Some standard content:
Setting and Selection of Safety Valves
HG/T20570.2--95
Compiled by: China Huanqiu Chemical Engineering Corporation Approved by: Ministry of Chemical Industry
Implementation Date: September 1, 1996 Prepared by:
Shang Changyou of China Huanqiu Chemical Engineering Corporation
Reviewed by:
Yang Yi of China Huanqiu Chemical Engineering Corporation
Feng Shuyuan and Gong Renwei of the Process System Design Technology Center of the Ministry of Chemical Industry
Scope of Application
1.0.1 This regulation is only applicable to the setting and calculation of safety valves for overpressure protection on pressure vessels with a pressure greater than 0.2MPa in chemical production equipment, and does not include ultra-high pressure systems with a pressure greater than 100MPa. It is applicable to pressure vessels within the above range in chemical production equipment Safety valves used on pressure vessels and pipelines are not suitable for safety valves used on pressure vessels in other industries, such as various types of tank trucks, various types of gas cylinders, boiler systems, non-metallic material containers, as well as the nuclear industry, electric power industry, etc. 1.0.2 The calculation method is quoted from the "Regulations on Technical Supervision of Pressure Vessel Safety" and API-520 (see Section 2.3). When using this regulation, the same specification should be used to calculate the discharge volume and discharge area. 21
2.0.1 Safety valve
2 Noun
Safety valve acted by a spring or controlled by a pilot valve. When the static pressure at the inlet exceeds the set pressure, the valve disc rises to discharge the overpressure of the protected system. When the pressure drops to the return pressure, the safety relief valve can automatically close. 2.0.2 Pilot valve
Auxiliary pressure relief valve that controls the action of the main valve Release valve. 2.0.3 Full-open safety valve
When the static pressure at the inlet of the safety valve reaches its set pressure, the valve disc rises rapidly to the maximum height to discharge the overpressure material to the maximum extent. Generally used for compressible fluids. The maximum rise height of the valve disc is not less than 1/4 of the throat diameter. 2.0.4 Micro-open safety valve
When the static pressure at the inlet of the safety valve reaches its set pressure, the valve disc position rises proportionally with the increase in the inlet pressure, minimizing the material to be discharged. Generally used for incompressible fluids. The maximum rise height of the valve disc is not less than 1/20~~1/40 of the throat diameter. 2.0.5 Spring-loaded safety valve
A safety valve acted by a spring. Its set pressure is controlled by the spring, and its action characteristics are affected by the back pressure. 2.0.6 Back pressure balanced safety valve
Safety valve acted by a spring. Its set pressure is controlled by a spring, and a piston or bellows is used to reduce the effect of back pressure on its operating performance.
2.0.7 Pilot valve type safety valve
Safety valve controlled by a pilot valve. Its set pressure is controlled by a pilot valve, and its operating performance is basically not affected by back pressure. When the pilot valve fails, the main valve can still open automatically without exceeding the relief pressure and discharge the entire rated discharge volume. 2.0.8 Main safety valve
The main safety valve is the main safety relief device of the protected system, and its discharge area is based on the discharge volume under the maximum possible accident condition.
2.0.9 Auxiliary safety valve
Auxiliary safety valve (sometimes more than one) is an auxiliary device of the main safety valve, providing additional discharge area in addition to the main safety valve. It is used for overpressure relief under non-maximum possible accident conditions. 2.0.10 Actual discharge area
The minimum flow area of the fluid through the safety valve. 2.0.11 Effective discharge area (minimum discharge area) 22
The discharge area calculated by formula or chart. The effective discharge area should be smaller than the actual discharge area. 2.0.12 Throat area
The cross-sectional area at the minimum diameter of the nozzle of the safety valve. 2.0.13 Annular area
The cylindrical area between the valve and the valve seat of the safety valve. 2.0.14 Maximum working pressure
refers to the maximum pressure that may be reached at the top of the container under normal working conditions. See the provisions of "Determination of design pressure and temperature of equipment and piping system" (HG/T20570.1-95). 2.0.15 Design pressure
refers to the maximum pressure set at the top of the container, which should not be less than the set pressure (opening pressure) of the safety valve. 2.0.16 Set pressure of safety valve
When the static pressure at the inlet of the safety valve reaches this value, the safety valve will operate. The set pressure is required to be no greater than the lowest design pressure in the protected system.
