Showing posts with label butterfly valves. Show all posts
Showing posts with label butterfly valves. Show all posts

Friday, November 16, 2018

What is a Triple Offset Valve (TOV)?

Triple Offset Valve
Click for larger view.
As the name implies, there are three separate offsets designed into the triple offset valve. Two of the offsets apply to the location of the shaft with respect to the center line of the bore and the center line of the disc/seat sealing surfaces.

The third offset in the design is the axis of the seat cone angle that is inclined from the center line of the valve bore. This eliminates rubbing of the seat/seal contact surfaces during operation and preserves sealing integrity over the cycle life of the valve.

The contact is made in only the final point of closure, acting as a mechanical travel stop which prohibits over-travel of the disc.

Applications and Method of Control

A triple eccentric or triple offset butterfly valve should be used when the application requires bubble tight shut-off, but does not allow the use of a rubber-lined butterfly valve due to low/high temperatures and high pressure. The triple offset design can be used for on/off services, throttling services and modulating services.

On/Off Service
Like the name suggests, on/off valves are designed to shutoff and to open fully but lack the ability to to regulate effectively through the range of travel.

Throttling Service
Throttling service (sometimes referred to as inching) is in general flow control through the system where the valve is set and held in an intermediate position.

Modulating Service
Modulating service (known also as regulating service) is used to drive the valve frequently to any position between fully open and fully closed to control the flow. It uses feedback from the field, and valve disc position is adjusted almost continuously.

Quarter turn valves are usually limited to a throttling range of ~25° to ~75° open (25% to 85%). In case of throttling the manufacturer should be consulted in order to predict whether the control valve was installed accurately.

For more information, contact Mountain States Engineering and Controls. Visit their web site at https://mnteng.com or call 303-232-4100

Monday, May 22, 2017

Introduction to Valve Parts or Components

cutaway view forged steel gate valve
Cutaway view of a forged steel gate valve
Courtesy Crane-ChemPharmaEnergy
Although there are many different classifications of valves specific to their respective functions, there are standard parts or components of valves you may find regardless of the classification. They are the valve body, bonnet, trim, seat, stem, actuator, and packing.

The Valve Body is the primary boundary of a pressure valve which serves as the framework for the entire valve’s assembly. The body resists fluid pressure loads from connected inlet and outlet piping; the piping is connected through threaded, bolted, or welded joints.

The Valve Bonnet is the opening of the Valve Body’s cover. Bonnets can vary in design and model, is built using the same material as the Valve Body, and is also connected to the entire assembly through threaded, bolted, or welded joints.

The Valve Trim collectively refers to all the replaceable parts in a valve, e.g. the disk, seat, stem, and sleeves––all which guide the stem as well.

The Valve Disk allows the passage or stoppage of flow. Disks provide reliable wear properties and differ in what they look like per valve type. For example, in the case of a ball valve, the disk is called a ball, whereas for a plug valve it is a plug.

The Valve Seat(s) or it’s seal rings provide surface seating for the disk. For example, a globe valve requires only one seat and this seat forms a seal with the disk to stop flow.

The Valve Stem provides the proper position which will allow the opening and closing movement of the Valve Disk. Therefore, it is connected to the Valve Disk on one end and the Valve Hand Wheel or the Valve Actuator on the other.

The Valve Yoke is the final piece in the valve’s assembly; the Yoke connects the Valve Bonnet with the actuating mechanism. The Valve Stem passes through the top of the Yoke which holds the Yoke or stem nut.

There are countless variants of valve designs, sizes, and configurations. These basic parts will be found on most, but the particular form and arrangement of the part may provide an advantage when employed for a particular application. Share your industrial process valve requirements and challenges with a valve specialist. Combine your own process knowledge and experience with their product application expertise to develop an effective solution.

Wednesday, December 9, 2015

A Close Look at Butterfly Valve Seat

Butterfly valve soft seat cutaway view
Cutaway View of Butterfly Valve With Soft Seat
Courtesy Flowseal - Crane CPE
Butterfly valves are found throughout the fluid based applications in the process control field. They are one of many common and special types of industrial valves used to regulate fluid flow in ways that are compatible with the media being controlled and the degree of precision needed to produce the desired process outcome.

The industrial process control field benefits from a large array of valve manufacturers in pursuit of the favor and business of process operators. Operators continually seek better performance and lower life cycle costs. Manufacturers respond with increasingly improved designs.

A butterfly valve has a disc that is positioned in the fluid flow path. It rotates around a central axis, the stem, through a 90 degree arc from a position parallel to the flow direction (open) to perpendicular (closed). A critical element of a butterfly valve is the seat, where the disc seals to the body in the closed position. Seat design should provide these positive operating attributes:
  • Low friction to reduce valve operating torque
  • Resistance to wear
  • Arrangement that provides for easy replacement
  • Seal or shutoff tightness appropriate for the application
Flowseal, part of the Crane, CPE group of brands, utilizes their specially designed Soft Seat valve sealing arrangement on their resilient sealed butterfly valves. The Soft Seat feature provides beneficial fulfillment of process requirements for the attributes listed above. The valve is available in a range of sizes, with options and variants to meet a wide array of industrial process requirements.

