Summary of Construction Work in Connection with the Renovation of 500,000 tons/year Catalytic Reforming Unit

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This post was last edited by I am kind on 2017-8-12 at 08:27. By compiling the materials, I found the summary I wrote ten years ago as a design representative while working on the construction project; it still touches me deeply. My first job after graduation: as a fresh graduate, after half a year of practical experience in operating equipment, I began my career in design, working on everything from process calculations for individual devices to process simulations for entire production lines, as well as equipment selection calculations and piping design ； Experience in preparing feasibility reports, basic design, detailed design documents, and supporting construction activities, etc. My six years of work at CNPC Dushanzi Petrochemicals were a valuable experience in my life, laying a solid foundation for my future career development. Thank you for the days of hard work and late-night efforts ； I am grateful to my mentors for their earnest guidance; their dedication and professionalism have had a profound impact on me ； Thank you to the DPDI “comrades” who have fought side by side through countless days and nights. -----------------------------The renovation of the 500,000 tons/year catalytic reforming unit was the first large-scale plant I was involved in designing since I started working. It took nearly three years to go from design to construction, and the expansion and renovation work was carried out taking advantage of the plant’s annual major maintenance period this year. The construction period for this project is short, there are many unforeseen issues at the site of the existing plant renovation, and the scope of the plant renovation is large. I have gained a great deal from cooperating with the construction process this time. Now, based on the problems encountered during on-site construction, I would like to share my insights. Design phase: The renovation of the 15,000 tons/year catalytic reforming unit is a retrofit of an existing plant; during the preparation of the construction drawings, it is necessary to visit the site frequently to ensure accurate representation of the parameters of the existing equipment and the layout of the original pipelines. Example 1: In this renovation, E-207B and E-106 are reused equipment. The installation diagram shows a standard heat exchanger, but the existing equipment on site is a condenser; moreover, the diameters of the tube side and shell side differ from those shown in the diagram. This not only requires additional materials but also leads to rework during construction (as the contractor has already pre-fabricated the pipes according to the diagram). Example 2: V-205 is an upgraded version of the original V-201; the civil engineering foundation for this equipment requires 8 anchor bolts, whereas the original equipment needed 16 anchor bolts. After the foundation on site was completed and the equipment was installed, it was found that something was wrong, so hole-drilling with a water drill was used to re-install the foot bolts. Example 3: The installation diagram for the refined oil line in the unit shows it to be located in a pipe gallery, but in reality it is situated in an underground trench; furthermore, there are filters and connecting lines on site as well. Example 4: In the original E-206ABCD air cooler, 206D has a single tube pass, with its inlet and outlet located at both ends; however, in the installation diagram, the inlet and outlet are on the same side. 2. The pipe diameter variation should be indicated in the PID diagram (by specifying elbows). The equipment nozzles are connected to the pipelines, and the pipelines are connected to each other. Example 1: The device ports of E-201 and E-206 have different diameters compared to those of the pipelines connected to them. Designers are required to prepare installation drawings in conjunction with the equipment drawings during the design process, confirming details such as the diameter of the equipment nozzles, the outer diameter and wall thickness, as well as their orientation. If the pipes have special materials, it will significantly affect the construction timeline (the lead time for ordering fittings made of special materials or non-standard fittings is long). 3. The installation drawings should be prepared in strict accordance with the PID diagrams; attention must be paid to the pressure level boundaries and the location of the blind flanges (whether they are placed before or after the valve, and whether they are in the open or closed position). Do not overlook any valves or fittings ； Example 1: The installation diagrams for the E-105A/B/C outlet valves and the F-102A/B fuel gas bus valves are missing. 