15 February 2022

BULK PIPING MATERIAL SELECTION FOR OIL & GAS INDUSTRY

Majority of the pipelines worldwide, whether they are for water, oil and gas, or any other utilities are constructed using Carbon Steel. These are readily available material which have great mechanical properties making them apt for the bulk piping purpose. They have excellent weldability, and the material is as such whose corrosion resistance can be enhanced leveraging techniques such as lining, coating, chemical inhibition among others. Add to this the cost-effectiveness and ease of use are a bonus.

However, PetroGas Piping ensures involvement of corrosion engineers in early stages itself to design a perfectly engineered bulk piping pipelines and other apparatus such as valves, flanges and other fittings. Their involvement ensures that there won’t be any last-minute failures or technical glitches due to corrosion influenced issues in material selection and design.

Therefore, we need to gather as much information about the operating environment and any other relevant factors. This helps in designing equipment and structures which are more efficient and corrosion resistant. It is imperative to check the data and operating conditions for material selection. Factors to note are:

• Water Content—Water is critical contributor to corrosion. This holds true especially for oil pipelines as oil is noncorrosive and provides a viscous film on metal surface of bulk pipes.
• Gases— These have major impact on the material given the presence of carbon dioxide, oxygen, hydrogen and sulfides.
• Pressure and Temperature—Corrosive reaction can also happen because of pressure, wherein the partial pressure of gases makes them soluble which reacts with the inner lining of the pipeline. Also increasing temperature is directly linked to increased corrosion. Thus, it makes it imperative to know the minimum temperatures and pressure required for the commodity being transferred, whether it is oil & gas or water. Accordingly, one will choose the material.
• Flow Rate— It’s also important to know the minimum and maximum flow rate to know the corrosion risk. A high flow rate, especially if it surpasses the erosional velocity then erosion takes place. While very low levels of flow rate will result in stagnation of liquids and solids, thereby resulting in under-deposit corrosion.
• pH levels—pH is usually affected by CO2 and H2S and bicarbonates.
• Design Life—This further has significant impact on the cost aspect of material selection. A short design life allows the use of carbon steel pipes without any worry for corrosion control, while a long design life necessitates a number of corrosion control measures.

Pipe exteriors should be such that they can withstand the external environment and demanding conditions, whether it is high and ambient temperature, fluctuating levels of pressure due to varying levels of humidity, or any other wear and tear. Therefore, it is essential to consider the fluid type which will help determine the best material to sustain the internal temperature and pressure.