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AWWA-Mpdf - Download as PDF File .pdf), Text File .txt) or read online. AWWA Standards, xvi. Welded Tanks, xvii. Bolted Tanks, xvii. Part I Elements of Steel Water Tanks. Chapter 1 Typical Capacities and Configurations 3. AWWA M ➢“The maximum interval for periodic inspections of the tank interior should normally be 3 years. It is usually advisable to wash out the tank at the.

Awwa M42 Pdf

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Preface, xiii. Acknowledgments, xv. Introduction, xvii. Definitions, xviii. AWWA Standards, xviii. Welded Tanks, xix. Bolted Tanks, xx. Composite Elevated Tanks . AWWA also provides quality improvement programs for water and Third Edition, , M42, Steel Water-Storage Tanks, First #PA Edition, AWWA Standards are not ○ Specifications Tank Industry Consultants. American Water Works Association. AWWA. American Water Works . AWWA M

Electrical properties. Standard fiberglass pipes are nonconductive. Some man- ufacturers offer conductive fiberglass piping systems for applications that require dis- sipation of static electricity buildup when transporting certain fluids, such as jet fuel. Dimensional stability. Fiberglass composites can maintain the critical tolerances required of the most demanding structural and piping applications.

The material meets the most stringent material stiffness, dimensional tolerance, weight, and cost criteria. Fiberglass piping is easy to maintain because it does not rust, is easily cleaned, and requires minimal protection from the environment.

To aid understanding of the performance characteristics of a finished fiberglass pipe, the interrelationship of the system components is outlined in this chapter.

The fol- lowing is a list of terms used in describing the material system. Fiberglass reinforcement. The amount, type, location, and orientation of glass fibers in the pipe that will provide the required mechanical strength. Resin system. Resin selection will provide the physical and chemical properties e.

Following is a brief review of the constituents of fiberglass pipe and how they influ- ence the finished pipe product. Strength increases proportionally with the amount of glass fiber reinforcement. The quantity of the glass fibers and the direction in which the individual strands are placed determines the strength.

This allows for addi- tional design flexibility to meet performance criteria. All fiberglass reinforcement begins as individual filaments of glass drawn from a furnace of molten glass. Sizing can also affect resin chemistry and laminate properties. Glass types ECR and C provide improved acid and chemical resistance. Type C glass fibers are generally only used to reinforce chemical-resistant liners. Continuous roving.

These consist of bundled, untwisted strands of glass fiber reinforcement and come as cylindrical packages for further processing. Woven roving. This is a heavy, drapable fabric, woven from continuous roving. It is available in various widths, thicknesses, and weights.

Woven roving provides high strength to large molded parts and is lower in cost than conventional woven fabrics. Reinforcing mats.

These are chopped strands held together with resinous bind- ers. There are two kinds of reinforcing mats used in pipe and fittings i. Chopped strand mats are used in medium-strength applications for pipe fittings and reinforcing where a uniform cross section is desired.

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Use of the combination mat saves time in hand lay-up operations. These lightweight fiberglass reinforcement mats allow layers with a high resin content with minimal reinforcement.

The surface veil provides extra envi- ronmental resistance for pipe and fittings, plus a smooth appearance. Some surface veils from polyester fibers are also used. The greatest strength is in the direction of the fibers. Some fibers are positioned at an angle to the rest of the fibers, as with helical filament winding and woven fabrics.

This provides different strength lev- els governed by the fiber quantity in each direction of fiber orientation. A combination of continuous and chopped fibers is also used to provide designed directional strength. Multidirectional isotropic. This arrangement provides nearly equal, although generally lower, strength and modulus in all directions. Manufacturers choose a resin system for chemical, mechanical, and thermal properties and processability. The two basic groups of resin systems are thermosetting and thermoplastic.

Fiber- glass pipe, by definition, uses only thermosetting resin systems. Thermosets are poly- meric resin systems cured by heat or chemical additives. Once cured, a thermoset is essentially infusible cannot be remelted and insoluble. The thermosetting resins used in fiberglass pipe fall into two general categories— polyesters and epoxies.

Polyesters have excellent water and chemical resistance and are noted for acid resistance. The base polyester resin is a solid. It is typically dissolved in styrene monomer, with which it cross-links to provide the final thermoset structure. Polyester resins are cured by organic peroxide catalysts. The type and amount of catalyst will influence gel time, cure time, curing temperature, and the degree of cure.

Manufacturers may select from several different types of polyester resins that pro- vide a wide range of performance characteristics. These include: Epoxy resins cannot be categorized by resin type as easily as polyesters. The type of curing agent, or hardener, is critical with epoxy resins because the agent influences the composite properties and performance.

The two basic types are amine- and anhydride- cured bisphenol-A epoxies. Bisphenol-A epoxy resins are commonly cured with multifunctional primary amines. The cured resin has good chemical resistance, particularly in alka- line environments, and can have good temperature resistance.

