May. 20, 2024
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Unlike the standard ball valves, most gas ball valves are tested and approved by CSA. These valves are vital for combustible gas service in different industrial applications. They are used in natural gas, manufactured gas, and liquefied petroleum gas pipelines.
A gas ball valve is a quarter-turn flow control device that is designed to offer better performance, shut off and sealing characteristics than the conventional ball valves. Unlike high pressure, high temperature, water service ball valves, gas ball valves adopt a compact and lightweight valve body design that increases their versatility, making them suitable for different applications.
Gas ball valves are predominant in applications and piping systems conveying combustible fluids like hydrocarbons, liquefied petroleum gas (LPG), natural gases, and chemical vapors. These valves are also ideal for boilers, furnaces, gas stoves, residential and commercial water heaters.
Flow control applications relying on gas ball valves operate under high pressure and temperature. Given the combustible nature of most of the working fluids, it is vital to prevent leakage at the valves. Sealing and protection against fugitive emissions rely on the metal-seated gas ball valves or PTFE seats.
The benefits of using gas ball valves for different industrial applications are:
Excellent shut-off characteristics — The valves open and close quickly in response to pressure conditions of the pipeline. It is vital for preventing backflows and contamination.
Versatility and efficiency — Gas ball valves have a compact design that fits into different industrial applications. They operate at low torque and require simple actuation mechanisms.
Durability and easy maintenance — These valves provide excellent flow control throughout their service life and demand minimal maintenance interventions.
Before using gas ball valves for combustible fluid service, they require approval from Canadian Standards Association (CSA). The association rates the valves based on application areas and country-specific requirements. CSA is accredited by several US regulatory authorities including the Occupational Safety and Health Administration (OSHA) and the American National Standards Institute (ANSI).
Valves bearing CSA ratings can be used in different industries across the US. According to the CSA ratings, gas ball valves designed for outdoor fluid applications in the USA bear the BRS125G-rating and CAN 3.16 in Canada.
For indoor applications, the CSA ratings are the same for the USA and Canada. Any ball valve bearing the ½ PSI and 5G- ratings are strictly used for indoor gas applications. The ½ PSI rating indicates that the installation location of the valve is on the appliance. Household piping systems use valves bearing the 5G rating. Indoor gas systems operate at a lower pressure when compared with outdoor piping systems.
CSA 3.16-15 standards apply to all lever-operated gas shut-off valves. These are metallic gas ball valves that are manually operated and contain flanged, threaded, or welded ends. Their service temperatures range between -1048°F (-600°C) and 3272°F (1800°C), while their maximum pressure limit is 125PSI. These valves are suitable for natural gas, liquified petroleum gas, and manufactured gas service.
Valves under the CSA 3.16-15 ratings can be used for methane gas service in sewage treatment plants. However, they are likely to suffer from the negative impacts of contaminant accumulation around the valve body. Gas ball valves are unsuitable for use in piping systems with traces of hydrogen sulfide (sour gas).
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For the efficiency of fluid flow applications, it is necessary to control and monitor fluid pressure. Gas ball valves are equipped with pilot taps for fixing pressure gauges. With these gauges, operators can monitor the pressure of the piping system and perform pressure tests. Fixing the pressure gauges at the valves guarantees accurate pressure control in the system to facilitate the safety and consistency of gas applications.
Gas ball valves have standard pilot taps in the form of ⅛" female pipe thread or female pipe taper (FPT). The pilot taps come with a ⅛" tapering male pipe thread plug that is tightened to prevent leakages.
Several manufacturers use yellow handles on the valves for identification purposes. Though this is not a standard visual indicator, it is a quick way for buyers to identify ball valves that are approved for combustible gas service. When selecting gas ball valves, do not just rely on visual indicators. Confirm that the intended piping requirements match the CSA approvals and ratings.
Gas ball valves are used in applications with varying temperature and pressure ranges. For the safety of operations, the valves are subjected to rigorous air tests to establish their efficiencies at different operating conditions. According to CSA standards, gas ball valves are tested to withstand 1.5 times their rated valve pressure. Gas ball valves with the CAN 3.16 approval are designed for higher pressure ratings. In some cases, they may be exempt from pressure tests.
The following are gas ball valve ratings and the accompanying test pressures in PSIG (Pounds per square inch gauge)
CAN 3.16 rating — test pressure is 125PSIG
BRS125G — test pressure is 188PSIG
½ PSI — test pressure is 3PSIG
5G — test pressure is 7.5 G
Each gas ball valve has a specific CSA approval rating. However, it is common to find valves with the same CSA ratings having different pressure and temperature ratings. Valves meant for industrial processes with extreme temperatures/pressure may require modifications and additional tests to meet the minimum CSA approval requirements.
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Gas ball valves have different constructions to suit their application areas. Piping systems for natural gas service, supply of clean gases or compressed air use fully welded ball valves. These valves have a compact design, are easy to insulate, provide bi-directional tightness, and are designed to be maintenance-free. Such ball valves are fabricated using high-strength materials, have spring-loaded PTFE seals and O-rings for maximum sealing.
