Orbital welding internal pressure control

Abstract

A weld bead geometry control system is provided for use in welding in abutment tubes or tubular components. The present invention can accurately and quickly correct for changes in purge gas pressure due to flow losses in real-time, to prevent any undesired protrusion or concavity of a molten weld bead, while allowing complete penetration of the weld. The present invention can additionally dynamically adjust the internal purge pressure to counteract the effects of gravitational pull on the molten weld bead. The weld bead geometry control system can in act in concert with existing orbital welding systems to consistently produce high quality and fully penetrated weld beads that meet or exceed industry standards.

Description

BACKGROUND [0001] 1. Field of Invention [0002] This invention relates generally to a pressure sensing and control device, and, more particularly, to a device enabling the adjustment of purge gas flow automatically and dynamically during the orbital welding of tubular components, to maintain a desired internal tube pressure, for the purpose of affecting the internal geometry of a molten weld bead and reducing particle generation. Additionally, the present invention relates to a device enabling the adjustment of purge gas flow and pressure relative to the activity of an orbital tube welder, again for the purpose of affecting the internal geometry of a molten weld bead and reducing particle generation during the weld. [0003] 2. Description of Prior Art [0004] When welding in abutment two metal tubes or components with tubular extensions, using an orbital welding device, such as the device disclosed in U.S. Pat. No. 5,196,664 to McGushion (1993), it is generally a desired result to crea...

AI Technical Summary

Benefits of technology

[0023] It is a general object of the present invention to provide a system for controlling the internal flow and pressure of tubular components throughout the welding process to overcome the deficiencies of existing systems and methods.

[0024] It is another object of the present invention to provide a system in which a predetermined constant internal tube pressure can be preprogrammed, and, in an automatic and timely manner, be adjusted to respond to pressure altering occurrences at the molten weld seam during the welding process, to ultimately affect the geometry of the weld bead.

Problems solved by technology

Often, the result of complete penetration is an undesirable weld bead protrusion into the internal diameter of the tubular component, effectively decreasing this internal diameter at the weld location.

This protrusion can trap impurities during normal operation of the manufactured product and create a significant and undesirable head loss in the system.

For example, the wall thickness of the tube is a significant factor in determining a weld schedule, and require quite dissimilar weld power schedules.

The resulting weld bead may not fully envelope the internal diameter weld seam, if there is even a slight misalignment of the seam versus the electrode of the orbital welder.

This method can result in an unacceptable rate of weld rejection or failure.

Although the concept of supporting the molten weld bead with increased internal pressure is approaching an acceptable solution, there are several major problems with the constant internal flow method.

The first problem occurs if the internal pressure is too low, causing a sagging of the weld bead as previously described.

The second problem occurs when the internal pressure is too high, causing the weld bead to bulge out radially, away from the center of the tubular extensions, characterized by an undesirable increase in internal and external diameters of the tubular extensions at the weld joint.

If the internal pressure is even higher, the gas may cause the molten weld joint between the tubular extensions to rupture, completely destroying the weld bead and, possibly, the components being welded.

A rupture is, for obvious reasons, an extremely undesirable occurrence.

Any one of these problems may occur while using the constant flow positive internal pressure system.

The constant flow positive internal pressure system's inherent unpredictability is caused by the behavior of the tubes during the welding process.

The temporary gap formed at this point allows the internal flow of gas to escape, causing an undesirable internal drop in pressure.

This phenomenon can degrade the quality of the weld or even rupture the weld seam, and potentially destroy the electrode.

Because the internal pressure of the system can change at a rapid rate, it is difficult for a person to accurately manually adjust the flow of internal gas.

This inaccurate and slow method of adjustment can easily result in a flawed weld bead and damage to expensive components.

In addition to the poor quality, low reaction time, and inaccuracies inherent to the manual pressure control system, it is labor intensive, requiring the constant supervision and control by a person.

Essentially, the system may not be compatible with existing orbital welders presently in use, requiring the purchase of both the pressure control system and the compatible orbital welder.

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