When operating a spiral plate heat exchanger, the pressure between adjacent channels is often different, and the pressure difference on both sides is the load acting on the spiral plate. When the curvature radius of the spiral plate is much larger than the spacing between the fixed distance columns, calculating the stress and displacement of the spiral plate is simplified as a bending problem of a plate supported by a series of points, and then the strength and stiffness calculation formulas are modified according to the characteristics of the spiral plate.

(1) Spiral plate: The spiral plate is subjected to both internal and external pressure, and its internal pressure strength and external pressure stability need to be considered. A spiral plate supported by a fixed distance column will lose stability when the critical pressure is reached on the convex surface under compression. The instability of the spiral plate will result in the following adverse consequences: local narrowing or even blockage of the spiral plate channel, and a sharp increase in resistance; Under repeated internal and external pressure, the spiral plate cracks; The large deformation caused by the instability of the spiral plate affects the end of the heat exchanger, resulting in the failure of the end face seal. The calculation pressure for spiral plate verification should be based on the most stringent working condition, which is the maximum possible pressure difference. Unless it can be ensured that the pressure difference between the two channels of the equipment is not greater than a certain value throughout the entire process, this value can also be used as the calculation pressure.

(2) Fixed distance column: Fixed distance bubbles can be used instead of fixed distance columns. The use of fixed distance bubbles will reduce stress concentration and make stress distribution more uniform. Its disadvantages are large curvature and poor stiffness.

(3) Inner ring plate and support ring: Generally, the thickness of the inner ring plate should not be less than that of the spiral plate, and if necessary, a thickened transition section can be used. The inner ring plate is subjected to both internal and external pressures. When checking the external pressure, it is necessary to consider whether the inertia moment of the support ring meets the minimum inertia moment requirement, in order to strengthen the calculation and reduce the length of the external pressure.

The manufacturing process of spiral plate heat exchangers is roughly as follows: layout, cutting, splicing, non-destructive testing, welding of distance columns, rolling of spiral bodies, welding of spiral channels, assembly, metal processing, final assembly, pressure testing, post-treatment, and final product delivery.

During the manufacturing process, the following points are worth noting:

(1) Spiral plate: Defects on the surface of the spiral plate, such as hard bending waves, sickle bends, and the quality of the cutting edge (usually gas cutting in China), have a significant impact on the rolling of the spiral body. The butt welds of the spliced board should undergo 100% radiographic or ultrasonic testing, and must use a full penetration structure. The excess height of the butt welds should be ground flat in a timely manner to prevent the board surface from warping and stress corrosion during use.

(2) Fixed distance column: It is important to have a chamfer of 1-2X45 ° at one end of the fixed distance column, because there are many fixed distance columns and the surface of the spiral plate cannot be completely flat. When spot welding the fixed distance column and the spiral plate, it is inevitable that a few fixed distance columns will be skewed. If there is no chamfer around it, it is easy to cut the spiral plate; The height deviation of the fixed distance column should be a positive deviation of 0-0.3mm, because if there is a negative deviation in the processing of the fixed distance column, when the spiral body is rolled and formed, the fixed distance column cannot be effectively adhered to the spiral body, and even rows of fixed distance columns do not support the spiral plate, weakening the role of the fixed distance column in enhancing the strength and stiffness of the spiral body; Due to the thinness of the spiral plate, special attention should be paid to controlling the welding quality during spot welding between the distance column and the spiral plate to ensure that the spiral body does not fall off during rolling. Attention should be paid to avoiding biting of the plate surface during arc initiation and termination. After spot welding the distance column, defects must be carefully inspected and remedied in a timely manner to avoid trouble caused by leakage and maintenance after equipment completion.

(3) Round steel: The round steel used for sealing the end face of spiral plate heat exchangers is generally composed of several round steels connected to fill a spiral channel. The hard bends of the round steel should be straightened, and the surface rust should be removed; When the diameter of the round steel is greater than 14mm, its rigidity is relatively high, and the inner ring does not fit well with the membrane during the spiral rolling process. At this time, the annealing length of the starting end of the round steel should be greater than 500mm; Round steel can also be replaced by Flat noodles.

(4) Central partition: If the size of the central partition is too small, it will affect the welding quality with the spiral plate. If it is too large, it will increase the local resistance of the medium flow. The allowable deviation of its width should be strictly controlled, generally 0-1mm. The connection between the central partition and the spiral plate is an important safety hazard of the spiral plate heat exchanger and cannot be repaired. Therefore, it is necessary to control its welding quality well. In order to eliminate the damage of the weld caused by the periodic effects of loading and unloading, an improved central partition structure (5) can be used. Support ring: The tight fit between the support ring and the inner ring plate (center tube) plays a role in strengthening the strength and stiffness of the inner ring plate. In order to ensure their fit, the radius of the support ring is best made according to the measured inner diameter of the inner ring plate (center tube), with conditions. The support ring should be completely welded to the inner ring plate.