Oct 04, 2006

Risk Vs. Progress

Change frequently induces strong emotions. A positive response to change opens the mind to innovation, efficiencies and improvements to the quality of life. A negative reaction yields fear, anxiety, anger and stagnation.
Change always involves some level of risk, but risk is a requirement for progress. If we were never to take a risk, we would still be building structures out of mud and stone.
Pipe, like numerous other products in the world, has seen a great deal of change over the past century. Many of the innovations came through the development of new and improved designs, materials and cost efficiencies.
As with any such evolution, change has resulted in the discontinuation and replacement of older, antiquated products with higher quality, less expensive and better-performing products. The stage of evolution we’re experiencing today—the shift from reinforced concrete pipe for storm water drainage to corrugated high-density polyethylene (HDPE) pipe—is no different than similar industry transformations we’ve seen in the past.

Rigid to flexible

One such example was the development of ductile iron pipe. In the late 1960s, the cast iron pipe industry was steadily losing its water pipe market share to a less expensive rigid pipe alternative—prestressed concrete cylinder pipe. The risk to the cast iron pipe industry was apparent: It would either have to evolve or be replaced by a less expensive product that would meet the performance requirements of the design engineers and municipalities.
Design engineers at the time knew cast iron pipe was still an excellent product, but it was no longer cost-effective compared to the new challenger. Yet, rather than succumbing to this new competitor, the cast iron industry invested significant time and money in research and soon developed a new product: ductile iron pipe.
This innovation changed rigid iron pipe to a flexible iron pipe, and in so doing created a high-performance, more cost-effective alternative to prestressed concrete cylinder pipe.

Adapt or fail

Not all industries demonstrate the fortitude to accept the challenge to change and make the necessary investment to stay relevant. A classic example was in the sanitary sewer market. Vitrified clay pipe was the most dominant player in this market for more than a century.
Yet, in less than a decade, clay ceded over 90% of its market to a new, innovative product—PVC pipe. The clay pipe industry refused to accept the fact that its product had poor joints, short lengths that exacerbated this design weakness and the reality that it was heavier and more expensive than the modern plastic pipe alternative.
Rather than adapt their product to meet these new higher expectations, the clay pipe industry reacted emotionally. It initiated a negative promotional campaign to disparage the image of PVC pipe by raising risk factors associated with using this newly developed flexible pipe.
Scare tactics typically have an initial impact, but they are always short lived because they ignore and attempt to mask the truth. Sure enough, PVC pipe’s superior joints, lower cost and ease of installation eventually overcame the fear tactics employed by the clay pipe industry. Clay pipe inherently is a good product, but no longer competitive.