Learn more about the Flowseal Soft Seat butterfly valves by watching the short video below. You can delve deeper with a browsing of the illustrative brochure that is also included below. It provides some detailed illustrations of how the seat functions under differing operating conditions. Contact a product specialist and share your process challenges. Your process knowledge and their product application expertise, when combined, will produce a useful solution.


Tuesday, July 14, 2015

Is a Butterfly Valve Right for Your Application?

There are many manufacturers of industrial control valves, with each producing an array of sizes, types, construction materials, and other distinguishing characteristics that make it necessary to quickly narrow the field of contenders to consider for your valve application in order to be productive. A useful filter that can be applied to the broad offering of valves is selecting a valve “type”. Valve types are generally classified according to their means of closure, with some common types being ball, plug, globe, butterfly and gate, among others. Each type has particular application strengths, some that may prove advantageous enough for your application to exclude all others. Let’s take a look at butterfly valves.
industrial butterfly valve
Butterfly Valve
Courtesy Crane CPE

The closure means for a simple butterfly valve is a disc, positioned in the fluid flow path, that rotates around a central axis through a 90 degree arc. The valve stem serves as the axis and extends through a seal to the exterior of the valve body where it serves as an actuation point. The closed position for the valve has the disc positioned perpendicular to the direction of flow and blocking the flow path. When open, the disc is parallel to the flow path, but still positioned in the center of the flow. Butterfly valves are available in a variety of construction materials, making them suitable for an array of media.

Butterfly valve aspects that might be advantageous:
industrial butterfly valve
Butterfly Valve
Courtesy Crane CPE

  • Closure mechanism allows for comparatively low torque operation.
  • Small size and weight for reduced installation space and valve body support.
  • Low pressure drop in the fully open position. The disc, when parallel to the flow path, presents a thin edge of its profile to the fluid flow.
  • Low maintenance requirements and small parts count.
  • Transition from fully open to fully closed with a 90 degree turn provides for fast operation.
  • Suitable for limited range of throttling applications.

Aspects warranting closer scrutiny:

  • Throttling capability is generally limited to low pressure drop applications.
  • The orientation of the closure may cause cavitation under some conditions.
  • Choked flow can be a concern under certain conditions.

Performance, low maintenance requirements, and cost are always primary considerations. There are many more detailed sources of application information. Consult with a professional sales engineer that specializes in industrial process valves and get the information you need to make a good choice.

Friday, May 29, 2015

Industrial Valve Body Style and Flow Path: A Visual Illustration

fluid dynamics image
(Image courtesy of Wikipedia)
There are many types of valves body styles, each with their own unique flow characteristic and pattern. Valve design generally dictates optimum application service for any given use. For instance, globe or diaphragm valves provide excellent flow control because of a very linear flow characteristic and are used widely as flow control valves. Conversely, standard ball or butterfly valves are not good control valves because of their very non-linear flow characteristic, and special modifications need to be made to their discs or balls to improve linearity.

The following video illustrates the design and flow pattern for (4) types of valve:

Tuesday, December 23, 2014

High Performance Butterfly Valve Exploded View

Here is a short video that quickly displays the components of a high performance butterfly valve. High performance butterfly valves are used in the oil and gas, commercial HVAC, chemical processing, mining, pharmaceutical, water & wastewater industries. High performance butterfly valves come in wafer and lug bodies, have bodies made of carbon steel, stainless steel, or other alloys, and work under higher pressures and temperatures than "rubber lined" butterfly valves.

Thursday, October 9, 2014

High Performance Butterfly Valves for On/Off and Throttling Service

High Performance Butterfly Valves (HPBF) are a standard in many industries including heating, ventilating and air conditioning, power generation, hydrocarbon processing, water and waste water treatment. The key features of HPBV are high performance shutoff and modulating service for standard industrial process lines, materials of construction options include carbon and stainless
steel,  sizes up to 48”, both wafer and lugged body styles available, in pressures classes 150 – 600.

Here is a short video introducing the Flowseal high performance butterfly valve.


Tuesday, July 8, 2014

Resilient Seated and High Performance Butterfly Valves

Lug Body Resilient
Seated Butterfly Valve
(Crane Centerline)

A butterfly valve uses a round, thin disk to control flow through a pipe. The disk is connected to the stem via a shaft completely through the disk, or at the top and bottom of the valve. 

The butterfly disk is continuously in the flow path, but because of its thin profile, has minimal impact on flow. Butterfly valves are popular because they offer very tight shut-off, are available in a wide range of materials and sizes, and can be automated inexpensively with many types of quarter-turn electric and pneumatic actuators.

Butterfly valves are used in many industrial applications today, from controlling the flow of water to handling much more severe industrial fluids. Butterfly valves are extensively used in water treatment, chemical processing, pulp and paper making, food processing, power generation and many other industries.