JPS60247478A - Method for repairing stud bolt of boiler tube - Google Patents

Abstract

PURPOSE:To reuse a boiler tube having worn studs and to provide the satisfactory functions thereof by polishing the outside peripheral surface of said tube and welding the fresh stud bolts to the polished surfaces by a capacitor type welding machine. CONSTITUTION:A refractory material 4, etc. clad on the boiler tube 1 are first washed away when the many studs 3 projected on the surface of the tube 1 are worn. The space 5 parts among the studs 3 on the surface of the tube 1 are then polished. The new studs 6 are pressed to such polished surface and are welded by the welding machine of a capacitor type. The new studs 6 and the spaces 5 of the tube 1 are instantaneously welded and therefore no thermal stress strain generates in the boiler tube body 2. The sure regeneration of a required number and length of the studs is made possible without being affected by the remaining studs according to the above-mentioned repair method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for repairing stud bolts of a boiler tube when they are burnt out during operation.

The boiler tube has many stud bolts (
Hereinafter, it will simply be referred to as a stud. ) is installed protrudingly.

When the boiler tube is used on the furnace wall facing the inside of the furnace or around the burner, this stud improves the envelopment with the refractory material and heat conductivity, and protects the tube body from fuel liquid, combustion gas, etc. have However, the studs burn out and are destroyed during operation, and are no longer able to fulfill their role.The length of the studs decreases by about half in 3 to 5 years, depending on the frequency of use and other factors, and can become more severe depending on the usage environment. In some cases. This is particularly noticeable in recovery boilers whose main fuel is chip black liquor. Conventionally, in such cases, when the wall thickness of the boiler tube decreases due to the end of the life of the stud, the boiler tube itself is replaced with a new one, but this has the disadvantage of causing a large economic loss. In addition, as a countermeasure to this, it is possible to regenerate the stud by repairing it. For example, one example is to polish the shortened tip of the stud to a specified length and weld a new stud to the tip. However, with this method of adding studs, the cost and construction time of polishing to the specified length increases, and cavities may form in the polished stud bolts, making it difficult to weld. There were drawbacks.

In view of these conventional drawbacks, the present invention provides a method for repairing the studs of a boiler tube, which has a plurality of studs protruding from the outer circumferential surface at regular intervals, when they are burnt out due to use. The outer peripheral surface of the boiler tube located in the gap is polished by sandblasting or the like, and then a new stud is pressed against the polished surface and instantly welded using a condenser type stud welding machine, thereby making it possible to reuse the boiler tube. At the same time, it can be reliably regenerated to a state where it can fully perform its initial functions.

An embodiment of the repair method of the present invention will be specifically described below. FIG. 1 shows the boiler tube before repair, and the boiler tube 1 has already become considerably short due to wear and tear on the numerous studs 3, 3, etc. protruding from the outer peripheral surface of the tube body 2. Reference numeral 4 indicates a refractory material etc. attached to the outer periphery of the boiler tube l. In order to repair this, the boiler tube 1 is first washed with hot water in order to remove the refractory material and the like that have adhered to it. Hot water washing is performed in hot water that is sprayed out at high pressure by a water jet.
In this way, the refractory material adhering to the surface is washed away. Next, the surface of this boiler tube 1 is polished. The polishing is performed by sandblasting or the like, and in particular, the outer surface of the tube body 2 located in the gap 5 is polished. After that, a new stud is pressed onto this polished surface and welded using a capacitor type welding machine. Here, a capacitor type welding machine is a welding machine that instantly discharges the electricity stored in a large-capacity capacitor built into the welding machine to weld the new stud 6 and the gap 5 of the boiler tube, but only instantaneously. The temperature of the welded part hardly rises, so no thermal stress distortion occurs in the boiler tube body. Figure 2 shows the boiler tube that has been repaired, and 6 is the new stud.

However, since the repair method of the present invention involves welding a new stud 6 into the gap 5, the remaining stud 3
To reliably reproduce the required number and length of studs without being affected by the presence of nests, etc. Further, unlike arc stud welding, which is a conventional welding method, there is no risk of punching out the tube body 2.

As shown in Figure 3, the new stud 6 can be welded into narrow gaps between existing studs by processing the welding end into a slightly tapered conical shape. As explained above, according to the boiler tube stud bolt repair method according to the present invention, new studs can be reliably regenerated at low cost and in a short construction period, regardless of the presence or absence of residual stud nests, etc. Boiler tubes can be reused to fully demonstrate their intended function.

Therefore, there is a great economic advantage in making boiler tubes reusable through repair.

[Brief explanation of the drawing]

The drawings are shown to explain the boiler tube stud bolt repair method according to the present invention, and FIG. 1 is an external perspective view of the boiler tube before repair, and FIG. 2 is an external perspective view of the boiler tube after repair. , FIG. 3 is an enlarged perspective view of the new stud to be welded. ■...Boiler tube, 3,3...Stud pole 1-15...Gap, 6,6...New stud. Patent applicant Hidetake Washimi Patent attorney Takeshi Ito: (-117, Figure 1 1 2N Figure 8

Claims (1)

[Scope of Claims] 1. In repairing the stud bolts of a boiler tube, which has a plurality of stud bolts protruding from the outer peripheral surface at certain intervals, when they are burnt out due to operation, the above-mentioned Polish the outer peripheral surface of the boiler tube located in the gap,
Thereafter, a new stud bolt is pressed onto the polished surface and instant welded using a condenser type welding machine. d. The method for repairing a stud bolt of a boiler tube as set forth in claim 1, wherein the end of the new stud bolt on the side to be welded to the boiler tube is processed into a slightly tapered conical shape.