JPH0641602B2 - Safety equipment in vacuum furnace - Google Patents

Description

The present invention relates to a safety device for a vacuum furnace that uses explosive gas.

(B) Conventional technology For example, for sintering cemented carbide, a method using an explosive gas such as H ₂ , CO, CH ₄ , C ₃ H ₈ as an atmosphere gas has been proposed in recent years and spread. I am doing it. However, since this sintering work is usually carried out in a vacuum heat treatment furnace under an appropriately reduced pressure, if an unexpected leak occurs in the furnace due to a sudden leak or seal deterioration, the explosion will occur. There is a risk of air being mixed with the volatile gas and causing an explosion accident. For this reason, in the sintering method using this kind of explosive gas, establishing the safety measure of the vacuum heat treatment furnace is the most technical issue.

(C) Purpose The present invention has been made to solve such a problem, and immediately detects an abnormality such as a leak in a vacuum furnace used for sintering work, and immediately detects the abnormality, and It is an object of the present invention to provide a safety device capable of automatically taking appropriate safety measures immediately.

(D) Structure That is, in order to achieve the above-mentioned object, the present invention receives detection means for detecting the pressure and oxygen ratio of the explosive gas in the vacuum furnace, and pressure and oxygen ratio information from this detection means. In addition, the control means configured to output a danger signal when the in-furnace pressure and the oxygen ratio reach or close to the respective explosion limit ranges set according to the operating conditions, and a danger signal from the control means. And adjusting means for adjusting the gas exhaust system and / or the inert gas introduction system in the furnace.

(E) Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a system of a safety device according to the present invention, in which a vacuum furnace 1 for heat treatment, especially for sintering, is connected to a gas supply device (not shown) via a valve 2 in a gas introduction passage a. The following systems are installed inside and outside the furnace. The vacuum furnace 1 is provided with a pressure sensor 3 as one of pressure detecting means for detecting the pressure of the explosive gas sealed in the furnace in a reduced pressure state. The vacuum furnace 1 is also provided with an O ₂ sensor 4 as one of oxygen ratio detecting means for detecting the oxygen ratio in the explosive gas. The pressure sensor 3 and the O ₂ sensor 4 independently transmit pressure information and oxygen ratio information to the control means described below via converters 5 and 6 for converting the detection results into electric signals.

The control means 7 receives these information and
Necessary conditions such as the type of gas used and the volume of the furnace are input, and the explosion limit pressure and the explosion limit ratio, which are respectively set according to the operating conditions of the vacuum furnace 1, are stored in the storage part thereof. Here, the explosive limit pressure refers to the upper or lower pressure limit of the pressure range in which various explosive gases are inherently practicable in a depressurized state. For example, in the case of H ₂ gas, it is possible to explode from atmospheric pressure to about 600 Torr and in a pressure range of about 40 Torr or less, and in the intermediate pressure range, it is not possible to explode regardless of the oxygen mixture ratio. This is mainly due to physical reasons related to flame propagation velocity. Therefore, when H ₂ gas is used as the explosive gas, each of the above pressures may be stored as the explosive limit pressure. The set pressure of is stored. In addition, the explosive limit ratio refers to the ratio of the upper limit or the lower limit of the oxygen ratio at which each of the various explosive gases has a unique explosive potential. For example, in the case of H ₂ gas, it is possible to explode in the range of 5 to 75% of H ₂ (mixing ratio with air), and it is not possible to explode if the amount of H ₂ gas or oxygen is excessive or insufficient. Therefore, in this case, the ratio calculated from the above ratio or the set ratio in the vicinity thereof may be stored as the explosion limit ratio. Since it is not normally expected that the oxygen amount exceeds the upper limit ratio, only the lower limit ratio may be used.

Then, the control means 7 compares and calculates the pressure information and the explosion limit pressure in the calculation part, and the furnace pressure transmitted by the pressure information rises from the control pressure to the explosion upper limit pressure or a set pressure in the vicinity thereof. If the internal pressure drops to the explosion lower limit pressure or the set pressure in the vicinity of the explosion lower limit pressure, the dangerous signal P1 is output to the pressure adjusting means to be described later. Is configured.

Further, the control means 7 also performs a comparison calculation of the oxygen ratio information and the explosion limit ratio in the calculation part, and the oxygen ratio of the in-furnace explosive gas transmitted by the oxygen ratio information is at or below the lower explosion limit ratio. When the temperature rises to 0, the dangerous signal O is output to the oxygen ratio adjusting means described later from the output portion.

The pressure adjusting means is composed of a vacuum pump 8 and a gas reservoir 9 which are connected to the vacuum furnace 1 via electromagnetic valves 10 and 11, respectively. That is, the vacuum pump 8 performs a low pressure recovery adjusting function, and when the danger signal P1 is inputted, the electromagnetic valve 10 provided in the gas exhaust passage b is opened and rapidly operated to depressurize the furnace. On the other hand, the gas reservoir 9 performs a high pressure recovery adjustment function, and when the danger signal P2 is input, the electromagnetic valve 11 is opened and the gas supply path c is opened for a certain period of time so that N ₂ stored in the chamber is A high-pressure inert gas such as CO ₂ is immediately supplied to the vacuum furnace 1 to lower the degree of vacuum in the furnace.

