Showing posts with label severe service. Show all posts
Showing posts with label severe service. Show all posts

Wednesday, September 7, 2016

Severe Service Valves - Application Targeted

severe service flanged plug valve lined Fluoroseal
Sever Service Plug Valve
Fluoroseal
Industrial process control applications can be associated with some very stringent and challenging performance requirements for the physical equipment and components that are part of the process chain. In fluid based operations, the control and shutoff valves can be a significant impact point of extreme fluid conditions, requiring careful design and selection consideration to assure proper performance and safety levels are predictably maintained.

Industrial valves that are intended for application at the extremes are generally referred to as severe service valves. While there are plenty of published and accepted standards for industrial valves, one does not exist to precisely define a severe service valve. There is, however, some movement toward the development of severe service standards in some industry segments.

So, how do you know when to focus valve selection activities on severe service valves, as opposed to general purpose valves? There are a number of basic criteria that might point you in that direction:
  • Very extreme media or environmental temperature
  • High pressure drop operation that may cause cavitation
  • Rapid and extreme changes to inlet pressure
  • Certain types or amounts of solids contained in the fluid
  • High number of mechanical operations
  • Thermal cycling
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 in evidence that might overrun 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 a severe service condition is identified, a careful analysis of the possible operating conditions will reveal the performance requirements for the valve.

There are numerous manufacturers of severe service valves, each seeming to concentrate on a particular niche. Fluoroseal, a globally recognized manufacturer of lined valves for corrosive applications, has their own entry in the severe service arena that is based upon one of their popular general purpose valves. The focus for the FE Series valve design appears to be thermal cycling, excessive number of mechanical operations, and fugitive emissions.

I have included a technical bulletin that describes and nicely illustrates (with a cutaway view) the various features incorporated in the valve design.

You can always get more information, or discuss your special requirements, with a product application specialist. They have access to technical resources that can help with selecting the right valve configuration to meet your severe service applications.

Tuesday, August 30, 2016

Applications For Metal Seated Ball Valve

metal seated ball valve with handle and flange connections
Metal Seated Ball Valve
Crane - Krombach
Fluid process control employs valves of various types to start, stop, throttle, or divert flow of a fluid. Ball valves are a common selection for process application when their inherent advantages provide the greatest benefit.
  • Leak-proof service
  • Well suited for processes requiring only full flow or no flow operation.
  • Rapid open and close action, requiring only 90 degrees of rotation from fully open to fully closed.
  • Comparatively light weight and compact size.
  • Wide range of construction material options for body, ball, and seals make them suitable for many applications.
  • Require only moderate force to control valve position.
  • Flow path opening in the ball will often be “full port”, providing same cross section as the connected pipe and adding very little restriction or pressure drop to the flow.
  • Low maintenance, with no lubrication required.
There are numerous ball valve variants that provide modified features and performance, but let's focus on what is generally considered severe service applications.

Severe service, while not currently defined by an international standard, generally can be characterized by one or more operating conditions that put great levels of stress or wear on valves.
  • Very extreme media or environmental temperature
  • High pressure drop operation that may cause cavitation
  • Rapid and extreme changes to inlet pressure
  • Certain types or amounts of solids contained in the fluid
  • Corrosive media
Some of these conditions will greatly impact the valve seat. Many valves are provided with thermoplastic seats that, while providing suitable performance throughout a wide range of media conditions, will deteriorate quickly under conditions prevailing in severe service. An alternative to the soft thermoplastic seats is a metal seat design. 
  • Greater temperature tolerance
  • Self cleaning seat
  • Improved resistance to effects of particulate laden media or slurries
  • Corrosion resistance, enhanced by special coatings applied to metal construction
The document below provides an in depth view of a metal seated ball valve. Operating conditions, specifications, and illustrations (including my favorite, the cutaway view) are provided. Share your fluid control requirements with product and application specialists, combining your process expertise with their product application knowledge to develop effective solutions.


Wednesday, March 9, 2016

Sleeved Plug Valves - Design Features and Variants

Industrial process control often involves the management of fluid flow, either by simple on-off flow control, throttling, or diversion of flow to alternate destinations. Valves of many differing designs and construction features provide distinct advantages for particular applications depending upon a variety of media characteristics, operational requirements, physical restrictions, and regulatory requirements.

Plug valves, so named for the generally tapered or parallel sided structure held in the flow path by the valve body, have wide application throughout the fluid control field. Their advantageous features include simple design, low maintenance, moderate size, minimal flow resistance when fully open, and quarter turn operation.
Cutaway view sleeved plug valve for industrial process use
Cutaway view of sleeved plug valve with design features labelled
Courtesy Fluoroseal

One subset of the plug valve family, the sleeved plug valve, has an additional advantage. It does not require lubrication. The metal plug is wedged within a sleeve, usually PTFE or a similar material, which provides a seal around the plug and a self lubricating surface to facilitate rotation of the plug within the body. One manufacturer, FluoroSeal, provides a broad offering of sleeved plug valves. The illustration (left) provides a cutaway view of one of Fluoroseal's valves of this type with primary design features labelled by the manufacturer as follows:
  1. Bidirectional in-line bubble-tight seal independent of line pressure
  2. Multiple external bubble-tight seals independent of line pressure
  3. Direction mechanical three-point adjustment independent of line pressure
  4. Independent travel stops
  5. Full encapsulation and retention of all leading edges of PFE sleeve and top seal components
  6. Full lip at port openings protects PTFE sleeve
  7. Contoured waterway ensures minimum flow turbulence characteristic
  8. No body cavities to entrap flow media
  9. Positive flow direction indication
  10. Drilled and tapped flange actuation mounting pads independent of cover and top sear assembly.

This versatile valve type is available in a number of variants suited to particular applications. Thes variants include:

  • Multiport configurations for flow diversion.
  • Caged plug version for use with a range of abrasive fluids
  • Double block and bleed design
  • Fire safe versions with additional sealing and venting to prevent leakage if the valve is overheated in a fire
  • Severe service variant to provide tight emission control and suitability for demanding applications with thermal cycling or a high operating rate
  • Special cleaning, testing, production methods, or other specialized tasks needed to assure safety or performance under very specific application conditions found in various industries.
An illustrated document with technical performance data for much of what is described above is included below. Browse the document for a more complete understanding of where sleeved plug valves can be applied and how they work. For more information, contact a valve specialist. Share your fluid control challenges with them and work toward a winning solution. The combination of your process expertise and their deep product application knowledge will yield good results.