JPS6113560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device for a ventilated internal pressure-proof constant temperature oven.

The general structure of a conventional thermostatic chamber of this type is shown in FIG. That is, in this FIG. 1, 1 is a thermostatic chamber, 2 and 3 are its air supply and exhaust ports,
Reference numeral 4 denotes a first constant pressure valve connected to the air supply port 2, which is connected to a safety gas for instrumentation, such as an air source 5; and 6, an electromagnetic on-off valve connected to the exhaust port 3, which is opened to the atmosphere. has been done. Further, 7 is a heater that heats the inside of the tank to a constant temperature by applying electricity, and 8 is an internal pressure detector that detects the internal pressure of the tank.
At the same time, the electromagnetic on-off valve 6 is closed to prevent dangerous gas from entering through the exhaust port 3.

In the conventional constant temperature chamber with this configuration, the first constant pressure valve 4 sets the instrumentation safety gas to a predetermined pressure.
The inside of the constant temperature chamber 1 is kept at a predetermined pressure to prevent dangerous gases from entering from the outside. During operation, the surface temperature exceeds the limit surface temperature determined by the explosion class and ignition degree of the explosion-proof guidelines.For example, if a failure occurs in the instrumentation safety gas supply system, As the internal pressure decreases, external dangerous gases may enter the interior through the exhaust port 3, creating a risk of explosion.
is inserted, and when the internal pressure detector 8 detects a drop in internal pressure, the power supply to the heater 7 is stopped and at the same time, this electromagnetic on-off valve is closed.

However, in such a configuration, the provisional exhaust port 3
Even if the thermostatic chamber 1 itself is closed, the purpose of explosion protection cannot be achieved if there is a leakage part in the thermostatic chamber 1 itself.Therefore, it is necessary to provide a complete sealing property to the constant temperature chamber 1 itself, and the structure for this purpose is Not only was it extremely complicated, but it also lacked reliability.

In view of this conventional situation, this invention maintains the inside of the tank at a predetermined pressure by automatically supplying auxiliary safety gas into the tank from a separate auxiliary safety gas source when the internal pressure drops. This makes it possible to prevent the infiltration of dangerous gases, etc.

Embodiments of the protection device according to the present invention will be described in detail below with reference to FIGS. 2 and 3.

In each of these figures, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. First, in the embodiment shown in FIG. 2, the exhaust port 3 is directly opened to the outside, and the reference numeral 10 is connected to the first constant pressure valve 4, so that when the controller 9 stops energizing the heater 7, the main pipe An electromagnetic three-way valve 11 is controlled to close the auxiliary pipe and open the auxiliary pipe.
A second constant pressure valve 12 is connected between the main pipe of the three-way valve 10 and the instrumentation safety gas source 5, and a third constant pressure valve 12 is connected between the auxiliary pipe of the three-way valve 10 and the auxiliary safety gas source
The constant pressure valve 14 is a check valve connected in parallel with the electromagnetic three-way valve 10 between the first and second constant pressure valves 4 and 11.

Therefore, in the configuration of the embodiment shown in FIG. 2, first, upon starting, the main line of the electromagnetic three-way valve 10 is closed, and the constant pressure valve 12 of the auxiliary safety gas source 13 is also in a state of being manually closed. In this state, the safety gas from the instrumentation safety gas source 5 is transferred to the second constant pressure valve 1.
1, the air is supplied into the thermostatic chamber 1 from the air supply port 2 via the check valve 14 and the first constant pressure valve 4, which is preset to a predetermined pressure. And this tank 1
When the inside of the tank 1 reaches a predetermined pressure, the internal pressure detector 8 detects this and activates a relay (not shown) in the control unit 9, which energizes the heater 7 to heat the inside of the tank 1 to a predetermined temperature. By controlling the three-way valve 10 to open its main pipeline and close its auxiliary pipeline, the instrumentation safety gas flows in the direction of the solid arrow through the main pipeline of the electromagnetic three-way valve 10, maintaining the inside of the tank 1 at a predetermined pressure. and then manually opens the third constant pressure valve 12, which was initially closed, and connects it to the auxiliary safety gas source 1.
Set the safety gas from 3 to reach a predetermined pressure, and operate continuously in this state.

