FRP Pipe Flow Measurement — Solved SLDF2085 Clamp-On Ultrasonic Flow Meter Passes Third-Party Calibration On DN300 FRP Pipe

         FRP (fiber-reinforced plastic) pipes have long been considered one of the most difficult applications for clamp-on ultrasonic flow measurement. High acoustic attenuation and complex sound velocity behaviour in the non-homogeneous composite material often defeat conventional clamp-on meters. Now Solidat's SLDF2085 has proven the answer: in a third-party calibration conducted by Guangdong Combell Flow Intelligent Inspection Platform on a DN300 FRP pipe (wall thickness 10 mm), the SLDF2085 achieved a measurement accuracy of 1% of reading after calibration.

1. The Challenge: Why FRP Pipes Are Difficult 

        FRP pipes are widely used in chemical, water treatment and marine applications for their corrosion resistance, light weight and insulation properties. However, as a non-homogeneous composite material, FRP causes strong acoustic attenuation and unpredictable sound velocity, which makes stable clamp-on ultrasonic measurement extremely difficult - many meters simply fail to obtain a usable signal.

Fig.1.1 FRP pipes at the test site

2. The Solution: SLDF2085 Clamp-On Ultrasonic Flow Meter

          The SLDF2085 is Solidat's clamp-on ultrasonic liquid flow meter based on bidirectional transit-time technology. It has no moving parts and is maintenance-free, and a patented measurement algorithm ensures drift-free long-term operation with automatic adaptation to fluid property changes. Pipe size range: 15–7600 mm; repeatability ±0.2% of reading; turndown 400:1; outputs 4–20 mA, HART, Modbus/RS485.

 

Fig.2.1 SLDF2085 clamp-on ultrasonic liquid flow meter

3. Third-Party Verification: Static Gravimetric Calibration 

            To verify the reliability of SLDF2085 on FRP pipes, Solidat (Zhuhai) commissioned an independent third-party laboratory - Guangdong Combell Flow Intelligent Inspection Platform - to run a calibration test. The platform establishes the flow reference with a static gravimetric flow standard: fluid is delivered into weighing tanks (12 T / 3 T / 300 kg / 30 kg); the mass increase per unit time combined with fluid density gives the actual flow rate.

Fig.3.1 Guangdong Combell Flow Intelligent Inspection Platform

4. Test Conditions & Key Data

           The test was carried out on a DN300 FRP pipe with 10 mm wall thickness, medium: water, line pressure 0.049 MPa, fluid temperature 27.8–27.9 ℃, test flow approx. 159–160 m³/h, calibration time 120 s. The transducers were installed in the Z-method arrangement with solid coupling compound.

Item	Condition
Pipe under test	DN300 FRP pipe, wall thickness 10 mm / DN300
Medium	Water
Line pressure	0.049 MPa (approx. 0.5 bar)
Fluid temperature	27.8 – 27.9 ℃
Test flow	approx. 159 – 160 m³/h (observed)
Reference method	Static gravimetric flow standard
Transducer arrangement	Z-method
Calibration time	120 s

 

5. Observed Data: SLDF2085 vs Gravimetric Reference

             The instantaneous flow readings of SLDF2085 agreed closely with the gravimetric reference, with an observed deviation of approx. 0.2% – 0.6%:

Point	SLDF2085 (m³/h)	Reference (m³/h)	Note
Obs.1	159.649	159.31	SLDF2085 totalized 2.905 m³; 12 T tank
Obs.2	159.414	160.3	SLDF2085 totalized 18966.500 m³
Obs.3	-	159.31	12 T tank: accumulated 2645.50 kg

 

6. Result: 1% Accuracy Achieved on FRP Pipe

             The SLDF2085 completed the calibration test successfully and operated stably on the DN300 FRP pipe. After static gravimetric calibration, with the transducer probes installed in the Z-method arrangement, the SLDF2085 achieved a measurement accuracy of 1% of reading on the DN300 FRP pipe with 10 mm wall thickness.

7. Test Site Photos

             Actual photos taken at the calibration site (October 2026):

Fig.4 On-site SLDF2085 and platform monitoring screen

Fig.5 SLDF2085 display: totalized 2.905 m³, flow 159.649 m³/h

Fig.6 DN300 FRP pipe test bench with clamp-on transducers

Fig.7 FRP pipe section with transducer clamp installation

8. About Solidat

              Solidat is a professional manufacturer of level and flow measurement instruments, serving customers in more than 60 countries and regions worldwide. Our product line includes radar level meters, ultrasonic flow meters, and water quality analysers for industrial and municipal applications.

 

 

Contact us ：

Email: solidat@solidat.net |

Web: www.solidat.net |