Are you aware of what your valve’s seal material is made of? Does the type of sealing material affect the performance of your process valves?

Seals are integral in fluid control - they prevent media leakages from valves, contributing to the overall reliability of fluid flow systems and maintaining predictable process efficiency. Seals do not only prevent leakages; they absorb some of the mechanical and chemical stresses from the service fluids. This means the quality of any industrial valve relates directly to its sealing capabilities and the reliability of seal materials over time.

Low-pressure gas applications present multiple operational challenges, which can complicate the design of process valves and their seals. Gases are compressible and experience volumetric changes as process temperature and pressure change. Volume changes mean gas leakage at low pressure may result in significant gas density variations, making it difficult to maintain consistent flow rates and desirable process efficiency. The low density of process gases implies the medium may not provide sufficient force to seal the valve. Low gas density and the low viscosity of gases make the valve an ideal location for fugitive emissions and unprecedented leakages.

 

1” Low Pressure Gas Valve

 

Seals for low-pressure gas applications must have robust designs to guarantee optimum safety and reliable sealing efficiency within the process operating temperature and pressure range. Nitrile Butadiene Rubber (NBR) is one of the reliable seal materials that overcome challenges associated with low-pressure gas applications. This article explores its strengths and relevance in automated applications using solenoid valves.

Understanding NBR seals

Nitrile Butadiene Rubber is a polymer composed of acrylonitrile (ACN) and butadiene. It is a versatile synthetic rubber with superior physical and chemical resistance properties, making it a reliable sealing material in various fluid applications.

Altering the composition of ACN and butadiene gives different properties to synthetic rubber. ACN gives NBR polymer the desirable resistance against media abrasion, and butadiene enhances polymer flexibility (deformation and elasticity) at different process temperatures. NBR rubber and seals are not limited to industrial fluid applications only. The seals are available as gaskets and O-rings and are vital for automotive and aerospace applications involving grease and mineral oils.

Properties of NBR Seals

Why are NBR seals preferable for frequently cycled low-pressure solenoid gas valves? The answer lies in their unique properties.

• NBR seals have dependable wear and abrasion resistance properties. It is an essential physical property since low-pressure solenoid gas valves undergo frequent actuation in response to gas flow requirements. The frequent cycling exposes the valves to extensive mechanical stresses, which can lower the durability of process valves. The impact of media abrasion on valve seals is more evident in gas applications where impurities can ingress fluid flow pathways. NBR seals provide a means to combat the abrasive nature of fluid media. NBR seal resistance to wear guarantees reliable gas leakage prevention over time.
• NBR seals can provide adequate resistance against damage by hydrocarbons, oils and fuels. The seals are compatible with the chemical properties of these fluid media, which contain substantial amounts of hydrocarbons. The resistance to fuels and oil gives NBR the versatility required for use across multiple industrial applications. The seals can resist swelling and softening, which is predominant with prolonged exposure of seals to hydrocarbon fluid media.
• NBR seals can easily deform when exposed to fluid pressure and regain their original shapes upon withdrawing the service fluid pressure. The elasticity of NBR seals means they can create leak-tight seals across different applications. They can conform to irregularly shaped valve surfaces, compensating for any valve seat manufacturing imperfections.
• NBR seals have a wide operating temperature range. It makes them ideal for low-pressure gas applications where process temperature can drop to -40oC and increase to a high of over 120 oC. These seals can offer dependable sealing across the designed operating temperature range as they expand and contract per the prevailing process temperature.

Real World Applications

Consider a commercial natural gas distribution pipeline to customers in a town. What challenges does a natural gas distribution company face in such a setting, and how can low-pressure gas solenoid valves with NBR seals help them meet customer demands? The gas distribution pipeline operates at low pressure, usually within 0.3-1 bar. The company must ensure the gas consistently reaches all customer terminals while preventing leakages, which may pose serious safety issues. The company will also be focusing on keeping operational costs within manageable levels.

