After years of serving corrosion-related industries, Fibrex noticed there seemed to be no easy approach to selecting and designing fiberglass reinforced plastic (FRP) pipe (also known as GRP pipes). Most plants have worked with fabricators and engineers to custom design all fiberglass pipe (FRP) equipment. Yet there is considerable cost and effort to custom design fiberglass pipe or a fiberglass pipe system and it is not always necessary. Fibrex has found there are many applications where a standard FRP pipe product will meet all of the requirements. That&#;s why Fibrex has developed a standard pipe product line called IntegraLine.
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IntegraLine is a standard production fiberglass pipe with custom corrosion resistance. Simple to specify and select, this fiberglass pipe is ideal for new system installation or replacement of existing pipe. IntegraLine pipe will meet many of the applications and life-span requirements at your plant or facility.
For special design requirements, Fibrex also offers custom fiberglass pipe solutions. Custom fiberglass pipe solutions may require thicker corrosion or abrasion barriers with different resins. Also, heavier structural laminates and special glass reinforcements are available to meet installation and temperature requirements. Fibrex can provide design recommendations for a proposed installation.
And because Fibrex understands the industries we serve, Fibrex products are designed to meet the most demanding and specialized conditions at each site. In standard pipe, custom pipe, special header systems, duct or stacks, Fibrex delivers long-term corrosion solutions and absolute maximum product life. We call this &#;performance-based manufacturing.&#;
IntegraLine fiberglass pipe ( fiberglass reinforced plastic pip &#; FRP) is designed to be &#;user friendly.&#; The resin, glass reinforcement
materials and composite construction were selected to provide consistent corrosion resistance for the majority
of chemical applications for which FRP pipe is considered appropriate. There remain certain extreme chemical services
for which special construction and alternative resins should be considered. Fibrex can advise if this is required for
your application.
IntegraLine pipe utilizes a heavily resinated exterior coat containing an ultraviolet stabilizer to impart long term
resistance to the effects of sunlight and other weathering elements. Should pipe become weathered after many years in
particularly severe environments, the exterior can be sanded and resin coated or painted.
Pigmented exterior gel coats are not used on IntegraLine pipe in order to take advantage of the natural translucency
of FRP. Visual inspection of the pipe, both new and after years of service, is more reliable with a &#;natural&#; laminate.
Additionally, the liquid contents can often be observed in the pipeline&#; sometimes a process control advantage.
When special color coding is required, however, this can be provided at a nominal added cost and slightly longer
delivery time.
The high tensile elongation properties of the vinyl ester resins utilized in IntegraLine pipe impart a superior
toughness to the pipe enabling it to resist cracking and crazing of the resin when subjected to heavy design loads.
In addition to high fatigue resistance, this toughness also provides a safety factor against impact damage during
shipping and installation.
IntegraLine pipe is manufactured with a premium vinyl ester resin as the standard production resin. Other vinyl ester resins specified by the customer are available, however delivery lead times will generally be longer. Epoxy vinyl ester resins are
premium corrosion resistant resins. At both room and elevated temperatures, these resins offer resistance to a broad range of acids, alkalis, bleaches and solvents making them the appropriate choice of resins in many chemical processing industry applications. These
resins, when properly formulated and cured, comply with FDA regulation 21 CFR 177. covering materials intended
for repeated use in contact with food. Specific chemical resistance information can be found in the Chemical Resistance
and Engineering Guides, available from FIBREX or directly from the resin manufacturers.
A &#;C&#; glass (chemical grade) veil is provided on all surfaces exposed to corrosive media. Fiberglass used in
all subsequent layers of the laminate has excellent electrical resistivity, high tensile strength, moderate thermal
conductivity and is noncombustible. The basic types of fiberglass materials used; mat, woven roving and continuous
strand, are selected for their physical properties, manufacturing characteristics and the chemical resistance of the
laminate resulting from their use.
The corrosion barrier of IntegraLine pipe is nominally 100 mils thick and is comprised of 70% to 80% resin. This
highly resinated laminate is reinforced by one layer of &#;C&#; glass veil followed by two layers of randomly oriented fiber
strand mat.
Straight Pipe
IntegraLine pipe is manufactured by the filament winding process utilizing continuous fiberglass strand wound in a
helical pattern at a nominal 55 degree wind angle to produce an optimum combination of hoop and axial properties
for most typical applications. The high glass content resulting from the filament winding process imparts excellent
strength characteristics to the laminate providing superior protective structural backup to the resin rich corrosion barrier.