Bisphenol-A epoxy resins may also be cross-linked with various anhydrides by using a tertiary amine accelerator and heat. These cured polymers generally have good chemical resistance, especially to acids.

Inorganic materials, such as hydrated alumina, glass microspheres, clay, talc, calcium carbonate, sand, and calcium silicate, may yield economic, appearance, or performance advantages in fiberglass pipe. Promoters, accelerators, and inhibitors. Promoters and accelerators advance the action of the catalyst to reduce the processing time. Inhibitors provide control over the cure cycle and increase the shelf life of the resin mix.

The pigment choice affects the difference in reflected and transmitted color, clarity of the resin mix, reaction between dyes and other additives, such as cata- lysts, and the end-product color fastness and heat resistance. They are not subject to general corrosion attack, galvanic corrosion, aerobic corrosion, pitting, dezincification, and graphitic and intergranular corrosion.

Fiberglass pipes are subject to some environmental stress and aging effects, the determination of which is part of the fiberglass pipe design procedure see chapter 5. Fiberglass pipe resists a wide range of chemicals. The chemical resistance of fiber- glass pipe depends primarily on the particular resin matrix material used. Although other factors such as liner construction, cure, and fabrication method may influence the chemical resistance of fiberglass pipe, the primary factor is the resin.

The resins can be selected to provide chemical resistance to a broad range of materials. The fiberglass pipe manufacturer should be consulted for performance information for a particular chemical application.

In general, chemical agents are more aggressive at higher concentrations and elevated temperatures. Fiberglass pipe is virtually unaffected by colder temperatures. Therefore, normal shipping, handling, and storage procedures, as discussed in chapter 10, may be used in subzero weather. However, users and installers of fiberglass pipe should be aware that the coefficient of thermal expansion for fiber- glass pipe is generally higher than that for metal pipes see Table This must be rec- ognized and provisions made in design and installation to accommodate expansion and contraction, particularly in aboveground applications.

Special lining materials should match or exceed the hardness and abrasiveness of the contents being transported through the pipe or provide a high level of toughness and resilience. Therefore, under the proper combination of heat and oxygen, a thermosetting resin, like any organic matter, will burn. If required, the fire performance of fiberglass pipe can be enhanced by using resin systems that contain halogens or phosphorus.

Use of hydrated fillers also enhances flame resistance. Other additives, primarily antimony oxides, can also increase the effectiveness of halogenated resins.

Fire performance testing requires small samples and specialized test methods and may not indicate how a material will perform in a full-scale field or fire situation. The fiberglass pipe manufacturer should be consulted for specific information on the com- bustion performance of fiberglass pipe. This degradation, however, is almost entirely a surface phenomenon.

The structural integrity of fiberglass pipe is not affected by expo- sure to UV light. The use of pigments, dyes, fillers, or UV stabilizers in the resin system or painting of exposed surfaces can help reduce significantly any UV surface degrada- tion. Surfaces exposed to UV light are generally fabricated with a resin-rich layer. Other weathering effects, such as rain or saltwater, are resisted fully by the inherent corrosion resistance of fiberglass pipe.

There are no known cases in which fiberglass pipe products suffered degradation or deterioration due to biological action. No special engineering or installation pro- cedures are required to protect fiberglass pipe from biological attack. Some elastomers used in gaskets may be susceptible to this type of attack. Because fiberglass pipe is inher- ently corrosion resistant, there is no tuberculation of the fiberglass pipe caused by corro- sion by-products.

For this reason, fiberglass pipe product standards are based on performance and detail product performance requirements rather than thickness- property tables.

Table illustrates the broad range of mechanical properties avail- able for resin, glass fiber, and fiberglass pipe. This broad range of mechanical properties is further illustrated by the widely variable stress—strain curves possible with fiberglass pipe, depending on the amount, type, and orientation of the reinforcement as well as the manufacturing process.

Figures and show the typical shape of the stress—strain curves for high- and low-pressure pipes for the circumferential and axial directions, respectively.

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Many test methods develop data over a moderate time range and then statistically extrapolate the data to establish long-term design values. For example, the key long-term property test for fiberglass pipe is the development of a hydrostatic design basis HDB to establish the pipe pressure rating. This method requires pressurizing a minimum of 18 pipe samples at pressures far exceeding the normal use range and monitoring the time to failure. Data must be collected over a range of time from 1 hour to beyond 10, hours.

To estab- lish the pipe pressure rating, a safety factor is applied to this year value. This testing may be conducted using static pressurization the standard for water piping or cyclic pressure testing which is common for small-diameter pipes used in the oil field industry. The same pipe tested in both static and cyclic pressure condi- tions will exhibit significantly different regression behavior.

The cycling testing condition is far more severe 25 cycles per minute from 0 to test pressure. Because the test is so severe, the common practice is to use the year value directly for design purposes i.

