KR20110019107A - Method for manufacturing fin tube in the process of making fin tube in order to recovery of wasted heat for boiler - Google Patents

Abstract

PURPOSE: A method for manufacturing a fin-tube for a waste heat recovery boiler, capable of rapidly welding a fin with a tube, is provided to improve welding quality by increasing welding accuracy and by preventing poor welding. CONSTITUTION: The outer surface of a long tube(T) made of one of carbon steel, P235GH, T11, T22, T23 and T91, is roughed. A fin-tube for a waste heat recovery boiler is manufactured by winding a strip type fin(F) along the outer surface of a tube by rotating the tube. The fin is made of carbon steel or T409. The fin is serrated type and keeps an inter-fin distance 8.38-8.81 inch.

Description

METHODS FOR MANUFACTURING FIN TUBE IN THE PROCESS OF MAKING FIN TUBE IN ORDER TO RECOVERY OF WASTED HEAT FOR BOILER}

The present invention relates to a fin tube manufacturing process for a waste heat recovery boiler, and more particularly, it is possible to weld a fin to a tube as fast and as long as possible in an appropriate condition when automatically combining a large number of fins arranged relatively narrowly outside the tube. It relates to a fin tube manufacturing method in the fin tube manufacturing process for waste heat recovery boiler.

In general, a heat recovery steam generator (Heat Recovery Steam Generator) is applied to improve heat efficiency in cogeneration plants and the like, which is referred to as "HRSG".

In general, when power is produced through a gas turbine in a power plant or the like, the temperature of the exhaust gas generates a high heat of about 200 to 550 degrees, which may be said to have a considerable amount of energy. If such exhaust gas is discharged to the outside as it is, there is a problem that a considerable amount of energy is lost. Waste heat recovery boiler systems are applied in power plants and other places to recover energy from the exhaust gas recently used for other purposes. .

The waste heat recovery boiler system generates steam by using exhaust gas to be discharged into the atmosphere, and the steam generated by the waste heat recovery boiler is used to generate electric power by driving a steam turbine.

The waste heat recovery boiler is provided with a plurality of heat exchangers to obtain steam through heat exchange from the exhaust gas of the gas turbine, and in this case, a fin tube having a zigzag shape is used.

Looking at the structure of the fin tube is a hollow tube, and a plurality of fins having a predetermined area on the outside of the tube is combined is applied. Here, the coupling of the fin to the tube is intended to increase the heat contact surface to increase the heat exchange efficiency.

The typical fin tube has a spiral finned tube method for improving productivity, and a fin is formed by a heat exchanger in which a band-shaped fin is formed on the outer circumferential surface of the spiral fin tube to spirally form a fin. The advantage is that the process can be maintained continuously without disconnection.

However, there is a problem that wrinkles occur in manufacturing on the fins of the conventional spiral fin tube, and the wrinkles have a disadvantage of rapidly increasing the flow resistance of the air side passing through the heat exchanger. In addition, in order to reduce the contact resistance between the pin and the tube, or the pin welding, or the spiral surface treatment in the position where the pin is attached, there is a problem that the productivity is lowered than expected.

Accordingly, the productivity is greatly improved, the heat transfer area can be sufficiently secured, and a new type of heat exchanger that is advantageous in terms of flow resistance is required, and its production method and apparatus are urgently required.

In addition, the finned tube (Finned Tube) is a spirally wound pin is welded to the outside of the tube during manufacture, the tube is rotated slowly, and the belt-shaped pin drawn out from the uncoiler perpendicular to the tube in the tangential direction In the connected state, the electrode tip is brought close to the tube and the fin, and then a high frequency arc is generated at the contact portion of the tube and the fin to perform the welding operation through the generated arc heat.

In welding the fins to the tube as described above, stable welding is achieved only by vertically erecting the belt-shaped pins that are continuously transported and maintaining a predetermined gap from the tubes. Conventionally, there is no dedicated device for vertically standing the fins. Due to the temporary use of a device made in Korea, there has been a problem that the work is delayed and many welding defects occur.

In addition, the outer peripheral surface of the tube when the pin is coupled to the outside of the tube is treated with a rust preventive or smooth, there is a problem that welding is not easy when welding.

In order to solve this problem, the surface of the tube is polished with belt paper before welding the pin to the tube, but the performance is degraded and it is impossible to reuse it when the cost rises due to excessive consumption of the belt paper and disposal after use. Therefore, the problem of environmental pollution has been generated.

In addition, there is a problem that the working environment in the room is vulnerable due to excessive dust when working with the belt paper.

