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Overview of diesel oil generator protection system
- Sep 25, 2017 -

1. Principle of operation


The main protection element of the oil mist protection system is the oil mist detector, which can detect whether the overheating or piston ring damage caused by excessive leakage and other failures caused by the formation of oil mist in the crankcase to monitor the diesel Main operating parts - crankshaft and cylinder working conditions are normal. During the operation of the diesel engine it is through the sampling line kept out of the crankcase oil and gas, and sent to a sensitive and accurate concentration measurement device. The concentration measuring device comprises an infrared emitting diode and an opposite side of the photoelectric receiving diode. The photodiode senses the intensity of light generated by the infrared ray and converts the light intensity signal into an electrical signal to the electronic identification device. If the crankcase gas contains an oil mist (which increases the opacity of the measuring channel), some of the infrared rays are absorbed in the measuring tube, and the light intensity is weakened, and the electrical signal is weakened. The higher the concentration, the more the electrical signal is weakened. When the electrical signal drops to a minimum value (ie, the oil mist concentration exceeds the maximum limit), the electronic identification device will issue an "oil mist detector high oil mist" alarm and shut down The valve box indicates which part of the fault caused by the high oil mist for inspection by the maintenance personnel.


2. Advantages and disadvantages


The protection of the rapid, sensitive to nothing wrong, but after several years of operation and maintenance found that due to the outside world or the device itself, making its selectivity and reliability greatly reduced. For example, due to the leakage of the lubricating oil cooler (water enters and pollutes the lubricating oil), the oil mist detector will feel an increase in opacity due to an increase in moisture, followed by a trip. Oil mist detector electronic components are high-precision components, but because of its installed in the diesel engine body, high temperature, vibration, the working environment is extremely bad, which makes the aging of electronic components intensified, resulting in temperature drift, jump machine sensitivity increased , The rate of malfunction also increased. And the protection sometimes appears without any indication, so that protection is often out of the state and so on. Frequent protection of the malfunction and protection can not be ready, not only caused by load rejection caused by material fatigue, shorten the life expectancy, and will produce production of paralysis, that the device is unreliable, is a malfunction, so greatly limited and misleading The production staff of thinking, and in the real "high oil mist" when the accident will occur.


3. Common faults and preventive measures


(1)Component aging, temperature drift and other causes of sensitivity changes combined with the actual power plant and the consent of the relevant experts, the alarm threshold S switch to the first four (the original four units are in the first three) , Running so far no jump phenomenon.

(2) electronic board failure When the oil mist detector red and green lights all the phenomenon of extinguishing, and check the 24VDC power supply normal, plug no looseness, the basic can be judged as electronic board failure, you can also use the other units of the electronic Board to judge. If it is really electronic board failure, it should be timely repair or replacement.

(3) crankcase oil and gas contains a lot of water due to the presence of water, making the measurement channel opacity greatly increased, resulting in electronic devices false positives. This requires checking whether the lubricating oil contains moisture, whether the lubricating oil cooler is leaking, whether the air system is excessively wet, and whether the heater in the bottom of the oil mist detector is working properly. In recent years, through the analysis of the high oil fog event found that the real high oil fog jump machine is 0%, high water crash is 98% (and the final inspection, 95% is due to the leakage of the oil cooler Caused by), the remaining failure of 2% (such as electronic board failure, relay malfunction, etc.). So if the oil into the machine on the pipeline to install a set of high sensitivity of the water detection device for the alarm, you can in the water is too high to remind the operator in time to reduce the number of destructive jumpers to increase the stability of the grid Sex.


4. The purpose of the installation of the oil mist detector is to monitor whether the working conditions inside the crankcase itself have changed. Such as piston ring failure (including peeling, abnormal wear, broken) caused by the liner leak to the crankcase, the formation of high oil mist. At this time to check the cylinder and piston ring, damaged to be replaced. Another example is the main bearing or connecting rod bearing high temperature burner caused by local high temperature, resulting in increased oil mist concentration and shutdown, to open the explosion hole hole, carefully check the big end bearing and shaft whether burns, if necessary, replacement. In the case of


5. oil mist detector itself, the type of fault more, these failures will not cause a trip, but it will make the diesel engine to lose important protection. According to the operational experience, as long as the following points, you can reduce the failure rate to a minimum, but also greatly reduce the false jump rate, and after the trip to provide first-hand information.

(1) maintenance personnel should do regular maintenance. Regularly replace the air filter, vacuum air filter, drain the water of the condensing tube, clean the oil tank of the valve box, clean the infrared probe with alcohol, purge the sampling tube with oil, air, and do the necessary alarm test with compressed air And the high oil mist protection action (the easiest way is to smoke a cigarette from the entrance of the sampling tube).

 (2) When the unit is running, the operating personnel should carefully monitor the bearing temperature, lubricating oil temperature and other relevant parameters, and regularly observe the oil mist detector working conditions, oil mist concentration instructions, crankcase U-shaped differential pressure difference, Crankcase ventilation device with or without smoke, crankcase explosion-proof door is hot, crankcase high pressure difference alarm. Such as the occurrence of high oil jump machine should be recorded as soon as possible concentration value, valve box flop situation, crankcase differential pressure difference, bearing temperature and oil mist detectors and other indicators of the indicators.