To illustrate the comparison of the two procedures, Figure shows the results of a filament- wound epoxy pipe tested both by static and cyclic pressure testing procedures. Fillers, if used, are added during the winding process. Chopped glass rovings may be used as supplemental reinforcement. After curing, the pipe may undergo one or more auxiliary operations such as joint preparation. The inside diameter ID of the finished pipe is fixed by the mandrel out- side diameter OD.

The OD of the finished pipe is variable and determined by the pipe wall thickness. The filament winding process is illustrated in Figure Within the broad defini- tion of filament winding there are several methods used, including reciprocal, continu- ous, multiple mandrel, and ring and oscillating mandrel, each of which is described briefly. Figure shows the application of impregnated glass reinforcement onto a mandrel during production of a filament-wound pipe.

In this method the fiber placement head with the associated resin bath drives back and forth past a rotating mandrel see Figure The angle of fiber placement rela- tive to the mandrel axis is controlled by the synchronized translational speed of the bath and the rotational speed of the mandrel. Flowtite Technology, Sandefjord, Norway. Figure Continuous advancing mandrel method 3. The winding angles are controlled through a combination of longitudinal man- drel speed, mandrel rotation if used , or the rotation of planetary glass application stations.

Once started, these methods produce pipe continuously, stopping only to replenish or change material components. A second type of continuous process is the continuous advancing mandrel, which is composed of a continuous steel band supported by beams, which form a cylindrically shaped mandrel. The beams rotate, friction pulls the band around, and roller bearings allow the band to move longitudinally so that the entire mandrel continuously moves in a spiral path toward the end of the machine.

Raw materials continuous fibers, chopped fibers, resin, and aggregate fillers are fed to the mandrel from overhead. Release films and surfacing materials are applied from rolls adjacent to the mandrel. After curing, a synchronized saw unit cuts the pipe to proper length. This method is illustrated in Figure Finished pipe emerging from the curing oven is shown in Figure When the winding oper- ation finishes, the mandrels are indexed to a new position for curing while another set of mandrels is wound.

The OD of the finished pipe is determined by the ID of the mold tube. Figure Chopped glass reinforcement method Source: Figure Application of glass, resin, and sand of material introduced into the mold. Other materials, such as sand or fillers, may be introduced in the process during manufacture of the pipe. Two different methods of centrifugal casting are used and are described briefly.

Preformed glass reinforcement sleeve method. A preformed glass reinforce- ment sleeve is placed inside a steel mold.

Chopped glass reinforcement method. Varying proportions of chopped glass reinforcement, resin, and aggregate are introduced simultaneously, by layer, from a feeder arm that moves in and out of the mold.

This method is illus- trated in Figure Application of glass, resin, and sand within a rotating mold is shown in Figure Denver, Colo.: Because the interior pipe sur- face typically remains smooth over time in most fluid services, fluid resistance does not increase with age.

In addition, the smooth interior allows the pipe diameter to be reduced while maintaining the desired flow. This chapter provides a basis for analysis of the flow capacity, economics, and fluid transient characteristics of fiberglass pipe.

Many engineers have adopted rules that are inde- pendent of pipe length but rely on typical or limiting fluid velocities or allowable pres- sure loss per ft 30 m of pipe. Once the fluid velocity or the pressure loss is known, it is easy to size a pump to provide the proper flow rate at the required pres- sure.

The following equations are guidelines for the initial sizing of pipe. These equa- tions are presented with inch-pound units in the left-hand column and metric units in the right-hand column. Typical diameters for fiber- glass pressure pipe and suction pipe can be calculated using the following equations. Figure Friction pressure loss due to water flow through fiberglass pipe 4.

Different computational methods can be used to determine the head loss in fiberglass pipe. The suitability of each method depends on the type of flow gravity or pumped and the level of accuracy required. Although not as technically correct as other methods for all velocities, the Hazen-Williams equation has gained wide acceptance in the water and wastewater industries. The Hazen-Williams equation is presented in nomograph form in Figure , which is typical for small-diameter fiberglass pipe.

When fluids other than water are encountered, a more universal solution such as the Darcy-Weisbach equation should be used. The Hazen-Williams equation is valid for turbulent flow and will usually provide a conser- vative solution for determining the head loss in fiberglass pipe.

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Graphs and examples use nominal pipe size for simplicity. The actual inside diameter ID should be used in hydraulic calculations. A design value of is frequently used with fiberglass pipe. It is inversely proportional to the diameter of the pipe. The primary advantage of this equation is that it is valid for all fluids in both laminar and turbulent flow. The disadvantage is that the Darcy-Weisbach friction fac- tor is a variable.

Once preliminary sizing of the pipe diameter has been completed, the next step is to determine whether the flow pattern within the pipe is laminar or tur- bulent. This characterization of the flow is necessary in the selection of the appropriate friction factor to be used with the Darcy-Weisbach equation. The well-known Reynolds number equation is used to characterize the fluid flow: Friction factor for laminar flow is denoted as fl, and ft denotes friction factor for turbulent flow.

