Failure Analysis

Establishing The Severity And Extent Of A Corrosion Problem After A Piping Failure

A piping failure can produce a substantial volume of damage in a relatively short period of time.  While most water leaks are relatively small and can be easily repaired, the most extensive pipe breaks can cause damages of $5 million or more.  The failure of a 4 in. pipe section operating at 200 PSI, a pressure common to most high rise office building properties, will release over 3,500 gallons of water per minute.

The response to a piping failure may be as small as a pipe clamp and the hope that it will not happen again, to a full blown investigation followed by pipe replacement, repairs, and / or corrective actions.  Five questions are tpyically raised in response to a pipe leak:

  1. What caused the failure?
  2. How extensive is the problem?
  3. What is the condition of the pipe?
  4. What is the remaining service life of the piping system?
  5. What actions should be taken?

Investigative Options

While all five questions are inter-related, answering them often requires different disciplines.  A pipe failure at a grooved clamped fitting, longitudinal or circumferential weld seam, fixture such as strainer or PRV, or other individual component suggests a localized failure best defined by submitting the failed item for metallurgical analysis.  Every failed piping component should be saved for inspection, although remarkably, the answer to many pipe failure problems are just thrown away.

A general rule of investigation is that where the failure can be isolated and the pipe section or component removed, submitting that example to a metallurgical laboratory for failure analysis is unquestionably the best first step.

Where no specific failure location has occurred, such as commonly where heavy rust deposits exist without a failure condition, then ultrasonic testing is often the best first step.  Ultrasonic testing allows the evaluation of a large number of piping locations from which the most appropriate examples of pipe can be identified for removal should further metallurgical testing be appropriate.  Rather than selecting a section of pipe at random for metallurgical testing and basing a decision upon results which may not be representative of the system or the problem, ultrasound allows a much larger sampling of test locations from which a more accurate piping assessment is possible.

Ultrasound provides a cost-effective method of establishing total pipe condition at approximately 1-2% of the cost to cut out pipe samples for metallurgical testing.  Ultrasonic testing followed by the metallurgical analysis of specific pipe samples, is the best procedure to follow in defining most corrosion problems; providing a baseline assessment of pipe condition followed by a visual confirmation to the ultrasonic results.  Property performed, the raw ultrasonic thickness data can be analyzed to provide an estimate of corrosion loss and subsequently an estimate to the remaining service life of the system.

Even where extensive service life may be indicated, most investigations will result in recommendations toward system improvement.  Where ultrasonic analysis shows severe pipe deterioration beyond repair, pipe replacement is often the only answer.  Generally, however, investigation is prompted by one or more physical failures or suspicion to a problem likely resulting in some corrective recommendations.

Other Interests

Far too often, mistaken or self- benefitting influences direct attention to corrective actions that may not be appropriate, or worse – will prevent the needed investigation into the source and extent of a problem.  To a high corrosion problem, filtration representatives will cite the need for filtration, chemical suppliers may suggest a modification in the chemical treatment program, mechanical contractors will recommend pipe replacement of the affected area or direct attention to a suspected cause – such as the need for dielectric fittings.  All such speculative corrective recommendations, without a solid understanding of current pipe condition, frequently waste valuable time and resources to actually correcting the problem at hand.

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Dead Zones

The Leading Cause Of Pipe Failure At Condenser Water Systems

Despite various corrective measure, advanced failures at condenser water systems are on the rise. Many problems are engineered into the system from the start due to the failure to recognize the impact rust deposits and particulates have on producing higher secondary corrosion levels. In addition, most corrective measure, if they are attempted, fail to provide a solution. Here is why.

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Undersized Steel Pipe

A Simple Dial Caliper Measurement Of New Steel Pipe May Reveal Surprising Results

In addition to the many corrosion influences negatively impacting piping systems, many new building properties are constructed using carbon steel pipe which is below factory specification. To the surprise of many, an FM or UL approval, like its ASTM stamp, does not define that the pipe actually meets ASTM thickness standards.