Fittings
IntegraLine pipe fittings are manufactured utilizing a highly efficient contact-molded laminate consisting of
alternating layers of glass fiber strand mat and bi-directional woven glass roving. The high glass content resulting
from the specific laminating process used for IntegraLine pipe fittings permits the wall thickness of this hand-layup
process to closely approximate the wall thickness of filament wound straight pipe in equivalent pressure rated classes.
Click Here to Print the Fiberglass Pipe Manual for Chemical Plants
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Click Here to Learn More About Fiberglass Pipe IntegraHeader &#; The Long-Term Chlorine Header Solution
Fiberglass-reinforced thermoset plastic pipe (or FRP pipe) is often the material of choice for corrosive process systems. This is due to a variety of factors:
An evaluation of the total cost of the system, including all of the above variables, often demonstrates cost savings for fiberglass FRP pipe vs. steel, with even greater cost savings over alternative alloy constructions.
PVC Polyvinyl Chloride CPVC Post Chlorinated PVC PP-H Polypropylene Homopolymer PP-R Polypropylene Random Copolymer PVDF PVDF Polyvinylidene Fluoride (Kynar) ECTFE Ethylene Chlorotrifluoroethylene (Halar) ETFE ETFE Ethylene Tetrafluoroethylene (Tefzel) MFA Perfluoroalkoxy Methylvinylether (Hyflon) FEP Fluorinated Ethylene Propylene (Teflon) PFA PFA Perfluoroalkoxy Copolymer (Teflon)Composites USA manufactures hand lay-up and filament wound FRP pipe in all commercially available resin systems, including polyester, vinyl ester, furan, phenolic, and epoxy thermoset resin systems. Resin systems as well as reinforcements are tailored for specific applications. FDA compliant materials are available, as are flame retardant and dual containment FRP pipe systems.
The design of any pipe system must take into account many different factors. Corrosion allowances, operating pressure, vacuum, temperature, abrasion, flammability, electrical conductivity are just a few of the characteristics of the desired system that must be considered and addressed with proper choice of materials of construction. Mechanical design evaluates the strength of the pipe, the requirements for supports, thermal expansion compensation, burial loads, wind, snow and seismic considerations. Laminate analysis, and when required, finite element analysis is a part of the overall fiberglass FRP pipe design solution.
The system analysis is completed using conventional techniques, substituting appropriate physical properties for the fiberglass system specified. A typical Specification for fiberglass pipe is also available in this catalog binder.
Fiberglass FRP pipe design is greatly influenced by the process design. The process will generally determine the required corrosion liner resin selection and thickness, the design and operating temperatures, pressures, and vacuum.
Following a determination of the above criteria, the mechanical design of the fiberglass pipe laminate structure begins. The laminate design will balance the economic benefit of various resin and reinforcement characteristics to meet the specified process design. Finally, the overall system is evaluated for proper support, thermal expansion stresses, and compliance with appropriate codes.
In the sections that follow, key relationships for fiberglass FRP pipe are highlighted. At the end, a life cycle cost comparison is shown to demonstrate the cost effectiveness of fiberglass pipe vs. steel.
The anticipated concentration limits of the process stream needs to be evaluated for chemical corrosion resistance at temperature. Specific recommendations should be made by the resin manufacturer whenever possible. Fiberglass pipe is not subject to many of the corrosion problems associated with metal pipes, such as galvanic, aerobic, intergranular corrosion or pitting.
As noted above, specific recommendations should be made whenever possible. Fairly extensive data exists for a number of resin systems, while corrosion data is relatively scarce for others. General-purpose polyester resins should usually be avoided for chemical process piping. Corrosion grade polyesters provide an excellent value for many mildly corrosive systems. Vinyl ester resins provide additional corrosion resistance to strong oxidizing solutions while offering better mechanical strength and temperature resistance than the polyesters. Extensive corrosion resistance information is available for these resins.
Furan, phenolic and epoxy resins generally offer additional solvent and temperature resistance, sometimes sacrificing resistance to strong oxidizers. Corrosion data for these resins is generally more limited than for the polyester and vinyl esters, but particularly for conveying organics in acid environments, they can offer significant improvements. For all the above, resin catalyst and post cure should follow the resin manufacturer&#;s recommendations.
The corrosion liner refers to the inside portion of the pipe laminate including resin reinforced with a corrosion veil or veils, and chopped strand fiberglass mat. The veil(s) may be either a corrosion grade fiberglass (C-glass), or an organic veil such as polyester (Nexus), ECTFE (Halar) or graphite. An organic veil would be used in environments known to attack glass, such as sodium hydroxide, hydrofluoric acid, etc.
