Flow through three-way ball valves
Two-way and three-way ball valves are the most common types of ball valves. Three-way ball valves are especially useful because they can be set up in ways that simplify the control of gas and fluid flow. For example, they can be used to divert the flow of oil from one tank to another.
Three-way ball valves can
Cut of or shut off flow
Switch flow between two different sources
Combine the flow from two different sources
Alternate flow between two different destinations
Divert flow coming from one source to another destination
Split flow coming from one source between two outgoing destinations
This post focuses on the basic design differences between L-pattern (L-port) flow and T-pattern (T-port) flow in three-way ball valves. I will also describe some of the ways handle position in combination with the range of handle rotation are used to control flow through typical three-way ball valve designs.
The front view of a typical three-way ball valve with a handle that rotates parallel to the valve ports plane. These are also called vertical version, vertical type, vertical ported, upright and upright tee valves.
The front view of another common style of three-way ball valve. It has a handle that rotates at a right angle to the valve ports plane. These are also called vertical version, vertical type, vertical ported, upright and upright tee valves.
How is a three-way ball valve different from a two-way ball valve?
Two-way ball valves are widely used as shut-off valves for gases or liquids (media) moving through closed tube or pipe systems. This is because of their simplicity and reliability. Two-way valves have two ports or openings where pipe or tubing is connected to the valve. The ball in two-way ball valves has a single straight hole through it where the liquid or gas (media) passes through the valve
The flow through a standard port ball valve is somewhat restricted because the bore through the ball inside the valve is smaller than the diameter of the pipes connected to the valve ports. An option for reducing or eliminating flow resistance through a ball valve is to use a full port ball valve.
Learn more about Full Port Ball Valves vs Standard Port ball valves. This blog post describes the differences between full port or full-bore ball valves and standard port valves. It also includes a list of FAQs describing some of the basics of ball valve design.
Three-way ball valves have three ports or connections for pipe. In general, three-way valves can solve more complex flow control needs than two-way valves. This makes them useful for many types of process applications.
For example, one type of three-way ball valve can be used to mix purified water from one source with juice concentrate from another source. A slightly different three-way valve design could divert fuel flowing from one tank to another tank while still being able to shut off the flow of fuel entirely if needed.
When choosing the right three-way ball valve, it is important to both understand the key three-way valve design options and plan how the valves will be used. First, some basics.
What is a three-way ball valve?
Three-, four- and five-way ball valves are called multi-port valves. The three-way ball valve is the most common multi-port ball valve. A three-way ball valve has three ports or openings that are connected to piping or tubing for gas or fluid flow (media) to pass through. These ports are usually described as one inlet and two outlet ports or one outlet and two inlet ports depending upon the flow direction through the valve.
Three-way ball valves are popular because they are an economical and simple way of providing both shut off and flow direction control in a single valve body.
Although this technical blog is aimed at large-bore and high-pressure flow control, it contains some useful and very well illustrated information about three-way ball valve design.
Controlling flow through a three-way valve is done with a combination of how the piping is set up, the handle rotation of the valve ball and the flow path through the valve ball (the ball bore or porting).
Using the right valve type and setup, flow can be controlled in ways that meet one or more different process requirements such as
Shut off flow completely
Mix flow from two different sources
Divert flow from one destination to another
Split flow from one source between two different destinations
Alternately block flow in one direction while allowing flow to continue in another
There is one simple but key internal design difference that determines what a three-way ball valve can do. This important design difference is the pattern of flow or port shape through the ball inside the valve. Most three-way ball valves have valve balls with flow patterns shaped like either a capital L (L-pattern flow, L-flow, L-port, two direction) or a capital T (T-pattern flow, T-flow, T-port, three direction).
I will describe the basics of three-way ball valves with both L-pattern and T-pattern flows, but I will describe L-pattern flow ball valves first. Having a clear understanding of L-pattern flow makes understanding T-pattern flow much easier.
L-pattern valve balls have flow paths shaped like a capital L
Notice that the stem slot for turning this valve ball is on top. This means the ball is made for a horizontal type three-way valve. If it was intended for a vertical type valve, the stem slot would be opposite one of the bore holes (ball flow path ports).
L flow patterns, sometimes called 90-degree balls, are most often used to allow flow from one common inlet port out into one of two different outlet ports. This is why L-pattern flow three-way ball valves are often called diverter valves.
What is a diverter valve?
