JPS6129615A - Fuel gas cutting device - Google Patents

Abstract

PURPOSE:To keep a safe repairing operation by a method wherein a nitrogen gas distribution pipe for supplying nitrogen gas is arranged between a gas flow rate control pipe arranged at a branch pipe and a gas cutting valve through a pressure adjusting valve and the nitrogen gas pressure is restricted in response to the ignited gas pressure. CONSTITUTION:A cutting valve 15 in a nitrogen pipe 9 is opened in case of performing a regular repairing operation to supply nitrogen gas and the fuel gas between a flow rate control valve 4 and a near valve 7 is purged through a dispersion pipe 11. Upon completion of purging, the cutting valve 5 and the releasing valve 10 are closed and the nitrogen gas is enclosed between the flow rate control valve 4 and the closing valve 5. The pressure adjusting meter 14 is set to a pressure higher by P than the enclosing pressures P2 and P1 of nitrogen between the flow rate control valve 4 and the closing valve 5 in response to the pressure signal P1 in a pressure signal transmitter 13a in a gas main pipe 1 and at the same time the pressure adjusting valve 12 is controlled in such a way as a relation of P3=P2 may be attained in response to an actual nitrogen gas pressure signal P3 got from the pressure signal transmitter 13b.

Description

[Detailed description of the invention] (Fields of use of the craft) The present invention provides a heating furnace in which fuel gas is branched from a main pipe.

This invention relates to a fuel cut-off device when the furnace operation is stopped, which is installed in a branch pipe installed to supply to general industrial furnaces, etc.

(Prior Art) Steel factories and the like handle large amounts of fuel gas, and the fuel used in various heating furnaces, general industrial furnaces, etc. is supplied through branch pipes branched from the main fuel pipe.

FIG. 2 is an explanatory diagram of a conventional fuel gas cutoff device. As shown in the figure, the fuel gas piping system includes a fuel gas main l through which fuel gas such as blast furnace gas and coke gas flows;
Gas branch pipe 2 that branches from the main pipe 1 and supplies fuel to the heating furnace
and an orifice 3 for measuring the amount of gas flowing through the gas branch pipe 2.
, a flow rate control valve 4 that controls the amount of gas, a cutoff valve 5 that cuts off the flow of gas, a burner 8 attached to the heating furnace, a burner hand valve 7, and an air pipe that supplies combustion air to the burner 8. Further, a nitrogen pipe 9 for purging the fuel gas in the gas branch pipe 2 is connected to the gas branch pipe 2 between the cutoff valve 5 and the burner hand valve 7. A shutoff valve 15 is installed between the nitrogen pipe 9 and the nitrogen gas source.
is provided.

Further, the fuel main pipe 1 is provided with a water seal valve 16 in preparation for periodic repairs. When the heating furnace is used, fuel gas flows into the branch pipe 2, the flow rate is measured by the orifice 3, the flow rate is controlled by the flow control valve 4, passes through the shutoff valve 5 and the hand valve 7, and then flows into the burner 8.
The combustion air 6 causes combustion.

When performing work such as repairing bricks inside heating furnaces during periodic repairs, etc., there is a risk of explosion if flammable gas is present in the furnace. It is necessary to prevent leakage into the furnace. Therefore, when performing periodic repairs, manually close the burner hand valve as well as the combustion gas system control valve and cutoff valve, and if necessary, shut off the fuel gas main pipe 11 with the water seal valve 16.
Prevent fuel gas from flowing into the furnace. In the fuel gas branch pipe 2, first, the flow control valve 4 and the cutoff valve 5 are closed, and with the hand valve 7 open, the cutoff valve 15 of the nitrogen pipe 9 is opened.
The fuel gas between the cutoff valve 5 and the burner 8 is purged to the furnace side, and then the cutoff valve 15 and the hand valve 7 are closed to seal in nitrogen gas between them to prevent fuel gas from entering the furnace.

(Problems to be Solved by the Invention) However, when the water seal valve 16 is used, the water seal valve must be closed manually, and a large-scale gas supply operation is required when starting up after regular repairs. If it is not a major repair of the fuel gas system, use the cutoff valve of branch pipe 2.

Gas is shut off by closing only the control valve, but since the flow rate control valve 4, shutoff valve 5, and hand valve 7, which have relatively large diameters, are not closed sufficiently, nitrogen gas leaks into the furnace and fuel gas flows through the shutoff valve. 5 and leaks into the furnace, creating a dangerous situation.