4. For retrofit projects of existing installations, it is necessary to clarify the standards for the original pipelines within those installations; a unified standard should be used during the retrofitting process. If different standards are employed, the differences between them must be assessed. Specifically, different standards impose varying requirements on the outer diameter and wall thickness of pipes and fittings, especially for large-diameter pipes. It is also necessary to check whether the requirements regarding pipe diameter and wall thickness specified by the equipment’s professional standards are consistent with those of the process piping standards. These should be considered uniformly throughout the device design to avoid large misalignment of the pipes. Example 1: The outlet flange of the V-330 unit, DN400 (mating flange), uses a larger outer diameter (426), while the process piping uses a smaller outer diameter (406). Example 2: The original large-diameter pipelines in the facility all had a large outer diameter, whereas the pipelines installed as part of this renovation have a smaller outer diameter. Special attention should be paid to the fact that the fittings for SH are all of the small outer diameter series; when using GB-standard steel pipes and flanges, it should be specified that they belong to Series I, while if large outer diameters are used, Series II should be indicated. 5. The bolt length automatically generated by PPDS is the basic length; if an 8-shaped blind plate is inserted between the flanges, the bolt length should be increased. Example 1: The bolts at the 8-character blind flanges in this device were not long enough; ordering new ones required additional investment and delayed the project timeline. 6. For the ordering information of pumps and compressors, it is necessary to carefully verify the external dimensions of the equipment, the installation height, as well as the equipment nozzles and their positions. Example 1: The bottom plate of the pump is very large, which results in a large civil engineering foundation; there is not enough space during on-site construction. For instance, on both the east and west sides of the P101 foundation there are pipe trenches, so it is necessary to demolish one of the trench walls before formwork can be installed and the foundation poured. Example 2: The actual nozzle of the pump does not match the installation drawings, so tees were added on-site for adjustment. (Thorough verification should be carried out after the manufacturer supplies the materials.) 7. For the pipelines in the unit that require heating, the automatically calculated number of heating pipelines is equal to the length of the process pipelines; however, in actual construction on site, the amount of heating pipelines needed is roughly twice that of the process pipelines. 8. On the installation drawings for the renovation of existing equipment, the original old pipelines related to the new pipelines should be represented as accurately as possible ； By considering the spatial distances between the new equipment and the existing equipment in both plan and elevation views, and by combining on-site conditions with the architectural blueprints, more accurate installation drawings and layout plans can be prepared. Example 1: The locations of V-204 and V-205 do not intersect with the pipe trays or air coolers in the plan view, but at a height of 9 meters, they come into contact with the maintenance platform of E-203 as well as the outlet collection pipe. 9. If a grid plate is used for the framework platform, holes should be reserved in the grid plate when pipes pass through it; (the grid plate manufacturer will produce the grid according to the locations of these reserved holes). On-site construction involves cutting holes in the grid plates and severing them, which affects their strength and stiffness. Example 1: On the grid plate platform adjacent to Unit C-202, when pipelines passed through, the grid plate was cut, causing the platform to collapse. On-site, platform beam support grid plates were added as a remedy. 10. Determination of the height of the column brackets in the compressor room. General formula: Foundation height of the unit + height of the largest component of the equipment (usually the motor) + height of the largest component of the equipment + (0.5–1.5 meters of clearance) + length of the hook + vertical length of the rope. Example 1: Although the height of the C-202 machine room is sufficient for lifting operations, there is not enough headroom, which increases the difficulty of lifting and moving objects. 11. The lubricating oil pipes for compressors should be made of stainless steel, as well as the fittings. The pipeline from the compressor dry gas seal to the unit’s main body should also be made of stainless steel. 12. If the equipment requires heat tracing, external heat tracing should be used. 13. The interlock system scheme for the plant process should be determined through consultation with the user during the process design phase. 14. The layout of process pipelines, instruments, and cable trays should be coordinated during the design phase to avoid intersections during construction. 15. The internal frameworks, equipment platforms, pipe galleries, etc. within the facility should preferably be interconnected to facilitate inspections and evacuation. On-site construction: 1. The on-site design representative should resolve promptly any issues raised by the contractor on the day of construction. 2. Problems encountered on-site each day should be documented in writing (produce a white print and fill out the on-site service record form) to facilitate traceability of these issues. 