In order to improve the heat tracing design effect of process pipeline in chemical plant, the article combined with practical experience, while analyzing the content of pipeline heat tracing technology, the principle of its selection was discussed. At the same time, on the basis of discussing the selection of the tracing medium of the tracing pipe, the main points of its design method are explored, and it is hoped that after the discussion can provide some reference to the relevant staff.
In the normal operation of the chemical process piping, if there is unnecessary heat consumption, it will cause huge energy waste, and also will bring more serious environmental pollution problems. In the modern society where the energy situation is relatively severe, if the form of pipeline heat insulation cannot be effectively improved and the effect of heat insulation improved, it will be difficult to better ensure the smooth operation of energy transportation, which will have an adverse impact on the environment and the effect of pipeline transportation can hardly be improved. Comprehensive analysis of the current pipeline transportation situation, to understand the design of heat tracing, it is necessary to analyze the operation state of the pipeline in depth, in order to better improve the process design level of the pipeline. The following will analyze the main content of the pipeline tracing heat design, and hope that it can help to improve the level of tracing heat design.
1. Analysis of pipeline heating technology
The pipeline accompanies the heat technology is the modern society very advanced heat preservation antifreeze technology, at present is applied to various fields in large quantities. According to the accompanying heat structure form, can be divided into the pipeline accompanying heat traditional method and automatic regulation electric accompanying heat two forms. The basic principle of the work of the self-regulating electric tracing heat is in the pipeline operation process, because the temperature of the surrounding space drops, will lead to molecular structure changes, carbon particles in the process of flowing in the circuit, the tracing heat will continue to heat, when the tracing heat reaches a certain temperature, the molecules in the electric plastic will rapidly expand, the output power of the tracing heat will be reduced, so as to form a closed temperature control circuit, so that it can comprehensively This can enhance the heating power of the hot line.
2. The choice of pipeline heating form
In the process piping design, the process of heat tracing system design, can choose to use with the pipe or jacket with the way of heat, make up for the pipeline material conveying process of heat loss, maintain the material temperature. In the process of selection, should pay attention to is the pipeline internal transport medium conditions, should ensure that the medium terminal temperature to meet the requirements, to ensure and pipeline internal temperature can not have excessive deviation, or also can be slightly lower than the pipeline internal medium freezing point data. If the material freezing point in the applied pipeline is greater than or equal to 50℃ and below 100℃, you can use the way of accompanying tube accompanying heat, which can better realize the energy supplement. If the medium transported inside the pipeline is gas medium, when the ambient temperature is lower than the pipeline temperature, when the medium temperature is relatively high, you can also choose to use the way of accompanying tube accompanying heat. In the pipeline conveying medium temperature to be higher than the pipeline temperature, at this time the pipeline temperature is relatively low, in the freezing point below, or the liquid medium inside the pipeline freezing point less than 40 ℃, gas dew point more than the specified problem, can apply hot water accompanying pipe accompanying heat structure form. At present the most common application is the steam accompanying pipe and the jacket accompanying pipe form, its main use condition is the pipeline internal material is relatively easy to solidify, and will remain in the pipeline's interior for a long time 3.
3. Analysis of the medium of the accompanying pipe accompanying heat
In the companion pipe with heat media application link, generally will apply hot water to carry out, also can choose to use water vapor as the medium. In the case of using hot water to provide heat to the system, the internal temperature of the pipeline cannot exceed the specified range, and at the same time compare and analyze with the temperature parameter in the accompanying heat treatment, the pipeline temperature should exceed the temperature parameter, so that the hot water can be used to accompany the heat treatment, can achieve better results. Steam as the tracing medium use range is also relatively wide, mainly is applied to the pipeline medium temperature less than 150 ℃ working conditions, can achieve the ideal tracing heat treatment effect.
4. Steam tracing pipe design
Steam tracing heat use to chemical production link, the effect is better, so the use is more common. In the specific operation link, has the material and temperature adjustment more convenient, condensation latent heat and adaptability is very strong and other advantages, so is widely used to the chemical production, can better play the effect of heat preservation, anti-freeze crack.
- One is the main pipeline, the chemical production of steam will be directly through the pipeline to complete the entire transport process.
- Its second is the introduction pipeline, steam in the process of transport through the pipeline, you can use the conduit directly into the specified area.
- The third is the distribution station, the role of which is to carry out steam collection, according to the provisions of the system to do distribution processing.
- The fourth is the steam tracing pipe, which can adjust the system temperature in a comprehensive manner.
