Y-Strainers are devices for mechanically removing solids from flowing liquids or gases by means of a perforated or wire mesh straining element. They are used in pipelines to protect equipment such as pumps, meters, control valves, steam traps and regulators.
Although there are occasional exceptions, the use of Y-strainers generally follows several rules. First, they are ordinarily employed where the amount of material to be removed is small. Size for size, their dirt holding capacity is less than a basket strainer. Next, Y-strainers are usually installed when frequent clean-out is not needed. There are Y-strainers in service on steam lines, for example, that are not cleaned more than once a year. Generally, Y-strainers are used with gases such as steam or air. Basket strainers are used with liquids.
For handling steam, a Y-Strainer is the standard and is almost universally used. Its compact, cylindrical shape is very strong and can handle high pressures. It is, literally, a pressure vessel. Y-strainers which handle pressures up to 6,000 psi are not uncommon. Of course, in these cases, safety is very important and Y-strainers, if properly designed, can be used at these pressures without fear of failure. When high pressure steam is being handled, another complicating factor arises – temperature. With steam pressures of 1500 psi or higher, standard carbon steel is sometimes not suitable because the steam temperature may be 1000 degrees F or even higher. In these cases, the Y-strainer body is generally made of chrome-moly steel.
Besides steam, the other gases most commonly used and requiring strainers are air and natural gas. Here again, high pressures are not uncommon. However, unlike steam, high air pressure does not automatically mean high temperature and so ordinary carbon steel bodies of sufficient wall thickness will generally suffice.
A Y-strainer has the advantage of being able to be installed in either a horizontal or vertical position. Obviously, in both cases, the screening element must be on the “down side” of the strainer body so the entrapped material can properly collect in it.
Size of size, a Y-strainer will offer more pressure drop than a basket strainer since its free straining area is less. This is why basket strainers are preferred for liquids. Gases, being readily compressible, will flow through Y-strainers of the same size as a pipeline easily, with little pressure loss. This is assuming the Y-strainer is properly designed and of adequate size. Some manufactures reduce the size of the Y-strainer body to save material and to cut costs. Before installing a Y-strainer, be sure it is large enough to properly handle the flow. A low priced strainer may be an indication of an undersized unit.