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Inevitable Corrosion

The Decline In The Quality Of Today’s Piping Products Means Greater Corrosion Problems

A large number of negative influences have comined to produce a higher frequency of corrosion problems – often in spite of all precautionary measures taken. Of those, lower quality pipe, undersized pipe, more complex piping layouts, and generally less effective chemical treatment options have produced a “Perfect Storm” contributing to more piping failures.

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Corrosion Threats

When Pipe Corrosion At A Fire Protection System Can Cost Lives

The time to learn of a fire pipe corrosion problem is not during an actual fire emergency. Internal rust deposits can, and have, totally blocked water flow through the sprinkler heads – resulting in the loss of human life. More common at dry systems, internal deposits are a serious threat to all fire protection systems.

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Fire System Failures

Major Misconceptions Within The Fire Protection Industry

Ignoring the obvious does have serious consequences when it comes to fire protection systems. From the use of thin wall schedule 10 & 7 pipe, to lower quality pipe products, to frequent flow testing which brings in new fresh water, clear and well documented reasons exist to explain the higher corrosion activity found at today’s fire protection systems.

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Fire System Corrosion

The Threat Of A High Corrosion Condition To A Fire Sprinkler Line

Often viewed only in terms of water damage in the case of a corrosion induced pipe failure, far more serious concerns exist, although rarely considered. Unlike HVAC piping systems, corrosion activity at fire related piping can impede and in some cases totally block water flow – a potentially life threatening condition during any fire emergency

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Ultrasonic Testing

The Benefits of Ultrasonic Testing in Determining Corrosion Rate and Service Life

Ultrasonic testing provides the most comprehensive, accurate, and cost-effective tool to assess the condition and remaining service life of any piping system. Planned and performed properly, ultrasound offers the first step toward identifying a potential corrosion problem, or for certifying a piping system as fit for service.

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Corrosion Influences

Why Not All Pipe Failures Are The Fault Of Your Chemical Water Treatment Provider

Various design elements to any piping system can have dramatic impact upon its corrosion activity. Pipe origin, schedule used, physical layout, and many other unknown factors can produce a pipe failure. And yet they are completely beyond the realm of protection offered by chemical water treatment.

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Corrosion By Design

Pipe Corrosion Problems No Water Treatment Program Can Protect Against

Various changes have occurred to mechanical piping designs over the past few decades, with virtually all HVAC, plumbing, and fire protection systems having been affected in some way. Many changes relate to the materials themselves. Major changes in piping design, however, have introduced new corrosion problems no chemical treatment program can stop.

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Corrosion Coupons

The Benefits and Limitations of Corrosion Coupons

Relied upon for decades as an indicator of corrosion activity within piping systems, corrosion coupons are highly unreliable in most examples, and totally worthless in others. Many of the most damaging corrosion failures have occurred while at the same time corrosion coupons produced excellent results. Here is why.

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Unexpected Failures

If Corrosion Activity Is Only 0.4 MPY, What Is Wrong With The Above Picture?

Corrosion coupons reported a 0.4 MPY corrosion rate for 6 years where the actual rate exceeded 25 MPY. Believed implicitly in contrast to multiple leaks and failures, the slow but total destruction of the entire condenser water piping system was the net result. A case history illustrating the threat from relying exclusively upon this highly flawed testing method.

Dry Fire Sprinkler

Fire Protection Contractor – Antifreeze: The Fine Line Between Hero and Defendant

Antifreeze used in dry fire sprinkler systems may solve one problem, but has also proven deadly. Rated a Class 1 flammable liquid, antifreeze can accelerate a fire, create a fireball, and even cause an explosion. Although now restricted to lower concentrations, antifreeze still adds heat value to any fire and introduces new and unknown liability to any such system.

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Corrosion Trends

American Welding Society – Understanding Pipe Corrosion Problems

A piping system that satisfies service life demands, requires the recognition of piping design vulnerabilities, effective corrosion monitoring, and the adoption of corrective measurements. With corrosion related failures on the rise, and with generally lower quality pipe being installed, advanced planning and an awareness of potential threats becomes more important.