When the flow regime is turbulent i. Fiberglass pipe has a surface roughness parameter e equal to 1. The fric- tion factor for turbulent flow can also be calculated from the Colebrook equation: This approach has sufficient accuracy for many applications and is used most often with the Hazen-Williams or Manning equations. The approach does not consider turbulence and subsequent losses created by different fluid velocities.

When tabular data are not available or when additional accuracy is necessary, head loss in fittings or valves can be determined using loss coefficients K factors for each type of fitting.

Table provides the typical K factors. Equation illustrates the loss coefficient approach. The total head loss in a system includes, but is not limited to, losses from fittings, the head loss from the straight run pipe, and head losses due to changes in elevation.

This section outlines the basic procedure for determining the head loss due to friction and relative economic merits when considering different pipe materials.

Calculate the head loss Eq Convert head loss to pump horsepower demand: Calculate the annual energy usage To demonstrate the calculations in a clear format, the expressions below assume the pumps run 24 hours per day at full capacity.

This is not a realistic assumption. In design situations, engineers must assess the actual expected operating conditions, e. Calculate average annual energy cost AEC: These techniques consider the installed cost of pipe in the calculation and future cash flows are discounted to present value. The pressure surge results from the rapidly moving wave that increases and decreases the pressure in the system depending on the source and direction of wave travel. Under certain conditions, pressure surges can reach magnitudes sufficient to rupture or collapse a piping system, regardless of the material of construction.

Rapid valve closure can result in the buildup of pressure waves due to the conver- sion of kinetic energy of the moving fluid to potential energy that must be accommo- dated. These pressure waves will travel throughout the piping system and can cause damage far away from the wave source.

The relatively high com- pliance low modulus of elasticity of fiberglass pipe contributes to a self-damping effect as the pressure wave travels through the piping system. In addition to rapid valve closure or opening, sudden air release and pump start-up or shut-down can create pressure surge. Pressure surges do not show up readily on conventional Bourdon tube gauges because of the slow response of the instrument.

The net result of pressure surge can be excessive pressures, pipe vibration, or move- ment that can cause failure in pipe and fittings. In other cases, mechanical valve operators, accumulators, rupture discs, surge relief valves, feedback loops around pumps, etc.

Good design practice usually prevents pressure surge in most systems. Installation of valves that cannot open or close rapidly is one simple precaution. In addition, pumps should never be started in empty discharge lines unless slow-opening, mechan- ically actuated valves can increase the flow rate gradually. Many fluid mechanics and hydraulic handbooks provide procedures such as the previous Talbot equation for calculating pressure surges as a result of a single valve closure in simple piping systems.

Sophisticated fluid transient computer programs are also available to analyze pressure surge in complex multibranch piping systems under a variety of conditions. Use of the Hazen-Williams equation. Compute the frictional pressure loss in a Compute the frictional pressure loss in a 1,ft long, in. Compute the head loss per unit length of pipe using Eq Convert head loss to pressure drop using Eq Determine the pipe diameter, working pressure, and pres- sure class on a pipeline.

Assume the kinematic change of 7. The flow rate is 8, gpm. Determine minimum diameter Eq Step 2. Calculate average fluid velocity Eq Calculate the Reynolds number Eq Step 4.

Calculate the friction factor Eq Calculate system friction loss using Eq and Eq Consequently, the total K factor is 4 0. Combine friction and elevation head: Convert head loss to working pressure Eq However, a higher pressure class tentatively be selected to account for may tentatively be selected to account possible water hammer in the line.

For for possible water hammer in the line. See example to kPa class is selected. See example verify that this is adequate for pres- to verify that this is adequate for pres- sure surge. Example Comparative power cost calculation.

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Assume a 10,ft long, 6-in. The engi- water on a year-round basis. Calculate the average AEC pipeline. Step 1. Calculate the head loss for each material Eq Convert head loss to horsepower demand Eq In design sit- uations, engineers must assess actual operating levels. Calculate the AEC Eq and calculate the total energy cost over 20 years: Surge pressure calculation.

Assume a full instantaneous change in Assume a full instantaneous change in velocity equal to the flow velocity in the velocity equal to the flow velocity in the pipe.

The fiberglass pipe has a tensile pipe. The pipe wall thickness class of kPa. The bulk modulus of is , psi. Calculate the wave velocity Eq Calculate the surge pressure Eq Check compliance with the maximum system pressure requirement: The This exceeds the pressure class. The engineer has three options. The first engineer has three options. The first would be to increase the pressure class would be to increase the pressure class to accommodate the surge, maintain- to accommodate the surge, maintain- ing the same pipe diameter.

