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Oil in Water Monitoring System for Merchant Ships

Current regulations with respect to the discharge of oily water from ships set limits of concentration 15 parts per million. A monitor is required in order to measure these values and provide both continuous records and an alarm where the permitted level is exceeded.

The principle used is that of ultra-violet fluorescence. This is the emission of light by a molecule that has absorbed light. During the short interval between absorption and emission, energy is lost and light of a longer wavelength is emitted. Oil fluoresces more readily than water and this provides the means for its detection.

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A sample is drawn off from the overboard discharge and passes through a sample cell . An ultra-violet light is directed at the sample and the fluorescence is monitored by a photoelectric cell. The measured value is compared with the maximum desired value in the controller/recorder.

Where an excessive level of contamination is detected an alarm is sounded and diverting valves are operated. The discharging liquid is then passed to a slop tank.


Oil in water monitoring system
Fig : Oil in water monitoring system


The oil is automatically bled from the evaporator to a heat exchanger in which liquid refrigerant mixed with the oil is vaporized. The heat for vaporizing the refrigerant is obtained by passing warm liquid refrigerant from the condenser, through the heat exchanger. Vapour and oil are passed to the compressor where the oil returns to the sump while the freon passes to the compressor suction. The regulator is a thermostatically controlled valve which operates in the



Ships instruments:

  1. Oxygen analyser working principle
    The measuring of oxygen content in an atmosphere is important, particularly when entering enclosed spaces. Also inert gas systems use exhaust gases which must be monitored to ensure that their oxygen content is below 5%. One type of instrument used to measure oxygen content utilises the fact that oxygen is attracted by a magnetic field, that is, it is paramagnetic....

  2. Temperature measurement instruments - use of Thermometers, Thermocouple, Radiation pyrometer & Thermistor

    Temperature measurement by instruments will give a value in degrees Celsius (°C). This scale of measurement is normally used for all readings and temperature values required except when dealing with theoretical calculations involving the gas laws, when absolute values are required.....

  3. Pressure measurement instruments - U-tube Manometer, Mercury Barometer & Aneroid Barometer
    Various liquids are used in this type of instrument, depending upon the temperature range, e.g. mercury -35 deg C to +350 deg C, alcohol -80 degC to 4-70°C. An increase in temperature causes the liquid to rise up the narrow glass stem and the reading is taken from a scale on the glass . High-temperature-measuring mercury liquid thermometers will have the space above the mercury filled with nitrogen under pressure.....

  4. Level measurement by Pneumatic gauge
    This is a device which uses a mercury manometer in conjunction with a hemispherical bell and piping to measure tank level. The arrangement is shown in Figure. A hemispherical bell is fitted near the bottom of the tank and connected by small bore piping to the mercury manometer. A selector cock enables one manometer to be connected to a number of tanks, usually a pair....

  5. Salinometer -How to determine water purity ?
    Water purity, in terms of the absence of salts, is essential where it is to be used as boiler feed. Pure water has a high resistance to the flow of electricity whereas salt water has a high electrical conductivity. A measure of conductivity, in Siemens, is a measure of purity.....

  6. Oil in water monitor
    Current regulations with respect to the discharge of oily water from ships set limits of concentration 15 parts per million. A monitor is required in order to measure these values and provide both continuous records and an alarm where the permitted level is exceeded.....

  7. Viscosity control of marine fuels
    Viscosity control of fuels is essential if correct atomisation and combustion is to take place. Increasing the temperature of a fuel will reduce its viscosity, and vice-versa. As a result of the varying properties of marine fuels, often within one tank, actual viscosity must be continuously measured and then corrected by temperature adjustment. ....

  8. Flow measurement
    Flow measurement can be quantity measurement, where the amount of liquid which has passed in a particular time is given, or a flow velocity which, when multiplied by the pipe area, will give a rate of flow.....

  9. Moving coil meter
    Electrical measurements of current or voltage are usually made by a moving coil meter. The meter construction is the same for each but its arrangement in the circuit is different.....

  10. Electrical and mechanical Tachometers
    A number of speed measuring devices are in use utilising either mechanical or electrical principles in their operation.....

