High temperature causes and solutions for air-cooled screw air compressor

The fully reliable, harmless and non-polluting compressed air has become an indispensable power source for factory enterprises. It is widely used in power transmission, pneumatic tools, surface coating and rust removal of steel structures, and automation control. Among hundreds of process equipment, it is one of the indispensable equipments in every production enterprise as an air compressor that produces compressed air.

Economic development and technological advancement, energy-saving, longevity, low-pitched and low-pollution screw air compressors have gradually replaced the old-fashioned piston-cylinder air compressors with their reliable and superior performance in various enterprises. It is rapidly spreading. At the same time, it also brought a series of new problems in the use, maintenance, maintenance and repair of screw air compressors. Running high temperature (surface temperature higher than 100 ft) is one of the most common failures of screw air compressors, especially in summer, which is one of the problems that plague many air compressor users. Practical experience is explored.

2 The temperature of the dangerous temperature will also generate heat, and the pressure is proportional to the heat. Therefore, the air compressor produces compressed air, and some by-products are generated. The higher the pressure, the larger the flow rate. The more heat there is, if the air compressor is to operate continuously and reliably, this part of the "by-product" must be cooled to the appropriate temperature (typically 80 to 90 feet).

There are more than a dozen brands of screw air compressors today, dozens of models, which can be divided into two types according to the cooling method: water-cooled and air-cooled. Water-cooled uses both circulating water to remove the cooling oil through the heat exchanger. Heat; air-cooled uses both flowing air to remove heat from the cooling oil through the radiator. Compared with the two cooling methods, the air-cooled type reduces the cooling tower, the reservoir, the circulation pump and the pipeline, etc., which is relatively simple and is generally welcomed by the majority of users.

Therefore, we have mostly air-cooled air compressors in the north, accounting for more than 90% of the total.

According to the principle and structure of the air-cooled screw air compressor, the circulation of the cooling oil is: separator tank (oil pool) - temperature control valve - radiator - filter - compressor - separator tank (oil pool). The cooling part is that the fan is forced to flow air through the heat sink capillary, taking away heat to cool.

Air compressor units operating under long-term high temperature or quasi-high temperature will cause the following hazards: air intake - air * oil filter quality, aging and even coking, carbon deposits, oil filter and oil separator, to maintain normal operation Frequent replacement of oil and gas separators and oil filters has increased operating costs and maintenance workload.

The inner wall of the capillary of the radiator makes the capillary thinner, the flow of the cooling oil is reduced, and the heat conduction is affected, which further aggravates the high temperature phenomenon, causes a vicious cycle, and finally blocks the radiator.

The oil hole of the compressor bearing causes the bearing to be poorly lubricated, which accelerates the wear of the bearing. The lighter wears the rotor and the casing (the gap between the rotor and the casing is 0.10~0.12mm), and the rotor and the end are severe. The cover is stuck and the compressor is scrapped.

Temperature protection device (generally the maximum protection temperature is 11 zhang~12 ft). When the temperature of the unit reaches the protection temperature, the unit will automatically stop for 20~30min, which will seriously affect the production. Some enterprises can not produce at the same time.

3 Analysis of the cause of high temperature analysis of the failure to analyze the following reasons and the corresponding solutions: 3.1 external clogging of the radiator due to long-term operation of the air compressor unit forced air flow through the radiator, cooling air is inevitably carried in the air Oil, dust, even weeds, leaves, feathers, tidbits, shovel bags and other debris will block the capillary pores outside the radiator. In severe cases, even the light will not pass through, so that the cooling air cannot pass through the radiator or the throughput is insufficient. The heat sink loses the function of cooling and dissipating heat, and the cooling oil cannot be cooled or cooled after passing through the radiator. Generally, the air compressor of the fixed product has a heat sink area (cooling capacity) of 20%~30% when designing and manufacturing. When the temperature drop of the cooling oil is less than the remaining amount, the air compressor will generate high temperature.

3.2 The inside of the radiator is clogged with different content of base oil. The oil additive is different. The composition of synthetic oil and mineral oil is different. If different grades of cooling oil are mixed, the air compressor will run thick under high temperature and high pressure. The char is attached to the inside of the heat sink capillary, solidifies and hardens after cooling, and gradually accumulates until the capillary is completely blocked.

The cooling oil will cause carbon deposits to adhere to the pipe wall, and the corners are more likely to adhere. As the thickness of the carbon deposit increases and the vibration of the machine runs, the carbon deposits will fall off into flakes or granules, blocking the capillary and bearing oil holes. Not only does the high temperature of the air compressor accelerate the bearing wear.

However, in the oil, the oil, grease, oxides and metal abrasives are generated in the cooling oil and adhere to the inside to make the capillary thinner until it is clogged.

The reason is that the thermal conductivity of the radiator is reduced, the flow of the cooling oil is reduced, and the cooling capacity of the radiator is reduced until failure, resulting in high temperature of the unit.

