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1 Overview
Air compressor (hereinafter referred to as air compressor) of the explosion, the recent number of enterprises in the country have occurred, causing a greater loss to the enterprise. In foreign countries, there are statistics of the explosion. According to the classification of air compressor equipment, transmission structure, there are two types of reciprocating and rotary. Prone to failure and explosion damage, mainly reflected in the reciprocating air compressor. Therefore, the explosion-proof of the reciprocating air compressor should arouse our attention. The causes and preventive measures of the explosion of the reciprocating air compressor are described in the following.
2.Three elements of air compressor explosion
According to the working characteristics of air compressor, the air is compressed by one or more than two levels. Cylinder and piston need lubricating oil will generate carbon deposition, compressed air will be a substantial warming, air containing oxygen, so that the formation of the air compressor explosion of three elements: carbon, temperature, air.
2.1According to the coking experiments show: the exhaust valve on the exothermic reaction of deposit formation occurs at 154 C and 250 C temperature range. The process for lubricating oil mist or stick on the metal surface, under high temperature and high pressure, especially under the condition of the contact metal, quickly air oxidation, oxidation of polymers (gelatinous sludge, etc.), deposited on metal surface, continues to be heated by the role, thermal decomposition hydrogen removal of reaction formed hydrogen of coke. Coke thickness more than 3mm, there is a danger of spontaneous combustion. In addition, coke influence the heat dissipating efficiency, accumulation of heat and the formation of fire, a part of lubricating oil viscosity in coke fire point, evaporation and decomposition, resulting in cracking light carbon and hydrogen free carbon when and high temperature and high pressure air mixture explosion limit is reached when the explosion occurred. General lubricating oil heating decomposition, can produce the explosive limit of light carbon hydrogen in air in the air, CH45 - 15 C2H63 - 12.5C2H42.8 - 28.6C3H82.1 - 11.1, etc..
Thus it can be seen that the carbon deposition and local overheating is the main cause of explosion, and hydrocarbon gas and air mixture gas is main medium of explosion. The size and amount of coke produced lubricating oil oxidation stability of lubricating oil, gas quantity, quality and maintenance related.
2.1.1 air compressor piston lubrication oil is required to add a variety of additives on the basis of the refined basic oil. The base oil will have a direct impact on the amount of residual carbon size and base oil (such as Lanzhou, Xinjiang), thermal oxidation stability, carbon residue value is small, the speed of lubricating oil deposit formation is low, it is difficult to form a large number of coke, so choose compressor oil is very important.
2.1.2 air compressor cylinder lubricator oil volume size, a direct result of the generation quantity of carbon deposition and oil sludge, oil and gas, such as 40 m3 secondary compressed air compressor, standard level cylinder oil 12 - 18 drops / min, second stage cylinder oil 12 - 15 drops /, more than the provisions of excess lubricating oil will be adsorbed on the depression and on the wall of the pipeline, generated sludge and coke, only a part with the compressed gas discharge.
2.1.3 maintenance is not timely, charcoal cleaning effect is not good, but also to promote the accumulated large amount of coke. According to the survey, intermediate cooler, after cooler and pipeline is not easy to clean carbon site, where general deposit formation, oil sludge, the amount is larger.
2.2 temperature compressed gas temperature is a important condition for prompted an explosion of, according to statistics, air compressor, more than 50% of the 170 DEG C explosion. Therefore, all countries have stipulated the exhaust temperature shall not be more than 150 DEG C O 2.2.1 intake reduced by 10%, the exhaust temperature will rise 20 DEG C. Therefore requires the intake of adequate intake.
2.2.2 exhaust valve deposits caused by valve leakage, will cause the exhaust temperature. Such as: 700 kPa of the compressor normal exhaust temperature is 130, while the valve leakage will produce 270 temperature, it is easy to explode.
2.2.3 the amount of water is not enough, the scale of the air cooling is seriously bad, resulting in high temperature rise. This point is very important.
3.Explosion proof measures
In view of the above for the three elements and the cause of the explosion of air compressor explosion, can strengthen the following aspects of the work.
3.1 strengthen management of lubricating oil in order to control the coke formation rate, should choose good base oil, carbon residue value is small, suitable viscosity (IsOVG68-100), good thermal oxidation stability of (Conradson carbon residue value < 3%), high flash point of lubricating oil. Such as: I, DAB air compressor oil. The cylinder oil supply amount is not too large, the maximum shall not exceed 50g/m3, to prevent the increase of oil gas and coking coke increased. No open storage mode, to prevent oil impurities clogging exceed the standard lubricator. In addition, the air pressure oil to have a product certificate and oil test.
