Temporary strainers are installed between pipe flanges during commissioning and start-up to capture construction debris, weld slag, scale, rust, gasket material, and foreign objects. They protect expensive downstream equipment (pumps, compressors, turbines, control valves) during the critical first hours of operation.
AQ Process Systems sources and exports conical (witch hat), flat plate, and truncated cone temporary strainers for all standard pipe sizes and flange ratings. Strainers are fabricated from stainless steel mesh on a carbon steel or stainless steel frame, with a gasket face matching the pipe flange.
Temporary strainers are designed to be removed after the system is flushed and clean, typically after 72-168 hours of operation. We supply strainers with tell-tale tabs that protrude outside the flange, making it impossible to forget removal during the permanent gasket-up.
| Product | Specification | Description |
|---|---|---|
| Conical Strainers | ||
| Conical (Witch Hat) Strainers | 2", 48" | Class 150-2500 | SS mesh + CS frame | Cone-shaped temporary strainers providing large screen area, the cone protrudes into the downstream pipe. Most common type. |
| Truncated Cone Strainers | 2", 48" | For restricted downstream space | Flat-top cone strainers for applications where the downstream pipe has restrictions (valves, fittings) close to the flange. |
| Flat Strainers | ||
| Flat Plate Strainers | 2", 48" | Class 150-2500 | Between flanges | Flat disc temporary strainers, compact, minimal protrusion. Used where downstream space is very limited or for horizontal installations. |
| Accessories | ||
| Strainer Gaskets | Spiral wound or compressed fibre | Matched to flange | Gaskets sized to accommodate the temporary strainer between flanges, ensuring leak-free installation during start-up. |
| Replacement Screens | SS 304/316 mesh | Various mesh sizes | Replacement screen elements for temporary strainers, pre-formed to fit cone or flat frames. |
Temporary strainers protect downstream equipment during pipeline commissioning and start-up. New piping systems contain weld slag, mill scale, rust, gasket debris, and foreign objects that can damage pumps, compressors, turbines, control valves, and other equipment. The temporary strainer captures this debris during the first hours of operation and is removed once the system is clean.
Conical (witch hat) strainers have 3-5x more screen area than flat strainers of the same pipe size, lower pressure drop and higher debris capacity. However, they protrude into the downstream pipe and need clearance. Flat strainers are compact with minimal protrusion, used where space is limited or as a backup in case the cone contacts downstream fittings.
Typically 72-168 hours of operation, or until the screen is inspected and found clean. Some project specifications require multiple screen inspections, the strainer is removed, inspected, cleaned, and re-installed until consecutive inspections show minimal debris. The strainer must be removed before the system is put into normal operation to avoid pressure drop and potential screen failure.
Standard temporary strainers use perforated plate with 3mm holes or 16-20 mesh (1.0-0.84mm) wire mesh, fine enough to catch weld slag and scale but coarse enough to avoid excessive pressure drop. For turbine and compressor protection, finer mesh (40-60 mesh) may be specified. Consult the equipment manufacturer's start-up requirements.
Yes, strongly recommended. Tell-tale tabs are metal strips that protrude outside the flange joint, making the temporary strainer visible from outside the pipe. This prevents the strainer from being accidentally left in the pipeline permanently, a common and potentially dangerous oversight. Most project specifications require tell-tale tabs.
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