The veil when cured will vary from 0.010&#; to 0.027&#;, at 10% to 50% reinforcement for C-glass or Halar, respectively, with polyester in between. The fiberglass chopped strand E-glass mat that backs up the veil forms the balance of the corrosion liner. This mat generally cures to 30% +/- reinforcement. The final corrosion liner may vary from as little as 0.040&#; for a C-veil and one layer of 1.5oz/ft2 chopped strand mat, to over 0.250&#;, depending upon the customer&#;s understanding of the corrosive properties of the fluid contained. The standard (SPI) corrosion liner is 0.100&#;, while many pulp and bleach manufacturers routinely use liners twice that thickness.
To avoid confusion, the corrosion liner and the corrosion allowance should be specified. Some specifications allow the use of the corrosion liner to be used in calculating required overall pipe wall thickness. Other specifications require the liner be treated as a sacrificial corrosion allowance and not to be used in any of the pipe structural calculations for pressure and vacuum handling capability.
The temperature handling capability of the various resin systems depends upon the corrosive nature of the process fluid. In general, corrosion grade isophthalic polyesters are suitable up to a temperature of approximately 120° &#; 170°F (50° &#; 75°C), while vinyl esters are suitable up to a temperature of 170°-210°F (75°-100°C). These ranges are general only. The specific system must be evaluated in light of the corrosion requirements, and later on for the mechanical requirements (supports, expansion, fatigue, etc.). Furan, phenolic and epoxy resins may offer slightly higher temperatures depending upon the system.
Fiberglass pipe is easily designed for the specific pressure or vacuum requirements of the system. It is common to specify pipe requirements by the design pressure of the system, using multiples of 25 PSIG (i.e., 25, 50, 75, 100, 125, or 150 PSIG design). Higher pressures can be accommodated when required. Fiberglass pipe is usually designed with a factor of safety = 10 for internal pressure and a factor of safety = 5 for vacuum.
When required, additives such as ceramic fillers can be incorporated into the fiberglass pipe corrosion liner to enhance abrasion resistance. These systems have been used for many years in power plant and other services. In addition to fillers, additional layers or styles of veils may be considered.
Structural Design Principles:
Due to the wide variety of available standards, there is no universal set of criteria for designing fiberglass pipe. The following equations and constants may be used in the mechanical design of fiberglass pipe. Acceptance criteria are based upon the most current revision of ASTM D- (Standard Specification for Filament Wound Reinforced Thermosetting Resin Pipe):
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Poisson Ratio:
Ratio of the axial strain to the hoop strain. Usually reported as 0.30 for laminates under discussion.
Density:
0.055 lb/in , or 1.5 gm/cm .
Specific Gravity: 1.5
Friction Coefficient: Surface Roughness: 150-160 (Hazen-Williams)
Surface Roughness: 1.7 x 10 ft (Darcy-Weisbach/Moody)
Internal Pressure Rating:
Based upon the hydraulic design basis for static or cyclic conditions in accordance with ASTM D-. The design basis is the hoop stress or strain that results in an estimated life of 100,000 hrs or 150 million cycles for static or cyclic conditions, respectively. Service factors are applied, usually 0.8 &#; 1.0 for cyclic and 0.50 0.56 for static conditions.
Thermal Conductivity:
Thermal Expansion:
May vary in the hoop and axial directions. Typical axial expansion for filament wound pipe at a 55° wind angle-5 is 1.1 &#; 1.5 x 10 inch/inch/°F (or approximately twice that of steel).
Thermal expansion in piping systems may be accomplished by guides, expansion loops, mechanical expansion joints, anchors or combinations of the above. Use of these tools is similar to steel pipe design.
Fiberglass pipe has a very low modulus relative to steel (<5% of steel). This significantly improves the pipe&#;s ability to handle expansion and contraction loads.
There are several tables available which specify the design modulus for calculating this expansion/contraction force. Fiberglass reinforced pipe is an anisotropic material which results in different modulus values for tensile, bending and compression, and vary again depending upon the resin, reinforcement and reinforcement orientation used. Care must be taken to insure the appropriate modulus is used, and a ply by ply laminate analysis is generally appropriate. An example of these tables is shown in our Pipe Specifications.
