Conical Temporary Strainer

Size: Custom-fitted to pipe inside diameter — manufactured to match specific pipe ID. Common range covers 2" - 24" pipe sizes.

Pressure: Class 150 - 300 / PN 10-40 (temporary service only — not rated for permanent installation. Design pressure matches line pressure for startup/commissioning period only)

Standard: No industry standard governs temporary strainer geometry — project-specific fabrication items per project piping specifications. MSS SP-89 covers permanent strainers only.

Body Materials: A240 304 (stainless 304 plate), A240 316 (stainless 316 plate). No cast body — fabricated from rolled plate.

Straining Element: Perforated cone surface. Perforation 1mm - 6mm, mesh lining optional (20 - 100 mesh). The cone shape is the straining element — flow passes through perforated cone wall from outside to inside.

Design: Cone-shaped perforated screen installed between pipeline flanges during commissioning. Apex points downstream. Removed after 2-4 weeks when initial debris is cleared. Flange-mounted or welded-tab installation.

What's Inside a New Pipeline

Every new piping system has debris inside it. No matter how carefully the construction crew works — welding, cutting, grinding, fitting — the inside of a newly assembled pipe system contains material that shouldn't be there. Welding slag drops inside the pipe from root-pass welding. Cutting chips from pipe preparation with saws or grinding tools. Gasket fragments from alignment and bolting. Dirt and dust that entered during storage and handling. Rust scale forming on carbon steel pipe surfaces during the weeks or months between fabrication and commissioning.

This debris load during startup is ten to a hundred times heavier than the normal operating debris that permanent strainers handle. Permanent strainers — basket strainers, Y-strainers, duplex strainers — have screens sized for ongoing operational conditions. Sand particles, corrosion products, biological growth, process contaminants. Those screens run at 0.5mm perforation or 40-mesh lining or finer. If you put that fine screen into a line during startup, it clogs in hours. Sometimes in minutes. The startup debris is larger, more varied, and far more abundant than anything the permanent strainer was designed to catch.

Conical temporary strainers exist to handle this startup load. Larger perforations — 1mm to 6mm — pass the volume of startup debris without immediate clogging while still catching the big pieces that damage downstream equipment. Welding slag, cutting chips, gasket fragments, large rust flakes. The cone strainer catches what matters during commissioning and lets the smaller particles pass through to be flushed or handled by the permanent strainer once it's installed after startup.

Why a Cone, Not a Flat Screen

The cone shape does two things that a flat screen can't.

Surface area. A cone sitting inside a pipe has more perforated surface than a flat disc at the same pipe diameter — roughly 1.5 to 2 times more depending on cone length. More surface area means more open area for flow to pass through. More open area means lower pressure drop per unit of debris collected on the surface. During startup, when debris loading is heavy and continuous, that extra surface area keeps the strainer functional longer before it needs cleaning or removal. Flat screens load up fast because all the debris collects on a small surface and blocks the perforations quickly.

Flow distribution. The cone shape spreads incoming flow across the perforated surface. Flow enters from upstream, hits the cone apex first, and spreads outward along the cone wall toward the base. The velocity distributes across the full cone surface rather than concentrating at the center. Flat screens create a different flow pattern — the highest velocity core stream hits the screen center and debris loads there first while the outer edges see lower velocity and slower loading. Localized clogging at the center blocks a disproportionate share of the open area. The cone shape avoids this concentration effect by geometry alone.

Temporary Means Temporary

Conical temporary strainers are not permanent piping components. The perforation sizes are too coarse for ongoing operational straining — 1mm to 6mm perforation won't catch the fine particles that your permanent strainer handles. The fabricated plate construction — rolled and welded perforated sheet — doesn't have the structural durability for years of continuous pressure service. Cast strainer bodies with machined seating surfaces and rated cover assemblies are built for permanent installation. Conical temporary strainers are built for a commissioning window.

After two to four weeks of service, pull the conical strainer out of the line. Open the flange joint, remove the strainer and its gaskets, inspect the pipe interior for remaining debris. If the system is clean — no visible welding slag, no cutting chips, no gasket material — install the permanent strainer or run the line unstrained per project specification. If debris is still present, extend the temporary strainer service period and keep monitoring. Don't leave a conical temporary strainer in the line indefinitely. It's a startup tool, not an operating component.

Match the perforation to the debris you need to catch, not to the final operating filtration requirement. Startup debris — welding slag, cutting chips, gasket pieces — is typically 2mm and larger. A 3mm perforation catches these while allowing smaller particles to pass for flushing downstream. If your downstream equipment is sensitive to particles above 1mm, use 1mm perforation on the cone and accept that it will clog faster during startup — you'll need to monitor and clean it more frequently during the commissioning period.

Optional. Mesh lining (20-100 mesh) adds finer filtration on top of the perforated cone surface. Use it when your downstream equipment needs protection from smaller particles during startup and you can't wait for the permanent strainer installation. Mesh lining reduces open area and increases clogging rate — the cone loads up faster and needs more frequent inspection during commissioning. For most startup applications, perforated cone surface without mesh lining is adequate because the permanent strainer handles fine filtration after the temporary strainer is removed.

Flange-mounted: the conical strainer sits between two pipeline flanges with a gasket on each side. The flange bolts compress the strainer and gaskets together. This is the standard installation method — easy to inspect, easy to remove, no welding required. Welded-tab: the strainer has small tabs that are welded to one flange face to hold position during service. After commissioning, you cut the tabs off and remove the strainer. Welded-tab installation prevents the strainer from shifting or blowing out under high flow conditions, but it requires welding during installation and cutting during removal. Most projects use flange-mounted installation unless the flow conditions or safety review specifically require welded retention.

Sometimes. Inspect the perforated surface for damage, deformation, or corrosion after removal. If the cone is intact — no crushed perforations, no weld cracks, no material degradation — clean it and store it for reuse on a similar-size line. But conical strainers are custom-fitted to specific pipe IDs, so reuse only works if the next project has the same pipe diameter and flange dimensions. Many projects treat conical temporary strainers as single-use items because the fabrication cost is low relative to the inspection, cleaning, and size-matching effort required for reuse.

Two to four weeks for most installations. Monitor pressure differential across the cone during commissioning — if the differential stays low and stable after the first week, the debris load is clearing. After two weeks with stable DP, schedule removal and inspection. If the differential continues climbing after two weeks, the system still has significant debris and the cone should stay in longer. Don't extend beyond four weeks without engineering review — the temporary strainer isn't designed for extended service, and a loaded cone at elevated DP is a flow restriction that affects system performance.