An Unknown Threat Unexpectedly Revealed Through Ultrasonic Investigation
A high rise 54 story office building changes owners. When the new chief engineer takes over, he notices what seem to be abnormally high rust deposits at the package air condition units served by a central condenser water system. Soon after, CorrView International, LLC is hired to perform an ultrasonic investigation of the condenser water system. The building is approximately 20 years old and has been well maintained.
Our investigation shows low to moderate corrosion activity of near 1-3 MPY throughout all areas tested. Like many more modern buildings, multiple futures have been installed at each floor but have never been used. For some floors we identify one set of larger 4 in. distribution lines serving the floor A/C unit, and then 3-4 additional dead ended lines ranging in size of 2 in. to 3 in. In some examples a small copper by-pass line has been installed across the dead ends in the hopes of mitigating damage caused by no water flow. Most, however, are valved off and capped. In reality, such efforts are worthless and do not slow the corrosion rate.
Investigation immediately discovers a significant threat at the capped future lines. In addition to higher corrosion and pitting activity, brass valves end each line and have had a noticeable galvanic impact against the steel pipe. We identify and photograph multiple locations showing rust encrustation and bluish green discoloration around the valve side of the future which defines galvanic activity. Some wall thickness measurements are not only below minimum standards, but near the limit of the thread cut itself.
We recommend the identification and replacement of all threaded pipe throughout the entire building, and highly recommend using either dielectric fittings or heavier schedule 80 black steel pipe.
During our investigation we are advised to the existence of an above ceiling located 4 in. distribution line running the entire length of the third sub-cellar where the building offices are located. Testing in this area identifies the most severe pitting of our entire investigation and shows that the pipe is very near failure. Thickness values in many areas are near 0.115 in. or less, and with the thread cut for 4 in. pipe at 0.105 in., very little wall thickness remains for pipe operating under a pressure of near 400 PSI.
We bring this information to the attention of the chief engineer and further warn him that while performing our testing at the very bottom of the main risers where the 4 in. distribution pipe originated, there were no isolation valves. The chief engineer expresses shock at our statement, and upon inspecting the riser pipe personally, finds that the very heavily damaged 4 in. pipe has been simply welded into the side of the main risers. Any failure of this 4 in. pipe will drain both risers and cooling towers into the basement of the building.
Within a few days, the engineer performs an emergency installation of new 4 in. isolation valves at the bottom of the risers by freezing the 8 in. lines. This provides some safety margin while preparations are made to replace hundreds of feet of the 4 in. pipe routing through multiple offices. Plans are also underway to shutdown the risers and replace some of the threaded pipe.
Upon cutting apart the 4 in. sub basement distribution piping, engineers find multiple lengths of 1 x 4 wood studs inserted into both supply and return lines. For whatever reason, and likely due to some form of dispute with the contractor or between employees and their firm, steam fitters deliberately inserted lengths of wood into the pipe before threading it into place. This obstruction then slowed the flow of water down to explain the long term balancing and operation problems the engineers had not been able to correct.
Slow flows over the prior 20 years had led to the settlement of massive amounts of rust and particulates creating a severe under deposit condition resulting in the wall loss measured ultrasonically. Some lengths of 4 in. pipe fracture at their threads and separate when handled.
Months later, when the dead ended futures are replaced, engineers find that many simply snap off from the threadolets with only minor handling, requiring a re-cutting of the threads. Our final written report from ultrasonic testing had suggested this may occur, and we had recommended having thread cutting dies available in the different size pipe they were planning to replace.
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