Using the wrong valve in a natural gas system can lead to catastrophic consequences such as leaks, fires, or even explosions. Ball valves are an excellent, cost-effective option for natural gas service as they offer leak-tight seals, quarter-turn operation and can be found with both flanged and threaded connections.
Key factors to evaluate when selecting a ball valve for natural gas:
- Pressure requirements
- Flow rates
- Valve and component materials
- Codes and safety standard requirements
Pressure requirements
Natural gas lines operate at a wide range of pressures, from 1,500 psi for large transmission lines down to ¼ psi for low-pressure residential service.
In commercial buildings and boilers, pressures are typically much lower and often under 5 psi, making ASME Class 150 valves a common choice. Choosing a valve that is rated for your intended line pressure is a critical first step.
The American Society of Mechanical Engineers (ASME) code section B16.34 specifies the pressure/temperature classes valves can be made to and lists the operating pressure at specific temperatures. Common classes include 150, 300, and 600, while higher pressure classes like 900, 1,500, and 2,500 also exist. This chart should be consulted to ensure you choose a valve that meets the pressure and temperature requirements of your intended service.
Flow rate requirements
Once you have determined the pressure and temperature requirements of your valve, you should ensure it also meets your flow rate demands.
Several factors determine the flow rate in a natural gas system, including:
- Pipe diameter
- Line pressure
- Gas velocity
- Pressure drop
Ball valves typically list a “Cv” (flow coefficient) for each size. This is a factor that can be used along with pressure drop and viscosity of the fluid to calculate the flow rate expected for the valve when used in your system.
Valve material requirements
The body and seat materials your valve is constructed from are another important factor to consider. For natural gas lines, the most common valve body materials used are:
- Brass
- Cast iron
- Stainless steel
The specific material needed for your application will depend on the operating pressure of your line and the corrosion resistance required.
Don’t overlook stem seals since a leaking stem can be just as dangerous as a leaking seat. For natural gas service, stem seals are often made from PTFE or other high-performance polymers to ensure tight sealing and chemical resistance.
Seat material is also a critical factor and is highly dependent on your specific application. Some natural gas lines require a metal seat made from stainless steel, tool steel, or a variety of other metals. Soft seats are typically made from PTFE due to its high corrosion resistance and nonstick properties.
Codes and requirements
Finally, when choosing the correct valve, you should be aware of any local or national codes and safety requirements. The most common requirements for valves used in flammable gas services are the American Petroleum Institute (API) standard 607 and the Canadian Standards Association (CSA) standard 3.16.
API 607 is a fire safety standard specifically for quarter-turn ball valves that lists test requirements that must be met in order to obtain this certification, and CSA 3.16 is a broader standard that covers a variety of valves used in flammable gas service and is often a requirement for valves used in Canada. When searching for the right ball valve, it is important to understand all applicable code requirements that your application might have.
When does a class 150 ball valve make sense?
A class 150 ball valve is a good fit for natural gas service under the right conditions. It can be suitable in low-pressure applications such as commercial heating systems or small boilers, provided it meets all relevant safety standards and material requirements.
However, for high-pressure transmission lines or severe service conditions, a higher-class valve or specialized design is essential. The key is matching the valve’s pressure rating, materials, and certifications to the specific application.
Making the right valve choice for natural gas
Selecting the right ball valve for natural gas service requires careful attention to safety and performance. By matching pressure ratings, materials, seals, and certifications to your specific use case, you can ensure reliable operation and peace of mind. When in doubt, consult industry standards and verify every detail before making your choice.
FAQ
What pressure rating do I need for a natural gas ball valve?
Natural gas systems operate across a wide pressure range, from high pressure transmission lines to very low pressure commercial or residential service.
For most commercial buildings and boiler systems operating under about 5 psi, an ASME Class 150 ball valve is commonly used. Always verify your system pressure and check the ASME B16.34 pressure/temperature chart to ensure the valve class matches your operating conditions.
What materials are best for ball valves used in natural gas service?
Common valve body materials include brass, cast iron, and stainless steel, with the right choice depending on pressure and corrosion resistance needs. Stem seals are typically made from PTFE or other high-performance polymers because they offer reliable sealing and chemical resistance.
Seat materials vary by application: PTFE soft seats are widely used for standard conditions, while metal seats are selected for high temperatures, abrasive flow, or severe service environments.
Read more about ball valve material optimization here.
Which codes or certifications should a natural gas ball valve meet?
Two major standards apply to valves used in flammable gas service:
- API 607 – firesafe testing requirements for quarter turn valves safe testing requirements for quarter turn valves
- CSA 3.16 – requirements for valves used in natural gas and other flammable gases, commonly required in Canada
It’s important to confirm that any valve you choose meets all relevant local, national, and industry code requirements for your application.