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Dwyer Paddle Wheel Flow Meter: Low Cost Spool Velocity Inline Sensors Specs
Quick Answer: Silver Instruments supplies low cost spool body paddle wheel flow meters for clean water, cooling water, and low viscosity liquids. These inline velocity sensors match many Dwyer style paddle wheel installations from DN15 to DN600. Send us your pipe size (DN), flow range, pressure (bar), and temperature (°C) for a quote.
What Is a Spool Body Paddle Wheel Flow Meter
A paddle wheel flow meter uses a rotating impeller inserted into a pipe spool. Flow velocity turns the paddle wheel. The rotation creates a frequency or pulse signal. The signal is linear to flow velocity. A spool body style is a short pipe section with flanges or threaded ends. This design makes installation simple. You remove a pipe spool and bolt the meter in place. No cutting or welding on site. Dwyer paddle wheel flow meters are common in HVAC, water treatment, and light industrial lines. Silver Instruments offers a low cost alternative with similar spool dimensions and signal outputs.
Key Specifications for Dwyer Style Paddle Wheel Sensors
Typical line sizes are DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100, DN125, DN150, DN200, DN250, DN300. Some spool models go to DN600. Process connections include ANSI 150 flanges, JIS 10K, or BSP threaded ends. Flow range depends on pipe ID and impeller material. A DN50 spool sensor can read 0.3 to 10 m/s in water. Accuracy is usually ±1.0% of full scale or ±2.0% of reading. Repeatability is ±0.5%. Maximum pressure is often 10 bar or 16 bar at 20 °C. Temperature limits are 0 to 85 °C for standard models. High temperature versions reach 120 °C. Wetted materials include polypropylene, PVDF, 316 stainless steel shaft, and ceramic bearings.
Output options include pulse, 4-20 mA, and pulse plus 4-20 mA. A blind pulse output is the lowest cost. Models with a local display and 4-20 mA transmitter cost more but save panel space. Power supply is 12 to 24 V DC. Some inline spool sensors also offer a flow switch output with a relay. This is useful for pump protection. In practice, most engineers in Southeast Asia select pulse output for PLC totalizing and 4-20 mA for remote flow indication.
Why Low Cost Spool Sensors Work for Water and Wastewater
Here is the thing. Most clean water applications do not need exotic materials. The paddle wheel meter uses plastic or PVDF body and a simple impeller. The cost is 40 to 60 percent lower than a magnetic flow meter in the same line size. That matters when you buy 20 or 30 meters for a cooling tower project. A water treatment contractor in Vietnam recently ordered DN80 polypropylene spool paddle wheel meters for reverse osmosis skids. The main requirement was a 4-20 mA signal and local totalizer. The meters were installed in two hours. The flow range was 2 to 40 m³/h. Operating pressure was 4 bar. Temperature was 28 to 32 °C. This is a typical case.
But this meter is not for dirty water. Particles above 75 microns can jam the impeller. Slurries, sewage, and liquids with fibers will damage the paddle wheel. For those applications, Silver Instruments recommends an electromagnetic flow meter. We have seen customer sites where a paddle wheel meter in raw river water failed within three months. The impeller stopped rotating because of sand and organic matter. If your water has suspended solids, a full bore magmeter is the safer choice.
Dwyer Paddle Wheel vs Silver Instruments Spool Sensors
Dwyer paddle wheel flow meters are known in the HVAC and water treatment market. The sensor specs are standard. Silver Instruments builds spool type paddle wheel flow meters with the same pulse and 4-20 mA outputs. The main difference is price and lead time. We supply from our Nanjing factory to customers in Australia, New Zealand, Mexico, Chile, UAE, and South Africa. A DN50 polypropylene spool paddle wheel meter with pulse output costs around USD 180 to USD 260 depending on volume. A similar Dwyer configured meter might cost USD 400 to USD 600 from a local distributor. That gap matters for OEM skid builders and panel shops.
