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Equipment service life matters

Published by , Editorial Assistant
Hydrocarbon Engineering,

Andrew Petticrew, Head of Global Sales for Automated Weld Overlay at Sulzer:

As oilfields and reserves reach maturity, companies in the oil and gas sector need to extract and use resources from sour fields. These contain elevated concentrations of highly corrosive hydrogen sulfide (H2S). To successfully process sour crude oil without allowing H2S to take a toll on equipment, companies in the oil sector need to implement suitable protection strategies that maximise equipment integrity and service life.

Sour crude oil has a total sulfur level above 0.5% w/w and tends to contain higher volumes of carbon dioxide (CO2), which contributes to creating harsh and aggressive processing conditions. Therefore, while corrosion is a common issue in the oil industry, when sour feedstocks are used, oil processing facilities face a higher risk of equipment damage associated with severe acidic corrosion.

In addition to selecting robust components featuring high-quality, corrosion resistant materials, processing facilities also need to create appropriate maintenance strategies aimed at maintaining and restoring the integrity of their equipment in order to maximize service life and uptime. When corrosion is compromising oil distillation operations, companies have a limited number of options.

One solution consists of replacing part of or the entire unit that has been degraded. While this allows oil processing plants to restore the facility’s initial capabilities, it is also a particularly costly and time-consuming operation. Alternatively, plants can rely on thermal-spray coatings to the internal surfaces of distillation columns, coker units and vessels. While this is an economical approach, the surface treatment prevents corrosion only for a limited time. This means that it needs to be applied on a regular basis, resulting in regular shutdowns. Even more, this method does not address surface thinning or loss of mechanical integrity.

Automated weld overlay is an advanced repair and corrosion protection method that extends the service life of distillation vessels exposed to the highly corrosive chemicals in sour crude oil.

A better corrosion protection option – weld overlay

There is a third alternative that greatly outperforms these two solutions: weld overlay. This is a welding process where layers of hard-facing and/or corrosive-resistant alloys are applied onto a parent material, i.e. the internal surfaces of oil processing units. In this way, the weld overlay substrate can be used to repair damaged surfaces and restore initial wall thicknesses. In addition, it can provide extra protection from the corrosive components of sour crude oil. As a result, this repair method offers a comprehensive, time-efficient, economical and long-lasting solution.

Weld overlay offers a high level of flexibility and versatility, as it is suitable for oil distillation vessels of any shape and size, and it is possible to choose the type of alloy, the layer thickness and the area that needs to be covered. In addition, a wide range of welding processes are available, in order to address specific requirements and applications.

Automated weld overlay is one of the most advanced and well-rounded repair and corrosion protection methods currently available. It can deliver high-quality and highly consistent depositions, even on irregular surfaces or in areas that are hard to reach by human operators. Additional benefits of using a fully automated process include faster weld speeds and decreased scrap volumes.

Get more from automated weld overlay

An example of a highly effective automated weld overlay system is Sulzer’s CladFuseTM. This uses a programmable logic controller (PLC)-based robotic index arm that moves a welding torch and an oscillator in order to create weld beads.

A laser profilometer monitors the topography of the surface being welded, creating a detailed and accurate surface map during the weld process. As a result, the laser-levelled track system can detect small surface imperfections that require thicker or thinner weld overlay and take this into account in real-time. All the relevant process parameters, such as carriage speed or bead thickness, are controlled by the PLC according to the most suitable weld sequence. This is identified during planning stages and backed by extensive simulations.

Sulzer is a leading provider of specialised field services, with over 40 years of experience in maintaining, repairing and revamping towers, drums and vessels. Thanks to this extensive knowledge, Sulzer has developed this highly advanced and reliable system which, maximises equipment service life and uptime whilst minimising maintenance costs and capital expenditure (CAPEX). Sulzer’s CladFuse can help processing facilities efficiently process sour crude oil.

Sulzer’s CladFuseTM automated weld overlay technology is regulated by a programmable logic controller (PLC). Operators can communicate with it, adjusting relevant process parameters by means of a human-machine interface (HMI).

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