Seven stages of chemical technology from creativity to industrialization (Issue 54/Total 100)--Equipment layout

Thread Content

Seven stages of chemical technology from creativity to industrialization (Issue 54/100 in total) - Technology finalization: Equipment layout and boundary conditions Dear friends: Hello everyone! In the last issue, we talked about the calculation of the relief valve's relief volume, and the relief volume under each working condition was determined. This issue talks about a job dealing with "space" - equipment layout and boundary conditions. Most of the first sixteen core tasks are completed on a two-dimensional plane - PFD draws the logistics direction, and PID draws the pipeline and instrument logic. But the installation is ultimately built in three-dimensional space. The distance between the equipment, the height difference, the width of the operating channel, the space for maintenance and core pulling, and the direction of the pipe gallery - the arrangement of these spatial relationships directly affects the safety, operability and construction cost of the device. In the process package stage, the equipment layout does not need to be as deep as the construction drawings - that is a matter of the detailed design stage. However, the process package needs to provide a recommended equipment layout drawing to determine the overall layout of the device in space.: Which equipment is placed where, how the pipe corridor is routed, how high the frame is, and how long the span is. This drawing is an important input for subsequent engineering design units to carry out basic design and detailed design. 1. Organizing the dimensions of key equipment: First, figure out how big the "big guy" is. The first step in arranging equipment is not to draw a picture, but to sort out the dimensions of all the big equipment. From the equipment list, pick out the equipment with the tallest vertical type, the largest horizontal diameter, and the longest horizontal type. The size of these "big guys" directly determines the span, column spacing and floor height of the frame. The determination of span and column distance must comprehensively consider equipment size, operation and maintenance space and structural rationality. Commonly used spans are 6 meters, 7.5 meters, 9 meters, 10.5 meters, 12 meters, 15 meters, etc. ； Commonly used column spacings are 4.5 meters, 6 meters, 9 meters, 12 meters, etc. The floor height is generally not less than 5 meters - too low, and there is not enough space for pipes and maintenance ； If it is too high, the structural weight and cost will increase. The overall dimensions of the equipment placed within the frame directly affect the span selection. A tower with a diameter of 3 meters must be placed in the frame, and the span of the frame must be at least 4.5 meters to leave room for operation and pipelines. If the tower is very high, you should also consider setting up several levels of operating platforms. The elevation of each platform should match the position of the tower's manhole. 2. Pipe gallery and tower area planning The pipe gallery is the "highway" of the installation - process pipes, public engineering pipelines, and cable trays all run on the pipe gallery. The location and direction of the pipe gallery determine the pipeline layout of the entire plant. The location of the pipe gallery is usually selected in the center of the device, so that the length of the pipes leading to both sides is the shortest. When estimating the width, if there is no detailed statistics on the number of pipes, you can first consider it as 6 to 9 meters - this width can be adjusted later based on the actual number of pipes, and the number of layers can also be adjusted. If there are a lot of pipelines in the device, the pipe gallery can be made into two or even three layers, with hot pipes and low-temperature pipes arranged in layers to reduce mutual thermal impact. The layout of the tower area has formed a relatively mature pattern. The tower arrangement can be centerline alignment or outer wall alignment. Centerline alignment is more commonly used - in this way, the direction of the tower's pipe openings is more uniform and the pipe layout is more orderly. The clear distance between the outer wall of the tower and the frame columns should not be less than 3 meters - this distance takes into account the operation and maintenance space requirements for pipes, valves, and manholes. The classic layout of the tower area frame is the "three-story pattern”: The tower bottom pump and tower bottom heat exchanger are mainly arranged on the first floor, the reflux tank and the tower top product pump are arranged on the second floor, and the tower top condenser is arranged on the third floor. If four layers are required, a secondary condenser or vacuum pump is usually arranged on the fourth layer. This layout is not random - the top condenser is at a high position, and the condensate flows into the reflux tank by gravity. ； The reflux tank is in the middle layer, which is not only beneficial for receiving the liquid from the condenser, but also provides sufficient cavitation margin for the reflux pump. ； The pump at the bottom of the tower is on the ground for easy maintenance. At the same time, the height of the tower skirt ensures the cavitation margin at the pump inlet. The vertical thermosiphon type is preferred for the tower bottom reboiler - it has good heating effect and takes up less space. If conditions permit, the reboiler can be hung directly on the side or outside of the tower for easy maintenance and piping. 3. Arrangement of reaction zone and other areas The reaction zone is usually arranged in a separate area. There are several purposes for doing this. First, the reaction area is usually more dangerous and is arranged in a relatively independent area, which can reduce the risk of radiation to surrounding equipment. Second, the reaction system equipment is often irregular in shape - there is a stirring motor, a solid hopper, and a catalyst loading and unloading port - and after being arranged in an independent area, it will not affect the regular arrangement of other equipment. Third, reaction systems usually have special requirements for the height and location of supporting equipment—for example, a catalyst feeding system that relies on gravity flow needs to check whether the position difference meets the transportation requirements. For flows driven by gravity, the position difference must be calculated in detail during the equipment layout stage. This calculation cannot wait until the piping stage - if the elevation is not enough, the equipment foundation height or frame height needs to be adjusted, which cannot be solved by changing the pipes. I once had the experience that gravity flow was not smooth due to insufficient calculation of level difference. Later, for every flow driven by gravity, detailed calculations were required when arranging equipment to confirm that the level difference was sufficient. Pumps are usually centrally arranged on the ground floor for easy maintenance and operation. The spacing between pumps should consider the inlet and outlet pipes and valve operating space, as well as the space for extracting the motor rotor during maintenance. Rotating equipment such as compressors and refrigeration units are usually arranged in low-noise areas of the factory, or sound insulation enclosures are provided. Large compressors require an independent foundation to reduce the impact of vibration on surrounding equipment. 