Protecting pipeline weld joints

A precise way to protect your pipeline weld joints in the field

Pipelines inevitably face corrosion and damage in the field. To reduce maintenance costs and prevent replacement, a long-lasting protective coating is essential. This coating is usually applied directly at the pipe manufacturer or a dedicated coating plant, but pipe ends must remain uncoated until they are welded together in the field. This leaves pipe endings particularly vulnerable to corrosion if the right coating is not applied correctly after welding. Sulzer has developed a cartridge-based application system to ensure a precise and rapid solution to this challenge.

A man is prepating a steel — Fig. 1 Steel preparation of a weld field joint.

Taking error out of the mix

Once the steel surface of a pipe ending is prepared and the welding is complete (Fig. 1) the pipe is ready to be coated. The coating itself is a two-component liquid anticorrosive, providing the most robust protection for your operations. Though this coating has traditionally been mixed manually, manual mixing can create disappointing results. As in any manual process, human error is inevitable, and preparing the wrong ratios or insufficient mixing can drastically affect the functionality of a coating. That is why Sulzer’s two-cartridge system provides the perfect solution (Fig. 2).

Fig. 2 Overview of the cartridge based mixing system.

Our plastic cartridge (Fig. 3) is pre-filled with the two-component coating. The dimensions on the cylinder meet the requirements of the mix ratio exactly, due to high metering accuracy. Sealed directly after the filling process by air-venting pistons, the coating is protected from external contamination until it is applied directly. To increase the flow of the two components and maintain a consistent temperature, the cartridges can also be pre-heated up to 55°C. This ensures a constant and reliable coating process.

Fig. 3: Cartridge with pistons, nose plug and retaining nut.

An application for precise and steady flow

Another challenge presented by manual application is the use of rollers and brushes to coat the pipelines. This leaves potential for exposed areas and incomplete protection which can only lead to increased maintenance in the future. Some choose to eliminate this possibility with the use of a multi-component high-pressure spraying device. However, such a device brings more challenges to overcome. Overspraying leads to a waste of coating material, not to mention the damaging impact such a liquid can have on the surrounding environment. The pressure exerted leaves a labour-intensive clean-up operation in its wake.

Overspraying pipe ends leads to a waste of coating material and can drip into the surrounding environment. Our dual-cartridge system uses the precise amount.

The spray tip on our application atomizes the mixed coating in the cartridges, creating a defined spray cone. After connecting the pneumatic dispenser to a properly sized air compressor, the system is now ready to use (Figure 6). The dispenser allows your teams to change the material flow rate and atomization rate of the air separately. Both are infinitely variable, even during the application. This leads to minimal overspray and thicker layers with a single coating step. Multiple mixer options now allow coatings to be applied in area that were previously difficult to reach.

A Sulzer employee is coating a pipeline — Fig. 4 Cartridge based application of a weld field joint coating.

A process your teams can work with

Exposure to hazardous materials during manual mixing and the strain of high-pressured spraying devices leave us in need of a new, more user-friendly process. At Sulzer we have designed a solution that eliminates both of these dangers. Unlike bulky high-pressure devices or a wide array of materials, our dispenser is easy to use and requires minimal training. Cartridges can be resealed so remaining coating can be used again for future applications, minimizing waste. We know that welding in the field leaves your unprotected pipe endings exposed to dirt, wind, and rain. Our application can be used irrespective of conditions and gets the job done quickly.

Such outstanding flexibility and reliable performance makes our cartridge-based system an exciting new solution for coating your weld field joints.

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