Dwyer models often have a compact wafer or insertion design. The inline spool version is less common. Silver Instruments spool sensors include flange or threaded ends to match your existing pipe spec. You send
Installation and Wiring Notes
Most engineers skip this part. The paddle wheel sensor needs a straight pipe run. Standard guidance is 10 pipe diameters upstream and 5 pipe diameters downstream. The impeller must sit in the center of the pipe. A depth setting tool is used for insertion models. For spool body models, the impeller is factory set. No adjustment is needed on site. Mount the meter in a horizontal pipe with the impeller axis vertical. This prevents air bubbles from collecting on the bearing. Avoid installing the meter at the highest point of a pipe. Avoid downstream of a partially closed valve or a pump discharge without a straight run.
Wiring is simple. Pulse output has three wires. Red is power positive. Black is ground. Yellow or white is the signal. The signal is an open collector NPN pulse. Connect a 10 kOhm pull up resistor if your PLC input does not have one. For 4-20 mA output, use a 2 wire loop or 3 wire loop depending on the model. Calibrate the display in engineering units. Use the K factor stamped on the meter. For example, a DN50 spool sensor may have a K factor of 52.3 pulses per liter. Enter this value in your flow totalizer or PLC. We include a calibration certificate with every meter.
Common Applications and Country Examples
HVAC chilled water and hot water loops in Australia and the Gulf states use DN40 to DN200 spool meters. The flow range is 1 to 300 m³/h. Water temperature is 5 to 95 °C. We supply brass or polypropylene bodies. For chemical dosing lines, PVDF body and ceramic bearings work with mild acids and alkalis. A fertilizer plant in Malaysia uses DN25 PVDF paddle wheel sensors for demineralized water at 10 to 50 L/min. Pressure is 2 bar. Temperature is 30 °C. For marine engine cooling water, a shipyard in Turkey ordered DN80 bronze spool paddle wheel meters with pulse output. The meters measure seawater flow at 10 to 60 m³/h. In this case the customer installed a strainer upstream to protect the impeller.
How to Request a Quote
Send us a short list of your operating conditions. We need pipe size (DN), flow range in m³/h or L/min, media type, pressure (bar), temperature (°C), power supply, and output signal. Also tell us the process connection standard. We will reply within 24 hours with a price in USD or AUD. Our contact numbers are +86-25-68650347 and Whatsapp +86-25-52155837. WeChat is +86 15365082610. You can also send your inquiry through flow-meter.com.au.
Silver Instruments serves distributors and end users in Southeast Asia, Oceania, Latin America, Africa, and the Middle East. We supply Coriolis mass flow meters, electromagnetic flow meters, ultrasonic flow meters, vortex flow meters, oval gear flow meters, thermal mass flow meters, pressure transmitters, and paperless recorders. For this paddle wheel spool meter, ask for the SIL-PW-SPOOL series. We will send a datasheet with dimensions, wiring diagrams, and material choices.
FAQ
Can I use a Dwyer paddle wheel flow meter for wastewater? No. Paddle wheel sensors are for clean water and low viscosity clean liquids. If your wastewater contains solids or fibers, choose an electromagnetic flow meter.
What is the minimum conductivity for a paddle wheel meter? None. A paddle wheel meter does not need conductivity. It measures mechanical rotation. This is one advantage over a magmeter.
What output signal should I select? Most users select pulse for PLC totalizing and 4-20 mA for analog trending. A local display is helpful for field readings. If you need both pulse and analog, select a model with a transmitter and display.
How do I select the K factor? The K factor is set at the factory and stamped on the meter body. Enter the pulses per liter value into your flow computer or PLC. If the impeller is replaced, use the new K factor supplied with the replacement kit.
What is the delivery time for a spool paddle wheel flow meter? Common DN25 to DN150 spool meters ship in 7 to 15 working days. Special flange standards or exotic body materials may take 20 to 30 working days.