Ultrasonic Pipe / Tank Testing



ULTRASONIC PIPE TESTING

Due to the combination of a wide variety of physical factors, building operations and management personnel are finding themselves faced with new and more complex corrosion related piping problems. Many are clearly related to the quality of the water treatment program or a past lack of corrosion protection, some are due to past problems which may have existed during construction and start-up.

In isolated cases, an engineering design deficiency may be at fault. Many, in fact, are directly related to the quality and origin of the steel pipe itself, and whether or not it is of foreign manufacture. Faulty construction and / or the substitution of sub-standard or thinner piping schedule may show up as an operating problem decades after installation.



The Advantages of Ultrasound

Identifying the current status of a piping system and the corrosion rate acting upon its metal surface is often difficult or impossible through other destructive and nondestructive means such as x-ray, corrosion coupons, spool pieces, selective pipe removal, or metallurgical testing, etc.

Ultrasound technology, however, allows the precise measurement of the pipe thickness from the outside surface; thereby providing the means to produce a thorough corrosion evaluation at reasonable cost. Ultrasonic testing differs from corrosion coupons, the most common form of corrosion monitoring, in that it summarizes the cumulative effects of all forms of corrosion over the lifetime of the pipe; providing a measurement of remaining wall thickness over a wide sampling of individual points.

The advantages of ultrasound testing are many, and include:

Proven Track Record As A Valuable Predictive Maintenance Tool
Results Based Upon Multiple Test Locations Rather Than A Few Isolated Areas
Identify Trends In Corrosion Rate Within Any Piping System
Improve Overall System Reliability And Extend Pipe Life
Highly Cost-Effective In Comparison To Cutting Out Samples
Equally Or More Accurate Than A Micrometer Measurement
Nondestructive, Non-Intrusive, Safe Procedure
No Shutdown Or Drainage Required
No Interference To Building Operations
Documents The Effectiveness Of The Water Treatment Program
A Useful Capitol Planning Tool For Future Repairs Or Replacement


Common Applications

HVAC piping systems for which ultrasonic testing is most frequently employed are:
Condenser Water Hot Water
Chill Water Steam Supply
Secondary Water Steam Condensate
Other Closed Systems    




Ultrasonic testing is suitable for determining the thickness of all materials, and is most commonly applied to:

Carbon Steel Cast Iron
Copper Brass
Galvanized Steel Ductile Iron
Wrought Iron Stainless Steel



Recommended Levels of Testing

Identifying the current status of any piping system requires a large number of sampling points upon which to base a final determination. This means evaluating multiple locations at the top, bottom and middle of the property, at horizontal and vertical sections, at large and small diameter sections, and at welded, threaded and grooved joint areas. As a general rule - the greater the number of wall thickness tests taken over the greater number of individual pipe locations equals the most reliable results.

This high number of required test points generally eliminates cutting out samples regularly spaced throughout a piping system for metallurgical analysis, and often leads to the dangerous practice of basing the evaluation of an entire system upon the results of just one or two piping sections.

It also eliminates taking a few random ultrasonic wall thickness measurements, printing them out on a standard spreadsheet, and calling it an evaluation. This is why each report produced by ECI is based upon a detailed investigation of 30, 50, 75 or more individual physical locations within one or more piping systems.

A total of 12 individual measurements are taken along the pipe circumference at each individual test location to provide a basis of several hundred wall thickness measurements for analysis. Data is offered in summary form as well as in fine detail, and provides valuable and reliable information on corrosion rate, actual pipe loss, percentage of allowable loss, remaining pipe life, and estimated retirement date.


Testing Accuracy

The basis of each evaluation is, of course, the measurement of the remaining pipe wall at the locations tested. Accuracy alone of the equipment we employ is approximately 1 mil or 0.001 in. for most applications.

Our use of on-site verification of each ultrasound measurement ensures the accuracy of each thickness reading, and eliminates the questionable practice often used by other testing services of discounting the highest and lowest readings within any set of measurements - in some cases discarding as many as 50% of the wall thickness readings taken. Existing thickness readings can then be compared to original pipe specifications and minimum acceptable wall thickness values to produce average and minimum based estimates of corrosion rate and remaining service life.


Reporting Criteria

Rather than produce retirement date calculations based upon some arbitrary percentage of the original pipe wall, a commonly employed practice having no basis in fact or theory, we refer to established engineering formulas for minimum acceptable wall thickness which take into account pipe size, service or application, construction, pressure, material strength efficiency, and other operating factors.

