Factors Leading to Damage in Pressure Vessels
The operational environment of pressure vessels in chemical equipment is intricate, with corrosion, cracks, and deformations posing potential risks of severe injuries. Instead of focusing solely on post-damage treatment, greater emphasis should be placed on proactive prevention and control. This approach ensures the secure and stable functioning of chemical equipment pressure vessels, effectively extending their service life. Given the varied forms and causes of pressure vessel damage in chemical equipment, there is a need for innovative preventive measures and management strategies to fully realize the value of pressure vessel management in chemical equipment.
1.Characteristics of Accidents Involving Chemical Equipment and Pressure Vessels
Pressure vessels, classified as pressure-bearing equipment, encompass a range of hazardous equipment, including pressure pipes and boilers, posing risks to life safety. They can be categorized into internal and external pressure vessels based on pressure-bearing methods. Pressure vessels are further classified by pressure, temperature, and manufacturing methods, such as high pressure, low pressure, medium pressure, ultra-high pressure, low temperature, high temperature, normal temperature, forging, welding, and casting vessels. Despite varying classifications, safety and reliability control for chemical equipment pressure vessels are crucial. The accident characteristics of chemical equipment and pressure vessels are predominantly evident in the following aspects:
(1) High Risks
Chemical products exhibit characteristics like high temperature, high pressure, toxicity, flammability, and explosion susceptibility. Pressure vessels in the chemical industry face a heightened risk of fire, leakage, and explosion, surpassing risks in other industries. The reactive, toxic, and flammable nature of certain chemical raw materials is a major factor contributing to frequent accidents in chemical enterprises. Such accidents not only result in injuries or fatalities but also lead to substantial economic losses.
(2) Environmental Pollution
Chemical production involves raw materials, products, intermediates, and by-products with industrial toxicity and corrosiveness. Leakage into water or air, particularly untreated industrial substances, causes varying degrees of environmental pollution, resulting in economic losses and casualties. Serious accidents in chemical enterprises typically present challenges in governance and have a prolonged impact.
(3) Impacts on Equipment Operation
Chemical enterprises impose stringent requirements on industrial equipment operation. However, pressure vessels in chemical equipment often operate in harsh environments, influenced by factors like vibration and corrosive internal mediums. This can lead to quality issues, such as metal fatigue, directly affecting the normal operation of chemical equipment. Addressing this challenge is essential for chemical enterprises in ensuring the safe management of equipment use.
2.Types, Causes, and Features of Damage to Chemical Pressure Vessels
(1) Excessive Plastic Deformation
When the pressure load on a chemical pressure vessel surpasses the established limit, the vessel's wall gradually thins, reaching an unstable state. Over-shaping leads to deformation and potential rupture. If rupture is due to over-shaping, it results in a tearing effect, accompanied by fragments or none at all. The energy of the chemical equipment pressure vessel explosion directly determines the explosion opening's size.
(2) Excessive Elastic Deformation
Excessive elastic deformation occurs when a chemical pressure vessel is subjected to external force, causing instability. With increased external force, the vessel transitions to an unstable state.
(3) Large Strain Fatigue
Alternating stress induces local metal grain slip in areas like structural discontinuities, leading to micro-cracks. As cracks expand, fatigue-related damage becomes evident, primarily in areas of high stress and large strain.
(4) Corrosion Fatigue
The joint action of corrosion and fatigue results in local surface damage and metal fatigue cracks. The protective film on the metal surface is damaged, leading to surface corrosion. The corrosion pit's bottom becomes an active site, forming an anode in the corrosion battery, ultimately causing metal breakage.
(5) Stress Corrosion
Stress corrosion involves the combined action of tensile stress and metal corrosion medium, leading to a unique failure form. Corrosion reduces the metal's effective cross-sectional area, concentrates stress, and accelerates corrosion progression under prestressing.
(6) Brittle Fracture
Brittle fractures lack significant plastic deformation, occurring at low temperatures, often in thick-walled vessels made of medium and low strength or high-strength steel pressure vessels.
(7) Hydrogen Corrosion Cracking
Hydrogen corrosion occurs due to hydrogen molecules adsorbed on the steel surface during manufacturing and use. Hydrogen molecules decompose into ions or atoms, diffusing into steel, causing hydrogen corrosion and embrittlement.
(8) Creep
Under the influence of changing external temperature and stress, prolonged exposure leads to metal container wall damage. Creep is distinct from plastic deformation, with temperature and tensile stress being crucial factors. High temperature weakens metal material rigidity, and tensile stress degrades pressure vessel performance and quality, leading to damage.
3. Analysis of Pressure Vessel Damage
Pressure vessels pose a high risk of accidents, leading to shutdowns and corrosion. Direct causes of industrial equipment pressure vessel accidents include these incidents. However, indirect factors like mismanagement, incomplete technical records, insufficient safety production responsibility implementation, and inadequate safety production rectification monitoring contribute to vessel accidents. Besides basic investigation, understanding fracture states and container physical and chemical properties is crucial. To determine accident causes, conducting a destructive simulation test on the container is necessary. Simultaneously, perform technical inspections, accident investigations, and formulate targeted treatment and preventive measures.
