Comparison between FRP pipe and steel pipe

01 06, 2025

Steel pipe is a traditional pipe material, which is made of steel plate spirally wound into a cylindrical shape and then welded. In terms of strength and rigidity, both sand-reinforced fiberglass pipe and steel pipe have characteristics. However, from the perspective of corrosion resistance and service life, hydraulic characteristics, energy consumption, water quality, transportation, installation, and price, sand-reinforced fiberglass pipe is more competitive than steel pipe.
1. Comparison of technical performance
1 Design flexibility
FRP pipe has design flexibility and can be designed and manufactured for any applicable technical parameter combination, which can maximize the needs and requirements of customers; while the design of steel pipe is less targeted and only has this feature to a certain extent.
2 Strength performance
FRP pipe has strength performance, the allowable working pressure can reach 6.4MPa, and the design safety factor is more than 6 times.
1) Tensile strength:
Depending on the fiber laying and content, the apparent circumferential tensile strength of the FRP pipe can be between 140~520MPa, and the axial tensile strength can be between 70~320MPa;
2) Bending strength:
Depending on the fiber laying and content, the apparent circumferential bending strength of the FRP pipe can be between 154~340MPa. Not only is the pipe mouth a flexible interface, but the pipe is also flexible.
3) Impact strength:
The FRP pipe has a good impact strength of more than 300kgf•cm/cm2. Tests have shown that the Φ2600 FRP pipe was dropped freely from a height of 1.8m without any damage;
3 Stiffness performance
In terms of stiffness performance, both can meet engineering needs. The FRP pipe increases the stiffness by adding a sand layer in the middle layer of the pipe wall that bears less bending stress according to engineering needs, which can meet any stiffness requirements put forward by the user. The stiffness of the steel pipe itself is large enough and can be ignored.
In terms of bearing short-term unexpected overloads (such as trucks), FRP pipes can bear them through their elastic deformation and automatically return to their original state after the load is removed; while steel pipes are easily sheared or broken under certain deformation.
4 Service life
The matrix of FRP pipes is an extremely stable polymer material, and its breaking pressure is designed to be 6 times the working pressure, which can ensure a 50-year service life (see AWWA, ASTM standards).
The service life of steel pipes is generally 20 years. Frequent maintenance during operation, difficult maintenance, and high cost. When the steel pipe is buried underground, factors such as the water quality in the pipe, the surrounding soil, groundwater, and whether there is an electric field near the buried area will cause corrosion to the inner and outer walls of the pipe. Therefore, the standard stipulates that the inner and outer surfaces of the pipe body should be coated with asphaltene or other anti-corrosion materials. Because the coating material is different from the material of the steel pipe, in long-term operation, it is easy to produce interface stratification and fall off due to the effects of climate heat and cold, hydraulic impact, etc., and gradually lose the anti-corrosion coating layer, so that the iron molecules on the inner surface of the pipe are oxidized and electrochemically corroded, which will inevitably reduce the service life.
5 Comparison of hydraulic characteristics
The inner wall of the FRP pipe is very smooth. The Hazen-Williams roughness coefficient C value of the new FRP pipe is 160-165, and its conservative design value (calculated based on 50 years) is 150. The C value of the new steel pipe is 120, and after use, it is C=65. The reduction of the C value is caused by the oxidation of iron molecules on the inner surface of the pipe and electrochemical corrosion reflected in the scaling of the inner wall.
Data comparing the flow rate of steel pipe and FRP pipe. Because the absolute roughness of the new steel pipe is 0.05mm, the absolute roughness of the corroded steel pipe is 3mm, and the absolute roughness of the corroded steel pipe is 60 times that of the uncorroded steel pipe;
Taking the Hazen-Williams average roughness coefficient C value of the steel pipe as 100 and the C value of the FRP pipe as 150, the flow rate of the 12-inch FRP pipe is the same as that of the 14-inch steel pipe. In other words, under the same pipe diameter conditions, the flow rate of the FRP pipe is 36% greater than that of the steel pipe.
6 Energy consumption comparison
Since the Hazen-Williams roughness coefficient C value of steel pipes decreases significantly with the years, its energy consumption will also increase significantly. The energy consumption of steel pipes is much greater than that of FRP pipes. There are two main reasons: one is due to factors such as oxidation and electrons.