  11. The measurement of torsion -Torsionmeters
    The measurement of torsion is usually made by electrical means. The twisting or torsion of a rotating shaft can be measured in a number of different ways to give a value of applied torque. Shaft power can then be calculated by multiplying the torque by the rotational speed of the shaft....

  12. Viscosity control of marine fuels
    Viscosity control of fuels is essential if correct atomisation and combustion is to take place. Increasing the temperature of a fuel will reduce its viscosity, and vice-versa. As a result of the varying properties of marine fuels, often within one tank, actual viscosity must be continuously measured and then corrected by temperature adjustment.....



Related Info:

  1. Compressed Air Systems for various shipboard operations
    2. The main aim of a compressor, as the name suggests, is to compress air or any fluid in order to reduce its volume. Some of the main applications of compressors onboard ships are main air compressor, deck air compressor, AC compressor and refrigeration compressor. Failure to start or control air compressor can be inconvenient, costly and can carry risks, which need to be managed.....

  2. Marine air compressors working principles
    3. Control or instrument air supplies have particular requirements with regard to being moisture and oil free and without impurities. A special type of oil-free compressor may be used to supply control air or it may be treated after delivery from an ordinary air compressor. This treatment results in the air being filtered and dried in order to remove virtually all traces of oil, moisture and any atmospheric impurities.....

  3. Coolers at sea- Shell and tube type coolers and plate type coolers
    4. Heat exchangers on board ship are mainly coolers where a hot liquid is cooled by sea water. There are some instances where liquid heating is required, such as heavy fuel oil heaters and sea water heaters for tank cleaning. Although being heat exchangers, the main condenser for a steam ship and the evaporator/distiller are dealt with separately .....

  4. Distillation system- Production of distilled water for ships use - The evaporation process
    5. Distillation is the production of pure water from sea water by evaporation and re-condensing. Distilled water is produced as a result of evaporating sea water either by a boiling or a flash process. This evaporation enables the reduction of the 32000 parts per million of dissolved solids in sea water down to the one or two present in distilled water. The machine used is called an 'evaporator', although the word 'distiller' is also used.....

  5. Oily water separator and filter unit for 15 parts per million purity
    6. Oil/water separators are used to ensure that ships do not discharge oil when pumping out bilges, oil tanks or any oil-contaminated space. International legislation relating to oil pollution is becoming more and more stringent in the limits set for oil discharge.....

  6. Sewage treatment on board- biological and chemical sewage treatment plant
    7. The discharge of untreated sewage in controlled or territorial waters is usually banned by legislation. International legislation is in force to cover any sewage discharges within specified distances from land. As a result, and in order to meet certain standards all new ships have sewage treatment plants installed.....

  7. Incinerator for ships
    8. Stricter legislation with regard to pollution of the sea, limits and, in some instances, completely bans the discharge of untreated waste water, sewage, waste oil and sludge. The ultimate situation of no discharge can be achieved by the use of a suitable incinerator. When used in conjunction with a sewage plant and with facilities for burning oil sludges, the incinerator forms a complete waste disposal package.....

Marine machineries - Useful tags

Marine diesel engines ||Steam generating plant ||Air conditioning system ||Compressed air ||Marine batteries ||Cargo refrigeration ||Centrifugal pump ||Various coolers ||Emergency power supply ||Exhaust gas heat exchangers ||Feed system ||Feed extraction pump || Flow measurement || Four stroke engines || Fuel injector || Fuel oil system || Fuel oil treatment ||Gearboxes || Governor || Marine incinerator || Lub oil filters || MAN B&W engine || Marine condensers || Oily water separator || Overspeed protection devices || Piston & piston rings || Crankshaft deflection || Marine pumps || Various refrigerants || Sewage treatment plant || Propellers || Power Plants || Starting air system || Steam turbines || Steering gear || Sulzer engine || Turbine gearing || Turbochargers || Two stroke engines || UMS operations || Drydocking & major repairs || Critical machinery || Deck machineries & cargo gears || Control and instrumentation ||Fire protection ||Engine room safety ||





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