nal concrete foundations. The pumps and compressor house (PCH) is located in the southwest quadrant of the BTU. This facility consists of steel framing that partitions each piece of equipment and concrete pad base supports. Mechanical equipment is shown in orange. Steel module SM-01 is placed at the lower half of the BTU and supports heat exchang- ers, pipelines, and cable trays. Some heat exchangers are stacked to opti- mise the floor space. Butane steel module SM-02 is located in the northwest quadrant of BTU and sup- ports heat exchangers, pipelines, and cable trays. Columns of steel mod- ules (SM01) and (SM-02) are sup- ported on pile foundations. The substation building (SB) is shown in yellow and located in the southeast quadrant. This building consists of two elevated floors and hosts critical electrical equipment. The building size and layout are determined by the required inte- rior equipment spacing. The control building (CB) houses critical instru- mentation controls and is occupied almost continuously. Plant design criteria were used to determine the spacing between control buildings and process units where explosion potential is high. The soil profile consists of four main soil layers. The first layer is sandy with pockets of clay, with a thickness of 3.0m. The second lay- ers consists of silty clay with traces of coarse and an average thickness of 5m. The third layer is made up of silty sand mixed with very dense to hard cemented siltstone. This layer is very stiff and considered the bearing layer for pile foundations. Groundwater level was detected at about 3.0-4.0m depth. BTU structural design criteria Steel modules were designed for erection, operation, testing, and transportation load condi- tions. The dead load consists of the total self-weight of structural steel, equipment, permanent fix - tures, fireproofing, insulation, fixed partitions, piping, and elec - trical material. The weight of cable trays, safety ladders, cages, and junction boxes was also taken into account. The grating dead load
• Pumps and compressor house (PCH) • Butane reactor (BR) • Steel modules (SM-01), (SM-02) • Substation building (SB) • Control building (CB) • Heat exchangers, horizontal and vertical vessels • Underground services, roads, and parking Note that the layout of the BTU may vary depending on the process design. The layout in Figure 1 was designed to boost refinery produc - tion of synthetic light crude oil to 232 mbbl/d. The orange arrow shows the direction of north (N). Two main pipe racks support the pipelines transporting process material from/ or to the BTU. These are denoted as horizontal (HPR) and vertical (VPR) pipe racks in Figure 1 . HPR supports pipelines and cable trays running in the east-west direction and consists of seven modules. VPR runs from south-north and consists of 13 steel modules. The butane reactor (BR) is located in the north-west (NW) quadrant of the BTU and is supported by octago-
Therefore, it is important to high- light requirements for the structural design of natural gas processing plants. This article presents a butane treatment unit (BTU) case study to illustrate effective structural design procedures and highlight construc- tion challenges encountered in new and expansion projects. The layout of the BTU is presented to describe the facilities used in gas process- ing. Then, a brief overview of the geometric characteristics of the facility is provided to identify load- ing mechanisms. Structural design criteria developed for each facil- ity’s transportation, installation, and operation are also discussed. Simplified numerical modelling strategies are described to simu- late load transfer and soil/structure interactions. The article also pro- vides recommendations and guide- lines for engineers to use in practice. Butane treatment unit description The BTU is part of the naphtha hydrotreating facility and consists of: • Horizontal (HPR) and vertical (VPR) pipe racks
(HPR)
N
(VPR)
(SM-02)
(CB)
(BR)
(SM-01)
(SB)
(PCH)
Figure 1 Butane treating unit plan
32 Gas 2022
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