3. Construction issues related to non-specialized areas should be addressed promptly by contacting the relevant specialized designers. During the construction phase, the general sequence of work is civil engineering and steel structure construction, followed by the installation of equipment, process piping, instrumentation, and electrical systems. At the end of the construction period, the work for each specialty is completed, after which the workshop carries out the \"three inspections and four determinations,\" as well as pipe purging, pressure testing, airtightness checks, and water testing. For a newly constructed facility, the general layout discipline should be handled first, followed by construction in the order mentioned above. Fun fact: 1) Civil engineering foundation construction: The contractor determines the location of the foundation based on the drawings (by marking out the boundaries), then digs to the required depth. After that, the foundation is inspected to ensure that it has been dug to the original soil layer and that its bearing capacity meets the requirements. Once approved, construction proceeds according to the civil engineering drawings (laying the foundation slab, installing rebar, fixing anchor bolts, etc.), followed by curing of the foundation. 2) For the lifting of large-scale equipment, the contractor shall prepare a lifting plan, which must be reviewed and approved by all relevant parties before the lifting can take place. Pay attention to the weather conditions (wind speed, thunderstorms, etc.) during lifting. No work or standing should take place within the circular area of the boom during lifting operations. 3) Large equipment such as towers can be transported to the site in sections, assembled and welded on-site, and then lifted as a whole to measure foundation settlement after filling it with water. 4) It is very important to accurately position the equipment foundation and the anchor bolts used to fix the equipment in place. When binding the reinforcement for the foundation, positioning plates should be used to ensure that the anchor bolts are in the correct position, thereby preventing them from shifting once concrete is poured. (The anchor bolts of the reforming reactor were misaligned due to the absence of positioning plates.) 5) Construction of process pipelines: The prefabrication of process pipelines should begin during the construction phase carried out by the civil engineering team. For pipelines involved in the renovation of existing facilities, prefabrication should be carried out in stages to avoid extensive rework on site. During the pressure testing of process pipelines, pipelines with similar pressure ratings should be grouped together within the same testing package and tested simultaneously, in line with the process flow. 6) When the power cable and the instrument cable are close to each other, appropriate shielding should be employed to prevent the power cable from interfering with the instrument signals and affecting the operation of the device’s DCS. 7) After the pump is installed in place, the motor should undergo a single-unit test run: a load test run. After the piping is completed, the compressor lubricating oil system undergoes oil circulation to maintain cleanliness in the system and meet the operational requirements. After the unit is installed, it also needs to undergo a single-unit trial run as well as a load test. 8) The 4.0MPa steam needs to be targeted. (Purging function) 9) For equipment and pipes within the facility that are difficult to clean, blasting purging is used for cleaning. (The entire system is sealed with only one opening left, which is covered with asbestos sheeting; water or gas is then gradually applied under pressure to the system, and when the asbestos sheeting can no longer withstand that pressure, it ruptures and the dirt is carried out.) Subsequently, the thickness of the asbestos board can be increased and this process can be repeated several times until it is thoroughly cleaned). 10) The ignition and heating of the furnace, as well as its drying, should be carried out in accordance with the instructions provided by the manufacturer of the furnace lining. 11) Determination of the construction period: The construction of key equipment within the plant and of the building itself should be taken as the main focus, such as compressors, heating furnaces, reactors, multi-layer frameworks, towers, etc. It is necessary to take into account the volume of work involved in filling and excavating the civil engineering foundation, the installation of rebar in the foundation, and the curing period for the concrete foundation. The lead time for manufacturing and delivery of large-scale equipment, the time for on-site assembly and welding, and the time required for installation. The time for purging, pressure testing, and airtightness testing of the pipeline. Insulation and heating duration. The fire protection construction time for buildings and structures within the facility, etc. The key is to arrange the various construction processes in a reasonable manner. Avoid reversing the construction sequence to prevent delays in the project timeline. Focus on the construction of key processes. 12) The on-site construction representative should have knowledge of all relevant specialties, and must be thoroughly familiar with parameters such as the process flow of the installation, its layout, the ordering of key equipment, and the negotiation of technical agreements.