Control Valve

What is a ball valve? What is a ball valve used for

What is a ball valve and what is the use of ball valve

Ball valves are stop valves, which use a ball to start and stop the fluid flow. Ball valves can be considered as quarter-turn flow valves. These valves are opened by turning a handle that is attached to a ball inside the valve the ball has a hole or port, through the middle so that when the port is in line with both ends of the valve flow will occur. By keeping the hole, perpendicular to the valve end we can block the flow. Ball valves are used for tight shutoff service. The soft seat gives a tight seating capacity for ball valves. The name ball is derived from the ball-shaped disc located within the body, these valves are light and durable. These valves are widely used in industries because it can be used in high pressure and temperature applications. They are easy to repair and can be operated manually or by an actuator. Ball valves can be used for quick on-off service, ball valves are normally used in ship, seawater…

What are the parts of the ball valve

How ball valves are constructed

The ball valve’s body could be made of metal, ceramic or plastic. Mostly metallic balls are used for metallic bodies and elastomeric materials are used to produce trim. Plastic constructions are also available. Seat materials are constructed by using nylon, neoprene, etc

The stem is not fastened to the ball in a ball valve, the stem has a rectangular portion at the ball end and that is fitted into the ball. Because of the enlargement, the valve will rotate as the stem is turned.

Bonnet cap holds the stem assembly and ball in place, and the bonnet cap is fastened to the body. Packing can be compressed by adjusting the bonnet cap. Packing of the ball valve stem is normally in the configuration of die-formed packing rings.

What are the types of ball valve

  • Full port
  • Standard port
  • Reduced port

A full port ball valve has a big sized ball so that the hole in the ball is the same size as the pipeline, and because of this friction loss is less. Unrestricted flow and larger valve.

In a standard port ball valve, the ball size is very small and has a smaller port. Flow through the valve is one pipe size smaller than the valve’s pipe size which would result in restricted flow, standard port valves are less expensive.

In reduced port valves the size of the hole is very small, that is they are two pipe sizes smaller than the valves pipe size. This would result in a restricted flow.

Based on ball type

Floating ball valve

Trunnion mounted ball valve

Floating ball valves can be used for small bore and low-pressure values. In the closed state of the floating ball valve, the ball is stressed against the soft seat by the upstream pressure. This force may cause damage to the seat in case of big-bore and high-pressure value. The trunnion ball valve can anchor the ball to the top and bottom by mechanical means. Trunnion mounted ball valve is the preferred choice ball valves in higher size and pressure ratings and they are used in pipelines and critical applications

Based on the number of body pieces

Single piece ball valve

In this type, the ball is enclosed in the body by an insert fitted along the valve’s axis. This would eliminate the possibility of body joint leakage and any chance of disconnection whilst in the service.

Two-piece ball valve

In this type, the body of the valve is split in one or two places in the same plane as the valve flange, and these pieces are bolted together. In this type of valve simplified inline maintenance can be done.

Three-piece ball valve

In this type of design, it allows the center part of the valve containing the valve, stem, and seats to be easily removed from the pipeline. This would help in efficient cleaning of disposed of sediments, replacement of seals and gland packing, all this without removing the pipes from the valve body.

Based on seat

The soft seat and metal seat are the two types of the seat in a ball valve. Soft seated ball valves use thermoplastic materials such as PTFE, NBR, etc. Metal seated ball valves use metal as the seat material such as 316 SS, Monel, etc. Each ball valve seat has its own characteristic and thus have its own advantages and disadvantages. Soft seated ball valves are used for clean fluids not used for dirty fluids, in the dirty fluid application, the metal seated ball valve is the best choice.

How does a ball valve work

In the above figure a ball valve consisting of a spherical ball located between two sealing rings in a simple body form. The ball has a hole that would allow the fluid to pass through. If they are aligned with pipe ends it gives almost full bore with less pressure drop. Rotating the ball through 90 degrees opens and closes the flow passage.

What are the advantages of a ball valve

  • Low-pressure drop and low leakage
  • They are small and rapid opening is possible
  • It can be used for quick quarter turn on-off operation
  • Tight sealing with low torque
  • Long service life and low cost
  • It can maintain and regulate high volume, high pressure, and high-temperature flow
  • Low maintenance cost
  • It can be installed in a vertical pipeline
  • It has a higher flow capacity
  • No lubrication is needed
  • Fire safe and antistatic features

What are the disadvantages of a ball valve

  • The seat can wear if it is used for throttling
  • Quick open may cause hammer
  • Suspended particles can settle in ball valves when they are used for slurries or other applications and this would badly affect the valve

What are the applications of ball valves

  • Flow control and pressure control
  • It can be used for shut-off service
  • It can handle corrosive fluids
  • It can be used for high pressure and high-temperature applications
  • LPG bottling plants
  • Power plants
  • Chemical process industries
  • Petrochemical industries
  • Refineries
  • Oil and gas processing
  • Onshore and offshore platforms

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