USING PLASMA ARC AND THERMITE TO DEMOLISH CONCRETE

Patent number: 5532449
Filing date: Aug 29, 1994
Issue date: Jul 2, 1996

A plasma arc can be employed to demolish a concrete structure at a high efficiency, while preventing a secondary problem due to noise, flying dust and chips, and the like. The concrete structure can be demolished by melting a surface of the concrete structure by generating a plasma arc from a plasma torch (15) of a plasma arc generator, mixing thermite powder (T) with a supply gas (Gc) for the plasma torch (15), directing the plasma arc at the surface of the concrete structure, and controlling the rate of supply of the thermite powder (T) to the plasma torch (15) in response to the operation of the plasma arc, including initiating and stopping the supply of the thermite powder (T) to the plasma torch (15) in a manner coordinated with the initiation and stoppage of the plasma arc, thereby controlling the heat generated by the thermite reaction, and melting the surface of the concrete structure. The plasma generator (1) can be provided with a feeder (20) for mixing the thermite powder...

Inventor: Taku Murakami
Original Assignee: Kabushiki Kaisha Komatsu Seisakusho
Current U.S. Classification: 219/121.59; 219/70; 219/121.38; 219/121.44; 219/121.48; 266/48
International Classification: B23K 1000

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Citations

Cited Patent	Filing date	Issue date	Original Assignee	Title
US3740522	Apr 12, 1971	Jun 19, 1973		FOR MAINTAINING TUBE CONCENTRICITY
US3988566	Jul 17, 1975	Oct 26, 1976	Metco Inc.	Automatic plasma flame spraying process and apparatus
US4371771	Nov 10, 1980	Feb 1, 1983	The United States of America as represented by the Secretary of the Navy	Cutting torch and method
US4477060	Jun 13, 1983	Oct 16, 1984		Underwater cutting tool
US4541616	May 23, 1984	Sep 17, 1985		Thermal burning rod
US4559890	Apr 25, 1983	Dec 24, 1985	Jet Research Center, Inc.	Mooring release apparatus and method
US4766284	Mar 5, 1986	Aug 23, 1988	Maghemite Inc.	Production of compounds by reaction of solid materials at high temperatures produced by plasma arc torches

Referenced by

Citing Patent	Filing date	Issue date	Original Assignee	Title
US5773785	Jun 7, 1996	Jun 30, 1998	Komatsu Ltd. Daido Tokushuko Kabushiki Kaisha	Plasma cutting apparatus for concrete structures

Claims

1. A method of demolishing a concrete structure, comprising the steps of:

generating a plasma arc from a plasma torch of a plasma arc generator,

mixing thermite powder with a supply gas for said plasma torch,

passing the resulting mixture into the thus generated plasma arc,

directing the plasma arc containing said mixture toward a surface of the concrete structure, and

controlling the supplying of said thermite powder to the plasma arc responsive to the operation of the plasma torch, thereby melting at least a portion of the surface of the concrete structure.

2. A method in accordance with claim 1, wherein the step of controlling comprises varying the rate of addition of the hermite powder to the supply gas in response to the operation of the plasma torch.
3. A method in accordance with claim 1, wherein said step of controlling comprises manipulating the rate of supplying the thermite powder to the plasma arc in response to the operation of the plasma torch, including initiating and stopping the supplying of the thermite powder to the plasma arc in a manner coordinated with the initiation and stoppage of the plasma arc, thereby controlling the heat generated by the thermite reaction.
4. A method in accordance with claim 3, wherein the step of manipulating comprises varying the rate of addition of the thermite powder to the supply gas in response to the operation of the plasma torch.
5. A method in accordance with claim 1, wherein said step of controlling includes initiating and stopping the supplying of said thermite powder to the plasma arc in a manner coordinated with the initiation and stoppage of the plasma arc.
6. A method in accordance with claim 1, wherein said step of mixing comprises mixing said thermite powder, said supply gas, and at least one material selected from the group consisting of agents to control a thermite reaction starting temperature.
7. A method in accordance with claim 1, wherein said step of mixing comprises mixing said thermite powder, said supply gas, and at least one material selected from the group consisting of agents to lower the melting point of concrete.
8. A method in accordance with claim 1, wherein said steps of generating a plasma arc from said plasma torch and directing the plasma arc containing said mixture toward a surface of the concrete structure comprise:

positioning an anodic dummy electrode on said surface between said surface and said plasma torch, and

generating said plasma arc to said dummy electrode.

9. A method in accordance with claim 8, further comprising simultaneously moving said dummy electrode and said plasma torch in a corresponding manner.
10. A method in accordance with claim 9, wherein the step of controlling comprises varying the rate of addition of the thermite powder to the supply gas in response to the operation of the plasma torch.
11. A method in accordance with claim 9, wherein said step of controlling comprises manipulating the rate of supplying the thermite powder to the plasma arc in response to the operation of the plasma torch, including initiating and stopping the supplying of the thermite powder to the plasma arc in a manner coordinated with the initiation and stoppage of the plasma arc, thereby controlling the heat generated by the thermite reaction.
12. A method in accordance with claim 11, wherein the step of manipulating comprises varying the rate of addition of the thermite powder to the supply gas in response to the operation of the plasma torch.
13. A method in accordance with claim 9, wherein said step of controlling includes initiating and stopping the supplying of said thermite powder to the plasma arc in a manner coordinated with the initiation and stoppage of the plasma arc.
14. A method in accordance with claim 9, wherein said step of mixing comprises mixing said thermite powder, said supply gas, and at least one material selected from the group consisting of agents to control a thermite reaction starting temperature.
15. A method in accordance with claim 9, wherein said step of mixing comprises mixing said thermite powder, said supply gas, and at least one material selected from the group consisting of agents to lower the melting point of concrete.

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