2.0.17 Opening pressure of safety valve (set pressure) The pressure when the valve disc of the safety valve begins to rise and the material flows out continuously. The value is the same as the set pressure. 2.0.18 Back pressure of safety valve
The pressure acting on the outlet of the safety valve. Back pressure is divided into static back pressure and dynamic back pressure. Static back pressure refers to the pressure at the outlet of the valve when the safety valve is not tripped; dynamic back pressure refers to the friction pressure drop caused by the flow of fluid after the safety valve is tripped.
2.0.19 Overpressure of safety valve
The part of the pressure at the inlet of the safety valve that exceeds the set pressure during the discharge process. Usually expressed as a percentage. 2.0.20
Relief pressure of safety valve
The pressure at the inlet of the safety valve after the valve core of the safety valve rises to the maximum height. The relief pressure is equal to the set pressure plus the overpressure. 2.0.21 Safety valve return pressure
After the safety valve is tripped, as the pressure in the protected system decreases, the valve core returns to the valve seat. 2.0.22 Maximum allowable working pressure
refers to the maximum gauge pressure allowed to be borne by the top of the container at the design temperature. The pressure is calculated based on the effective thickness of the pressure-bearing components of the container, and the minimum value is taken. 23
Referenced standards
3.0.1 "Regulations on Safety Technical Supervision of Pressure Vessels" (issued by the Ministry of Labor, implemented on January 1, 1991) 3.0.2 GB150-89 "Steel Pressure Vessels" 3.0.3 API-520 "Sizing Selection and Installation of Pressure--Relieving Devices in Refineries" 1992. (American Petroleum Institute Standard) 3.0.4 API-526 "Flanged Steel Safety-Relief Valves" (American Petroleum Institute Standard) 24
4.0.1 Pressure Relationship Table
See Table 4.0.1 for pressure relationships.
Pressure relationship table
Pressure relationship table related to safety valve and containerContainer
Design pressure (or maximum allowable working pressure
Pressure percentage
93%~97%
Safety valve
Maximum relief pressure of fire safety valve
Maximum relief pressure of auxiliary safety valve for non-fire Maximum relief pressure of non-fire main safety valve, maximum setting pressure of auxiliary safety valve for fire
Maximum setting pressure of auxiliary safety valve for non-fire Maximum setting pressure of main safety valve
Reseat Pressure
Table 4.0.1 shows the proportional relationship between the maximum relief pressure and the maximum set pressure of the safety valve set in the protected system under different conditions and the design pressure (or maximum allowable working pressure) of the protected container. 25
5 Setting of safety valve
5.0.1 Safety valves are suitable for clean, particle-free, low-viscosity fluids. Where safety pressure relief devices must be installed but safety valves are not suitable, bursting discs should be installed or safety valves and bursting discs should be used in series. 5.0.2 Safety valves must be installed in containers that fall into any of the following situations: 5.0.2. 1
Independent pressure system (separated from other systems by a shut-off valve). This system refers to the full gas phase, full liquid phase or gas phase connection;
5.0.2.2 The occasion where there is no safety valve at the source of the pressure material of the container; 5.0.2.3 The container and pipeline whose design pressure is less than the pressure at the pressure source; The outlet pipeline of the volumetric pump and compressor
Containers with overpressure due to the accumulation of non-condensable gas: 5.0.2.5
If a shut-off valve or control valve is installed on the outlet pipeline of the heating furnace, a safety valve should be installed upstream of the valve. 5.0.2.7
Overpressure caused by process accidents, automatic control accidents, power accidents, fire accidents and public engineering accidents ;
5.0.2.8 The part where the liquid expands due to the closing of the valves at both ends; 5.0.2.9
Steam outlet pipe of condensing turbine:
In some cases, due to the leakage of the pump outlet check valve, a safety valve is installed on the pump inlet pipe. 5.0.2.10
Other places where safety valves should be installed.
6 Choice of safety valve type
When discharging gas or steam, a full-open safety valve should be selected. 6.0.1
6.0.2When discharging liquid, a full-open or micro-open safety valve should be selected. When discharging water vapor or air, a safety valve with a wrench can be selected. 6.0.3
6.0.4For safety valves for gases with set pressure greater than 3MPa and temperature exceeding 235℃, use safety valves with heat sinks to prevent the discharged medium from directly eroding the spring. If the discharged medium is allowed to leak into the atmosphere, use an open bonnet safety valve. If it is not allowed to leak into the atmosphere, use a closed bonnet safety valve.
