Maintenance & Reliability · SOP

Strainer Selection Guideline

This standard operating procedure provides a systematic method for selecting the correct pipeline strainer — Y-type, basket, or duplex — based on process fluid properties, pipe size, pressure class, and operational requirements. Proper selection prevents premature screen blinding, reduces unplanned maintenance, and ensures reliable system protection.

Estimated Time

30 min

Difficulty

Intermediate

Regulation

ASME B16.5 / B31.3

Version

1.0

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Purpose

To define a standardized, repeatable engineering workflow for selecting pipeline strainers that protect downstream equipment (pumps, valves, heat exchangers) from solid particulate contamination. This guideline ensures consistent sizing, material compatibility, and pressure drop management across all industrial fluid and gas applications, reducing procurement errors and premature strainer failures.

Scope

This SOP applies to the selection of inline process strainers for liquid and gas systems in industrial, chemical, oil & gas, and food processing facilities. It covers Y-type strainers, basket strainers (single and duplex), and temporary conical strainers. Excluded: suction line strainers (pump protection), automatic self-cleaning strainers, and filtration skid packages that require detailed process simulation.

Safety Precautions

LOTODepressurize and lock out the line segment before any strainer removal or inspection. Confirm zero energy state with a test gauge.
PPEWear chemical‑resistant gloves, safety glasses, and appropriate footwear when handling screens or opening strainer housings. Use face shield if line contains aggressive chemicals.
TEMPSCheck for thermal burns — strainers handling steam or hot process fluids must be allowed to cool to below 60 °C before disassembly.
PRESNever exceed the pressure rating of the strainer body (marked per ASME B16.34). Verify flange class compatibility before installation.

Required Tools & Materials

Piping & instrumentation diagram (P&ID) for the relevant line
Process fluid data sheet (temperature, viscosity, solids type & concentration)
Pipe schedule/dimension reference (ASME B36.10 for carbon steel)
Flange class & facing information (ASME B16.5, 150# – 2500#)
Strainer manufacturer catalog with pressure drop curves and mesh specifications
Caliper or tape measure for verifying mating dimensions on existing lines
Pressure drop calculator (spreadsheet or mobile app)
Material compatibility chart (e.g., NACE MR0175 / ISO 15156 for sour service)
Flange bolt torque table (based on gasket type and class)

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Procedure: Step-by-Step

1Define duty conditions. Gather operating pressure (max/min), temperature, flow rate (normal/maximum), fluid phase (liquid/gas), viscosity at operating temperature, solids type (scale, weld slag, debris) and concentration. Record required filtration fineness (micron or mesh number).

2Determine pipe & connection specifications. Note pipe nominal size, schedule, and material. Identify flange class and facing (RF, FF, RTJ). Verify end connections — flanged, threaded, or welded. For existing lines, measure face-to-face distance and bolt pattern.

3Select strainer body type. Use Y-type for horizontal or vertical down-flow lines with moderate dirt loads; basket for high dirt-holding capacity (e.g., start-up debris); duplex for continuous processes where cleaning without shutdown is required. Consider space constraints for basket removal.

4Choose mesh or perforation size. Match screen opening to the smallest particle that must be stopped. Common meshes: 20 (1000 µm), 40 (400 µm), 60 (250 µm), 100 (150 µm). Avoid unnecessarily fine mesh to prevent rapid blinding. Reference manufacturer's open-area ratio.

5Verify material compatibility. Confirm strainer body, screen, gasket, and fasteners are compatible with fluid, temperature, and any corrosive or sour components. Typical materials: cast carbon steel, cast stainless steel (CF8M), duplex, or Hastelloy. Check NACE MR0175 if H₂S present.

6Calculate clean pressure drop. Use manufacturer's chart for the selected body size, mesh, and flow rate. For liquids, target ΔP ≤ 0.5 psi (3.4 kPa); for gases, ≤ 1–2% of line pressure. If ΔP exceeds these values, increase body size or use a larger screen area (e.g., basket strainer).

7Evaluate blow-down / drain requirements. For Y-type, ensure blow-down port connection (typically NPT) matches drain line. For basket strainers, confirm clearance for vent and drain valves. For duplex, verify that the switching valve handle does not interfere with adjacent equipment.

8Document selection and create requisition. Complete a strainer specification sheet including: tag number, duty conditions, body type, screen mesh/material, pressure rating, end connections, applicable codes (ASME B16.5, CRN registration number), and a note if custom screen is required. Submit for engineering approval.

Strainer Selection Guideline

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