The full form of FRP is fiberglass reinforced plastic that 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. \n\n\n\nApplications of FRP Pipes\n\n\n\nDue 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:\n\n\n\nPotable Water and desalination industriesChemical, Petrochemical, Oil & Gas industries.Ducting and Vent pipingIrrigation and Sanitary servicesWater distribution and transmissionSlurry pipingPower plants, etc.\n\n\n\nProperties of FRP Piping\n\n\n\nThe main properties that make FRP Pipes an ideal selection for various industries worldwide are\n\n\n\nExcellent corrosion resistanceExcellent strength to weight ratio. Note that, the strength to weight ratio of FRP pipes are higher than steel or other metallic pipes.Light weight which makes easy for handling and transportation.Dimensional stabilityNon-toxicityLow coefficient of friction (>25% better than steel) that ensures excellent flow characteristics.Good abrasion resistanceSuitable for both aboveground and buried pipingResistance to biological attacks like bacteriaNon-conductive to electricity andLow maintenance cost\n\n\n\nTypical mechanical properties of FRP piping system are provided in the table below:\n\n\n\nMechanical 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\n\n\n\nJoining of FRP Pipes\n\n\n\nAs 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.\n\n\n\nUnrestrained FRP Pipe Joints\n\n\n\nJoints 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.\n\n\n\nRestrained FRP Pipe joints\n\n\n\nSuch pipe joints are capable of withstanding both the 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.\n\n\n\nNote that FRP pipe joint tightness must be ensured following ASTM D4161.\n\n\n\nFRP Pipe Fittings\n\n\n\nVarious FRP pipe fittings are available for proper piping layout needs. Common FRP pipe fittings are\n\n\n\nLong radius and short radius FRP Pipe Elbows (22.5 Degree, 30 Degree, 45 Degree, 60 Degree, 90 Degree, 180 Degree)Tee Connections (Equal Tee and reducing Tee)FRP Pipe flangesSteel backing flangesFlanged elbowsSmooth flow reducing elbowSpecial radius bendLateral connectionCross connectionsWye ConnectionsReducers (Eccentric and Concentric)Flanged reducers\n\n\n\nCodes and Standards for FRP Pipes\n\n\n\nFrequently used Codes and Standards that govern the FRP piping details are\n\n\n\nISO 7370ANSI\/AWWA C950AWWA M45ISO 14692AWWA C590ISO 10467BS 5480ISO 10639ASTM D2996, ASTM D2997, ASTM D5421, ASTM D4024, ASTM D5685\n\n\n\nSpecification of FRP Pipes\n\n\n\nWhile ordering FRP pipes the following data need to be provided to the vendor:\n\n\n\nPipe DiameterDesign and Operating temperature of the service fluid.Design, operating, Surge, vacuum, test pressures.Live loads in case of buried piping.Maximum\/minimum buried depth and trench Widths.Details of Soil properties and trench preparation.\n\n\n\nSupporting of FRP Piping System\n\n\n\nFRP 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. Manufacturer's guidelines with respect to the supporting shall be followed. Usually, clamped supports with an elastomeric pad are used for support.\n\n\n\nFig. 1: FRP Pipe Supporting\n\n\n\nDrawbacks of FRP Piping\n\n\n\nThe main drawbacks of FRP piping systems are\n\n\n\nFRP pipe is not recommended for carrying fluid with temperature more than 1000 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.\n\n\n\nFRP vs GRP: Difference between FRP and GRP\n\n\n\nFRP 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.\n\n\n\nFRP vs Steel: Differences between FRP and Steel\n\n\n\nAs 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. \n\n\n\nSteel pipes are isotropic while FRP pipes are anisotropic and the properties changes 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. Usual factor of safety in the design of FRP pipes varies in the range of 5 to 10.\n\n\n\nOther major differences between FRP and Steel pipes are provided in Table 2 below:\n\n\n\nPropertyFRPCSRemarksDensity1850 kg\/cu.m7800 kg\/cu.mLoads on support is less in the case of FRP pipe as compared to Steel. Handling and transportation of FRP are easier than Steel pipes.Co-eff 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 case of FRP Piping system.* This value may change from vendor to vendorModulusAxial= 12000 N\/sq.mmElastic= 211365 N\/sq.mmConsiderable difference in the strength of FRP & CS. Anchor loads are less in FRP Pipes as compared to steel pipes.Shear= 11400 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 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\n\n\n\nFRP vs HDPE: Differences between FRP and HDPE Pipes\n\n\n\nThe main differences between FRP and HDPE pipes are listed in Table 3 below:\n\n\n\nFRP PipeHDPE PipeFRP is Orthotropic composite materialHDPE is isotropic material.The cost of FRP pipe is very highThe cost of HDPE pipe is considerably lower than FRP Pipes.Lower thermal expansion co-efficientThe thermal expansion coefficients of HDPE pipes is 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.Strength and Elastic modulus for FRP pipes are higher than HDPELower strength and elastic modulus.Easy installation at 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 \n\n\n\nThe 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.