WO2007133091A1

WO2007133091A1 - An apparatus for automatic detection of measurement of gas leakage in a welding system

Info

Publication number: WO2007133091A1
Application number: PCT/NO2007/000172
Authority: WO
Inventors: Arild Halvorsen
Original assignee: Weltec AS
Current assignee: Weltec AS
Priority date: 2006-05-12
Filing date: 2007-05-11
Publication date: 2007-11-22
Anticipated expiration: 2008-11-12
Also published as: NO20062153L; NO328259B1

Abstract

This patent application relates to the automatic detection or measurement of welding gas leakages that may occur in hoses, pipes, nozzles, valves, connections or other part of a system in a welding apparatus for transport of welding gas from a supply point to the welding nozzle.

Description

Apparatus and method for automatic testing of a welding gas provisioning facility

The invention relates to an apparatus and a method for detecting leakage in a shielding gas delivery system in a shielding gas welding apparatus. The invention may most advantageously constitute an automatic leakage detector for a robotic shielding gas welding system.

The present inventors have experienced problems in connection with the leakage of welding gas, and especially such leakage as may occur in systems which operate using shielding gas such as MIG, MAG or TIG, and in particular during welding operations where programmed robots are used to perform these operations automatically. The leakage of welding gas that occurs due to leaking hoses and worn parts and connections results in a higher consumption of gas and an unwanted leakage of gases which may be detrimental both to the environment and to health. In addition, a leakage of gas, in particular during shielding gas welding, will result in the quality of the weld being sub-standard, and there will be costs associated with rejects.

Automatic systems for detecting leakage during such welding operations of the type provided by the invention are not known to exist.

It may be possible to use leakage detectors in the form of cameras (adapted to the spectrum of the gas) or sniffers that monitor the operation, but these have in practice been found to be unreliable and costly.

It is therefore normal practice that the welding equipment is inspected manually at given service intervals. An inspection of the quality of the weld will also indicate that there may be problems with the gas supply.

In addition, it is known that the users set the gas flow rate so that there is always a certain overcapacity of gas (unused gas). In this way, the system can withstand a certain leakage before it results in inferior weld quality, but this gives poor gas economy during the operation of the welding machine.

It has also been found that these techniques, on the whole, are costly and have an impact on efficiency. If a leakage is to be detected before it results in faults in the weld, the manual checks must be frequent, and this results in reduced operating time with concomitant increased costs.

One of several objects of the present invention is to provide an automatic technique to s detect leakage, based on shutting off the normal outlet of the gas in the welding head (7), and in combination with a flow sensor (1), being able to determine whether the leakage level within is acceptable.

In one variant of the invention, it can also detect a restriction or blockage in the gas o supply from a gas source facility to the welding site.

During normal operation, a shutting off the normal outlet of the gas at the nozzle of the welding gun, also referred as the welding head, is normally difficult due to the high temperatures that occur at the welding head. It has therefore been found advantageous s to combine the leakage test with the regular cleaning procedures that the nozzle must in any case first undergo, since some time will then be spent cleaning between the end of the welding operation and the start of the leakage test. This time should be of such length to allow the temperature of the nozzle to be lowered sufficiently.

0 The invention will be explained in more detail below with reference to the attached drawings, hi each drawing, reference numerals are used that are specific to the individual drawing figure, unless otherwise specified in the following description.

Reference is first made to Figure 1, which shows a schematic presentation of a leakage ₅ testing system arranged in connection with a robot system for shielding gas welding. After the cleaning process has been completed, the robot automatically moves the welding head into position for leakage testing in a separate test chamber (8). The control unit (2) for the leakage tester detects that the nozzle is in place by means of an inductive sensor (6) and in that way receives a signal that the test can start. o The control unit (2) then admits gas by means of a bypass valve (3), so that welding gas is admitted to the whole system independent of the welding system gas control valve. Flow sensor (1) is read by the control unit (2) which compares the read flow that is in the system with pre-selected limit values.

