FRP pipe: an effective solution for wastewater management

Fibre-reinforced plastic (FRP) is a composite material composed of a polymer matrix strengthened by fibres, also referred to as fibre-reinforced polymer.

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Commonly employed fibres include carbon, glass, basalt or aramid. In some cases, other fibres like wood, asbestos, and paper have been utilised. While vinyl ester, polyester, epoxy thermosetting plastics are used as matrix materials. In some cases, phenol formaldehyde resins are also used.

Fibreglass-reinforced pipes are experiencing a rapid surge in demand because they play a vital role in the industrial sector. These pipes, made from FRP, are non-metallic and crafted by continuously wrapping fibreglass filament saturated with a specialised combination of epoxy resin and curing chemicals. Their applications range from piping systems to tankers, and various vessels across numerous fields and industries. The global FRP pipe industry is gaining momentum owing to an expansion of the building and construction sector and the benefits of FRP pipe in the construction domain.

Features of FRP pipes:

&#; Lightweight

FRP pipes, designed from a combination of 1/10 P.S.C., 1/5 steel, and 1/8 C.I., exhibit a reduced strength-to-weight ratio compared to alternative materials. Their lightweight construction enables easy handling, installation, modification, and repair of FRP pipes.

&#; Non-corrosive

FRP pipes inherently possess corrosion resistance. In many cases, fibreglass-reinforced plastics stand as the sole material capable of withstanding certain parameters. Additionally, their corrosion resistance, typically coupled with cost efficiency, positions them as the most viable solution. The corrosion resistance of Fibreglass Reinforced Plastic pipes depends on both the overall resin content and the specific resin employed in the pipe's laminate. Thus, a higher resin content equals to increased resistance against corrosion.

FRP pipes offer an excellent solution for transporting corrosive wastewater and sewage. Their smooth inner surface effectively facilitates the flow of various fluids. Corrosion resistance is a crucial attribute in these applications.

&#; Flexibility

FRP pipes offer versatility in shaping various equipment pieces or configurations using permanent or temporary molds. For instance, constructing ductwork with FRP pipes is highly feasible as it enables the production of different types of rectangular transitions, Tee inlets, circular transitions, flanges, and elbows at a minimal expense. Additionally, Fibreglass Reinforced Plastic pipes are a suitable option for lining both new and existing structures.

Computer software programmes have significantly improved the design of FRP systems. These programmes include various functionalities such as analysing gas flow, chemical composition, liquid flow, and thrust blocks, and providing installation information.

Recent developments transforming the FRP pipe industry:

RPS Composites introduced a robust and durable joint specifically designed for FRP (Fibreglass Reinforced Plastic) piping systems.

RPS Composites, based in Franklin, Ohio, US, has introduced the RPS Grooved Adapter, specially designed for use in combination with RPS fibre-reinforced polymer (FRP) piping systems. This adapter is designed for use with a Victaulic Style 296-A coupling, resulting in a sturdy and dependable joint for FRP piping. As per the RPS, the most appealing feature of the Grooved Adapter is its ease of use, enabling coupling or uncoupling within minutes without requiring any specialised tools or training. Specifically designed for mild corrosive environments such as water, seawater, and wastewater, the RPS Grooved Adapter offers practicality and convenience in its application.

The RPS FRP adapters have undergone rigorous testing and meet the ASME NM.2- Proof of Design qualification test standards. These tests include static pressure, cyclic pressure evaluations, and hydrostatic strength testing.

CPP has successfully installed the tallest Fibre Reinforced Polymer (FRP) stack liner for the Bangladesh-India Friendship Power Company

CPP (Chemical Process Piping), a company specialising in industrial piping solutions producing GRP and FRP-based pipes, has introduced an FRP stack in the FGD (Flue Gas Desulfurisation) plant established by BIFPCL (Bangladesh India Friendship Power Company). This joint venture operates on a 50:50 partnership between the Bangladesh Power Development Board and the National Thermal Power Corporation.

CPP has accomplished Phase I of the Maitree Super Thermal Power Plant project in collaboration with BHEL and Simplex in Bangladesh. Marking a significant achievement, CPP stands as the pioneering entity in this sector by successfully constructing an 800 ft FRP stack for the MW coal-fired power station located in Rampal, Bangladesh. This accomplishment positions CPP as the foremost FRP manufacturer in this region to employ vertical winding technology for filament winding the FRP stack, a pioneering approach adopted for their project in Bangladesh. The project itself represents an environmentally friendly initiative, leveraging supercritical technology for the thermal power plant.

