PTQ Q3 2022 Issue

test data. The lateral spring stiffness was variable through the embedment length, and the spring constant was averaged using 4m intervals. Flexible supports were used at the bot- tom of the piles to stimulate the end bearing in the soil bed. It must be emphasised that minimum pile projections of 150mm inside the pile cap are a critical requirement to secure load transfer to the soil and provide adequate length for verti- cal pile reinforcements. Axial pile capacity was verified using pile load test data obtained from several plant areas in the vicinity of the reactor support system. Pile lateral load capac- ity was reduced to account for the group interaction effect. Numerical results The first application example is provided for the absorber stripper reactor (ASR) used in the hydrocarbon extractions process. Several ASR models are used in industry to perform the transformation process. The reactor geometry used in this study is shown in Figure 4 . The diameter (D R ) =5.5m, thickness is (t) R =14 mm and the total length (H Z ) is variable. The skirt diameter (D Sk )= 5.2m, and the dressing extends 8.7 m measured from the finished grade. The reactor is required to withstand internal design pressure (P R ) Int =1,315 KPa at 227˚C and field hydro test pressure (P R ) FT =1,625 KPa. Figure 5 shows the design space for the ASR support sys- tem. Four piling configurations are used. Configuration (A) uses 4 piles (m=n=2), configuration (B) uses 9 piles (m=3, n=3) and configuration (C) uses 16 piles (m=n=3). Pile diam - eter ( Φ P )=750mm is used in all configurations. The reactor height varies between (H Z )=6-120m. Three pile lengths are used in Figure 5 . The dashed green line denotes (L P =14m). The feasible design segments of configuration (A), (B) and (C) using this (L P ) value are identified using identical line colour and leg - end. Pile embedment length (L P =18m) is identified by a solid black line. Similar treatment is accorded to the correspond- ing configurations. Pile capacity for (L P =20m) is shown by a red dashed line. Solid circles represent intersection points of (L P =14) with the three configurations (A-C). Magnitudes of these points are (14, 12.4) B , (14, 36) C and (14,48) D . Similarly, solid triangles are used for piles with (L P =18m). The magni- tudes are (18, 3) A , (18, 28) B , (18, 64) C , (18, 84) D . Finally, plies with (L P =20m) intersect with configuration (A) at (20, 13) A , (20,52) B , (20, 106) C , as shown by solid red circles. It can be observed that by increasing the pile embedment length by 6m, the reactor height can be increased from 36m to 106m. The second application example is provided for a typi- cal butane stabiliser reactor (BSR) used in the hydrocarbon industry. The reactor size and height depend on the process design capacity. Platforms normally surround the reactor body at various elevations to support operation and mainte- nance requirements. Figure 6 shows a BSR’s three-dimen - sional elevation view as part of a gas recovery unit (GRU). The adjacent steel module (shown in red) supports mechani- cal equipment, pipelines, and cable trays. The weight of these connected accessories is: cable trays (W R ) trays =0.29 tones and pipelines (W R ) Pipes = 1.2 tones. The reactor internal diameter is (D R )= 1.4m, thickness is (t) R =9 mm, and overall height (H Z ) is variable. The skirt dressing is 4.2m in height with diameter (D SK )= 1.6 m. The pile-cap size

Figure 4 3D view of absorber/stripper reactor

system. The skirt reactions were transferred to piles using displacements and rotational compatibility constraints along the connection nodes. Flexural beams were used to transfer the skirt loading to the pile cap. Auxiliary nodes were generated at the bolt loca- tions to simulate out of plane bending and model the load transfer of the reactor loads into the pile cap. Nodes around bolts were connected to their adjacent node on the pile cap support using extensional and rotational spring elements. Compatibility of displacement in z-direction and rotation in y-direction were imposed in this model. A non-linear elastic- plastic material model is used for the support system. Shear deformation of concrete support was ignored. Furthermore, the reactor diameter was increased to compensate for attached steel platforms, pipes, and cable trays. Piles were restrained bi-laterally throughout the embedded length using horizontal springs. The pile head rotations and in-plane translations were restrained in the x and y directions ( θ x = θ y =u x =u y =0). This assumption is justified by casting the pile cap with the pile head concurrently. The stiffness of piles was variable to reflect the variation in the pile casings. The sub-grade lateral stiffness was determined using borehole

(D)

(C)

120

100

L = 20m P

(B)

L = 18m P

L = 14m P

(A)

500

1000

1500 (KN)

2000

(P , Q ) P P

Max

Figure 5 Design space of absorber/stripper reactor

PTQ Q3 2022