Specifics Of Low-Pressure Gas Valves

Sizing valves and piping systems for gas service presents unique challenges to piping professionals. Gas service deals with various gases like nitrogen, hydrogen, compressed air, oxygen, etc. These gases, unlike liquids, are highly compressible. They expand to fill available spaces and escape through the tiniest openings. The design and selection of valves for industrial gas service consider the unique nature of the service fluids. This is to ensure they provide desirable flow characteristics at different pressure ratings while optimizing the safety of processes.

Gasses exhibit specific chemical and physical characteristics at different operating pressure and temperature. It is essential to limit the leakage of gases around valves and other sections of the piping system. These gases can be flammable, corrosive, or undergo chemical reactions when in contact with other materials. Valves for industrial gas services must provide adequate defenses against leakages and fugitive emissions to guarantee optimal performance and reliability of gas pipelines.

Low pressure gas valves are popular across industries for industrial applications handling gases at low pressure. These valves are essential for:

• Commercial laboratories
• Residential gas systems
• Low pressure industrial processes
• HVAC systems

How do different categories of low-pressure gas valves work, and how do their performances compare? This article explores the working principles of low-pressure gas valves and critical sizing and selection factors.

Types Of Low-Pressure Gas Valves

One can choose from a wide range of gas valves depending on the desired flow control, function and design of the pipeline and the level of automation. Here is a look at the different low pressure gas valves, their performance characteristics and practical use cases.

Ball Valves

Ball valves are popular in natural gas and compressed air pipelines. These valves rely on a spherical disc to regulate and control the flow of gases. Ball valves are quarter-turn control devices that move from a fully opened to a fully closed position and vice versa by rotating the disc through 90 degrees. Ball valves provide tight shut-off and have low pressure drops across them.

Gate Valves

Gate valves for low pressure gas systems are suitable for on/off fluid service. They are linear motion valves that regulate fluid flow by manipulating the up and down movements of the disc (gate). Gate valves provide maximum flow capacity when fully opened. The gate valve diameter matches the internal diameter of the adjacent pipes, thus exerting minimal pressure drops. It is beneficial for low pressure gas systems where optimal flow capacities are required. Gate valves offer tight shut-offs and can provide bi-directional fluid control. It makes them preferable for gas systems requiring periodic flow reversal. These valves are unsuitable for throttling as they can damage their seats and flow control mechanisms. Gate valves are common in low pressure natural gas distribution systems. Such systems use resilient seated gate valves to guarantee tight shut-off and limit leakages.

Butterfly Valves

Butterfly valves are fast-acting quarter-turn flow control devices with significant importance in low pressure gas systems. These valves permit gases to flow when the disc lies parallel to the direction of fluid flow. A 90-degree turn causes the disc to lie perpendicular to the direction of flowing gas, thereby restricting fluid flow. The existence of the flow control mechanism in the path of fluid flow means the valve causes slight pressure drops in the system. Butterfly valves are popular in industrial pneumatic systems.

Solenoid Valves

Solenoid valves are vital for automated low pressure gas applications. They provide quick on/off shut off and throttling of service media. Solenoid valves have various advantages over traditional gas control valves. Some benefits of solenoid valves include:

• Quick operation - the operation of a solenoid valve relies on control signals to energize or de-energize an electromagnetic solenoid. This generates a corresponding mechanical force that opens or closes the valve for desirable flow control. Their quick operation means these valves can respond fast to changes in control signals and adjust valve positions to achieve proper gas regulation.
• Remote operation - solenoid valves are automatic flow control devices. These valves can be operated remotely, maximizing the safety of low-pressure gas systems. Remote operations depend on control signals in the form of electrical pulses, increasing the responsiveness and precision of the valves.
• Improved safety - solenoid valves have various inbuilt safety control mechanisms. The valves can shut off pipelines in emergencies, restricting further gas flow that may result in leakages or fugitive emissions.
• Compact, energy-efficient designs - solenoid valves are small and can fit into locations with limited spaces. Their operation depends on the control signals, implying they consume energy only when opening or closing. This reduces energy consumption across the facility.
• Reliability and durability - the design of solenoid valves guarantees long-term and reliable gas service. These valves withstand continuous cycling without losing their reliability (flow rates), leak tightness and responsiveness to control signals. The valves have adequate resistance to vibration, corrosion by service media and corrosive elements in operating environments and mechanical stress caused by valve cycling requirements.

Low pressure solenoid gas valve

Electric Solenoid Valves has an expansive catalog of low pressure solenoid gas valves. These valves are engineered using the best materials to meet the performance requirements of different industries. They are available in multiple sizes for compatibility with various pipelines. Some unique characteristics of our valves are:

• Valve bodies are manufactured using sturdy, durable materials like stainless steel and brass.
• They utilize nitrile butadiene rubber (NBR) seals which withstands low temperatures associated with low-pressure gas systems. NBR can withstand a wide temperature range without losing their sealing efficiencies, ensuring leak-tight gas service throughout their useful lives.
• Compatibility with a wide range of industrial gasses

Choosing the Right Low Pressure Gas Valve

Choosing the right size and type of valve is essential for maximizing the safety of industrial and domestic gas systems. What are some crucial factors one should evaluate when sizing or selecting valves for low pressure gas conveyance systems?

