The design basis behind DI pipe is the most conservative of products on the market today. Decades of reliable service is evidence of DI pipe’s success. Design calculations are found in the ANSI/AWWA C151/A21.51 Standard Design for Ductile Iron Pipe.
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The most notable difference is the safety factor. The safety factor for DI pipe is 2.0 versus the safety factor for steel, ranging from 1.33 to 2.0, depending on the percent of yield strength used.
Notice the two different equations used to calculate thickness design. Allowing the stress to escalate to 75 percent of yield strength lowers the steel pipe's safety factor to 1.33 when including surge, compared to the 2.0 safety factor used in the DI pipe design. The difference in percentages to yield affect the thickness design of the pipe.
Let’s stick with the more conservative and trustworthy calculations. Take the example of a 24-inch water line with a working pressure of 150 psi. Calculating the thickness:
Required Thickness
Steel Pipe (50% Yield) = .086 Thickness
Steel Pipe (75% Yield) = .095 Thickness
Ductile Iron Pipe = .157 Thickness
The thickness of the DI pipe is much greater than steel. The minimum thickness for a 24-inch Class 200 pipe is .24 inch. This is well beyond the calculated thickness design for internal pressure.
There is a comfortable feeling knowing the product chosen is designed well above the intended use. We do not know what the future will bring 100 years down the road, but we know that the design of DI pipe helps to ensure your water delivery system's longevity.
Everyone would like to see a return on investment. These annual savings could be put to practical use. For more information on the these calculations, check out McWane's Pocket Engineer.
Additionally, DI pipe is also SMaRT certified with as much as 95 percent recycled content used in the manufacturing process. It also has no "end of use," which means that when replaced, it can be recycled over and over again. Choosing a sustainable product like Ductile iron not only benefits the end-user, but also our environment long term.
Ductile iron pipe is unique when it comes to corrosion control. An oxide layer is formed on the inside as well as the outside of all DI pipe during the manufacturing process. This oxide layer provides adequate corrosion protection (in many circumstances.) Utilization of the 10 Point Soil System will determine if there is a need for additional corrosion protection. The next step in corrosion protection for DI pipe is polyethylene encasement, better known as V-Bio®.
V-Bio is formed by bonding three layers of co-extruded, linear, low-density polyethylene into one. The inside surface contains an antimicrobial biocide to control microbiologically influenced corrosion and a volatile corrosion inhibitor to prevent galvanic corrosion.
V-Bio is easily installed in the field prior to pipe installation, making it cost-effective and easy to use. DI pipe and V-Bio can be installed in nearly any weather condition. No other product on the market compares.
Polyethylene encasement has proven to control corrosion in aggressive soils for more than 50 years and is cost-effective. The investment in V-Bio is minimal compared to the project's overall cost, especially when compared to the vastly more expensive alternative of bonded coatings used by the steel pipe industry. Not to mention the even higher costs associated with cathodic protection that is widely used in conjunction with steel.
Bonded coatings used to protect steel pipe are very expensive. Other issues that plague bonded coatings are handling and patching. The thin wall of steel pipe may not have enough beam strength to support its own weight, making for difficult handling.
It is difficult to handle a steel pipe section through installation without some damage to the bonded coatings. Any void in the bonded coating dramatically increases corrosion's potential, and these voids must be repaired. Contractors do not have the luxury of waiting until the sun shines to get the job done.
Time is money, and these folks need a product that is easy to work with, such as DI pipe. Some steel pipes are also coated with cement mortar, which is porous and subject to cracking. Again, any void in the coating increases the potential for corrosion of steel pipe.
Contact us to discuss your requirements of Di Pipe Manufacturer. Our experienced sales team can help you identify the options that best suit your needs.
Ductile iron pipe can be installed in the rain, sleet, snow, high heat, or freezing temperatures. Because steel pipe needs to be welded together, a rainstorm can shut down any progress being made.
Ductile iron pipe joints come in 18-to 20-foot lengths, which are much easier to handle in the field than 40- to 50-foot steel joints. Do the math. Four joints of 24-inch ductile per hour = 72 feet, versus one joint of steel at 40 feet.
18-foot DI joints also provide a better opportunity for deflection. This deflection capability reduces the number of fittings. Again, reducing the overall cost of a project.