Therefore, the present invention was devised to solve the above problems, and an object of the present invention is to implement a mechanical welding condition most suitable for high frequency welding while spirally wound a pin on a tube, and to weld the surface of the tube to be welded through pretreatment of the welding wire. It is to provide a fin tube manufacturing method in the fin tube manufacturing process for the waste heat recovery boiler to improve the weld quality after welding to increase the durability, lower the flow resistance and increase the heat exchange area.

In order to achieve the above object, the present invention comprises the steps of roughing the outer surface of the pipe-shaped long tube; Finned tube for waste heat recovery boiler characterized in that it comprises a processing step of manufacturing a fin tube for waste heat recovery boiler by high frequency welding while spirally wound the strip-shaped pin on the outer surface while rotating the processed tube Provided is a method for manufacturing a fin tube in a manufacturing process.

In addition, the tube is made of any one selected from carbon steel, P235GH, T11, T22, T23, T91; The pin is also characterized by being made of either carbon steel or T409.

In addition, the pin is characterized in that it is a serated type (Serrated Type) to maintain the distance between the pins 8.38 ~ 8.81 inches.

In addition, in the processing step, the high frequency welding conditions are welding speed 500 ~ 1200m / min, high frequency welding output 100 ~ 200KW, input current 350 ~ 360A, anode voltage 9 ~ 13KV, anode current 15 ~ 25A, grid current 4.5 ~ 4.9 The feature is also A.

According to the present invention, it is equipped with a specific welding conditions according to the material when welding continuously while winding a thin strip-shaped pin spirally on the outer peripheral surface of the tube on the pipe to increase the precision, prevent welding failure, and improve the durability according to the improvement of welding quality It can raise fin tube for heat exchange more efficiently.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment according to the present invention.

1 is a schematic diagram of a fin tube according to the present invention, Figure 2 is a cross-sectional view of the main part according to the present invention.

As shown in Figure 1 and 2, the fin tube according to the present invention is utilized as a heat exchange means for waste heat recovery boiler that is being applied to improve the thermal efficiency in cogeneration plants and the like.

The fin tube according to the present invention is composed of a pipe-shaped tube (T), and a strip-shaped fin (F) that is high frequency welded while spirally wound along the outer circumferential surface of the tube (T).

A very important technical condition in the production of the fin tube used in the waste heat recovery boiler (HRSG) is how long the tube (T) in the longitudinal direction in order to improve the thermal efficiency than the general design product within a predetermined period. More pins F can be continuously welded at high frequency.

In order to produce a fin tube that requires such high production conditions, it is necessary to be able to weld the fin F to the tube T in a constant and vertical manner under mechanical operating conditions and high frequency welding conditions.

The present inventors have spent years researching on the above-mentioned conventional problems, and have succeeded in producing Serrated Type / 330 ~ 347Fins (8.38 ~ 8.81inch).

Fin tube manufacturing in the field of the present invention is a tube (T) which is a welding base material because it is manufactured by rotating the tube (T), which is a metal material at a constant speed, by the high frequency welding of a strip-shaped fin (F) in a spiral shape on the outer peripheral surface thereof. This is a difficult task because there are many factors scattered in the final quality such as the surface of the fin, the thickness of the fin F, the welding conditions, the rotational speed of the tube T, and the pitch of the spiral coil F. .

In particular, the fin (F) should be fused to the tube (T) under constant pressure, and the final quality of the high frequency welding machine for high frequency welding, the output, the welding speed, the separation distance from the welding point (W) to the energization point, etc. Is a very important factor that directly affects.

This is because the fins F released from the take-up rolls (not shown) on the outside of the tube T continuously rotated should be stably and automatically welded to the outer circumferential surface of the tube T.

At this time, the welding point (W) is the position of the tube (T) to which the pin (F) is attached, the conduction point refers to the position where the conductor of the high frequency welder is arranged for energization.

In the present invention, the distance between the fins (F), that is, it is possible to manufacture the fin tube of the spiral automatic welding method having a pitch of 8.38 ~ 8.81 inches, mass production is easy, and the welding quality is excellent, durability is improved, and lower cost With the advantage of producing a large amount of fin tube.

To this end, the present invention first undergoes a material roughening step.

The roughing of the material refers to rough grinding of rough material, and as the material of the tube T, carbon steel, P235GH, T11, T22, T23, and T91 are suitable.

The outer surface of the material is slightly roughened to make it suitable for manufacturing a serrated type fin tube.

Thereafter, the processing step.

