2-Way vs 3-Way Valves: Which Type is Right for You?

Valves play a crucial role in almost all industrial processes. These devices regulate, redirect, or control the flow of liquids or gases by opening, closing, or partially blocking flow passages. There are numerous types of valves, each differing in various ways, including operating principle, configuration, power source, and application.

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The main components of a Baelz control valves are the actuator, plug and spindle, and the valve body. The actuator, which can be either pneumatic or electric, controls the valve plug by moving it up or down in varying strokes.

2 way and 3 way valve classifications are commonly used in industrial applications. These valves are defined by the number of ports they use. 2 way valves, as their name suggests, consist of two ports: an inlet port &#;A&#; and an outlet port &#;AB.&#; On the other hand, 3 way valves consist of three ports: &#;A,&#; &#;B,&#; and &#;AB&#;.

Since these valves support different flow rates, temperature ranges and pressures, it is important to understand their differences before determining which type of valve is appropriate for your application.

A Guide to Selecting Control Valves for Your Project

2 Way Valve Operation

When fluid enters the inlet (port A) of a 2 way valve, the relative position of the plug dictates the amount of fluid allowed to leave the outlet (port AB). When the plug and spindle are positioned all the way up, the valve is fully closed from ports A to AB. Conversely, when the plug and spindle are fully down, the valve is open from A to AB. The B port is fully capped off with a blind flange on all Baelz 2 way valves. Percise plug positions will control the flow rate through the valve. 

2 way valves are commonly found in basic on/off applications, where they are frequently referred to as isolation valves. These valves are an essential component in many process safety systems, as they can immediately stop fluid flow to a specific location in the event of an emergency.

2 way valves can also be used in variable flow systems that experience changes in pressure, temperature, and flow. For instance, these valves can regulate operating temperatures by using sensors to adjust to specific fluid parameters to maintain the desired temperatures and flow.

For some chilled or hot water applications, 2 way valves are also an ideal solution. Plug and spindle valve positions can be adjusted to ensure that the system in question operates within the optimum efficiency range (typically when the valve is 30-80% open). Functioning within this range prevents equipment damage and also extends the valve&#;s life.

When used correctly, 2 way valves can increase process efficiencies and lower operating costs by providing operators with the ability to run heating and cooling systems at variable flow rates. 2 way valves are used in almost every industry application that requires the regulation of process fluids. This includes the automotive, wood, chemical, food and beverage, power generation, marine, and water treatment/wastewater industries.

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3 Way Valve Operation

3 way valves contain the same components as 2 way valves. What differentiates it from the 2 way valve is the use of an additional port. Like 2 way valves, 3 way valve assemblies can also be controlled by pneumatic or electric actuators.

These valves can be used to either divert the flow of fluids, or to mix fluids from two inlets delivered through to a single outlet. When used as mixing valves, fluids from inlet port A and B are mixed inside the valve body and subsequently transmitted out through port AB. 

Mixing allows for the combination of fluids with varying temperatures and pressures to be combined sent through an outlet with specific desired properties.

When used as diverting valves, port AB functions as the inlet, while Ports A and B function as the outlets. When the plug and spindle are 100% in the upward position, Port A is blocked, thus allowing flow only from AB to B. When the plug and spindle are 100% in the downward position, flow through Port B is blocked, and flow is only permitted from AB to A.

3 way valves are more cost-effective for diverting and mixing applications than utilizing multiple 2 way valves. The ability to mix fluids from more than one inlet makes 3 way valves ideal for heating and cooling various media such as water, oils, and chemicals. These valves are also commonly used as bypass valves in primary and secondary loop applications. Similar to 2 way valves, 3 ways valves are also used in the same process industries previously mentioned.

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2 Way & 3 Way Valves

Baelz&#;s 2 way valves and 3 way valves are constructed from specially selected materials to ensure maximum durability and reliability. For instance, our stainless steel bellows supports movement up to 120,000 up and down reps at a maximum temperature of 350°C / 662°F. Our valves are able to support this type of performance due to a durable and high-end stuffing box which supports the life of the spindle and bellows. 

As an industry leader and premier distributor for North America, Baelz NA also offers an expansive catalog of parts and components for an expansive range of valve solutions.

If you would like to know more about our 2 way or 3 way valve systems, contact our technical team or request a quote today.

Automatic control valves, much like everything else we purchase these days, are not all created equal. Some fall into the high quality bracket with pricing to match, while others hover closer to the lower quality and price sensitive end of the scale. Unfortunately, when evaluating control valve prices, it is not always clear what you are being offered and what standards the valve actually meets. Here are a few questions to consider and ask the supplier to ensure you get years of trouble free operation that lasts longer than it takes the sales person to drive out of your parking lot!

