According to the Regulations on the Safety Supervision of Special Equipment dated January 24, 2009, special equipment refers to boilers, pressure vessels (including gas cylinders, the same below), pressure pipelines, elevators, lifting machinery, passenger ropeways, large amusement facilities and special motor vehicles in the field (factory) that involve life safety and are more dangerous. (There are eight categories, including the materials used, the attached safety accessories, the safety protection devices and the facilities related to the safety protection devices).
**The special equipment safety supervision and management department is responsible for the safety inspection of special equipment in the country, and the department responsible for the safety supervision and management of special equipment at or above the county level shall carry out safety supervision of special equipment within its administrative area.
What are the characteristics of special equipment?
1.High Risk:Special equipment involves life safety and dangerous production and living fields, and once an accident occurs, it often causes personnel and property losses.
2.Wide range of equipment:There are many types of special equipment, including boilers, pressure vessels, elevators, lifting machinery, passenger ropeways, large amusement facilities, etc., and each equipment has its specific operation and management requirements.
A diagram outlining its classification.
3.Diverse use environments:The use environment of special equipment is diverse, including factories, public places, residential areas and other different use environments put forward different requirements for the operation and management of equipment.
4.Strong professionalism:The professionalism of the operation and management personnel has a direct impact on the safety and performance of the equipment.
This article mainly expounds the basic concept of pressure vessel:
First, the basic concept of pressure vessel
Broadly speaking, a pressure vessel is a cavity device designed to hold various materials (also known as media) while operating to maintain structural tightness, not communicate with the outside atmosphere, and at the same time be able to withstand internal and external pressure. This type of container ensures that the material is safely stored or transported under a specific pressure environment. Pressure vessel can also be defined as a device and equipment used to complete the process of reaction, heat and mass transfer, separation, storage and other processes in industrial production.
The pressure vessel needs to withstand more than 0The pressure is 1MPa (gauge pressure), so it has a closed form. According to the Regulations on Safety Supervision of Special Equipment, the pressure vessel also needs to meet certain design pressure, pressure and volume product and working temperature requirements. Pressure vessels are commonly used in the reaction of storage tanks and containing fluid chemicals, and have a risk factor, involving the production, storage, transportation and use of hazardous chemicals.
Second, the application of pressure vessels
Pressure vessels are commonly found in the industrial sector. In the production of the chemical industry, the pressure vessel is one of the indispensable equipment. Due to the large number of chemicals and high temperature and high pressure involved in chemical production, the safety performance requirements for pressure vessels are very high. At the same time, pressure vessels are used in food, pharmaceutical and other fields for storing materials, reaction, sterilization and other functions. Because the pressure vessel has to withstand a certain pressure and has a safety factor requirement, there are strict requirements for materials, welding, structure, etc., so it is necessary to strictly comply with relevant regulations and standards in design and use.
3. The structure, classification and main parameters of the pressure vessel
The pressure vessel is generally composed of a cylinder, a head, a sealing element, an opening and a pipe (such as a manhole, a hand hole, a sight hole hole, a material inlet and outlet pipe, a level gauge, a flow meter, a temperature measuring pipe, a safety valve, etc.), a bearing, and other internal components.
Classification by wall thickness:It can be divided into thin-walled, medium-thick-walled, thick-walled and other containers, and the wall thickness determines the safety performance and service life under a certain pressure.
Classification by compression:It can be divided into internal pressure and external pressure, and the internal pressure vessel can be divided into different pressure levels such as ultra-high pressure, high pressure, medium pressure, and low pressure according to the pressure capacity.
Classification by appearance geometry:It can be divided into cylindrical, spherical, rectangular and other shapes, and cylindrical is more common.
Classification according to the materials used in manufacturing:It can be divided into steel, non-ferrous metal, non-metal and other pressure vessels.
Classified by installation method:It can be divided into fixed type and mobile type, etc., and can also be subdivided according to the different installation positions.
Classified according to the principle of action in the process:It can be divided into reaction, heat exchange, separation, storage, etc., and pressure vessels can play different roles in different process requirements.
Classification by operating temperature:It can be divided into normal temperature container (T>-20 150 °C), high temperature container (T 450 °C), low temperature container (T -20 °C), etc.
There are many classification methods of pressure vessels, and these classification methods help us understand and recognize the characteristics of pressure vessels, but in the process of practical design and manufacturing, they are generally divided according to the use, production process, equipment size, use environment and other factors of pressure vessels. So there will be specific parameters involved.
The "Regulations for the Safety and Technical Supervision of Pressure Vessels" issued by the State Bureau of Quality and Technical Supervision (Quality and Technical Supervision Bureau Fa [1999] No. 154) is based on the operating pressure of the pressure vessel, the degree of hazard of the medium, the function of the vessel, the structural characteristics of the material and the safety performance of the vesselThe overall degree of impactetc., the pressure vessels are divided into the following three categories:
1.Class I Pressure Vessels:Low-pressure vessels, except for the provisions for Class II and Class III pressure vessels.
2.Class II Pressure Vessel:This includes one of the following (in addition to the provisions for Class III pressure vessels).
1) Medium pressure vessel;
2) Low-pressure containers (only for media with extreme and high toxicity levels);
3) Low-pressure reaction vessels and low-pressure storage vessels (only applicable to flammable media or mediums with moderate toxicity);
4) Low-pressure shell-and-tube heat recovery boiler;
5) Low-pressure glass-lined pressure vessel.