The processing step is a step of high-frequency welding while releasing the pin (F) wound on the take-up roll while rotating the heat-treated tube (T) continuously spiral wound around the outer peripheral surface of the tube (T), if necessary It can be divided into two stages.

At this time, the pin (F) to be welded to the outer peripheral surface of the tube (T) has a height of 13 ~ 19mm, thickness 0.8 ~ 1.0mm, the distance between the pin (pitch) 8.38 ~ 8.81 inch, segment width (3.8 ~ 4.4) Carbon steel or T409 is preferable as the material which is made of mm and constitutes the fin F.

In addition, the welding conditions are as follows.

First, welding speed is 500 ~ 1200m / min, high frequency welding output is 100 ~ 200KW, input current is 350 ~ 360A, anode voltage is 9 ~ 13KV, anode current is 15 ~ 25A, grid current is 4.5 ~ 4.9A. It must be maintained.

The reason for this limitation is that in the case of the serrated type pin tube welding method, the welding point becomes wider when the welding speed is 500 m / min or less, and the weldability decreases when the welding rate is over 1200 m / min. Since this may occur, it should be limited to the above range, because it is the most reasonable range in view of the tube (T) having the welding speed and the serrate type surface in the case of input current and welding voltage and current including the welding output.

Through this step, as shown in (b) of Figure 2, it is possible to complete a fin tube having a stable welding point (W).

Hereinafter, an Example is described.

Example 1

In order to confirm the welding conditions according to the present invention in the final step during the manufacturing step according to the manufacturing method described above, it was welded to the specifications and conditions shown in Table 1 below.

By the way, in the case of Example 1 shown in Table 1, the thickness of the squeeze roll (squeeze roll) was tested to 2.0mm as the conventional one, but the weldability defect due to the high frequency leakage phenomenon due to the narrow distance between the pin and the pin It was also confirmed that the welding failure was aggravated because the speed (RPM) was too fast.

The squeeze roll is assembled in a pair of male and female and is positioned between the pin and the pin to serve to raise the pin vertically. It also prevents heat from conducting and dissipating during high frequency welding, and also allows the fins to adhere closely to the tube surface.

[Example 2]

In order to confirm the welding conditions according to the present invention in the final step during the manufacturing step according to the manufacturing method described above, the welding was carried out in the specifications and conditions as shown in Table 2.

In the case of Example 2 shown in Table 2, the thickness of the squeeze roll (Squeeze Roll) was changed to 2.0 ~ 1.5mm for the purpose of improving the high frequency leakage phenomenon was tested.

However, since the thickness dimension was thinned to 1.5 mm, high frequency welding itself was impossible due to deformation caused by the high temperature of the existing material (SCM4). And the speed was adjusted to 1200 or less.

Example 3

Based on the experience of Examples 1 and 2 above, welding was performed under the conditions shown in Table 3 below to find more accurate welding conditions.

In the case of Example 3 of the present invention tested under the conditions as shown in Table 3, the inventors satisfied all desired characteristics.

Through this, the serrate-type fin tube could be manufactured to have a more durable and high welding quality.

1 is a schematic diagram of a fin tube according to the present invention,

Figure 2 is a cross-sectional view of the main part according to the present invention.

♧ description of the symbols for the main parts of the drawing

T ... tube F ... pin

W .... welding

Claims (4)

Roughing a pipe-shaped long tube T outer surface consisting of any one selected from carbon steel, P235GH, T11, T22, T23, and T91; Waste heat recovery comprising a processing step of manufacturing a fin tube for waste heat recovery by high frequency welding while winding the strip (F) in a spiral shape on the outer surface while rotating the tube (T). Fin tube manufacturing method in the process of manufacturing fin tube for boiler. The method according to claim 1; The fin (F) is a fin tube manufacturing method in the fin tube manufacturing process for waste heat recovery boiler, characterized in that consisting of one of carbon steel or T409. The method according to claim 1 or 2; The fin (F) is a fin tube manufacturing method in the fin tube manufacturing process of the waste heat recovery boiler, characterized in that the serrate type (Serrated Type) to maintain the distance between the fins 8.38 ~ 8.81 inches. The method according to claim 1; In the processing step, the high frequency welding conditions are welding speed 500 ~ 1200m / min, high frequency welding output 100 ~ 200KW, input current 350 ~ 360A, anode voltage 9 ~ 13KV, anode current 15 ~ 25A, grid current 4.5 ~ 4.9A Fin tube manufacturing method in the fin tube manufacturing process for waste heat recovery boiler characterized in that.

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