This article combines practical applications to explain the sealing principle, structural characteristics, applicable media and selection suggestions of ball valves to help you accurately select valves according to working conditions.

1. Sealing principle of ball valve
Ball valve is mainly composed of valve body, ball, valve stem and sealing seat. The core working logic is very simple: the ball rotates 90°, the medium is switched on and off through the through hole on the ball, and the ball and the valve seat contact to form a seal to prevent medium leakage.

Whether the sealing is good or not depends on these 5 points:

·Ball machining precision
·Valve seat sealing material
·Preload design
·Valve body structural stability
·Operating temperature and pressure

According to the sealing material, there are two types of ball valves:

·Soft sealing ball valves
·Hard sealing ball valves

The two are very different in terms of applicable working conditions, temperature resistance, and service life.

2. Features and Applicable Media of Soft Sealing Ball Valves
The seat sealing ring of soft sealing ball valves is commonly made of non-metallic materials such as PTFE (polytetrafluoroethylene), RPTFE, and PPL.

(1) Core Advantages for Soft Sealing Ball Valves
·Excellent sealing performance: The soft material is elastic and can fit closely with the ball, easily achieving "zero leakage".
·Effortless opening and closing: small friction coefficient, easy opening and closing, suitable for frequent operation scenarios.
·High cost performance: low manufacturing difficulty, moderate cost, and can meet most common industrial scenarios.

(2) Suitable Media for Soft Sealing Ball Valves
Soft Sealing ball valves are suitable for:
·Water
·Air
·Steam (low temperature and low pressure)
·Natural Gas
·Oils
·Weakly corrosive media

Widely used in:
·Water supply and drainage systems
·HVAC systems
·Food industry
·Pharmaceutical industry
·General chemical pipelines

(3) Obvious shortcomings for Soft Sealing Ball Valves
While offering good sealing performance, soft sealing materials have limited high-temperature resistance.

Conventional PTFE seals are generally suitable for:
·Temperature: ≤180℃
·Pressure: Medium and low pressure conditions

If the medium contains:
·Solid particles
·High-temperature medium
·High-wear fluid

This can easily lead to valve seat wear, aging, or even failure.

3. Hard sealing ball valves: structural characteristics and applicable working conditions
The hard-sealed ball valve is a metal-to-metal seal. The surface of the ball and valve seat will be hardened (such as spray welding tungsten carbide, Stellite alloy, cladding nickel-based alloy), and the wear resistance and high temperature resistance are greatly improved.

(1) Core Advantages of Hard Sealing Ball Valves:
·High Temperature Resistance: Suitable for harsh conditions such as high-temperature steam and high-temperature oil.
·Wear resistance: When the medium contains particles, dust, and impurities, the seal remains stable.
·Long life: In high-frequency and high-pressure differential scenarios, it is much more durable than soft seals.

(2) Hard sealing ball valves are suitable for the following media
Hard sealing ball valves are commonly used for:
·High-temperature steam
·Heat transfer oil
·Coal chemical media
·Dust media
·Particulate fluids
·High-pressure natural gas
·Petrochemical media

Typical application industries include:
·Thermal power generation
·Oil refining
·Metallurgical industry
·Coal chemical industry
·Long-distance pipelines

(3) Disadvantages of Hard Sealing Ball Valves
Compared to soft-seal ball valves, their main disadvantages include:
·High manufacturing cost
·High machining precision requirements
·Large opening and closing torque
·Stricter sealing requirements under low-pressure conditions

Therefore, hard sealing structures are not suitable for all operating conditions.

4. Soft sealing VS Hard sealing: how to choose?
When selecting a valve, the following factors should be considered:

  If the operating conditions are: