How Low Flow Detection Works
Extreme-Sensitivity Paddle Deflects at Near-Zero Flow
The low flow paddle is engineered for maximum sensitivity — its geometry and spring tension are tuned to respond to flow rates below 0.01 GPM. Even the slightest media movement deflects the paddle enough to begin stem travel toward the set point.
Tapered Inlet Compensates for Gas Compressibility
Low flows of gases introduce chatter caused by compressibility effects. A constantly expanding taper on the inlet side of the paddle smooths the flow profile as it reaches the sensing element, eliminating false trips without sacrificing sensitivity.
Switch Trips with Full Repeatability
Once the stem reaches the set point, the micro-switch trips cleanly. The low flow design maintains the same reliable, repeatable actuation as standard PEECO switches — just at flow rates far below what conventional paddles can detect.
Key Features
<0.01 GPM Detection
Flows of less than 0.01 GPM can be reliably detected with full repeatability. The low flow paddle geometry is purpose-built for extreme sensitivity — not a modified standard paddle.
Adjustable Paddle Width
Adjustable from half to full pipe diameter. Easily changed in the field to accommodate flow and media changes, half-full lines, and fluid separation applications without removing the switch from the line.
Minimal Pressure Drop
Designed for extreme sensitivity while allowing full flow with minimal pressure drop. The low flow paddle does not restrict the line — it senses without impeding.
Gas Compressibility Compensation
A constantly expanding taper on the inlet side compensates for chatter caused by gas compressibility at low flow rates — enabling reliable detection on gas lines where standard switches would produce false trips.
Folding Paddle Option
The folding paddle uses a helical-wound Inconel spring to allow actuation at flow rates even lower than the standard low flow paddle — while still permitting full, unrestricted flow at high velocities. This makes it the preferred choice for flare gas stacks, where flow can swing from near-zero to extremely high in the same line.
Lower Actuation Point
Trips at flow rates below standard low flow paddle capability
Inconel Spring
Helical-wound for corrosion resistance and consistent spring force
High-Velocity Compatible
Folds flat at high flow — does not impede media passage
Typical Applications
Chemical dosing and metering lines
Laboratory flow monitoring
Flare gas stack flow detection
Lubrication system flow confirmation
Low-flow cooling circuits
Pharmaceutical process lines
Pilot plant and R&D flow monitoring
Half-full or partially filled pipe detection
Availability
Low flow switches are available in both explosion proof and non-explosion proof configurations, in screwed or wafer tee styles. Recommended for line sizes up to 2″ inclusive. Specify your series, tee style, and whether the folding paddle option is required when requesting a quote.
N Series
Non-explosion proof. Standard industrial environments.
E Series
Explosion proof. Hazardous area classification required.
Specifications
| Minimum Detectable Flow | Less than 0.01 GPM |
| Paddle Adjustment | Half to full pipe diameter, field-adjustable |
| Recommended Line Size | Up to 2″ inclusive |
| Available Models | Explosion proof and non-explosion proof |
| Tee Styles | Screwed or wafer |
| Gas Compensation | Constantly expanding inlet taper |
| Folding Paddle Option | Inconel helical-wound spring, for flare gas and high-velocity media |