The role of flow control in midstream storage applications
The role of flow control within oil and gas applications
Flow control is the management of liquids and gases. Actuators are key pieces of equipment that allow for automation, controlling the valves at the heart of the process. They can be electrically, pneumatically, hydraulically or electro-hydraulically powered, depending on power supply and customer requirements.
Electric actuators have varied roles within a large variety of applications in the oil and gas industry. They can control the flow of water, gas crude oil and condensate at the upstream applications, while in midstream applications isolating actuators are used for day-to-day flow control, fail-safe actuators are for critical safety duties and modulating actuators for process valves. Electric actuators (especially intelligent electric actuators, because of their ability to capture data) are increasingly the preferred choice for oil and gas operators. Powered by electricity, they are reliable, efficient, precise and simple to use. A watertight enclosure (such as one that is double-sealed) protects internal elements from the ambient environment, making actuators durable and robust. Actuators on oil and gas sites should have explosionproof certification, as part of the high degree of safety required within production and processing. They often provide Emergency Shutdown (ESD) and shutdown capabilities. Flow control safety provisions on tank farms are largely a combination of explosionproof certification and environmental protection (such as double-sealing). Electric actuators are also not subject to the negative impacts some flow control systems can have on the environment. Pneumatic actuators powered by gas have traditionally been used. Spring-return and diaphragm pneumatic actuators, for example, vent this gas (often methane) into the atmosphere. Electric actuators negates this, aiding in compliance with emission mandates that are increasingly imposed upon operators to aid in efforts tackling the climate crisis.
Tank farms
Tanks farms and storage terminals are a fundamental and essential part of midstream oil and gas operations. They are used for natural gas, crude and refined oil, and finished oil products, and are therefore often attached to or found near to refineries. These products are stored in tanks before they are moved (for example via pipelines) and enter the downstream stage of oil and gas activities. They can be stored for some time (depending on product) and international supply and demand will affect what happens, and when. This level of control is part of the global market for oil and gas; it can include actions like reserves of oil and gas, as seen in the Strategic Petroleum Reserve in the USA. Tanks and storage facilities can be above and/or below ground. Flow control plays a key role in most midstream applications. This occurs within the wide range of individual applications within terminals, such as receipt, storage and loading, pump stations, metering skids and blending systems, transfer safety/shutdown options and liquefaction (for Liquified Natural Gas [LNG]). On tank storage systems, actuators can be found in tank overfill protection, condition monitoring and tank gauging/measuring. Isolating actuators are used for routine flow control around the plant, fail-safe actuators for critical safety duties and modulating actuators for process applications. For example, 100 intelligent electric IQ3 actuators were installed at Moroccan terminal in 2019. The site has a capacity of 532,900 m³ for petroleum products and blending components and is a critical operation for oil provision in north-western Africa. The actuators operate gate and butterfly valves on tank inlets and outlets.
Safety
Flow control solutions play a key role within safety provision on midstream operations such as tank farms/terminals. Appropriate care and control is not only necessary to ensure smooth operation, but to prevent a safety incident like the Buncefield fire in 2005. Here, a storage tank overflowed and the vapour cloud ignited to cause a devastating fire. Safety systems to prevent this sort of incident are essential. Tank failures and safety incidents can lead to huge hazards and costs. Any site that contains flammable materials must always consider safety as the paramount operating consideration. Flow control systems contribute to this. Tank overfill protection is an important point to consider; this stops material overflowing from the tank (and the loss of product) and the subsequent safety concerns. Actuators operate isolating valves (inlets and outlets) and control valves (in some cases). All these elements of tank overfill systems require certified safety systems for filling, emptying, tank blanketing and level monitoring. Equipment should be explosionproof, SIL 2/3 capable and suitable for use in SIS systems, operating to API/ANSI Standard 2350 (the minimum standard operators must work to).
Other safety considerations include ESD/shutdown capabilities provided by actuators. They can stop the flow of oil and gas when required. This can be on loss of ESD signal, loss of power supply, or both, depending on customer specification. Making sure that flow finishes in a safe operating state avoids both safety and monetary concerns. For example, Rotork Skilmatic electro-hydraulic actuators control Remote Operated Shut-off Valves (ROSOV) at multiple tank farms in India. They provide a spring-return fail-safe control action, ensuring high degrees of safe operation. The choice of electro-hydraulic actuators provides operators with the speed and flexibility of hydraulic operation and the reliability of spring action with the convenience and control benefits of electric actuators. They are therefore a popular choice for providing safety functions. Another example of the use of Skilmatic actuators is at a terminal in Rotterdam. The Botlek Tank Terminal has 34 storage tanks, providing a combined storage capacity of 200,000 cubic metres, and benefits from ESD functionality from over 50 Skilmatics on site. They position inlet and outlet ports of the storage tanks (and on the marine and truck loading bays) to a pre-determined safe position.
Asset management
Downtime can be costly and disruptive. Within oil and gas production, tank farms and terminals require frequent operation of key flow control assets to continue to be productive and profitable. Sites that require flow control need actuators to consistently provide reliable, safe, efficient operation. Interruption of flow control at a tank farm, for example, results in an inability to achieve the optimal mass balance and accuracy of blending needed. Any unplanned downtime will detract from key operational goals. The maintenance and upkeep of these important assets must therefore be at the forefront of operator’s minds. Innovations within flow control technology can now contribute to the continued availability of assets, increasing essential uptime. Key in this is the use of data to improve operational effectiveness.
Asset management systems such as Intelligent Asset Management from Rotork exist to ensure actuators continuously operate an optimum performance level, allowing sites to work reliably, efficiently and safely. They contribute to the essential uptime needed in midstream oil and gas operations. Unplanned downtime caused by a lack of asset availability can cause economic loss and reputational damage, irrespective of how long a site is offline for. Part of the Industrial Internet of Things (IIoT), a system like Intelligent Asset management allows operators to access the data within intelligent actuators – and act on it to improve performance and uptime to prevent the kind of damage mentioned above. Intelligent electric actuators contain data loggers that can provide a large amount of data, such as the number of valve operations, alarms and valve torque profiles. Torque average, deviation, peak levels and opening/closing torque are especially valuable and aid in understanding an actuator’s health. Sudden changes can indicate a potential problem. A holistic asset management system that analyses this data assists operators in running assets/a site at an optimum level, maximising productivity and reducing operational risk. A system than removes the need to manually review data lifts access barriers to data but instead present it in a straightforward and clear manner.
Ensuring asset availability at tank farms can also be managed by battery technology. Such is the importance for process uptime on these sites, battery actuation can provide a solution for power supply concerns. If power is interrupted or can be intermittent, flow control that can continue with the help of a battery maintains operation and production activities. Such solutions can continue to operate while power is unavailable or bring the process to a safe stop; this safety provision is an additional benefit. Rotork’s intelligent electric IQT part-turn Shutdown Battery, for example, can fail-safe, fail-close, fail-open or stayput on battery power. Processes will finish in a safe operating state, preventing safety and monetary consequences. Innovative battery functionality of this kind assists tank farm operators in achieving a high level of uptime, as well as safety benefits.
Conclusion
Tank farms and storage terminals are critical within the oil and gas industry. Flow control plays an important role in multiple applications on tank farms and storage terminals, such as overfill protection, condition monitoring and tank gauging/measuring. Actuators also provide essential safety functions within an environment where safety considerations must be of paramount importance.