Q 1 What materials are being used?

Make sure you know what the different components of the valve are made of, as this will certainly affect the life of your valve, specifically:

Body Material &#; is the valve body cast iron or ductile iron? Traditionally valves were cast iron but ductile iron has become the new standard due to its superior physical properties that are much better at weathering the elements.

Body Coating &#; Most of the world insists on fusion bonded coating of a valve, inside and out. Unfortunately here in North America, that is not always requested. This just makes common sense for valves that are constantly wet and sit in locations that are not always dry and pristine. A valve should last for many years, so insisting on a coated valve is a wise choice.

Seat Material &#; bronze is typically the common material for seats but over time, depending on water quality and velocities, bronze wears resulting in the need for replacement. This is time consuming and expensive as seat replacement requires a complete disassembly of the entire valve. Ideally go for stainless steel.

Valve Internals &#; Most valve manufacturers utilize stainless steel for their valve stems. Make sure that you ask what grade of stainless you are getting as not all stainless steel is created equal. 316 SS is always the best choice because it is harder and least likely to corrode.

External Fasteners &#; Over time valves experience condensation or flooding and this can play havoc with coated studs or bolts. There is nothing worse than trying to remove heavily rusted studs out of an old valve to perform maintenance. Request stainless steel fasteners as this will ensure that bolts will be removable at any age.

Q 2 Does the valve supplier fully understand your application?

Too frequently a specification will be requested and a valve is supplied that is simply the wrong valve for the job. It may also be the case that there is just a better solution. Ensure you give your valve supplier all the necessary pressure and flow details including details of the actual application and what you want this valve to do. Having the wrong valve for the wrong application, at best case will result in a significantly shorter life and worst case, a malfunction that can result in destruction of the valve and other parts of your water distribution system.

Q 3 Will this new valve fit into my existing piping layout?

Don&#;t be tempted to just stay with brand X because that is the valve you may be replacing and has the same lay lengths. Most manufactures can be quite innovative on providing solutions to combat varying lay lengths so explore all of you options rather than just settling because you think it may be easier.

Q 4 Do you need specialty tools for maintenance?

Nobody wants to have to carry around a specific tool that only performs one task. Ensure that your valve can be maintained with everything you would carry in regular tool kit. Some valve manufacturers require specialized seat removal tools, or vice jaws installed with copper jaws to protect valve stems. While these are great ideas, they are certainly not things that the average operator has in his toolkit.

Q 5 Will your personnel receive complimentary factory qualified training?

Control valves are not so difficult to understand and once taught, most operations personnel can easily perform maintenance. Ensure that you will not be reliant on the additional cost of having to bring out a factory person every time your valve requires maintenance. Request that a factory-trained representative is on site when the valve is commissioned. This will allow your operators to be schooled in the regular maintenance needs, know what to look for if things go awry and how to start up a valve in a new system or after service. Simple tricks like removing air out of the pilot system are valuable lessons to see in practice.

Q 6 Does your valve have a solid warranty?

These days having a product with the long term back up of the factory is important. Three years should be the standard to ensure there are no manufacturing faults.

Q 7 Can I make changes to the valve if required

Having a valve &#;expansion ready&#; for the future can save you money and make your decisions a whole lot easier. For example, can you add a limit switch or a position indicator easily? Or, if you need to move the pilot system to the other side of the valve, can you do it, or is it not possible because the valve body does not have the required connections? Things always change and a flexible valve gives you more options to keep your now perfect valve, perfect down the road.

Q 8 Does your valve meet industry standards?

There are third party accreditations that ensure your valve was built to the correct specifications. For example; NSF 61, WRAS, UL/FM, AWWA, ISO et.al. They are important because they ensure that the valve has been built to a given standard so the user can be assured they meet approval for such things as low lead content, bacterial growth tests, functional tests etc.

Q 9 Do you have local and factory support?

Make sure there is someone in the area that is factory trained and available to come out and assist when you have questions or problems. This sounds like a given but it&#;s best to ensure the local agent will in fact be there for you when you need him. When a valve fails, timing is usually of the essence so you should know whom to call prior to such an event.

Q 10 Is the valve solution offered able to handle future needs?

In the world of &#;low bid wins&#;, a supplier may be tempted to squeeze as small a valve as possible into the application in order to reduce price. Make sure that the offered solution will supply your needs for the foreseeable future without the burden and additional cost of having to change a valve in a couple of years.

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