Causes of PCCP (C301) Pipeline Failure
PCCP (AWWA C301) pipe are widely used for water mains and wastewater lines. There are two types of line that are widely used for water mains and wastewater lines. PCCP pipe consists of an inner core of concrete, a steel cylinder is places around the concrete line, then pre-stressing wires and a mortar coating are layered. C303 pipe is similar, but it differs because instead of being wrapped in wire, steel bars are used instead. These lines carry a lot of fluid and the purpose of these pipelines is to prevent corrosion.
They have countless benefits but also need to be inspected and monitored for the myriad of issues that can occur with these pipelines.
Benefits of Pre-stressed Concrete Cylinder Pipe (PCCP) Pipelines (according to the manufacturers):
- Can be installed efficiently
- Cost less to install than metal pipelines
- Reinforced with wire or bar so they are strong
- Exceptional corrosion resistance
- Can resist high internal pressure
- Can handle high external loads if the pipe is buried
- Available in diameters 120" or larger
Inspection of PCCP pipes
Many pipeline inspection companies focus on the condition of the wire being used (i.e. number of breaks), some even obtaining patents on their technology for this purpose, but there are a number of good reasons why PCCP pipes fail that are unrelated to simple wire breaks, such as:
- High chloride content in soils
- Corrosive soils due to sulphates, high water table, organics and oxygen
- Delamination of the mortar coating
- Inadequate mortar component leading to cracking or spalling
- Poor concrete quality – low density, low thickness, and low cement content
- Unrepaired coating damage
- Fabrication and construction damage
- Poor welding of the wires or the joints
- Poor bedding leading to cantilever (bending or broken back)
- Inadequate joint restraint – pipe moved exposing joint to environment
- Loss of pre-stress due to core under-design strength at time of pre-stressing or due to wire breaks and splicing.
- External load
- Hydrogen sulfide (H2S) in wastewater applications attacking the steel can
- Pressure Surge – unanticipated and above design value
- Cracking of concrete
As you can see, there are many factors that can lead to the failure of PCCP pipelines, not just the deterioration of the wires. In a recent study by the American Water Works Association (AWWA) they state that "a large diameter pipe failure typically costs a utility between $200,000 and $1,500,000, including ancillary damages. Thus while the distress rates are low, it’s important to find deteriorated pipe and implement corrective measures."
PICA Corp. is able to conduct inspections and utilize the latest technology to monitor pipelines for the following issues.
- Evaluation of structural integrity
- Detection of corrosion on the steel can
- Visual inspection for internal anomalies
- Detection of leaks
Contact PICA Corp. at 1 (780) 469-4463 or by e-mail firstname.lastname@example.org to schedule an inspection of your PCCP (AWWA C301) pipeline today.