PVC Ball Valves Knowledge Base

Ball Valves

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Article Contents

  • What Is a Ball Valve?
  • What Sizes of Plastic Ball Valve Are There?
  • What Is a Double Union Ball Valve?
  • What Are the Advantages of a Double Union Ball Valve?
  • How Do You Connect a PVC/ABS Double Union Ball Valve?
  • What Is the Difference Between a Single Union and a Double Union Ball Valve?
  • What Advantages Does a Ball Valve Have over a Gate Valve?
  • What Advantages Does a Ball Valve Have over a Butterfly Valve?
  • 4 Important Things About Ball Valves

What Is a Ball Valve?

A ball valve uses a drilled ball to open and close flow in a pipeline. Ball valves only turn through 90 degrees between fully open and fully closed, which makes it very difficult to accurately control the flow rate. Ball valves may be made from metal (such as brass) or plastic (such as PVC or ABS).

What Sizes of Plastic Ball Valve Are There?

PVC and ABS ball valves are typically manufactured between 16mm and 110mm (⅜” to 4″ imperial). Valves larger than 110mm/4″ would be too heavy to handle, very difficult to turn manually and very expensive due to the amount of plastic required.

What Is a Double Union Ball Valve?

A double union ball valve has a union nut on both ends of the valve. This holds the connecting end of the valve against a seal on the main body. The union nuts on either side of the valve can be unscrewed and the central body removed for servicing.

What Are the Advantages of a Double Union Ball Valve?

A double union ball valve enables the main body of the valve to be removed and serviced or replaced very quickly, without cutting the pipe. If double union ball valves are installed either side of a pump or other piece of equipment, the unions nearest the pump can be removed and it can be removed or changed.

How Do You Connect a PVC/ABS Double Union Ball Valve?

A double union ball valve can be supplied with either threaded or solvent weld ends:

  • When solvent welding to a pipe, it is important to make sure that no cement enters the body of the valve, or the ball may weld and the valve will not turn. To prevent this, many installers remove the valve end and the union before cementing; however, you must ensure that the union end is on the pipe before you cement.
  • A union end makes threaded connections much easier, as the valve end can be turned independently of the valve.

 

What Is the Difference Between a Single Union and a Double Union Ball Valve?

A single union ball valve has a fixed socket on the discharge side of the valve, and a union on the supply side, whereas a double union ball valve has union ends on both sides.

The single union ball valve is usually used on the end of a pipeline (for example, a scour line). A double union ball valve is more often used in the middle of a pipeline as the whole valve body can be removed for inspection.

What Advantages Does a Ball Valve Have over a Gate Valve?

A ball valve is generally more compact than a gate valve and will operate at a higher pressure. The ball valve also has a full-bore flow without any steps, whereas a gate valve typically has areas where debris can collect. However, a gate valve gives better control of flow rates.

What Advantages Does a Ball Valve Have over a Butterfly Valve?

A ball valve is generally cheaper than a butterfly valve and also has a smaller footprint. Butterfly valves rely on a disc in the middle of the flow which, as well as increasing friction loss, can also catch debris and foul easily. Generally, people prefer ball valves up to 90mm/3″ and butterfly valves above that.

4 Important Things About Ball Valves

 

  1. Ball valves only turn through 90 degrees, which can make it difficult to accurately control flow rates.
  2. Double union ball valves allow the body to be removed for servicing, while single union valves do not.
  3. A ball valve has a full-bore flow when open.
  4. Ball valves are the least likely valve type to block or foul.
  5. Ball valves are the cheapest option for small, reliable plastic valves for pressure pipe systems.

Post time: Mar-21-2022