Analysis of emulsification failure of lubricating oil in a main air compressor

1 Analysis of the cause of oil emulsification Emulsification means that the two liquids are thoroughly mixed into an emulsion. Oil and water are not emulsified; however, if some amphiphilic substances are adsorbed and concentrated at the oil-water interface, it is possible to change the interface state (reducing the interfacial tension) and increase its surface activity. Many particles are dispersed in another liquid, resulting in emulsification. These substances which increase the surface activity of two liquids and emulsify them are called emulsifiers.

There are many types of emulsifiers which can cause oil and water emulsification, and the amount of emulsifier required to emulsify oil and water is small. It is difficult to determine the composition of the emulsifier and can only be analyzed from the source of moisture which causes emulsification of the oil.

According to the structure of the air compressor, there may be two sources of water in the lubricating oil. One is the leakage of the cooling water of the cylinder liner, and the other is the condensation of air in the crankcase.

After repeated inspection of the oil pan, the cylinder seal seal is not found and the cylinder liner crack leaks, and the liner cooling water leakage can be excluded.

Air condensate in the air compressor casing - set: summer sea surface air pressure 0MPa (same standard atmospheric pressure, the following pressure is table pressure), summer sea surface relative humidity p = 60% (typically higher than 60%), summer The average air temperature in the cabin is f = 30 (the average temperature in the cabin in summer is generally higher than 30). From (the entropy map of the humid air under standard atmospheric pressure), it can be seen that the relative humidity of the condensed water is 100% from the relative humidity of the air of 60% and the average air temperature of the summer cabin (30 points (corresponding to the "A" point in the figure). In the "B" point), it is a vertical line with constant air moisture content, and the atmospheric dew point temperature td corresponding to point B is 22; according to the pressure dew point and atmospheric dew point conversion map (see), the atmosphere is wet and the most d Analysis of emulsification failure of wheel main air compressor oil Huang Wenlong 1 Wang Lianhai 2 (1. Beihai Rescue Bureau of the Ministry of Communications; 2. School of Maritime Transportation, Shandong Jiaotong University) The pressure corresponding to the slanting line of the air enthalpy diagram under standard atmospheric pressure is 0, 0.1, 0.3 respectively. , 0.5, 0.7, 丨. 0, 丨. 7. 2.0MPa pressure dew point and atmospheric dew point and atmospheric dew point conversion map Analysis of a certain round of main air compressor oil emulsification failure - Huang Wenlong Wang Lianhai. 47 Analysis of a heavy oil oil separator drain running oil failure Shanghai Ocean Shipping Co., Ltd. Wu Wenfa Wang Xiangwei 1700-1800r/min, rated oil content 21500L / h, control unit EPC-41, gas control constant flow regulation system (MCFR) adjustment The fuel flow rate of the fuel separator is kept constant (the actual oil consumption is about 3400L/h), and the fuel supply pump is a positive displacement screw pump. It was delivered in 1990.

As is well known, the principle of centrifugal separation is that the fuel to be purified is separated by a plurality of separators that are rotated at a high speed: water and impurities are extracted along the lower plane of the upper separator and finally accumulated in the sludge space; separating water along the top plate and The separation cylinder cover is pumped by the water impeller; the purified fuel reaches the oil discharge chamber through the LEVELRING inside the top plate, forming a liquid ring belt rotating at a high speed with the separation cylinder, and the fuel at the outer edge is centrifugally centrifuged. Under the action of kinetic energy, enter the oil impeller hole to increase the capacity (deceleration) and expand the pressure, and discharge it from the net oil outlet pipe.

As a water separator, a specific gravity ring adapted to the fuel density is used as a dividing machine, and a minimum diameter specific gravity ring (the heterocyclic ring of the clearing disc, a diameter of 66 mm) and a liquid level ring having a diameter of 116 mm are used.

When the No.2 heavy oil separator is operated as a water separator, the following abnormalities are continued for a long time: from the glass observation mirror of the water outlet, the separated water becomes black and emulsified, indicating that oil is discharged; often the oil separator outlet is drained. Low-pressure alarm; statistical analysis of fuel slag rate of up to 2%, exceeding the conventional slag rate provided by the oil supplier (about 1%).

Obviously, the failure of the N.2 heavy oil separator is not that the slag outlet runs oil, but that the drain port runs oil and is unstable.

In view of the fact that the fault lasted for a long time, multiple inspections and adjustments were not eliminated. The idea of ​​taking over this fault this time is to list the measured pressure gauges, up to 0.2 MPa). According to the analysis of the previous utilization, if the relative humidity of the crankbox is 60%, the air pressure reaches 0.2MPa, and the atmospheric dew point temperature is td=22, according to the diagonal line corresponding to the 0.2kg pressure of the crankcase, the pressure dew point temperature Td can be found. 38 feet, more than the cooling water temperature of the cylinder liner (30 feet), more turbid water in the crank box.

In the previous years when the equipment was put into use, the cylinder liner/piston ring was less worn, less helium, and could be discharged in time. The pressure of the crankcase was not high, so the condensation was less. As the cylinder liner/piston ring wears more, the helium gas is more, and it cannot be discharged in time, resulting in an increase in the pressure of the crankcase, and the conditions for generating condensation.

Remove the ball of the original venting check valve, replace the oil in the oil sump, and use no oil for 500 hours. This confirms that the above analysis is correct.

2 Corrective measures to improve the venting device. Seal the original venting port of the crank box, newly install the ventilated elbow (see), install a wire mesh cover at the opening (recommended near the hole 1mmx 1mm according to personal experience) to prevent the debris from being inhaled, enhance the ventilation effect, and prevent the pressure of the crankcase Too high.

Plug ring to reduce helium.

(Slightly higher than 33 feet). It can be adjusted manually to reduce the flow of cooling seawater; or to cool the seawater from other equipment to lead the way as air compressor cooling water.

Improved Ventilation Bend * Author Huang Wenlong, Chief Engineer of the North Sea Rescue Bureau of the Ministry of Communications, Class A First Class Chief Engineer.

Wang Lianhai. Lecturer of the School of Maritime, Shandong Jiaotong University, Class A first-class engineer, engineering master, is engaged in maritime teaching and research.

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