5 With reference to Figure 2, there is described another variant of a leakage detection device according to the invention. In this variant, the control unit is connected to the welding robot gas control valve so that it can open and close the valve by means of a control signal that is passed to the valve in parallel with the control signal from the welding apparatus, or through a selector circuit that is controlled by the welding apparatus when testing is to be conducted. The use of one and the same valve both for welding operations and for testing can also be introduced into the solution outlined in Figure 1, either in substitution for the bypass valve or as a supplement to control both valves so as to be able to conduct a separate valve test. Furthermore, the test chamber 8 that is shown in Figure 2 is provided with an outlet to which a further flow sensor IB is connected. During testing, the control unit 2 sets the gas valve in a suitable position to allow a predetermined gas stream to flow from the gas source to the welding head, and by measuring the gas flow using each of the two sensors, the control unit determines whether there is any difference as a result of a leakage between the flow sensor on the inlet side of the gas source and the flow sensor IB on the outlet side at the welding head. The testing device may advantageously also comprise a controllable valve (not shown on the drawing) inserted between the test chamber flow sensor and connected to a control output from the control unit, thereby permitting testing of the welding apparatus gas line system based on both pressure and flow, or a selected one of these.

As stated above, the bypass valve may be included or excluded, depending on the design of the individual welding apparatus, for example, in that the bypass valve and its support (T pieces and/or directional valves) for connection in the flow path may be required when the inventive testing device is retrofitted in an existing welding apparatus, or may be omitted in cases where the inventive testing device is incorporated into the welding apparatus during its production.

The automatic method for detection of gas leakage during welding operations that is proposed in this patent application will mean that the user:

- will reduce the overconsumption of gas (which results in a direct financial saving)

- will obtain a consistently good weld quality - will have a positive HSE effect as unused gas is not discharged into the atmosphere.

Compared with manual tests, an automatic leakage test could be conducted more frequently, thereby weeding out faults as early as possible, and, moreover, the costs of carrying out the actual test are low.

A more detailed description of various aspects of the invention is given below. A: The component parts of a welding robot that are most prone to leakages are hose package 5, welding head/nozzle (7) and all integral connections. It is particularly the parts that are movable and/or have a high temperature that are extremely susceptible.

B: The welding robot (4) can be programmed to go to leakage testing after a cleaning process has been completed. When the nozzle (7) has been placed in the test chamber (8), it is intended that the flexible funnel against which the nozzle stops should seal sufficiently to allow a test to be carried out.

C: The test is started in that the inductive position sensor (6) gives the signal that the nozzle (7) is in place in the test chamber (8).

D: If the flow that is read by the control unit (2) from flow sensor (1) exceeds pre-set limit values, a leakage is observed. To ensure that there is no fault in the measuring system, the control unit (2) can give a status to welding robot (4) that there is a fault, after which the nozzle (7) is removed and then replaced in the test chamber (8) for a new test. This test can be repeated several times if the user wishes the accuracy of the measurement to be optimal. An external reading of the STATUS signal from the control unit (2) may also be useful in allowing the user to monitor progress and react to any faults that may occur.

E: If the flow that is read by the control unit (2) from flow sensor (1) exceeds pre-set limit values, this leakage can be compensated for by increasing the supply of gas. This can be done in that the welding robot receives a signal in respect of the leakage level that has been measured, and then compensates for this by increasing the admission of gas. This may be a temporary solution to finish an operation before a service can be carried out.

F: The sealing material used in the test chamber (8), especially in the version where the test is based on shutting off the test chamber outlet, must have special properties with regard to being able to withstand high temperatures whilst being sufficiently flexible to ensure a good seal between the nozzle (7) and the test chamber (8). In addition, it is necessary that the material should have a long lifetime.

G: In a system for automatic welding as described, a welding wire is used that is fed from the robot (4) and out through the nozzle (7). There will always be a minimum leakage in such a system which will correspond to what leaks through the liners through which this welding wire is fed. If a minimum leakage corresponding to what has been set as a limit value cannot be observed, this can be taken as an indication that the conduits are blocked, which may prevent the feeding of the welding wire. It may be an extra function of this measuring system for leakage tests to indicate where such a blockage has occurred.

