6 Types of Welding Leak Stoppage Methods (The Welder Must Know)

In industrial production, some continuous running equipment leaks due to various reasons.

Such as pipes, valves, containers, etc.

These leaks affect the stability of normal production and the quality of products, pollute the production environment and cause unnecessary waste.

What’s more, the leakage of some media, such as toxic gas and grease, will cause great harm to the safety in production and the surrounding environment.

For example, the explosion of Qingdao Huangdao oil pipeline on November 22, 2013 and the explosion of Tianjin Binhai New Area dangerous goods warehouse on August 2, 2015 caused huge losses of life and property to the country and people.

The causes of these accidents are all caused by medium leakage.

Therefore, the leakage of some industrial products cannot be ignored and must be handled in a timely manner.

However, how to remedy the leakage of equipment containing flammable and explosive substances or toxic chemical media under pressure is also a technical problem.

Leakage stoppage of equipment with pressure, oil or toxic substances belongs to special welding under abnormal working conditions, which is different from the normal welding specifications, and attaches great importance to safety during operation.

Before welding, safety construction measures must be formulated to prevent accidents, so as to ensure the personal safety of the workplace, welders and other workers.

Welders must be experienced and skilled, and welding engineers with rich technical experience must provide technical guidance for safe operation.

For example, a certain type of oil tank can only be operated when the capacity, ignition point, pressure, etc. of the oil inside it are known, and the welding process can not cause personal injury or even greater safety accidents.

Therefore, the following points must be achieved before and during welding construction:

First, safe pressure relief.

Before welding and plugging, it must be determined whether the equipment pressure to be welded will cause personal injury.

Or under the influence of welding heat source, the equipment has a safe pressure relief channel (such as a safety valve).

Second, temperature control.

Before welding, all cooling measures for fire and explosion prevention must be taken.

During welding, the welder must weld in strict accordance with the minimum and minimum heat input specified in the process document, and safety cooling measures must be taken while welding to prevent fire or explosion.

Third, prevent poisoning.

When plugging and welding the containers or pipes containing toxic substances, the leaked toxic gas must be timely dispersed and fresh air must be timely supplied.

At the same time, it is necessary to isolate pollution from the outflow of toxic substances.

The following are several commonly used welding leak stoppage methods in engineering practice for everyone to learn and improve.

1. Hammering, twisting and pressing welding method

This method is applicable to the welding of cracks, sand holes and blowholes in low-pressure vessels and pipes.

Small diameter electrodes shall be used for welding as much as possible. The welding current shall strictly comply with the process requirements.

The fast welding method shall be used for operation. The heat of the arc shall be used to heat the periphery of the leakage point.

After the arc is extinguished, the hammer or pointed shovel shall be used to quickly squeeze the leakage point, and the weld shall be hammered while welding.

2. Riveting welding method

When some cracks are wide or the diameter of sand holes and air holes is large, it is difficult to use hammering, twisting and pressing.

The cracks or holes can be riveted with appropriate iron wires or welding rods to reduce the pressure and flow of leakage, and then the welding can be completed quickly with small current.

The key point of this method is that only one section can be blocked at a time, and then rapid welding can be carried out.

As shown in Fig. 1

Fig.1

3. Top flow welding method

Some leaks are caused by corrosion, wear and thinning. At this time, do not weld the leak directly, otherwise, it is easy to cause bigger leaks.

Spot welding shall be carried out at appropriate positions next to or below the leakage.

There is no leakage at these places.

First, a molten pool shall be established, and then, like a swallow’s mud trap, the leakage shall be surrounded by welding point by point to gradually reduce the area of the leakage.

Finally, the leakage shall be sealed with a suitable welding current using a small diameter electrode, as shown in Fig. 2.

Fig.2

4. Diversion welding method

It is applicable to welding with large leakage area, large flow or large pressure, as shown in Fig. 3.

According to the shape of the leakage, make a complementary plate with a closure device.

When the leakage is relatively serious, the interceptor uses a section of diversion pipe, on which a valve is installed;

When the leakage is small, a nut can be pre welded on the repair plate.

The area of the patching plate shall be larger than the leakage point. The position of the intercepting device on the patching plate must face the leakage point.

Apply a bead of sealant on the side where the patching plate contacts the leakage point to let the leaking medium flow out from the guide pipe to reduce the leakage around the patching plate.

After the repair plate is welded, close the valve or tighten the bolts.

Fig.3

5. Sleeve tube welding method

When the pipeline leaks in a large area due to corrosion or wear,

A section of pipe with the same diameter or just able to hold the leakage pipe diameter is used as the sleeve tube, and the length depends on the area of the leakage.

Cut the sleeve pipe into two halves symmetrically, and weld a deflector pipe. The specific welding method is the same as the deflector welding method.

In the welding sequence, the circumferential seam between the pipe and the sleeve shall be welded first, and then the welding seam of the sleeve shall be welded, as shown in Fig. 4.

Fig.4

6. Welding of oil leakage container

Continuous welding shall not be adopted. The temperature of the weld shall not rise too high.

Spot welding method shall be adopted and cooling shall be conducted at the same time.

For example, after spot welding several points, immediately use cotton gauze soaked in water to cool the welding points.

Sometimes, it is necessary to make comprehensive use of the above methods of leak stoppage. Welding leak stoppage requires flexibility to ensure the success of welding leak stoppage.

However, not all metal materials are suitable for welding leak stoppage. Only ordinary low carbon steel and low alloy steel can adopt the above leak stoppage methods.

Austenitic stainless steel can only be repaired by welding when it is determined that the base metal near the leak point can produce large plastic deformation, otherwise it cannot be repaired by welding.

The medium in the heat-resistant steel pipe is usually high-temperature and high-pressure steam.

Leakage after long-term service cannot be repaired under pressure. Low temperature steel shall not be repaired by welding under pressure.

All the above welding methods are temporary measures and do not have the metal mechanical properties that can be achieved by welding in a strict sense.

When the equipment is not under pressure or loaded with medium, the temporary leakage blocking welding state must be completely removed, and the equipment must be welded again or repaired in other ways to meet the requirements of the product.

Summary

With the development of modern production, welding leak stoppage technology is an emergency technology needed in the continuous production process.

The treatment of leakage accident requires a certain time, and the leakage shall be completely replaced later.

The application of leak stoppage technology should be flexible.

Multiple methods can also be used to deal with a leak. The purpose is to prevent leakage after welding.

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