The sec- ing the same pipe diameter. The larger pipe pressure requirement. The larger pipe diameter will lower operating pressure diameter will lower operating pressure due to lower friction loss and will lower due to lower friction loss and will lower fluid velocity. The third option is to fluid velocity. The third option is to provide measures, such as a surge provide measures, such as a surge tank, to reduce the magnitude of the tank, to reduce the magnitude of the surge.

For this example, the second option For this example, the second option will be used and a diameter of 20 in. Calculate the fluid velocity for the new pipe diameter Eq Step 5. Calculate the new working pressure. Reynolds number Eq Friction factor Eq Friction losses using Eq and Eq The total K factor is then 4 0. Convert to working pressure Eq and using Htotal for Hf: Calculate the pressure surge using Eq Before final selection, the engineer would typically evaluate the economics of using the larger diameter with a higher pressure class ver- sus using the original diameter with a still higher pressure class.

New York: Fiberglass Pipe Pressure Pipe. American Institute. Water Works Association. Kent, G. Preliminary Pipeline Sizing. Benedict, R. Fundamentals of Pipe Chemical Engineering. Sharp, W. Predict- Brater, E. Handbook of ing Internal Roughness in Water Mains. AWWA, 80 If the results of any calculation indicate that a requirement is not satisfied, it will be necessary to upgrade installation param- eters or select a pipe with different properties, or both, and redo pertinent calcula- tions.

Special information and calculations not covered in this chapter may be required in unusual cases see Sec.

Both rigorous and empirical methods are used to design fiberglass pipe. In addition to short-term tests, many performance limits are determined at 50 years through sta- tistical extrapolation of data obtained from long-term tests under simulated service conditions. Design stress or strain values are obtained by reducing performance limits using appropriate design factors.

Design factors are established to ensure adequate performance over the intended service life of the pipe by providing for variations in material properties and loads not anticipated by design calculations. Design factors are based on judgment, past experience, and sound engineering principles. The design method discussed in this chapter applies in concept to pipe with uniform walls and to pipe with ribbed-wall cross sections.

However, for design of pipe with ribbed walls, some of the equations must be modified to allow for the special properties of this pipe.

Also, additional calculations not addressed in this chapter may be required to ensure an adequate design for a ribbed-wall cross section. The equations are presented with inch-pound units in the left-hand column and metric units in the right-hand column.

Working pressure, Pw. The maximum anticipated, long-term operating pressure of the fluid system resulting from typical system operation. The maximum sustained pressure for which the pipe is designed in the absence of other loading conditions. Surge pressure, Ps. The pressure increase above the working pressure, some- times called water hammer, that is anticipated in a system as a result of a change in the velocity of the fluid, such as when valves are operated or when pumps are started or stopped.

Surge allowance, Psa. That portion of the surge pressure that can be accommo- dated without changing pressure class. The surge allowance is expected to accommodate pressure surges usually encountered in typical systems. Hydrostatic design basis, HDB. Design factor, FS. A specific number greater than 1 used to reduce a specific mech- anical or physical property in order to establish a design value for use in calculations. This is reflected in typical long-term flow coefficient values of 0. The engineer may wish to consider this in establishing design conditions.

See chapter 4 on hydraulics. Excessive surge pressures should be identified in the design phase, and the causative condition should be eliminated or automatic surge-pressure relief provided, otherwise, a higher pressure class should be selected.

Some pipe products may have sig- nificantly higher values for these properties. Pipe properties necessary for design calculations include the following: A given combination of soil type and degree of compaction will largely determine the following values required for design calculations: The calculations may be made using either stress or strain, depending on the basis used to establish a particular product performance limit.

The procedure for using design calculations to determine whether pipe meets the requirements discussed in Sec. Check working pressure, Pw Sec. Check surge pressure, Ps Sec. Calculate allowable deflection from ring bending Sec.

Determine soil loads, Wc, and live loads, WL Sec. Calculate the composite constrained soil modulus, Ms Sec. Check combined loading Sec. Check buckling Sec. See Sec. The HDB of fiberglass pipe varies for different products, depending on the materials and composition used in the reinforced wall and in the liner.

The HDB may be defined in terms of reinforced wall hoop stress or hoop strain on the inside surface. Temperature and service life.

The required practice is to define projected pro- duct performance limits at 50 years. Performance limits at elevated temperature depend on the materials and type of pipe wall construction used. The manufacturer should be consulted for HDB values appropriate for elevated temperature service. Design factors. This factor ensures that the stress or strain due to the short-term peak pressure conditions do not exceed the short-term hydro- static strength of the pipe. This factor ensures that stress or strain due to sustained working pressure does not exceed the long-term hoop strength of the pipe as defined by HDB.

For fiber- glass pipe design, this minimum design factor is 1. Both design factors should be checked. Either design factor may govern pipe design, depending on long-term strength regression characteristics of the particular pipe product.

Prudent design practice may dictate an increase or decrease in either design factor, depending on the certainty of the known service conditions. The pressure class of the pipe should be equal to or greater than the working pressure in the system, as follows: The pressure class of the pipe should be equal to or greater than the maximum pressure in the system, due to working pressure plus surge pressure, divided by 1.

