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Present Situation Of Production Technology Of Finned Tube
- Nov 09, 2018 -

Sets of fins: The set fin process is to pre-use a punch to process a batch of individual fins, and then by manual or mechanical methods, according to a certain distance high (wing distance), by the excess of the fin set on the outside surface of the pipe. It is one of the earliest methods used to process finned tubes. Because the package process is simple, the technical requirements are not high, the equipment used is low price, and easy to repair, so far there are still many factories in the adoption.

This process is a labor-intensive process scheme, suitable for the general small factory or township enterprises of the financial and technical conditions. A manual set is called a handmade suit. It is the use of tools, relying on the power of people to press the fins into one.

This method because the pressure force of the fin is limited, so the excess of the set is small, the fin is easy to produce loosening phenomenon. The mechanical set of fins is carried out on a fin set machine. Because the fin pressing is based on mechanical impact or liquid pressure, the pressure into the force is large, so, can be used a larger amount of excess. The bonding strength between the fins and the pipe is high and not easy to loosen. Mechanical transmission set machine production rate is high, but the noise is big, the safety is poor, the worker's working conditions are poor.

Although the hydraulic transmission does not exist the above problems, but the equipment price is more expensive, the use of maintenance personnel technical requirements are higher, its productivity is also lower.

Mosaic Spiral Fins: The mosaic spiral finned tube is a helical groove in which a certain width and depth are machined in advance on the steel pipe, and then the steel strip is inlaid on the steel pipe on the lathe. In the winding process, due to a certain preload, the steel belt will be tightly strangled in the spiral groove, thus ensuring that there is a certain contact area between the steel strip and the steel pipe. In order to prevent the steel belt rebound from falling off, the two ends of the steel belt should be welded on the steel pipe. In order to facilitate the mosaic, there should be a certain side gap between the steel strip and the helical groove. If the side gap is too small to form an excess, the mosaic process is difficult to proceed smoothly. In addition, the winding steel belt will always have a certain rebound, the result of which makes the steel belt and spiral groove bottom surface can not be very good bonding.

Mosaic fins can be carried out on general purpose equipment, the cost is not high, but the process is complex production efficiency is low.

brazing Spiral finned Tubes: The processing of brazing spiral finned tubes is carried out in two steps.

First, the steel strip plane is perpendicular to the pipe axis according to the spiral way winding on the outside surface of the pipe, and the steel strip at both ends of the welded pipe fixed, and then in order to eliminate the gap between the steel strip and the pipe contact, the steel strip and steel pipe are welded together by brazing method. Because of its high cost, this method is often used in another way, the pipe wrapped in the steel belt will be put into the zinc tank for the whole hot galvanizing to replace. The use of overall hot-dip galvanizing Although the plating solution is not necessarily very good seepage between the fins and the steel pipe between the very small gap, but on the outer surface of the fin and the surface of the steel pipe on the outside of the formation of a complete galvanized layer. The use of the overall hot-dip galvanized spiral fin tube, because of the thickness of the galvanized layer (galvanized layer thick, zinc layer firmness is poor, easy to fall off), coupled with zinc liquid can not all penetrate into the gap, so, the bonding rate of fins and steel pipe is still not high. In addition, the heat transfer coefficient of zinc is smaller than that of steel (about 78% of steel), so the heat transfer capacity is low.

Zinc is highly susceptible to corrosion in acids, alkalis and sulphides, so it is not suitable to make air preheater (recovery of waste heat from boiler flue gas) with galvanized spiral finned tube.

High frequency welded spiral fins: High frequency high frequency welded spiral finned tube is one of the most widely used spiral finned tubes, which is widely used in electric power, metallurgy, cement industry waste heat recovery and petrochemical industry. High frequency welded spiral finned tube is in the steel strip winding steel pipe at the same time, the use of high-frequency current skin effect and proximity effect, the steel belt and steel pipe outside the surface heating, until the plastic state or melting, in the winding steel belt under a certain pressure to complete the welding. This high frequency welding is actually a solid phase welding.

It is more advanced than Mosaic, brazing (or overall hot-dip galvanizing) and other methods, whether in terms of product quality (high bonding rate of fins, up to 95%), or degree of productivity and automation.

Three-roll oblique rolling integral spiral finned tube: The production principle of the three-roll oblique rolling integral spiral finned tube is as: lining a core rod in the light tube, driven by the rotation of the roll blade, the seamless steel pipe through the pore cavity composed of the rolling groove and the core head on the outer surface of the processing of fins. The finned tube produced by this method is an organic whole because of the base tube and the outer fin, so there is no problem of contact thermal resistance loss, and it has high heat transfer efficiency.

Compared with the welding method, the three-roll oblique rolling method has the advantages of high production efficiency, low consumption of raw materials and high heat transfer rate of finned tubes produced. At present, the technology of three-roll oblique rolling integral spiral finned tube has been successfully applied to the finned for copper, single finned tube or composite finned tube of aluminum, or low finned tube of steel; steel monolithic finned tube is now seen as a low finned tube on the market, the whole type of high fin tube is mostly aluminum, copper and so on, generally cold rolling molding.