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Testing Procedures

World Pipelines – Investigation vs. Procedure

Substantially different findings are likely where ultrasonic pipe testing is approached as a forensic investigation based upon known system problems and vulnerabilities, rather than simply a linear based measurement procedure. A critical importance is understanding the inherent corrosion related problems to various piping systems. An adapting investigation will also produce a more definitive answer to any piping problem.

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Fire Pipe Corrosion

Fire Protection Contractor – When Pipe Corrosion In a Fire Protection System Can Cost Lives

The time to first learn of a pipe corrosion problem is not during a true fire emergency when lives are in jeopardy. Thinner pipe, more corrosive steel, lower quality galvanizing, foreign pipe, dry systems, MIC – all such negative factors are driving toward higher internal corrosion deposits to render your fire protection system worthless.

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Ultrasonic Testing

Fluid Handling Systems – Finding The Remaining Service Life

Ultrasonic testing is, by far, the most informative diagnostic method available for determining pipe status, as well as extremely cost effective. An effective piping analysis is much more than a spreadsheet of a few wall thickness measurements – requiring careful statistical analysis and practical interpretation of the data.

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Pipe Corrosion

World Pipelines – Multiple Metering And Monitoring Needs

With no single form of corrosion monitoring capable of proving full coverage to the many different forms of pipe corrosion possible, multiple testing methods are always advised. These should include ultrasonic testing, spool pieces, LPR, regular internal inspection, and a close observance to the often obvious but missed signs of a problem.

A 30+ Year Knowledge Base

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Corrosion

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Failure

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Repair

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Replacement

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Unfortunately, the above is a very common progression of events for many of our clients. Often, greater attention to chemical corrosion control and corrosion monitoring could have saved the system and avoided the problem. In others, a decades prior design flaw or poor choice of pipe supplier may be traced back as the primary fault.

During the 20 years that we have been involved in the field of ultrasonic pipe testing / corrosion monitoring, we have authored various Technical Bulletins for the benefit of our clients. These Technical Bulletins address frequent problem issues to any building owner or operator, and offer both insight as well as reasonable and proven solutions.

We offer below the various categories available, and continue to add new bulletins as time permits.

Current Categories

Interior Rust Deposits, Common Threats, Corrosion Types, Winter Lay-Up, MIC, Corrosion Monitoring and Testing, CUI, Corrosion Coupon Failures, Rust Removal, Reducing Corrosion Threats, Roof Level Corrosion, Drained Pipe, Corrosion Trends, Fire Sprinkler Corrosion, Corrosion At “Free Cooling” Systems


The Impact Of Flow Rate To Higher Corrosion, Inadequate Water Filtration, Piping Layout Design, “Green” Piping Designs


Corrosion Threats, Design Misconceptions, Interior Rust Deposit Threat, Dry Fire System Corrosion, Schedule 10 Pipe, Premature Failures, Clogged Fire Systems, Chemical Control Options, Remediation Choices


Condition Assessment, Due Diligence, Preparation Prior To Renovation, System Evaluation, Expert Witness


Heat Exchangers, Benefits of UT Testing, High Pressure Water Jet Cleaning, Filtration Errors, Chemical Treatment, Condenser Tube Coating, Mold Concerns, Chromate Removal, Growing Threat of Corrosion, Heat Exchanger Tub Coating, Nondestructive Testing


Schedule 40 Limitations, Piping Trends, Hidden Corrosion Threats, Dielectric Insulators, Clamped Grooved Piping, Piping Schedules, Pipe Testing Specification, Roof Pipe Draining, Low Corrosion Guidelines, Dual Temperature Piping Failure


Cold Water Threats, External Corrosion Issues, Fire Reserve Tanks, Interior Pitting, Protective Coatings, Rehabilitation


Improving Heat Transfer Efficiency, Improving Filtering Efficiency, Filter Placement, Poor Performance Causes, Filter Selection Considerations


Chemical Treatment Challenges, Limitations to Water Treatment, Corrosion Coupon Reliance