3.3 Temperature control valve failure 6m3/min air compressor unit No matter what brand is equipped with temperature control device, its function is to facilitate the air compressor unit to start in winter; the second is to maintain the best balanced oil temperature during operation. (usually 80~90 feet). The temperature-controlled wide core is filled with ether inside. When it expands with heat, it generally starts to operate at 65T. The valve stem pushes the valve core to control the opening of the large oil hole and balance the amount of cooling oil entering the radiator. The long-term use of the thermostatic valve core (usually 1~3 years) will cause ether leakage or fatigue, so that the spool thrust is not enough or no push or the valve core is stuck in a certain part, so that the amount of oil involved in the cooling cycle is reduced, resulting in high temperature of the unit. .

3.4 If the oil filter blocks the carbon deposit, it will inevitably block the oil filter; (2) If it is more than 2 maintenance cycles without maintenance, it will inevitably block the oil filter; (3) If the air with insufficient filtration density is used There is a leak in the filter element or the intake pipe. The dust in the air will enter the cooling oil in the machine with the air. Most of the circulation will collect on the oil filter, and the oil filter will be blocked for a long time.

Blockage of the oil filter will reduce the amount of oil involved in the cycle, causing the unit to heat up. 3.5 No cooling air or cooling air volume is insufficient to stop; road, motor stops; fan stops; makes the fan impeller and output shaft not synchronized, commonly known as "belt slip" and "fan turn" cause insufficient cooling air volume; insufficient air volume.

3.6 Oil and gas separation core plugging Any brand of screw air compressors has oil and gas separation devices, which function to separate the compressed air in the oil and gas mixture and discharge it from the outlet, leaving the cooling oil in the separator to continue the cycle, the new oil and gas separation The density of the core is 3~5|xmm, and the initial pressure difference before and after separation is 0.01~0.03MPa (pressure difference = pressure before separation - pressure after separation).

The phenomenon of carbon deposits, etc., will block the oil and gas separation core while blocking the oil filter and the radiator; (2) The service life of the general oil separation core is 4000~6000h, and its density will increase with the extension of the running time (less than 3mm). ), commonly known as "oil partitioning, the pressure difference increases, and the pressure rises before separation."

According to the principle that the pressure is proportional to the temperature, the larger the pressure difference, the greater the pressure before the separation, the more heat the unit generates. If the cooling capacity of the radiator exceeds the cooling capacity of the radiator, the safety valve will jump (the general safety). The take-off pressure of the valve is greater than the outlet pressure of 0.15 MPa).

3.7 The amount of cooling oil is insufficient. The separation density of the machine is 3xl-6, that is, the compressed air produced by it has a oil content of 3xl-6, ie 0.03mL/m3 (0.03mL of cooling oil per cubic meter of compressed air). For example, a 10m3/min unit consumes 30mL of cooling oil per day.

Inevitably, pipelines, joints, seal parts leak or oil separators run oil. If it is not discovered in time, timely repair will result in insufficient cooling oil.

However, the amount of oil circulating is too small, causing the unit to be ancient; æ›°3.8 poor ventilation is too small, P is too strong; (2) the ventilation duct is too long and the resistance is too large; (3) the ventilation tube is bent too much and the resistance is too large.

Although the unit cooling system has no faults, the unit temperature is caused by insufficient ventilation.

3.9 Ambient temperature is too high The air-cooled air compressor should not exceed 35. The following reasons can cause the ambient temperature to be too high: (1) no window or single-sided window; (2) in the sunny space or in the basement, And no ventilation ducts are installed; (3) there are other equipments that generate heat sources in the equipment room; (4) the indoor space is too small.

The above reasons cause the indoor temperature to accumulate higher, resulting in high temperature of the unit.

3.10 There are foreign matter blocking in the circulating oil circuit. This phenomenon is rare, but it also occurs from time to time. Common foreign objects include uncleaned casting sand, rubber gasket on oil filter, oil filter, filter cotton filter on oil. The broken star wheel fragments on the single-screw unit, the foreign objects dropped during refueling, etc., these foreign objects are blocked in the pipeline, causing the unit oil circuit to circulate poorly, resulting in high temperature. Usually these foreign materials are more clogged in the thinner diameter pipe in the oil system.

3.11 Inappropriate temperature setting Some computer version units use temperature sensors to control the start and stop of the fan motor. If the set control temperature is too high, the unit operation must be high temperature. 3.12 Unit overload operation Some air compressor units due to improper selection or expansion of production scale, resulting in insufficient pressure and displacement, artificially overloaded, causing temperature rise.

4 Solution Out of the cooling oil, remove the radiator, first use 0.5 ~ 0.7MPa compressed air to purify the front and back sides of the radiator, remove dust and debris, and then use a misty oil cleaning agent or banana water (away from the fire source) to purge The oil on the gap and surface reveals the metal surface and can be reinstalled.

Cool the oil, remove the radiator, pour out the residual oil inside, soak the inside with an alkaline carbon stain cleaner with a pH greater than 10 for 6~8h, then rinse it with clean water, blow it with compressed air, and reinstall it. .

