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Automatic Oil Content Alarm Device
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Task 1. Read and translate the text below.
The standard Bilge Alarm Monitor OCD 1M is designed and type tested in accordance with the IMO rules of MARPOL 73/78, IMO Resolution MEPC 60 (33) as 15 ppm Alarm Device. It is suitable for continuous monitoring of the oil content in water. The alarm device is adjusted according to IMO requirements. The alarm points are set to 15 ppm. If another adjustment is required (e.g. 5ppm or 10 ppm), the adjustment can only be done by the manufacturer.
The monitor utilizes the light scatter principle to determine the content of residual oil in the clear water. It is capable of determining free oil particles (dispersed oil) and oil-in-water emulsions. If the 15 ppm limit is exceeded the automatic control triggers an alarm signal, the 3-way valve is switched over to recirculation mode, after the set time interval has elapsed, to prevent possible outboard oil contamination.
There are two alarm relays in Monitor OCD 1M. They serve as alarm output. In accordance with IMO requirements the alarm point is set to 15ppm and sealed. This control device has two alarms. Alarm 1 is used as signal for the ship’s alarm system. The alarm signal is connected to the automatic control box of the oily water separator, where there are terminals for the ship’s alarm. Alarm 2 is used to control the 3-way diverting valve at the clean water outlet of the oily water separator. If the oil content in the effluent water is exceeding 15 ppm, the 3-way valve will be switched over from “overboard discharge” to “recirculation to bilge or bilge water tank”.
In a low capacity oily water separator the clean water outlet is connected directly to the Monitor OCD 1M, so that the full quantity of purified water is passing through the monitor. In an oily water separator of a capacity from 0.5 to 10 m3/h the sample flow is fed from the clean water discharge pipe into a by-pass to the Monitor OCD 1M. (An orifice plate before the 3-way diverting valve is causing a backpressure in the discharge pipe, so that the necessary sample flow is always guaranteed.) Usually the Monitor OCD 1M requires a sample flow from 0.5 up to 2 ltr / min. The flow can be regulated by the flow adjustment screw in the measurement cell cap of the monitor.
If oily water flows through the Monitor OCD 1M, the status LED (Light Emitting Diode) changes from ORANGE to GREEN. Alarm display LED 1 is activated as soon as the oil content in the effluent water exceeds 15 ppm. 10 minutes later the alarm relays 1 and 2 will be activated.
This will initiate:
- Engine room alarm.
- The 3-way diverting valve will change over to recirculation to bilge or bilge water tank.
The Monitor OCD 1M requires little maintenance to keep it operational. There is a simple standard procedure specified by the manufacturer. Special cleaning equipment is available on request. Regular use of this equipment is intended to prevent monitor failure due to dirt and malfunctions. It is very important to check desiccant regularly to prevent the measuring cell from moisture condensation on the surface of the glass tube. A new desiccant is blue. If the colour is changing to white/pink, the desiccant has to be replaced immediately.
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Task 2. Study the Oily Water Separator Fault Table below. Discuss possible faults and malfunctions, their causes and remedies.
| SIMPTOM | CAUSE | CORRECTIVE MEASURE |
| Continual rapid repetition of the backwashing process | Plant takes in air from an empty bilge. Float switches do not actuate shutdown. | Immediately shut down the plant! Check float switches. |
| Continual repetition of backwashing process, and vacuum gauge indicates a suction height that is too low. | Air enters through leaks in the suction piping or at the OWS (covers, flanges, valves) | Air enters through leaks in the suction piping or at the OWS (covers, flanges, valves) |
| Low flow rate despite low pressure reading of gauge | 1. Suction piping or inlet filter clogged. 2. Valves in suction piping closed. | 1. Check both, and remove obstacles. 2. Open the valves. |
| Plant flushes continuously or unusually slowly | 1. Oil inlet non-return valve not closing. 2. Oil outlet clogged. 3. Backwash water pressure inadequate. | 1. Check; remove and clean if necessary. 2. Check and clean if necessary 3. Check pressure. Min. is 0.5 bar, max. 1 bar. |
| Plant detects oil but discharges water | 1. Wiring from control box to electrode damaged 2. Electrode clogged | 1. Check and correct if necessary. 2. Clean contact surfaces. |
| Plant detects oil but does not discharge | 1. Oil outlet to collecting tank blocked 2. Backwash water supply interrupted 3. Piston valve does not work | 1. Check piping to collecting tank and clean if necessary 2. Check water supply. Check piston valve. 3. Check connection voltage in control box; the voltage between the contacts must be 24 V. If not, replace the circuit board. |
| Plant does not flush | 1. Backwash water outlet to bilge blocked 2. Piston valves don’t work | 1. Remove obstacles. 2. Check connection voltage in control box; the voltage between the contacts must be 24 V. If not, replace the circuit board. |
| Plant does not detect oil | 1. Failure in the wiring between sensor electrodes and circuit board 2. Circuit board defective 3. Possible formation of oil-water emulsion 4. Oil binds water | 1. Check wiring. 2. Check circuit board by removing the plug from the electrode; if no oil is indicated, replace the board. 3. Avoid emulsions. Contact Manufacturer’s Service department. 4. Contact Service dept. |
Make yourself familiar with an example of a certificate of type approval for an oil content meter.
Text 3
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