For highly toxic, highly corrosive, and extremely dangerous media, use a bellows safety valve. 6.0.6
For high back pressure, use a back pressure balanced safety valve or a pilot valve controlled safety valve. 6.0.7
6.0.8In some important occasions, it is sometimes necessary to install two safety valves as backup for each other. The inlet and outlet shut-off valves of the two safety valves should be mechanically interlocked to ensure that the required discharge area of the container can be met at any time (including during maintenance and overhaul).
7.0.1 Misclosed valves
7 Calculation of discharge volume under various accident conditions
When the outlet valve is closed and the inlet valve is not closed, the discharge volume is the maximum normal flow of the closed pipeline. 7.0.1.1
7.0.1.2 When the shut-off valves at both ends of the pipeline are closed, the discharge volume is the expansion volume of the closed liquid. The inlet of this type of safety valve is generally not larger than DN25. However, for large-diameter, long-distance pipelines and pipelines with liquefied gas as the material, the liquid expansion volume is calculated according to formula (7.0.1).
7.0.1.3 Cold side of the heat exchanger When the inlet and outlet valves are closed, the discharge volume is calculated based on the heat input for normal operation. The calculation formula is shown in formula (7.0.1).
7.0.1.4 For a container filled with liquid, when all the inlet and outlet valves are closed, the discharge volume is calculated based on the heat input for normal operation. Calculate the discharge volume under liquid expansion conditions according to formula (7.0.1): VB·H/(GC.)
V—volume discharge flow, m/h;
B——volume expansion coefficient, l/℃,
H-maximum heat transfer under normal working conditions, kJ/h; G—liquid phase density, kg/m
Cp—constant pressure specific heat, kJ/(kg℃).
7.0.2 Circulating water failure
7.0.2.1 Taking circulating water as For the top condenser of the tower using circulating water as the refrigerant, when the circulating water fails (water outage), the discharge volume of the safety valve installed on the top of the tower is the maximum amount of steam entering the condenser under normal working conditions. 7.0.2.2 For other heat exchangers using circulating water as the refrigerant, when the circulating water fails (water outage), the scope of impact should be carefully analyzed to determine the discharge volume.
7.0.3 Power failure
7.0.3.1 When the power supply is cut off, the top reflux pump driven by the motor and the tower side line reflux pump will stop rotating, and the discharge volume of the safety valve installed on the top of the tower is the amount of steam entering the top condenser under the accident condition. 7.0.3.2 When the top condenser of the tower is an air cooler without louvers, in the event of a power outage, the discharge volume of the safety valve installed on the top of the tower is the amount of steam entering the condenser under normal working conditions. 75% of the maximum steam volume. 7.0.3.3 When the power supply is cut off, the impact range of the power outage should be carefully analyzed, such as the driving mechanism of the pump, compressor, fan, valve, etc., to determine the sufficient discharge volume. 7.0.4 Accumulation of non-condensable gas
7.0.4.1 If there is a lot of non-condensable gas that cannot be discharged in the tower top condenser, the discharge volume of the safety valve installed at the top of the tower is the same as that specified in 7.0.2.
7.0.4.2 In other occasions where non-condensable gas accumulates, the impact range should be analyzed to determine the discharge volume. 7.0.5 Control valve failure
7.0.5.1 If the control valve installed at the outlet of the equipment is in the fully closed position when a failure occurs, the discharge volume of the safety valve installed is the maximum normal flow through this control valve. 7.0.5.2 If the control valve installed at the inlet of the equipment is in the fully open position when a fault occurs: (1) For gas phase pipelines, if the design pressure on the low-pressure side is less than 2/3 of the design pressure on the high-pressure side, the discharge volume of the safety valve shall be calculated according to formula (7.0.5): W = 3171.3 (Cvi - Cv2) Ph (G/T) 1/2 Where
W is the mass discharge flow rate, kg/h;
Cvi is the Cv value of the control valve;
Cv2 is the Cv value at the minimum flow rate of the control valve, Ph is the working pressure on the high-pressure side, MPa;
Gg is the gas phase density, kg/m
T is the discharge temperature, K.
