Poor Ultrasonic Equipment, Inexperience, And Poor Operator Training Combine To Create A Non-Emergency
Our ultrasonic investigation at a large financial institution identifies weakness at their smallest diameter threaded fittings at the condenser water system. Multiple drains and vents have been installed using standard schedule 40 pipe directly connected to brass ball valves. All other results are excellent, and show the larger main pipe to be in near new condition.
Corrosion activity is low, but after 20 years of service, has reduced the small threaded nipples to near or below minimum acceptable standards. Higher corrosion and pitting is measured at the brass valve side of the small 3/4 in. steel nipples due to suspected galvanic activity, with leakage and rust encrustation at the threads common to many examples. Testing near the valve side of many pipe nipples produces low thickness values approaching the thread cut itself. We recommend the global identification and replacement of every existing threaded pipe nipple prior to a reliable isolation valve, and recommend the use of dielectric fittings or schedule 80 pipe as their replacement.
While most such fittings are at the pumps and before larger service valves where they can be isolated from the main system, there are approximately 8 threaded fittings located prior to any possible isolation. Some are on 18 in. and 24 in. piping. Freezing various lines is considered but is not feasible. We make the recommendation to encapsulate this vulnerable pipe by welding over it a 3 in. or 4 in. extension of capped schedule 40 pipe. With the valve handle removed, this simple precaution will prevent service problems when the threaded nipple eventually fails.
Within a year, the facility hires a mechanical contractor to perform the work, and all problem areas which can be isolated are easily corrected. Prior to encapsulating the 3/4 in. pipe nipples located on active lines, the contractor brings in their own ultrasonic testing firm to certify the pipe as suitable for welding.
The firm identifies severely low wall thickness in the areas where welding is planned, and recommends against welding to the pipe. Facility engineers and managers are called upon, and are informed by the ultrasonic technician that the 10 in. to 24 in. condenser water piping is extremely thin, and might fail at any moment. Further ultrasonic testing outside the 8 original areas of interest are requested by the facility whereby even worse results are stated. The ultrasonic testing firm marks its wall thickness measurements directly onto the pipe using a Sharpie marker, writes on the pipe a test location number, and hand writes on paper their wall thickness measurements for their report.
In certain areas of the 24 in. piping headers to the refrigeration machines, the ultrasonic inspector finds such low wall thickness (to below 0.050 in.) that he expresses major concern for even writing his thickness measurements on the pipe using a Sharpie. Indicating to the facility managers and engineering staff that the pipe may fail should he even gently write on it, he instead requests a tube of pump bearing grease and gently marks circles and thickness measurements onto the pipe using his finger dipped in grease.
These results throw this critical data center facility into massive panic, and raise concern that the entire refrigeration plant and all 24 in. condenser water pipe will require replacement. The facility considers immediately contracting an emergency refrigeration or cooling tower plant for the site given warning by the ultrasonic inspector that just bumping into the pipe or even writing lightly onto its surface could cause its failure.
While such preparations are considered, the facility contacts CorrView International, LLC requesting an immediate site visit.
Initial discussion with facility management more then defines the level of panic and fear which exists. Based upon what they have been informed, management and engineering are concerned that touching our thickness probe to the pipe might itself produce a failure, and inquires to whether any adjustments can be made to our field testing procedure to minimize this threat.
Management requests of CorrView International an immediate answer to the question of pipe condition given that they need to make a decision regarding the emergency cooling towers by the end of the day.
We assure everyone that there is no threat to this piping whatsoever, and that the results indicated to them previously are totally in error. We point out the results of our prior ultrasonic examination of the entire condenser water system only 1 year earlier, and where our thorough investigation of 65 examples of condenser water pipe found consistently high and uniform wall thickness measurements still at or near new ASTM specifications. This after 20 years of service. We express no doubt whatsoever that the measurements related to them by their mechanical contractor and his ultrasonic technician are completely wrong.
Ultrasonic testing is performed by CorrView International at each of the 8 areas of pipe planned for encapsulation where we identify high and uniform wall thickness approaching new standard pipe specifications. We find no indication of any pitting and no thickness values anywhere approaching the low 0.075 in. measurements reported by the mechanical contractor’s ultrasonic testing firm. Measurements are consistently at near 0.365 in. and far above the limit for safe welding.
We also re-test the threaded pipe nipples themselves to show a continued loss of wall thickness from our prior investigation – thereby reaffirming the need to perform the encapsulation of the pipe.
Testing is then performed at other areas of the 24 in. condenser water mains where the mechanical contractor’s ultrasonic testing firm had identified wall thickness so low that they had advised against writing on the pipe with a Sharpie. In each and every example, CorrView International identifies the pipe wall in near new condition, and at virtually the same wall thickness as we had documented previously.
The facility provides us a copy of the one page spreadsheet style report by the mechanical contractor’s ultrasonic testing firm, which proves to be worthless. Reviewing it together with building engineers, we can find no correlation between the measurements written or marked on the pipe with the measurements reported for that location in their spreadsheet report. Our best guess is that their incorrectly taken wall thickness measurements were then randomly mixed together and incorrectly report for the various piping locations tested.
We explain to our client that they have in effect all erroneous wall thickness measurements which have been inaccurately recorded and mismatched to the wrong test locations to produce a completely worthless report.
The mechanical contractor is called to the facility and presented our findings, but maintains that the pipe is unsafe to weld. In anticipation to such a conflict, we have brought to the facility two different models (37DL and 38 DL) of Panametrics instruments, multiple probes, and different calibration blocks. The set-up and calibration of both instruments is very well demonstrated to the mechanical contractor and all site personnel involved. Testing is performed within the circles drawn on the pipe by either Sharpie or greased finger, where none of the low thickness measurements inscribed are found. We allow building engineers to scan the pipe themselves to see our results first-hand.
We demonstrate our procedure over and over at similar examples, and explain that there is not the slightest possibility that 24 in. steel pipe could even survive under its own weight at the 0.045 in. low thickness values identified in some areas by the contractor’s ultrasonic inspector. We are requested to double check all of the areas tested by the contractor’s ultrasonic inspector where we find none of his measurements accurate or even close.
We question the contractor to the equipment used by the other ultrasonic inspector and are told it is “highly advanced” but also determine that it has no visual waveform display and is a relatively small device. In reality it seems to be a low cost unit not capable of displaying the signal path through the material, nor verifying a wall thickness signal, nor capable of echo-to-echo measurement necessary for painted pipe, and not capable of data logging the thickness results. The type of probe used is unknown, but is not likely a higher frequency unit suited for such applications.
For areas of painted pipe, we can speculate that the ultrasonic instrument used by the mechanical contractor’s ultrasonic firm returned a false signal reflection at the boundary between the paint thickness and the steel pipe. Without a waveform display, and possibly lacking the experience to interpret such low thickness results due to this error, only the thickness of the paint was displayed. Since paint is softer, less dense, and transmits sound at a much slower velocity than steel, the movement of the ultrasonic signal back and forth through the paint would be inaccurately interpreted by the instrument as having traveled through a greater distance to produce the measurements reported.
Errors in wall thickness measurement performed at areas of bare steel cannot be explained, and are simply due to operator and/ instrument error.
Our inspection of the painted pipe uses echo-to-echo technology to negate the paint thickness entirely. As a final check and demonstration. we remove the paint in those lowest thickness areas circled and perform standard thickness testing, which identifies the same thickness values identified by echo-to-echo measurement.
The building engineers and facility management are finally convinced to the accuracy of our results and reassured that no threat exists for performing the threaded pipe encapsulation.
The work is performed within a few days of our inspection with no issues.
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