High Performance Butterfly Valves for Challenging Process Fluid Conditions

High performance butterfly valves handle challenging
 media and process conditions.
Image courtesy Flowserve - Valtek Control Products

Industrial process control applications can present stringent and challenging performance requirements for the physical equipment and components that comprise the process chain. The valves employed in fluid based operations need to be resistant to the impact of extreme fluid conditions, requiring careful design and selection consideration to assure proper performance and safety levels are maintained in a predictable way.

Industrial valves intended for extreme applications are generally referred to as severe service or high performance valves. While there are plenty of published and accepted standards for industrial valves, one does not exist to precisely define what constitutes a severe service valve.

So, how do you know when to focus valve selection activities on severe service or high performance valves, as opposed to those rated for general purpose? There are a number of basic criteria that might point you in that direction:

• Extreme media or environmental temperature or pressure
• High pressure drop operation that may cause cavitation
• Rapid or extreme changes to inlet pressure
• Certain types or amounts of solids contained in the fluid
• Corrosive media

Certainly, any of these criteria might be found in an application serviceable by a general purpose valve, but their presence should be an indicator that a closer assessment of the fluid conditions and commensurate valve requirements is in order. The key element for a process stakeholder is to recognize when conditions are contemplated that can exceed the capabilities of a general purpose valve, leading to premature failure in control performance or catastrophic failure that produces an unsafe condition. Once the possibility of an extreme or challenging condition is identified, a careful analysis of the range of operating conditions will reveal the valve performance requirements.

There are numerous manufacturers of severe service or high performance valves, each with specialized product offerings focusing on a particular performance niche. Flowserve, under their Valtek brand, manufactures the Valdisk high performance butterfly valves ranging from NPS 2-52 and ASME class 150, 300, 600, 900, 1500 pressure ranges. The valve design is ideal for manual or automated actuation, installed with a manual hand gear, electric actuator, or a pneumatic actuator. Seats are available as soft or metal on this double offset butterfly valve that provides tight closure for bi-directional flow. Construction materials include carbon steel and stainless steel. A range of options and variants are available to customize the valve build to suit a replacement or new installation.

There is more information available about the Valtek high performance valve offering. Share and discuss your special requirements with a valve specialist. They have application experience and access to technical resources that can leverage your own process knowledge and experience into an effective solution.

Scotch Yoke Valve Actuators

Scotch Yoke Pneumatic Valve Actuator
Courtesy Flowserve - Automax

A Scotch yoke is a mechanical linkage arrangement that converts linear motion into rotational motion. A common usage of the mechanism found in modern industry is valve actuators for quarter turn valves with high torque requirements. These applications would emerge most frequently in chemical and oil and gas industrial installations.

Quarter turn valves, such and ball, plug, or butterfly valves, only require a 90 degree rotation from their fully closed to fully open positions. In this case, the Scotch yoke is not used to produce continuous rotating motion, as it may in some engine applications. For the valve actuation case, the Scotch yoke functions much like a hand on a lever. The pneumatic variants use air pressure to drive the slider in one direction until a preset stop position is reached. Usually, a spring provides a counterforce that will drive the valve to a desired fail-safe stop position in the absence of air pressure. Other combinations of driving force and fail-safe operation are available to suit differing application needs.

Diagrammatic representation of Scotch yoke valve actuator
Illustration excerpted from Automax RG Standard Pneumatic Valve Actuator IOM 
with text added

The drive assembly consists essentially of a slider, a pin, and the yoke. The slider is moved laterally by whatever power sources are appropriate for the unit (pneumatic, hydraulic, spring, hand wheel, etc.). The pin is affixed to the slider and extends through a slot in the yoke. One end of the yoke is mounted to the valve shaft. As the slider is driven through is range of motion, the pin moves with the slider and forces movement of the yoke. This movement of the yoke translates into rotational force on the valve shaft and the repositioning of the valve trim.

Selecting and configuring the right actuator and valve for any application benefits from consultation and cooperation among the process engineers and valve automation specialists. Share your process valve and automation challenges with experienced professionals, combining your own process knowledge and experience with their product application expertise to produce an effective solution.

Oil and Gas Wellhead Valves Meet Special Application Challenges

Slab Gate Valve
Courtesy Flowserve - Valbart

Industrial valves are manufactured in a huge array of configurations to accommodate the specialized needs of a broad range of industrial process applications. The oil and gas industry is but one segment of many throughout the industrial sphere that presents its own set of application specific criteria.

Oil and gas production, essentially pulling raw material from the earth, has unique valve performance challenges. Extreme pressure and abrasive or erosive material are common elements of oil and gas production at the wellhead. The valves also need to tolerate the range of outdoor temperatures at the production site. Safe and reliable operation throughout these and a range of other conditions are part of the design criteria for these valves. Here are some of the specific valve variants and configurations applied in the oil and gas industry at the production wellhead.

Rising Stem Ball Valve
Courtesy Flowserve - Valbart

• Slab Gate Valve - Provides metal to metal seal and employs parallel gate and seal with a preloaded means of assuring positive upstream and downstream seal. Full port design allows for pigging.
• Expanding Gate Valve - A parallel expanding gate seals positively against both seats, which are protected from the flow medium in the open and closed positions.
• Mud Gate Valve - Designed to provide positive closure under rigorous field conditions with abrasive media. 
• Adjustable Choke Valve - Designed to regulate production well flow and downstream pressure. Different trim configurations provide appropriate levels of control.
• Needle Adjustable Choke Valve - Utilizes different trim arrangement than other types to provide good flow management, abrasion resistance, erosion resistance, and reliable service over a long life with low maintenance requirements.
• Check Valve - Check valves of various types are utilized throughout practically all fluid flow operations, essentially anywhere that fluid is supposed to flow in only one direction. Oil and gas production presents some special conditions of abrasion, erosion, and pressure that call for special accommodation in design and materials of construction.

There are other specialty valves employed at or near the wellhead, but the key take away here is that oil and gas production generally cannot be accommodated by general purpose valves. Share your oil and gas production challenges with a valve specialist. The combination of your process and production field experience with their product expertise will produce effective solutions.

Electronic Line Break Detection - Pipeline Monitoring

Electronic line break detector unit
Courtesy Rotork

There are some process control challenges for which you may need to establish or produce a solution of your own design. These should be applications where a pre-engineered option or product is not available. A manufactured product for your application likely is comprised, not only of appropriate physical attributes suitable for the application, but also the experience gained from numerous successful iterations solving the same problem, challenge, or issue you currently face. There can be expertise, knowledge, and experience provided as part of a hardware item, and bringing that knowledge and experience of others into the solving of a process control challenge is sound practice.

Pipelines, when considered from differing organizational vantage points:

• A source of revenue
• A means of transportation
• A pipe with fluid in it
• An ongoing operation requiring monitoring and control
• An extensive physical presence with an associated risk element

Pipelines are all those and more. Regardless of your vantage point, line breaks are decidedly negative events worthy of early detection and rapid response. Part of that solution is available in the electronic line break detection device from Rotork, globally recognized leader in the design and manufacture of valve actuators employed throughout the industrial sphere. The ELB model incorporates a set of features and capabilities that can be used to detect and respond to gas pipeline breaks. It is a self contained unit employing technology to detect line breaks and execute a predetermined response.

Read more about the ELB from Rotork in the document included below. It provides a detailed outline of the operational features of the unit. Share your fluid system control challenges with an experienced application team, combining your process knowledge with their product application expertise to develop effective solutions.

Electronic Line Break Protector for Fluid Systems from CTi Controltech