Compressor accidents that must be prevented

Compressor is an essential power equipment for chemical and petrochemical production. From the energy point of view, the compressor is a machine that converts the power energy of the prime mover into gas pressure energy. With the development of science and technology, the application of pressure energy is becoming more and more extensive, which makes the compressor become one of the essential key equipment in many departments of national economic construction. During the operation of the compressor, it is inevitable that there will be some failures and even accidents.

combustion explosion accident

in chemical and petrochemical production, the risk of compressor combustion and explosion accidents is great, which not only seriously affects the safety and stability of production, but also causes serious economic losses, but also causes casualties and destruction of buildings. Therefore, the compressor combustion explosion accident has attracted great attention.

Most of the compression medium of petrochemical compressor is flammable and explosive gas, and it is easy to leak under high pressure. Flammable gas leaks through defective parts such as cylinder body joints, suction and exhaust valves, flanges, welded joints and seals of equipment and pipelines; compressor parts are fatigue and broken, and high-pressure gas rushes out to the plant space; air enters the compressor system and forms explosive mixture. At this time, if the operation, maintenance or repair is improper during operation, maintenance and repair, the mixture of combustible gas and air that reaches the explosion limit concentration will burn abnormally and even cause explosion accidents when it meets the fire source.

For oxygen compressors, if the oxygen flow is mixed with flammable gases, grease, rust, paper scraps and other impurities and metal objects, when the lubricating fluid is suddenly interrupted or the supply is too insufficient, it will cause the cylinder to "dry grinding" and cause high temperature. Under high pressure and high temperature conditions, the combustibles in the cylinder quickly react with oxygen to cause spontaneous combustion. Due to the accumulation of heat and the combustion of high-pressure oxygen, the combustion can be intensified, resulting in extremely serious cylinder combustion and explosion accidents.

Most of the cylinder lubrication of petrochemical compressors and air compressors uses mineral lubricants, which are combustibles. When the temperature of the gas rises sharply, it will produce strong oxidation after exceeding the flash point of the lubricating oil, and there will be a danger of combustion and explosion. In addition, the lubricating oil molecules present in suspension are easy to react with oxygen in the air under high temperature and high pressure conditions, especially the oil film attached to the hot metal wall of the exhaust valve and exhaust pipe, and its oxidation is even more intensified., Generate acid, asphalt and other compounds. They are combined with dust in the gas and metal particles produced by mechanical friction, and deposit in the cylinder head, piston ring groove, air valve, exhaust pipe, buffer tank, oil-water separator and gas storage tank to form carbon deposits.

Carbon deposit is a kind of flammable material, which may cause spontaneous combustion or even explosion under the conditions of high temperature overheating, accidental mechanical impact, airflow impact, electrical short circuit, external fire and electrostatic spark. Carbon deposits produce a large amount of CO after combustion. When the CO content in the compressor system reaches 15% ~ 75%, an explosion will occur, and a large amount of heat will be released at the instant of the explosion and a strong shock wave will be generated. Due to the rapid increase of gas pressure and temperature and the rapid expansion of combustion products, the shock wave spreads along the direction of compressed gas flow at supersonic speed, causing continuous explosion in many places.

During the starting process of the compressor, the air in the compressor system is not replaced by inert gas or the compressor system is not completely replaced (the oxygen content exceeds 4% or impurities such as combustibles remain). Due to lack of operation knowledge, the outlet valve and bypass valve of the compressor (or ice machine) are not opened to cause overpressure. During the operation, the gas pressure is too high due to the instrument failure of the compressor gas regulation system, can cause combustion and explosion accidents.

Accident causes and preventive measures:

1. Serious leakage of combustible gas

(1) suction, exhaust valve failure, sealing is not tight, causing leakage, causing fire and explosion.

(2) serious leakage at the shaft seal, causing fire.

(3) The valve flange connected to the high-pressure synthesis system leaks, and the lighting joint is short-circuited, causing fire and explosion. The pressure gauge root of the outlet manifold of the circulating machine leaks, high-pressure gas rushes out, resulting in electrostatic fire and explosion. The cylinder leg of nitrogen and hydrogen compressor is broken, and the inlet pipeline leaks, causing explosion in case of open flame.

Precautions:

(1) Reasonably arrange the suction and exhaust valves to ensure the flexibility and air tightness of the valve action, clean up the dirt and replace the valve in time.

(2) reasonable installation of piston rod and packing, regular inspection of wear, timely replacement of packing. The turbine oxygen compressor shall be equipped with an air-tight device to flow the safety sealing gas into the shaft seal part, and an adjusting device to maintain the pressure difference with the balance chamber.

(3) The pipe fittings such as pipelines, valves, flanges and instruments shall be reasonably installed to ensure the reliable sealing of the connecting parts, and the leakage of the connecting parts shall be checked frequently, and the gas leakage detection device shall be set to monitor the abnormal phenomenon of the sealing system.

2. Due to corrosion and fatigue fracture, flammable gas is ejected

(1) Fatigue fracture of the vent pipe at the outlet of the circulating machine and ammonia leakage cause fire and explosion.

(2) The thread roots of the connecting bolts between the multi-stage cylinders and between the cylinders and the fuselage are fatigue fractured, and a large amount of high-pressure gas is ejected, causing fire and explosion.

(3) The damage of the fuselage and high-pressure cylinder causes the oil system to catch fire, the cylinder liner is of poor material, and the cylinder body has serious shrinkage defects and fatigue fracture, causing high-pressure gas to rush out and cause space explosion.