However, in the steady operating state, if the internal pressure of the thermostatic chamber 1 drops for some reason, the internal pressure detector 8 detects this internal pressure drop, and the controller 9 accordingly controls the heater 7. When the power supply is stopped, the electromagnetic three-way valve 10 is controlled to close the main line and open the auxiliary line, so that in this case, the instrumentation safety gas can only flow through the check valve 14, and instead This time, the safety gas from the auxiliary safety gas source 13 will be continuously supplied into the thermostatic chamber 1 through the auxiliary pipe line of the electromagnetic three-way valve 10, and the pressure within the thermostatic chamber 1 will be maintained at a predetermined level without change. Something happens.

In addition, at this time, the auxiliary safety gas side and the instrumentation safety gas side are cut off by the check valve 14, so that the auxiliary safety gas does not flow into the instrumentation safety gas side, and the exhaust port 3 is provided with a check valve. 3a may be arranged to prevent backflow from the outside. Furthermore, the amount of gas in the auxiliary safety gas source 13 is such that after the power supply to the heater 7 is stopped, the inside of the tank 1 is kept for a sufficient period of time to cool the surface temperature of the heater 7 to the explosion-proof specified temperature. It is necessary to maintain the pressure at a predetermined level or higher.

Further, in the embodiment shown in FIG. 3, the electromagnetic three-way valve 10 is replaced with a normal electromagnetic valve (two-way valve) 1 in the embodiment shown in FIG.
0a, the main line of the instrumentation safety gas source 5 and the auxiliary line of the auxiliary safety gas source 13 are separated and are operated in the same way.

As detailed above, according to the present invention, in a ventilated internal pressure explosion-proof thermostatic chamber, the safety gas supplied into the chamber drops below a predetermined pressure, and the internal pressure detector detects this and energizes the heater. At the same time as the tank is stopped, safety gas is automatically supplied into the tank from a separately prepared auxiliary safety gas source to maintain the internal pressure.
There is no risk of dangerous gases entering the tank from the outside, so the constant temperature tank itself only needs to be strong enough to withstand more than the specified internal pressure stipulated in the explosion-proof guidelines, and must be completely sealed. This method does not require a wall, which simplifies the structure of the thermostatic chamber, and has the advantage of providing a highly reliable device configuration at a low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the general configuration of a conventional ventilated internal pressure explosion-proof thermostatic chamber, and FIGS. 2 and 3 show ventilated internal pressure explosion-proof thermostatic chambers to which different embodiments of the device of the present invention are applied. FIG. 2 is an explanatory diagram showing a general configuration. 1... Constant temperature chamber, 2... Air supply port, 3... Exhaust port, 4,1
1 and 12...first, second and third constant pressure valves,
5... Safety gas source for instrumentation, 7... Heater, 8... Internal pressure detector, 9... Control unit, 10, 10a... Solenoid valve, 13
...Auxiliary safety gas source, 14...Check valve.

Claims (1)

[Claims] 1. A heater having an air supply port and an exhaust port to heat the inside of the tank to a constant temperature and an internal pressure detector are provided, and the inside of the tank is maintained at a predetermined internal pressure by instrumentation safety gas introduced from the air supply port, In the protection device for a ventilated internal pressure explosion-proof constant temperature oven, the control unit stops heating by the heater when the internal pressure detector detects a decrease in internal pressure, and the air supply port is connected to the air supply port through a check valve. A wearable safety gas source and an auxiliary safety gas source are connected to each other via a solenoid valve, and when a drop in internal pressure is detected, the solenoid valve is opened to introduce the auxiliary safety gas into the tank. Protective device.