Every engineer on ship knows the importance of oily water separator (OWS) and must have heard stories of legal actions taken against seafarers who tried to fiddle or bypass the automation system of the OWS. The most common cause of people tempering with oily water separator is deterioration of performance of the system.
Apart from the filter getting clogged due to continuous usage, there can be many other reasons for the lack of performance. A few critical points, which are often ignored and less commonly known to engineers operating oily water separator on daily basis, are discussed in this article to ensure efficient performance of oily water separator (coalesce filter type) used onboard ships:
- Oil In Bilge: The separator is suitable for separating small quantity of oil in bilge and not the other way round. If there is a mixture consisting of small quantity of water in oil, better not to pass it though the OWS and directly transfer it to waste oil tank for sludge disposal to shore or for incineration.
- Keep Viscosity in Limit: Highly viscous oil if supplied for oily water separation will clog the filter. It is important to keep the viscosity of the oil within 1000 mm2/s
- Discharge Outside Separator: Never discharge or drain water oil mixture from the separator abruptly out of OWS as it will lead to the separated oil adhere to coalescers, making it inoperative. Ensure to discharge the collected separated oil outside the separator and clean the internals of the OWS by supplying water.
- Install Dust Filter: While using OWS for discharging bilge mixture containing dust and sand (a coarse grained entity), it will be difficult for the coalescer filter to pass dust and sand due to their sizes. This will reduce the operating hours of the filter and in-turn the efficiency of the OWS. The ideal service life of the filter normally ranges from 1-2 year depending upon the manufacturing process, considering daily operation of one hour. It is advisable to install a dust filter in the inlet line of the OWS to avoid this trouble.
- Exchanging Probe for Fault Finding: for In most of the 15ppm OWS models, the oil level detecting probe and transmitting convertor in the 1st and 2nd stage chamber are identical. In the event of trouble, exchange these with each other, between the chambers, as this will help in finding out the source of trouble quickly.
- Keep Check On Heating Device: If a heating device is provided, ensure it is ON when OWS is in operation and switched OFF before OWS is stopped. In case when the OWS is run for a long time, keep a track on the heater for overheating of coils. If the separator is overheated to high extent, there may be some production of inflammable gases inside.
- Protect Internal Coating: The OWS internals are applied with tar epoxy coating, which is inflammable. Avoid bringing fire near to it or perform welding over the surface or body as the heat generated will damage the coating, making OWS susceptible to corrosion
- Check Water Level: Ensure that the separator is initially filled with sea water before bilge mixture is supplied to it. This is to increase the life of filters and also to maintain the operational efficiency of the separator
- Prevent Leakage: Ensure the means provided to avoid leaking or flowing out of water due to siphon effect. Failure to do so will allow oil to flow in the secondary chamber highly affecting the treatment capability of the machine and clogging the 2nd stage filters
- Check Effluent: Frequent checks on effluent to be done to assess the performance of the separator. If the effluent is found contaminated, immediately stop the separator and take preventive actions
The operator of OWS should be thorough about the system, design, piping arrangement and of course the operating procedure of oily water separator. Out of all the machinery systems, OWS is kept at high priority due to stringent rules and regulations attached to it for ensuring environmental compliance. Hence it is important for the ship staff to maintain this machine in best of its shape.