Factory hydrotesting at pressures up to 2 Pc is acceptable and is not governed by Eq and Eq Calculated surge pressure, Ps. The surge pressure calculations should be performed using recognized and accepted theories.

Because of this, the engineer should generally expect lower calculated surge pressures for fiberglass pipe than for pipe materials with a higher modulus or thicker wall or both. Surge allowance. The surge allowance is intended to provide for rapid transient pressure increases typically encountered in transmission systems. Special consideration should be given to the design of systems subject to rapid and frequent cyclic service.

The manufacturer should be consulted for specific recommendations. Satisfaction of this requirement is assured by using one of the following formulas. For stress basis: The shape factor relates pipe deflection to bending stress or strain and is a function of pipe stiffness, pipe zone embedment material and compaction, haunching, native soil conditions, and level of deflection.

For pipe zone embedment materials with a finer grain size, use the Df value of sand with moderate to high compaction. The long-term, ring-bending strain varies for different products, depending on materials and type of construction used in the pipe wall. Prudent design of pipe to withstand bending requires consideration of two separate design factors. The first design consideration is comparison of initial deflection at failure to the maximum allowed installed deflection.

This test requirement demonstrates a design factor of at least 2. The second design factor is the ratio of long-term bending stress or strain to the bending stress or strain at the maximum allowable long-term deflection. This require- ment may be stated as follows: When installed in the ground, all flexible pipe will undergo deflection, defined here to mean a decrease in vertical diameter. The amount of deflection is a function of the soil load, live load, native soil characteristics at pipe ele- vation, pipe embedment material and density, trench width, haunching, and pipe stiffness.

Many theories have been proposed to predict deflection levels; however, in actual field conditions, pipe deflections may vary from calculated values because the actual installation achieved may vary from the installation planned. These variations include the inherent variability of native ground conditions and variations in meth- ods, materials, and equipment used to install a buried pipe.

As presented previ- ously and as augmented by information provided in the following sections, Eq serves as a guideline for estimating the expected level of short-term and long-term deflection that can be anticipated in the field. This equation is the best known and docu- mented of a multitude of deflection-prediction equations that have been proposed.

As presented in this chapter, the Iowa formula treats the major aspects of pipe—soil inter- action with sufficient accuracy to produce reasonable estimates of load-induced field deflection levels. Soil Engineering. These deflections are typically small for pipe stiffnesses above 9 psi to 18 psi 62 kPa to kPa depending on installation conditions.

For pipe stiffnesses below these values, consid- eration of these items may be required to achieve an accurate deflection prediction. Application of this method is based on the assumption that the design values used for bedding, backfill, and compaction levels will be achieved with good practice and with appropriate equipment in the field. Experience has shown that deflection levels of any flexible conduit can be higher or lower than predicted by calculation if the design assumptions are not achieved.

The deflection lag factor converts the immedi- ate deflection of the pipe to the deflection of the pipe after many years. The vast majority of this phenomenon occurs during the first few weeks or months of burial and may continue for some years, depending on the frequency of wetting and drying cycles, surface loads, and the amount of original compaction of the final backfill. Secondary causes of increasing pipe deflection over time are the time-related consolidation of the pipe zone embedment and the creep of the native soil at the sides of the pipe.

These causes are generally of much less signifi- cance than increasing load and may not contribute to the deflection for pipes buried in relatively stiff native soils with dense granular pipe zone surrounds. For long-term deflection prediction, a DL value greater than 1.

The bedding coefficient reflects the degree of support provided by the soil at the bottom of the pipe and over which the bottom reac- tion is distributed. Assuming an inconsistent haunch achievement typical direct bury condition , a Kx value of 0. For uniform-shaped bottom support, a Kx value of 0. The long-term vertical soil load on the pipe may be considered as the weight of the rectangular prism of soil directly above the pipe. The soil prism would have a height equal to the depth of earth cover and a width equal to the pipe outside diameter.

The following calculations may be used to compute the live load on the pipe for surface traffic see Figure These calculations consider a sin- gle-axle truck traveling perpendicular to the pipe on an unpaved surface or a road with flexible pavement. Direction of Travel 0. Change accounts for overlapping influence areas from adjacent wheel loads.

Equations as shown are for h in inches meters. This lane load is ignored in these calculations because it has only a small effect on the total live load and may be added by the engi- neer if deemed appropriate.

The above calculation method assumes that the live load extends over the full diameter of the pipe. This may be conservative for large-diameter pipe under low fills.

The OD is the outside diameter of the pipe in inches millimeters. For depths of fill less than 2 ft 0. Such an analysis is beyond the scope of this manual. The previous calculation is for single-axle trucks. Design for tandem-axle trucks may use the same procedures; however, the following substitutions for L1 should be used if both axles load the pipe at the same time. Rigid pavements dramatically reduce live load effects on concrete pipe.