- The fifth is the collection pipeline, which should carry out the necessary thermal insulation treatment in the running link of the companion pipe, and then be able to form condensate in the end and collect it, and then apply the conduit to lead it out, to prevent the long-term retention of the situation inside, causing the existence of pipeline corrosion problems; and
- The last is the main pipeline, can be directly inside the pipeline formed by the condensate collection processing, and then all the condensate will be unified lead out. Chemical process piping in the development of steam with heat design links, from the entire system functionality, to carry out a systematic design.
First, steam should be selected to provide sufficient heat to the system. The pressure parameter of the steam should be above 0.3 MPa and below 1 MPa, and the diameter of the piping used should be above 18 mm and below 24 mm. In the pipeline transportation link, if the solidification point of the medium inside the pipeline reaches about 50°C, the pressure of the steam used to accompany the heat should be reasonably determined to ensure that it reaches about 0.3 MPa. If the solidification point of the medium inside the pipeline will exceed the value of the original solidification point parameters, then the process of operation should strictly control the steam pressure parameters to ensure that it is below 1 MPa, and then be able to achieve the comprehensive use of multiple pipelines to carry out the necessary insulation treatment to prevent the existence of a large loss of heat. Second, in the design, it is necessary to take into account the actual diameter of the pipe parameters.
In the process of design, the pipe diameter in the range of DN15 - DN25, the effect of accompanying heat is better. Then should comprehensive analysis of a variety of factors, and then be able to determine the specific number of accompanying heat pipe. The number of parameters should be determined under the condition of taking into account the internal transport medium, and also need to achieve the corresponding standards stipulated by the chemical enterprises for insulation design, in order to achieve the scientific and reasonable requirements of the number of pipes. In the design process, the requirements of thermal compensation should be analyzed. Steam with heat treatment link, according to the specific length of the pipeline size, generally need to be set up in the location of 25 meters, but also need to be arranged according to the requirements of the compensator structure, so that you can achieve the role of heat compensation. Also need to make full use of the pipeline bending type, for heat compensation link should be clear in the pipeline fixed point, the use of tie to carry out, to ensure its stability qualified. In the process of fixing, should be comprehensive analysis of the material of the companion pipe, and then carry out the necessary isolation, to prevent the pipeline deformation, damage and other problems. Steam accompanying pipe accompanying heat treatment stage, should pay attention to, if the internal medium of the pipeline has high corrosive, it is necessary to ensure that it has a corresponding distance with the accompanying pipe, to prevent the pipeline damage, generally need to set up asbestos board in the two to isolate. In addition, steam accompanying pipe distribution station, hydrophobic station and other parts in the design, if its in three meters away, then need to be arranged according to the requirements of the number of more fixed points, then should be in the position to determine more than one site, and in the installation construction stage should try to maintain the horizontal installation, can also choose the vertical installation mode, in order to better ensure that the installation quality qualified.
5. The problems that need to be paid attention to in the design of the tracing pipe heat tracing
First of all, should pay attention to, in the pipeline design link, with the pipe inside if is steam medium, can use the main steam pipeline to lead out, should be led out of the pipeline in and out of the position of the installation of the corresponding valve, after the steam is led out, can through the valve to its transmission pipeline to cut off processing. Second, in the design process, it should be installed in the trap door position, and it should not be necessary to arrange the bypass valve device according to the actual situation, so as to prevent the existence of steam intrusion and other defects in the condensing system operation. In addition, steam should be introduced reasonably in the design process, and in a top-down order, but the location of the introduction should be raised as much as possible so that the process effect of the whole system can be improved.
The condensate drainage system should be designed to be as low as possible and then introduced to prevent it from being affected by other factors. The condensate drainage system should be designed in such a way that U-shaped pipes are not used as much as possible, otherwise the discharge of water will be affected. Then, in the design stage of the heated piping, the location of the venting valve should be accompanied by heat treatment, so that the entire steam can be recycled as soon as possible. Therefore, in the design of the link, the location of the main pipeline should be arranged with the design and use of heat, and for other locations on the branch pipeline also do not need to implement with the heat treatment, while the need to apply the cut-off valve device in the branch pipeline near the location, and then the implementation of heat design, in order to improve its thermal insulation performance.
The design of the heat tracing system can better play the effect of heat insulation and heating, in the system operation link, to organize personnel to carry out regular testing. Pipeline in the initial stage of operation, should be the internal pipeline stored in the moisture out, otherwise it will lead to serious safety accidents. In addition, also need to strictly control the valve opening size, according to the need for debugging treatment, to prevent the normal opening of the situation exists, but also to avoid valve failure and lead to the decline of the heating effect and other problems, to ensure that the system can be normal operation.
Chemical process pipeline in carry out with heat design link, should understand the pipeline operation, if there is heat loss and other problems, to timely compensation, prevent the temperature from falling too fast and lead to the pipeline can not be normal operation, to ensure that the system operation more safe, stable.
Author: Zhou Enshen