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Quick Answer: Silver Instruments supplies compact inline flow sensors for equipment OEMs, skid builders, and process plants that need fluid presence detection and speed output in DN10 to DN50 lines. These sensors transmit 4-20 mA, pulse, or switch signals to a PLC, pump interlock, or valve controller. Send your pipe size, fluid type, pressure, temperature, and flow range to receive a fixed quotation from our team.
Most engineers look for inline flow sensors when a full flow meter is too large, too costly, or unnecessary for the control loop. We have seen this on customer sites many times. A food plant in Vietnam uses a DN20 inline sensor to confirm CIP return flow before the next wash step. A pump package builder in Chile uses a DN15 speed sensor to detect diesel flow to a burner. Both applications needed a compact device with no bypass line.
Some equipment drawings use the term speed sinks for the pulse or frequency input channel on a controller. In practice, the flow sensor sends a speed signal. The controller input accepts that signal. That is why the phrase appears in OEM specifications. Silver Instruments treats the sensor as the source and the PLC or motor drive as the receiving device.
An inline flow sensor sits directly in the fluid stream. It detects fluid presence, flow speed, or both depending on the model. A flow switch gives a simple on or off signal. A speed sensor gives a frequency or analog output that represents flow velocity. Both outputs are common in equipment control panels.
Here is the thing. A pump interlock only needs to know if liquid is moving. A flow switch with a 24 V DC supply can shut down the pump in under one second. A dosing skid may need more detail. A speed sensor with a pulse output can tell the PLC how fast the fluid moves and confirm that a metering pump is actually dosing.
Common pipe sizes for inline sensors are DN10, DN15, DN20, DN25, and DN50. Standard process connections include NPT, BSP, and tri-clamp. For water and light chemicals, NPT is often the cheapest option. For food and beverage lines, tri-clamp is the preferred connection because it allows quick removal for cleaning.
Silver Instruments offers three main inline flow sensor technologies. Paddle wheel sensors work well in clean water and light chemicals up to 80 °C. They provide a pulse output that is easy to read on a PLC. Thermal dispersion sensors work for oil, coolant, and low conductivity fluids. They have no moving parts and are suitable for flow presence detection in compressors and cooling loops. Compact electromagnetic sensors work for conductive fluids such as wastewater, brine, and chemicals. They provide stable speed output even when the fluid is dirty.
Because clean water is conductive enough for an electromagnetic sensor but oil is not, we always ask for fluid type before quoting. This avoids quoting a sensor that cannot physically work. Material selection also matters. A 316L body with PTFE liner and EPDM O-rings handles many industrial fluids. FKM O-rings suit oil and fuel. Pressure ratings up to 40 bar and process temperatures up to 120 °C cover many mid-range plant applications. ATEX Zone 1 versions are available for hazardous areas in oil and gas or chemical storage.
Do not assume one sensor fits every fluid. A paint manufacturer in Southeast Asia asked for a DN15 inline flow sensor for solvent dosing. The solvent had low conductivity. A paddle wheel sensor was not suitable. We supplied a thermal dispersion version with 316L body and FKM O-rings. The output was a 4-20 mA signal tied to a pump interlock. That solved the issue without a full flow meter.
Compact inline flow sensors need a full pipe. Mount the sensor in a location where the pipe always stays full. For paddle wheel and electromagnetic sensors, keep at least 10 pipe diameters of straight run upstream and 5 pipe diameters downstream. This reduces swirl and unstable readings. Paddle wheel sensors should be inserted with the shaft horizontal on horizontal pipes. That prevents air from sitting at the sensing point.
For pulse and frequency outputs, use shielded cable. Keep the signal cable away from variable frequency drive cables. In practice, most equipment builders skip this part and then see random pulse counts on the PLC. We have helped customers in Malaysia and Nigeria solve this exact issue by moving the cable route and adding a small signal isolator.
If the fluid contains particles, install a strainer upstream. This protects the paddle wheel or flow channel from damage. For thermal dispersion sensors, make sure the sensor tip is fully inserted into the flow stream. A partially inserted tip gives false low readings. For electromagnetic sensors, verify that the pipe is filled and that the fluid has a minimum conductivity of 20 µS/cm.
Water and wastewater plants use inline flow sensors to monitor chemical dosing, filter backwash, and pump discharge. Food and beverage plants use them for CIP return lines, pasteurizer cooling water, and bottle washer feeds. Oil and gas packages use them for seal water, diesel forwarding, and compressor cooling loops. Marine systems use them for fresh water generation and bilge line monitoring.
We ship regularly to Southeast Asia, Oceania, Latin America, Africa, and the Middle East. A desalination skid builder in Oman ordered DN25 electromagnetic inline sensors for antiscalant dosing verification. A dairy plant in Australia used a DN20 paddle wheel sensor on a CIP return line. These are small projects with high operational impact.
For a fixed price, send us these parameters: pipe size in DN, fluid type, pressure in bar, temperature in °C, flow range in L/min or m3/h, and required output signal. Also tell us the power supply available, such as 24 V DC or 220 V AC. We will reply with a recommended inline flow sensor model, price, lead time, and freight cost.
Contact Silver Automation Instruments directly. Tel: +86-25-68650347. WhatsApp: +86-25-52155837. WeChat: +86 15365082610. You can also see our flow meter ranges at flow-meter.com.au.
1. What is the difference between a flow switch and a speed sensor?
A flow switch gives a dry contact or transistor output when flow is present. A speed sensor gives a pulse or 4-20 mA signal that changes with flow velocity. Use a flow switch for pump interlock. Use a speed sensor for dosing verification or closed loop control.
2. Can an inline flow sensor handle liquids with low conductivity?
Yes. Thermal dispersion inline sensors work in oils, fuels, and low conductivity fluids. Paddle wheel sensors also work in low conductivity fluids if the fluid is clean and the velocity is within range. Electromagnetic sensors need a minimum conductivity of 20 µS/cm.
3. What is the maximum pressure and temperature for a compact inline sensor?
Standard models from Silver Instruments handle 40 bar and 120 °C. High temperature and high pressure options are available for specific cases. Send your process limits before ordering.
4. How long does the straight run need to be?
Use 10 pipe diameters upstream and 5 pipe diameters downstream for paddle wheel and electromagnetic inline flow sensors. This reduces swirl and improves repeatability. A compact thermal dispersion sensor is less sensitive but still needs a full pipe and stable flow profile.
5. Which industries use these sensors the most?
OEM skid builders, water and wastewater plants, food and beverage lines, oil and gas packages, and marine systems. We see the highest demand from Southeast Asia, the Middle East, and Latin America for DN15 to DN25 inline flow sensors.
