A pipeline strainer is a protective device installed upstream of sensitive equipment (pumps, compressors, control valves, steam traps, meters) to remove solid particles from the process fluid. Strainers differ from filters in that they use a perforated or woven metal screen (not a replaceable cartridge) and are designed for coarse to medium particle removal.
Strainer Types
| Type | Description | When Used |
|---|
| Y-type | Compact body with angled screen chamber; available in screwed, socket-weld, and flanged ends | Most common type for steam, gas, and liquid lines up to NPS 8; permanent installation |
| T-type (basket) | Vertical screen chamber with removable basket; larger dirt-holding capacity | Large-bore liquid lines (NPS 4 and above); high-debris applications; easier cleaning |
| Temporary cone | Perforated cone inserted between flanges during commissioning | Startup strainers; removed after flushing; protects equipment during initial operation |
| Duplex (twin basket) | Two basket chambers with a diverter valve; allows online switching | Continuous-operation systems where shutdown for cleaning is not acceptable |
Mesh Size Selection
The screen mesh size determines the smallest particle that the strainer will capture. It must be selected based on the downstream equipment’s tolerance.
| Downstream Equipment | Recommended Mesh Size | Perforation/Opening Size |
|---|
| Control valves | 40-60 mesh | 0.25-0.40 mm |
| Steam traps | 20-40 mesh | 0.40-0.85 mm |
| Pumps (centrifugal) | 10-20 mesh | 0.85-2.0 mm |
| Flowmeters/instruments | 60-100 mesh | 0.15-0.25 mm |
| General pipeline protection | 10-20 mesh | 0.85-2.0 mm |
Sizing Considerations
| Parameter | Guideline |
|---|
| Line size | Strainer body size matches pipeline nominal size; never undersize |
| Pressure drop (clean) | Y-type: 0.1-0.5 psi; basket: 0.3-1.0 psi at rated flow (clean screen) |
| Pressure drop (dirty) | Monitor differential pressure; clean or replace screen when DP exceeds 5-10 psi (or per manufacturer) |
| Screen open area | Minimum 3x to 4x the cross-sectional area of the inlet pipe for adequate flow capacity |
| Pressure rating | Must match or exceed the piping class rating (e.g., Class 150, 300, 600) |
| Material | Body and screen material per piping specification; screen is typically 304 or 316 stainless steel |
Installation Procedure
| Step | Activity | Notes |
|---|
| 1 | Verify strainer type, size, rating, and mesh against the piping specification | Cross-check P&ID and valve/instrument data sheets |
| 2 | Confirm flow direction arrow on the body | Arrow must match process flow direction |
| 3 | Orient screen chamber downward (Y-type) or vertically downward (basket) | Allows gravity to collect debris away from the flow path |
| 4 | Install blowdown valve at the bottom of the screen chamber | Allows periodic online blowdown without removing the screen |
| 5 | Ensure adequate clearance for screen removal | Y-type: clearance equal to body length below the strainer; basket: vertical clearance above the bonnet |
| 6 | Install isolation valves upstream and downstream | Allows strainer maintenance without full system shutdown |
| 7 | Install differential pressure gauge or transmitter across the strainer | Monitors screen fouling in real time |
| 8 | Perform hydrostatic test with the strainer installed | Verify body and flange joint integrity |
Strainer installation and screen condition are verified during piping inspections and pre-commissioning line checks to confirm correct orientation, mesh size, and cleanliness before system startup.
Read the full guide to piping inspections
Leave a Comment
Have a question or feedback? Send us a message.