4. The equipment layout diagram of the operation and maintenance channels is not only for yourself to see, but also for the operators and maintenance personnel. The design of channels and platforms directly affects the daily operating experience of the device. Key operating channels and maintenance channels must be wide enough. The main operating channel should not be narrower than 1.2 meters, the maintenance channel should not be narrower than 2 meters, and the firefighting channel should not be narrower than 4 meters. Some devices leave very narrow passages in order to reduce the floor space. After the device is built, operators often complain that it is difficult to even turn around during inspections, let alone carry tools for maintenance. The location and elevation of manholes and hand holes are the main basis for setting up the operating platform. The manhole faces the operating platform, and when opened, there is room for people to stand. The opening direction of the manhole cannot be toward the wall or pipe - otherwise people will not be able to get in when the door is opened, or they will not be able to get out after entering. The number and location of manholes have been marked on the equipment data sheet, and they must be checked one by one during the equipment layout stage.: Whether there is a corresponding operating platform for each manhole, whether the platform elevation is appropriate, and whether the inspection space is sufficient. The platform should also consider escape routes. Operators in hazardous areas need to evacuate quickly in an emergency. The escape route should not be too long - when the distance from the exit exceeds a certain length, escape routes in two directions should be set up. This item is easily overlooked in many projects, but it is often a key concern during security reviews. 5. Suggested equipment layout drawings and three-dimensional design The traditional equipment layout drawing is a two-dimensional plan plus elevation drawing, marking the positioning dimensions and elevation of the main equipment. With the popularity of 3D design in various engineering companies, it is recommended that equipment layout be done directly in 3D - the equipment in the 3D model is three-dimensional and the spatial relationship is clear at a glance. Where pipes may fight, and where the operating platform is not wide enough, can be seen at a glance in the 3D model. It is recommended that the depth of equipment layout drawings be controlled at the level of "transmitting spatial intent". There is no need to be precise about the routing of every pipe and the positioning of every valve – that is a matter for the detailed design stage. However, the positioning and elevation of the main equipment, the span and floor height of the frame, the direction and width of the pipe corridor, the main operating channels and maintenance spaces - these large patterns must be clearly defined in the proposed layout. There is also a forward-looking consideration for equipment layout: Leave room for possible capacity expansion and technology upgrades. If you know that this product has the possibility of expansion in the future, you can reserve the location of the second phase equipment during layout, or reserve expansion space in the pipe gallery, so that you don’t have to strain your muscles during future technical transformation. Of course, don’t over-reserve – find a balance between “enough now” and “possible use in the future.” 6. Boundary Area Condition Table After the equipment layout is determined, all interfaces between the process package and the outside need to be listed one by one on the Boundary Area Condition Table. The boundary condition table is the "interface file" for external communication of the process package. The question it answers is: What is the state and condition of each material and public engineering medium that enters and exits the boundary area? The content includes the name of the medium, status, temperature, pressure, flow direction, flow rate, conveying method (continuous or intermittent), and the number of materials that may be conveyed at the same time. The data on the boundary condition table corresponds to the boundary symbol on the PID. All pipelines with boundary zone symbols drawn on the PID should have corresponding entries in the boundary zone condition table. Data consistency check is an important task when integrating the process package master instructions. Each material parameter in and out of the boundary zone in the boundary zone condition table must be sourced from the PFD or PID. The temperature and pressure come from PFD logistics data, the flow rate comes from the material balance sheet, and the transportation method comes from the process operation instructions. This traceability chain must be complete, because subsequent engineering design units must design peripheral supporting devices and public engineering pipe networks according to the boundary condition table. If the boundary conditions are wrong, the peripheral design will also be wrong. The boundary condition table should also indicate which pipelines are operated simultaneously and which are used intermittently. If several strands of materials will not be transported at the same time, shared pipes or equipment can be considered in the design of the pipeline system to save investment. But sharing is also risky - if materials are cross-contaminated during the switching process, or operating errors lead to material switching from different media, the consequences may be serious. Whether sharing is allowed requires clear advice at the process package stage. Next issue preview No. 55: HSE and analytical testing - the layout of the three waste emission inventories and sampling system design and equipment layout has been determined, and the boundary conditions have also been clarified. The next thing we want to talk about is the design of the device in terms of safety, environmental protection and health protection - how to compile the three waste emission inventories, how to identify hazardous factors, how to design the sampling system, and how to determine the analysis and testing items. This is a content that is easily overlooked by technical professionals in the preparation of process packages, but is very important in environmental impact assessment and safety assessment reviews. Expand next issue.