Heat exchanger core pulling Aerial Pulling Bench Design

Abstract: A heat exchanger core pulling Aerial Pulling table design. Pulling table discusses the structure and working principle, structure design focuses on the stringer and mechanical calculations, which use two safety factor to determine the fuzzy comprehensive evaluation method. The design of the heat exchanger core pulling aerial vehicles set lifting, core pulling, walking three functions in one machine to achieve the integration of core-pulling device, changing the dependent crane operations with backwardness.

In order to achieve substantial increase in the efficiency of heat exchanger repair, maintenance work to increase the degree of automation and civilized production, we designed a heat exchanger core pulling aerial vehicles. It implements a traffic-type heat exchanger core pulling machine program, the core pulling devices and chassis combine into one, not only can automatically lift pumping core, but also between the various devices or walking between the refinery and improve the equipment mobility. Car design into the main operating metal structure design [1-2] and Pulling bench design two parts, here introduces the core pulling bench design.

1 is the major deficiencies with the core-pulling machine

Currently, refineries or chemical plants generally use the semi-mechanized devices [3-4], such as frame-by power pumping spiral core machine, core-pulling winch frame machine. Pulling the crane lifted to the air core-pulling machine, to align the heat exchanger tubes weeks after the end of the rigid core-pulling machine heat exchanger fixed to the tower shell, cover with rope in the tube bundle panel, steel wire rope other end of the sleeve nut on the mobile, screw weeks after starting the motor or winch to the mobile sector, resulting in pulling out the tubes from the shell, out of bundle, the bundle together with the core-pulling machine into the ground by crane. The pulling mechanism, although to some extent, improve the maintenance of automation, but there are a large number of defects. First, core-pulling machine can not work independently and must rely on a large crane to complete the pumping with the core operations; second, core-pulling captain 9m, whether it is transportation or operation is not easy; Third, core-pulling machine with tubes degree swing in the air great, the workers work very difficult, security is poor; the fourth, pumping the core process to be shut down twice, the position of artificial moving wire rope, core pulling a long time, taking up a large proportion of working hours, or low degree of automation.

Pulling bench 2 new works

2.1 Technical Performance

Pulling the form table for the hydraulic and mechanical forms of combination, the maximum pumping core specifications  1200mm × 6000mm; the maximum weight of 10000kg; maximum pumping height core 18m; Pulling bench to start the length of 8m; Pulling Bench maximum width 2m, maximum body width of 2.5m. It uses hydraulic cylinder force Congress and the mechanical devices and fast speed, the tubes can be collected or sent back to the maximum pumping to meet the needs of tension and fast.
outdoor cable tray, cable tray suppliers, data cable tray
2.2 Structure and working principle

Figure 1 is a heat exchanger core pulling Aerial schematic. Double-dotted line for non-working state, the solid line to work state. Pulling Pulling framework in table below, together with the frame sections move up and down along the tower, avoiding the drawbacks with using the crane. Pulling the length of the table in Figure 1 in the direction perpendicular to the paper in this direction, the table is divided into three parts, the middle part does not move, both sides of the folded part of the hydraulic cylinders, core pulling machine to avoid the disadvantage of long .

Pulling the operation table shown in Figure 2, the first pumping section of the core table slide along the main tower and the tower to pull the location of the heat exchanger rather by the lateral movement of the screw for fine-tuning bench, put down both sides of the folding part, the use of two front vertical table adjustment of the hydraulic cylinder tubes parallel to the direction of the table and the displacement, while the meniscus is installed on the piston rod with different diameters relative to the heat exchanger shell flange solid with these completed, the Pulling can work.
Aramid Packing Ring
 Pulling, by the hydraulic motor driven winch drag the table fast approaching heat exchanger core by pumping large initial tension, the initial stage by the main hydraulic cylinder out of control, when the tubes are out of 1m or so, switch to winch quickly out, after taking the proper distance reined in turn put two cable bundles and continue until the tubes out from the shell, the table will bundle into the ground to complete the core-pulling work. Returned to action with the opposite bundle. Core-pulling operation, the tower section and the pumping core framework does not move, the workers and effortless operation, security is good.

3 Pulling table design

Pulling bench designs, including longitudinal design, hydraulic and transmission design, fine-tuning the design agencies and other components [5-8].

3.1 Pulling Bench stringer design

3.1.1 Structural design of the main table for the two rails, hot-rolled I-beam material selected Q235A, Model 14, each longitudinal beam length is 8m, are mounted on rails through the dovetail-shaped core pulling frame.

3.1.2 mechanical calculation of two symmetrical on the vertical longitudinal center line, so they are seen as a beam, the calculated stress divided by 2 can be. Pulling the process in each moment of the force beam is not the same, the force of the beam analysis, all the tubes out and the center of symmetry in the stringers, stringer and the shell from the heat exchanger maximum contact stress. Supported by the anti-strike force, bending moment diagram drawn to determine the maximum bending moment, check geometric properties of the material to take a series of conventional steps, find the dangerous section of maximum stress. The difference is that the allowable stress to determine the beam, the use of two fuzzy comprehensive evaluation method to determine the safety factor, as follows.

1) set of factors influence the establishment of a major safety factor value of fuzzy factors design level u1, manufacturing level u2, material quality u3, conditions of use u4, importance of u5, u6 manufacturing cost and reliability of u7, factor set is U = {u1, u2, u3, u4, u5, u6, u7}.
PAN Packing
2) division of the factors that determine the factor levels and levels of membership according to the nature and extent of each factor is divided into five, and then determine the degree of membership of each factor level of 0 to 0.5. Classification of various factors and membership (normalized values) in Table 1.

3) the establishment of a safety factor of the alternative set of values interval [1.2,2.0], 0.1 by step after that this continuous range of alternative discrete set of n = {1.2,1.3,1.4,1.5,1.6,1.7,1.8 , 1.9,2.0}. 4) for a fuzzy comprehensive evaluation using the factors common membership of the same rating as the row matrix:

The factors listed in Table 1 the value of membership of each level of each factor as the weight wij, then get the i-th factor Wi = (wi1, wi2, ..., wi5) i = 1,2, ..., 7 (1) factor of the i fuzzy sets in various levels of comprehensive evaluation, fuzzy comprehensive evaluation was a set Ai = Wi • Ri, respectively, i = 1,2, ..., 7 substituted, and substituted into wi1 and Ri of the values, calculated a fuzzy comprehensive evaluation matrix A is:

  5) for two fuzzy comprehensive evaluation similar to that of the factors important was no significant difference in the weight set J = (1 / 7, 1 / 7, 1 / 7, 1 / 7, 1 / 7, 1 / 7, 1 / 7), after a comprehensive evaluation of various factors have two fuzzy evaluation set is B = J • A = (0.35,0.46,0.56,0.64,0.68,0.69,0.65,0.57,0.45).

 6) The safety factor used to determine the weighted average method, that is to take the bk (k = 1,2, ..., p) for the weights, nk (k = 1,2, ..., p) the weighted average value of the safety factor n The value of: n = (pk = 1bknk) / pk = 1bk (2) calculated n = 1.62, according to the alternative set of data obtained n = 1.6. After mechanical calculation, the maximum stress is less than the longitudinal profile of the allowable stress, bending strength are met.

3.2 Other Design

Hydraulic and transmission design, including hydraulic cylinders and hydraulic motor parameter calculation, deceleration devices, design, fine-tune the design of institutions and other components, including fine-tune the horizontal movement of the screw design, the dovetail slot and half board design, the choice of wire rope and pins and checking and so on. Due to space constraints, they are to be introduced in another paper the design calculations, I will not explain.