Thus, the invention relates in general to a system and a method for automatic measurement of gas leakage in the parts which transport gas from a supply point to an apparatus that is to release the gas in a predetermined amount for various purposes. It may, for example, be included in connection with automatic welding operations (robots) as shown in Fig. 1, where the parts used to carry out the test either may be incorporated into welding robot (4) or are wholly or partly added outside of the robot.

The design of the sealing around the welding nozzle in connection with a transition to a sealed test chamber 8 is of great importance for a successful test, where this chamber is included in a system for gas leakage testing.

The invention utilises of the location of the welding head nozzle (7) in test chamber (8) with the aid of an inductive sensor.

Detection of the correct location of the welding head nozzle (7) in test chamber (8) is intended to be obtained by means of a pressure sensor (not shown in the drawings) connected to the interior of the test chamber for measuring the pressure in the test chamber, where the control unit (2) is provided with an input from the pressure sensor and utilises the pressure measured by the pressure sensor as an indication that the nozzle (7) is in place. Determining that the nozzle has been correctly positioned in the test chamber by means of pressure measurement can be based on a predetermined pressure limit value, or can be determined on the basis of a pressure comparison in that the device is equipped with a further pressure sensor on the side on the welding apparatus where the gas is introduced.

In an advantageous embodiment of the invention for measuring the whole gas flow system in the welding apparatus, a gas bypass valve (3) is used. In this way the gas supply is controlled during testing independent of the welding apparatus valve. To perform leakage testing using the inventive testing system, a welding robot (4) is preferably programmed to go to "a separate testing station", where the test chamber (8) is arranged, for leakage testing.

The present invention provides automatic to indicate blockage in liners/conduit for feeding the welding wire.

A testing device according to this invention employs a test chamber of the type that will be explained below with reference to Figures 3 to 15 inclusive. The testing device may however be realised using other means for shutting off the gas outlet in the welding head, optionally a shut-off means that is provided with a pressure measuring device to measure the gas pressure at the outlet, or to lead gas from the gas outlet in a welding head to a flow measuring device.

Figure 3 is a split drawing of an embodiment of test chamber 8. The test chamber housing 11 can be made in different ways as explained with reference to the following drawings. The chamber consists of an upper circular-cylindrical part and a lower tapered or conical part. The upper cylindrical part comprises two sub-chambers, where the upper part is arranged to hold a gasket which ensures a good seal against the welding head nozzle. The lower part is partly separated from the upper part, although with an opening that allows communication between the upper part and the lower part, hi the upper part there is room for the introduction of a gasket seat 12 of an external circular-cylindrical form and an internal tapering form that is adapted to a funnel-shaped gasket 14. A pressure washer 13 must be placed over the gasket and a pipe nut 15 screwed into an inner threaded portion of the upper part of the test chamber in order to hold the gasket in place in the upper part of the chamber. The test chamber is preferably fastened to a bracket arm on which there is also arranged a retaining plate 16 for securing a position indicator 17 for sensing the welding head when it has been placed in the test chamber.

Figure 4 is a sectional top view of the gasket.

Figure 5 shows a side view, a top view and a perspective view of the pressure washer.

Figure 6 illustrates the gasket seat in section, in a top view and a perspective view. Figure 7 illustrates the different parts of the test chamber, such as upper sub-chamber 7, dividing plate 3 which separates the upper and lower parts of the test chamber, the lower part 6, the funnel-shaped or tapered bottom part 4 of the chamber, the bottom outlet 8 of the chamber, the retaining plate 1 for securing position indicator 17, the bracket arm 5 and a mounting flange 2.

Figure 8 shows the bracket arm 5 in more detail.

Figure 9 shows the lower part 6 of the chamber in more detail.

Figure 10 shows the mounting flange 2 in more detail.