If the material on the high-pressure side may transfer heat to the low-pressure side, the influence of heat transfer must be considered. (7.0.5)
（2）For liquid phase pipelines, the discharge volume of the safety valve is the difference between the maximum flow rate of the control valve and the normal flow rate, and it is necessary to estimate whether the material on the high-pressure side flashes. 7.0.6 Excessive heat input
Under conditions such as the control valve on the heat medium side of the heat exchanger failing to fully open, the shut-off valve opening by mistake, the heating jacket of the equipment, and the shut-off valve opening by mistake, the gas evaporation or liquid expansion caused by excessive heat input is used as the calculation. 7.0.7 Volatile materials enter the high-temperature system
Under conditions such as light hydrocarbons accidentally entering hot oil and water accidentally entering hot oil, a large amount of steam is generated, causing the pressure in the container7.0.7.1
to rise rapidly.
7.0.7.2Since the discharge volume under this accident condition cannot be determined and the pressure rises very rapidly, it is inappropriate to install a safety valve and a bursting disc should be installed. 7.0.7.3The protection measures for this condition are to ensure that such accidents are avoided. 29
7.0.8 Heat exchanger tube rupture
7.0.8.1 If the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, it should be considered as an accident condition.
7.0.8.2 According to the conditions of 7.0.8.1, the discharge volume of the safety valve is compared with the result calculated by formula (7.0.8) and the normal flow on the high-pressure side, and the smaller value of the two is taken. 7.0.8.3 The discharge volume when the heat exchanger tube ruptures W=5.6·d2.(GXAP)1/2
W—mass discharge flow, kg/h;
d——tube inner diameter, mm;
G liquid phase density, kg/m;
AP-pressure difference between the high-pressure side (tube side) and the low-pressure side (shell side), MPa. This formula is applicable to high-pressure fluid in liquid phase. 7.0.9 Out of control of chemical reaction
7.0.9.1 For exothermic chemical reactions, if the automatic control of temperature, pressure and flow fails, the chemical reaction will be out of control and form a "flying temperature". At this time, a large amount of heat will be generated, causing the material to evaporate rapidly and form an overpressure. In this type of accident condition, the installation of a safety valve cannot meet the requirements in terms of reaction time or discharge rate, and a bursting disc should be installed.
7.0.9.2 If the patent owner can provide an accurate chemical reaction kinetic correlation formula to calculate the discharge volume under the accident condition, a safety valve can be installed with the consent of the patent owner and the construction party. 7.0.10 External fire
7.0.10.1 This regulation applies to containers containing liquids exposed to external fires. 7.0.10.2 Wetted area of the container (A)
The area below the liquid surface in the container is collectively referred to as the wetted area. The heat transmitted by the external flame vaporizes the material in the container through the wetted area. The wetted area of different types of equipment is calculated as follows: (1) Horizontal and vertical containers: Compare the surface area of the container within a height range of 7.5m from the ground or 7.5m above the platform where a large flame can be formed with the surface area below the highest normal liquid level, and take the smaller value. a. For equipment with elliptical heads, the total surface area is: A = Yuan D (L + 0.3XD) || tt || (7.0.10-1)3 When the inlet and outlet valves on the cold side of the heat exchanger are closed, the discharge volume is calculated based on the heat input for normal operation. The calculation formula is shown in formula (7.0.1).
7.0.1.4 When the inlet and outlet valves of a container filled with liquid are all closed, the discharge volume is calculated based on the heat input for normal operation. Calculate the discharge volume under liquid expansion conditions according to formula (7.0.1): VB·H/(GC.)
V—volume discharge flow, m/h;
B——volume expansion coefficient, l/℃,
H-maximum heat transfer under normal working conditions, kJ/h;G—liquid phase density, kg/m
Cp—constant pressure specific heat, kJ/(kg℃).
7.0.2 Circulating water failure
7.0.2.1 For the tower top condenser using circulating water as the refrigerant, when the circulating water fails (water outage), the discharge volume of the safety valve installed at the tower top shall be the maximum amount of steam entering the condenser under normal working conditions. 7.0.2.2 For other heat exchangers using circulating water as the refrigerant, when the circulating water fails (water outage), the scope of influence shall be carefully analyzed to determine the discharge volume.
7.0.3 Power failure
7.0.3.1 When the power supply is stopped, the tower top reflux pump driven by the motor and the tower side line reflux pump will stop rotating, and the discharge volume of the safety valve installed at the tower top shall be the amount of steam entering the tower top condenser under the accident condition. 7.0.3.2 When the tower top condenser is an air cooler without shutters, in the case of power outage, the discharge volume of the safety valve installed at the tower top shall be 75% of the maximum amount of steam entering the condenser under normal working conditions. 7.0.3.3 When the power supply is cut off, the impact range of the power outage should be carefully analyzed, such as the driving mechanism of pumps, compressors, fans, valves, etc., to determine sufficient discharge volume. 7.0.4 Accumulation of non-condensable gas
7.0.4.1 If there is a lot of non-condensable gas that cannot be discharged in the tower top condenser, the discharge volume of the safety valve installed at the top of the tower is the same as that specified in 7.0.2.