To sum up, the global FRP pipe industry is experiencing growth due to the advantages of these pipes in the construction sector and the rapid growth of the construction and building sector. The potential of FRP pipes in wastewater management will present remunerative growth opportunities to the market in the upcoming years.

Read the article online at: https://www.worldpipelines.com/special-reports//frp-pipe-an-effective-solution-for-wastewater-management/

The full form of FRP is fiberglass-reinforced plastic which is a composite material consisting of a polymer matrix reinforced with fibers. So, an FRP pipe is a pipe manufactured of FRP material by contact molding or filament winding method. Various types of resins like thermosetting polyester, epoxy, phenolic resin, etc are used to get specific FRP pipe properties in the final product. The most widely used reinforcement is the glass fiber &#;E-glass&#;. As a corrosion-resistant alternative to metallic piping, the FRP piping system has found worldwide application. By selecting FRP as the pipe material, the need for internal lining, external coating, and cathodic protection can easily be eliminated. FRP piping system is available in a wide range of sizes starting from 1 inch to 144 inches.

Applications of FRP Pipes

Due to its high durability, corrosion resistance, and moderate strength, the use of FRP pipes is increasing day by day. FRP piping systems are used in various industries like:

• Potable Water and desalination industries
• Chemical, Petrochemical, Oil & Gas industries.
• Ducting and Vent piping
• Irrigation and Sanitary services
• Water distribution and transmission
• Slurry piping
• Power plants, etc.

Properties of FRP Piping

The main properties that make FRP Pipes an ideal selection for various industries worldwide are

• Excellent corrosion resistance
• Excellent strength-to-weight ratio. Note that, the strength-to-weight ratio of FRP pipes is higher than steel or other metallic pipes.
• Lightweight which makes it easy for handling and transport.
• Dimensional stability
• Non-toxicity
• Low coefficient of friction (>25% better than steel) that ensures excellent flow characteristics.
• Good abrasion resistance
• Suitable for both aboveground and buried piping
• Resistance to biological attacks like bacteria
• Non-conductive to electricity and
• Low maintenance cost

Typical mechanical properties of the FRP piping system are provided in the table below:

Mechanical Properties of FRP PipeTypical RangeTensile Strength14 to 550 MpaTensile Modulus3.5 to 34.5 GpaFlexural Strength28-480 MpaFlexural Modulus6.9 to 34.5 GpaPoisson&#;s Ratio0.3Thermal Co-efficient14 to 54 mm/mm/0CSpecific gravity1.2 to 2.3Compressive Strength69-275 MpaTable 1: Range of Mechanical Properties for FRP Pipe

Joining of FRP Pipes

As the FRP pipe lengths are limited by transportation and handling, they are required to be joined. Also, various FRP Pipe fittings need to be joined as per the requirement. The joining system of the FRP pipe should be such that it does not leak for the intended service condition at the operating pressure. Depending on the specific joint configuration and design conditions, the FRP pipe joints may be restrained or unrestrained.

Unrestrained FRP Pipe Joints

Joints that can withstand the internal pressure but can not withstand the longitudinal tensile loads are known as Unrestrained FRP Pipe joints. Examples of such joints are Coupling joints, bell and spigot joints, mechanical coupling joints with elastomeric seals, flanged joints, butt joints with laminated overlay, etc.

Restrained FRP Pipe joints

Such pipe joints are capable of withstanding both internal pressure and longitudinal tensile loads. For these joints, supplemental restraining elements are added to restrict the longitudinal loads. Threaded joints, bell, and spigot joints with laminated overlay or adhesive bonds are examples of Restrained FRP pipe joints.

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Note that FRP pipe joint tightness must be ensured following ASTM D.

FRP Pipe Fittings

Various FRP pipe fittings are available for proper piping layout needs. Common FRP pipe fittings are

• Long radius and short radius FRP Pipe Elbows (22.5 Degrees, 30 Degrees, 45 Degrees, 60 Degrees, 90 Degrees, 180 Degrees)
• Tee Connections (Equal Tee and Reducing Tee)
• FRP Pipe flanges
• Steel backing flanges
• Flanged elbows
• Smooth flow-reducing elbow
• Special radius bend
• Lateral connection
• Cross connections
• Wye Connections
• Reducers (Eccentric and Concentric)
• Flanged reducers

Codes and Standards for FRP Pipes

Frequently used Codes and Standards that govern the FRP piping details are

• ISO
• ANSI/AWWA C950
• AWWA M45
• ISO
• AWWA C590
• ISO
• BS
• ISO
• ASTM D, ASTM D, ASTM D, ASTM D, ASTM D

Specification of FRP Pipes

While ordering FRP pipes the following data need to be provided to the vendor:

• Pipe Diameter
• Design and Operating temperature of the service fluid.
• Design, operating, Surge, vacuum, and test pressures.
• Live loads in case of buried piping.
• Maximum/minimum buried depth and trench Widths.
• Details of Soil properties and trench preparation.