Figure 11 shows the retaining plate 1 in more detail.

Figure 12 shows the bottom part 4 of the chamber in more detail.

Figure 13 shows the bottom outlet 8 in more detail.

Figure 14 shows the upper part 7 of the chamber in more detail.

Figure 15 shows the dividing plate 3 in more detail.

Figures 16A, 16B and 16C show in more detail the chamber in use with a welding head nozzle 20 placed in the welding head receiving means in the test chamber. The area circled and marked with the letter C, in particular, is drawn in more detail in the sectional view shown in Figure 16C. The reference numerals for the elements shown in these three figures correspond to the reference numerals that can be seen from Figure 3 and its accompanying explanation. The position of the dividing plate is marked with the letter B to indicate the division it provides for establishing the interior space in the lower part of the chamber, which is indicated by means of the letter A. The reference numeral 18 is an indication of a device that can be attached to the chamber outlet 8, for example, for closing the chamber outlet 8 or for routing gas from the chamber outlet to a further device, as described elsewhere in this description.

In one embodiment of the inventive test chamber, a controllable "discharge valve" is provided in or connected to the bottom outlet of the chamber. During testing with a pressurised chamber, the discharge valve is kept closed. Before or after testing, the valve is opened so that slag or other debris which falls from the welding head into the chamber can be discharged from the chamber, for example, by using a gas stream from the welding head. A controllable discharge valve may be designed to be controllable by use of pneumatic, hydraulic, electric or some other means, as controllable from the control unit, for opening according to a pre-determined program, or by other means such as mechanical actuation from the welding head which opens the bottom valve when the welding head is removed from the test chamber and closes it when the welding head is introduced into the test chamber. Optionally, the chamber may be provided with a device which detects the presence of debris or other unwanted objects in the chamber, and be designed to effect an emptying of the chamber in a suitable manner.

Claims

P a t e n t c l a i m s

1.

An apparatus for automatic detection or measurement of gas leakage in the parts of a welding system that transport gas from a supply point to an apparatus that is to release the gas in a predetermined amount for different purposes, especially parts of a welding system that are included in connection with automatic welding operations (robots), wherein the parts used to carry out the test either can be incorporated into welding robot (4) or are wholly or partly added outside of the robot.

2.

A test chamber for an apparatus according to claim 1, with sealing around the welding nozzle in connection with the transition to a sealed test chamber, wherein this chamber is a part of a system for gas leakage testing, s

3.

An apparatus for detecting the correct location of nozzle (7) in test chamber (8) by means of an inductive sensor for an apparatus in accordance with claim 1.

0 4.

An apparatus for detecting the location of nozzle (7) in test chamber (8) in a system in accordance with claim 1, by means of a pressure sensor that measures the pressure in the test chamber, wherein the control unit (2) utilises this pressure as an indication that the nozzle (7) is in place. ₅

5.

An apparatus for automatic detection or measurement of gas leakage in the parts that transport gas from a supply point to an apparatus that is to release the gas in accordance with claim 1, comprising measuring the whole system by using a gas bypass valve (3). 0

6.

An apparatus for automatic detection or measurement of gas leakage in the parts that transport gas from a supply point to an apparatus that is to release the gas, comprising an apparatus for automatic compensation for leakage. S

7.

The welding robot (4) programmed to move the welding head to a suitable testing station for leakage testing of the gas supply system of the welding robot.

s

8.

An apparatus for automatic detection or measurement of gas leakage in the parts which transport gas from a supply point to an apparatus that is to release the gas, comprising automatically indicating blockage in the liners/conduit for feeding welding wire in a welding gas supply system hi a wire welding apparatus (MIG/MAG). 0

9.

An apparatus for automatic testing of a welding gas system that transports gas from a supply point to an apparatus that is to release the gas at the welding area, comprising detecting a restriction or blockage by measuring through-flow from gas inlet to welding s head outlet, or by measuring pressure at at least one point in the welding gas system, such as at a gas outlet in a welding head.