The oil-water separator is an important equipment for ship pollution prevention measures. Many people are not very thorough about the composition and working principle of the oil-water separator, especially for many small coastal ships. The outlet of the oil-water separator has been sealed with lead, and many colleagues feel that it is not necessary to have a detailed understanding of the equipment that is not used. However, in reality, the maritime department will still board the ship to inspect the relevant equipment and test results, and if not done well, points will be deducted and punished. Therefore, the following elementary school students will organize the relevant knowledge and inspection points of the oil-water separator for everyone, hoping to be helpful to friends.
Introduction to oil-water separator
An Oil Water Seperator is an anti pollution equipment that separates the bilge water (oil-water mixture) in the machinery compartment, ensuring that the oil content of the discharged bilge water into the sea is less than 15ppm.
The ship's oil-water separator system generally includes oil filtration equipment, control box, 15ppm bilge water alarm device, automatic shutdown device, recirculation device, related pipelines and valves, etc,
Main workflow
When the separator is in operation, the sewage pump sucks the treated drainage at the discharge port of the separation device, causing a vacuum to be generated inside the separation cylinder. The bilge water, under the action of the internal and external pressure difference, enters the diffusion nozzle inside the separator through the suction check valve, the inlet filter, and the three-way valve through the gas closed channel. Preliminary oil-water separation is carried out, and the separated large oil droplets float at the top. The sewage containing small particle oil droplets flows downward from the annular chamber into the first stage oil collector (stacked with multiple layers of conical corrugated plates). The first coalescence separation is carried out inside, and the larger oil droplets formed by coalescence float upward to the top oil collection chamber. The sewage continues to flow down from the central channel and enter the second stage oil collector, outward chamber. The large oil droplets that flow and coalesce stop at the top of the annular chamber. Water that meets the discharge standards is discharged downwards through the bottom of the separator and flows to the air shut-off channel of the external three-way valve. It enters the single screw pump and flows out of the pump before passing through the air shut-off channel of the three-way valve and being discharged outward.
If the treated sewage does not meet the discharge standards, the oil content alarm recorder will send an alarm signal, the three ventilation (electric) valve will act, and the sewage will flow back into the sewage tank. The resistance type oil level detector uses the different conductivity of oil and water to detect the oil level. When a high oil level is detected, it controls the oil discharge pneumatic (electric) valve to open the oil discharge channel, achieving automatic oil discharge function. Simultaneously equipped with manual oil discharge control.
Composition of oil-water separator
1,Oil filtration equipment
The main function of oil filtration equipment is to separate oil from oily wastewater. According to the separation principle, it can be divided into physical separation, chemical separation, electrolytic separation, and biochemical separation. At present, the vast majority of marine oil filtration equipment uses gravity separation method, which utilizes physical methods such as density difference between oil and water or polymerization and adsorption to separate oil and water. It is the main device that runs the equipment.
Specifically, the sewage pump injects the bilge oily water into the first separation chamber of the separation cylinder for coarse separation. After coarse separation through the first separation chamber, the oily water also contains small oil particles. The small oil particles can be coarsened to nearly 100% through the condenser installed in the secondary separation chamber, allowing them to separate and float on the water surface. After secondary treatment, no more than 15ppm of sewage will be discharged overboard.
2,15PPM alarm device
The function of the 15ppm bilge water alarm device is to continuously record the oil concentration in the water treated by the oil-water separator. When the oil content in the treated water exceeds the discharge standard (15ppm), the device will automatically shut down through sound and light alarms and actions, and the unqualified treated water will be automatically discharged back to the bilge through the opening and closing of the three-way solenoid valve. At present, the vast majority of marine oil meters use the optical turbidity method, which measures the oil concentration by using the intensity of direct and scattered light as the oil concentration changes after the measurement beam passes through the turbidity liquid of the oil wastewater emulsion.
3,Automatic shutdown device
When the sampled treated water is monitored by the oil content meter and the water sample exceeds the discharge standard, a 15ppm alarm device will sound. By automatically switching the working status of the three-way valve (electric/pneumatic), opening the bypass reflux pipeline valve and closing the discharge pipeline valve, the overboard discharge pipeline will be cut off, and the excess treated water will be directed back to the dirty oil water tank (or bilge). Alternatively, by shutting down the sewage pump, the discharge of excess oil and sewage to the ship's hull can be stopped.
For ships that comply with MEPC.60 (33) resolution, the automatic shutdown device can either shut down the sewage pump or open/close the three-way solenoid valve to stop the overboard discharge. However, for ships that comply with MEPC.107 (49) resolution, this automatic shutdown function can only be achieved by opening and closing a three-way solenoid valve or setting up two separate solenoid valves (one on each of the offshore and return pipelines).
