When trying to select metallic valves for your system, it is important to keep track of the choice of the material for these valves, as the type of material can have a significant impact on performance, durability, and compatibility with the system's requirements. Even within the same broad category, materials are broken down into different grades, with different grades of metals offer varying levels of strength, corrosion resistance, and temperature tolerance. By choosing the correct type of material for specific use cases, it can maximise the lifespan of the servicing valve and avoid disruptions caused by potential issues arising from the lack of compatibility between the flow medium and the material in contact. Below is a deeper exploration of common metals used in valves, to give a brief understanding of suitability of these materials for different use cases.
Copper Alloys
Brass and bronze are alloys of copper that are frequently employed as the material for valves and fittings used in water systems and residential plumbing. Both types of alloys come in various grades with different compositions that impact their properties. In Singapore, copper alloys approved for use in potable water are restricted to a specific set of copper alloy grades. This was primarily driven for transition to modern regulations standards regarding lead content within copper alloys. The full list of usable copper alloy grades in Singapore’s potable water system can be found listed in the 4MSI (The four Member States-Initiative) “Common Approach on Metallic Materials Part B: Positive List of Compositions”.
Common Grades (For Potable Water in Singapore):
CW511L: This is a lead-free dezincification-resistant (DZR) brass alloy commonly used in areas that require compliance with strict drinking water and environmental regulations. CW511L is known for its excellent corrosion resistance and machinability and with its lead-free formulation and dezincification resistance, this makes it especially valuable for plumbing applications where safe water quality and long-term durability are essential.
CW724R: This is a high-performance DZR brass created by Diehl under the brand name CUPHIN, offering excellent corrosion and dezincification resistance. On top of the useful properties that other DZR brass such as the CW511L offers, the CW724R comes with the added property of its antimicrobial nature. The alloy is thus frequently used in water systems requiring strict hygiene and health safety requirements due to its lead-free and antimicrobial nature.
CW617N: This brass alloy is commonly used for components that require forging and machining, particularly in plumbing and hydraulic systems. It is widely used in plumbing and hydraulic fittings, as the ease of forging and machinability is able to provide a cost-effective solution as a material choice. However, CW617N contains a small amount of lead which limits its use in some potable water applications due to lead-content regulations. In the case of the 4MSI list, this restriction applies to allow the material to only be used for fittings and valve bodies in buildings but not for pipes.
Common Grades (Non-Potable Water in Singapore):
CC333G: This copper alloy is also known as nickel aluminium bronze, a high-strength copper alloy with excellent corrosion, wear, and dezincification resistance. The alloy is particularly useful in marine environments and other settings with exposure to harsh conditions, as it is highly resistant to saltwater corrosion, scaling, and erosion. Although not allowed to be used for potable water in Singapore, CC333G is still commonly used for valves, pump components, and fittings where durability and resistance to aggressive environments are required.
Cast Iron
Cast iron is strong and durable and are commonly used in larger valves and systems where strength and structural integrity is a necessity. Their applications comprise of water systems, steam applications, and industrial pipelines, especially in non-corrosive or lined systems. These materials are often coated with a protective layer, such as fusion bonded epoxy coating for use with water systems to protect the material from corrosion. There are different types of cast iron, each with distinct properties.
Common Grades:
Gray Cast Iron (ASTM A126 Class B): Known for its excellent machinability and vibration damping properties. This is the most common cast iron used for valve bodies, especially valves that are of large sizes
Ductile Iron (ASTM A395): Ductile iron is a type of cast iron that offers improved flexibility and impact resistance compared as compared to gray iron. It is often used for high-pressure valves due to its capability of withstanding more stress before failure.
Stainless Steel
Stainless steel is highly resistant to corrosion, making it suitable for harsh environments and areas that require strict hygiene. They are often used in chemical processing, pharmaceutical, food and beverage, high-temperature steam systems and extreme low-temperature cryogenic applications. Different grades of stainless steel are tailored to handle various levels of corrosion, temperature, and pressure. Austenitic stainless steels can handle a wide range of temperatures (from around -196°C to upwards of 900 °C), making them one of the most versatile materials for extreme low to high temperatures.
Common Grades:
304 Stainless Steel: One of the most common grades of stainless steel, containing approximately 18% chromium and 8% nickel. This grade of steel offers good corrosion resistance in most environments at a relatively cost-effective price. However, it may not withstand highly acidic, chloride-rich and marine environments and as such other grades of stainless steel should be considered for more corrosive environments.
316 Stainless Steel: This grade of steel contains molybdenum (2-3%), which enhances its resistance to chloride corrosion, making it ideal for marine and chemical processing applications. 316, albeit slightly more expensive, is preferred over 304 in harsher environments due to its better corrosion resistance.
Duplex Stainless Steel (2205): This is a mix of austenitic and ferritic stainless steel, offering higher strength and better resistance to stress corrosion cracking than 304 and 316. Although expensive, it is still commonly used in demanding applications such as oil and gas or petrochemical processing for its highly sought-after properties.
Carbon Steel
Carbon steel is a strong and economical choice for valves in high-pressure environments. However, it is more prone to corrosion than stainless steel, making it suitable for applications where corrosion resistance is not a primary concern. Carbon steels offer cheaper alternatives to higher quality steels suitable for high-pressure steam, oil, and gas systems, and even some cryogenic applications with the LF2 grade.
Common Grades:
A105 (Forged Carbon Steel): This steel grade is widely used for valve bodies and fittings in high-pressure systems. It offers excellent strength and toughness but needs to be coated or lined if exposed to corrosive fluids.
WCB (ASTM A216 Carbon Steel Castings): WCB is the most common carbon steel used in valve casting. It is primarily used for valves that handle non-corrosive or low-corrosion fluids, such as water or oil.
LF2 (Low-Temperature Carbon Steel): This grade is designed for low-temperature applications, offering both strength and impact resistance down to -46°C. It’s used in cryogenic valves for cold environments like those found in LNG processing.
How to Choose the Right Valve Material and Grade
Choosing the right valve material and grade is essential for ensuring optimal performance and longevity in industrial applications. By understanding the specific properties of different metal grades and their suitability for pressure, temperature, and environmental factors, you can select a valve that meets the precise needs of your system. Plastic materials, although not mentioned in the article, can also be commonly found and used in our everyday plumbing and other specialised industrial uses. Key points to look out for when selecting the valve material is to balance the corrosive, temperature and pressure requirements while also understanding the cost-effectiveness of the selected material. Stainless steel duplex grades might be suitable for general potable water purposes due to its superior properties, however there are cheaper lower quality materials that can be used instead without compromising the valves’ quality in those general use cases.
We at Val-Technik would be able to provide professional opinion on the appropriate material choices for valves and offer quality products from reputable global brands for use in your systems.
For more information and consultation regarding the types of material used and if there any specific material requirements for different types of valves, please email us at sales@val-technik.com.sg or call 6742 2770.
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