This article provides an overview of ball valves, including what they are, the different types and materials available, factors that determine quality and price, and how to select ball valves for your needs. Ball valves are quarter-turn shut-off valves that control flow through a circular orifice.
What Are Ball Valves?
Ball valves contain a spherical rotor with a circular hole through the center, called the ball or sphere. They are closed when the hole in the ball is perpendicular to the flow and open when the hole is aligned with the flow. Ball valves provide a leak-tight on/off control of flow in a system.
Types of Ball Valves
The main types of ball valves include:
•Two-piece: The simplest and most affordable type. Has a separable body and bonnet for easy stem and seal replacement.
•Three-piece: Also has a separable body, with a material called the thrust retainer around the upper stem guide. This reduces seat cracking from gland adjustment in high-pressure/high-temperature applications.
•Concentric: Has only one seating ring located outside the peripheral diameter of the ball. Often used where reduced pressure drop and unrestricted flow relative to seat diameter are required.
•Single/double-ported: Double-ported has two holes through the ball to increase flow rate capacity. Single-ported is more common and economical.
•Floating/trunnion: The floating ball is free to move into the valve seats. Trunnion mounts the ball with trunnion bearings to contain the ball, reducing seat wear and allowing higher pressures. More expensive but lasts longer.
•Multi-turn: Has a notch in the ball/stem to allow controlled partial opening/closing. Often used for regulating flow or balancing systems.
Common Ball Valve Materials
The materials used for ball valve components depend on the fluid and temperatures in the system. The most common options include:
•Stainless steel: For high-temperature and corrosive fluids. More expensive but extremely durable. Common types are 316 and 420 stainless steel.
•Brass: Good for low-pressure plumbing systems handling potable water. Not for high temperatures. Prone to dezincification in some water conditions.
•Bronze: Similar to brass but with higher strength. Can handle higher pressures and temperatures than brass.
•PVC/CPVC: For corrosive chemical handling. Limited pressure/temperature ratings. Prone to brittle failure if overheated.
•Chlorinated poly: For corrosive chemicals. Better high-temperature performance than PVC but is more costly.
•Carbon steel: For high temperature/pressure needs on large sizes where other materials would be prohibitively expensive. Requires painting or plating to prevent corrosion.
Factors that Determine Ball Valve Quality and Price
Several factors significantly impact the quality, performance, and cost of ball valves:
• Materials: Valve material is the primary factor in determining quality and price. Stainless steel and high-alloy valves are superior for high-performance needs but much more expensive than brass or bronze valves.
• Pressure/temperature rating: Higher-rated valves require thicker walls and more durable materials, so they cost more to produce. Choose ratings at least 125% of your maximum working conditions.
• Valve size: Larger ball valves, especially in sizes above 2 inches, require more materials and time to fabricate, so prices increase significantly with size.
• Type: Multi-port, trunnion-mounted, and multi-turn ball valves tend to cost more than standard floating two-piece ball valves due to their more complex designs.
• Brand: Reputable industrial valve brands typically charge a premium over generic Chinese-made valves. Paying more for a trusted brand usually means higher quality and reliability.
• Production method: Factors like the amount of automation and hand-work involved in the production, quality control standards, local labor costs, and other overhead also contribute to the overall ball valve price. Advanced machining and grinding methods required to meet tight tolerances increase costs.
• Supply and demand: When supply is limited and demand is high, ball valve prices also rise. Excess supply and competition drive prices lower. The cost of materials also continues to influence ball valve pricing over the long term.
In summary, ball valves control flow through a circular orifice. Many types are available in a variety of materials for different applications and budgets. However, you should buy the highest quality valves you can afford for optimum performance and service life, especially for critical processes. Reputable, high-performing ball valves may cost more upfront but save money in the long run.