Valve Actuation: The When, How and Why of Actuator Selection
11Pages

WHITE PAPER Valve Actuation: The When, How and Why of Actuator Selection A guide to actuators for upstream and midstream oil and gas applications By Jacqueline Onditi, Earnest Carey, David Montgomery and Lorenzo Colonna Preti

Valve automation dramatically improves control, precision and efficiency. While these advantages must be weighed against higher capital and operating costs, actuators are frequently found to be a cost-effective investment for most oil and gas applications. Once the decision to automate has been made, there is a wide — and often confusing — variety of actuators from which to choose. This paper is designed to make all these decisions easier by providing a quick-reading overview of: • The key factors to consider when making the decision to automate. • The most common types of actuators and the...

Is automation right for your application? Three factors typically encourage the decision to automate: • Frequency of operation—Valves that must perform a high number of operations or regularly perform modulating functions are good candidates for automation. • Ease of access—Automation increases the efficiency of valves in remote areas, unmanned installations, dangerous environments, the execution of lightly serviced processes, and the use of large valves requiring significant time or effort to operate manually. • Critical functions—Actuators offer significant advantages for shutdown or...

Electric actuation Electric actuators use electrical power to actuate a valve. While most of the basic technology used in electric actuators has been around since the 1930s, decades of incremental improvement have significantly increased their functionality while dramatically reducing their cost. In recent years, these advances have reached a tipping point that makes electric actuators the first choice for a wide variety of applications. Pros • Electric power is relatively inexpensive, easy to manage, and normally available to most industrial sites. The capital cost of electric actuators is...

Pneumatic actuation Pneumatic actuators are simple mechanical devices, able to incorporate a mechanical action or valve stroke by storing energy in a spring. A key advantage of this design is that a pneumatic actuator can always reach a predefined safe condition, even after the loss of its primary power supply (compressed air or electricity to the control components). This is the most important differentiator between pneumatic and electric actuators today. It’s also why nearly 90% of on/off piston-type actuators are spring-return (as opposed to double-acting). Pneumatics become the actuator...

Hydraulic actuation When size and weight requirements no longer make pneumatic actuators economical, the choice shifts to hydraulic actuators. Other specific factors can also drive the choice to hydraulics, usually as a result of the specific characteristics of hydraulic fluids. • Hydraulic control instrumentation is significantly more expensive, and is available from a much smaller supplier base. • While hydraulic cylinders must be stronger and thicker to contain higher pressures, they have much smaller dimensions. This size benefit is the primary reason to use hydraulic actuation. •...

Specialized actuators for pipeline applications Two major types of actuators lie outside the hierarchy detailed on page 3: gas-powered and electrohydraulic. Depending on the application, one of these might replace a counterpart in any of the three major categories. Both are primarily used by the midstream segment, most specifically by the pipeline industry. The defining characteristic of pipeline actuation is the need to automate large isolating ball valves, typically used to seal off segments of pipeline for routine process isolation, line break mitigation, pigging, and so on. Pipeline...

In its basic form, an electrohydraulic (EH) actuator combines an electric motor and pump assembly to pressurize a reserve of hydraulic fluid, a hydraulic control group to handle open/ close functionality, and a hydraulic actuator to operate the valve. This basic design can be expanded to include a wide range of electrical or electronic control components, allowing command and feedback capabilities equivalent to those of electric actuators. Pros • EH actuators combine the infrastructure simplicity of electric power with the advantages of piston-type actuators, including mechanical fail-safe...

Future developments Heavy-duty piston actuators There is growing industry demand for mechanical workhorses designed specifically to operate valves, typically with expected lifespans of 20 to 40 years. The goal is to improve mechanical efficiency, reliability and safety. Some initial progress is being made toward integrating piston actuator control components into plant SCADA or DCS systems. Most of these developments are being carried out by control equipment providers, both independently and as part of automation groups. More widespread use of electrohydraulic actuators EH trends on the...

Future developments (continued) Integrated operations and “smart” valves Sensor technology keeps getting cheaper, as does data processing capability. By combining the two, valves and actuators can be integrated with sensors that monitor operating pressures, torque and speed output, and wear of critical parts — all in real time. This potent combination enables more and better predictive maintenance, driving increased safety and efficiency. This fits in well with the increasingly popular trend of integrated operations, commonly known as IO, which relies heavily on real-time information...

About the authors Jacqueline Onditi — Specialist Product Manager, Heavy-duty Actuators David Montgomery — Senior Product Manager Jacqueline Onditi is a product manager of heavy-duty actuators for Flowserve Limitorque. From an accounting background, she started her career in an administrative role with a global actuator manufacturer in 1997, but an aptitude for technical issues and customer relationships quickly led her to transition into account management, and later to automation project management. Her background includes working closely with EPCs and end-user companies to develop...