4. Recirculation device
For ships that comply with MEPC.107 (49) resolution, in addition to oil filtration equipment, a 15ppm bilge water alarm device, and an automatic shutdown device, the oil-water separator should also be equipped with a recirculation device on the piping system from the automatic shutdown device to the overboard outlet, so that the oil-water separator can be tested with the discharge valve to the overboard closed. Currently, ships generally adopt the method of installing manual two position three-way valves or installing one valve on each of the two pipelines to achieve this.
Statutory specifications for oil-water separators
(1)Unless otherwise exempted by the competent authority, motor vessels with a total tonnage of 400 tons or more but less than 10000 tons shall be equipped with oil filtration equipment that ensures that the oil content of the oily mixture discharged into the sea through the system does not exceed 15ppm.
(2)Motor vessels with a total tonnage of 10000 tons or more shall be equipped with approved oil filtration equipment and devices that can sound an alarm and automatically stop the discharge of oil when the oil content in the discharged material exceeds 15ppm.
(3)According to the requirements of Annex I of the MARPOL Convention, MEPC Resolution, and domestic conventions, the oil-water separator should meet the following recognized standards according to different keel installation dates or device loading dates.
① International navigation vessels laying keel on or after January 1, 2005 (for sea 06 repairs, domestic navigation vessels on or after March 1, 2007) must comply with MEPC.107 (49) resolution as required;
② For ships with keel laid on or after April 30, 1994, it is necessary to comply with the requirements of Resolution MEPC.60 (33) "Guidelines and Technical Conditions for Anti Pollution Equipment in Ship Engine Room Bilge Water". Ships before April 30, 1994 shall comply with Resolution A.393 (x) of the International Maritime Organization.
MEPC60 (33) Resolution Performance Requirements:
(1) The reaction time of the oil content meter has been limited, requiring that the time required for the sample supplied to the oil content meter to display the correct reaction should not exceed 20 seconds.
(2) For the response time required for the automatic shutdown device, it is required that the total reaction time from changing the mixture pumped out to changing the oil level gauge reading should not exceed 40 seconds.
(3) For the sampling position of the oil filtration equipment, it is required to set the sampling point as close as possible to the vertical part of the discharge water near the outlet of the oil-water separator.
(4) For the displacement of the sewage pump, it is required that the rated capacity of the pump cannot exceed 1.5 times the maximum processing capacity of the oil-water separator.
MEPC.107 (49) Resolution Performance Requirements
(1) The automatic shutdown device is required to be a valve device installed at the outlet line of the 15PPM bilge water separator. When the oil content of the effluent exceeds 15ppm, it will automatically lead the mixed effluent discharged to the ship's bilge or sewage tank.
(2) The reaction time of the oil content meter has been limited, requiring that the time required for the sample supplied to the oil content meter to display the correct reaction should not exceed 5 seconds.
(3) The 15ppm bilge water alarm device should record the date, time, and alarm status, as well as the operating status of the 15ppm bilge water separator. The data storage time should be at least 18 months, and its accuracy should be tested (implemented by the manufacturer) when replacing the ship's oil pollution certificate, and there should be a calibration certificate.
(4) The structure of the 15ppm bilge water alarm device should activate the alarm whenever clean water is used for cleaning work or to restore zero position.
(5) Recirculation equipment should be installed behind and near the overboard outlet of the shutdown device, so that the 15ppm bilge water separation system, including the 15ppm bilge water alarm device and automatic shutdown device, can be tested under the condition of overboard discharge shutdown.
(6) For the response time required for the automatic shutdown device, it is required that the total reaction time from changing the mixture pumped out to changing the oil level gauge reading should not exceed 20 seconds.
(7) For the displacement of sewage pumps, it is required that the rated capacity of the pump cannot exceed 1.1 times the maximum processing capacity of the oil-water separator. The specifications of the pump and motor should be recorded on the type approval certificate.
The performance standards that oil-water separators installed in different years in China should meet and the differences in key technical conditions caused by different performance standards
(1) Oil filtration equipment and oil separation meters loaded onto ships before March 1, 2007 should comply with Resolution A.393 (X) or Resolution MEPC.60 (33) [the Technical Rules for Statutory Inspection of Non International Navigation Seagoing Ships (1999)], which were first specified to be referred to];
(2) The oil filtration equipment and oil content meter loaded onto ships on or after March 1, 2007 shall comply with Resolution MEPC.107 (49) of the Technical Regulations for Statutory Inspection of Domestic Seagoing Ships (Revised in 2006);
