Wye ('Y') strainers and Pot (aka. Tee or 'T') strainers have many similarities, so how does one decide which style is the best fit for an application?

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Similarities

Y and T strainers are both simplex style pipeline strainers designed for batch applications with a light particle load; to clean the internal screen requires interrupting the process flow.

Y Strainers

Although commonly used for liquid applications, the use of Y type strainers were initially for steam, air and other inert gases to protect downstream equipment from a "particulate upset condition" such as protecting steam condensers from rogue pipe scale.  Y strainers have a blow-down port for steam applications and this flushing capability is a characteristic that T strainers do not have. While blow-down may work for aqueous applications, the efficiency of flushing depends upon the particles retained not becoming embedded within the element.

Although it is possible to fabricate Y strainers to satisfy specific applications, the majority of Y strainers are cast items, thus non-customizable. It is common for Y strainers to be available in 1/4" through 10" sizes and because they are a cast item manufactured in foundry-pour based quantities, shipment is often made within just a day or two after receipt of an order. The available pressure class ranges and breadth of materials of construction (iron, steel, bronze, and 316SS) are also advantages of Y strainers.

The open area ratio (OAR) for Y strainers is typically a little better than T strainers; most of our Y strainers have a 3:1 OAR wheras the larger size T strainers have an OAR of <= 2.

Y strainers have a screwed or bolted chamber cover for screen access and are installed such that when opened the process fluid will fall/drain out.

T strainers are mostly a custom fabricated product, often manufactured from pipe. The advantage of a fabricated product is the ability to provide customized features, such as a quick-opening style cover, addition of a vent port or adding differential pressure taps. It is also possible to off-set the inlet and outlet by 90 degrees, forming an "elbow" shaped strainer which might be desirable when the installation area is constrained.

T strainers usually begin at larger sizes (2") and can be fabricated for 24" or larger pipelines. As a fabricated product, the lead times range from 8-12+ weeks (inclusive of generating approval drawings and manufacturing).

While the OAR for a T strainer is typically less than a comparable size Y strainer, its' flow capacity is higher. This is attributable to the flow path within a T strainer having a "straight-through" design as well as the convoluted element shape.

When installed horizontally, the chamber cover of a T strainer can be opened without the process fluid draining from the chamber; this might be a desirable feature with valuable or hazardous process fluids.

Summary

Y strainers typically offer the best value in terms of initial cost, lead time and overall flexibility which include materials of construction, pressure class, and inherent built-in blow-down port/drain.

T strainers are used when transferring fluids at higher velocities (equates to higher flow rates), for larger pipelines, applications that require special features and for quicker access to the straining element.

 

 

 

Y Strainer - How They Work

Figure 1: Y Strainer

A Y strainer mechanically removes solids and other particles when fluid flows through it. They are essential in numerous fluid control applications to ensure that particles within the fluid do not negatively affect any downstream component. In this article, we will review their design, use cases, how to size the mesh filter, materials, and how to clean them.

Table of contents

 

Why use a Y strainer?

Y strainers are generally necessary for processes that require clean fluids. While clean fluids can help maximize the reliability and lifespan of any mechanical system, they are critical with solenoid valve types because they are very sensitive to dirt. Any solids entering the stream can disrupt and even damage the entire system. In addition to protecting the performance of solenoid valves, they also help safeguard other types of mechanical equipment, including:

• Pumps
• Turbines
• Spray nozzles
• Heat exchangers
• Condensers
• Steam traps
• Meters

A simple Y strainer can keep these components, which are some of the most valuable and expensive parts of the pipeline, protected from the presence of pipe scale, rust, sediment or any other kind of debris. Y strainers, also referred to as wye strainers, are available in various designs and connection types.

Y strainer design

As its name implies, a Y strainer is shaped like a Y and is used to filter or strain out particulates from steam, gas, or liquid. This mechanical straining process is possible because of a filter element composed of mesh, perforated metal, or a wedge wire straining element. The most common kind of straining element is a wire mesh. Some also include blow-off valves that make the cleaning process easier in applications with more substantial dirt.

Sizing the mesh filter for a Y strainer

A Y strainer cannot function properly without a properly sized mesh filter. There are two terms that describe the size of the openings in the strainer through which debris passes. One is micron and the other is mesh size. Though these are two different measurements, they describe the same thing.

What is a micron?

A micron (micrometer) is a unit of length that's used to measure tiny particles. For scale, a micrometer is one thousandth of a millimeter or about one 25-thousandths of an inch.

What is mesh size?

A strainers mesh size indicates how many openings there are in the mesh across one linear inch. The ratings typically range from a size 3 mesh screen with 6,730 microns to a size 400 mesh screen with 37 microns.

Micron-to-mesh conversion chart

Table 1 is a handy resource to help convert from mesh to micron (or vice-versa).

See also:
What is the Advantage and Disadvantage of control valves

For more information, please visit DIN Y Type Strainer.