Flow capacity

The first thing to consider is the quantity of gas required in the piping system. The valve should be capable of handling varying flow rates, depending on system requirements. Inadequate valve flow rates result in undesirable bottlenecks and system inefficiencies. These inefficiencies affect the reliability of gas systems.

Valves should exert minimal pressure drops on the low-pressure gas. Some valves can exert excessive pressure drops on the service fluids, causing reduced flow rates to downstream equipment and systems. Valves with adequate flow rates reduce pressure drops across them and can stabilize gas flow through the piping system for uninterruptible gas regulation and control.

Valves can undergo premature damage due to gas flow velocity issues and choked flow. Low pressure gas valves should have adequate flow capacities to mitigate the negative impacts of inconsistent flow rates like vibration and noise that damages piping equipment. Other effects of inadequate flow rates are cavitation and choked flow, which limit downstream flow capacities and accelerate valve deterioration.

Ensure low pressure gas valves selected for various industrial systems can meet the maximum flow rates of the piping systems. Do not oversize or undersize gas valves to avoid any performance issues.

Material compatibility

Gasses exhibit multiple chemical characteristics such as process temperature and pressure change. These chemical variations increase gas reactivity and corrosiveness and can cause undesirable damage to valves, pipes, fittings, and other equipment. The type of low-pressure valve chosen for a specific gas application should utilize materials compatible with the service media. That is, the valve materials must provide adequate chemical resistance to minimize damage due to corrosion.

Aside from meeting the chemicalcompatibility of the service medium, low pressure gas valves should possess sufficient mechanical strength and temperature resistance. The temperature of low-pressure gas can drop below 0 degrees centigrade. The subzero temperatures can distort the mechanical properties of valve materials. The temperature changes cause expansion and contraction, leading to surface deformations and cracks which reduce valve body efficiency and durability. Some sealing materials deform when the process temperature drops below certain levels. When this happens, leakages emerge around the valve, posing various safety risks in facilities.

Another aspect of material compatibility is the connection of low-pressure valves to existing piping equipment. Is the low-pressure valve connected through threaded ends, or is it flanged? Does it require additional gaskets for leak protection? Valve materials should also have chemical compatibility with adjacent equipment and pipes to prevent galvanic corrosion.

Valve safety features

Various risks exist when dealing with low pressure gas service. Valves should provide adequate defenses to prevent accidents or incidents exacerbating workplace and environmental safety. When choosing valves for low pressure gas systems, evaluate:

• Leak prevention mechanisms of the valve - what types of seals does the valve use, and do they provide reliable, leak-tight sealing? Valve construction and sealing materials must complement leak-free gas service and offer tight shut-off capabilities.
• Pressure ratings of the valve- the valve should accommodate the pressure range of the piping system without failure. Check if the valve has additional safety mechanisms, like a pressure limit switch, to protect against overpressure.
• Fail-safe features and emergency shut-off - does the valve contain advanced safety features to restrict gas flow in an emergency? The valves should also shut off faster during emergencies.

Actuation and complexity of the piping system

How will the valves be operated? Some low-pressure gas systems require manual operations and can benefit from manual ball valves, while others demand precise control and automation. The latter benefits from automated low pressure solenoid valves. Automated valves are favorable for frequently cycled systems, while manually operated valves are essential for low-cycle systems.

One should evaluate the complexity of the low-pressure piping system when choosing control valves. Some systems convey multiple gases at varying pressure levels. Others have intricate piping networks with various control points demanding synchronized valve operation. One must ensure these valves can operate in tandem without compromising flow rates or the efficiency of other piping components. There must be a well-defined troubleshooting and maintenance plan for all low-pressure gas valves within a facility to extend their durability and maximize their safety.

Compliance standards

Low pressure gas valves must comply with several local and international pipe design, operation and maintenance codes and standards. These standards influence the safety of facilities, sizing, placement and fabrication of valves and the type of valves to use in specific low-pressure applications. Some common standards one should consider when sizing or selecting low pressure gas valves include:

• ASME B31.3 - contains guidelines for the design, testing, inspection, and fabrication of valves for different industries.
• API 6D - specifications for valves used in oil and gas pipelines.
• ISO 15848 - standards for fugitive emissions and leakages from process valves
• NEC and NFPA codes - define standards for fire protection and guidelines for installing electrical components.

Confirm if your low-pressure gas application should meet all or any of the above standards and local codes and regulations before purchasing and utilizing your low-pressure gas valves.

Concluding Remarks

Valves are indispensable for domestic and commercial gas services. Gas service poses unique challenges to process engineers because of its compressible nature and chemical properties. Choosing the correct process valve for low pressure gas service ensures process safety and efficiency and must consider various operating variables and chemical properties of gases. Engage valve specialists to size and design valves to meet specific performance requirements. Inspect and maintain low pressure valves regularly to extend their durability and reliability.

At Electric Solenoid Valves, we have an expansive catalog of automation products in addition to our low pressure solenoid gas valves including, electric ball valves including 3 way motorized ball valves, and high-temperature gas solenoid valves to meet the performance requirements of different industries.

If you still have questions or need help deciding what best to use in your system, our valve specialists are available to help you by phone, email, or chat-box on our website.