Full Port Ball Valves vs Standard Port

Full port ball valves provide almost no resistance to flow through the valve

Summary: The flow path through a full port valve body is the same size as the flow coming into the valve and leaving it via its tube or pipe connections. Standard port valves have smaller bodies overall with a corresponding narrowing inside the valve body.

Introduction
Questions about the differences between full port or full bore valves and standard valves come up pretty regularly for us. I am going to try to answer some of them in this post. I’ve included some related information in the form of a short FAQ list. These FAQs should help with some of the technical issues and vocabulary. My intention is to provide a description of the differences between full port and standard port ball valves and an overview of ball valve type miniature valves.

What is a ball valve?
Generally, valves are devices used to control the flow of a gases or liquids through a closed tube or pipe system.  Flow through a valve can be relatively unobstructed when it is completely open. Flow stops when the valve is completely closed.

A ball valve consists of a valve body with a rotatable ball in it. This ball or sphere has a hole or bore through its center. The handle on a ball valve opens the valve when it turns the ball to align with the pipe or tube so that it is pointing the same direction as the pipe. This allows flow to pass through it. The valve handle can also turn the ball so that the bore is at a right angle or 90 degrees to the flow. This closes the ball valve.

Learn more about full port ball valves

Ball valves are tough, durable and reliable. They close securely even after long periods of not being used. These qualities make them an excellent choice for shutoff and control applications. Ball valves are unable to provide fine flow control or throttling. Gate, globe or needle valves are more appropriate for these situations.

What is a full port or full bore ball valve?

• Has a straight flow path
• Offers little or no resistance to flow
• The flow path through the valve does not become narrower on the inside

The inner diameter of the pipe coming into a full bore valve is the same diameter as the flow path through the valve body and out through the other side of the valve. Most full bore valves are two-way, quarter-turn ball valves.

Learn more about ISM’s stainless steel and brass full port ball valve series

• BVSS Series - 2 Way Stainless Steel Ball Valves (full port and standard port)
• SSBV Series - 2 Way Stainless Steel Full Port Ball Valves
• BCV Series Brass Ball Valves

What is a standard port or standard bore ball valve?

• Has a straight flow path
• Flow restriction produces a pressure drop
• The flow path through the valve becomes narrower on the inside

A standard bore valve body is about the same diameter as the pipe or tube coming into and exiting it. The working part of the valve is the ball inside the valve body. Since the working part of the valve fits inside the valve body, the bore through the valve ball is smaller than the diameter of the valve’s connecting pipe or tube.
 

The following are some FAQs related to valve basics, ball valves and selection tips

What are valve ports?
The ports of a valve are generally understood to be the connections that carry the flow of the liquid or gas into the valve and away from it.

Why are so many ball valves the standard port or bore type?

• More compact design
• Easier and less expensive to make

The reason most ball valves use standard bores is that this design is relatively compact. It is not unusual for space limitations to be a factor when choosing a valve. Standard bore valves also require less material to make the valve body. Higher material and manufacturing costs can be significant when the body material used is something like stainless steel or Hastelloy.

What is a quarter-turn valve?

• Ball valves are often called quarter-turn valves
• A quarter turn of the valve handle is enough to fully open or fully close a quarter-turn valve

Multi-turn valves require multiple turns of the handle to fully open or close the valve. Spigots on the outside of houses are a good example of a multi-turn valve.

Why are ball valves used so widely?

• Quick to open and close
• Available in multi-port designs
• Smaller and lighter than gate valves
• Suitable for both clean and silty flow
• They provide bubble-tight flow shut off
• The variety of ball valve designs and materials provides selection flexibility
• Capable of reliable service in both high-pressure and high-temperature applications
• The force needed to close ball valves is less than for same sized gate or globe valves

Ball valves are not well suited for regulating flow. This is because ball valves use a relatively soft ring-shaped valve seat to create a tight seal. When they are partially open, pressure is applied to only a portion of the valve seat. This can cause the valve seat to warp and reduce its ability to provide a good seal causing it to leak.

