JPS5826481B2 - How to attach a thermocouple to a boiler tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION With the increase in the high temperature, high pressure, and capacity of power generation boilers, the operating conditions for boiler furnace wall tubes are becoming increasingly severe.

Especially in supercritical pressure boilers, the maximum heat load of the furnace is 4 to 5.
The metal temperature of the furnace wall tube becomes extremely high due to the fact that the pressure reaches as high as 105kr4/m''H, the tube wall thickness increases due to the ultra-high pressure, and the fluid temperature in the tube is originally high.

Therefore, in order to operate the boiler safely and efficiently over a long period of time, multiple thermocouples are usually attached to the inner side (flame side) of the furnace wall tube of a large-capacity boiler near the burner level. It is necessary to constantly monitor the metal temperature of the furnace wall tube.

The present invention relates to a method for attaching this thermocouple.

The conventional installation method is explained based on Figures 1 to 3.
First, in Figure 1, holes were made in two places, one in the furnace wall tube and the other in the web, the thermocouple was passed through the hole in the web and into the hole in the furnace wall tube, and the part of the thermocouple exposed to the inside of the furnace was covered with a cover plate. However, the heat flux is easily disturbed by the cover plate, and there are drawbacks such as requiring two steps to drill the holes.

Next, in Figure 2, a short tube is taken out from the furnace wall tube panel and a thermocouple insertion hole is formed by performing electric discharge machining with a special machine for arc discharge electrodes, but since a special machine is required, It has drawbacks such as being impossible to process and install on-site and requiring a long processing time (it takes 5 hours to drill a 3cIrL hole).

Furthermore, Figure 3 shows a short tube taken out from the furnace wall tube panel, a circumferential groove with a rectangular cross section cut, a thermocouple embedded, and fixed with silver solder. Since it requires a lot of work, it is impossible to install it on-site, and since the cover plate is installed around the entire circumference, there are problems such as changes in heat flux.

As mentioned above, the technical difficulties in generally attaching thermocouples to furnace wall tubes are: (1) Practical and economical pore processing method for inserting thermocouples into the wall of the furnace wall tube; (2) Predetermined method Technique for attaching thermocouples to the temperature measuring part with precision (3) Once attached to the furnace wall tube, thermocouple installation that functions reliably over a long period of time without burning or breaking depends on establishing the structure, etc. , traditional poetic forms did not necessarily satisfy all of the above conditions.

The present invention overcomes these conditions and provides a method for attaching thermocouples that can be carried out extremely easily without disturbing the factory manufacturing process of furnace wall tube panels. A drilled hole that linearly penetrates the inside of the furnace wall tube and the inside of the web is drilled near the side crown so that the other end opens on the outer surface of the web, and then the tip is located in the drilled hole near the open end. The present invention is characterized in that a thermocouple is inserted thereinto, and the open end of the drilled hole on the surface of the furnace wall tube is covered with the same material as the furnace wall tube.

To explain one embodiment of the method of the present invention with reference to the drawings, first, a furnace wall tube panel is manufactured by placing a large number of tubes side by side at equal pitches on a special stand in a factory, and then using a special electric arc welder to fill the gaps between the tubes with molten metal. are supplied to form a web sequentially, and finally a large fusion welded wall panel is constructed.

Next, a drilled hole for attaching a thermocouple in the chord direction is drilled in a predetermined tube, and the drilling process is as follows.

(1) After lightly polishing the outer surface of a given tube with sandpaper or the like to remove dirt, rust, etc., thoroughly clean it with acetone or the like.

(2) Apply an instant adhesive to the adhesive surface 4 of the drilled hole jig 1, press the drilled hole jig 1 to the outer surface of the tube, and bond them together.

At this time, place the reference mark 3 of the drill hole jig 1 on the crown part 1 of the iron pipe.
Set it to 3.

Note that several types of drilled hole jig 1 and the inclined surface α of the drilled hole guide hole 2 are manufactured in advance so as to correspond uniquely to the specifications of the furnace wall panel.

(3) Insert an aperture of the required diameter attached to the electric drill of the portapull 1 from the aperture insertion port 9 along the aperture hole guide hole 2 to form a straight through hole in the furnace wall tube 6 and the web 7.

The rear drilled hole jig 1 can be easily removed by tapping it lightly with a small hammer or the like.

(4) Next, the thermocouple is inserted through the thermocouple insertion opening 10 on the web 7 side along the conical hole 5, and the tip of the thermocouple is guided to a predetermined temperature measuring section 8.

Note that the position of the thermocouple tip at this time can generally be determined with high precision using a relatively simple instrument.

(5) Also, a stuffing material 12 made of the same material as the tube is inserted into the opening of the drilled hole 5 on the tube side and fixed to the tube surface by electric arc welding.

When the fusion welded wall panel with thermocouples attached as described above is assembled into the boiler furnace wall during boiler installation on site, the temperature measuring part 8 where the tip of the thermocouple 11 is located is located inside the furnace, that is, on the boiler furnace wall. The thermocouple is facing the flame side, and the temperature measuring part 8 is slightly out of the crown part 13 of the furnace wall tube (deflection angle β in Fig. 5). is measured and a pre-prepared calibration value (established by experiment and theory).

), the true metal temperature of the crown portion 13 can be determined.

Conventionally, when attaching a thermocouple to a tube, the temperature measuring part 8 is placed on this crown part 13 or placed as close to it as possible, which makes the mounting technique and accuracy of the thermocouple difficult, and Although the durability of the thermocouple pair was not always satisfactory, these drawbacks were solved at once by the method of attaching the thermocouple of the present invention. Can be drilled in a straight line.

(2) Drilling work is quick and can be done in any location, regardless of the working environment, such as in a factory or on-site.

(3) Thermocouples can be directly attached to large furnace wall tube panels (no need to invert the panels), which greatly reduces the number of steps required to attach thermocouples.

(4) Since the drilled hole passes through the tube and the web in a straight line, the installation work of the chordal thermocouple is extremely simple.

(5) Since the thermocouple of the present invention does not come into contact with the flame inside the boiler, there is no risk of burnout or disconnection, and therefore the durability of the thermocouple is dramatically improved.

(6) Since there is no metal attached to the outer surface of the tube, the true tube wall metal temperature can be measured without disturbing the heat flux inside the tube.

This resulted in significant effects such as:

[Brief explanation of the drawing]

Figures 1 to 3 are sectional views and side views showing a known method for installing thermocouples of this type, and Figures 4 and 5 are views showing an embodiment of the method of the present invention, respectively, on a boiler tube before and after thermocouple insertion. FIG. 1...Drilled hole jig, 2...Drilled hole guide hole,
3...Reference mark, 4...Drilled hole jig adhesive surface, 5...Drilled hole, 6...Furnace wall tube, 7
...Web, 8...Temperature measurement department, 9...
... Cone insertion port, 10 ... Thermocouple insertion port, 11
...Thermocouple, 12... Packing machine, 13.
・・・・・・Crown part of the tube.

Claims (1)

[Claims] 11 After drilling a conical hole that linearly penetrates the wall of the furnace wall tube and the inside of the web so that one end opens near the furnace side crown on the furnace wall tube surface and the other end opens on the outer surface of the web, the tip A boiler tube characterized in that a thermocouple is inserted so that the thermocouple is located in the conical hole near the open end, and the open end of the conical hole on the furnace wall tube surface is covered with a material equivalent to the furnace wall tube. How to install a thermocouple on.