3.Class III Pressure Vessel:This includes one of the following:
1) High-pressure vessels;
2) Medium-pressure vessels (only for media with extreme and high toxicity levels);
3) Medium-pressure storage container (only applicable to flammable or moderately toxic media, and the product of pressure and volume (PV) is greater than or equal to 10MPa·m3);
4) Medium-pressure reaction vessel (only suitable for flammable or moderately toxic media, and PV greater than or equal to 0.)5mpa·m3）；
5) Low-pressure container (only for media with extreme and high toxicity and PV greater than or equal to 0.)2mpa·m3）。
These classification standards take into account factors such as operating pressure, medium hazard degree, vessel function, structural characteristic materials and the degree of comprehensive influence on the safety performance of the vessel to ensure the safe use of pressure vessels.
Fourth, the main parameters of the pressure vessel
Maximum working pressure:The highest gauge pressure that a pressure vessel may produce during normal operation.
Design Pressure:The pressure vessel is used to determine the pressure of the vessel shell wall at the corresponding design temperature, calculating the wall thickness and the size of its elements. The design pressure must not be lower than the maximum working pressure.
Working Pressure:The gauge pressure generated by a pressure vessel under conditions that meet the requirements of the process.
Test pressure:The pressure on the top of the pressure vessel during the pressure test.
Design Temperature:The metal temperature of the elements set by the pressure vessel under normal operating conditions. The design temperature should be the highest or lowest value of the design temperature of the housing.
Test Temperature:The metal temperature of the shell of the pressure vessel during the pressure test.
Calculate thickness:The thickness of each part of the pressure vessel element is calculated according to the formula.
Design thickness:Calculate the sum of the thickness and corrosion margin.
Nominal thickness:The design thickness is rounded upwards to the thickness of the standard specification of the steel after the negative deviation of the steel is added.
Effective thickness:Nominal thickness minus the negative deviation and corrosion margin of the steel.
Measured thickness:The actual thickness of the pressure vessel measured by the thickness gauge during the inspection.
Outer diameter:The outer diameter of a cylindrical, spherical pressure vessel.
Inner Diameter:The inner diameter of a cylindrical, spherical pressure vessel.
Representation of container specifications:Inner diameter x wall thickness x length (height) in mm, represented by symbols.
5. Briefly understand the safety accessories of pressure vessels
Safe Attachment isIn order to prevent overheating, overpressure and overload of the containerand other situations in the event of an accident, and a safety device installed on the equipment. Common ones include safety valves, rupture discs, explosion-proof caps, pressure gauges, level gauges, etc.
6. Materials for the manufacture of pressure vessels
The vast majority of pressure vessels are made of steel, and the more commonly used ones are as follows:
1.Carbon Steel:
Q235-A: Ordinary carbon structural steel, suitable for low-pressure vessels.
20g: for boilers and medium-pressure vessels, suitable for medium temperature conditions.
16mnr: low-alloy container steel, suitable for manufacturing medium and low pressure containers.
345R: Low alloy steel, suitable for medium to low temperature and general pressure conditions.
2.Stainless steel:
304 304L: Commonly used stainless steel, with good corrosion resistance, suitable for general pressure vessel manufacturing.
316 316L: Stainless steel with better corrosion resistance, suitable for pressure vessels with highly corrosive media.
321 321H: Stainless steel with high temperature resistance, suitable for pressure vessels in high temperature environments.
904L: Stainless steel with good acid resistance, suitable for strong acid corrosion environments.
Duplex stainless steel: such as etc., has good corrosion resistance and strength, and is often used in pressure vessels under special working conditions.
3.High alloy steels:
15CRMOR: suitable for high temperature and high pressure vessels, such as boilers, reactors, etc.
12Cr2MO1R: High temperature resistant, corrosion resistant alloy steel for high temperature pressure vessels.
A387G2: Chromium-molybdenum alloy steel, suitable for high temperature and high pressure vessels.
The selection of manufacturing materials mentioned above needs to consider various factors, and different pressure vessels may have differences in material selection, and optimization decisions need to be made according to the specific situation. The selection of general materials needs to consider the following factors: strength and toughness, corrosion resistance, temperature adaptability, process performance and economy.
7. Laws and regulations related to pressure vessel management
According to Order No. 373 "Regulations on the Safety Supervision of Special Equipment" and the "Regulations on the Safety and Technical Supervision of Pressure Vessels" issued by the Bureau of Quality and Technical Supervision, units engaged in pressure vessel-related work must comply with the following requirements:
1.Design of pressure vessels:The design unit of the pressure vessel must obtain the license of the special equipment safety supervision and management department, and can only be manufactured after being identified by the approved inspection and testing institution. The design unit must also have appropriate designers, design reviewers, and a sound management system and responsibility system.
2.Manufacturing, installation and transformation of pressure vessels:Units engaged in the manufacture, installation and transformation of pressure vessels and manufacturing units of related pressure piping components must obtain the license of the special equipment safety supervision and management department. At the same time, these units must also have appropriate professional and technical personnel, skilled workers, production conditions and testing methods, as well as a sound quality management system and responsibility system.
3.Periodic inspection of pressure vessels:Periodic inspection is to inspect and test the various pressure-bearing parts and safety devices of the container during use. According to the actual situation, the safety status of the pressure vessel is rated.