7.0.4.2 In other situations where non-condensable gas accumulates, its impact range should be analyzed to determine the discharge volume. 7.0.5 Control valve failure
7.0.5.1 If the control valve installed at the outlet of the equipment is in the fully closed position when a failure occurs, the discharge volume of the safety valve installed is the maximum normal flow through this control valve. 7.0.5.2 If the control valve installed at the inlet of the equipment is in the fully open position when a fault occurs: (1) For gas phase pipelines, if the design pressure on the low-pressure side is less than 2/3 of the design pressure on the high-pressure side, the discharge volume of the safety valve shall be calculated according to formula (7.0.5): W = 3171.3 (Cvi - Cv2) Ph (G/T) 1/2 Where
W is the mass discharge flow rate, kg/h;
Cvi is the Cv value of the control valve;
Cv2 is the Cv value at the minimum flow rate of the control valve, Ph is the working pressure on the high-pressure side, MPa;
Gg is the gas phase density, kg/m
T is the discharge temperature, K.
If the material on the high-pressure side may transfer heat to the low-pressure side, the influence of heat transfer must be considered. (7.0.5)
（2）For liquid phase pipelines, the discharge volume of the safety valve is the difference between the maximum flow rate of the control valve and the normal flow rate, and it is necessary to estimate whether the material on the high-pressure side flashes. 7.0.6 Excessive heat input
Under conditions such as the control valve on the heat medium side of the heat exchanger failing to fully open, the shut-off valve opening by mistake, the heating jacket of the equipment, and the shut-off valve opening by mistake, the gas evaporation or liquid expansion caused by excessive heat input is used as the calculation. 7.0.7 Volatile materials enter the high-temperature system
Under conditions such as light hydrocarbons accidentally entering hot oil and water accidentally entering hot oil, a large amount of steam is generated, causing the pressure in the container7.0.7.1
to rise rapidly.
7.0.7.2Since the discharge volume under this accident condition cannot be determined and the pressure rises very rapidly, it is inappropriate to install a safety valve and a bursting disc should be installed. 7.0.7.3The protection measures for this condition are to ensure that such accidents are avoided. 29
7.0.8 Heat exchanger tube rupture
7.0.8.1 If the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, it should be considered as an accident condition.
7.0.8.2 According to the conditions of 7.0.8.1, the discharge volume of the safety valve is compared with the result calculated by formula (7.0.8) and the normal flow on the high-pressure side, and the smaller value of the two is taken. 7.0.8.3 The discharge volume when the heat exchanger tube ruptures W=5.6·d2.(GXAP)1/2
W—mass discharge flow, kg/h;
d——tube inner diameter, mm;
G liquid phase density, kg/m;
AP-pressure difference between the high-pressure side (tube side) and the low-pressure side (shell side), MPa. This formula is applicable to high-pressure fluid in liquid phase. 7.0.9 Out of control of chemical reaction
7.0.9.1 For exothermic chemical reactions, if the automatic control of temperature, pressure and flow fails, the chemical reaction will be out of control and form a "flying temperature". At this time, a large amount of heat will be generated, causing the material to evaporate rapidly and form an overpressure. In this type of accident condition, the installation of a safety valve cannot meet the requirements in terms of reaction time or discharge rate, and a bursting disc should be installed.
7.0.9.2 If the patent owner can provide an accurate chemical reaction kinetic correlation formula to calculate the discharge volume under the accident condition, a safety valve can be installed with the consent of the patent owner and the construction party. 7.0.10 External fire
7.0.10.1 This regulation applies to containers containing liquids exposed to external fires. 7.0.10.2 Wetted area of the container (A)
The area below the liquid surface in the container is collectively referred to as the wetted area. The heat transmitted by the external flame vaporizes the material in the container through the wetted area. The wetted area of different types of equipment is calculated as follows: (1) Horizontal and vertical containers: Compare the surface area of the container within a height range of 7.5m from the ground or 7.5m above the platform where a large flame can be formed with the surface area below the highest normal liquid level, and take the smaller value. a. For equipment with elliptical heads, the total surface area is: A = Yuan D (L + 0.3XD) || tt || (7.0.10-1)3 When the inlet and outlet valves on the cold side of the heat exchanger are closed, the discharge volume is calculated based on the heat input for normal operation. The calculation formula is shown in formula (7.0.1).
