Sandfång

Sandfång, or sand trap, is a hydraulic device or section integrated into a pipeline, channel, or structure to remove sand and grit from a flow. Its primary purpose is to protect pumps, valves, pipes, and downstream treatment processes from abrasion, clogging, and excessive wear caused by abrasive solids. Sandfångs are commonly used in municipal wastewater and stormwater networks, in water intakes, and in industrial process lines where sediment loads are high.

Operation relies on slowing the flow or creating a quiescent zone so that heavier particles settle to the bottom while the clarified water continues downstream. The design may include baffles, elbows, or a dedicated detention chamber to promote separation. Collected sand and grit accumulate in a bottom hopper or trough and are removed periodically or via automatic desludging devices, sometimes assisted by air scouring to facilitate cleaning.

Placement and design considerations include preventing short-circuiting of flow between inlet and outlet, achieving adequate detention time for the target particle size, and selecting cross-sectional area and flow paths that accommodate expected sediment loads. Materials should resist abrasion, and access for inspection, desludging, and maintenance must be straightforward. In larger networks, sandfångs are often integrated with grit separators or primary sedimentation stages to enhance overall solids removal.

Limitations include the need for regular maintenance to avoid clogging and re-entrainment, limited effectiveness on very fine particles, and potential odor or sediment handling issues if not properly managed. Sandfångs thus form a protective, maintenance-dependent component of sediment control in various water and wastewater systems.