FULL OUTLET STRAINER DESIGN CONSIDERATIONS

Mer-Made FO Series strainers have been designed to achieve lower pressure losses and higher debris holding capacity. These units have been tested for pressure loss (clean basket). In addition, tests were run using grass clippings as a medium to establish a comparison between “dirty-up” time for our design versus the standard designs being offered by competitors.

Mer-Made FO Series (full outlet) strainers are built with a large outlet area in the basket chamber. Historically, strainers have been required to have a basket total open area that is a multiple of incoming pipe area. A typical code or specification may call for a basket open area to be four times the incoming pipe area. Tests have shown, however, that in many designs very little of the basket area is used before a maximum pressure loss, (say 5 psi) is achieved. The usefulness of the strainer basket is much more dependent on the amount of opening in the chamber that houses the basket. To achieve a significant strainer performance improvement we have increased this area considerably.

To best understand the evolution of our design, refer to the sketches below. A “T” type strainer is frequently offered as “equal” to a Mer-Made FO Series design but these sketches highlight the differences.

NOTE: The Mer-Made has a complete outlet section built onto the basket chamber and this is what allows the greatly improved outlet area.

PRESSURE LOSSES VS. FLOW

PRESSURE LOSSES VS. FLOWTIME

NOTE: A test to establish rate of increase of pressure drop versus debris loading was simulated by adding 50 ml of grass clippings every two minutes to 1000 gpm of flow

FO SERIES STRAINER SPECIFICATIONS

Strainer shall be constructed completely of non-corrodible materials. Body shall be all fiberglass construction incorporating a .100″ corrosion liner on all interior surfaces and flange faces. Liner shall be constructed of one layer of resin-rich “C” veil, followed by two layers of 11/2 oz. fiber glass mat. Structure to be four layers of 11/2 oz. glass mat, impregnated with isophthalic polyester resin.

Inlet and outlet to be flanged connections, flange to be 3/4″ thick drilled to 150# ANSI standard drilling pattern. Lid to be manufactured of clear acrylic to allow unobstructed visual inspection of basket*. Stainless steel toggle bolts are to be built into the top of the strainer body. Fiberglass knobs on these bolts clamp the acrylic cover tightly. Three bolts are immovable while one** bolt drops away after loosening knob. The clear lid shall be grooved to allow it to swing open after dropping one toggle. Lid shall be sealed with an ethylene propylene “O” ring.

Strainer is to be built with an outlet structure to enlarge the opening in the basket chamber. Outlet area of the basket chamber shall be a minimum of four times the area of the inlet pipe. Designs similar to a pipe cross, with the outlet of the basket chamber being a nozzle similar to the inlet, are not acceptable.

Supply a V-wire 316 stainless steel basket with 3/16″ square openings and 62% open area. Supply one spare basket for change-out.

Strainer to be FO Series as manufactured by MER-MADE Filter, Inc.

Option – reducing strainer

Strainer outlet shall reduce to pump suction size by use of a full concentric*** reducing station.

*NOTE: 14″ and larger strainers are built with a fiberglass lid which includes an 8″ diameter clear acrylic view port.

**NOTE: Two bolts drop away on 12″ and larger models.

***NOTE: Eccentric reducing sections also available – specify if so desired.