• NBR-sealed solenoid valves provide an effective means to combat natural gas distribution challenges across a large area. These valves will offer a simple way to automate natural gas distributions to customer terminals while offering leak-tight fluid service. Employing NBR seals can prevent minor gas leaks. The gas leaks may seem insignificant but can lead to cumulative losses, increasing distribution costs.
• Natural gas is a hydrocarbon and can rapidly degrade valve materials. Recurring seal and valve material degradation lowers valve longevity, causing inconsistencies in gas distribution pressure. NBR seals can effectively resist hydrocarbon media corrosion, further lowering the frequency of valve downtime and associated operating costs.
• Handling gas distribution to a wide coverage area is prone to flow instabilities and inconsistencies due to valve performance challenges. Using low-pressure solenoid valves with NBR seals ensures precision and stable low-pressure gas distribution without the usual gimmicks of delayed valve responsiveness. The distribution company enjoys a reliable gas supply at affordable rates.
• NBR seals for municipal gas distribution systems are cheaper than high-performance seal alternatives. These seals are more affordable than their counterparts like FKM, considering the company deals with hundreds or thousands of valves at distribution and customer terminals.

The NBR Seal Advantage in Low-Pressure Solenoid Valves

Low-pressure solenoid valves in our Electric Solenoid Valves catalog have NBR seals. These are high-quality valves for your low-pressure gas system automation at an affordable rate. The NBR seal advantage in our low-pressure solenoid valves means you can enjoy unlimited versatility and manage gas flow for domestic or industrial applications. Here are some crucial benefits one can enjoy with NBR-sealed low-pressure solenoid valves.

• Mechanical performance - NBR seals have remarkable mechanical properties necessary for maximizing valve leak prevention performance. They can withstand repetitive mechanical stresses, abrasion and frictional wear from service media, including hydrocarbons. They have low permeability to gaseous media and can prevent leakages from solenoid valve ports and bodies. NBR is also flexible (elastic) and provides dependable sealing even at low system pressure.
• Durability - enhanced resistance to wear and tear gives the sealing material an extended lifetime. The sealing medium can withstand regular and rapid valve actuation cycles. They are ideal for frequently cycled valves, even in harsh operating environments.
• Chemical compatibility - NBR seals do not react with service media. They possess dependable resistance to chemical corrosion. They can handle the flow of hydrocarbons (including methane, propane, butane, natural gas), inert gases and compressed air. Low-pressure solenoid valves with NBR seals are also effective for servicing mixed and processed gases in multiple low-pressure industrial applications. They can convey these gases without degradation while offering adequate defenses against leakages and fugitive emissions.
• See our chemical compatibility tool for more information

Alternatives for NBR Seals in Low-Pressure Solenoid Valves

While NBR seals are effective for low-pressure gas applications, they have a few limitations that impede their usability beyond the intended application areas. They have limited resistance to gaseous media with acidic content. Strong acids can accelerate their degradation. These valves are also susceptible to Ozone and UV radiation degradation and cannot be effective in environments with these elements.

NBR seals are ineffective at extreme temperature ranges. They cannot provide adequate sealing against gas leakage in cryogenic gas applications. They are also ineffective at high process temperatures (above 120oC). Extreme heat and cold applications will require alternative sealing materials for solenoid valves.

Some alternative sealing materials to NBR in solenoid valves include FKM and PTFE. FKM is a fluorocarbon material with superior temperature resistance. It can withstand process temperatures beyond 200oC. It also has better chemical resistance than NBR. It can provide adequate seals even in high Ozone and UV radiation environments. While FKM can be a reliable sealing material for industrial low-pressure solenoid valves, it is costlier than NBR. It increases the cost of valve ownership and maintenance.

Polytetrafluoroethylene (PTFE) is another alternative to NBR seals. It also has remarkable temperature endurance and chemical resistance properties and can be used for solenoid valves for acidic gaseous media. However, PTFE lacks the flexibility to provide leak-tight sealing in extremely low-pressure gas applications.

Click here for more information on different valve seal materials.

Conclusion

NBR seals are an ideal solution for leak prevention in low-pressure domestic and industrial gas applications. They provide a balance between affordability, reliable and predictable performance, and durability. The correct sealing material for low-pressure gas applications is essential for maintaining system reliability and enhancing the high safety standards in gas-related applications. Understanding the challenges associated with low-pressure gas applications is necessary when designing and sizing solenoid valves and their seals. Ensure the NBR seals can withstand the system temperatures for a more predictable valve performance.

Consult our valve specialists at Electric Solenoid Valves when choosing low-pressure gas solenoid valves for more specialized applications. It will ensure you get tailor-made valve solutions that are affordable, reliable, and long-lasting.