7.0.1.4 When the inlet and outlet valves of a container filled with liquid are all closed, the discharge volume is calculated based on the heat input for normal operation. Calculate the discharge volume under liquid expansion conditions according to formula (7.0.1): VB·H/(GC.)
V—volume discharge flow, m/h;
B——volume expansion coefficient, l/℃,
H-maximum heat transfer under normal working conditions, kJ/h;G—liquid phase density, kg/m
Cp—constant pressure specific heat, kJ/(kg℃).
7.0.2 Circulating water failure
7.0.2.1 For the tower top condenser using circulating water as the refrigerant, when the circulating water fails (water outage), the discharge volume of the safety valve installed at the tower top shall be the maximum amount of steam entering the condenser under normal working conditions. 7.0.2.2 For other heat exchangers using circulating water as the refrigerant, when the circulating water fails (water outage), the scope of influence shall be carefully analyzed to determine the discharge volume.
7.0.3 Power failure
7.0.3.1 When the power supply is stopped, the tower top reflux pump driven by the motor and the tower side line reflux pump will stop rotating, and the discharge volume of the safety valve installed at the tower top shall be the amount of steam entering the tower top condenser under the accident condition. 7.0.3.2 When the tower top condenser is an air cooler without shutters, in the case of power outage, the discharge volume of the safety valve installed at the tower top shall be 75% of the maximum amount of steam entering the condenser under normal working conditions. 7.0.3.3 When the power supply is cut off, the impact range of the power outage should be carefully analyzed, such as the driving mechanism of pumps, compressors, fans, valves, etc., to determine sufficient discharge volume. 7.0.4 Accumulation of non-condensable gas
7.0.4.1 If there is a lot of non-condensable gas that cannot be discharged in the tower top condenser, the discharge volume of the safety valve installed at the top of the tower is the same as that specified in 7.0.2.
7.0.4.2 In other situations where non-condensable gas accumulates, its impact range should be analyzed to determine the discharge volume. 7.0.5 Control valve failure
7.0.5.1 If the control valve installed at the outlet of the equipment is in the fully closed position when a failure occurs, the discharge volume of the safety valve installed is the maximum normal flow through this control valve. 7.0.5.2 If the control valve installed at the inlet of the equipment is in the fully open position when a fault occurs: (1) For gas phase pipelines, if the design pressure on the low-pressure side is less than 2/3 of the design pressure on the high-pressure side, the discharge volume of the safety valve shall be calculated according to formula (7.0.5): W = 3171.3 (Cvi - Cv2) Ph (G/T) 1/2 Where
W is the mass discharge flow rate, kg/h;
Cvi is the Cv value of the control valve;
Cv2 is the Cv value at the minimum flow rate of the control valve, Ph is the working pressure on the high-pressure side, MPa;
Gg is the gas phase density, kg/m
T is the discharge temperature, K.
If the material on the high-pressure side may transfer heat to the low-pressure side, the influence of heat transfer must be considered. (7.0.5)
（2）For liquid phase pipelines, the discharge volume of the safety valve is the difference between the maximum flow rate of the control valve and the normal flow rate, and it is necessary to estimate whether the material on the high-pressure side flashes. 7.0.6 Excessive heat input
Under conditions such as the control valve on the heat medium side of the heat exchanger failing to fully open, the shut-off valve opening by mistake, the heating jacket of the equipment, and the shut-off valve opening by mistake, the gas evaporation or liquid expansion caused by excessive heat input is used as the calculation. 7.0.7 Volatile materials enter the high-temperature system
Under conditions such as light hydrocarbons accidentally entering hot oil and water accidentally entering hot oil, a large amount of steam is generated, causing the pressure in the container7.0.7.1
to rise rapidly.