Table 1: Converting between micron and mesh size

Mesh Size Microns Millimeters Inches 10 2.000 0. 12 1.680 0. 14 1.410 0. 16 1.190 0. 18 1.000 0. 20 841 0.841 0. 25 707 0.707 0.028 30 595 0.595 0. 35 500 0.500 0. 40 420 0.420 0. 45 354 0.354 0. 50 297 0.297 0. 60 250 0.250 0. 70 210 0.210 0. 80 177 0.177 0.007 100 149 0.149 0. 120 125 0.125 0. 140 105 0.105 0. 170 88 0.088 0. 200 74 0.074 0. 230 63 0.063 0. 270 53 0.053 0. 325 44 0.044 0. 400 37 0.037 0. 500 25 0.025 0. 625 20 0.020 0. 10 0.010 0. 8 0.008 0. 5 0.005 0. 2.5 0. 0. 1 0.001 0.

In addition, it can be helpful to see examples of the mesh sizes of certain particles, as shown in Table 2.

Table 2: Mesh sizes of particular particles

Mesh Size Microns Example of particle size 14 0. - 28 0. Beach Sand 60 0. Fine Sand 100 0. - 200 0. Portland Cement 325 0. Silt 400 0. Plant Pollen

Determining proper filter size

It's important to take the time to size the mesh filter correctly. A mesh filter that is too small or too large can negatively affect the system. If the filter is too small, there will be a higher pressure drop from inlet to outlet. Additionally, removing too much debris from the flow can clog the filter and increase the pressure drop. If the filter is too large, the performance and life span of the downstream equipment can be negatively effected.

Material options

There are various material options for the strainer's housing and seal. The variety of housing materials fit well with certain environments and media. The seal helps to extend the life of the strainer.

Housing materials

• Brass
• Stainless steel
• (Carbon) steel
• Bronze
• Cast iron
• Ductile iron
• Plastics

Seal materials

• PTFE: Very common seal material. Handles aggressive environments and low and high temperatures.
• Fluoro rubber: There are a few different seal materials that have a fluoro rubber base: FKM, FPM, and Viton. These seals are noted for their resistance to chemicals and weathering.
• EPDM: EPDM is similar to fluoro rubber but has different chemical resistances and working temperatures ranges. Learn more in our chemical resistance of materials guide.

How to install a Y strainer

Before installing a Y strainer, ensure the following:

• The strainer's pressure rating is suitable for the intended application.
• A Y strainer is a one-way strainer, so ensure the arrow that indicates flow direction will be pointing in the right direction.
• The Y strainer can be installed vertically or horizontally, but the filter leg must be pointing downwards to ensure that any filtered material does note interfere with the main flow.
• There must be enough space around the filter leg to open it and clean the inside.

When installing a Y strainer:

• The strainer should go in front of any equipment it is meant to protect.
• The pipes that the strainer will connect to should be supported.
• Finally, review the strainer's manufacturer's manual to determine if any other special considerations need to be planned

How to clean a Y strainer

The necessary frequency for cleaning the Y strainer depends on the process, mesh size, and materials being filtered. Close off any valve connections to both sides of the strainer, loosen the plug at the end of the filter leg, and empty the collected material from the filter.

Y strainer selection criteria

There are different kinds of Y strainers on the market designed to meet various industry needs. Keep the following criteria in mind:

• Port size
• Filter size
• Housing and filter materials
• The temperature in the environment
• The pressure level in the environment
• Preferred installation orientation
• The kind of debris in the system
• Ease of maintenance

There is no one-size-fits-all Y strainer that meets every need. That's why it's important to understand the application requirements before selecting a strainer.

Typical Y strainer applications

A Y strainer is most valuable in an environment that requires constant protection from debris and contamination. Some of the most common applications are the following.

Steam applications

These strainers are a go-to resource in most steam applications, as their shape is built to handle the high pressure that exists in these environments.

Liquid applications

Liquid applications tend to become infiltrated by sand and gravel, and Y strainers can help keep those particles out to ensure the liquid stays clean. Especially when they work in tandem with other water-handling applications, these strainers can protect important (and expensive) equipment from damage, corrosion, or clogs that could result from such contamination.

Natural gas and air applications

Natural gas and air applications tend to have a low operating pressure, so proper sizing to reduce a pressure drop from inlet to outlet is important.

FAQs

How should I install my strainer?

Y strainers have an arrow from inlet to outlet. It is important to install them in this orientation for proper filtration.

What kind of end connections are available?

Depending on your needs, Y filters can include a variety of end connections, including flanged, threaded and welded. You can also find special flanges, such as ring joints.

What kind of housing material should I choose?

Select the housing material based on the application's environment. To do this, it's necessary to understand the chemical resistances of the materials.

Are Y strainers affordable?

A Y strainer is an affordable alternative to other types of strainers, especially at small sizes.

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