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Liquid Ultrasonic Flow Meter Manual
Non-Invasive Transit-Time Transducer Layouts on Metal Pipes
Quick Answer: For metal pipes from DN15 to DN6000, use clamp-on transit-time transducers in V, W, or Z layout. V layout fits DN15 to DN100. Z layout works best on DN100 to DN6000 lines. W layout helps small pipes and weak signal conditions. Always enter exact pipe OD, wall thickness, material, and liquid type before mounting.
This manual was prepared by Silver Automation Instruments for installers and plant engineers. It covers non-invasive transit-time liquid flow measurement on carbon steel, stainless steel, copper, and ductile iron pipes. No cutting or welding is needed. You do not need a process shutdown.
Three Mounting Layouts
Most clamp-on jobs use one of three layouts: V, W, or Z. The meter calculates transducer spacing after you enter the pipe outside diameter, wall thickness, pipe material, and liquid type. Do not guess the wall thickness. Measure it with an ultrasonic thickness gauge.
V Method for DN15 to DN100
The V method is the first choice for small and medium metal pipes. Both transducers sit on the same side of the pipe. The acoustic signal reflects once off the far wall. This long path improves resolution on small lines.
Use V layout for clean water, demineralized water, light chemicals, and cooling water. Keep the pipe surface temperature below 150 °C unless high temperature transducers are ordered. On horizontal pipes, install the transducers at the 3 and 9 positions. Avoid the top position where air collects.
For a DN40 carbon steel pipe with a wall thickness of 3 mm, we start with 1 MHz transducers. Signal strength is normally stable above 60 percent.
Z Method for DN100 to DN6000
The Z method places transducers on opposite sides of the pipe. The acoustic signal crosses the pipe once. This layout tolerates high temperature, light suspended solids, and long pipe runs.
In practice, Z layout is standard for pipes DN100 and larger. It also works on smaller pipes when V method cannot hold a stable signal. A palm oil refinery in Malaysia used Z layout on a DN300 stainless steel line at 95 °C. The signal stayed stable for continuous batching.
For horizontal large pipes, place the transducers at the 2 and 10 positions. This avoids air pockets at the top and sediment at the bottom.
W Method for Small Pipes and Weak Signals
The W method bounces the acoustic signal twice across the pipe. This creates a longer path. It helps on pipe sizes from DN15 to DN50 where V method gives a weak signal. It also helps at low flow rates below 0.3 m/s.
This layout requires clean liquid. Gas bubbles or solids scatter the signal. A city water utility in the Philippines used W layout on a DN25 copper pipe for a district metering test. The meter read 0.25 m/s with stable signal quality.
Metal Pipe Surface Preparation
Here is the thing. Most installation problems come from poor surface preparation. For carbon steel, remove paint, rust, and scale at the transd
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For stainless steel and copper, clean the surface with a degreaser. Apply a thin layer of coupling compound to each transducer face. Do not use silicone grease above 120 °C unless the manual allows it. Check the real wall thickness. A 5 mm error can cause a 1 percent to 3 percent reading offset.
Signal Quality Checks
After mounting, check signal strength, sound velocity, and signal quality on the meter display. Our clamp-on ultrasonic flow meter shows these values in the installation menu. Keep signal strength above 60 percent. Compare sound velocity with the expected liquid value. Water is around 1480 m/s. Seawater is around 1520 m/s. Light oil is often 1300 m/s to 1400 m/s.
If the signal is weak, reapply coupling compound and check transducer spacing. On small pipes, change from V to W. On large or hot pipes, change from V to Z. But do not assume the electronics failed before checking the mount.
Typical Output and Ordering Data
The Silver Instruments clamp-on transit-time flow meter supports 4-20 mA, pulse, and RS485 Modbus RTU. The converter can be wall mounted or panel mounted. Accuracy is typically ±0.5 percent to ±1 percent of reading when the installation is correct. Flow velocity range is 0.01 m/s to 12 m/s. Liquid temperature range depends on the transducer type. Standard transducers cover -30 °C to 120 °C. High temperature transducers cover -30 °C to 200 °C.
Send us the pipe outside diameter in mm, wall thickness in mm, pipe material, liquid type, flow range, temperature in °C, and pressure in bar. Silver Instruments will confirm the transducer layout and provide a price.
FAQ
Q: Which layout should I use for a DN200 carbon steel cooling water pipe?
A: Start with the Z method. It gives better signal stability on pipes DN100 and larger. If the pipe is horizontal, mount transducers at the 2 and 10 positions.
Q: Can I use clamp-on transducers on old galvanized steel pipe?
A: Yes, but remove the zinc layer and rust at the mounting spot. The contact surface must be smooth. Measure the real wall thickness because old pipe often has internal scale.
Q: What if the liquid contains bubbles or solids?
A: Transit-time meters need a relatively clean liquid. A small amount of suspended solids can still work on Z layout. Heavy aeration or high solids content will cause signal loss. Choose an electromagnetic flow meter for high solids lines.
Q: Does pipe insulation affect the transducer mounting?
A: Yes. Remove enough insulation to mount the transducers directly on the metal pipe. Do not clamp transducers over insulation or jacket material.
Q: How do I get a price for a clamp-on ultrasonic flow meter for a seawater line?
A: Send your pipe OD, wall thickness, pipe material, seawater temperature, and flow range to Silver Instruments. Tel: +86-25-68650347. Whatsapp: +86-25-52155837. WeChat: +86 15365082610.
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