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Steel pipe weld repairer

Steel pipe weld repairer

1. No power supply is required, it is not restricted by remote valves, and it works under pressure, which is particularly suitable for underground coal mine operations.
2. Under normal operation of the pipeline, there is no need to remove the pipeline, because the connection part has a sealing ring to achieve a high-strength sealing effect.
3. Suitable for underground engineering, chemical industry, tap water, various underground pipelines, etc. In the absence of power, complete pressure connection, pressure maintenance and water extraction engineering.
4. Without stopping water or oil, you can quickly complete the positioning connection at any part of the pipeline. It has the characteristics of high strength, small size and easy operation.
5. The quick takeover is manually operated, without stopping production, and is used in various water and oil pipelines, and does not require any power for rapid maintenance.

Analysis of the causes of leakage in steel pipe welds

Incomplete fusion/incomplete penetration:

Causes: Insufficient heat during welding, too fast welding speed, too small groove angle or too thick blunt edge, incorrect welding rod/wire angle, arc deviation from the weld center, incomplete interlayer cleaning resulting in slag hindering fusion.

Consequences: The weld metal and the parent material, or the weld metal layers and layers, fail to completely melt and combine, forming continuous or intermittent gaps. This is a common direct channel for leakage.

Porosity:

Causes: Welding materials are damp, the parent material or welding wire surface has oil, rust, paint and other pollutants (producing CO, H2), shielding gas is impure or the flow is improper, the arc is too long, and the welding speed is too fast, resulting in no time for gas to escape.

Consequences: Cavities are formed inside or on the surface of the weld. Dense pores or penetrating pores (especially root pores) will become leakage paths.

Slag inclusions:

Causes: Incomplete cleaning between welds or weld layers, too low welding current so that slag cannot float, too fast welding speed, too small groove angle, improper electrode swinging method.

Consequences: Non-metallic inclusions remain in the weld. Large or penetrating slag inclusions will weaken the strength of the weld and may connect to form a leakage channel.

Cracks:

Hot cracks: Occur in the late solidification period, mainly related to the chemical composition of the weld metal, solidification segregation, and large welding stress.

Cold cracks: Occur during the cooling process after welding or a period of time after cooling. The main causes are high diffused hydrogen content in the weld, the presence of hardened structure, and large restraint stress. Insufficient drying of welding materials and moisture/contamination on the surface of the parent material are the main sources of hydrogen.

Reheat cracks: Occur during post-weld heat treatment or high-temperature service, and are related to grain boundary weakening and residual stress release caused by alloying elements.

Undercut:

Causes: Welding current is too large, arc is too long, welding rod/welding gun angle is incorrect, welding speed is too fast, improper operation during vertical welding or fillet welding.

Consequences: The base material along the edge of the weld is melted by the arc without being supplemented by filler metal, forming grooves or depressions. Undercut reduces the effective cross-sectional area of ​​the base material, causing stress concentration, which easily induces cracks and becomes a leakage point.

Weld nodules and concave:

Weld nodules: Metal nodules formed when molten metal flows onto unmelted base material. Although it may not leak directly, it affects the appearance and stress distribution. The root nodules may cover defects such as incomplete penetration.

Root concave: When single-sided welding and double-sided forming are performed, the middle of the weld root is a depression lower than the surface of the base material. Too deep concave will significantly reduce the effective thickness of the weld, reduce the load-bearing capacity, and easily lead to leakage.

Burn-through:

Causes: Welding current is too large, assembly gap is too large, welding speed is too slow.

Consequences: During welding, the molten pool collapses, forming a perforation on the weld. This is a very obvious leak point.

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