The Portland Cement Association developed a calculation method to consider loads transmitted through concrete pavements Vertical Pressure on Concrete Culverts Under Wheel Loads on Concrete Pavement Slabs, Portland Cement Association, Publication ST, that is still in use today and is suitable for computing live loads on fiberglass pipe under rigid pavements.

The loads shown assume that the load extends over the full diameter of the pipe. This assump- tion will not be true for large-diameter pipes with shallow covers.

Loads for this condition may be lower. See calculation note 3 for guidance on appropriate adjustments. The pipe stiffness can be determined by conducting parallel-plate loading tests in accordance with ASTM D During the parallel-plate loading test, deflection due to loads on the top and bottom of the pipe is measured, and pipe stiffness is calculated from the following equation: The vertical loads on a flexible pipe cause a decrease in the vertical diameter and an increase in the horizontal diameter.

The horizontal movement develops a passive soil resistance that helps support the pipe. The passive soil resistance varies depending on the soil type and the degree of compaction of the pipe zone backfill material, native soil characteristics at pipe eleva- tion, cover depth, and trench width see Table This change is based on the work of McGrath Design values of the constrained modulus are presented in Table The table shows that Ms increases with depth of fill, which reflects the increased confining pressure.

This is a well-known soil behavior. To determine Ms for a buried pipe, separate Ms values for the native soil Msn and the pipe backfill surround Msb must be determined and then combined using Eq Special cases are discussed later in this chapter.

For stress basis HDB: ASTM D The borderline condition is indicated by an en dash between the two symbols, for example, CL—CH. SC1 soils have the highest stiffness and require the least amount of compactive energy to achieve a given density. SC5 soils, which are not recommended for use as backfill, have the lowest stiffness and require substantial effort to achieve a given density.

Soil stiffness categories are explained in chapter 6.

SC1 soils have higher stiffness than SC2 soils, but data on specific soil stiffness values is not available at the current time.

Even if dumped, SC1 materials should always be worked into the haunch zone, see Sec. Vertical stress level is the vertical effective soil stress at the springline elevation of the pipe. It is normally computed as the design soil unit weight times the depth of fill. Buoyant unit weight should be used below the groundwater level.

Engineers may interpolate intermediate values of Msb for vertical stress levels not shown on the table. In-between values of Sc may be determined by straight-line interpolation from adjacent values. Ms special cases: Geotextiles—When a geotextile pipe zone wrap is used, Msn values for poor soils can be greater than those shown in this table. Solid sheeting—When permanent solid sheeting designed to last the life of the pipeline is used in the pipe zone, Ms shall be based solely on Msb. Buried pipe is subjected to radial external loads com- posed of vertical loads and the hydrostatic pressure of groundwater and internal vac- uum, if the latter two are present.

External radial pressure sufficient to buckle buried pipe is many times higher than the pressure causing buckling of the same pipe in a fluid environment, due to the restraining influence of the soil. The summation of appropriate external loads should be equal to or less than the allowable buckling pressure. The allowable buck- ling pressure qa is determined by the following equation: Satisfaction of the buckling requirement is assured for typical pipe installations by using the following equation: The minimum requirements for axial strengths are as specified by Sec.

When restrained joints are used, the pipe should be designed to accommodate the full mag- nitude of forces generated by internal pressure. Special consideration should be made for the following conditions: For reference, the set of design conditions, pipe properties, and installation parameters assumed for this design example are presented in Table This summary is not repeated in the body of the example design calculations.

The pipe material properties and characteristics presented in Table have been assumed for illustrative purposes and should not be used as actual design values.

Values for these parameters differ for various pipe constructions and materials and should be obtained from the manufacturer. Confirm pressure class Eq Check working pressure Eq Check surge pressure Eq Calculate maximum allowable deflection Eq Calculate soils load Eq Calculate live loads Eq Calculate the composite constrained soil modulus Eq Determine Sc from Table Calculate the predicted deflection Eq Check combined loading Eq and Check buckling Eq a.

Buckling check at 1. Buckling check at 2. American Association of Density. West Conshohocken, Pa.: American State Highway and Transportation Officials. Society for Testing and Materials. American Society for Testing and Materials. American Soil Using Standard Effort. West Consho- Water Works Association.

Related titles

American Society for Testing Cagle, L. Recom- and Materials. Group on Buckling. In Proc. Modulus of Soil Reaction Plate Loading. Values for Buried Flexible Pipe. Journal of American Society for Testing and Materials.

Geotechnical Engineering, Pipeline Installation. Relativity Publishing. Soil Classification System. West Consho- Luscher, U. Buckling of Soil Surrounded hocken, Pa.: American Society for Testing Tubes.

Soil Mech. In Pipelines in the Constructed Pipe and Fittings. Edited by J. Castronovo American Society for Testing and Materials. Reston, Va.: American Soci- ———. American Society of Loads, Deflection, Strain. ISO Bull. Spangler, M. Soil Engineering, 4th ed.