Further, the oxygen ratio adjusting means is provided with a gas reservoir 9 attached to the vacuum furnace 1 via the electromagnetic valve 11 and an electromagnetic valve 12 provided in a discharge path d for discharging the gas in the furnace to the atmosphere.
It consists of a purging mechanism in the furnace constituted by. That is, the danger signal O is simultaneously input to the electromagnetic valve 11 on the side of the supply path c and the electromagnetic valve 12 on the side of the discharge path d to open both valves 11 and 12, and the inert gas is discharged from the gas reservoir 9 into the furnace. On the other hand, the gas in the furnace is expelled from the discharge path d into the outside air, and the oxygen ratio in the gas in the furnace is instantaneously reduced.

Next, the operation of the safety device having the above configuration will be described.

When the control means 7 receives the pressure information from the pressure sensor 3 and detects an abnormal fluctuation of the in-furnace pressure due to a leak or the like in its calculation part, as described above,
The dangerous signal P1 or P2 is output from the output portion, and appropriate safety measures are immediately taken. Explaining this in detail with reference to FIG. 2, it is assumed that a leak or the like occurs in the vacuum furnace 1 in a depressurization control state and the furnace pressure rises to a set pressure near its upper limit pressure as shown by an arrow Pup in the drawing. The control means 7 outputs a danger signal P1 from its output portion to the vacuum pump 8 and the electromagnetic valve 10. Then, the vacuum pump 8 moves the vacuum furnace 1 under the open condition of the valve 10.
The atmosphere gas inside is sucked and the furnace pressure is rapidly lowered as shown by the arrow Pdown in the figure to restore the original furnace pressure.
Although not shown in the figure, on the contrary, when the pressure in the furnace drops to a set pressure near its lower limit pressure by mistake, the danger signal P2 is sent from the control means 7 to the electromagnetic valve 11.
Is output and the inert gas is supplied from the gas reservoir 9 to restore the original furnace pressure. As described above, in this safety device, even if an abnormality such as a leak occurs, the in-furnace pressure is reliably maintained within a depressurized pressure range in which the explosive gas cannot physically explode. There is no danger of explosion and safety can be secured.

Further, if the control means 7 receives the oxygen ratio information from the O ₂ sensor 4 and detects an abnormal increase in the oxygen ratio of the explosive gas in the furnace due to a leak or the like in its calculation part, As described above, the danger signal O is output from the output part.
Is output to operate the in-furnace purging mechanism to rapidly release the explosive gas to the outside and replace the inside of the furnace with the inert gas, thereby eliminating the danger of explosion.

The safety system based on the oxygen ratio adjusting means for the in-furnace explosive gas operates independently from the safety system based on the pressure adjusting means, and further ensures the safety of the vacuum furnace 1.

As the pressure detecting means and the pressure adjusting means used in the safety device of the present invention, in addition to those mentioned in the embodiments, various mechanisms can be adopted. The control means 7 may have any internal system configuration as long as it has the necessary information processing function and command output function.

(F) Effects As described above, the safety device of the present invention is provided with the pressure detecting means, the control means, and the pressure adjusting means under a predetermined coupling state, and the explosive gas of the vacuum furnace is always constant. Since the pressure is maintained within the non-explosive pressure range, the risk of an explosion accident can be prevented even if an abnormality such as a leak occurs in the vacuum furnace. Further, since the safety of the vacuum furnace is secured, the sintering method using the explosive gas can be widely carried out without any trouble.

[Brief description of drawings]

FIG. 1 is a system explanatory view showing an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an example of an operation mode of the embodiment system. 1 ... vacuum furnace 2 ... valve 3 ... pressure sensor 4 ... O ₂ sensor 5,6 ... converter 7 ... control unit 8 ... vacuum pump 9 ... gas reservoir 10, 11, 12 ... electromagnetic valve a ... gas introducing path b ... Gas discharge path c ... Gas supply path d ... Gas discharge path P1, P2, O ... Danger signal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Nishimoto 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto-shi, Shimadzu Corporation Sanjo Plant (72) Inventor Chian Kawasaki Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto Company Shimadzu Sanjo Factory (72) Inventor Masao Takeda 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto-shi, Kyoto Shimazu Corporation Sanjo Factory

Claims (1)

[Claims] 1. A detection means for detecting the pressure and oxygen ratio of an explosive gas in a vacuum furnace, and the pressure and oxygen ratio information from this detection means are received, and the furnace pressure and oxygen ratio are operating conditions. Control means configured to output a danger signal when the explosion limit range is set to or near each of the explosion limit ranges set in accordance with the above, and the danger signal from the control means is input to the gas exhaust system in the furnace and / or A safety device in a vacuum furnace, comprising: an adjusting means for adjusting an inert gas introduction system.