Discussion on FRP duct and Traditional duct

With the process of human industrialization, we develope and apply many new materials. By using them for industrial commercial use, it has achieved great economic and environmental effects. As FRP duct manufacturers, we can apply the technology in a variety of fields. Today I want to share the prospect and FRP duct applications including different situations.

The FRP pipe consists of glass fiber and industrial resins. So it belongs to the category of glass fiber reinforced plastic FRP products. Before the use of industrial synthetic resins, there are some usual duct systems, many of which use metal materials. And the most common is steel duct system.

Metal duct board is a kind of traditional pipe. And it’s welded by spirally winding steel plates into a cylindrical shape. From aspects of strength and stiffness, filament wound FRP pipes and steel pipes have excellent properties. But, in many other ways, the filament wound fiberglass duct is superior than metal duct board. For example, corrosion resistant, service life, hydraulic features, energy consumption, carriage, installation, and price. So, FRP duct applications including drinking water pipelines, distribution, sewage, rainwater pipes, water wastewater underground and others.

FRP duct

Technical performance comparison:

1. Design flexibility

As a kind of FRP duct, glass fibers pipe has design flexibility. It can be designed and manufactured for any suitable combination of technical parameters. So it can well meet the needs and requirements of customers. The design of the steel pipe is relatively weaker than that of fiberglass reinforced plastic FRP duct. As we all know, metal duct only has this characteristic in some aspects.

2. Strength performance

Fiberglass reinforced plastic FRP duct has excellent strength properties. Its largest allowable working pressure can reach 6.4MPa. And the design safety factor is more than six times.

1)Tensile strength. According to the laying and content of glass fibers, the apparent hoop tensile strength of FRP duct can be between 140-520MPa. And its axial tensile strength can be between 70-320MPa.
2) Flexure strength. According to the laying and content of glass fibers, the apparent hoop bending strength of FRP ductwork can be between 154-340MPa. Not only the nozzle is a flexible interface, but the pipe is also adjustable.
3) Impact strength. The impact strength of FRP pipes is more than 300kgf • cm / cm2. Tests show that the Φ2600 FRP pipes can drop freely from a height of 1.8m without any damage.

3. Stiffness performance

In terms of stiffness performance, both of them can meet engineering requirements. The FRP is in the middle layer of the pipe wall with less bending stress. According to the needs of the project, FRP duct manufacturers add the sandwich layer to increase the rogidity. It can meet any requirements proposed by the customer. However, the stiffness of sheet metal ducts is pretty large so we can ignore it.
When subjected to short-term accidental overloads (such as a truck), the FRP pipe can bear the load through its elastic deformation. It can automatically return to its original state after removing the pressure. However, the steel duct is easily sheared or broken under certain strain.

fiberglass duct

4. Service life

The matrix of FRP pipe is an extremely stable polymer material. And it can usually guarantee a service life of more than 30 years. While, the service life of steel pipes is 20 years. Frequent maintenance during operation makes maintenance difficult and expensive. When the steel pipe is running in water wastewater underground, many factors will cause corrosion inside and outside the pipe. For example, factors include water quality in tubes, surrounding soil, and the presence of an electric field near the buried zone. Thus, under the standard, suppliers should coate asphaltene or other corrosion resistant materials. We paint them not only on inner but also outer surface of the pipe.

The content of coating is different from the materail of steel pipe. In the long-term operation, it is affected by the effects of cold and hot weather and hydraulic shock. It is easy to cause the interface to fall off layer by layer and gradually lose the corrosion resistant coating. Then, Iron molecules on the inner surface of the tube produce oxidation and electrochemical corrosion. It will definitely reduce the service life. In particular, demads for industrial water constantly increase. As a result, it makes the requirements for pipes that carry industrial water higher and higher. Some are even much higher than that of traditional metal duct board. Finally, the application of fiberglass duct in industrial water demand solves this problem.

5. Comparison of hydraulic characteristics

The inner wall of the FRP pipe is very smooth. Hazen-Williams roughness coefficient C of the new glass fiber reinforced plastic pipe is 160 to 165. While, its conservative design value (based on 50 years) is 150. The C value of the new steel pipe is 120, and after use, its C is 65. The reason of C value decrease is the inner fouling, which is caused by Oxidation and electrochemical corrosion of iron molecules.

The following is the data comparing the flow rate of the steel duct and the fiberglass duct. As we all know, the absolute roughness of the new steel pipe is 0.05mm. After corrosion, it is 3mm, which is 60 times of that of uncorroded steel tube. Taking the steel pipe’s Hazen-Williams average roughness coefficient C as 100 and the C value of fiberglass pipe as 150. As a result, the 12-inch FRP pipe and 14-inch steel pipe have the same flow rate. In other words, under the same pipe diameter condition, the flow rate of the FRP pipe is 36% larger than that of steel pipe.

6. Energy consumption comparison

As the steel pipe’s roughness coefficient C decreases with the years, its energy consumption will also increase. The energy consumption of steel pipelines is much higher than the FRP pipelines. There are two main reasons. One is due to the oxidation of the steel pipe, electrochemical corrosion, and other factors. The internal wall is scaled, which increases resistance and energy consumption. The second is that in the case of new pipes, FRP pipes are smoother than steel pipes. It is worth mentioning that in the last few years of pipeline life, the power of the FRP pipeline doesn’t change. But, the pumping power required for steel pipelines increases from 25 to 60 horsepower.

