JPS5932877B2 - Sea heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a red-hot, high-temperature sheathed heater, and an object of the present invention is to improve safety in the event of wire breakage during the life of the sheathed heater.

Generally, as shown in Figure 1, a sheathed heater has a heating coil 1 with terminal rods 2 connected to both ends for power extraction, placed in the center of a pipe 3, and filled with insulating powder to electrically insulate both. 4, and both end portions are moisture-proofed with a sealant 5.

When this sheathed heater is used for a long time, the air inside is consumed by the heating coil 1 or the pipe 3, and the electrical insulation and withstand voltage gradually deteriorate with use, eventually causing wire breakage. There are two patterns of disconnection in this sheathed heater, one in which only the internal heating coil 1 is disconnected, and the other in which the pipe 3 is also fused at the same time as the heating coil 1 is disconnected, resulting in a very dangerous disconnection condition. The latter disconnection mechanism is similar to the previous one, as the heating coil 1, pipe 3, and insulating filling powder 4 deteriorate after long-term use, causing a part of the heating coil 1 to abnormally heat up, causing that part to become damaged. It has been confirmed that the insulating filling powder 4 and the pipe 3 reach an abnormally high temperature of 2800°C or more at the same time, causing the pipe 3 to melt, which not only creates a very dangerous situation, but also in some cases (
It has the disadvantage that it can even lead to a fire. It has been confirmed that this pipe melting occurs when the temperature of the pipe becomes abnormally high. This phenomenon becomes more pronounced as the operating temperature increases. The present invention solves the above-mentioned drawbacks, and includes:
An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 2, 11 is a heating coil, 12 is a terminal bar, and 13 is a heating coil.
1 is a metal pipe, 14 is an insulating filling powder, 15 is a sealant, 1
6 is a metal tube, IT is an alumina molded body, and constitutes a sheathed heater.

To explain in more detail, the heating coil 11 has a wire diameter of 0.
Using a 5-layer wt nichrome wire, stainless steel terminal rods 12 with a diameter of 2 mm are connected to both ends by spot welding, placed in the center of a pipe 13 made of heat-resistant and corrosion-resistant steel, and filled with insulating filler powder 14 of magnesia. do.

When filling the insulating filler powder 14, first fill the insulating filler powder 14, leaving the filling for the length of the alumina molded body IT, insert the alumina molded body 17 from the terminal rod 12, and then fill the insulating filler powder 14. The filling takes the form of a sandwich. After that, the diameter is reduced by rolling to increase the packing density and dehumidified, and then both ends are sealed with a sealant such as glass.
5 to make it moisture-proof. Alumina molded body 1? The size of the pipe 13 and the outer diameter of the heating coil 11 allow easy insertion, and the outer diameter is 6.5 m77! , a cylindrical one with an inner diameter of 3.5 mm and a length of 10 mm is used. To describe the characteristics of this sheathed heater, at the rated time, the part 1 having the alumina molded body 17 in the heating coil 11
The linear temperature difference between the portion 1b and the other portion 11a is about 100° C., and the portion 11b having the alumina molded body 17 is higher.

At the same time, the surface temperature of the pipe 13 at this time is about 800°C in the part 13a without the alumina molded body, while the surface temperature in the part 13b with the alumina molded body 17 is about 8700°C.
It will be about C. Regarding these temperature relationships, the temperature difference tends to increase as the power consumption increases, and if this continues, the temperature of the pipe in the portion 13b having the alumina molded body will further rise, causing the pipe to melt at that portion. Therefore, in order to further improve the adhesion, a stainless steel metal tube 16 having a length of about 10 mm and a wall thickness of 2 mm that matches the outer diameter of the pipe 13 is inserted into the portion 13b having the alumina molded body 17 as shown in the figure. The edges are caulked. After caulking, when the temperature of the part 13b with the alumina molded body 17 is measured, the temperature drops to about 800 due to the heat dissipation effect of the metal cylinder 16, and the pipe 13 does not melt and only the part 11b of the heating coil 11 with the alumina molded body 17 is measured. There was a break in the wire. Furthermore, the disconnection life of the sheathed heater is controlled by the temperature of the heating coil 11, and it goes without saying that the higher the temperature, the faster the disconnection will occur.
After carrying out step 6, the temperature of the part 11b with the alumina molded body in the heating coil 11 is only about 50°C higher than that of the other part 11a, so the lifespan of this sheathed heater is the same as that of the conventional product. level. Although an alumina molded body was used in the above example, a molded body of a composite of heat-resistant inorganic insulators that is stable at high temperatures may also be used.Furthermore, the heat capacity of the metal pipe may not exceed 850°C. Depending on the situation, it may not be necessary. As described above, the sheathed heater of the present invention is made by inserting a heat-resistant inorganic insulator molded body such as alumina molded body into a part of the heating coil so that the temperature becomes higher than other parts, and a pipe part corresponding to that part is formed. 85
``By suppressing the temperature by dissipating heat below C, we were able to create a sheathed heater that does not cause pipes to melt.

In addition, it is possible to provide a sheathed heater that is simple, inexpensive, and highly safe, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway sectional view of a conventional sheathed heater, and FIG. 2 is a partially cutaway sectional view of a sheathed heater showing an embodiment of the present invention. 11...Heating coil, 13...Metal pipe, 14...Insulating filling powder, 16...
・Metal tube, 17...Alumina molded body.

Claims (1)

[Claims] 1. A sheathed heater in which a metal pipe into which a heating coil is inserted is filled with insulating filler powder, in which a part of the metal pipe is provided with heat radiation means for suppressing a temperature rise to 850 degrees or less, and this heat radiation means is A sheathed heater made by inserting a heat-resistant inorganic insulating molded body between a metal pipe and a heating coil. 2. The sheathed heater according to claim 1, wherein the heat-resistant inorganic insulating molded body has a lower thermal conductivity than the insulating filler powder.