Supporting of FRP Piping System

FRP piping systems must be supported properly to avoid excessive sagging. Maximum acceptable sagging is the lower of 12.5 mm or 0.5% of span length. The manufacturer&#;s guidelines with respect to the supporting shall be followed. Usually, clamped supports with an elastomeric pad are used for support.

Fig. 1: FRP Pipe Supporting

Drawbacks of FRP Piping

The main drawbacks of FRP piping systems are

• FRP pipe is not recommended for carrying fluid with temperatures more than C
• Slight degradation from UV rays is found to occur which can be reduced by using pigments, dyes, UV stabilizers, fillers, etc in the resin system.

FRP vs GRP: Difference between FRP and GRP

FRP stands for fiber-reinforced plastic while GRP stands for Glass reinforced plastic. So, from the name, it is clear that there is a change in the reinforcing fiber. But, both FRP and GRP are normally used to indicate the same plastic piping products.

FRP vs Steel: Differences between FRP and Steel

As FRP Pipes have superior corrosion resistance capabilities and over the long term it is economic, Steel pipes are replaced by FRP pipes. So, in this section, it will be great to find the differences between FRP and Steel.

• Steel pipes are isotropic while FRP pipes are anisotropic and the properties change with respect to direction.
• FRP pipes are more flexible than Steel pipes due to the lower modulus of elasticity.
• FRP piping systems are designed considering a higher factor of safety than steel piping. The usual factor of safety in the design of FRP pipes varies in the range of 5 to 10.

Other major differences between FRP and Steel pipes are provided in Table 2 below:

PropertyFRPCSRemarksDensity kg/cu.m kg/cu.mLoads on support are less in the case of FRP pipe as compared to Steel. Handling and transportation of FRP are easier than Steel pipes.Co-efficient of thermal expansion27 X 10-6 mm/mm 0C11 X 10-6 mm/mm 0CExpansion is almost 2.5 times of Carbon Steel Pipe. So more thermal growth in the case of the FRP Piping system.* This value may change from vendor to vendorModulusAxial= N/sq.mmElastic= N/sq.mmConsiderable difference in the strength of FRP & CS. Anchor loads are less in FRP Pipes as compared to steel pipes.Shear= N/sq.mmTensile Strength80-135 MPa456 MPaMechanical Strength is higher for Steel material as compared to FRP.Yield Strength70-135 MPa227 MPaThe yield strength of FRP is lesser than that of Steel.Allowable Stress4,000 PSI to 20,000 PSI20,000 PSIThe strength of the GRE varies drastically and hence proper vendor data is a must.Corrosion resistanceSuperiorInferiorThe corrosion resistance of carbon steel is much lower than that of FRP pipes.JointsThreaded or gluedWeldedFRP joints are to be checked for higher axial loads and pressureTable 2: FRP vs Steel

FRP vs HDPE: Differences between FRP and HDPE Pipes

The main differences between FRP and HDPE pipes are listed in Table 3 below:FRP PipeHDPE PipeFRP is Orthotropic composite materialHDPE is isotropic material.The cost of FRP pipe is very highThe cost of HDPE pipes is considerably lower than FRP Pipes.Lower thermal expansion coefficientThe thermal expansion coefficients of HDPE pipes are extensively higher as compared to FRP pipes.FRP pipes have a comparatively higher temperature range than HDPE PipesLowe temperature rangeFabrication time is comparatively longerQuicker fabrication.The strength and Elastic modulus for FRP pipes are higher than HDPELower strength and elastic modulus.Easy installation at the siteCostly complex equipment is required for installation.Highly skilled professionals are required for site work of FRP piping systemsHDPE pipe works can be done by semi-skilled operators.Much lighter in weight due to lower all thickness even though the density of FRP is normally higher than HDPEHeavier due to higher wall thickness.A fire-retardant version of FRP pipes can be made.HDPE pipes are highly flammableTable 3: FRP vs HDPE

The initial cost of FRP pipes is normally higher than the metallic piping systems. But when comparing the total cost over the complete service life FRP Pipes come as a winner due to their long service life.

Stress Analysis of FRP Piping System

In piping stress analysis guides or flexibility specifications, FRP lines are considered critical irrespective of their sizes. So, a proper stress analysis must be performed to investigate the stresses, loads, displacements, supports, etc to decide if the FRP piping system will work smoothly throughout its design life. I have developed an online course explaining step-by-step procedures for FRP piping stress analysis. You can check it out here.

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