The result - a report conclusion that does not recommend premature or unnecessary pipe replacement, nor one that fails to recognize those operational factors which may lead to unexpected failure. Our remaining service estimates have been shown accurate at predicting pipe failures in many cases, and have saved the unnecessary replacement of pipe with decades of remaining life.

In some cases, a customer might only require an abbreviated report which basically shows all recorded wall thickness readings only. This option is available and will not include retirement dates, graphs and many of the operating conditions. This report option saves the customer approximately 40% of the highly detailed report. It is not usually recommended, but might be suffice for customer’s operating on a lean budget.


Field Testing

Testing can usually be accomplished during normal working hours. Steam and steam condensate piping, while it can be tested "live", is best performed during any available or scheduled downtime. Typically, it requires one day of on-site testing per 25 to 35 pipe locations, and approximately 4-7 days to analyze the data and prepare the final report.

Insulated piping requires the removal of small individual sections for access to the pipe surface. Severely corroded outer surfaces may require mild grinding to produce an acceptable base measurement platform. Paint can generally be accounted for by a special feature of our test instrumentation which negates the paint or coating from the overall wall thickness - thereby eliminating the need to wire brush and repaint any test areas. This is always a savings to building maintenance.


Pipe Testing Report Samples

A selection of reprinted pages from a typical client report can be viewed below in order to illustrate the level of detail provided for each pipe location tested. Although such high detail is requested by many of our clients, summary information in the form of written text and graphics is also provided in each report.

Each report offers both an executive summary as well as a detailed discussion of our findings. Written recommendations and corrective measures are also made addressing any piping deficiencies identified in the report. A photograph of each pipe location showing the actual test area is incorporated into each detail page of the report in order to better identify the test site to the reader, and to aid follow-up testing or future investigators.

Since a high level of detail is provided in each ECI ultrasound report, and because we do not always have the opportunity to present our findings personally, we provide the written explanation and background information necessary to understand its content as best possible. A typical 50 point report will cover between 100 and 125 pages, and is written and arranged in an easy to read and understand format. Our pipe testing report has been termed by many within the building management industry as, "An invaluable piping and corrosion reference book." A full appendix of relevant wall thickness data and other valuable information is also provided.

Each report is preceded with a thorough explanation of the testing procedure, equipment used, basic theory of ultrasonic measurement, and necessary assumptions related to our testing and reporting procedure. Due to the fact that our pipe testing reports are often submitted past a wide range of individuals including building owners, operating engineers, consulting engineers, and lawyers, among others, we have always strived to provide information ranging from the most basic conclusions to the most detailed technical information.


Clear Presentation of Results





Graphical Analysis

Graphed summaries are particularly useful for identifying various trends which may exist, and for comparing and evaluating the cumulative data derived from all test locations.





Specialty Product – Corrosion Monitoring

The CorrView ® corrosion monitor is a new product specifically designed for monitoring corrosion activity and wall loss under the real world conditions - meaning that it measures corrosion activity within the actual piping system – not in an isolated side stream loop. Simply stated, CorrView ® acts as a virtual "Pipe Fuse" by providing a bright visual warning indication after a predetermined amount of wall loss has been exceeded. Its unique design offers building and plant owners and operators a valuable new method to safeguard their piping and related equipment from the damaging effects of corrosion.

Its simple, maintenance free design allows installation virtually anywhere - thereby extending corrosion monitoring coverage and greatly improving system reliability. It is ideally suited for condenser water, process water, chilled water and fire sprinkler applications.

To find out more, click here, www.corrview.com



Ultrasonic Tank Testing


Similar to our pipe testing program, nondestructive ultrasonic analysis offers an extremely cost-effective method of fully evaluating any tank or pressure vessel without the expense and downtime of cutting out wall samples for metallurgical analysis.


The Advantages of Ultrasound

Identifying the current status of a tank, pressure vessel, expansion tank, heat exchanger, cooling tower pan or other storage vessel, and the corrosion rate acting upon its metal surface, is often difficult or impossible through other destructive and nondestructive means such as x-ray, selective sample removal, or metallurgical testing, etc.

Ultrasound technology, however, allows the precise measurement of the metal's thickness from the outside surface; thereby providing the means to produce a thorough corrosion evaluation at reasonable cost. Unlike for open or closed circulating systems, corrosion coupons are not a valid option for tank corrosion monitoring. In many cases, a leak or failure at the associated piping to or from a tank or pressure vessel is the first indication that a corrosion problem might exist.

