What is a ball valve?

10/5/2015

Ball valves are probably the most used valves in the process industry.

While ball valves do nothing more than start a flow or stop a flow, they have some advantages which make these valves very interesting for use in a process design.

A ball valve is used for opening and shut-off applications.
By turning the handle for a quarter (90 degrees) the valve reaches it's open- or it's closed position.
The most important part of this type of valves is a ball, in which a bore has been created.

Types of ball valves

Full bore ball valves
When the diameter of the bore in the ball, is the same as the inner diameter of the connecting tube, it is called a "full bore ball valve".
When this type of valve is in "open" position, the flow is obstructed by nothing. That means these type of ball valves have very little pressure loss and that can be an important issue in some process designs.
Full bore valves are more expensive and have larger dimensions than reduced bore ball valves.

Reduced bore ball valves
Reduced bore ball valves have smaller hole, so the flow area in the ball is smaller than the flow area in the connecting pipes. This results in a larger pressure drop than the full bore ball valves.
Despite this disadvantage, you are generally better off using a reduced bore ball valve because they are much cheaper than a full bore version.

V-bore ball valves
Though a ball valve isn't very good in throttling services, there are types of ball valves with as V-shaped bore.
This shape allows a more controllable flow than the straight bore ball valves.

Three way ball valves
Three way ball valves have three connections instead of two and they have a T or L shaped bore in the ball.
This makes it possible to combine flows, or to change from one to another flow direction, with the use of only one valve. Sometimes you can use a three way ball valve instead of 2 regular straight ball valves.

One piece ball valves
This is the cheapest housing type for ball valves. The housing is made of one full piece of material. These valves can best be used when the fluid is clean and harmless. When also no maintenance is expected, a one piece ball valve could be a good choice. The bore is almost always reduced to make them as cheap as possible.
Repairing a one piece ball valve is often more expensive than to buy a new one.

Two piece ball valves
A two piece ball valve can easier be maintained than a one piece ball valve. It can be removed from the piping system for maintenance or replacement. The bore is mostly reduced but full bore versions are also easy to obtain.

Three piece ball valves
When you need a valve that is easy to clean, maintain and repair, the three piece ball valve is probably the best option.
The middle piece of the valve , containg the ball, the stem and seats, can be removed without disconnecting the pipes from the valve body.
Of course the three piece ball valves are the more expensive types, so it's mostly an an economic assessment to choose a three piece or a two piece housing type for the process design.

When are ball valves used?