringent dayby day. For this purpose Oily water seperators have become compulsory on all types

of ships. OWS is used to treat the oil-water mixture from bilge spaces (read aboutbilge water here), oil tanks or any compartment in the ship which has accumulatedwater, before discharging it to the sea. According to Annex I of Marpol, water thathas to be discharged should contain less than 15 parts per million of oil. OWS is usedto attain this.

Almost all OWS use gravity system for the separation of water from oil. This methodallows the system to bring down the PPM (parts per million) number to 100, whichis not enough. For this purpose, all OWS are equipped with a filtration system tobring down the PPM level. The PPM is measured with an instrument which is similarin working to the Salinometer used to check salt ppm.


3/13

Construction and working- The separator unit

The Separator unit itself consists of two parts. The first part consists of a coarse

separating compartment with an inlet for the oil-water mixture. The oily watermixture enters the compartment through the inlet pipe . Some of the oil moleculesdue to their lower density will separate and rise to the top of the mixture into an oilcollecting compartment.


4/13

The remaining oil leaves the compartment, from an outlet provided at the bottom ofthe chamber to the second part which is a fine separating compartment. Thiscompartment has stationary catch plates arrangement fixed at the center of thecompartment as shown in the figure. The oil mixture flows slowly between the catch

plates. The oil from the mixture will stick to the underside of the catch plates andslowly move outwards to rise at the top of the mixture and gets collected in an oilcollecting space.The clean water which has PPM of around 100, flushes out of the compartmentthrough a pipe attached at the center of the compartment. All the oil collectingcompartments are provided with heating coils or a steam inlets for heating the oil to

facilitate a free flow. The air produced is released through a vent provided at the topof the compartment. The mixture is then passed to the filteration unit.


5/13

Construction and working - The filtrating unitThe water that comes out of the separating unit generally has a PPM level of 100 or

less. To reduce the PPM level, it is passed to the filtrating unit. The filtrating unit alsoconsists of two stages.


6/13

When the water enters the first stage, solid particles and physical impurities areremoved with the help of filter units. These impurities settle at the bottom of thecompartment and are removed later. The water then passes through the second

stage for complete removal of oil. The second stage uses coalescer inserts toachieve this. Coaslescer induces coalescence process between the oil particles. Dueto this process the surface tension between the oil molecules in the mixture breaksdown which makes them to stick together to form larger molecules. This large oilmolecules then rise to the top of the mixture to get collected in the collectingchamber.

The collecting chamber is emptied as and when require. The filter units are to bechanged generally once a week. The OSW system is fixed with a PPM monitoringdevice which keeps a continuous check on the discharged water's PPM level. Thesystem raises an alarm, in case the PPM level goes above 15 .


7/13


8/13

What is Oil Discharge Monitoring and Control System (ODMCS) on Ships?

Oil tankers carry different types of oil cargo in their cargo tanks and it often

happens that after discharging the oil cargo in some port, the ship sails without anycargo to some other destination. In order to do so, it has to take ballast from thesea to get better draught and stability.

For this reason, ballast water is taken into cargo tanks wherein generally oil cargowould have been carried. It is to note that the ballast water carried in cargo tanks has to be discharged out at sea before the next cargo loading. Therefore, OilDischarge monitoring and control system (ODMCS) is used to prevent thepollution of ocean by oil due to the discharge from ballast and bilge spaces.As per MARPOL 73/78 Annex I, all the oil tankers of 150 GT and above must havean approved Oil Discharge Monitoring System. The system must have provision towork in manual operating mode if the auto system is not working.
http://marineinsight.com/marine/what-is-ballast-and-de-ballasting/http://marineinsight.com/marine/list-of-important-and-not-so-famous-tanks-on-a-ship/http://marineinsight.com/knowledge/safety-of-life-at-sea-solas-convention-for-prevention-of-marine-pollution-marpol-a-general-overview/http://marineinsight.com/knowledge/safety-of-life-at-sea-solas-convention-for-prevention-of-marine-pollution-marpol-a-general-overview/http://marineinsight.com/marine/list-of-important-and-not-so-famous-tanks-on-a-ship/http://marineinsight.com/marine/list-of-important-and-not-so-famous-tanks-on-a-ship/http://marineinsight.com/marine/what-is-ballast-and-de-ballasting/


9/13

Main Parts of ODMCS An ODMCS consists essentially of four systems:1. An Oil content mete r: The oil content meter is used to analyze the content of oilin the water that is to be discharged overboard. This oil is expressed in parts permillion (PPM).2. A flow meter : The flow rate of the oily water to be discharged is measured at thedischarge pipe.3. A computing unit : A computing unit calculates the oil discharge in litres/nauticalmiles and the total quantity, along with date and time identification.4. An overboard valve control system : The auto control valve is installed at theoverboard so that it must close and stop the discharge when permissible limit hasbeen reached.


10/13


11/13

Working The oily mixture is pumped out to the sea through ODMCS by a pump .A sampler probe and a flow meter sensor is connected at the dischargepipe, before the overboard valve, to sense the oil content and the flowof mixture.The data provided by the two sensors are fed in a control unit whereinit is analysed and the discharge valve is controlled by the same.

Regulatory requirements for oil mixture discharge from cargo space Tanker vessel must be enroute The vessel should not be in special areas .The tanker must be 50 nautical miles away from land.The instantaneous rate of discharge of oil content does not exceed 30 litresper nautical mile .

The total quantity of discharge must not exceed 1/30000 of the total quantityof the residue formed cargo.

The tanker must have operational and approved ODMCS.
http://marineinsight.com/knowledge/general-overview-of-types-of-pumps-on-ship/http://marineinsight.com/knowledge/general-overview-of-types-of-pumps-on-ship/


12/13

As per the regulation, the following inputs must be recorded by the system :Discharge rate of the pump which is discharging the oily water mixture overboard.The location of the ship in latitude and longitude.Date and time of the discharge.The total quantity that has been discharge overboard.Oil content of the discharged mixture in PPM.All the records of ODMCS must be stored on board ships for not less than 3 years .


13/13

The oil/water/sludge mixture enters the oil water separator The heavier sludge and particulates fall out of the fluid and are captured in thesludge hopperThe oil and water mixture with lighter particulates travels up the inclined platesThe inclined plates start to separate the mixture. Some oil rises to the top of theseparator and the remainder of the particulates slide back down to the sludgehopper.The remaining oil and water mixture then moves through the coalescing mediapacks where the majority of the smaller oil particles attach to the media andcombine together to form larger oil particles.These larger oil particles become so buoyant that they release from the media andtravel to the top of the separator.As the oil volume in the separator reaches a certain level, the oil is drained tothrough piping to an oil storage tank.The clean water continues over the weir to the clean water chamber where it goesthrough a final polishing pack and out to the sewer.
http://www.washbaysolutions.com/oil-water-separators.phphttp://www.washbaysolutions.com/oil-water-separators.php

oil pollution prevention equipment

Documents