7.0.7.2Since the discharge volume under this accident condition cannot be determined and the pressure rises very rapidly, it is inappropriate to install a safety valve and a bursting disc should be installed. 7.0.7.3The protection measures for this condition are to ensure that such accidents are avoided. 29
7.0.8 Heat exchanger tube rupture
7.0.8.1 If the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, it should be considered as an accident condition.
7.0.8.2 According to the conditions of 7.0.8.1, the discharge volume of the safety valve is compared with the result calculated by formula (7.0.8) and the normal flow on the high-pressure side, and the smaller value of the two is taken. 7.0.8.3 The discharge volume when the heat exchanger tube ruptures W=5.6·d2.(GXAP)1/2
W—mass discharge flow, kg/h;
d——tube inner diameter, mm;
G liquid phase density, kg/m;
AP-pressure difference between the high-pressure side (tube side) and the low-pressure side (shell side), MPa. This formula is applicable to high-pressure fluid in liquid phase. 7.0.9 Out of control of chemical reaction
7.0.9.1 For exothermic chemical reactions, if the automatic control of temperature, pressure and flow fails, the chemical reaction will be out of control and form a "flying temperature". At this time, a large amount of heat will be generated, causing the material to evaporate rapidly and form an overpressure. In this type of accident condition, the installation of a safety valve cannot meet the requirements in terms of reaction time or discharge rate, and a bursting disc should be installed.
7.0.9.2 If the patent owner can provide an accurate chemical reaction kinetic correlation formula to calculate the discharge volume under the accident condition, a safety valve can be installed with the consent of the patent owner and the construction party. 7.0.10 External fire
7.0.10.1 This regulation applies to containers containing liquids exposed to external fires. 7.0.10.2 Wetted area of the container (A)
The area below the liquid surface in the container is collectively referred to as the wetted area. The heat transmitted by the external flame vaporizes the material in the container through the wetted area. The wetted area of different types of equipment is calculated as follows: (1) Horizontal and vertical containers: Compare the surface area of the container within a height range of 7.5m from the ground or 7.5m above the platform where a large flame can be formed with the surface area below the highest normal liquid level, and take the smaller value. a. For equipment with elliptical heads, the total surface area is: A = Yuan D (L + 0.3XD) || tt || (7.0.10-1)3(Cvi—Cv2)Ph(G/T)1/2Wherein
W is the mass discharge flow rate, kg/h;
Cvi is the Cv value of the control valve;
Cv2 is the Cv value at the minimum flow rate of the control valve, Ph is the working pressure on the high-pressure side, MPa;
Gg is the gas phase density, kg/m
T is the discharge temperature, K.
If the material on the high-pressure side is likely to transfer heat to the low-pressure side, the influence of heat transfer must be considered. (7.0.5)
（2）For liquid phase pipelines, the discharge volume of the safety valve is the difference between the maximum flow rate of the control valve and the normal flow rate, and it is necessary to estimate whether the material on the high-pressure side flashes. 7.0.6 Excessive heat input
Under conditions such as the control valve on the heat medium side of the heat exchanger failing to fully open, the shut-off valve opening by mistake, the heating jacket of the equipment, and the shut-off valve opening by mistake, the gas evaporation or liquid expansion caused by excessive heat input is used as the calculation. 7.0.7 Volatile materials enter the high-temperature system
Under conditions such as light hydrocarbons accidentally entering hot oil and water accidentally entering hot oil, a large amount of steam is generated, causing the pressure in the container7.0.7.1
to rise rapidly.
7.0.7.2Since the discharge volume under this accident condition cannot be determined and the pressure rises very rapidly, it is inappropriate to install a safety valve and a bursting disc should be installed. 7.0.7.3The protection measures for this condition are to ensure that such accidents are avoided. 29
7.0.8 Heat exchanger tube rupture
7.0.8.1 If the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, it should be considered as an accident condition.
7.0.8.2 According to the conditions of 7.0.8.1, the discharge volume of the safety valve is compared with the result calculated by formula (7.0.8) and the normal flow on the high-pressure side, and the smaller value of the two is taken. 7.0.8.3 The discharge volume when the heat exchanger tube ruptures W=5.6·d2.(GXAP)1/2
W—mass discharge flow, kg/h;
d——tube inner diameter, mm;
G liquid phase density, kg/m;
AP-pressure difference between the high-pressure side (tube side) and the low-pressure side (shell side), MPa. This formula is applicable to high-pressure fluid in liquid phase. 7.0.9 Out of control of chemical reaction
7.0.9.1 For exothermic chemical reactions, if the automatic control of temperature, pressure and flow fails, the chemical reaction will be out of control and form a "flying temperature". At this time, a large amount of heat will be generated, causing the material to evaporate rapidly and form an overpressure. In this type of accident condition, the installation of a safety valve cannot meet the requirements in terms of reaction time or discharge rate, and a bursting disc should be installed.
