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Y  STRAINERS

Y StrainersFlow path through a Y strainer

Y strainers provide an economical method of removing undesirable solids from liquid and gaseous pipelines.  Y strainers are designed for protection of equipment downstream, presumably when the percentages of solids are low and the need for cleaning is infrequent.  You should consider a basket strainer for applications which require continuous removal of particles from liquid pipelines.

Y strainers can be installed for flow paths horizontal and vertically downwards and are available in a wide variety of materials, including iron, steel, 316SS, bronze, PVC, CPVC, polypropylene, PTFE and PVDF.

Common connection types include ANSI flanged, threaded, socket weld and ring-joint.  The internal screens are typically 304SS, 316SS, monel, PVC, CPVC or Tefzel.

Like basket and duplex strainers, NOT ALL Y STRAINERS ARE THE SAME.  While they may look virtually the same and may have the same size and connection type, that does not mean their internal geometry, most importantly their flow coefficient value (Cv), is also the same.  You will also find other subtle design differences between brands, for example, some models have differential pressure taps to make it easier to incorporate a differential pressure gauge into your system.  Another common difference is the access to the screen, some are screwed and others are flanged.   Usually lower price is reflected in a strainer body which is either physically smaller or has thinner walls; comparing the weight of different Y strainer models is relatively easy to do.

Y strainers are almost exclusively a cast or molded product and seldom fabricated; it is easier to fabricate a T (tee) strainer then Y strainer and from a fabricated performance perspective they are equals.  Therefore most customers select a Y strainer based upon its material, size, cost and availability and rarely do they compare features.

Clear PVC Y strainer

Y strainers have a threaded drain port which was initially designed to be used in conjunction with a ball valve to enable "blow-down" of the screen chamber when used in steam applications.  Hard materials such as rust and pipe scale interfere with valves, instrumentation and equipment such as condensate drain traps; such particles being hard do not tend to become embedded within the screen perforation or mesh, so when the drain port is opened, the pressure drop between the process gas (steam) and atmospheric pressure effectively "purges" material sitting within the screen chamber.  Opening a valve is much quicker and easier than shutting down the process  and unscrewing or unbolting the screen chamber cover.

Y strainer with blow down valve

This "blow-down" feature has been adapted to some liquid applications, usually water applications due to the loss of fluid during blow-down.  It is important to consider the nature of the particles being retained; if they are organic and deformable, they may become embedded within the screen material reducing the effectiveness of "blow-down" cleaning.  It is also possible to use a timer or PLC to actuate a drain valve when a degree of automation is desired.

We can modify some cast and fabricated basket strainer designs to have bottomless baskets to support "blow-down flushing"; the advantage of using a basket strainer is that they typically require less frequent cleaning.

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