Ball Valve Materials

A ball valve is a quarter-turn shut-off valve that controls the fluid flow using a rotating ball having a hole. Selecting the right ball valve material is a crucial step in the ball valve selection process. Based on the media and the environment, several materials like stainless steel, carbon steel, and brass can be used to manufacture the housing, ball, and seal of these valves. This article discusses the popular materials used for manufacturing ball valves.

Table of contents

• Ball valve materials
• Brass ball valves
• Stainless steel ball valves
• Bronze ball valves
• Cast iron ball valves
• PVC ball valves
• Ball valve seal materials
• FAQs

Ball valve materials

Materials like stainless steel, brass, and PVC (polyvinyl chloride) are the common housing materials used in ball valves. The ball is usually made of chrome-plated steel, chrome-plated brass, PVC, or stainless steel. The valve seats are commonly made of Teflon, but they can also be made of metals or other synthetic materials. Read our article on the chemical resistance of materials for more information.

PVC ball valves

PVC (Polyvinyl chloride) is resistant to most acids, bases, salt solutions, and organic solvents. PVC has a low price (except for ISO-top valves), and the material is popularly used in water supply, irrigation, and drainage with corrosive media. PVC is not suitable for temperatures higher than 60°C and is not resistant to aromatic and chlorinated hydrocarbons. PVC ball valves have a long service life and better resistance to corrosion and cavitation. However, these valves are not as strong as brass or stainless steel and are unsuitable for high pressure and temperature applications. PVC ball valves are commonly used to control the flow of air, water, and corrosive chemicals.

Brass ball valves

Brass is stronger than plastic and hence more expensive. Brass can withstand more heat compared to plastic; hence brass ball valves are an ideal choice in home plumbing applications. Brass is highly malleable and can be welded easily compared to stainless steel. At times lead is added to brass (typically less than 2%); hence choose a lead-free variant for ball valve applications involving drinking water. Brass has better corrosion resistance compared to bronze and cast iron. Brass may break down when exposed to high chlorine levels.

Brass valves are commonly used for applications involving drinking water, oil, air, and gas. Chloride solutions (like seawater) or demineralized water can result in dezincification. Dezincification is a corrosion type where zinc gets removed from the alloy resulting in a porous structure with a significantly decreased mechanical strength. The brass housing makes the ball valves economical and withstands high pressure, high temperature, and high flow rate applications. Other main selection criteria for manual 2-way brass ball valves with approvals include the connection size, seal material, pressure rating, and temperature rating.

• Ball valves for drinking water applications have either a KTW and/or DVGW approval.
• Ball valves for gas applications have either DIN-EN 331 and/or DVGW approval.
• Ball valves for oxygen applications are made of material that doesn't contaminate the oxygen.

Approvals are required for specific applications involving drinking water, gas, and oxygen. This is because the media is sensitive or potentially dangerous if a component fails or contaminates the media. Read our article on ball valves for drinking water for more information.

Stainless steel ball valves

Stainless steel is a highly durable and resilient metal used for high temperature and pressure applications. Stainless steel has better resistance to corrosion and leaks when compared to brass. Stainless steel 316 is highly resistant to chlorides; hence the ball valves made from this material can be used in marine environments. These valves are often used in applications involving high temperatures and chemicals like swimming pools, seawater, and osmosis installations. Stainless steel 304 and 316 are the most common types; however, Type 316 has the best corrosion resistance. Stainless steel ball valves require higher operating torque than PVC or brass ball valves. This factor must be taken into consideration when a stainless steel valve is operated by a pneumatic or an electric actuator. Stainless steel ball valves come with specialized designs and approvals for gas and oxygen applications. These valves conform to DVGW approval and DIN-EN 331 standard. Approvals refer to the type of media to be used under various conditions.

Bronze ball valves

Bronze is an alloy of copper and tin; the material is strong and malleable (it doesn’t crack quickly). Parts made from bronze are manufactured by casting the material into a mold or by fabricating a pre-cast bronze ingot. Bronze has a rough, porous exterior with small cavities on the surface as a result of the casting process. Bronze alloys with selective additives can hold a polish on their surface. Bronze has many benefits like high ductility (resistance to cracking), low cost (compared to brass), and corrosion resistance. Bronze ball valves are used for flow direction control, flow shut-off, and safety relief valves. But bronze has a higher amount of lead as compared to brass making bronze ball valves questionable for drinking water applications. Lead-free bronze valves can be used for drinking water if they meet the restrictions of the clean water act.

Cast iron ball valves

Cast iron is an alloy of 96-98% iron, 2-4% carbon, and tiny amounts of silicone. Cast iron has a very high temperature tolerance; some cast iron can handle temperatures over 2100⁰F (1150⁰C). The pressure strength of cast iron depends on its class. The common types are class 125 and class 250. At low temperatures, class 125 cast iron flange is rated for pressures from 150 to 200 psi. Class 250 cast iron can work with pressure ratings from 300-500 psi and hence is tougher. These pressure values can vary with the connection end types used.

Cast iron is extremely strong, and it is immune to vibrations. The material has excellent resistance to wear and tear and temperature tolerance. But cast iron is not ductile in nature. Hence, any bending can cause the cast iron material to crack and become useless. Cast iron can work at higher temperatures when compared to PVC but gets corroded over time. Cast iron ball valves are budget-friendly and come at a much lower cost when compared with PVC and metal ball valves.

Ball valve seal materials

The various seal materials used in ball valves are discussed below. Read our article on the chemical resistance of materials for more information on the suitability of a material with the various media used in the ball valve.

NBR (Nitrile rubber)

NBR has good resistance to general wear and tear and compression. The material is suitable for ball valves involving media like oil products, solvents, and alcohol but unsuitable for polar solvents and brake fluids. NBR is sensitive to weather influences. NBR seals can provide continuous sealing for gaseous media only at low temperatures compared to the sealing properties of FKM.

FKM (Viton)

FKM seals have excellent resistance to the media, aging, and ozone. FKM is suitable for medium-high temperature ball valve applications and has higher thermal resistance than PTFE. Also, FKM has superior strength, sealing capabilities, and flexibility compared to PTFE. The material has excellent overall chemical resistance making it suitable for fuels, oils, and solvents, and the material shows more chemical resistance universally compared to NBR. FKM is typically used to manufacture O rings, gaskets, and seals for ball valves.

EPDM

EPDM is suitable for water, steam, and alcohol but shows poor resistance to oil and general solvents. EPDM is budget-friendly when compared to FKM and comes at around one-eighth of its price. But the material is not an excellent choice for use at high temperatures as opposed to FKM.

PTFE (Teflon)

PTFE is suitable for ball valve applications involving high temperature and pressure. The material is non-elastic and has good resistance to wear and tear abrasion and most chemicals. PTFE offers superior resistance to almost all fluids as compared to FKM but comes at a price of limited flexibility.

FAQs

Which material is used for the ball valve?

The most common housing materials for ball valves are brass, stainless steel, and PVC. The ball is usually made of chrome-plated steel, chrome-plated brass, stainless steel, or PVC. The seats are often made of Teflon but could also be made of other synthetic materials or metals.

What are brass ball valves used for?

Brass ball valves are commonly used in commercial and residential plumbing systems, HVAC, water wells, etc. Brass is a great option as long as there are no highly corrosive media passing through the valve.