Overwhelming Proof Of A Corrosion Threat Does Not Always Produce The Appropriate Response Preface
A chemical water treatment company acquires a new contract for an older building property known to have not been well maintained or chemically protected. Large rust and scale deposits are found in all strainers and have accumulated throughout the system. The condenser water piping system is fully drained for freeze protection annually, which further suggests a high corrosion loss.
Upon entering their agreement with the building owner, the water treatment representative suggest an ultrasonic investigation of the 50 year old condenser water system in order to learn of any threats potentially impacting their planned chemical cleaning and treatment program.
The chemical treatment company recommends the services of CorrView International, LLC and a contract directly with the building owner is produced. Our investigation shows a moderat to high average corrosion rate of near 5-6 mils per year (MPY) and more severe pitting at the bottom of all horizontal lines likely due to the accumulation of heavy rust deposits. All pipe is heavily impacted due to the fact that it is fully drained every winter season. A visual inspection of a section of exposed condenser water pipe opened in order to attempt to remove deposits interfering with water flow shows approximately 3 in. of rust product at the bottom of the cooling tower supply and return headers.
We estimate that extra heavy pipe was originally installed having an initial wall thicknes of 0.500 in. With wall thickness at many examples of large 18 in. condenser water pipe near 0.200 in., more than half of the pipe in some areas has been corroded away. Identifying some areas of roof level pipe down to near 0.100 in., it becomes clear that the larger main lines will soon require replacement. Still, this finding represents a significant length of trouble free service for a building operating under less than ideal water treatment and maintenance conditions.
Further testing at the individual A/C units served by the main riser produces far greater concern. Here, the 50 year old and originally extra heavy threaded pipe has deteriorated down to near or below minimum acceptable limits. All distribution lines are threaded, which for pipe at 3 in. and 4 in. diameter means a 0.105 in. thread cut loss. After 50 years of service, we identify a substantial number of pipe locations having a current wall thickness of near 0.140 in. or below, and dangerously close to the point where a total pipe separation might occur.
With pressures of near 175 PSI at the lower floors, significantly greater threat is possible due to a 3 in. or 4 in. take-off line separating completely at its threads, in contrast to a pinhole leak at the main riser. Our recommendation is to immediately replace every section of threaded pipe prior to its first reliable isolation valve from the riser, then replace all threaded run-out piping, followed by larger scale planning to replace the main risers entirely. With a large scale project defined, we recommend beginning the replacement of the run-out piping at the lower floors given its greatest and most immediate threat to operations.
The building owner doubts the results of the CorrView report and hires another ultrasonic testing service to check and verify our results. The UT company reviews the 186 page CorrView report consisting of over 75 sets of test data taken throughout the entire building and selects one single area of 18 in. main condenser water pipe for further testing. They take 6 wall thickness measurements in the general area referenced by the CorrView report, and covering approximately 4 ft. of a 18 in. cooling tower supply header.
The company does not measure or identify the lowest 0.102 in. wall thickness documented in the CorrView report within their 6 thickness measurements taken, and consequently produces a scathing report to the building owner totally disissing the CorrView report. No further statistical analysis of the 6 wall thickness measurements is produced, with only a listing of the 6 wall thickness measurements submitted. Results state that wall thickness measurements produced in the CorrView report could not be verified, and that the entire report shuld be discounted as in error.
The building owner submits this critical review to the chemical water treatment company in criticism to their recommendation of CorrView International, LLC, with the letter then forwarded to our office for comment.
We return to the subject property and to the area in question. Within approximately 30-40 measurements and approximately 10 minutes of investigation we again find the 0.102 in. low wall thickness documented in our original report. Further scanning, now approximately 6 months after testing had been first performed, identifies even lower wall thickness measurements of 0.095 in. at this 18 in. condenser water pipe. The very specific areas containing the 0.102 in. and 0.095 in. wall thickness measurements are circled and clearly marked with their dimensions using spray paint. Photographs are taken of the pipe location and its measurements.
A follow-up report is then submitted to the property owner and chemical treatment company documenting the confirmation of our prior findings, as well as even lower wall thickness measurements now 6 months after first measurements were taken. We again state that a failure of the main risers due to pitting will likely be in the form of a small pinhole, whereas failure at the 3 in. and 4 in. threaded run-out pipe to the units is likely to be a catastropic thread separation, and occur at a lower floor operating under higher pressures.
The building owner submits the original CorrView report, the critical review by the other UT contractor, and our follow-up letter to a well known and respected independent 3rd party water treatment / corrosion consultant for his review and recommendations. The consultant, (as CorrView would surprisingly learn many years later in working together at another building property), raises serious concern for their building and reiterates prior CorrView recommendations to immediately replace all threaded pipe as the minimum action required. The consultant emphatically warns to the potential of a catastrophic failure of the condenser water piping.
The building owner discounts the recommendation of the water treatment consultant, and follows the recommendation of a 1 page report based upon 6 wall thickness measurements over CorrView’s 186 page report covering 75 sets of data and an approximate 1,300 wall thickness measurements, and follow-up rebuttal firmly documenting the error by the 2nd ultrasonic testing firm. The building takes no actions to repair the piping.
Approximately 8 months from the date of our original report, on a Sunday night at 2:45 AM, a 4 in. threaded nipple at the main riser separate completely separates to drain the entire cooling tower system through 7 floors of computer room and library storage tenant space on its way to the lobby. By the time the make-up water is shut down and the 18 in. risers drain 26 floors down to the 7th floor, approximately 6 in. of water is in the lobby and cascading out the front doors down the street. The failed pipe section is later shown to be one which had been ultrasonically tested by CorrView and specifically identified in our report as in need of immediate replacement 8 months prior. Damage estimates exceed $900,000, with final damages and lawsuit claims unknown.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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