Another reason ball valves are not a good choice for regulating flow is that they create turbulence and possible cavitation when used this way. Turbulence and cavitation reduce flow rates, increase noise and vibration and can even damage valves and piping.

What is flow turbulence?
Pressure difference across a valve can cause turbulent or irregular flow on the downstream side of the valve.

System conditions and valve design can increase or reduce turbulent flow. Generally, there will always be some turbulent flow on the downstream end of a standard bore ball valve, especially when it is just opening and just closing.

What is cavitation?
Flow creates a pressure difference across a valve. Rapid pressure drop across a valve can cause cavitation. Cavitation is the rapid formation and collapse of vapor bubbles within a liquid. When this happens, the collapse of these tiny vapor bubbles could erode the valve and pipe material around them. This video from the IET Institute for Energy Technology at HSR University of Applied Sciences Rapperswil in Switzerland provides a detailed explanation.

The pressure difference across a valve is greater for a standard bore ball valve than it is for a full bore valve. Full bore ball valves tend to have little or not pressure difference across the valve.

What is valve bore size?
Valve bore size is the size of the hole through the ball, the working part of a ball valve. The difference between a standard and a full bore ball valve is directly related to the size of the ball and its bore. Full port bore sizes are the same as the inner diameters of both the valve ports and the pipe used. Standard port bore size is about the same as the next smaller pipe size.

An example to help make this clearer
The bore in a 3/4-inch size full bore ball valve is 3/4-inch in diameter. The bore in a 3/4-inch size standard bore ball valve is 1/2-inch. This is because the balls in standard bore valves are sized in proportion to their valve bodies and bore sizes. In practice, this makes the bore diameter of a standard 3/4-inch ball valve about the same as the inner diameter of 1/2-inch pipe, the next smaller pipe size.

What is throughput and how is it related to flow?
Fluids and gases flow readily from one place to another with relatively low force. Measuring the flow of gases is a little trickier than measuring liquid flow because gases can be compressed. Generally, though, the flow or throughput of a system is the volume of fluid or gas that can pass through it in a given amount of time.

What is flow coefficient (C_V)?
The flow coefficient or C_V is a measure of the resistance to flow of any given part of a fluid system. It is used to calculate the length of straight pipe equal to the flow resistance created by an elbow or valve or any other component that affects the flow because of friction, turbulence or flow restriction.

A high flow coefficient means a low resistance to flow and a low flow coefficient means high resistance to flow.

A full bore ball valve has a low flow resistance (high flow coefficient), about the same as a straight piece of pipe. This means a full bore ball valve causes very little pressure drop across the valve. The flow path through a standard bore ball valve is narrower with a higher resistance to flow (lower flow coefficient). This resistance to flow causes a larger pressure drop across the valve.

Wikipedia has a concise but dense explanation of flow coefficient. As a plus, it includes the metric system version, flow factor. The more technically minded of us here at ISM are partial towards The Engineering ToolBox version because it includes online calculators for air, gases and classes of steam.

Conclusion
Whew, you made it. Like me, you probably just read the intro and skimmed through the rest. However much you decided to take in on this pass, I hope you come away from this with some useful information. I hope you also find the short FAQ to be a handy reference to come back to. A quick and simple explanation of full port vs standard port ball valves plus an introduction to ball valve design.

ISM is proud of our extensive selection of miniature ball valves, so I invite you to spend some time browsing through the miniature valve section of our catalog. You might be surprised at how wide ranging our ball valve selection is.

About the author

Steven C. Williams, BS, is the technical writer and an inbound marketing specialist at Industrial Specialties Manufacturing (ISM), an ISO 9001-2015 supplier of miniature pneumatic, vacuum and fluid circuitry components to OEM's and distributors all over the world. He writes on technical topics related to miniature pneumatic and fluidic components as well as topics of general interest at ISM.       

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