Floating ball valves are a type of ball valve where the closing system stays suspended, which means it has a very simple design and operation, so it can be used for applications where the most important factors are the speed to open or close the flow, easiness to change the direction of such flow or simple installation.

If more complex requirements are present, such as a higher resistance to harsh environments, high temperatures and high pressures, other designs should be considered. Perhaps using a two-piece or three-piece design would be a better idea, while considering the type of sealing is another important factor affecting the decision in those cases.
 

All You Need to Know About Floating Ball Valve

Floating Ball Valve Standards

a. Design standard    API 608 /API6D

b. Test standard    API 598/API6D

c. Fire Standard    API 607

d. Wall thickness standard    ASME B16.34

Floating Ball Valve Classification

a. One-piece floating ball valve

One-piece ball valve and flange gate valve belong to the same type of valve, being the closing member the main difference between them. Obviously, the one-piece ball valve uses a sphere in which rotates around the center line of the body, while the flange gate valve opens a type of gate by lifting the blocking structure when the handle is rotated. The ball valve is mainly used in the pipeline to cut off, distribute and change the flow direction of the medium. Also known as integral ball valve, it is a new type of valve which has been widely used in recent years.
 

b. Two-piece floating ball valve

The two-piece floating ball valve takes its name from the fact that it is made of two parts called the left and the right body which are connected to each other through threads and bolts or by welding them. This type of valve is suitable for different working conditions such as high temperature and high pressure.
 

c. Three-piece floating ball valve

The three-piece floating ball valve refers to a floating ball valve whose body is composed of three parts from left to right. The parts are usually a body and two bonnet. Similar to the case of two-piece floating ball valves, the end caps are usually connected through threads and bolts, by welding them or flanged to the pipe.

Floating Ball Valve Sealing principle

Since the ball of the floating ball valve is not restricted by any component, when the valve is closed, the medium is pressed from one end upstream) of the valve, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end (downstream) of the valve, thus producing an outlet seal. 

Floating ball valve Feature structure

a. The status of the valve can be understood by looking at the position of the handle. If it is crossing the pipeline it means it is closed, and if it is along the pipeline, it means it is open.  

b. Misuse of the valve can be prevented by means of a locking device as presented in the graphics.

c. The valve comes with an anti-flying structure on the stem, and the packing can be replaced online.

The bottom-mounted valve stem has a shaft shoulder at the root of the stem. The outer diameter of the shaft shoulder is larger than the stem hole

Top-mounted stem with a gland structure, where the inner diameter of the gland hole is smaller than the diameter of the stem shoulder

d. The anti-static design is more suitable for flammable and explosive media.

Dry valve, DC voltage not exceeding 12V, resistance not exceeding 10Ω

Since the filler and bearing affect the conductive performance, antistatic components such as stainless-steel springs and stainless-steel balls are provided between the valve stem and the valve body, and between the valve stem and the ball.

e. Fire safe design

① Valve seat (ball and valve body)  

The valve seat is surrounded by three sides, and a fireproof sealing lip is processed on the side near the flow channel, which can play the role of an emergency sealing after the valve seat is burnt out.

② Medium flange (valve body and bonnet)

It is sealed with a stainless-steel spiral graphite fireproof gasket, and the structure uses metal – metal contact.

③ Packing (stem and body)
It adopts a multi-ring graphite packing to seal, since graphite packing can prevent the medium from leaking out.

 
Various sealing forms suitable for different working conditions

a. Composite seal       

• A valve seat is provided on both the upstream and downstream sides of the valve, and the valve seat is embedded in the valve body by means of a special press.

• It relies on the elasticity of the valve seat to provide the initial preload.

• The seats at upstream and downstream sides of the valve are completely symmetrical, and there is no restriction on the installation direction. It is a two-way valve.

• It is mainly used for applications with working conditions below 150℃ (special material can reach 250℃)

• It has the advantages of flexible operation and reliable sealing.