Now compare the energy consumption according to the same flow rate. Suppose that the daily flow is 60,000 cubic meters, the total length of pipes which transport tap water is 10 kilometers. The dynamic viscosity coefficient is 1.2*10-6, and the slope height is zero. Among them, the absolute roughness of the steel tube is 1.65mm on average. Then, the head of the FRP pipe is 30.85m, while the head of steel is 58.62m. As a result, the energy consumption of steel tubes is 1.9 times that of FRP tubes. This means that later costs will increase while the pipeline is running.

7. Water quality

The lining of FRP pipe is made of food-grade resin. So this can ensure that the water quality meets the national standard (JC586-1995). And, we can use it to transport and store drinking and domestic water that contains chlorine. In addtion, in the dark, the fiberglass reinforced palstic duct is not easy to grow microbes. Thus, fiberglass tubes buried underground can further ensure the tap water quality.

Because metal tubes must be coated with painting. GB13295-91 standard has made strict regulations on it. First of all, paints should be insoluble in water and not cause it to smell. Harmful substances in paints should comply with the relevant rules of the Ministry of Health for drainage. Besides, the wall of steel pipes is too rough to achieve the same smoothness as the inner wall of the FRP pipe. After long time use, it will also cause corrosion, growth of microbes and scaling, which affect water quality.

FRP duct manufacturers

8. Anti-leakage performance and the water hammer resistance

Fiberglass tube adopts double ring rubber seal to connect. During installation, we make the pressure test at the connection place. It ensures that the joint sealing performance is 100% qualified.

In addition, FRP is a highly dense composite material. The FRP body won’t leak water from the inside (such as the sewage that leaks out affects the farmland). Besides, it is impossible to seep from the outside (such as sewage outside the pipe Infiltration will affect water quality). The steel pipe has higher requirements for the working environment during welding. Due to the constraints of site conditions during field construction, it is difficult to guarantee the welding quality. Therefore, the sealing reliability of the welded joints of steel pipes is not as good as that of FRP pipes.

Pipe burst is the outgoing line at the weld of steel pipe. Glass fiber reinforced plastic sand pipe had high strength and good ductility. The water hammer and instantaneous over-pressure will not damage it. Therefore, it can be concluded that the impermeability of the FRP pipe is much better than that of steel pipe.

9. Wide applicability

The duct systems include FRP pipes, FRP dampers, and FRP electric valves. Due to the fiberglass insulation, we use reinforced plastic FRP products in lots of fields. For example, air duct, air conditioning covers, and external insulation. Fiberglass insulation is particularly great in waste water treatment, odor control and fume exhaust air duct systems. Now, the national environmental protection awareness continues to improve, the relevant policies introduce. The trend that traditional pipe system changes into FRP duct system is obvious day by day. The excellent insulation of FRP products also has great effects in the electrical field, such as HVAC system and insulation pipe protection. HVAC system can change the temperature in the room. So the air conditioning has the function of refrigeration and residential heating. All these benefit from the fiberglass insulation and thermal insulation features of FRP pipes.

10. Frost resistance

FRP pipe is a kind of highly flexible pipe. It has a high elongation at break, good elasticity, and low thermal conductivity. Thus, it belongs to non-metallic thermal insulation materials. Besides, the glass fiber reinforced plastic FRP has high tensile strength. Even the full water in the pipe is completely frozen, there will not be frost cracking.
As FRP duct manufacturers, our fiberglass duct wrap is not easy to damage. Under normal circumstances, 1/3 ~ 1/2 of glass fiber reinforced plastic pipes buried in cold areas will not affect the use in the frozen layer.

11. Resistance to deformation and uneven settlement of the foundation

The FRP pipe not only has enough rigidity resistance to external loads and deformation but also has a certain flexibility. The rotation angle of the tube of the DNl800mm pipe interface can reach 1.5 °. But, steel pipes are rigid connections. They are prone to shear failure or weld cracking due to external forces or uneven settlement. So, FRP pipes have a stronger resistance to deformation and uneven settlement than steel pipes. Also, they have a stronger resistance to external forces such as earthquakes.

12. Flexibility and maintainability of accessories

We cannot seperate the pipe from the connection elbow and the air valve. Especially when customers request to provide FRP pipe kits, FRP pipes have more advantages. First of all, molds investment will be much lower than the cost of sheet metal ducts of the past. It has design flexibility, can meet the needs of small quantity and short delivery period. Secondly, our FRP products have excellent external insulation properties and strong corrosion resistance. They can be widely used in FRP ductwork.

FRP is a kind of maintenance-free pipe. The fiberglass duct wrap is rigorous, and it is uneasy to be damaged. If the glass fiber reinforced plastic pipe is damaged due to external factors, suppliers will also solve the problem in the shortest time without affecting the water supply. But, once the steel pipe is damaged or burst, it is challenging to repair.

2019-12-30T07:05:48+00:00By |FRP application|