The structural design process, discussed in chapter 5, assumes that a pipe will receive support from the surrounding soil, and the installation process must ensure that the support is provided. The guidelines in this chapter suggest pro- cedures for burial of fiberglass pipe in typically encountered soil conditions.

Recom- mendations for trenching, placing, and joining pipe; placing and compacting backfill; and monitoring deflection levels are included. Diameters range from 1 in. Engineers and installers should recognize that all possible com- binations of pipe, soil types, and natural ground conditions that may occur are not considered in this chapter.

The recommendations provided may need to be modified or expanded to meet the needs of some installation conditions. Section 6. Guidance for installation of fiberglass pipe in subaqueous conditions is not included.

The following terms are specific to this manual: Backfill material placed in the bottom of the trench or on the founda- tion to provide a uniform material on which to lay the pipe; the bedding may or may not include part of the haunch zone see Figure A measure of the ease with which a soil may be compacted to a high density and high stiffness. Crushed rock has high compactibility because a dense and stiff state may be achieved with little compactive energy.

Any change in the diameter of the pipe resulting from installation and imposed loads. Deflection may be measured and reported as change in either ver- tical or horizontal diameter and is usually expressed as a percentage of the unde- flected pipe diameter. The engineer or the duly recognized or authorized representative in responsible charge of the work. Final backfill. Backfill material placed from the top of the initial backfill to the ground surface see Figure Soil particles that pass a No.

Any permeable textile material used with foundation, soil, earth, rock, or any other geotechnical engineering-related material as an integral part of a synthetic product, structure, or system.

Backfill material placed on top of the bedding and under the spring- line of the pipe; the term only pertains to soil directly beneath the pipe see Figure Initial backfill.

Backfill material placed at the sides of the pipe and up to 6 in. Backfill 6 to 12 in. Aggregates such as slag that are products or by- products of a manufacturing process, or natural aggregates that are reduced to their final form by a manufacturing process such as crushing.

Maximum standard Proctor density. The maximum dry density of soil com- pacted at optimum moisture content and with standard effort in accordance with ASTM D Native in situ soil. Natural soil in which a trench is excavated for pipe instal- lation or on which a pipe and embankment are placed. Open-graded aggregate. An aggregate that has a particle size distribution such that when compacted, the resulting voids between the aggregate particles are rela- tively large.

Optimum moisture content. Pipe zone embedment. All backfill around the pipe, including the bedding, haunching, and initial backfill.

Processed aggregates. Aggregates that are screened, washed, mixed, or blended to produce a specific particle size distribution. Manufacturer The person or company that furnishes the tank components. Owner The person or firm that will own and operate the completed tank. The owner may designate agents, such as an engineer, downloadr, or inspector, for specific project responsibilities. downloadr The person, company, or organization that downloads the tank.

Reservoir A ground-supported, flat-bottom cylindrical tank with a shell height less than or equal to its diameter. Standpipe A ground-supported, flat-bottom cylindrical tank with a shell height greater than its diameter. Tank An elevated tank, standpipe, or reservoir used for water storage. Top capacity level TCL The maximum operating level of water in a tank, as dictated by the elevation at which water discharges from the tank through the over- flow pipe entrance.

In a standpipe or reservoir, the top capacity level is as given by the downloadr. Once a draft standard or revision is approved by a standards committee, it is forwarded to the AWWA Standards Council for review and approval. If approved by the council, it is offered for public review and then presented to the AWWA Board of Directors for final approval.

Welded construc- tion had totally replaced riveted construction by the s. This year transition period from riveted to welded design and construction was necessary because time was needed to train enough skilled welders and because contractors wanted to keep their skilled riveting crews working as long as possible. Advantages The advent of welded tanks provided opportunities for new tank configurations, but the greatest advantage of welded over riveted tanks was the development of smooth structures with much lower maintenance costs than was possible with lapped, riveted seams.

Manual, semiautomatic, and automatic welding processes have improved con- tinually over the years, offering increased economy and strength. As of the writing of this manual, the largest welded steel water-storage tank con- structed had a capacity of 34 mil gal ML.

Elevated tanks have been constructed with capacities up to 4 mil gal 15 ML , and designs are available for greater capacities. Construction Bolted steel tanks are made of uniformly sized panels usually 5 ft wide by 8 ft high or 9 ft wide by 5 ft high [1. Organic gaskets or sealants are used to achieve a watertight seal at the bolted joints.Calculate the wave velocity Eq Design values of the constrained modulus are presented in Table Consult the manufacturer for recommendations and limitations.

Within the broad defini- tion of filament winding there are several methods used, including reciprocal, continu- ous, multiple mandrel, and ring and oscillating mandrel, each of which is described briefly. This security feature prevents the reproduction and redistribution of downloaded documents.