Attempts have been made to shut off the fuel gas by installing double metal touch shutoff valves and control valves, but complete shutoff is impossible. Keep the nitrogen gas cutoff valve 5 open at all times during furnace salt repair,
It is possible to constantly replenish nitrogen gas, but the hand valve 7
The consumption due to leakage from the fuel gas pipe is large and uneconomical, and it is not possible to follow changes in the fuel gas main and nitrogen gas source pressure.If the nitrogen gas pressure becomes too high relative to the fuel gas pressure, the nitrogen gas will reversely flow through the flow control valve 4. , it mixes into the fuel gas through the shutoff valve 5 and has an adverse effect on the fuel gas composition.On the other hand, when the nitrogen gas pressure becomes low, the fuel gas leaks and the gas shutoff becomes meaningless.

The present invention eliminates the drawbacks and problems of the prior art.

It is an object of the present invention to provide a fuel gas cutoff device that can be improved, and the above object can be achieved by providing the fuel gas cutoff device according to the claims.

That is, the present invention provides a fuel gas cutoff device when the furnace operation is stopped, which is installed in a branch pipe installed to branch fuel gas from a main pipe and supply it to a heating furnace, general industrial furnace, etc.
Nitrogen gas piping supplies nitrogen gas via a pressure adjustment valve between the gas flow control valve and gas cutoff valve installed in the branch pipe, and the fuel gas pressure in the main pipe is measured and a signal is output according to the measured value. a pressure signal transmitter that transmits a pressure signal; a pressure signal transmitter that measures the nitrogen gas pressure between the gas flow rate control valve and the gas cutoff valve and transmits a signal according to the measured value; and a pressure signal transmitter that transmits a signal according to the measured value; A pressure signal and a nitrogen pressure regulating valve controlled via a pressure regulator operated by the nitrogen gas pressure signal are provided, and configured by means for regulating the nitrogen gas pressure in accordance with the fuel gas pressure. This invention relates to a fuel gas cutoff device.

(Means for solving problems) The fuel gas cutoff device of the present invention will be explained in detail below.

FIG. 1 is an explanatory diagram of the fuel gas cutoff device of the present invention. As shown in the figure, the fuel gas piping system includes a fuel gas main pipe 1 through which fuel gases such as blast furnace gas and coke gas flow, and a gas branch pipe 2 that branches from the main pipe 1 and supplies fuel to the heating furnace. , an orifice 3 that measures the amount of gas flowing through the gas branch pipe 2, a flow control valve 4 that controls the amount of gas, a shutoff valve 5 that shuts off the flow of gas, and a burner 8 attached to the heating furnace.
A burner hand valve 7 and an air pipe 6 for supplying combustion air to the burner 8 are provided as holes, and a gas branch pipe 2 is provided.
A nitrogen pipe 9 for purging the fuel gas inside is connected to the gas branch pipe 2 between the shutoff valve 5 and the burner hand valve 7. The nitrogen pipe 9 is provided with a shutoff valve between it and the nitrogen gas source, and the fuel gas main pipe 1 is provided with a water seal valve 16 in preparation for periodic repairs. It is the same as the piping system leading to the furnace etc. However, a nitrogen gas pipe 9 and a gas diffusion pipe 11 are connected and provided between the flow rate control valve 4 and the cutoff valve 5, and the nitrogen gas pipe 9
is provided with a pressure control valve 12, and the gas diffusion pipe 11 is provided with a gas diffusion valve 10, and further includes a pressure signal transmitter 13a that measures the gas pressure in the fuel gas main pipe 1 and transmits the pressure as a signal. In addition, a pressure signal transmitter 13b that measures the pressure between the flow rate control valve 4 and the cutoff valve 5 and transmits the signal is provided, and the pressure control valve 12 of the nitrogen gas pipe 9 is activated via the pressure regulator 14 by this signal. It differs from conventional piping systems in that it is configured to be controlled.

Since the flow of fuel gas during operation of a heating furnace or the like is the same as in the case of a conventional piping system, the explanation will be omitted, and next, the gas purge operation of the piping system of the present invention will be described.

During periodic repair of a heating furnace or the like, the flow rate control valve 4 and the hand valve 7 of the gas branch pipe 2 are closed, and the cutoff valve 5 and the dispersion valve 10 are opened.

Next, open the shutoff valve 15 of the nitrogen pipe 9 and supply nitrogen gas.
A fuel gas dissipation pipe 11 between the flow rate control valve 4 and the hand valve 7
purge. The purge time is set using a timer. After completing the purge, close the shutoff valve 5. The diffusion valve 10 is closed and the nitrogen gas is confined between the flow rate control valve 4 and the cutoff valve 5.

