Ball Valve Types: Full‑Bore vs Reduced‑Bore, Floating vs Fixed, Soft vs Hard Seal

1. Full bore ball valve and reduced bore ball valve
Ball valves can be divided into: according to the size of the flow channel:
· Full bore ball valve
· Reduced diameter ball valve

1) Full bore ball valve
The diameter of the ball hole of a full-bore ball valve is close to the inner diameter of the pipe. When fully open, the medium passes through with little resistance.

Features:
· Small flow resistance
· Small pressure loss
· Strong flow capacity
· Suitable for pipelines requiring pigging
· Suitable for occasions with low pressure drop requirements

Commonly used for:
· Oil and gas pipelines
· Long-distance pipelines
· Working conditions requiring low pressure drop
· Pipelines that need to be passed by pigs

2) Reduced diameter ball valve
The ball through hole of the reduced diameter ball valve is smaller than the inner diameter of the pipe, and the internal flow path of the valve is reduced.

Features:
· Small structure
· Light weight
· Lower cost
· The flow resistance is larger than the full diameter
· Small flow capacity

Commonly used for:
· Normal cutting
· Small diameter pipeline
· Occasions where the pressure drop requirement is not high

3) How to choose?
If the process requires:
· Low pressure drop
· Large traffic
· Pigging
· Strong flow capacity

Full bore ball valves may be considered. If it is just a normal cut-off and the pressure drop requirement is not high, you can consider a reduced-diameter ball valve.

But when selecting, you can't just look at DN, but also:
· Valve bore size
· Cv/Kv, valve flow coefficient
· Medium flow
· Allowable pressure drop
· Process requirements

2. Floating ball valve and fixed ball valve
Ball valves can be divided into: according to the ball support method:
· Floating ball valve
· Fixed ball valve

1) Floating ball valve
The ball of the floating ball valve is not completely restricted by the upper and lower fixed shafts. The sphere can produce slight displacements under the action of medium pressure.
When closing, the medium pressure pushes the ball against the valve seat on the outlet side, thereby forming a seal.

Floating ball valves are commonly used for:
· Small diameter
· Medium and low voltage
· Normal cutting conditions

Advantages:
· Simple structure
· Good sealing
· Lower cost
· Easy to maintain

Disadvantages:
· The operating torque is larger when the pressure is high and the diameter is large.
· The valve seat bears greater pressure
· Not suitable for all high pressure and large diameter working conditions

2) Fixed ball valve
The ball of the fixed ball valve is supported by the upper and lower valve shafts. The position of the sphere is relatively fixed and does not move significantly like a floating ball.
The seal mainly relies on the valve seat spring or medium pressure to push the valve seat toward the ball.

Fixed ball valves are commonly used for:
· High voltage
· Large diameter
· Long-distance pipelines
· Important cutting conditions

Advantages:
· Small operating torque
· Suitable for large diameter
· Suitable for high pressure working conditions
· Sphere support and stability

Disadvantages:
· Complex structure
· Higher cost
· High maintenance requirements

3. Soft sealing ball valve and hard sealing ball valve
Ball valves can be divided into: according to sealing materials:
· Soft sealing ball valve
· Hard seal ball valve

1) Soft sealing ball valve
Soft sealing ball valves usually use non-metallic valve seats.

Common materials include:
· PTFE
· Reinforced PTFE
· PPL
· Nylon
· Rubber materials

Advantages:
· Good sealing performance
· Easy to achieve strict isolation
· Small switching torque
· Suitable for clean media

Disadvantages:
· Not resistant to high temperatures
· Not resistant to strong erosion
· Not suitable for media containing hard particles
· The valve seat is prone to aging or deformation

Commonly used for:
· Water
· Air
· Nitrogen
· Oil products
· Clean liquid
· Low temperature and low pressure corrosive media

2) Hard seal ball valve
Hard seal ball valve adopts metal seal. The ball and seat are generally hardened.

For example:
· Spraying carbide
· Surface welding of cemented carbide
· Metal-to-metal sealing

Advantages:
· High temperature resistance
· High pressure resistance
· Erosion resistant
· Wear resistance
· Suitable for harsh working conditions

Disadvantages:
· Sealing grade is usually not as easy as soft sealing to achieve zero leakage
· High processing accuracy requirements
· Higher cost
· Large operating torque

Commonly used for:
· Steam
· High temperature oil products
· Particle-containing media
· High pressure medium
· Strong erosion conditions