Jerry Regula, "JR" is a product engineer with McWane Ductile. Jerry’s responsibility is to provide technical support for water professionals at all levels including engineers, private water companies, contractors, municipalities, and water districts. JR has been with McWane Ductile for more than 30 years, starting on the ground floor. Jerry has been involved in nearly all facets of the foundry, providing him with extensive experience in manufacturing, installation, and design of ductile iron water products. JR is a NACE Certified Corrosion Technician, Envision Specialist, and member of the American Society of Civil Engineers. He enjoys spending time with his church where he is a speaker and treasurer, as well as spending time with his wife Susan and their two daughters, Katelyn and Shannon on their farm in Ohio. “Many people do not realize how their water gets to them or how blessed we are to have clean drinking water,” says Regula. “I am honored as a water professional to do my part in ‘Building Iron Strong Utilities for Generations.’" Jerry’s favorite quote: "I can do all things through Christ who strengthens me.” ://www.linkedin.com/in/jerry-regula-6a87b/
Good Question! Today's Iron Strong Blog answers it. At first glance, you might think longer lengths mean fewer joints, and that has got to be better. So why don't all manufacturers make longer pipe? This perceived advantage is really a myth and we will look at that in a minute. In fact, there are more Ductile iron pipe plants in North America that manufacture 18-foot length pipe either entirely or as a significant portion of their product mix.
And don't get me started on the poly/welded steel pipe because, yes, those are joints, and yes, they can leak and separate if not appropriately assembled – it does happen. Besides, those joints often take longer to make up than it takes to dig the trench to lay the pipe! But let’s first talk about why you would need or want longer or shorter lengths of pipe.
What is true is that pipelines are more often composed of many curves, particularly in residential areas. In , residential community construction and development changed forever with the beginning of Levittown, NY. Levittown is most often credited with being the first residential planned community in North America. Its curved residential street design is carried on today throughout Canada and the United States.
Often, these curves can be accommodated by using 18-foot lengths, eliminating the need for costly fittings and associated installation costs. Not only must you pay for the extra fittings but also the additional joint restraints, labor, and lost time.
You can calculate the radius McWane Ductile 18-foot lengths can make by using the McWane Pocket Engineer: https://pe.mcwane.com/groups/ductile-iron-pipe/mcwane-ductile/calculators/radius
Shorter lengths are usually mostly preferred in urban situations. In fact, requests for shorter than 18-foot pipe are not unusual. Even though the old streets may be laid out straight in a grid-like fashion, urban environments are often congested underground with many other buried utilities making installing long pipe lengths difficult.
As can be seen, long lengths would be detrimental to deal with in these crowded urban situations, but even outside urban centers, the underground environment is getting more crowded.
Rural areas are not immune to the problem of existing utilities, either. There are often drainage issues in or along roads that pipelines must curve around or under. These rural scenarios are another area where 18-foot lengths can save utilities and installers time and money. In these cases, the reduction of eight joints, eight joint restraints, and the time and money to install all of that besides cutting pipe to fit can often be obtained using 18-foot pipe.
Another factor affecting pipe installation and the benefit of 18-foot length pipe is construction zone width limitations. Occasionally, pipeline installations are required along roads and streets that necessitate the maintenance of traffic flow. While the difference of 2 feet may not seem much, it could be significant in a situation with limited swing space. Standard road lane widths are 8 to 10 feet and shoulders, when present, narrower. Combined with equipment width and lane isolation requirements, traffic safety could dictate using shorter lengths versus undesirable and more expensive temporary traffic closures requiring flaggers, police details, and barriers.
Speaking of Safety, most pipe installations now require the use of trench shoring of some type. Often this shoring is accomplished via the use of trench boxes. An 18-foot length pipe doesn't require as long a box as 20-foot pipe. A smaller box is easier to move due to lighter weight, thereby speeding up installation while being less expensive to rent or buy, resulting in saving money while maintaining a safe installation environment. These safety and trench box issues are compounded on deep pipe installations.
Eighteen-foot length pipe is also better suited than longer lengths in wet trench installations. Often wet trench or high groundwater installations can be completed by running pumps instead of well-point systems. Still, longer trenches required for longer pipes may necessitate not only larger, more expensive, capacity pumps, but more of them. Moving the pumps and the extra cost of refueling and downtime during refueling may add additional costs not often considered.
Modern technology has also made 18-foot and even shorter length pipe more desirable. This is especially true in the arena of trenchless technologies, especially Horizontal Directional Drilling (HDD) installation. HDD installs have a curve-based profile by necessity. As previously discussed, 18-foot lengths, especially with high deflections available in some joints (up to 15), can accommodate a much tighter radius. This deflection capability could even make the difference between a doable project to a prohibitive project.
Check out McWane Ductile’s Pocket Engineer to use for calculating pipe curve geometry in HDD installations.
As these costs accumulate, the small margins installers work on can be eroded, making the project a losing proposition for an installer. No one wants that to happen as corner-cutting and disputes over extras arise due to poor product selection. Choosing the right product can make long term contributions to the installers as well as designers, and utilities. In some instances, a project might benefit from using even shorter than 18-foot lengths, so contact your local McWane Ductile Representative more information early in the design stages.
We have team members who have managed small and large water utility systems, served in engineering consulting firms, and bring decades of experience in solving field issues involving pipeline construction and operation. From design, to submittal, to installation, we strive to provide education and assistance to water professionals throughout the water and wastewater industry.
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