duplex strainers are used for continuous removal of
particulate from liquids or environments that are
aggressive to alloy strainers and are designed to be
installed within non-alloy piping systems.
Duplex strainers are used in applications where the flow cannot be interrupted to clean or replace the strainer basket. The DB series duplex strainers consist of a pair of SB series simplex strainers connected with a pair of linked 3-way valves. The valve assembly diverts the flow from the dirty basket chamber to the clean basket chamber, isolating the dirty basket chamber so that it can be accessed safely for cleaning or replacing the dirty strainer basket. We've written an article: BASKET STRAINERS: Differences between Simplex and Duplex Style Strainers explaining the key differences between simplex and duplex strainers; since these consist of two SB series simplex strainers, reading the overview of plastic simplex strainers will be helpful also.
Our duplex strainers are available in PVC, CPVC and Eastar (clear) materials with the three-way flow diverting valves matching the strainer body material; with exception of the Clear Eastar material where PVC valves are used. The three-way valves used are the TW series as described at our valve website: Three Way Ball Valves.
Both the strainer and valve connections feature the true-union design, simplifying installation and maintenance.
EPDM or FKM elastomers are used for the chamber covers, connections and valve seals.
The standard strainer screen has 1/32" perforations and is made from the same material as the strainer body. Additional perforations are available and may be substituted for no additional cost. it is also possible to order stainless steel screens and mesh lined screens for an additional cost.
One frequently asked question is: Are the strainers schedule 40 or 80? The answer is "neither" because that terminology is used to describe the uniform wall thickness of piping and since these are molded products having varying wall thicknesses, they cannot have a specific "schedule" assigned to them. What you need to refer to is the rated pressure by temperature chart to make sure that your application falls within the limits of the strainer material chosen. Each duplex strainer page has links to the catalog pages and the pressure/temperature charts.
Other significant aspects to consider include:
Never use plastic strainers for compressible fluids such as air or nitrogen.
The maximum fluid velocity should not exceed 5-8 FPS and our sizing calculators use 5 FPS as the design standard.
Your piping system should be independently supported; the strainer is not designed to support piping nor should piping support the strainer. The strainer should be mounted to a firm surface and the piping upstream and downstream of the strainer should be independently supported.
It's critical to review your pressure limitations for your fluid temperature and reduce potential Water Hammer situation accordingly.
If you intend to install a plastic strainer within an alloy piping system it is recommended that you install at least 10 pipe diameters of plastic piping upstream and downstream of the strainer to help account for differences in thermal expansion rates of metal and plastic, transmittal of pipe vibration and pipe loading forces. Connecting plastic strainers directly with metal piping can potentially damage the strainer.
When in-doubt, simply call us or better yet, fill-out our application based inquiry form and we'll assist you with the proper selection.