Valves in action -
Bleeding and venting valve EB 1.12
Degassing of natural gas liquids in crude oil production
During petroleum extraction, natural gas liquids come to the surface as by-product. Such associated gases, also known under the abbreviation NGL, consist of hydrocarbons and are either dissolved in the crude oil or overlie an oil zone in the form of a gas cap.
In past times such gases were often flared or vented, particularly in oil-producing regions with poor infrastructure, whilst nowadays they are processed to the greatest possible extent into a marketable product. As an example, they can be used for power generation or as basic material for the petrochemical industry. Due to their low evaporating temperature, these gases are stored and transported in the liquid phase. This makes good economic sense because less volume must be transported and pumps can be used instead of compressors.
Task // Venting of highpoints in liquid gas pipelines
At normal ambient temperatures, the plant pressure is above the evaporation pressure and ensures the liquid aggregate state of the NGL. However, highpoints in the pipelines pose a problem because the fluid that rests or flows in the pipelines degasses. This applies in particular to inhomogeneous mixtures because the evaporation points of different substances must be observed. If one of the substances evaporates, the pipeline will be blocked up over the entire operating period. In such a case the volume flows are lower and/or the differential pressure in the pipeline rises. To prevent this from happening, the resulting gas must be discharged as soon as possible out of the pipeline with the help of a continuous bleeding valve.
Solution // Compact venting valve for continuous operation
Since the pipelines in the plant are constantly pressurised, a start-up venting valve is not suitable for this application because it would not open when required. A self-acting float-controlled continuous bleeding valve is used as a solution. It discharges the gases without requiring external energy. The valve is made of highly corrosion-resistant deep-drawn stainless steel and designed to withstand temperatures of up to 130°C. This special valve gets along well with the significantly lower densities of the fluid which are partly at 640 kg/m³ only. The large and lightweight float has a high strength which is optimally suited for the operating pressure of the plant.
