VALVE SIZING EXPLAINED: KEEPING THINGS FLOWING
While valves might be a small part of your piping process or system in terms of space, they’re often a substantial portion of the design and build budget. They also have a significant impact on long-term costs and overall system performance.
Choosing a proper valve size is essential to both optimizing costs and ensuring safe, accurate, and reliable operation.
The first thing to consider is the overall size of the valve — both in terms of physical dimensions and in terms of internal size and flow rates (CV).
Choosing a valve that does not fit properly in the space required could result in added costs. Choosing a valve which does not provide the ideal flow rate can lead to inaccurate flow control at the least and complete system failure at worst.
For example, if your valve is too small, it could cause reduced flow downstream while creating back-pressure upstream. If the valve is too large, you’ll find that flow control is drastically reduced the further you move from fully open or fully closed.
When choosing the proper size, be sure to consider both the connector diameter and the overall flow rate of the valve compared to your needs. Some valves offer excellent flow while others constrict flow and increase pressure.
This means sometimes you must install a larger valve to adjust for flow than the adapter diameter alone might imply.
Common Valve End Types. Source: Unified Alloys
While the most obvious implication here is choosing an end connection compatible with your piping, there are also functional characteristics to common end types that might make one valve more suited to your needs than another.
Common valve connections and ends include:
Screwed or Threaded: Often used in instrument connections or sample points
Flanged: The most common ends for piping use
Butt Welded: Typically used in high-pressure or high-temperature operations
Socket Welded: Commonly used on small bore piping where threaded connections are not permitted
Wafer and Lug: Often used for compact valves installed in systems with limited space
VALVE MATERIALS: ENSURING SAFETY AND LONG-LASTING PERFORMANCE
Depending on your intended use, the materials with which your valves are made might be a critical aspect in ensuring safe operation and reducing maintenance and replacement costs over the life of your operation.
Stainless steel valves are excellent options in a range of processing environments, including those involving corrosive media (such as chemicals, saltwater, and acids), environments with strict sanitation standards (such as food and beverage manufacturing and pharmaceuticals), and processes involving high pressure or high temperatures.
However, if you are processing solvents, fuels, or volatile organic compounds (VOCs), choosing a valve material from a non-sparking material — such as brass, bronze, copper, or even plastic — is often a better option. In addition to selecting the correct body material, internal (wetted) trim parts should be evaluated for chemical compatibility as well. If your valve contains elastomers, they should also be evaluated for their chemical compatibility as well as pressure and temperature limitations.
VALVE STANDARDS: MEETING COMPLIANCE AND REGULATORY CONCERNS
Depending on your intended usage, you might find that valves must adhere to particular standards to meet regulatory requirements for safety, sanitation, or other concerns.
While there are too many standard organizations and potential regulations to cover in detail, common general standard organizations include:
CSA Group (CSA)
The American Society of Mechanical Engineers (ASME)
The American National Standards Institute (ANSI)
The American Society for Testing Materials International (ASTM International)
The Manufacturers Standardization Society (MSS)
The International Organization for Standardization (ISO)
The Public Health and Safety Organization (NSF)
NACE International (NACE)
The American Petroleum Institute (API)
American Water Works Association (AWWA)
There are also industry-specific standards to consider.
Major standards organizations by industry include:
ASHRAE Valve Standards
ASME BPVC Valve Standards
ASSE Valve Standards
ISA Valve Standards
NFPA Valve Standards
SAE Valve Standards
Ref.
https://www.unifiedalloys.com
https://hardhatengineer.com