GB2166993A - Apparatus for maintaining a gaseous atmosphere about a heat treatment zone - Google Patents

Abstract

For maintaining an inert atmosphere about a heat treatment zone, such as during welding of pipes, the zone is encompassed by a chamber having access ports for work units and inert atmosphere is introduced into the chamber. Apparatus is portable serving as an effective on-site welding aid. <IMAGE>

Description

SPECIFICATION Apparatus for maintaining a gaseous atmosphere about a heat treatment zone The present invention concerns an apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone.

When heat is applied to a reactive material it is necessary to ensure that atmospheric contamination does not influence the integrity of the material. For instance, when heat treating pipes it is required to maintain an inert atmosphere about the pipes, for example during welding operations and subsequent cooling.

According to the present invention an apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone comprises a chamber adapted to encompass the zone and having access ports for the introduction of work units.

Preferably the chamber is rotatable and includes means for restricting longitudinal displacement. A preferred form of chamber comprises a hexagonal compartment adapted to fit about a pipe to be treated and having access ports for work units in flats at the periphery of the compartment.

The invention will be described further, by way of example, with reference to the accompanying drawings; in which: Figure 1 is a diagrammatic representation of a shield to fit about pipes.

Figures 2 and 3 are sectional views showing modifications for use with large and small diameter pipes respectively.

A shield shown in Figure 1 comprises an hexagonal chamber 1 formed in two substantially equal parts 2 and 3 having a hinge 4 and a fastener 5.

Circular apertures 6 in the end walls of the chamber are dimensioned to allow the chamber to be fitted about a pipe. Work stations are provided in the flats. In Figure 1 an access port 7 for a welding torch is provided in flat 8. A viewing window 9 incorporating a filler wire access port 10 is provided in an adjacent flat. The viewing window can be formed from a heat resistant glass. An inlet port for shield gas can be provided in one or more of the flats.

When treating reactive material in the form of a pipe having a wall thickness less than about 2.5mm the diameter of the apertures 6 in the end walls of the chamber are such as to fit about the pipe with a dimensional toierance which permits free rotation of the chamber. However, for pipes having wall thickness greater than 2.5mm it was found desirable to increase the rate of heat extraction from the pipe to provide a sound product. This can be achieved, as shown in Figure 2, by fitting heat sinks 11 to the pipe at opposite ends of the chamber 1. The heat sinks are each formed in two halves to facilitate mounting and demounting and are securely clamped in position by set screws.

The apertures 6 in the end walls of the chamber are increased in diameter to accommodate reduced diameter portions 12 on the heat sinks 11. The heat sinks 11 also serve to restrict longitudinal movement of the chamber on the pipe.

As shown in Figure 3, it is preferable to provide guide rings 13 to restrict longitudinal movement of the chamber when used with pipes having wall thickness less than 2.5mm. The internal diameter of the rings exceeds the outside diameter of the pipe and the rings are mounted in position by set screws. The rings 13 are likewise formed in two halves.

A gas diffuser can be included within the chamber 1 to reduce turbulence of gas introduced as a shield into the chamber. Shield gas ports in flats on the chamber communicate with the interior of the diffuser. The diffuser has a plurality of outlet ports within the chamber.

Problems can arise when working in the field with difficult materials such as titianium and zirconium. With such materials it is necessary to provide an inert atmosphere about the weld to maintain its integrity. The chamber of the present invention being portable and simple to use meets these requirements and is an effective on-site aid.

1. An apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone comprising a chamber adapted to encompass the zone and having access ports for the introduction of work units.

2. An apparatus as claimed in claim 1 for welding pipes in which the chamber is rotatably mounted on the other pipes and restrained against axial displacement relative to the pipes.

3. An apparatus as claimed in claim 2 including axial restraint means releasably secured to the pipes at opposite sides of the chamber.

4. An apparatus as claimed in claim 3 in which the axial restraint means constitute heat sinks.

5. An apparatus as claimed in any preceding claim in which the chamber comprises a hexagonal compartment having the access ports in flats at the periphery of the compartment.

