Material comparisons, in whatever format presented, are a common and useful tool for evaluating the advantages and disadvantages of one product versus another. These evaluations can assist engineers and specifiers with selecting the proper material, yet must contain relevant and factual details so as not to be vague or misleading. Otherwise, they are no more than bad marketing literature. Such is the case with a recent publication from a plastic pipe manufacturer and their most recent comparison of PVC pipe to Ductile iron pipe (DI pipe)1. In this #IronStrong Blog, we pointedly call out several erroneous claims by “writing the wrongs” contained in the published chart below.
There are no shortcuts to making good Ductile iron pipe (DI pipe). Built upon fundamentals and protocols developed by the American Society for Testing and Materials (ASTM) and the American National Standards Institute came the American Water Works Association standards (AWWA), which govern and judge the consensus fitness of products as produced. These standards strictly govern the dimensions and properties of DI pipe. What separates DI pipe manufacturers is their adherence to these standards and consistent dedication to quality assurance.
Through the years, across the country, contractors, engineers, authorities, and customers routinely ask questions that seem basic yet truly speak to the fundamental versatility of Ductile iron pipe (DI pipe). Among the most popular questions are:
Dear Ditch Doctor: Out here in the western United States, we wind up with a lot of pipelines installed up or down serious hills, dare I say mountains as well? We are good at the construction part, yet time after time we struggle with getting a satisfactory post-installation hydrostatic test on the pipeline, especially with inclined installations. Often the pipeline drops anywhere from 20 to 50 psi on the gauge and can do that several times or more until we take some sort of drastic redo/restart on the test procedures.
Whenever the word "rating" is used regarding Ductile iron pipe (DI pipe), a 100-psi surge allowance and a safety factor of 2.0 are consistently included for all wall classes. This leads to conservative yet versatile designs for the long-term performance of utility pipelines of all kinds in various or changing conditions. Hence the basic universal rating for DI pipe is 350-psi which equates to a minimum of 900-psi of hydrostatic pressure containment within the pipeline.
So, the site plans say, "… connect to existing iron pipe." Now that we’ve dug down to it, I can’t tell if it is gray iron or Ductile iron pipe. Are there ways to reliably distinguish between the two without some physical testing on a sample? In this blog, we'll take a closer look at the characteristics and differences between the two types of pipe.
This article takes a deeper dive into concepts outlined in the July 2020 entry prepared by my co-worker Gary Gula, How Much Does Ductile Iron Pipe Weigh and Why Does It Matter to You? Specifically, we will focus on the pipe weight itself, answering questions such as: From where do these weights originate? Why do we show weights on each pipe? How trustworthy are these weights as provided? And, What do these weights mean to me, the pipe customer?
Dear Ditch Doctor
We recently installed a 15,000-ft 12-inch diameter Ductile iron pipeline with several 6-inch branches off two hydrants. The average depth of cover is 4 feet. The city engineer has expressed a concern that residual groundwater might have entered the pipeline during our installation activities.
Did you know the mattress industry is one of the oldest continuous industries in the world? The first mattresses were believed to have been manufactured in 37 BC in Persia. Today, more than 35 million mattresses are shipped world-wide to replace those that have been in service for an average of seven years. So, what does this have to do with Ductile iron pipe (DI pipe), you ask? This article will discuss how setting improper bedding in a pipe trench can cause sleepless nights for the water company and its crews due to pipe failures, seemingly always at night — as it is my experience that most large main breaks typically occur after dark!
This entry in the Iron Strong Blog compares the performance of Ductile iron pipe (DI pipe) to Polyvinyl Chloride (PVC) pipe against cyclic pressure variations in piping systems. Cyclic loading, or more accurately, cyclic surges, is a phenomenon where pressures in a pipeline frequently vary due to changes in demand, operating conditions, storage tank levels, treatment plants, and pump starts and shutdowns. Surges can also occur during common field operations such as exercising or flushing fire hydrants or valves within the system, which can drastically change flow parameters, causing surges or water hammers.
In a continuous effort to make your job easier, we are constructing an online submittal builder to quickly and neatly package your personalized presentation. Stay tuned!
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