无所畏惧的流量控制
流量控制：从天然气管道到液化天然气
执行器是石油和天然气行业中必不可少的设备项目。它们提供流量控制，这是工业应用中液体和气体的管理。在石油和天然气行业的所有三个领域都发现了流量控制设备：上游，中游和下游。本文将探讨传统管道围绕传统管道的挑战和机遇，以及在液化天然气（LNG）生产和运输中使用的管道的独特情况。
Flow control in traditional midstream pipelines
传统管道被认为是中游操作的一部分，将石油和天然气从一个位置移至另一个位置。这通常是数千英里的距离。它们是天然气生产区域（包括进口和LNG终端）与大多数消费者所在的人口中心之间的重要联系。这可以包括已从液化天然气重新使用的天然气。必要的流控制涉及最大化操作的可靠性和效率。执行器提供的精度和控制消除了人为错误，从而提高了自动化过程中的精度。但是，对管道的执行者最重要的考虑因素可以说是安全的。关键安全职责由执行器提供故障安全和紧急关闭（ESD）功能。持续不需要的石油或天然气流可以带来环境和人类安全的后果，但有效的关闭选择会减少或消除影响。
Valves that control the flow of oil and gas can be pneumatically, hydraulically or electrically actuated. The type of actuator chosen depends on several factors, such as power sources, location, type of control required, what fluid is being controlled and frequency of operation. Fluid powered actuators are often chosen for large- scale pipeline applications due to their fail-safe capability, their high torque and thrust capacity, and because they are fast acting. Appropriate customised control systems for high pressure gas supplies are often used. Categories of fluid powered actuators include pneumatic actuators, high-pressure pneumatic actuators and electro-hydraulic actuators. Spring-return pneumatic actuators are often used on both gas and oil pipelines as they provide the simplest and most reliable way of achieving a fail-safe action. Large actuators (such as Rotork’s GP range, which can stretch up to nearly 6 m, operating valves up to 68 inches) have on-board control panels for shut-down operation. This is the safety function that makes them ideal for use on pipelines. High pressure pneumatic actuators are used on pipelines where the high-pressure gas flowing in the pipeline is used as the power source to the actuator; no pressure reduction system is required. As well as ESD and safety functions, they can also provide other control functions such as low pressure close and line break. They are ideal for remote or hazardous environments. If necessary, they can be solar powered. Electro-hydraulic actuators are another option, combining simplicity of electrical operation with precision of hydraulic control, with the reliability of a spring to perform ESD and safety functions. Rotork’s Skilmatic actuator is a self-contained solution for remote locations and is designed for safety critical applications. It can close a valve in seconds if necessary and offers partial stroke and ESD capability as standard features. In 2018, Skilmatics were installed on a tank farm in India to fulfil an increase in demand of safety related duties as required local legislation. They operate 42" and 48" triple offset butterfly valves, providing tank overfill protection.
运输天然气的大型工业管道穿过许多偏远，具有挑战性的地形。在这里，压缩空气甚至电力可能无法使用。管道中的气体有时可能是执行器的唯一可用动力。此类重型执行器为管道上发现的大型阀门提供了常规和安全关闭职责温度波动。例如，在委内瑞拉北部的低温液化天然气管道上安装了执行器。管道在不同地点之间运输气体和LNG。执行器可以控制沿管道的球阀并提供ESD选项，并在LNG生产的所有阶段提供高水平的安全性，可靠性和安全性。液化天然气提出了自己的独特挑战。
液化的天然气
To turn specifically to LNG, many challenges seen in natural gas midstream pipeline applications apply to LNG as well. The main method of LNG transportation is by tanker/sea vessel, but pipelines also play a key role both in terminals, liquefaction facilities, storage and regasification systems. Safety must always be an overriding concern for operators. The fail-safe and ESD functions offered by actuators play an essential role in safe and reliable operations, shutting off product flow in an emergency and preventing further damage. This especially applies in often hazardous and challenging environments. For example, an LNG pipeline in south-west Chile was enhanced by the installation of fluid power actuators from Rotork. The LNG complex includes a sea terminal that receives LNG from tankers and a plant for regassifying and distribution by pipelines into central Chile. Heavy-duty, pneumatic and hydraulic actuators provide safety and shutdown duties. The exposed marine environment dictated the use of corrosion resistant materials in the packaged control systems and components supplied with these actuators. An LNG site in Queensland, Australia, installed CP and GP pneumatic actuators to operate butterfly valves; they are customised with control packages for bespoke operating duties. Large gas-over-oil actuators were installed on large mainline pipeline shutdown valves. The pipelines link natural gas production wells in the middle of Queensland to an LNG production plant at Curtis Island on the coast.
液化天然气的移动需要使用阀门和执行器，这些阀门和执行器可以承受涉及的极端寒冷温度。为了使气体转化为液体，需要-162°C。因此，带有液化天然气操作的阀门和设备必须能够在非常低的温度下运行，以在低温存储下提供所需的安全性和可靠性，对天然气进行重新认可以及在通常有害和具有挑战性的环境中运输中游阶段。通常需要低温阀。来自旋转船的GP和CP苏格兰轭执行器已在LNG终端使用，以在存储和重新化植物中操作球和蝴蝶低温阀。2020年，GP执行器安装在韩国液化天然气码头，该航站楼拥有四个LNG储罐和一个重新化厂。它们安装在终端的32英寸主管道上，并执行开放/关闭功能，以控制LNG和天然气的气态形式的流动。在紧急情况下，可以通过在任一方向上提供的故障安全功能立即切断流动。印度的天然气管道也使用了GP执行器。提供了80多种以操作埋藏的球阀，以满足ESD的要求，该要求沿着西南海岸的高容量液化天然气进口码头的879公里管道。
电动执行器在终端和相关地点的天然气和液化天然气的流动中也发挥作用。许多操作要求阀门在设定位置之间反复移动；电动执行器提供精确的操作，并具有分辨率和可重复性。IQ3电动执行器于2019年安装在马来西亚现场，该站点建造了重新设备，LNG储罐和泊位，用于装载和卸载LNG载体船。执行器现在控制从端子到载体的流动。CVQ电动执行器也已安装在澳大利亚苏拉特盆地的LNG站点上。他们在分离器上操作球阀。电动执行器由于其可靠性，安全性和效率而被珍视。许多人提供爆炸性认证，适合在危险和危险环境中使用。
重新验证的流量控制
In order for LNG to be transformed back into natural gas, a process called regasification is required. The regasification stage of LNG usually takes place at import terminals where LNG has been moved onshore. It must be returned to its gaseous state for onward transportation through traditional pipelines to be used for fuel, power generation and heating. Pneumatic scotch yoke actuators are often used, performing open/close functions for both LNG and natural gas control. Fail-safe functionality can be provided in either direction due to the spring-return module inside the actuator. Vaporisers, a key component of the regasification process, have valves that are often small and compactly arranged. They require compact and fast acting actuators to operate them. Other applications at this stage include controlling gas outlet valves, vapour discharge, tank pump discharge and unloading valves.
结论
传统的大规模管道（要在数千英里的土地上运输天然气）和用于液化天然气生产和加工的较小规模管道都需要执行器。执行器是控制液体和气体的关键设备，可在整个中游区域的各种应用中提供可靠，高效且安全的阀门操作。在液化天然气内，阀门通常是低温的，操作它们的执行器必须坚固，坚固且能够在苛刻甚至危险环境中成功工作。