• Commonly used soft sealing materials include: PTFE, RPTFE, NYLON, PPL, PEEK, etc.
 

b. Metal hard seal

• The upstream side of the valve is provided with a seat assembly, and the sealing surface is covered with a carbide. The downstream side of the valve body is directly welded.

• The seat at the upstream side of the valve provides the necessary initial sealing specific pressure for the valve, the seat at the downstream side of the valve plays the main sealing role, and the valve has a restricted installation direction.

• These seals are mainly used in applications with working conditions that include high temperature, and the presence of particles, dust, slurry, etc.

• It has the advantages of being high temperature, high pressure, wear and erosion resistant, while being a reliable sealing.

• The usual surface covering material is Stellite cemented carbide.
 

c. Soft seal

• Two valve seat components are provided on both the upstream and downstream sides of the valve. Each valve seat component is formed by a valve seat, a valve seat ring, and a gasket ring. The valve seat ring is fixed in the valve seat by the gasket ring, and an O-ring is arranged between the valve seat and the valve body type sealing ring. On the one hand, the valve seat and the valve body are sealed, on the other hand, it can provide the initial pretension of the valve.

• The two valve seats are completely symmetrical, the valve has no restrictions on the installation direction, and it is a two-way valve.

•The metal seal is the primary seal, which is used to cut off most of the medium and block the particulate impurities in the medium from entering the soft sealing surface. The soft seal is the secondary seal, which is used to completely block the medium.

• These seals are mainly used in applications where the working conditions include the presence of particles, dust, slurry and other media under normal temperature (below 150℃)

• It has the advantages of having flexible operation, wear and erosion resistance, long service life and being a reliable sealing type.

• The material used for soft seals (valve seat ring) is usually a type of rubber.

 
Floating Ball Valve advantages and disadvantages

Advantages of floating ball valve:

• The fluid resistance is small, and the resistance coefficient is equal to that of the pipe section of the same length.

• It has a simple structure, a small size and a light weight.

• It is tight and reliable. Currently, the most widely used sealing surface material of a ball valve is plastic, which has good sealing performance and has been widely used in vacuum systems.

• It is easy to operate with a fast shutter speed. The rotation from the fully open to the fully closed position is as long as 90 [deg.], to facilitate remote control.
 

Disadvantages of floating ball valve:

• The sealing surface of the sphere can be damaged very easily, and it is not suitable for the applications with working conditions where the medium contains particles.

• Soft-sealed valves are not practical for high temperature and high pressure conditions.

• Hard-sealed valves require high sealing forces and high torque to create the protection barrier.

 
Floating Ball Valve Selection guide

a. The main pipeline for oil and natural gas transportation needs to be a clean pipeline, and it needs to be buried underground. For buried pipelines, it is recommended to select full-diameter welded or flanged ball valves. For branch pipes, it is recommended to select flange connections or welded connections with a full diameter or a reduced diameter ball valve.

b. For the pipeline and storage equipment of oil products, it is recommended to use flanged ball valves.

c. For city gas and natural gas pipelines, the choice of suggested is floating ball valves with flange connection and female connections.

d. The metallurgical oxygen piping system should use rigorously de-aliphatic oxygen valves.

e. When working with fluids at very low temperatures, it is recommended to select the low temperature ball valve with a valve cover

f. The pipeline system of the catalytic cracking unit of the oil refining unit can be used with a lifting rod ball valve.

g. In the equipment and piping systems of corrosive media such as acids and alkali used in the chemical industry, it is appropriate to select stainless-steel ball valves made of austenitic stainless steel with polytetrafluoroethylene as the seat ring.

h. Metal-to-metal sealed ball valves can be used on the piping systems or devices which work at high-temperature in metallurgical systems, power systems, petrochemical plants, and urban heating systems.

i. When flow adjustment is required, worm gear drive, pneumatic or electric adjustment ball valve with V-shaped opening can be selected.