If you were to work at a firm for 50 years or stay married to the love of your life for 50 years, would you say that was a remarkable milestone? Would one consider this to be a life time of service where congratulations are in order? So, tell me, when a design engineer chooses to use a pipe product that has an anticipated design service life of 50 years, and it lasts that long, is that not also a remarkable service life? Did the engineer of record expect it to last forever? Do you?
The product that I am referring to is an industry standard, corrugated metal pipe (CMP). The original patent for this product was filed in 1896. There have been many upgrades in the past century and major improvements to this strong, lightweight pipe that have enhanced CMP as a long-term design life solution.
In 1952, over 100 locations were identified across the country to use as test sites for the improved CMP coating materials. In the same location galvanized CMP was buried alongside aluminized CMP pipes. The design service at that time was approximate 50 years for CMP. The Army Corp of Engineers inspected these systems and reported in 1988 a service life of 50 years, in 1995 they adjusted their finding to an improved 75 years. Note, these pipes are still being evaluated today.
Keep in mind, site conditions have a strong impact on the longevity of the pipe. Just as in a 50-year marriage, chemistry matters. On the soil side of the pipe: acidity (PH), soil resistivity, soil aeration and soluble salts influence design decisions. On the water side of the pipe: ground water infiltration carries PH and soluble salts, surface water may contain pollution, abrasion due to bed load, and possible water pooling loads. The actual application of the drainage pipe, whether it be an open-ended culvert or a closed stormwater system, can also impact the CMP product chosen. When all these parameters are understood and accounted for, CMP can be designed to meet and exceed service life requirements
The National Corrugated Steel Pipe Association (NCSPA) provides design support when evaluating and choosing a CMP pipe. The first question the pipe service life calculator will ask is “what is your design life required”? If it is 75-100 years, then there is a high likelihood that CMP pipe can make the commitment.
There are several pipe developments that can help you achieve a century of service:
Aluminized Type 2 pipe became commercially available in the late 70’s. This pipe, when used in the appropriate environmental conditions, can provide 2x to 5x the service life of galvanized CMP. The steel-aluminum forms a hard dense alloy layer to improve abrasion resistance.
Aluminized or Aluminum ULTRA-FLO® pipe with a smooth interior wall (Manning’s=0.012) helps flow to slide through the pipe for storm sewer applications. It also forms a self-=healing oxide layer that works well in brackish or salt water environments.
Polymer Coated CMP, with soil and water side coating designed by Dow Industries, provides a protective layer to combat against harsh soil or water conditions and/or abrasion and can provide a 100-year service life within most environments.
Aluminum Pipe moved to commercial use in the early 80’s. This pipe works very well in chlorine and sulfate salt environments.
Galvanized Pipe – This economical pipe, when used in the appropriate environmental conditions, at minimum can provide more than 50 years’ service life. This is the most common culvert pipe coating.
Next time you design with CMP, do yourself a favor and check your site chemistry, choose an appropriate pipe coating, and ensure proper installation to extend the life of your drainage pipe. In 100 years, someone not yet born will be commenting on your remarkable choice of a 100-year performance milestone.