6. An apparatus as claimed in claim 5 in which the compartment comprises two substantially identical parts.

7. An apparatus as claimed in any preceding claim including a gas diffuser within the chamber.

8. An apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone substantially as herein described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for maintaining a gaseous atmosphere about a heat treatment zone The present invention concerns an apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone. When heat is applied to a reactive material it is necessary to ensure that atmospheric contamination does not influence the integrity of the material. For instance, when heat treating pipes it is required to maintain an inert atmosphere about the pipes, for example during welding operations and subsequent cooling. According to the present invention an apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone comprises a chamber adapted to encompass the zone and having access ports for the introduction of work units. Preferably the chamber is rotatable and includes means for restricting longitudinal displacement. A preferred form of chamber comprises a hexagonal compartment adapted to fit about a pipe to be treated and having access ports for work units in flats at the periphery of the compartment. The invention will be described further, by way of example, with reference to the accompanying drawings; in which: Figure 1 is a diagrammatic representation of a shield to fit about pipes. Figures 2 and 3 are sectional views showing modifications for use with large and small diameter pipes respectively. A shield shown in Figure 1 comprises an hexagonal chamber 1 formed in two substantially equal parts 2 and 3 having a hinge 4 and a fastener 5. Circular apertures 6 in the end walls of the chamber are dimensioned to allow the chamber to be fitted about a pipe. Work stations are provided in the flats. In Figure 1 an access port 7 for a welding torch is provided in flat 8. A viewing window 9 incorporating a filler wire access port 10 is provided in an adjacent flat. The viewing window can be formed from a heat resistant glass. An inlet port for shield gas can be provided in one or more of the flats. When treating reactive material in the form of a pipe having a wall thickness less than about 2.5mm the diameter of the apertures 6 in the end walls of the chamber are such as to fit about the pipe with a dimensional toierance which permits free rotation of the chamber. However, for pipes having wall thickness greater than 2.5mm it was found desirable to increase the rate of heat extraction from the pipe to provide a sound product. This can be achieved, as shown in Figure 2, by fitting heat sinks 11 to the pipe at opposite ends of the chamber 1. The heat sinks are each formed in two halves to facilitate mounting and demounting and are securely clamped in position by set screws. The apertures 6 in the end walls of the chamber are increased in diameter to accommodate reduced diameter portions 12 on the heat sinks 11. The heat sinks 11 also serve to restrict longitudinal movement of the chamber on the pipe. As shown in Figure 3, it is preferable to provide guide rings 13 to restrict longitudinal movement of the chamber when used with pipes having wall thickness less than 2.5mm. The internal diameter of the rings exceeds the outside diameter of the pipe and the rings are mounted in position by set screws. The rings 13 are likewise formed in two halves. A gas diffuser can be included within the chamber 1 to reduce turbulence of gas introduced as a shield into the chamber. Shield gas ports in flats on the chamber communicate with the interior of the diffuser. The diffuser has a plurality of outlet ports within the chamber. Problems can arise when working in the field with difficult materials such as titianium and zirconium. With such materials it is necessary to provide an inert atmosphere about the weld to maintain its integrity. The chamber of the present invention being portable and simple to use meets these requirements and is an effective on-site aid. CLAIMS

1. An apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone comprising a chamber adapted to encompass the zone and having access ports for the introduction of work units.

2. An apparatus as claimed in claim 1 for welding pipes in which the chamber is rotatably mounted on the other pipes and restrained against axial displacement relative to the pipes.

3. An apparatus as claimed in claim 2 including axial restraint means releasably secured to the pipes at opposite sides of the chamber.

4. An apparatus as claimed in claim 3 in which the axial restraint means constitute heat sinks.

5. An apparatus as claimed in any preceding claim in which the chamber comprises a hexagonal compartment having the access ports in flats at the periphery of the compartment.

6. An apparatus as claimed in claim 5 in which the compartment comprises two substantially identical parts.

7. An apparatus as claimed in any preceding claim including a gas diffuser within the chamber.

8. An apparatus for maintaining a gaseous, non-reactive atmosphere about a heat treatment zone substantially as herein described with reference to and as illustrated in the accompanying drawings.