After the containment operation, the pressure signal transmitter 131 of the gas main l
Based on the pressure signal P1 of L, the pressure regulator 14 sets the containment pressure P2 of nitrogen gas between the flow rate control valve 4 and the cutoff valve 5 to a pressure higher than the above-mentioned Pl by ΔP, that is, p2=p1.
+△P and based on the actual nitrogen gas pressure signal P3 from the pressure signal transmitter 13b, P3 =
The pressure regulating valve 12 is controlled so that the pressure becomes p2. The reason for increasing the nitrogen gas pressure by △P is to increase the blocking effect of the nitrogen gas.The reason is to maintain the nitrogen gas pressure slightly higher than the fuel gas pressure P1, so that the fuel gas is lowered by the flow rate control valve. ,4 to prevent intrusion. This pressure difference△
If PfJ'' is too large, a large amount of nitrogen gas may flow back toward the fuel main pipe 1, causing a change in the !!A composition of the fuel gas, so the nitrogen gas pressure should be 10 It is desirable to set it so that it is about % higher.

In FIG. 1, the fuel gas pressure signal transmitter 13a is attached to the main pipe IK, but this mounting position can naturally be between the flow control valve 4 of the fuel gas branch pipe 2 and the fuel main pipe 1. The effect is the same because pressure can be measured. Further, the pressure regulating valve 12 of the nitrogen gas pipe 9 does not need to be a special type of valve, and may be a simple type of electromagnetically operated shutoff valve. In addition, in the above description, an example was described in which the fuel branch pipe was purged using the dispersion pipe 11. In this purge, the flow rate control valve 4 is closed, the cutoff valve 51 and the hand valve 7 are opened, and the fuel in the fuel branch pipe 2 is purged. Purge the gas to the furnace side, close the shutoff valve 52 and the hand valve 7 after completing the purge, and then perform the operations described above to open the dissipation pipe 1.
1 does not necessarily have to be provided.

(Effects of the present invention) As explained above, when the fuel gas cutoff device of the present invention is used, the nitrogen
Even if gas leaks and the pressure drops, nitrogen gas can be supplied immediately, and the pressure of nitrogen gas can always be maintained at an appropriate level relative to the fuel gas pressure, so fuel gas will not leak into the furnace. Repair work can be carried out safely, and large amounts of nitrogen gas will not flow back into the fuel gas. Since the supply of nitrogen gas is carried out between the flow control valve 4 and the cutoff valve 5, the v-gas is doubly cut off by the cutoff valve 5 and the hand valve 7, so leakage of nitrogen gas to the furnace side is extremely unlikely. few.

Furthermore, according to the fuel gas cutoff device of the present invention, the gap between the cutoff valve 5 and the hand valve 7 is completely cut off, so work can be performed safely without using the water seal valve of the fuel gas main. The effect is extremely large. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a fuel gas shutoff device of the present invention, and FIG. 2 is an explanatory diagram of a conventional fuel gas shutoff device. 11... Fuel gas main pipe, 2... Fuel gas branch pipe, 3...・Orifice, 4...Flow control valve, 5...Shutoff valve, 6...Air piping, 7...Burner hand valve, 8...Burner, 9...
...Nitrogen purge piping, 10...Gas diffusion valve, 11...
・Gas diffusion piping, 12...pressure control valve, 13a...
Pressure signal transmitter, 13b... Pressure signal transmitter, 14.
...Pressure adjustment, 15...Nitrogen cutoff valve, 16...-Water seal valve.

Claims (1)

[Scope of Claims] 1. In a fuel gas cutoff device when furnace operation is stopped, which is installed in a branch pipe that is installed to branch fuel gas from a main pipe and supply it to a heating furnace, general industrial furnace, etc.: Nitrogen gas piping that supplies nitrogen gas via a pressure control valve between a gas flow control valve and a gas cutoff valve installed in a branch pipe; Measures the fuel gas pressure in the main pipe and sends a signal according to the measured value. a pressure signal transmitter that transmits; a pressure signal transmitter that measures nitrogen gas pressure between the gas flow rate control valve and the gas cutoff valve and transmits a signal according to the measured value; and the fuel gas pressure signal. , a nitrogen pressure regulating valve controlled via a pressure regulator operated by the nitrogen gas pressure signal; and means for regulating the nitrogen gas pressure in accordance with the fuel gas pressure. A fuel gas cutoff device characterized by: