Y Strainer vs Basket Strainer Design

Differences Between Y and Basket Style Strainers

Download the Y vs Basket Strainer Comparison PDF

Both Y and basket style strainers require isolating the strainer’s inlet and outlet to physically clean the straining element (thus interrupting the process flow). However, there are significant functional differences that, depending upon specific application characteristics, will determine whether a Y or basket style strainer is the best choice for your application.

Y Strainers

Although Y strainers are applied to liquid applications regularly, they were initially designed for steam, air and other inert gases to protect downstream equipment from a “particulate upset condition.” Normally particles are not expected; however, as piping systems age, bits of pipe scale, gaskets and other materials can become entrained in the process flow. Y strainers have a blow-down port for this reason. Bits of pipe scale can be flushed from the screen chamber by attaching a valve to this port and opening it to atmospheric pressure so the material within the screen chamber is flushed through the valve.

 

The key takeaway about the design of a Y strainer is that it is intended to protect downstream equipment from material that is not continuously present in the process flow. In other words, the percentage of particles to be removed from the process fluid should be relatively low if you are going to use a Y strainer.

 

There is nothing wrong with using a Y strainer for liquid applications. In fact, Y strainers have several advantages:

• They can be installed horizontally or vertically downward. Basket style strainers can only be installed horizontally.
• They are more compact and thus less expensive than basket style strainers.
• Standard Y strainers have higher operating pressure ranges than basket style strainers.

Perhaps the most significant downside of a Y strainer when compared to a basket strainer is the open area ratio (OAR). The open area ratio is the ratio of the cross-sectional area of the inlet/outlet port compared to the open area of the element.

 

A straining element is either perforated or has a perforated substrate with a mesh lining for finer retention. Generally speaking, the finer the retention, the less open area the straining element has. The percentage of open area combined with the flow coefficient (C_V) of the strainer itself (design dependent) will determine the pressure drop across the strainer for a given flow rate. The higher the C_V, the lower the pressure drop across the strainer body; the open area of the straining element will determine how much more the initial differential pressure will increase.

 

Because Y strainers were not designed to continuously remove particulate, their design (strainer element chamber and element dimensions) typically provides straining ratios of only 1:1, 2:1 and perhaps in some cases 3:1. At best the element has three times the open area compared to the diameter of the inlet/outlet connection.

Basket Style Strainers

The phrase “simplex strainer” has become ubiquitous for basket strainers even though Y, Tee and other variations are also simplex in nature. For clarity we will refer to them as basket strainers.

 

Due to the way the basket element seals in the basket chamber and the location of the drain port, basket strainers are designed to be installed horizontally. Although both Y and basket strainers are offered in cast and fabricated designs, the standard basket strainer design is typically rated for 150# or 300# pressure class applications, whereas Y strainers are commonly rated to 600#–2500# applications.

 

Returning to the open area ratio, the real differentiator is that basket strainers typically have an OAR of 6:1 and sometimes as high as 8:1 — significantly more than a Y strainer. This is why basket strainers are used for applications that have a continuous particle load. An application such as reclaimed cooling tower water, where there is an expectation of particulates that need to be removed all the time, is a better fit for a basket strainer than a Y strainer.

 

The difference in straining ratios is approximately the difference in frequency that the straining element will need to be cleaned. You would therefore expect to clean a Y strainer screen that has a 2:1 OAR about three times as often as you would clean a basket strainer having a 6:1 OAR.

 

Summary

Most liquid filtration applications that are either batch processes or where it is acceptable to interrupt the flow to clean the straining element will be best suited for basket strainers due to their higher open area ratio and physically larger holding capacity. Y strainer applications are typically for inert gases and for liquid applications where the particle loading is very low or only expected during an upset condition.