Basket Strainer Product

Overview

A basket strainer is a coarse pipeline filter: a vessel set in the line whose internal Strainer Basket catches pipe scale, weld slag, gravel, leaves, and process debris before they reach pumps, control valves, spray nozzles, heat exchangers, and flow meters. Unlike a Y-strainer, which packs a small screen into a fitting, the basket strainer is a true vessel with a large-area element and a top Cover Assembly — so it holds far more dirt, drops less pressure, and is cleaned from above without breaking pipe joints. It is the standard protection device on pump suctions in water intake, condenser cooling, fuel-oil, and process service from DN50 to DN600.

Construction

The Strainer Body is a cast iron, carbon steel, or 316 SS Body Casting rated to ANSI Class 150 or 300, with the Inlet Flange arranged to discharge into the open top of the basket and the Outlet Flange drawing from the chamber outside it. Flow therefore passes from inside the basket out through its wall, leaving solids trapped on the inner surface where lifting the basket removes them cleanly. A machined Basket Seat ledge locates the basket rim, and on DN200-plus vessels Support Legs carry the weight to the floor rather than hanging it on the pipe.

The basket itself is a rolled and welded 316 SS Basket Shell with perforations from 0.8 to 12.7 mm chosen for what is being protected — a rule of thumb is holes no larger than half the smallest passage downstream. For finer duty a woven Mesh Liner, 20 to 400 mesh, is spot-welded inside the perforated shell, which then serves as the structural backing. The solid Basket Rim seats on the body ledge over an elastomer Rim Seal so no unfiltered bypass path exists, the reinforced Basket Bottom resists collapse when the element blinds over, and a fold-flat Basket Handle lifts the loaded basket straight up and out. Good practice sizes the basket open area at four or more times the pipe bore, keeping clean pressure drop to 0.03–0.1 bar.

Closure and servicing

Everything about the top end is built for routine opening. The Cover seals on a Cover Gasket — Buna-N, EPDM, or PTFE by service — clamped by hinged Swing Bolt eye bolts that swing clear without removing nuts; smaller units use Hand Knob nuts for tool-free access. Above DN150 the cover gets heavy, so a pivoting Cover Davit carries its weight and swings it aside, with Lifting Lug points for slinging.

The service cycle is: isolate the line, crack the Vent Cock on the Vent Assembly to break vacuum, open the Drain Valve at the bottom Drain Boss to depressurise and empty the sump, release the cover, lift out the basket, dump and wash it, and reassemble. With a spare basket on the shelf the line is back in service in minutes. Where flow cannot stop at all, the same elements are built as a duplex strainer — two baskets with a changeover valve so one chamber strains while the other is cleaned.

Knowing when to clean

As debris accumulates, pressure drop across the basket rises. The Differential Pressure Indication makes this visible: a Pressure Gauge on each side of the element behind Gauge Isolation Valve isolation, or a differential Pressure Sensor transmitter wired to the control system. The working rule is to clean at about 0.7 bar differential; well before the basket's collapse rating of 1.7–3.5 bar. Running a blinded basket is the classic failure — either the basket crushes and dumps its load downstream, or a pump suction strainer starves the pump into cavitation. On critical suctions the differential switch is interlocked to alarm or trip.

Selection notes

Body material follows the fluid (bronze for seawater, 316 SS for chemicals, cast iron for plain water), gasket material follows temperature, and perforation/mesh follows the most sensitive downstream component. Strainers on pump suctions deserve special care: the added pressure drop subtracts directly from NPSH available, so suction baskets are specified coarse and generously oversized. Magnetic inserts catch ferrous fines in lube and fuel systems, and steam-jacketed bodies keep viscous products such as resins and heavy fuel oil flowing through the element.