1.Characteristics of Accidents Involving Chemical Equipment and Pressure Vessels
Pressure vessels, classified as pressure-bearing equipment, encompass a range of hazardous equipment, including pressure pipes and boilers, posing risks to life safety. They can be categorized into internal and external pressure vessels based on pressure-bearing methods. Pressure vessels are further classified by pressure, temperature, and manufacturing methods, such as high pressure, low pressure, medium pressure, ultra-high pressure, low temperature, high temperature, normal temperature, forging, welding, and casting vessels. Despite varying classifications, safety and reliability control for chemical equipment pressure vessels are crucial. The accident characteristics of chemical equipment and pressure vessels are predominantly evident in the following aspects:
(1) High Risks
Chemical products exhibit characteristics like high temperature, high pressure, toxicity, flammability, and explosion susceptibility. Pressure vessels in the chemical industry face a heightened risk of fire, leakage, and explosion, surpassing risks in other industries. The reactive, toxic, and flammable nature of certain chemical raw materials is a major factor contributing to frequent accidents in chemical enterprises. Such accidents not only result in injuries or fatalities but also lead to substantial economic losses.
(2) Environmental Pollution
Chemical production involves raw materials, products, intermediates, and by-products with industrial toxicity and corrosiveness. Leakage into water or air, particularly untreated industrial substances, causes varying degrees of environmental pollution, resulting in economic losses and casualties. Serious accidents in chemical enterprises typically present challenges in governance and have a prolonged impact.
(3) Impacts on Equipment Operation
Chemical enterprises impose stringent requirements on industrial equipment operation. However, pressure vessels in chemical equipment often operate in harsh environments, influenced by factors like vibration and corrosive internal mediums. This can lead to quality issues, such as metal fatigue, directly affecting the normal operation of chemical equipment. Addressing this challenge is essential for chemical enterprises in ensuring the safe management of equipment use.
2.Types, Causes, and Features of Damage to Chemical Pressure Vessels
(1) Excessive Plastic Deformation
When the pressure load on a chemical pressure vessel surpasses the established limit, the vessel's wall gradually thins, reaching an unstable state. Over-shaping leads to deformation and potential rupture. If rupture is due to over-shaping, it results in a tearing effect, accompanied by fragments or none at all. The energy of the chemical equipment pressure vessel explosion directly determines the explosion opening's size.
(2) Excessive Elastic Deformation
Excessive elastic deformation occurs when a chemical pressure vessel is subjected to external force, causing instability. With increased external force, the vessel transitions to an unstable state.
(3) Large Strain Fatigue
Alternating stress induces local metal grain slip in areas like structural discontinuities, leading to micro-cracks. As cracks expand, fatigue-related damage becomes evident, primarily in areas of high stress and large strain.
(4) Corrosion Fatigue
The joint action of corrosion and fatigue results in local surface damage and metal fatigue cracks. The protective film on the metal surface is damaged, leading to surface corrosion. The corrosion pit's bottom becomes an active site, forming an anode in the corrosion battery, ultimately causing metal breakage.
(5) Stress Corrosion
Stress corrosion involves the combined action of tensile stress and metal corrosion medium, leading to a unique failure form. Corrosion reduces the metal's effective cross-sectional area, concentrates stress, and accelerates corrosion progression under prestressing.
(6) Brittle Fracture
Brittle fractures lack significant plastic deformation, occurring at low temperatures, often in thick-walled vessels made of medium and low strength or high-strength steel pressure vessels.
(7) Hydrogen Corrosion Cracking
Hydrogen corrosion occurs due to hydrogen molecules adsorbed on the steel surface during manufacturing and use. Hydrogen molecules decompose into ions or atoms, diffusing into steel, causing hydrogen corrosion and embrittlement.
(8) Creep
Under the influence of changing external temperature and stress, prolonged exposure leads to metal container wall damage. Creep is distinct from plastic deformation, with temperature and tensile stress being crucial factors. High temperature weakens metal material rigidity, and tensile stress degrades pressure vessel performance and quality, leading to damage.
3. Analysis of Pressure Vessel Damage
Pressure vessels pose a high risk of accidents, leading to shutdowns and corrosion. Direct causes of industrial equipment pressure vessel accidents include these incidents. However, indirect factors like mismanagement, incomplete technical records, insufficient safety production responsibility implementation, and inadequate safety production rectification monitoring contribute to vessel accidents. Besides basic investigation, understanding fracture states and container physical and chemical properties is crucial. To determine accident causes, conducting a destructive simulation test on the container is necessary. Simultaneously, perform technical inspections, accident investigations, and formulate targeted treatment and preventive measures.