Processes in which the working media should be fully open or fully closed use gas ball valves with flanged and welded ends. They are in sections like heating pipeline crossings or heat exchanger stations.
When selecting gas ball valves, consider the installation areas. Are the valves intended for indoor or outdoor usage? After that, select the appropriate size that will meet the desired process parameters.
When selecting a gas ball valve for any industrial application, identify the performance requirements of the system. It will include factors like flow rates, pressure, and temperature ranges. Identify the chemical characteristics of the service medium. Piping systems with traces of sour gas will use gas ball valves with PTFE seats due to their inert nature against chemicals, unlike metal-seated valves that are likely to corrode under similar conditions.
Gas ball valves selected for critical gas pipelines should be easy to maintain or demand minimal maintenance interventions. The quantity of abrasive media and contaminants in the piping system should be minimal to prevent premature valve damage.
Gas ball valves provide an affordable and often ideal solution for combustible gas service in different industrial applications. Their application is guided by CSA ratings and approvals that guarantee safe usage under varying process conditions.
Need guidance in determining the appropriate gas ball valve for a specific application?
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Principle of Cryogenic valve|Standard of Cryogenic valve|Selection of Cryogenic valve
The so-called cryogenic valve is a kind of altra-low temperature valve, as the name implies, is a valve suitable for working in cryogenic conditions. In the valve industry, valves that tend to -40°C are called cryogenic valves. Cryogenic valves are generally used in cryogenic systems such as liquid helium, liquid hydrogen, liquefied natural gas, and air separation. The medium used is liquid helium, liquid hydrogen, liquefied natural gas, liquid nitrogen, liquid oxygen and other cryogenic fluids. Under low temperature conditions, conventional metal hard seals and non-metal soft seals cannot meet the sealing requirements. In order to ensure that cryogenic valves can operate safely and reliably at low temperatures, there are some special considerations and requirements in the design and manufacture of cryogenic valves. see photo attached is a cryogenic triple offset butterfly valve.
Principle of ultra-low temperature valve: For valves used in ultra-low temperature conditions, the medium temperature is very low, and the metal materials will experience low temperature cold brittleness. The strength and hardness will be greatly improved, and the plasticity and toughness will be greatly reduced. This will directly affect the performance and safety of the valve. If an ordinary valve is used, the low temperature will freeze the packing in the valve stuffing box, and it will not be able to play a sealing role. In this way, the valve needs to be lengthened from the sealing seat on the bonnet to the bottom of the stuffing box. With sufficient isolation space and heat dissipation distance, the low-temperature medium in the valve body will not freeze the packing. As shown in the figure, the part marked with 175mm is the lengthened part.
In ultra-low temperature conditions, the valve stem and valve body can only adopt stuffing box or bellows structure. There are many restrictions on the use of bellows. Generally, the structure of the stuffing box seal is adopted. The stuffing box seal structure is simple to process and convenient to maintain. However, the sealing effect cannot be guaranteed under the condition of <-40℃, so the ultra-low temperature valves are all Keep the stuffing box as far away from the material as possible, and choose packing with low temperature characteristics.
Selection of ultra-low temperature valve:
Valve body: Ferritic stainless steel can be used when the temperature is higher than -100°C, austenitic stainless steel can be used when the temperature is lower than -100°C, copper alloy or aluminum alloy can be used for low-pressure and small-diameter valves. Stem: Made of austenitic stainless acid-resistant steel, it needs to be properly heat-treated to increase the tensile strength. At the same time, it must be hard chrome plated (coating thickness 0.04~0.06mm) or nitriding treatment to increase the surface hardness.
Gasket: When the working temperature is higher than -196℃ and the maximum low temperature working pressure is 3MPa, the asbestos rubber sheet made from long fiber can be used; when the working temperature is higher than -196℃ and the maximum low temperature working pressure is 5MPa, it can be used. Stainless steel spiral wound gasket with asbestos, stainless steel spiral wound gasket with PTFE, or stainless steel spiral wound gasket with expanded graphite.
Fasteners: when the temperature is higher than -100°C, the bolt material is Ni, Cr-Mo and other alloy steels, which need to be properly heat-treated to prevent thread bite; when the temperature is lower than -100°C, the bolt material can be austenitic Body stainless steel. The nut material is generally Mo steel or Ni steel, and the thread surface is coated with key disulfide.
Ultra-low temperature valve design standards:
1. Design: API6D, JB/T7749
2. Valve routine inspection and test: according to API598 standard.
3. Low temperature inspection and test of valve: According to JB/T7749.
4. Drive mode: manual, bevel gear drive and electric drive device.
5. Valve seat form: The valve seat adopts a welded structure, and the sealing surface is welded with cobalt-based hard alloy to ensure the sealing performance of the valve.
6. The ram adopts an elastic structure, and a pressure relief hole is designed at the pressure inlet end.
7. One-way sealing valve body is marked with flow direction mark.
8. The low-temperature ball valve, gate valve, and stop valve adopt a long neck structure to protect the packing.
TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D
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