The advantages of ultrasound testing are many, and include:

Proven Track Record As A Valuable Predictive Maintenance Tool
Results Based Upon Hundreds Or Thousands Of Measurements
Identify Trends In Corrosion Rate Within Any Tank Or Vessel
Improve Overall System Reliability And Extend Tank Life
Highly Cost-Effective In Comparison To Cutting Out Samples
Equally Or More Accurate Than A Micrometer Measurement
Nondestructive, Non-Intrusive, Safe Procedure
No Shutdown Or Drainage Required
No Interference To Building Operation
Documents The Effectiveness Of The Water Treatment Program
A Useful Capitol Planning Tool For Future Repairs Or Replacement



Common Applications

Commercial facility equipment for which ultrasonic testing is most frequently employed are:

Domestic Water House Tanks Heat Exchangers
Make-Up Water Tanks Steam Supply Headers
Cold & Hot Water Storage Tanks Steam Condensate Tanks
Chill, Hot, & Secondary Water Expansion Tanks Flash Steam Tanks
Cooling Tower Pans    



Recommended Levels of Testing

Identifying the current status of any tank or pressure vessel generally requires a large number of sampling points upon which to base a final determination. This is primarily due to their size, and the different surfaces often having varying thickness values and minimum thickness limits. In addition, most tanks have varying physical parameters - with round tanks usually having a different shell and head thickness, and square or rectangular tanks having different wall and bottom dimensions.

Since most tanks or vessels maintain a water line, it is extremely important to provide sufficient measurements to determine if any deterioration in that area exists, and to what degree. Under deposit corrosion at the bottom of the tank is also a serious concern due potential sediment and deposits, although this area is often difficult to physically access. In addition, cold water tanks have the added threat of developing outer surface corrosion due to moisture condensation - in some cases becoming the limiting factor in future service life.

This high number of required test points generally eliminates cutting out samples regularly spaced along the wall for metallurgical analysis, which often leads to the dangerous practice of basing the evaluation of an entire system upon the results of just one or two individual samples.

It also eliminates taking a few dozen random ultrasonic wall thickness measurements, printing them out on a standard spreadsheet, and calling it an evaluation. This is why each report produced by ECI is based upon a detailed investigation of several hundred or more individual measurements per tank.


Testing Accuracy

The basis of each evaluation is, of course, the measurement of the remaining tank wall at the locations tested. The accuracy alone of the Panametrics equipment we employ is approximately 1 mil or 0.001 in. for most applications.

Our use of on-site verification of each ultrasound measurement ensures the accuracy of each thickness reading, and eliminates the questionable practice often used by other testing services of discounting the highest and lowest readings within any set of measurements - in some cases discarding a significant percentage of thickness readings taken. Existing thickness readings can then be compared to original wall thickness specifications and minimum acceptable wall thickness values to produce average and minimum based estimates of corrosion rate and remaining service life.


Reporting Criteria

Data is offered in summary form as well as in fine detail, and provides valuable and reliable information on corrosion rate, actual wall loss, percentage of allowable loss, remaining tank life, and estimated retirement date.

Rather than produce retirement date calculations based upon some arbitrary percentage of the original wall thickness dimensions, a commonly employed practice having no basis in fact or theory, we refer to established engineering formulas for minimum acceptable wall thickness which take into account overall shape, size, diameter, head shape, base supports, ASME or API code, operating pressure, construction, material strength, thickness schedule, service provided, and other relevant physical parameters.

The result - a report conclusion that does not recommend premature or unnecessary tank replacement, nor one that fails to recognize specific attributes of the tank or pressure vessel, or fails to include those operational factors which may lead to unexpected failure.

In some cases, a customer might only require an abbreviated report which basically shows all recorded wall thickness readings only. This option is available and will not include retirement dates, graphs and many of the operating conditions. This report option saves the customer approximately 40% of the highly detailed report. It is not usually recommended, but might be suffice for customer’s operating on a lean budget.


Field Testing

Testing can usually be accomplished during normal working hours. Steam and steam condensate tanks and vessels, while they can be tested "live", is best performed during any available or scheduled downtime. Typically, it requires one day of on-site testing per large house tank, cooling tower pan, or steam condensate vessel and one half day to test smaller equipment. We require approximately 4-7 days to analyze the data and prepare the final report.

