Company Profile

Keyence Flow Meters and Keyence Flow Sensors: Clamp-On FD-Q Series Digital Flow Monitors

Quick Answer: The Keyence FD-Q series is a clamp-on digital flow monitor for liquid lines with pipe outer diameters from about 10 mm to 50 mm. It is a good fit for clean water, DI water, cooling water, and light chemical flow confirmation without pipe cutting. Silver Automation Instruments supplies FD-Q compatible flow monitors and inline flow meters for industrial buyers in Southeast Asia, Oceania, Latin America, Africa, and the Middle East.

Most engineers in Vietnam, Malaysia, Saudi Arabia, and Chile only look at clamp-on flow meters when shutdown time is expensive. The FD-Q series uses a non-contact mounting method. The pipe stays closed. The process stays live. This saves hours on DN15 and DN25 lines because there is no draining, no threading, and no spool piece.

Here is the thing. A clamp-on flow meter is not always the correct device. For clean water and light chemicals, it works well. For slurries, heavy oil, or liquids with solids, an inline flow meter is safer. We tell every customer to check the liquid type first and the pipe outer diameter second.

How the Keyence FD-Q Series Works in Practice

The Keyence FD-Q series mounts directly on the outside of a pipe. Keyence flow sensors in this line share the same clamp-on body style across several pipe size models. The sensor sends a 4-20 mA analog signal or a switch output to a PLC, panel meter, or pump interlock. Common pipe outer diameters covered by different FD-Q models range from 10 mm to 50 mm. The fluid temperature limit is typically 0 to 85 °C and the line pressure limit is around 1.0 MPa for water-like liquids.

The sensor is used most often on straight runs of plastic, copper, or stainless steel pipe. The pipe wall must be clean and the pipe must be full of liquid. Air bubbles near the sensor face will cause unstable readings. We have seen this many times on cooling water lines with poor venting.

Typical Industries and Application Scenes

Cooling water monitoring is the most common application. A plastic injection plant in the Philippines installed an FD-Q clamp-on sensor on a DN25 copper line carrying cooling water at 22 °C and 3 bar. The flow alarm was set at 15 L/min to protect a hydraulic heat exchanger. Installation took 20 minutes during a gap between production batches. No welder. No pipe cutting. The customer used the 4-20 mA output to feed a site SCADA system.

Other sites use these flow sensors on DI water loops in semiconductor wet benches, demineralized water in pharmaceutical skids, and chilled water in CNC spindle cooling circuits. If the water conductivity is below 10 µS/cm, the FD-Q type monitor is a good fit because it does not need conductive electrodes. In the UAE and Saudi Arabia, we also see clamp-on flow monitors on district cooling branch lines where draining a charged network is not practical.

FD-Q Series vs Inline Flow Meters

An inline electromagnetic flow meter or oval gear flow meter gives better accuracy on batching, custody transfer, and high-viscosity liquids. But an inline meter needs a process connection. A clamp-on digital flow monitor like the Keyence FD-Q series is faster to fit on small lines and does not create a leak point. It is better for flow trending, alarm, and go/no-go confirmation. It is not the correct tool for custody transfer.

For water, DI water, and light chemicals below about 50 cP, a clamp-on flow monitor often pays for itself on the first avoided shutdown. Many plants use a clamp-on sensor for daily checks and add an inline meter later only if the process needs tighter accuracy or higher temperature and pressure ratings.

Key Specifications to Check Before You Order

Do not select a model by pipe schedule alone. Measure the actual pipe outer diameter with a caliper. Fo