7.0.9.2 If the patent owner can provide an accurate chemical reaction kinetic correlation formula to calculate the discharge volume under the accident condition, a safety valve can be installed with the consent of the patent owner and the construction party. 7.0.10 External fire
7.0.10.1 This regulation applies to containers containing liquids exposed to external fires. 7.0.10.2 Wetted area of the container (A)
The area below the liquid surface in the container is collectively referred to as the wetted area. The heat transmitted by the external flame vaporizes the material in the container through the wetted area. The wetted area of different types of equipment is calculated as follows: (1) Horizontal and vertical containers: Compare the surface area of the container within a height range of 7.5m from the ground or 7.5m above the platform where a large flame can be formed with the surface area below the highest normal liquid level, and take the smaller value. a. For equipment with elliptical heads, the total surface area is: A = Yuan D (L + 0.3XD) || tt || (7.0.10-1)3(Cvi—Cv2)Ph(G/T)1/2Wherein
W is the mass discharge flow rate, kg/h;
Cvi is the Cv value of the control valve;
Cv2 is the Cv value at the minimum flow rate of the control valve, Ph is the working pressure on the high-pressure side, MPa;
Gg is the gas phase density, kg/m
T is the discharge temperature, K.
If the material on the high-pressure side is likely to transfer heat to the low-pressure side, the influence of heat transfer must be considered. (7.0.5)
（2）For liquid phase pipelines, the discharge volume of the safety valve is the difference between the maximum flow rate of the control valve and the normal flow rate, and it is necessary to estimate whether the material on the high-pressure side flashes. 7.0.6 Excessive heat input
Under conditions such as the control valve on the heat medium side of the heat exchanger failing to fully open, the shut-off valve opening by mistake, the heating jacket of the equipment, and the shut-off valve opening by mistake, the gas evaporation or liquid expansion caused by excessive heat input is used as the calculation. 7.0.7 Volatile materials enter the high-temperature system
Under conditions such as light hydrocarbons accidentally entering hot oil and water accidentally entering hot oil, a large amount of steam is generated, causing the pressure in the container7.0.7.1
to rise rapidly.
7.0.7.2Since the discharge volume under this accident condition cannot be determined and the pressure rises very rapidly, it is inappropriate to install a safety valve and a bursting disc should be installed. 7.0.7.3The protection measures for this condition are to ensure that such accidents are avoided. 29
7.0.8 Heat exchanger tube rupture
7.0.8.1 If the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, it should be considered as an accident condition.
7.0.8.2 According to the conditions of 7.0.8.1, the discharge volume of the safety valve is compared with the result calculated by formula (7.0.8) and the normal flow on the high-pressure side, and the smaller value of the two is taken. 7.0.8.3 The discharge volume when the heat exchanger tube ruptures W=5.6·d2.(GXAP)1/2
W—mass discharge flow, kg/h;
d——tube inner diameter, mm;wwW.bzxz.Net
G liquid phase density, kg/m;
AP-pressure difference between the high-pressure side (tube side) and the low-pressure side (shell side), MPa. This formula is applicable to high-pressure fluid in liquid phase. 7.0.9 Out of control of chemical reaction
7.0.9.1 For exothermic chemical reactions, if the automatic control of temperature, pressure and flow fails, the chemical reaction will be out of control and form a "flying temperature". At this time, a large amount of heat will be generated, causing the material to evaporate rapidly and form an overpressure. In this type of accident condition, the installation of a safety valve cannot meet the requirements in terms of reaction time or discharge rate, and a bursting disc should be installed.
7.0.9.2 If the patent owner can provide an accurate chemical reaction kinetic correlation formula to calculate the discharge volume under the accident condition, a safety valve can be installed with the consent of the patent owner and the construction party. 7.0.10 External fire
7.0.10.1 This regulation applies to containers containing liquids exposed to external fires. 7.0.10.2 Wetted area of the container (A)
The area below the liquid surface in the container is collectively referred to as the wetted area. The heat transmitted by the external flame vaporizes the material in the container through the wetted area. The wetted area of different types of equipment is calculated as follows: (1) Horizontal and vertical containers: Compare the surface area of the container within a height range of 7.5m from the ground or 7.5m above the platform where a large flame can be formed with the surface area below the highest normal liquid level, and take the smaller value. a. For equipment with elliptical heads, the total surface area is: A = Yuan D (L + 0.3XD) || tt || (7.0.10-1)
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