Introduction to Block Valves (On-Off Valves)

GOALS for this module 

• Provide valve definitions and key concepts
• Introduce different design options for block valves
• Present the key features of selected block valve designs
• Introduce the API 6D specification for valves
• Provide the information required to specify/purchase a block valve

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DEFINITIONS and KEY CONCEPTS

What is a Valve?

A valve is a mechanical device used to control the flow of a fluid (such as gases, liquids, or slurries) through a system of pipes or tubes. 

What are the main types of valves?

1. Block valves: valves that block the flow when in closed position. Aka "On-off valve". 
   • Warning: a block valve should be used in fully open or fully closed position only, not in partially open position for throttling.
2. Control valves: valves that regulate the flow by varying the size of the flow passage as directed by a signal (e.g. temperature or pressure) from a controller.
3. Pressure relief valves/Safety valves: valves that limit the pressure in a system by automatically discharging the pressure when it exceeds the set point. 

What are the key components of a block valve?

• Body: the valve body is the pressure containing component, preventing external leaks (i.e. release of contained fluid into the environment).
  • The body is usually made of forged parts or cast parts.
• Closure member (aka "Obturator"): it is the part of the valve that permits or prevents flow through the valve. It is the component that qualifies the type of valve.
  • In our presentation it can be a Ball, Gate, Plug, or Disc.
• Seat: it is the part that contains the surface upon which the obturator rests to prevent flow through the valve.
  • It can be metal-based or "soft" (with either an elastomeric or polymeric seal); fixed or spring loaded.
• Stem: it is the part that drives the closing member and allows for opening-closing operation.

BORE SIZE

Block valves can be categorized based on the size of the bore within the closure member, commonly referred to as "port size".

• When the bore size matches that of the pipe, the valve is known as a "Full Opening Valve" also referred to as "Full Port".
• If the bore size is smaller than that of the pipe, the valve is referred to as a "Reduced Opening Valve", sometimes known as "Regular Port".

It is important to note that valves featuring non-circular openings within the closure member should not be classified as full opening valves.

Furthermore, valves with a reduced opening result in a more significant pressure drop across the valve compared to full opening valves.

DESIGN OPTIONS

The most common design options, based on the type of closing member, are:

1. Ball valves
2. Gate valves
3. Plug valves
4. Butterfly valves

The tables below offer a quick snapshot of the key features of each design type.

BALL VALVES

GATE VALVES

PLUG VALVES

BUTTERFLY VALVES

INTRODUCTION TO THE API 6D SPECIFICATION

What is API?

The American Petroleum Institute (API) is a trade association in the United States that primarily serves the oil and natural gas industry. It was founded in and has since played a significant role in the development and promotion of industry standards, best practices, and advocacy for the oil and gas sector. 

What is API 6D?

For more information, please visit A105 Valve Balls.

API 6D is the specification that defines the requirements for design, manufacturing, materials, welding, quality control, assembly, testing, marking, documentation, and process control of axial, ball, check, gate, and plug valves for application in the petroleum and natural gas industries. 

Why is API 6D important?

API 6D is an industry recognized standard and its compliance is frequently required for valves for oil & gas applications.

PHMSA (the Pipeline and Hazardous Materials Safety Administration, which is part of the US Department of Transportation) requires API 6D compliance for all the valves used in Gas Transmission systems in the USA. Compliance to API 6D ensures quality, safety and purpose fitness.

INFORMATION REQUIRED TO SPECIFY/PURCHASE VALVES

When you specify/purchase valves there is a minimum set of basic information that is required to be transmitted to the supplier to make sure the valves will meet your expectations.

Additional information is also highly recommended.

