What points need attention when installing a clamp-on ultrasonic flowmeter?

When installing a clamp-on ultrasonic flowmeter, attention must be paid to multiple aspects such as pipeline conditions, sensor installation position, and environmental factors to ensure measurement accuracy and equipment stability. Here are the specific precautions:

I. Inspection of Basic Pipeline Conditions

1. Pipeline Material and Wall Thickness
   • Clamp-on sensors rely on ultrasonic waves penetrating the pipeline for propagation. Therefore, the pipeline must be made of non-metallic materials (such as PVC, PE) or thin-walled metallic materials (such as stainless steel, carbon steel, with a wall thickness usually recommended to be ≤ 10mm).
   • If the inner wall of the pipeline has an anti-corrosion layer, scaling, or lining (such as cement, rubber lining), it is necessary to confirm that its thickness is uniform and does not affect sound wave transmission; otherwise, measurement errors may occur.
2. Pipeline Diameter and Flow Velocity Range
   • Ensure that the measurement range of the flowmeter matches the pipeline diameter and actual flow velocity (generally, clamp-on types are suitable for pipelines with DN15~DN6000, and the flow velocity is usually recommended to be 0.3~12m/s).
   • Excessively low flow velocity (<0.3m/s) may result in weak signals, and excessively high flow velocity (>12m/s) may affect measurement stability due to turbulence.
3. Medium State in the Pipeline
   • The medium must be a single-phase fluid (liquid without a large number of bubbles, suspended particles, or impurities). Otherwise, bubbles or particles will reflect/scatter sound waves, leading to signal loss or errors.
   • Avoid stratification, vortices, or severe turbulence of the medium in the pipeline (such as near valves and pumps), and ensure that the measurement section is a stable full-pipe flow.

II. Selection of Sensor Installation Position

1. Straight Pipe Section Requirements
   • To ensure stable fluid flow patterns, the sensor installation point must meet the length requirements of the straight pipe sections before and after:
     • Upstream (the side far from the sensor): If there are elbows, valves, pumps, or other resistance components ahead, it should be ≥ 10 times the pipeline diameter (10D); if there are no complex components, it should be ≥ 5D.
     • Downstream (the side close to the sensor): ≥ 5D (if there are resistance components downstream, it is recommended to be ≥ 3D).
   • Avoid installing at the highest point of the pipeline (where air may accumulate) or the lowest point (where slag may accumulate).
2. Installation Direction and Spacing
   • According to the pipeline material and diameter, select the V-method (sound waves obliquely pass through the pipeline, suitable for small and medium diameters) or Z-method (sound waves directly pass through the pipeline, suitable for large diameters or thick-walled pipes).
   • The two sensors (transmitting end and receiving end) must be installed symmetrically on both sides of the pipeline to ensure that the sound wave path is parallel to the pipeline axis, and the spacing conforms to the calculation formula in the flowmeter manual (usually related to the pipeline diameter and sound wave refraction angle).
3. Avoid Interference Sources
   • Keep away from strong electromagnetic interference sources (such as motors, transformers, frequency converters) to prevent electromagnetic signals from interfering with ultrasonic transmission.
   • Keep away from vibration sources (such as pumps, compressors). If necessary, install shock-absorbing pads to prevent poor sensor fitting due to pipeline vibration.

III. Details of Sensor Installation Operation

1. Pipeline Surface Treatment
   • Before installation, clean the pipeline surface to remove rust, paint, oil, or oxide layers to ensure close contact between the sensor and the pipeline (if necessary, sand to a metallic luster; non-metallic pipelines need to remove surface dirt).
   • If the pipeline surface is uneven, apply special coupling agent (such as silica gel, glycerin) to fill the gaps and exclude air (air will severely attenuate sound waves). The coupling agent must be compatible with the medium (not corrosive to the pipeline).
2. Sensor Fixing Method
   • Use a special fixture to firmly fix the sensor on the pipeline to avoid loosening (loosening will cause signal instability), but pay attention to the strength to prevent pipeline deformation or sensor damage.
   • For easily deformable pipelines such as plastic ones, the fixture strength should be moderate to avoid the pipeline being pinched flat and affecting the flow pattern.
3. Cable Connection and Protection
   • Sensor cables must be kept away from high-voltage lines to avoid signal interference, and the cable length must meet the requirements in the manual (excessively long cables may cause signal attenuation).
   • For outdoor installation, it is necessary to waterproof the cables (such as installing waterproof joints) and protect them from sun exposure to avoid cable aging.

IV. Environment and Working Condition Adaptation

1. Ambient Temperature and Humidity
   • The working ambient temperature of the sensor must be within the allowable range of the equipment (usually -30℃~+60℃). Avoid long-term exposure to extremely high temperatures, low temperatures, or high humidity environments (install thermal insulation or sunshade devices if necessary).
   • If the temperature of the pipeline medium is too high (such as >100℃), confirm the high-temperature resistance of the sensor to avoid failure of the coupling agent or damage to the sensor due to high temperature.
2. Explosion-Proof and Protection Requirements
   • When installing in flammable and explosive environments (such as chemical workshops), select explosion-proof sensors that meet the on-site explosion-proof grade requirements.
   • For outdoor or humid environments, ensure that the equipment protection grade is ≥ IP65 to prevent rainwater and dust intrusion.

V. Commissioning and Verification After Installation

1. Signal Strength Detection
   • After installation, check the signal strength through the flowmeter host (usually expressed as a percentage or decibel). Ensure the signal is stable (recommended ≥ 60%). If the signal is weak, readjust the sensor position or coupling agent.
   • Observe whether the instantaneous flow and cumulative flow match the actual working conditions (verification can be done by comparing with known flow values or empirical values).
2. Long-Term Stability Check
   • Regularly check the fixing of the sensor and the state of the coupling agent (whether it is dry or detached), especially in scenarios with large vibration or temperature changes.