3.2 to strengthen the maintenance of equipment maintenance management air compressor parts of the situation, to regular verification, to develop a complete large and medium repair plan, the project should be specific, there is acceptance criteria. In particular, the regular cleaning of the work to be responsible for acceptance. Suction port should not be located in the interior, and to ensure that the provisions of the amount of suction, to prevent the air filter plug and reduce the intake, resulting in an increase in exhaust temperature. To strengthen water cooling, to ensure that the cooling water temperature difference between the water and the water is not higher than 10, even if the summer cooling tank outlet water temperature can not exceed 50. Periodically remove the compressor internal deposit, general inspection every 600 h to clean the exhaust valve, exhaust valve for each of the 4000 H.
3.3 to strengthen the operation management of air compressor can be used as a dangerous source to treat, so the operator should after training certificates. Operation personnel in strict accordance with the operation of the operation of the same time, to be able to the general air compressor fault to judge and deal with. Require the operator to empty compressor working principle, the cause of the explosion, reasonable oiling, regular blowdown, strict implementation of start stop system to have a clear understanding.
3.4 improve monitoring capabilities of the operation status of air compressor in ensuring the empty air compressor cooling, temperature and pressure instrumentation display, safety valve and so on basic safety facilities based on, should also be in the exhaust valve outlet pipe series, automatic temperature alarm, strict control of temperature can not exceed the provisions of 150 DEG C.
4.Typical case analysis
An enterprise air compressor workshop, a L5. 5 - 40/8 air compressor in March 2000, an explosion occurred. By field investigation, the main damage form of air compressor gas supply system is:
(1) air compressor: air compressor two cylinder lower cylinder, base burst, the valve chamber broke, after the cooler, the cooler, the inner core burst. Two cylinder compensator to cooler the burst, cast iron pipe burst, and the section of the sludge, etc. there are a lot of coke. The upper wall partition wall in most plants.
(2) pipe network: from the air compressor workshop to air door about Dg219, mm 200m pipe 2/3 appear interface, from the stand on the ground. No groove weld pipe interface, the height of 3 mm and welding pipe welding defects and meat.
4.1 damage state analysis
4.1.1 from damage form (1) analysis, in the air compressor workshop as the source of the explosion. The two stage cylinder to the rear cooler for the explosion of the section and the form of damage, so the damage caused by the block equipment. The explosion shock wave to part of the plant wall strength is weak, the impact damage collapse.
4.1.2 pipe network damage is due to the lack of weld strength, the impact caused by the explosive gas shock wave caused by the welding mouth tear. With the addition of a pipeline on the bracket fixed is not solid, pipe bending arrangement uneven stress caused by the impact of pipeline bounce after falling.
4.2 explosion cause analysis
4.2.1 from oil field, cooler of coke (3 - 4 mm thick), a valve chamber (product oil is serious, local clay thickness of 10 mm), indicating that the air compressor lubricator oil injection quantity and timing of emission is not timely, clear maintenance carbon is not complete, resulting in sludge, coke, coke deposits.
4.2.2 air compressor inlet is arranged in the adjacent iron workshop, dust quantity is big, easy to plug the air filter, resulting in the intake of small, high exhaust temperature. Also examined from the composition of coke prove a small granular dust, dust and the lubricating oil with the easy formation of sludge and coking, is not conducive to the compressed air cooling. Coke and Coke will cause the exhaust valve lax, cause leakage caused by the exhaust temperature, so it has high temperature conditions.
4.2.3 the air compressor cylinder lubrication using HS - 13 compressor oil, no oil certificate and laboratory tests. After the oil test of the oil, dirt and ash are exceed the standard, thermal oxidation stability index by not doing. This oil is compared with the current L - DAB air compressor oil, because of its fast speed of deposit formation has been eliminated. So the use of old oil is one of the reasons for the increased carbon.
Together, the air compressor cylinder lubricating oil management was not standardized, operation, maintenance and other issues, resulting in air compressor carbon deposit generated a large amount and high exhaust temperature. At the second stage cylinder exhaust valve produce coke and fire point, the lubricating oil in high temperature thermal oxidation decomposition intensifies, when produced lightweight carbonization and hydrogen free carbon in the compressed air reaches the explosion limit, and is formed by the explosion. So the coke and the local overheating is the main cause of the explosion. Operators found abnormal is not timely and also one of the causes of the accident.
5.Conclusion
The reciprocating compressor currently has three elements: carbon, inevitable temperature and air, the feasibility of the explosion. Therefore it requires the air compressor of the explosion-proof work to the daily management of the implementation of the clear, detailed, air compressor safe operation on a real guarantee. For enterprises in the future of the equipment transformation, as far as possible the use of non oil reciprocating air compressor, from the root causes of the explosion accident.
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