Minimum set of basic information

• Valve design option
  • For example: Ball OR Gate OR Plug OR Butterfly
• Valve Size 
  • In North America, size is normally expressed as NPS (Nominal Pipe Size), which is typically measured in inches (can be dimensionless). In Europe, it is normally expressed as DN (Nominal Diameter), which is typically measured in mm (can be dimensionless).
  • For example: NPS 2" OR DN 50.
• Pressure-temperature rating
  • Typically expressed by a class numbers, as defined in ASME B16.34. Classes are defined as the maximum pressure that the valve can withstand at a specific temperature, for each steel group. The class selected should correspond to the intended maximum pressure and temperature range for the valve's intended usage.
    For example: Class 150 OR Class 600. 
  • Warning: please note that Class 150 does not mean that the valve is rated for 150 psi (or 150 bar). Just as a reference, the Maximum Acceptable Operating Pressure (MAOP) for a carbon steel valve (for example, made in A105) is 285 psi when used between -20F and 100F. The MAOP for the same valve at 500F is 170 psi. 
• End connections
  • For example: Flange by Flange (or FxF) OR Weld by Weld (WxW).
  • In the case of flanges, the type of flange, for example RF (Raised Face) or FF (Flat Face) or RTJ (Ring Type Joint), and the flange standard (ASME B16.5, etc.) should be specified.
  • In the case of weld connections, the thickness of the pipe and the pipe material should be specified.

Additional information - recommended

• Fluid
  • For example: clean natural gas OR sour gas with 15% H2S.
• Operating conditions
  • Operating temperature range; Operating pressure range.
• Port Size
  • Full Port OR Regular Port
• Specific materials, as needed
  • If any specific material is needed/preferred for the steel body (e.g. A105 or A350 LF2) or for any other components, like the seat (e.g. PTFE/Teflon or HNBR).
• Type of Operator
  • For example: Lever handle OR 2" square nut OR gear operator (with vertical/horizontal input; with or without handwheel) OR actuator.
    In case of actuator, additional information is required.
• Type of painting/coating
  • For example: epoxy coating for buried service OR manufacturer's standard. 
• Compliance requirements to specific standards or design codes
  • For example: API 6D.

Many valve users developed their own valve specification. In that case, please share the specification with your valve supplier.

Also, many valve users have their own Approved Vendor List (AVL) or Approved Manufacturer List (AML). These are documents that include the vendors/manufacturers approved for supplying a specific type of equipment (for example: valves OR actuators). Usually, the process to add a new Vendor/Manufacturer on an AVL/AML entails a detailed scrutiny, that includes desk activities (analysis of drawings, references, quality system, certifications, etc.) and an on-site audit/inspection at the manufacturer's facility. If you have an AVL/AML for valves, please share it with your valve supplier.  

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The Impact of Butterfly Valve Installation Orientation and Spatial Layout on Valve Performance -08-01

The butterfly valve, as a compact, quick-opening, and low-resistance regulating valve, is widely used in industries such as water supply and drainage, HVAC, power, chemical, and paper-making. However, in practical engineering applications, improper consideration of the butterfly valve’s installation direction and spatial arrangement often leads to valve operating abnormalities, decreased sealing performance, and deviations in control accuracy. In severe cases, it can even cause system failures or frequent maintenance, resulting in unnecessary economic losses. Therefore, a correct understanding of the impact of installation orientation and spatial layout on butterfly valve performance is essential to ensure its reliable operation and extend its service life.     1. The Impact of Installation Orientation on Butterfly Valve Performance   (1) Fluid Flow Direction and Its Effect on Sealing Performance For centerline butterfly valves, where the valve disc rotates around the valve shaft, the force is relatively symmetric, and the fluid flow direction has little impact on the sealing performance. Therefore, the flow direction requirement is not strict during installation. However, for eccentric butterfly valves, especially double-eccentric and triple-eccentric types, the seal design is based on the "flow-assisted compression" principle. That is, when the medium pressure comes from the specified direction, it pushes the valve disc toward the sealing seat, thereby enhancing the sealing effect.   If the valve is installed in the opposite direction of the flow arrow marked by the manufacturer, the reverse fluid flow will wash the valve disc. Not only will the expected sealing effect not form, but it may also create gaps between the sealing surfaces, accelerate valve seat wear, and cause internal leakage, making it impossible to close the valve completely. Therefore, the installation of eccentric butterfly valves must strictly follow the flow direction requirements.   (2) Valve Shaft Orientation and Its Effect on Opening/Closing Torque and Actuator The installation orientation of the valve shaft (horizontal or vertical) has a significant impact on the opening/closing performance, valve body stress, and actuator life. Most medium and small-sized butterfly valves are installed with the valve shaft in the horizontal position. This method facilitates the alignment of the valve body with the pipeline and the arrangement of the actuator.   However, for large-diameter butterfly valves or those installed in high locations or vertical pipelines, the valve shaft is often vertical. In this position, the weight of the valve disc directly acts on the valve shaft, especially when the valve disc is in the open position, where its center of gravity deviates from the axis, creating a large eccentric torque and increasing the axial load during opening and closing. If the actuator does not account for this additional load, it may result in po...

