Heat exchanger is petroleum,
chemical, metallurgical, power, grain and oil, refrigeration, food processing and widely used in the defense industry in areas such as a general process equipment.
In petrochemical plant, heat exchanger investment accounts for about more than 20% of the total investment, accounting for more than 40% of the total quality equipment.
The effect of the heat exchanger, there are two: one is through the heat exchange makes logistics process temperature reached the requirements of temperature, to complete the heating, cooling, evaporation and condensation processes;
Second, can effectively use the heat source, it has become an indispensable equipment in waste heat recovery, etc.
However, some of the heat exchanger is under high temperature and high pressure working conditions, such as the working medium pressure up to 250 mpa, operating temperature up to 1000 ~ 1500 ℃;
Some of its working fluid have the characteristics of flammable, explosive, toxic, corrosive, combined with the chemical and petrochemical production requires large quantity, continuity is strong, therefore, it brought certain difficulties to the normal operation of the heat exchanger, a bit careless accident occurs, endanger the life safety of the employees.
The main accident type heat exchanger are burning explosion, serious leakage and bundle out of control.
Unreasonable including design, manufacturing defect, improper material selection, corrosion is serious, error and poor management is the main cause of accidents result in heat exchanger.
The causes of the accident in detail for you: 1 burning explosion accident reasons: (1) heat exchanger, equipment structure and material to make bigger changes blindly, manufacturing quality is poor, do not conform to the pressure vessel code, equipment strength is reduced greatly.
(2) the welding quality is poor, especially in weld lack of penetration, joint and not inspection, blasting pressure testing of weld inspection, lead to welding head leak or produce fatigue fracture, and a large number of flammable and explosive fluid overflow, in case of fire, explode.
(3) due to corrosion (
Including stress, intergranular corrosion)
Crushing strength decline, the tube bundle failure or severe leakage, fire explosion.
(4) heat exchanger for air tightness test, will use the oxygen filling pressure with combustible refining gas leakage, caused an explosion of the physics and chemistry.
5. Illegal operation, operator error, cause explosion overpressure valve is closed.
6. Not for a long time of drainage, flammable and explosive substances (
Such as nitrogen trichloride)
Accumulation is overmuch, coupled with high temperature cause heat exchanger (
Such as liquid chlorine heat exchanger)
In a violent blast.
All landowners oxygen bomb attacks.
Preventive measures (1) heat exchanger design, the manufacture should comply with the specification requirements of the national pressure vessel and drawing modification and changes must be approved by the competent department of experience quality qualification.
(2) heat exchanger manufacturing, welding quality and strict inspection of weld.
(3) fluid for the corrosive medium, and attention should be paid to improve the material quality and welding quality, and increase the wall thickness or add corrosion in fluid preparation, regularly check the pipe surface corrosion situation and to test the easy corrosion damage of equipment, to take effective measures.
(4) heat exchanger for air tightness test, must be the adoption of dry air, nitrogen and other inert gases, oxygen or combustible gas experiment or fill pressure is strictly prohibited.
(5) it is forbidden to illegal operation, strict operation regulations.
6 for easy scaling of the fluid can be regular cleaning, scaling to clean off.
All landowners strictly control the content of oxygen.
Case study: heat exchanger overpressure explosion accident case study 1.
Accident after briefly entrusted by a petrochemical general factory of a chemical plant, the nuclear industry department's fifth installation company, in 1986 March 15 heat exchanger of a chemical plant air tightness test.
16 35 points, when the air pressure to 3.
Suddenly exploded when 5000000 mpa, the bolt pressure ring is pulled, nut off, separation, heat exchanger tube bundle and shell weight of four tons of tube bundle after forward out of 8 meters, hit the yellow card carrying air compressor on the truck, the truck was over 2.
3 meters, bundle from in situ rushed out of the 8 meters, weight of 2 tons of shell to fly out of 38 in the opposite direction.
5 meters, hit the ground on the pile.
Overlap, two heat exchanger bearing bolt connection is cut, connecting flange short tube is pulled, the release of two sets of equipment.
Weighing six tons of unexploded heat exchanger by the reaction, the entire southeast displacement of 8 meters, and to 170 degrees.
In the field work of four people die because of the explosion.
The explosion caused a direct economic loss of 56000 yuan, the indirect economic loss of 25000 yuan.
2.
The cause of the accident analysis (
1)
Operating personnel in violation of the operation.
Explosion heat exchanger 40 fastening bolts, but operators only 13 bolt for air tightness test, and because of the pressure testing thickness thicker than the original connecting flange 4.
7 cm, the original length of the bolt is not enough, but the operator still make do with the original bolt, the bearing bolt number more than half of cases, each bolt can bear the load and has obvious drop, due to the actual load of each bolt more than design carrying capacity, the bolt is pulled, after an explosion heat exchanger.
This is a typical explosion accidents caused by illegal operations.
In the past few decades,
cosmetic machinery manufacturers production has increased because of the use of chemical reactor.
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