Key Points of Marine Oil-Water Separators

Working Principle of Marine Oil-Water Separator

A typical marine oil-water separator system includes oil filtration equipment, a control box, a 15ppm bilge water alarm device, an automatic shutdown device, a recirculation device, related pipelines and valves, etc.

Main components of a marine oil-water separator

01 : Oil Filtration Equipment

The main function of oil filtration equipment is to separate oil from oily wastewater. Based on the separation principle, it can be divided into physical separation, chemical separation, electrolytic separation, and biochemical separation. Currently, the vast majority of marine oil filtration equipment uses gravity separation, which utilizes the density difference between oil and water or physical methods such as polymerization and adsorption to separate oil and water.

02 : 15ppm Bulking Water Alarm Device

The 15ppm bilking water alarm device is used for continuous monitoring of oily water discharge from the bilge of a ship's engine room. It mainly consists of an oil separator and an automatic shut-off device, and has the functions of alarming for exceeding the 15ppm limit and controlling the discharge of oily water. Taking the 15ppm bilking water alarm device that complies with the current MEPC.107(49) resolution as an example, the specific working principle (taking the most commonly used optical turbidimetric method as an example) is to measure the transmitted and scattered light signals of the oily water entering the oil separator using infrared measurement, and then measure the oil content through a high-resolution photoelectric converter and microprocessor data processing. When the oil concentration of the discharged water exceeds the specified value (15ppm), the alarm device triggers an alarm and outputs a control signal to control the oil filter equipment and automatic shut-off device, and monitors the execution status of the automatic shut-off device, returning the excess sewage to the bilge tank.

03 :  Automatic Shutdown Device

When the sampled treated water is monitored by the oil separator and the water sample exceeds the discharge standard, the 15ppm alarm device will sound an alarm. The device will automatically switch the working state of the three-way valve (electric/pneumatic), open the bypass return line valve and close the discharge line valve to cut off the overboard discharge line and guide the treated water exceeding the standard back to the sludge tank (or bilge). Alternatively, the discharge of the sludge exceeding the standard into the overboard can be stopped by shutting down the sludge pump. Both shutdown methods are allowed in MEPC.(60)33 resolution, but MEPC.(107)49 resolution explicitly requires that it can only be controlled by a three-way valve.

04 : Recirculation Unit

For vessels complying with MEPC.107(49) resolution, in addition to oil filtration equipment, a 15ppm bilge water alarm, and an automatic shut-off device, the oil-water separator should also be equipped with a recirculation device on the piping from the automatic shut-off device to the overboard outlet, so that the oil-water separator can be tested with the overboard discharge valve closed. Therefore, according to the resolution requirements, the working principle of the recirculation device is to add a device to the piping from the automatic shut-off device to the overboard outlet, which can meet the normal circulation operation of the equipment during the test with the overboard discharge pipeline closed.

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