Dervos Becomes YPFB's Qualified Valve Supplier -07-16

YPFB (Yacimientos Petrolíferos Fiscales Bolivianos) as Bolivia's state-owned oil and gas company, plays a critical role in the exploration, production, and distribution of oil and natural gas across Bolivia. It has a strong commitment to quality and innovation. DERVOS VALVE is honored to have passed the qualification review and become one of contract valve suppliers of YPFB.   • Supplier Qualification Requirements for YPFB Becoming a supplier for YPFB requires meeting several stringent qualifications. YPFB looks for suppliers with a proven track record of reliability, technical expertise, and product quality. This includes compliance with international industry standards and certifications,along with the ability to provide high-performance products that meet the specific needs of Bolivia’s oil and gas industry. The process also involves submitting detailed technical documentation, including certifications, safety records,and previous successful project references.   •  Application Process to Become a YPFB Supplier The application process to become a certified supplier for YPFB is highly competitive and rigorous. The first step is to submit an official application, followed by a review of the company’s credentials. Dervos Valve underwent this process and provided comprehensive technical documentation, including product specifications and compliance with safety standards. Our team also participated in interviews and site visits, showcasing our manufacturing capabilities and commitment to quality. DERVOS VALVE will supply a range of valves to YPFB for use in their oil and gas operations, including high-performance ball valves, gate valves, globe valves, and check valves. These products are crucial for ensuring the safety and efficiency of operations in challenging conditions.   Dedicated to consistent product quality through daily operations, we ensure excellence in performance. Our ongoing commitment is providing partners with professional support and premium services, fostering mutual growth and win-win success.  

Global Partners Reunite to Celebrate Dervos' 17th Anniversary Milestone -07-03

To mark this milestone in Dervos Valve’s journey, we came together not just to celebrate, but to connect with the partners who have supported us along the way. This anniversary is a tribute to enduring partnerships and a sha- red vision for the future.   On the occasion of Dervos Valve’s 17th anniversary, our valued partners were specially invited to visit our headquarters for in-depth, face-to-face exchanges with the team. These meaningful interactions deep- ened mutual understanding andtrust, laying a solid foundation for even stronger cooperation in the future.   Accompanied by our team, the clients toured the office area and were introduced to colleagues from various departments. The interactions were relaxed and friendly, creating a warm atmosphere that further strengthened mutual understanding. Following the tour, our sales team delivered a themed presentation on “Dervos 17th Anniversary,” offering the clients a comprehensive overview of the company's development journey, core strengths, and service philosophy. We also expres- sed our heartfelt gratitude and warm welcome to our valued partners. Through this session, the clients gained a deeper understanding of Dervos, enabling us to better tailor our services to their needs. They expressed strong appreciation for Dervos’ steady growth and thanked us for inviting them to be part of this meaningful celebration.   In front of the company’s cultural wall, clients took a moment to sign and leave messages, expressing their well wishes for Dervos. This moment not only reflected cultural recognition but also a genuine expression of the emotional bond and trust shared through our partnership.   Next, we arrived at the highlight of the anniversary celebration— the Dervos Valve 17th Anniversary Gala Dinner, a moment of gratitude and shared celebration. We arranged a visit to the "Yu Jian Minnan" Cultural Park for our clients, where they explored the ancient architectu- ral district and experienced the traditional art of rubbings, immersing themselves in the charm and craftsman- ship of Chinese culture.   In the evening, a red carpet was laid out in front of the hotel, where the Dervos team warmly welcomed guests, coming together with partners from around the world to witness this moment of honor. As the lights came on, the anniversary gala dinner officially began. The venue was decorated in a grand and festive style, with a warm and lively atmosphere. The event kicked off with a performance that blended both Eastern and Western cultures,featuring a lineup of classic foreign songs and traditional Chinese pieces, showcasing Dervos' open and inclusive brand spirit, with a global outlook. During the interactive games and lucky draw sessions, guests actively participated and enjoyed themselves, with laughter and joy filling the air. This lively atmosphere showcased the cohesion and energy of the Dervos team.   As the familiar melo...

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