The core difference between ball valve and axial ball valve is the ball fixing method, sealing mechanism and applicable operating conditions. These differences directly affect their performance and application scenarios. Here's a breakdown:
1.Booked: Floating vs. Fixed
Common ball valve (float): The ball is not fixed, it depends on the pressure of the medium to press the ball to the seat at the end of the exit, forming a seal. The design is simple, but the ball's displacement depends entirely on the pressure of the medium. Under high pressure, the ball can compress the seat too much, causing the seal to wear and tear faster and even leak.
Typical Scenarios: Low to medium pressure pipelines (e.g. water, steam and ordinary oil transport), cost-sensitive and operating under mild conditions.
Trunnnion Ball Valve (fixed): Interceptor ball is fixed on the valve body with upper and lower interceptors and cannot float. Seals rely on floating valve seat-which move toward the sphere at medium pressure, allowing for a a bidirectional seal. The trunnion design reduces friction as the ball rotation, which reduces operating torque and allows for higher pressure.
Typical Scenarios: High-pressure, large-caliber pipelines (such as long-distance oil and gas pipelines, high-pressure steam systems, etc.) require stable long-term operation with manageable maintenance costs.
2. Sealing Mechanism: one-way vs. Two-way
Common ball valve: Seal depends on medium pressure to press the ball on the outlet seat, which is a one-way seal. If the medium flows in the opposite direction, pressure pushes the ball away from the seat, causing a leak. In addition, under high pressure, the ball displacement is too large, easy to cause wear and tear of the sealing ring, and often require to be replaced.
Three-dimensional ball valve: using a two-way seal design: floating seat under media pressure in both directions, tight pressure on the ball, to maintain the seal, whether forward or backward flow. Some models also have sprung seats to compensate for wear and extend seal life.
Advantages: It can adapt to high pressure fluctuations (such as oil and gas field gathering and transportation system) and reduce the shutdown risk caused by sealing failure.
3. Operating Torque and Lifespan
Common ball valve: under high pressure, ball displacement must overcome the large friction force, significantly increase the operating torque. Long-term use may cause valve stem or actuator damage. Seals wear out and valves need to be removed and replaced, resulting in higher maintenance costs.
Intercept Truncate Ball Valve: The design of the intercept ball bearing greatly reduces rotary friction and provides low operating torque and smooth operation even in the case of frequent opening and closing. Floating seat distribution pressure reduces local wear and extends service life. Some models support online seat replacement without the need to remove plumbing, improving maintenance efficiency.
Typical: truncated spherical valves used in nuclear power plants require decades of leak-free operation.
4. Anti-Flyout and safety: Normal ball valves: Under high pressure, internal pressure may push the stem out, requiring additional anti-flyout structures (such as pins or retaining rings), but limited reliability.
Interceptor: The integrated design of the stem and stem, or the use of a an anti-flyout valve stem structure, ensures the integrity of the valve even in the event of a sudden change in internal pressure, thereby improving safety.
Applicable Scenarios: Pipeline conveying flammable and explosive media such as natural gas and hydrogen.
V. Cost and applicability: Ordinary ball valve: simple structure, low cost, suitable for projects with limited budget or moderate operating conditions. However, due to frequent replacement of seals, long-term maintenance costs may increase.
Ternary ball valves require higher materials (e.g., high-strength alloy steel) and manufacturing processes, resulting in higher initial costs. However, their high pressure adaptability, long lifespan and low maintenance requirements make them an advantage in overall life-cycle costs.
Economic inflection point: The total cost of trunnion ball valves is lower when pipeline pressure ≥ 25 MPa or diameter ≥ DN 300.
Summary: How to choose?
Select standard ball valve: suitable for low and medium pressure, small diameter, clean medium (e.g. water, air), cost sensitive, low maintenance frequency.
For example: building water supply and drainage systems, air conditioning circulating water pipelines, etc.
1. Choosing high-pressure, high-temperature or corrosive media (such as oil, natural gas, chemical raw materials, etc.) requires frequent operation or on-line maintenance.
Such as: oil and gas field gathering station, nuclear power plant cooling system, high pressure steam boiler outlets.
Core logic: The trunnion-type ball valve solve the problem of sealing and service life of common ball valves under high pressure by the design of ``fixed ball seat + floating seat ''. Essentially, it adapts to different operating conditions with structural complexity. If the working pressure exceeds 16MPa or the diameter exceeds DN300, the trunnion-type ball valve is almost the only option.
