The Benefit Of Prior Investigative Experience And A Trained Eye
A large worldwide financial institution plans the installation of two 4 in. wet taps into their active 24 in. condenser water header piping which serves their refrigeration machines and heat exchangers. As a standard precaution, they hire CorrView International, LLC to determine the wall thickness of the pipe in the areas planned for welding. CorrView has previously inspected this same facility going back 18 years, and has consistently identified low corrosion activity at their condenser water system to below 1 MPY.
Testing in both well defined areas takes under ½ hour to perform and produces excellent results as expected. We confirm high and uniform wall thickness still exceeding new standard pipe specifications of 0.375 in. since the pipe had been originally oversized when installed 22 years earlier. In combination with low corrosion activity, virtually unlimited service life remains in both areas of concern. Prior testing of the 24 in. mains had consistently identified high wall thickness. Our initial measurements of the piping system 18 years earlier had identified high wall thickness values to near 0.400 in. – to define that oversized standard grade pipe had been installed.
During our visit we notice that the facility is running approximately 4,000 tons of refrigeration while outdoor temperatures are near 8° F. Two large plate and frame heat exchangers are available but not in service. When we inquire why the heat exchangers are not in use on such a cold day we are informed they have never ever been used throughout the entire history of the facility.
A second look at the piping layout shows that the 12 in. distribution lines to and from the heat exchangers run an approximate 50 ft. distance across the mechanical room to the opposite wall. Supply and return lines to the heat exchangers are the 1st and 2nd take-offs to the flow of supply water from the cooling tower, and are bottom connections to the 24 in. main lines. Isolation valves are not installed at the mains, but at the heat exchangers approximately 50 ft. away.
Recognizing this piping arrangement as a common problem area and as a significant potential threat, we spot test areas of all four piping runs and quickly identify very severe pitting along the bottom and lower sides. Ultrasonic testing at the top of all four lines produces measurements at near 0.350 in. to 0.365 in., and very near new ASTM standard pipe specifications of 0.375 in. Alternately, inspection of the bottom of the pipe produces much lower wall thickness readings averaging near 0.125 in., with lowest thickness values to near 0.090 in. Low thickness values are marked onto the pipe itself should the facility have the interest to confirm our results.
Considering the possibility that there may be some error in the instrumentation, we recalibrate the probe, changes probes and recalibrate again, and then switch to another instrument where we produce the exact same readings. Low wall thickness is localized beginning at the bottom of the 90° elbow from the main to approximately 6 ft. outward from the elbow. Higher than normal corrosion activity is identified further out to the heat exchangers, but with wall thickness values still near 0.300 in., is of no consequence .
Our testing identifies the highest deterioration at the two supply side take-offs, with slightly higher but still unacceptable wall thickness at the return side piping. Three hours of further investigation is provided to the facility, and to a critical services long term client of ours at no charge.
The engineering staff is requested over to the site of our findings, where further testing and demonstration is performed in order to give them a first hand understanding of their conditions. We explain that the severe bottom pitting is likely due to over 20 years of rust and other airborne particulates settling in this area of pipe. Installing isolation valves far downstream at the heat exchangers, instead of immediately at the supply and return headers themselves as more appropriate, has created a large no flow settling zone. In addition, the installing the elbows from the mains at the bottom of the 24 in. header, instead of at the side wall or at top, guaranteed that any material traveling down the 24 in. line from the towers would fall down into the 12 in. outlet. Both are serious design errors in our view, but common ones seen at most larger data center and larger chiller plant operations.
The facility is a 24 /7 computer data storage site which is designed for uninterrupted service and which cannot be shut down. However, it is very clear that such low wall thickness to the bottom of the pipe, and a continued acceleration of that loss, will prematurely cause its shutdown, and at some unexpected moment.
The decision to shut down the facility is made, and requires almost 9 months to coordinate. A 6 hour window is provided to remove all 4 elbows and weld in their place 12 in. weldolets to isolation valves.
Once offline and drained, welders find they cannot burn or cut the pipe at the elbow. Two acetylene torches trained onto the same area of pipe fails to produce any result. A member of the mechanical firm climbs to the top of the pipe and turns a hole to reveal that the pipe is filled to approximately 70% of its depth with rust and mud. Obviously, almost 8 in. of thick wet mud and rust is absorbing the heat applied to the bottom of the pipe.
Attempts to shop vac the rust out from the top hole is unsuccessful since the material is packed rock solid into the pipe. A hammer drill is then employed to break up the blockage, after which it can be removed by vacuum. With the rust removed, the pipe can be cut away.
This unexpected problem causes panic to everyone given that an absolute maximum 6 hour window has been provided to complete operations on this and 3 other 12 in. lines and have the entire refrigeration system back up and running, and that the clock is ticking down. Additional teams of mechanics are rushed in from other Sunday projects to assist.
All four lines are found to be in similar condition. A later inspection of the removed pipe shows it extremely thin as had been reported by our investigation. New 12 in. valves are installed right at the headers themselves and the system returned to service within the 6 hour window allowed.
Facility management is so astounded at the event that they provide CorrView International, LLC a purchase order for a full week of on-site testing in order to inspect any other piping to our interest. They express that such a finding raises fears to other potential and unknown threats.
Our further efforts identify some significant threats at both the fire sprinkler and condenser water systems, which are addressed next by facility management thereby avoiding unnecessary failure.
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