Supports and Guides:
Proper support of fiberglass pipe is very similar to steel pipe support. Several key points to consider are the following:
Guides should allow movement in the axial direction only. Care should be taken to provide protection at all contact points using a steel or fiberglass saddle bonded to the pipe. Anchors must restrain the pipe against all forces. Anchors break the pipe system into component systems, which are then analyzed for expansion. Pumps, valves and other equipment can sometimes function as an anchor. Additional anchors may be required, and it is good practice to include them on at least 300 ft straight run intervals.
Guides and anchors function as supports. Supports are required to prevent excessive pipe deflection. For fiberglass pipe, a mid-span deflection of no greater than 0.5 inch generally results in acceptable bending stresses. If the deflection exceeds 0.5 inch, a safety factor on the bending stress of 8:1 is usually sufficient.
Buried Pipe:
Buried pipe design differs from above ground design in many respects. Most of these requirements are spelled out in Appendix A of AWWA Standard C-590-88. Additional design details including pipe size, surge pressure, working pressure, service temperature, soil conditions, soil specific weight, depth of cover, and traffic loads will be required. Note that while the previous discussions have used ASTM service design factors of less than or equal to 1.0 the AWWA C-950 specifies design factors which are the reciprocal of the service design factors and are always greater than or equal to 1.0.
Contact Composites USA for specific guidance in this area.
Joining Pipe:
Composites USA pipe may be assembled using either butt and wrap (fiberglass lay-up) or flanged construction. Factory subassembly is available and recommended for branch connections. The procedures for butt and wrap joining are similar to those shown for Class 1 duct, also in this catalog binder. Thickness and width of the joints will vary depending upon the pressure classification and liner requirements of the system.
Composites USA fiberglass pipe offers significant hydraulic advantages over steel pipe for the following reasons:
Fiberglass pipe has a smoother internal surface than steel pipe, with a Hazen-Williams roughness coefficient of 160 when new, or 150 used. Steel pipe, on the other hand, has a Hazen-Williams roughness coefficient of 120 when new, or 65 used. The far greater loss in smoothness for the steel pipe is due to scale build-up on the steel pipe. Note that even when the fiberglass pipe is used, it is still much smoother than new steel.
Composites USA, as do many manufacturers of fiberglass pipe, provide internal diameters for their pipe and fittings which match the nominal pipe size. Thus, an 18&#; diameter fiberglass pipe would have an 18&#; internal diameter, while an 18&#; diameter schedule 40 steel pipe would have a 16.88&#; internal diameter, providing only 88% of the flow area of its fiberglass counterpart.
These key differences are directly related to substantial cost savings available with the use of fiberglass pipe as shown below.
The first cost (material) purchase price of fiberglass pipe and fittings for typical installations has been variously reported as 0.75 &#; 2 times the price of similar diameter stainless steel pipe systems. But first cost is only one piece of information in evaluating overall system cost. An evaluation of installed plus operating cost of piping systems usually generates a compelling case for the use of fiberglass pipe.
In addition to the material purchase price, evaluation of the total system cost considers the following:
Pipe Installation Cost
Pipe Operating Cost
Total System Life Cycle Cost
Pipe purchase cost differentials can vary widely depending upon factors such as costs of stainless steel and pipe specification requirements. It is however, fairly straight forward for the consumer to obtain pricing for comparison. The rest of the factors are somewhat less straight forward and some additional information follows.
The standard method for joining Composites USA manufactured fiberglass pipe is with either flanged ends or butt and strap connections. Butt and strap is the industry method of choice for most severe corrosion services, and involves butting the fiberglass ends together and completing a wet fiberglass lay-up (strap) over the joint area. Although this is a procedure that takes skill and training to successfully complete, it is generally easier to learn than welding stainless steel.
The time required to cut, prepare and weld the two materials are as follows (budget purposes).
One of the key reasons to consider fiberglass pipe for any traditional carbon steel systems is its generally lower cost to operate, or horsepower requirements.
The discussion in the previous section called attention to the larger flow area generally available with fiberglass pipe (12% greater of the 18&#; diameter example given). This is one key reason why fiberglass pipe results in lower pumping costs. A second reason is the lower coefficient of friction for fiberglass pipe, 25% lower for new systems and twice as low for aged systems.
This fact allows the system designer to choose between down sizing the line in (in fiberglass) or taking advantage of lower operating costs. These costs are usually significant and can be estimated as follows:
For the 18&#; diameter pipe mentioned above, assume 6,000 gpm traveling through a 2,000 ft long straight pipe system. Costs will be estimated for one year only (year #3). The process is repeated for each year of the estimated useful life of the system. Use of the HazenWilliams relationships is used in the analysis below. Other formulas, such as the Colebrook equation may be used and should yield similar results.
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