Some standard content:
Analysis of differential pressure of pumps and compressors
HG/T 20570.4-95
Compiled by: China Huanqiu Chemical Engineering Corporation Approved by: Ministry of Chemical Industry
Implementation date: September 1, 1996 Prepared by:
Wang Qingyu, China Huanqiu Chemical Engineering Corporation
Reviewed by:
Gong Renwei, Process System Design Technology Center, Ministry of Chemical Industry 1.0.1 Responsibilities
1.0.1.1 The process system specialty is responsible for determining the differential pressure of all pumps, compressors, and blowers. When the chemical process specialty has other required working conditions, such as different flow rates and material weight and viscosity changes, the process system specialty needs to determine the corresponding differential pressure for various situations. 1.0.2 Requirements
The determination of the pressure difference of pumps and compressors shall meet the following requirements: 1.0.2.1 Calculate and propose as soon as possible after the process is published; 1.0.2.2 The determined pressure difference shall select an appropriate safety factor and should not be too conservative 1.02.3 The data in the pump data sheet proposed by the chemical process department shall be as close as possible; 1.0.2.4 Subsequent modifications shall be minimal;
1.0.2.5 Where control valves are used, the system's regulating performance shall be good. 1.0.3 Information required for determining the pressure difference
Since the pressure difference must be determined early, the process system department shall at least need the following information when using preliminary basic data to determine the pressure difference:
1.0.3.1 Process load table.
(1) Process working conditions of the pump.
Process data sheet of the compressor.
1.0.3.2 Process flow chart.
Design data of the project.
Preliminary dimensions and layout of heat exchangers.
Preliminary furnace pressure data.
Simplified vessel diagram (including pressure difference between tower and vessel). Preliminary process control diagram.
1.0.3.8 Equipment layout diagram.
1.0.3.9For the content of the above information, please refer to the corresponding provisions in the industry standard "Provisions on the Content of Accepted Documents for Process System Professionals" (HG20558.1-93).
1.0.4 Calculation table
The calculation of the pump is carried out item by item according to the pump calculation table. For the pump calculation table, please refer to "Calculation of System Characteristics of Pumps and Determination of Relative Installation Height of Equipment" (HG20570.5-95). The calculation table of the compressor can be compiled according to the compressor conditions listed in the industry standard "Provisions on the Content of Documents Submitted by Process System Professionals" (HG20558.2-93). 93
2 Contents of Accepted Data
2.0.1 The accuracy of the pressure difference depends largely on the accuracy of the design data used and the reliability of the data used in the project. The process system specialty must verify the consistency and completeness of the data of each edition accepted at each stage, and should promote the confirmation of the data of each edition in each stage by the relevant specialty. 2.0.2 The contents of the data accepted by the process system specialty during the pressure difference analysis are as follows: 2.0.2.1 The working conditions (process load table) of the pump shall be proposed by the chemical process specialty on the date of the process publication. The data include: normal flow, design flow, safety factor, medium name, medium vapor pressure, specific gravity, viscosity and approximate suction and output pressure difference. 2.0.2.2 The compressor data table (process load table) shall be proposed by the chemical process specialty on the date of the process publication. The data include: material name and composition, molecular weight, vapor pressure data, flow under normal and design conditions, inlet pressure and temperature, output pressure, compression coefficient, specific heat and adiabatic index of gas and molecular weight. During the process design stage, a rough economic study is usually conducted on the compressor and piping system. The process system professionals should try to maintain the pressure difference within the range of the determined compressor suction and outlet pressures and the process professional settings, unless the accumulated experience of the process system professionals confirms that the pressure difference setting proposed by the process professionals is obviously unreasonable. 2.0.2.3 The process flow chart
is proposed by the chemical process professionals on the date of process publication. The data includes: the system flow chart connecting all process equipment, the material flow, temperature, pressure of the pipeline, the specific gravity, density and expansion coefficient of the material and other pipeline conditions. The flow data indicated on the process flow chart should meet all hydraulic calculations of the process system. The missing data should be discussed with the chemical process professionals immediately and supplemented as soon as possible. 2.0.2.4 The design data of the engineering project
is proposed by the project manager (design manager) on the date of publication of the engineering design commencement report. The data includes: the pressure and temperature conditions of all process and public material pipelines at the boundary of the boundary area specified by the construction party. When these data are not presented, the process system specialist should notify the project manager and point out that the pressure differential can only be determined after obtaining this information. bZxz.net
2.0.2.5 The preliminary size and layout of the heat exchanger shall be presented by the heat exchanger analysis specialist shortly after the process data is published. The data shall include: preliminary heat exchanger data, including type, number of shells, number of tubes, tube and shell flow rates and approximate pressure drop. If necessary, the process system specialist may discuss with the heat exchanger analysis specialist whether the allowable pressure drop figures are accurate before the formal presentation of the heat exchanger data. 94
2.0.2.6 Preliminary pressure data for furnaces
The preliminary pressure data for furnaces shall be presented by the industrial furnace specialist shortly after the process data is published. The data shall include: expected inlet and outlet pressures at normal and design flow rates, pressure drops and safety factors when all furnace tubes are clean, coked and scaled. The pressure differential shall be calculated using this data and verified when the final data is formally presented. 2.0.2.7 Vessel schematics
are proposed by the chemical process major, and the time of proposal is shortly after the process is published. The data include: shell size, size and position of all nozzles and tower plates, allowable pressure drop, working temperature, working pressure and nozzle name. The vertical length and static pressure head of the pipeline are determined by the vessel schematic and equipment installation elevation. When it takes a long time to propose the cylinder diagram of some vessels, the chemical process major must provide the shell size, nozzle position and pressure drop to the process system major as soon as possible after the process is published. The pressure difference calculated and proposed on this basis must be rechecked when the vessel schematic is officially published.
