武汉理工大学：《船舶辅机》课程教学资源（PPT课件，英文版）6.6 Coalescing bed-type oily water separators

6.6 Coalescing bed-type oily water separators

6.6 Coalescing bed-type oily water separators

6.6 Coalescing bed-type oily water separators The coalesce is capable of forming oil globules up to 12 mm diameter and the heavier fuel oils usually form long 'stalagmites' which grow to a considerable size before they are released Because of the low velocities employed the collected oil can flow past the water screen without becoming re-entrained and carried through into the outlet

6.6 Coalescing bed-type oily water separators • The coalesce is capable of forming oil globules up to l2 mm diameter and the heavier fuel oils usually form long 'stalagmites' which grow to a considerable size before they are released. Because of the 1ow velocities employed the collected oil can flow past the water screen without becoming re-entrained and carried through into the outlet

6.6 Coalescing bed-type oily water separators The separators can be arranged for manual or automatic operation. Four test corks are fitted, two to each zone with the internal pipes arranged so that the high and low levels of oil can be monitored When oil reaches the high oil level test cock a manual discharge valve on the collection zone being monitored is opened to allow the oil to discharge to the oil collection tank. The low oil level test cock is then opened and when water appears the oil discharge valve is closed The separator pressure valve is maintained at l bar either by having a high level overboard discharge or a spring loaded or manual discharge val ve in the clean water outlet

6.6 Coalescing bed-type oily water separators • The separators can be arranged for manual or automatic operation. Four test corks are fitted, two to each zone with the internal pipes arranged so that the high and low levels of oil can be monitored. • When oil reaches the high oil level test cock a manual discharge valve on the collection zone being monitored is opened to allow the oil to discharge to the oil collection tank. The low oil level test cock is then opened and when water appears the oil discharge valve is closed. • The separator pressure valve is maintained at 1 bar either by having a high level overboard discharge or a spring loaded or manual discharge valve in the clean water outlet

6.6 Coalescing bed-type oily water separators It is advisable to fit a high capacity basket strainer with a 20 mesh screen between the oily water pump and the separator to prevent dirt and debris from fouling the underside of the coalescing bed With a suitable strainer the bed will operate almost indefinitely without servicing and does not normally require cleaning by back flushing or renewal but without adequate filtration the bed is liable to become partiall blocked resulting in a fall-off of effluent quality and a significant rise in back-pressure. In the event of this occurring the bed should be backwashed

6.6 Coalescing bed-type oily water separators • It is advisable to fit a high capacity basket strainer with a 20 mesh screen between the oily water pump and the separator to prevent dirt and debris from fouling the underside of the coalescing bed. • With a suitable strainer the bed will operate almost indefinitely without servicing and does not normally require cleaning by back flushing or renewal but without adequate filtration the bed is liable to become partially blocked resulting in a fall-off of effluent quality and a significant rise in back-pressure. In the event of this occurring the bed should be backwashed

6.6 Coalescing bed-type oily water separators This can be done by opening the drain val ve in the bottom of the unit and allowing the contents to run to the bilge e. For satisfactory operation it is essential that the bed is well charged with oil at all times; new separators are supplied with the bed already charged. When operating the separator for the first time it should be filled with clean water before use

6.6 Coalescing bed-type oily water separators • This can be done by opening the drain valve in the bottom of the unit and allowing the contents to run to the bilge. • For satisfactory operation it is essential that the bed is well charged with oil at all times; new separators are supplied with the bed already charged. When operating the separator for the first time it should be filled with clean water before use

6.6 Coalescing bed-type oily water separators The separator is designed so that it is only necessary to lift the top section 75 mm to gain access to the interior and for full examination, the top half can be moved sideways. This facility enables the separator to be installed between the decks where the headroom is low Steam coils or electric heaters may be fitted to reduce the specific gravity of the oil to aid collection and discharge. Drain and steaming out connections are provided so that the separator can be drained and steamed out before opening up for survey

6.6 Coalescing bed-type oily water separators • The separator is designed so that it is only necessary to lift the top section 75 mm to gain access to the interior and for full examination, the top half can be moved sideways. This facility enables the separator to be installed between the decks where the headroom is low. • Steam coils or electric heaters may be fitted to reduce the specific gravity of the oil to aid collection and discharge. Drain and steaming out connections are provided so that the separator can be drained and steamed out before opening up for survey

6.6 Coalescing bed-type oily water separators This design of separator produces an effluent quality of better than 20 mg/litre. Figures of 15 mg/litre with 25% oil concentration and 6 mg/litre with 5%0 oil concentration have been recorded during tests on board ship When fitted with a clean water discharge valve which closes when the oil discharge valves are open, the separator can function adequately when handling 100% oil as for instance when the bilge water has been stripped off and only the oil is left

6.6 Coalescing bed-type oily water separators • This design of separator produces an effluent quality of better than 20 mg/litre. Figures of 15 mg/litre with 25% oil concentration and 6 mg/litre with 5% oil concentration have been recorded during tests on board ship. • When fitted with a clean water discharge valve which closes when the oil discharge valves are open, the separator can function adequately when handling 100% oil as for instance when the bilge water has been stripped off and only the oil is left

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