Strainers are used in piping systems to protect equipment sensitive to dirt and other particles that may be carried by the fluid. During system start-up and flushing, strainers may be placed upstream of pumps to protect them from construction debris that may have been left in the pipe.
Figure A2.9 depicts a typical start up strainer. Permanent strainers may be installed upstream of control valves, traps, and instruments to protect them from corrosion products that may become dis- lodged and carried throughout the piping system.
Strainers are available in a variety of styles, including wye and basket.
The wye strainer (Fig. A2.10) is generally used upstream of traps, control valves, and instruments. The wye strainer resembles a lateral branch fitting with the strainer element installed in the branch. The end of the lateral branch is removable, to permit servicing of the strainer. Also, a blow-off connection may be provided in the end cap to flush the strainer.
Basket strainers (Fig. A2.11) are generally used where high flow capacity is required. The basket strainer is serviced by removing the cover, which yields access to the basket. Basket strainers are also available in a duplex style which consists of two parallel basket strainers and diverting valves, which permit diversion of the flow through one of the strainer elements while the other element is being serviced an essential feature where flow cannot be interrupted.