As one of the most depended on resources in the transport of water and wastewater, large diameter Prestressed Concrete Cylinder pipes (PCCP) pipes make up a large portion of highly critical pipelines running throughout North America. Constructed with a cement-lined thin steel cylinder, PCCP pipes rely on high-tensile-strength, helically wound wires to provide structural strength and prevent bursts.
Despite being known as a highly durable option, PCCP pipes should be regularly inspected to detect and quantify wire breaks, cylinder corrosion and loss of pre-load before they have the opportunity to cause catastrophic failures. Below, we’ll discuss a few of the common factors that can lead to PCCP pipe failures, as well as give a brief overview as to how to conduct an efficient inspection. Read on to learn more.
What Are the Main Sources of Damage
If you’re under the notion that the main source of PPCP pipe failures is broken pre-stress wires, you’re not alone. However, while broken wires certain do cause issues, there are actually a wide number of issues that can lead to breaks in the line. Such factors typically fall into three distinct categories:
Environmental
Due to the fact that most PCCP pipe is buried, a large number of failures occur because the soil is corrosive. Chemical elements such as chlorides, sulfides and sulfates can be found in most soils to varying degrees. These can originate in road salt, fertilizers, petroleum and carbon emissions from traffic. Over time, these chemicals can slowly degrade and corrode the exterior of the pipe and cause the mortar coating to crack, leaving wires and the cylinder vulnerable to corrosion damage.
As well, stray electrical currents from nearby utilities (other pipelines, railway lines, electric wires etc.) can cause corrosion in the wires and cylinder. In most cases, this kind of damage is localized to the area of the stray currents.
PICA’s wire stress inspection tools are able to detect corrosion and hydrogen embrittlement of the wires and cylinder, giving you ample time to treat the issue before it spreads and causes failures.
Construction Issues
PCCP pipes made with poor wire or concrete quality can often have increased susceptibility to ground water corrosion. Other construction issues include undetected coating damage, fabrication and construction damage, poor welding jobs, inadequate joint restraint, and more.
Progressive Wear and Tear
Even with the most diligent care, ageing takes its toll on any line, especially if pipes are exposed to pressure surges and ground movement. Frost heave and the wet/dry cycle of clay soils can move the pipes around under the surface, even pulling pipe joints apart where settlement is severe or the pipe slowly creeps down a side-hill. Such factors, along with hydrogen sulfide concentrations in wastewater pipes will slowly eat through the pipes and corrode through the concrete liner and steel cylinder, leading to failure.
Stop Issues Before They Spread
Due to the larger size of most PCCP lines, sudden failures can be catastrophic to both your job site, as well as the surrounding community. With the potential for fines and extensive cleanup costs looming, prevention through regular inspection is one of the best ways to avoid such issues.
PICA Makes Inspection A Breeze
PICA Corp understands the inherent risks associated with PCCP Pipe failures and is proud to be a leading supplier of inspection services for customers worldwide such as San Diego County Water Authority. Our advanced selection of inspection technologies, including our EMIT and RAFT tools, provide reliable, high-resolution data that you can count on, catching signs of corrosion and cracking early on. PICA’s reputation for excellence has made us the valued partner of multiple counties, cities, and industry leaders throughout North America. Learn more about our CCP and PCCP solutions by contacting us today!
Source: How to Perform PCCP Condition Analysis with Confidence picacorp.com • 3 min read