Insulated tanks and vessels require the removal of such material, preferably throughout the entire unit. In some cases where management does not wish to remove and replace all the insulation, we can suggest cutting strips of insulation along the side of the tank to access specific locations only. Severely corroded outer surfaces may require mild grinding to produce an acceptable base measurement platform. Paint can generally be accounted for by a special feature of our test instrumentation which negates the paint or coating from the overall wall thickness - thereby eliminating the need to wire brush and repaint any test areas. This is always a savings to building maintenance. However, many "tar or mastic" like coatings often found at cold water house tanks must first be removed. Similarly, multiple layers of paint or coatings which have not held their adhesion, and offer microscopic separations and air gaps, must also be removed.


Tank Testing Report Samples

A selection of reprinted pages from a typical client report can viewed below, and is provided in order to illustrate the level of detail provided for each tank location tested. Although such detail is requested by many clients, summary information in the form of written text and a graphical format is also provided in each report. Related piping problems and visually observed defects are documented with a photograph and commented upon.

Each report offers both an executive summary as well as a detailed discussion of our findings. Written recommendations and corrective measures are also made addressing any deficiencies identified in the report. A photograph of each tank location showing the actual test area is incorporated into each detail page of the report in order to better identify the test site to the reader, and to aid follow-up testing or future investigators.

Since a high level of detail is provided in each ECI ultrasound report, and because we do not always have the opportunity to present our findings personally, we provide the written explanation and background information necessary to understand its content as best possible. All reports are written and arranged in an easy to read and understand format.

Each report is preceded with a thorough explanation of the testing procedure, equipment used, basic theory of ultrasonic measurement, and necessary assumptions related to our testing and reporting procedure. Due to the fact that our tank testing reports are often submitted past a wide range of individuals including building owners, operating engineers, consulting engineers, and lawyers, among others, we have always strived to provide information ranging from the most basic conclusions to the most detailed technical information.


Clear Presentation of Results








Limitations of Ultrasound Pipe and Tank Testing

We believe our reports provide the best available evaluation of the condition of any piping/tank system within its intended scope - which is to provide an initial general evaluation. Yet, there are clearly limitations to ultrasound technology which must be recognized.

First is the inability to take wall thickness measurements covering every square inch of every pipe/tank. Due to this physical limitation, in fact a virtual impossibility for any form of contact testing, we can never conclusively state the condition of every part of a system based upon the results from the locations tested in our report alone.

While hundreds or even thousands of thickness measurements represent a significant number of test points over this limited number of pipe/tank locations, we could, in fact, take all such measurements entirely within a less than ten square inch area of pipe/tank. Other factors such as welds, expansion joints, hanging stresses, dezincification, sweated joints, and pipe seams and material defects, etc. may contribute to a future leak or failure, and are not within the scope of our evaluation.

A second limitation is in the focusing range or sensitivity of our equipment. We can measure wall thickness with great accuracy and identify general areas of pitting. However, because the travel of the ultrasound wave through the pipe/tank wall has a focusing width of approximately 1/16th of an inch, we are unable to locate pipe/tank flaws of lesser dimension. Manufacturing inclusions and defects, weld and seam cracks etc. and micro fine pipe splits and pinholes cannot be reliably located using the A-Scan instrumentation we employ due to the perpendicular orientation of the defect to the direction of the ultrasonic sound wave. Such pipe flaw detection and analysis is possible, however, using far more advanced B-Scan technology or X-Ray, which are suited only to finely investigate localized areas and thereby not appropriate for a general building piping survey.

A third limitation (or benefit, for the purpose of a wall thickness study) is the inability to locate pipe/tank sections having a buildup of rust, iron oxide, biological material, or other debris on the interior of the pipe/tank wall. A key feature of our Panametrics 36DL Plus instrumentation is its ability to clearly distinguish between metals of a different acoustical density. Ultrasound waves will travel within one material of a specific density until they reach a boundary layer having a different acoustical characteristic - this may be water, gas, air, rust, dirt, or biological material. Ultrasound waves are then reflected back from the boundary layer along the same basic path to provide a round trip time interval upon which actual wall thickness is determined.

Ultimately, the reliability of this or any ultrasonic evaluation is based upon numbers - many numbers. Simply stated, the greater the number of wall thickness readings taken at a given point location, the greater probability that the final conclusions drawn accurately reflect true wall thickness and corrosion conditions within the pipe/tank under evaluation. Similarly, the greater the individual number of locations tested within a particular piping/tank service increases the probability that the corrosion rate and retirement date determined for those sections exists throughout the remainder of that system.


To learn more, click here or call 732-548-4311 for more information.