An engineered risk

In the storm sewer market, the current dominant product is reinforced concrete pipe. Much like cast iron and clay pipe, concrete pipe is losing market share to new products that provide high-performing, cost-effective alternatives to the design needs of the specifying community. Corrugated HDPE pipe, with its strong joints, corrosion and abrasion resistance, ease of installation and design efficiencies, represents a very viable and proven economic alternative to concrete pipe.
Corrugated HDPE pipe evolved and improved over time to accommodate the ever-increasing demands of the engineering community. Originally designed in 1966 as a subsurface agricultural drainage product, its wall designs, material resin composition and joints have constantly changed to improve structural, hydraulic and durability performance.
The major redesigns and significant investments in equipment and tooling had to be correct, or else the manufacturers would be left with very expensive boat anchors. As in virtually every developing technology, some miscalculations were made initially, but ultimately the risks paid off with a product that many now consider one of the best-engineered products in the pipe industry.
As the newest pipe product developed during the age of computers and automation, corrugated HDPE pipe has had more finite element engineering and pure research studies conducted on its structural performance than possibly all other pipe products combined.
It also undergoes more testing on raw materials, finished product and installation integrity than any other pipe material. Corrugated HDPE pipe is cold-climate-impact tested; laboratory deflection tested; watertight joint pressure tested; field inspected and deflection tested; and also tested for environmental stress cracking.
More traditional products, such as concrete pipe, may rely too much on past performance, rather than continuous laboratory and field testing, for their acceptance. This lack of constant scrutiny, with its associated checks and balances, may result in deterioration in the quality of the product and its long-term performance.
Reinforced concrete pipe is classified by D-load strengths, but published acceptance criteria in both ASTM and AASHTO specifications only require testing a concrete cylinder for product acceptance. Because a finished product test is not required, the variability involved with steel placement could easily result in a concrete pipe not having the appropriate strength for the design installation. In this case, the risk associated with specifying concrete pipe could be much higher than that for the highly tested corrugated HDPE pipe.
This risk is further elevated because, unlike the flexible corrugated HDPE pipe, concrete pipe is a rigid pipe and relies to a much greater extent on the structural strength of the pipe to carry the majority of the soil overburden.
Since all buried pipes are components of soil-structure interaction systems, the degree to which soil arching reduces the direct load applied to the pipe varies.
Concrete pipe does have the benefit of requiring installations with high-quality, high-density backfill to reduce the loading on the pipe, and thereby, the required D-load strength. An installation of this type would certainly provide a higher safety factor to account for manufacturing variations. In effect, it would be an installation essentially identical to that for corrugated HDPE pipe.
Given these facts, one would have to truly question which product has the higher safety factor.

Warranties & risk

Much has been made over the years about reducing a specifier’s risk through the use of product warranties. These warranties are beneficial, but are no different than any you receive for products purchased for your house. They warrant the workmanship and quality of the product, not how they are used.
If one were to purchase a copper water pipe and place it near an exterior wall without insulation, the resultant failure of a frozen and subsequently broken pipe is not inherent to the pipe. Most pipe manufacturers supply warranties on their products. As in the previous example, however, installation and use is totally outside the control of the manufacturer.
Pipe soil-structure interaction is exactly that; it is a composite system requiring a balance between soil and pipe-load resistance. It is the contractor’s responsibility to obtain and apply the appropriate installation integrity specified by the design engineer by properly compacting the backfill materials. It is for this reason that design engineers require contractors to post a bond for their workmanship.
This risk factor has little to do with the pipe specified, as all pipe must be properly installed to perform well. This aspect of the design is solely controlled by the contractor, regardless of pipe type.

Scare tactics

Today, engineers are being subjected to the same scare tactics about corrugated HDPE pipe by the concrete pipe industry that the clay pipe industry employed in their dealings with PVC pipe. This is unfortunate when we know the positive outcome realized by evolving and developing better products.
Instead of evolving, the concrete pipe industry meets the economic challenge by reducing their costs, changing material and design specification to allow unlimited use of fly ash in lieu of cement, reducing reinforcement requirements and decreasing embedment integrity.
Cheapening a product or its installation does not improve its performance, nor do negative promotional campaigns based on fear.

Flexible benefits

It’s no accident that all the past and present challenges to the established water, sanitary sewer, storm sewer and natural gas distribution products reflect a general referendum on flexible versus rigid pipe design and a movement to engineered polymers. These products provide, and at times surpass, the integrity demanded by the specifying community and at a lower economic cost.
The real risk comes in not exploring alternative technologies that can improve performance, efficiencies and cost. Our country has become the economic world leader due to the freedom to innovate and provide better and more economical alternatives in virtually every aspect of commerce.
All of the advancements we enjoy today, from air transportation and satellite TV to digital music and even indoor plumbing, were brought on by testing new theories, evaluating new materials and developing new manufacturing processes. By moving forward, innovators assume leadership positions in their industries and avoid being dumped on the ash heap of history.
That’s not risk; that’s progress.

About the author

Radoszewski is the executive director of the Plastics Pipe Institute. He can be reached at 202/462-9607 or by e-mail at [email protected].