2.0.2.8 Pressure drop between tower and vessel
is proposed by the vessel analysis major (or chemical process major), and the time of proposal is shortly after the process is published. The data include: pressure drop after the medium passes through the container, tower, reactor and packing tank. When more than one operating scheme is expected, the operating pressure drop of various schemes should be indicated. The process system specialty calculates the pressure drop (including friction and static head loss) of some internal parts of certain towers and containers and the pressure loss at the inlet and outlet of the pipes based on the data submitted by the chemical process specialty. 2.0.2.9 The preliminary process control diagram (PCD) is submitted by the automatic control specialty shortly after the process is published. The content includes: the installation location of all instruments for the process and auxiliary and public materials according to the basic control plan. Since the automatic control specialty prepares the PCD or the flow chart with main control points from the chemical process specialty at the same time as the pressure difference is determined by the process system specialty, it is necessary to determine and discuss the system control plan between the specialties first, and conduct a formal check when the PCD (or the flow chart with main control points) is published. 2.0.2.10 Equipment layout diagram
(1) The recommended equipment layout diagram
is submitted by the chemical process specialty on the date of process publication. The recommended equipment layout diagram can be used to roughly estimate the pressure drop of all pipelines. The content of the recommended equipment layout diagram can be found in the relevant provisions of the industry standard "Provisions on the Content of Acceptable Documents by the Process System Specialty" (HG20558.1-93). (2) The D version (confirmed version) equipment layout drawing is proposed by the equipment layout professionals.
The time and content of the proposal can be found in the relevant provisions of the industry standard "Provisions for the Content of Accepted Documents by Process System Professionals" (HG20558.1-93).
When there are major changes to the proposed equipment layout drawing or the D version (confirmed version) equipment layout drawing, the pressure difference values of the pump and compressor must be recalibrated.
3 Pump pressure difference calculation
3.0.1 The steps for calculating the pump pressure difference are in accordance with the calculation method in the industry standard "Calculation of Pump System Characteristics and Determination of Relative Installation Height of Equipment" (HG/T20570.5--95). 3.0.2 Use the calculation table and method in "Calculation of Pump System Characteristics and Determination of Relative Installation Height of Equipment" to draw a system sketch marked with length, pipe diameter, elevation, valves and pipe fittings to calculate the equivalent length and static pressure head. 3.0.3 Precautions for calculating pump pressure difference
3.0.3.1 Use the calculation method of pump net positive suction head (NPSH) in "Calculation of pump system characteristics and determination of relative installation height of equipment".
3.0.3.2 For pipelines out of the boundary area, check the pressure at the boundary area with relevant professionals or calculate point by point to the equipment outside the boundary area to determine the boundary area pressure.
3.0.3.3 For pumps with multiple discharge pipelines, each pipeline must be analyzed to determine which pipeline requires the maximum pump discharge pressure at the maximum parallel output during operation. 3.0.3.4 The maximum terminal pressure of the boiler feed pump (discharge side container pressure) is the maximum allowable accumulation pressure of the boiler (i.e. the boiler safety valve relief pressure)
3.0.3.5 The selection of the control valve must provide good regulation performance of the system within the operating range, which is reflected in Cve/C (Ce—calculated value of the flow coefficient, C——flow coefficient of the control valve). The normal flow and the design flow should be checked and filled in on the control valve data sheet. Usually, the initial control valve size is one level smaller than the pipeline size.
3.0.3.6 After the pressure difference of the pump is determined, the actual design output pressure and control valve pressure drop are calculated. 3.0.3.7 The maximum closing pressure of the pump should be the highest static pressure head on the suction side plus the maximum pressure in the suction side container (i.e. the set pressure of the safety valve on the suction container), plus the pump head at zero flow. 97
4 Calculation of pressure difference of compressor
4.0.1 After the pressure of the compressor suction source is determined, calculate the pipeline resistance point by point to the compressor suction port according to the normal flow rate. The pressure loss of all equipment in the inlet pipeline must be included. This pressure is the suction pressure of the compressor at normal flow rate.
The suction pressure of the compressor at the design flow rate can be obtained by adjusting the pipeline and pipe port resistance according to the design flow rate and calculating the pressure loss of all inlet and outlet equipment. 4.0.2 After determining the terminal pressure of the compressor discharge pipeline (i.e., the discharge side container pressure), start from the compressor discharge pipe port according to the normal flow rate, and calculate the position where the pressure drops to the terminal pressure (i.e., the discharge side container pressure) point by point with the output pressure on the compressor data sheet published by the process. This pressure will determine the gas density at the compressor outlet. When moving forward point by point, the gas density decreases due to pressure loss. After the calculation is completed, list all the resistances and pressure losses in the pipeline into a table. The sum of the terminal pressure (i.e., the discharge side container pressure) plus the total pressure loss on the pipeline is the discharge pressure of the compressor under normal flow conditions. The discharge pressure of the compressor at the design flow rate is equal to the adjusted pipeline friction resistance loss at the design flow rate, plus the pressure loss of the equipment, plus the terminal pressure. Usually, the compressor piping system has been economically analyzed before the process is published. The process system professional should try to maintain the suction and discharge pressures listed on the process load table. The compressor piping system is usually maintained by gas flow rate control rather than using control valves to maintain pressure. Therefore, the pressure loss in the system comes from the furnace, container, heat exchanger, pipe and fittings. Among these units, the heat exchangers, pipes and fittings are the most flexible in pressure drop changes. Changes in the pressure drop (△P) of the reactor bed, tower and storage tank are not obvious unless the process requires a large pressure drop (AP) change.
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