Diverter, selecting or directional valves are alternate names used for L-pattern flow ball valves. This is because this valve design is widely used to divert or change the flow going out through one of two different valve outlets or ports. Manual three-way L-pattern ball valves used as diverter valves are usually installed with the bottom port of the valve body as the common or flow entry port.
L-pattern flow ball valves with handles that can turn 90 degrees (a quarter turn of the handle) are also called two position valves. They can divert flow either to the left or to the right with one 90-degree turn of the handle.The PMBV series plastic three-way ball valves are typical L-port ball valves designed to be used as diverter valves without a cutoff position.
When their handles are allowed an additional 90-degree turn, 180 degrees total (a half turn of the handle) they can stop flow altogether. These are usually called three position valves.
If the sweep of the handle rotation is not limited by built in valve handle stops, an L-flow pattern ball valve can also be rotated either 270 degrees (a three-quarter turn of the handle) or 360 degrees (a full turn of the handle). This freedom of rotation provides two possible shut-off positions.
With a four-position valve, these two valve shutoff positions are only 90 degrees or a quarter turn apart.
Most horizontal type L pattern flow valves will have handles that are limited to 180 degrees of turn. This provides for three flow options
Cut off or shut off flow
Again, this type of L-pattern flow three-way ball valve is usually described as a three position valve.
Vertical type L-pattern flow three-way ball valves have two possible flow paths and two possible off positions.
For a vertical type L-pattern flow ball valve, the bottom port or common port is always open. Turning the valve handle 180 degrees (a half turn) diverts flow either to the left or to the right (see the previous images). If the valve is rotated only 90 degrees (a quarter turn) in either direction though, the handle faces either the front or the back of the valve. In these handle positions, flow through the valve is cut off.
Many vertical type L-pattern flow valves will have handles that are limited to only turning 180 degrees, a half turn. This provides for all three options: left flow, right flow and one off position.
BVPM Series – Female NPT Ball Valves (spec sheet) from ISM
The BVPM series of vertical type brass miniature valves include three-way ball valves. These three-way valves are typical L-port 180-degree rotation ball valves designed to be used as diverter valves plus one cutoff position.
BLV Series – Female NPT Ball Valves (spec sheet) from ISM
The BLV series of vertical type brass miniature valves include three-way ball valves. These three-way valves are typical L-port 180-degree rotation ball valves designed to be used as diverter valves plus one cutoff position.
PBV3 Series – 3-Way Ball Valves (spec sheet), PBV3 Series 3-Way Ball Valves – Panel Mount (spec sheet) and PBV3L Series – Large 3-Way Ball Valves (spec sheet) from ISM
These vertical type plastic miniature valves are typical L-port 180-degree rotation ball valves designed to be used as diverter valves plus one cutoff position.
Let’s look at horizontal type L-pattern flow in greater detail
In this L-pattern flow horizontal type three-way ball valve, the default handle position allows flow between the common valve port at the bottom and the left valve port.
If the valve handle is turned counterclockwise 90 degrees, the L-flow pattern ball inside the valve also rotates 90 degrees counterclockwise. It then diverts flow to the right instead. Flow now passes between the common or bottom port and the right port.
What are two position L-pattern flow ball valves?
This is where it starts getting a little tricky. A basic L-pattern flow three-way ball valve type (see above) is often limited to only this 90-degree turn of the handle. This very simple three-way ball valve is usually called a two-position valve. It is also called a diverter, selecting or directional valve.
Why do handles matter for three-way ball valves?
Limits on how far a ball valve handle can rotate are provided by handle stops of some sort (red arrows). These are usually extensions of the handle and the top of the valve body. They function by interfering with handle rotation. These stops prevent the handle from turning beyond a set range of motion.
The handle stops built into this valve and its handle (red arrows) interfere with the movement of the valve handle limiting it to a 90-degree turn.
Three position L-pattern flow ball valves
Three position three-way L-flow pattern ball valves are also available. They have a 180-degree limit on the turn of the handle.
In a design like this, the handle position could start with a clear flow path between the bottom port and the left port (position 1). Turning the valve handle 90-degrees counterclockwise to its second position still allows flow through the valve, but this time the flow is between the bottom port and the right port.
Turning the valve an additional 90 degrees counterclockwise, 180 degrees total (position 3), cuts off all flow through the valve. These sort of L-pattern flow ball valves are usually called three-position valves: a starting position, a 90 degree turn and a 180 degree turn.
A 180-degree (three-position), L-pattern, three-way ball valve has two flow paths and one cutoff position.