(4) The root of the piston lock nut thread and the root of the connecting thread of the piston rod and the piston are fatigue and fractured, and the piston rod blows and fires and causes an explosion.

Precautions:

(1) Reduce the vibration of the compressor piping system and ensure the quality of the pipe and weld.

(2) Ensure that the structure and geometric dimensions of the connecting bolts are reasonable, the material is excellent, and the strength and processing accuracy of the thread are improved; ensure that the connecting surface is closely fitted and the tightening force is appropriate.

(3) Strictly inspect the quality of the fuselage, cylinder block and cylinder liner; diagnose the remaining life of the main parts of the high temperature and high pressure compressor.

(4) Improve the quality of heat treatment process to ensure the strength of the piston rod; use arc rolling threads to improve the machining accuracy of threads; ensure high quality in manufacturing and installation to avoid additional bending moments.

3. The temperature and pressure is too high, carbon spontaneous combustion and combustible combustion

(1) Improper selection of cylinder lubricant, inconsistent lubricating oil brand, too much or too little oil, poor oil quality, so that the gas temperature rose sharply, the formation of carbon deposits.

(2) the circulating cooling water quality is poor, the intermediate cooling effect is not good, the cooling water is accidentally interrupted, resulting in an increase in gas temperature. The discharge of oil and water from the intercooler, oil-water separator and gas storage tank is not timely or complete, which increases dirt and resistance and increases the temperature of the gas.

(3) Use air to test pressure and leak, carbon deposits at high temperatures, intense oxidation and explosion; during the mechanical manufacturing process, rust and other impurities are not removed, resulting in heat; the filter is seriously fouled, and the inhaled gas contains a large amount of dust, which is easy to form Carbon deposits.

(4) lack of security measures and modern management tools.

Precautions:

(1) Reasonable selection of lubricant according to the nature of the gas, non-emulsified mineral oil for acetylene gas, concentrated sulfuric acid for chlorine gas, distilled water and diluted glycerin for oxygen, white oil or oil-free lubrication for ethylene gas; Select high-grade grease with high flash point and less carbon precipitation after oxidation; The amount of oil injection is appropriate. For the piston moving area of 200 cm2/min, the amount of oil injection is about 0.01 L/h. Regular oil quality analysis, timely replacement.

(2) Adopt advanced water quality treatment technology, regularly remove dirt, discharge oil and water, and strictly control the exhaust temperature, which shall not exceed the allowable value.

(3) Fully remove the foreign matter and rust in the casting and piping, and blow the entire compressor system completely after assembly; select corrosion-resistant materials, select high-efficiency filters, and remove dirt in time.

(4) Set explosion-proof wall and inert gas fire extinguishing device near the compressor with explosive gas. For high pressure, flammable and explosive gas safety valve should always check its reliability. The instrument measurement and automatic alarm device are adopted, and safety measures can be taken in time when abnormal faults are found.

4. Misoperation, illegal operation, resulting in combustion and explosion

(1) When overhauling the nitrogen-hydrogen compressor, aluminum plate is used as a blind plate to cause space explosion due to high-pressure gas ejection; The bypass valve and outlet valve were not opened when the ice machine was started, and the pressure increased beyond the material strength limit, resulting in explosion. During the operation of the blower, abnormal noise was found and the machine was not stopped for inspection in time, resulting in the twist of the fan journal and the fire and explosion of the oil tank.

(2) When the compressor for chemical industry is tested under load, it is not blown with low-pressure nitrogen or is not completely blown away, causing combustion and explosion.

(3) Incomplete oil prohibition treatment will cause the filler to catch fire with oil and the oil collecting tank to explode.

(4) Mistaking that there is no liquid ammonia at the outlet of the ice machine section; After hearing the sound of liquid hammering, no liquid discharge treatment was carried out. The shortcut valve was used, and the liquid ammonia was gasified by high temperature and exploded.

Precautions:

(1) Familiar with the operation knowledge, open the outlet valve of the compressor (or ice machine) before driving, and pay close attention to the pressure and temperature changes of water, gas and oil and abnormal noise after driving.

(2) Load test, when starting the flammable gas compressor, first replace the air with inert gas to make the oxygen content less than 4%. For compressed hydrogen and acetylene gas, the oxygen content limit is 2%. The load test must be carried out in strict accordance with the operating procedures.

(3) It is forbidden to use gasoline and other volatile oils to clean parts. During the manufacturing and installation process, try to avoid contact with the atmosphere, strictly implement the prohibition of oil treatment and control the oil temperature.

(4) Careful operation.

5. Explosion accidents caused by manufacturing defects and poor management

(1) The outlet valve of the oxygen compressor is damaged, causing overpressure and the safety valve to jump, causing fire and explosion; The oil-water separator exploded due to manufacturing defects; The buffer exploded due to operation with water.

(2) During operation, the pressure is too high, the water seal is washed out, a large amount of high-pressure gas is vented, and electric spark is ignited.

(3) Due to power failure, the decompression gas of the propylene gas compressor overflows. When restarting, the relay generates sparks, causing space explosion.

(4) the motor insulation aging caused by fire, burn the compressor.

Precautions:

(1) Strengthen quality management and quality inspection, and timely remedy or replace wearing parts when defects are found.

(2) Keep a close eye on the change of the pressure gauge reading.

(3) Strengthen the maintenance and maintenance of the motor relay.

(4) Replace the motor with aging insulation in time.