Is hydrogen embrittlement putting your PCCP at risk?

Introduced in the early 1940s, prestressed concrete cylinder pipe (PCCP) is the backbone of many modern water transmission systems. In fact, if all the PCCP installed today were laid end-to-end, it could span the width of North America eight times over.

Water has reliably flowed through some of these PCCP pipelines for nearly a century, and inspection shows that most PCCP is in good condition. This durability comes from high-strength steel prestressing wires wrapped around the pipe core under extreme tension.

However, when prestressing wires lose their ductility and toughness, the consequences can be severe. The vast majority of PCCP failures are due to broken wires, and one of the most significant threats to these wires is hydrogen embrittlement (HE).

Impact on pipeline integrity

Hydrogen embrittlement occurs when steel absorbs hydrogen, making it brittle under stress. In PCCP, this affects the prestressing wires. HE can arise from manufacturing defects or develop after installation, often linked to improperly designed or operated cathodic protection systems.

Pipes manufactured in the 1970s with Class IV reinforcing wire are especially vulnerable, but HE has been observed across nearly all PCCP vintages. Over time, embrittlement leads to wire fractures, structural weakening, and in worst cases, sudden pipe ruptures.

Detecting hydrogen embrittlement

For utilities with PCCP, understanding whether deterioration is caused by HE helps inform an effective management strategy. Here are three possible steps to confirming the presence of HE:

01. Evaluate distress levels

Advanced inline inspection tools can assess the pipeline’s current condition and identify the number of broken wire wraps on each pipe. Pipes with HE often exhibit higher rates of distress.

02. Investigate with field forensics

Field forensics can provide initial clues about whether distress is caused by HE. Typically, HE results in brittle wire breaks scattered across the pipe. A classic brittle wire break is clean with little visible corrosion and potential longitudinal splitting. However, corrosion can develop on brittle wire breaks when the pipe’s mortar coating is damaged, making visual identification more challenging.

^{Image A shows a classic brittle wire break. However, the corroded wire in image B came from the same pipe. These images demonstrate the challenge of visually identifying HE in pipes with more severe distress.}

For cases where full pipe excavation and destructive testing aren’t feasible, wire continuity testing can indicate the presence of HE by analyzing the scatter pattern of wire breaks.

03. Confirm with laboratory testing

To confirm the presence of HE, laboratory testing of wire samples following ASTM standards is necessary. Utilities should collect and submit multiple clean wire segments, each at least 18 inches long.

Managing risk when hydrogen embrittlement is present

Proactive management strategies for PCCP with HE include:

• Operational changes: Reduce operating pressure and mitigate pressure transients to minimize stress on the pipeline. Assess and adjust cathodic protection systems to prevent further embrittlement.
• Point repairs: Inspection data and engineering analysis can help utilities make targeted repairs on specific pipes.
• Section repairs: Larger-scale repairs, such as slip lining or replacing full sections, may be necessary.
• Continuous monitoring: Detect wire breaks as they occur to plan repairs proactively.

The role of continuous monitoring

PCCP can sustain more scattered wire breaks before reaching a structural limit compared to concentrated, corrosion-induced wire breaks. However, the progression of deterioration on pipes with HE can be highly unpredictable. Given the catastrophic consequences of PCCP failures, extending the life of pipes with HE while effectively managing risk requires ultra-high-resolution detection systems.

Xylem’s SoundPrint AFO continuously listens for wire breaks along the pipeline. When a wire break occurs, the system captures acoustic data, pinpoints the location, and sends near-real-time alerts to utilities. SoundPrint AFO enables utilities to closely monitor the health of their pipeline without the need for repeated inspections.

Rehabilitation or replacement?

HE poses a silent threat that can lead to sudden, costly failures. Deciding whether to repair or replace a pipeline with HE depends on the severity and location of damage. If wire breaks are isolated and structural integrity remains intact, targeted repairs and monitoring can extend service life. However, when HE is widespread and integrity is compromised, replacing the full pipeline or larger sections may be necessary. High-resolution condition assessment can help utilities make informed choices, balancing risk, cost, and operational continuity.

Take action today

If you’re seeing elevated wire break counts, suspect HE, or operate PCCP from HE‑prone eras, our team can help you assess risk and prioritize action.  Contact Xylem’s Pure Technologies team today to schedule a condition assessment and build a long-term strategy for your PCCP network.

_{Authors: Ashan McNealy, P.E., Manager of Condition Assessment Engineering at Xylem and Brianne Nakamura, P.E., Global Product Manager at Xylem}