Paddle Trimming Calculator
Enter process and sensor parameters below. Product suitability is determined by the calculated equivalent drag force (gf) and indicated by colour-coded status in the Answer panel. All results assume the switch sensitivity adjustment is set to maximum.
Installation assumptions: Calculations presume the flow switch is installed vertically (top-entry) in a horizontal pipe run, with a minimum of 5 pipe diameters (5D) of unobstructed straight pipe both upstream and downstream of the insertion point. This provides a fully developed velocity profile at the sensing element. Deviations from this configuration — including angled or horizontal mounting, proximity to bends, valves, reducers or tee junctions — will alter the local velocity profile, introduce asymmetric flow impingement on the paddle, and may produce actuation forces that differ significantly from those calculated here. Such installation effects are not accounted for in this tool.
| Drag Force on Paddle / Wire Sensor | |||
|---|---|---|---|
| Kelco Flow Switch | Force (g) | Force (N) | Flow Status |
Kelco paddles are made from either Polypropylene or Monel Metal (a corrosion-resistant stainless steel alloy). For switches with a 25mm (1") process connection, the standard Polypropylene paddle measures 29mm wide × 168mm long. For switches with a 20mm (¾") process connection, the paddle is 22mm wide × 168mm long. All Polypropylene paddles are designed to be trimmed — both in length and width — so they can be sized to suit each specific application.
Kelco's all-metal construction flow switches (the FM-D range) are fitted with a Monel Metal paddle measuring 22mm wide × 168mm long as standard. An optional extended Monel Metal paddle — 22mm wide × 300mm long — is also available for use in large-diameter pipes and open channel installations. Contact Kelco for details.
Trailing wire sensors are compatible with most Kelco paddle flow switches and can be retrofitted if needed. These 316 Stainless Steel wire sensors have a 2mm diameter and are available in standard lengths from 50mm to 300mm, in 50mm increments. If a wire needs to be cut to a non-standard length, the cut end must be TIG welded or silver soldered to prevent the wire from fraying.