Be sure to use a cleaning agent that does not oxidize or corrode non-ferrous metals. The above two methods are used at the same time.

The unit is high a丨; c control valve core, soaked with 90 feet of hot water for 5min, if the opening of the valve core or the action of the valve stem is less than 10mm, it can be judged that the valve core is invalid, and it is unobstructed on the slide that confirms the action of the temperature control spool. When you replace the new valve plug.

The oil filter must be replaced at the same time, and the inlet pipe should be inspected and sealed, and an air filter of appropriate density should be used.

Replace the motor, reset the thermal relay, replace the adjustment belt, pulley, and vane.

Change the oil separation core and replace the cooling oil and oil filter.

Cooling oil, the amount of cooling oil should be kept at 2/3 of the oil window or oil level gauge. Too much will increase the oil content in the compressed air. If too little, it will cause high temperature. The oil level should be checked once a day.

The cross-sectional area should not be less than 80% of the radiator area, and the length of the ventilation pipe should not exceed 10m. The elbow of the ventilation pipe is only allowed to have one, the elbow should have a circular arc transition, and the outlet should be free of obstacles within 1m.

Open the ventilation window on both sides or install the induced draft fan, open the heat source of other equipment to enhance the indoor ventilation, and install the ventilation duct in the underground room to reduce the indoor temperature to below 35 feet.

Check the thin pipe joints, remove the pipes, and remove foreign matter.

The appropriate temperature value is set at 70~80 feet in summer and 80~90 feet in winter.

Low pressure and reduced displacement.

5 Inspection and judgment method The reason for the high temperature problem of the press operation can be checked and judged as follows: The difference between the air-cooled air compressor unit and the water-cooled type is that the air-cooled type uses the cooling air to blow the heat sink to remove heat. The water-cooled type uses the cooling water to remove heat through the heat exchanger. Therefore, in addition to the above reasons, the water-cooled unit should also check that the cooling water temperature of the air compressor unit should not exceed 32T:; excessive wear will make the circulating water Insufficient pressure, insufficient water (the water pressure entering the air compressor unit must be greater than 0.3MPa); scale, sludge will seriously affect the cooling efficiency, the maximum heat exchanger inlet, the fan sensor failure, the outward exhaust, not the external heat blocker Lost. Blade deformation fan motor damage or power-off fan set temperature too * Ambient temperature is too high Oil-deficient temperature control valve failure Oil filter oil and gas separation core blocking cold pipe has a foreign matter internal blockage * fruit, is inevitable, Therefore, it must be cleaned once a year.

6 Precautionary measures and conclusions In summary, if the service life of the air compressor unit is to be extended and the production is continuously carried out, it is necessary to make predictive maintenance on the unit to prevent it from happening: (1) Strengthen the responsibility of the operator Heart and post responsibility system, regular inspections, timely detection of problems, timely report and timely resolution, the elimination of the failure in the bud, not allowed to run with the disease, to prevent run, run, drip, leak phenomenon, every shift to do a good job record. (2) Regular maintenance, regular maintenance, timely replacement of air filter, oil filter, oil separator core and cooling oil, regular cleaning of the radiator, inspection of fans, belts and fan motors, etc., and maintenance records. (3) To use qualified parts, especially cooling oil, be sure to use quality-assured oil. Different brands of cooling oil can not be mixed. (4) Continuously improve the conditions of work and the environment, keep away from dust, keep away from high temperature, keep away from pollution, and improve ventilation.

In case of sudden failures including high temperature (see other related articles for other types of faults), do not panic. Engineering and technical personnel and maintenance workers should be based on the inside and outside, and from the outside to the inside. From simple to complex principles, "looking, smelling, asking, cutting", with the help of instruments and meters, accurately determine the cause, "the right medicine, hand to disease", do not blindly SL, not only increase the amount of labor, Delayed time, but also easy to hurt the flawless parts.

7 Conclusion In the work, we are gratified to see that many units have turned waste into treasure, making full use of the heat of the by-product of the air compressor, and achieving “low-carbon production” in the near future. For example, a 4S shop in an automobile changes the air-cooled radiator into a heat exchanger, and the hot water generated is provided for the staff bath; a coating factory introduces the hot air blown from the air compressor into the staff lounge to solve the problem of heating in winter, and a textile factory will be empty. The hot air of the press is introduced into the workshop to keep the workshop constant. We think this is a good development direction. All units can take advantage of this part of the energy and make a new contribution to our maintenance technicians. I believe that there will be a lot to do in this topic.

Today, air compressors have been basically popularized. So far, China has not issued a systematic and authoritative book on the use, maintenance and maintenance of screw air compressors. The manufacturer’s instructions only made troubleshooting. Brief introduction, it is impossible to summarize the various characteristics of various enterprises and the various problems arising therefrom, and the lack of specialized personnel, so the maintenance and maintenance work of the screw air compressor is still very poor and not standardized. . It takes a long time to work to have a rule-based management approach.

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