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Shorter Pipe Service Life

A common and unavoidable observation for anyone involved in the piping industry over the past few decades has been to the unfortunate but steady decline in the quality of American made steel pipe.  In the 1980’s, reference was made to the higher quality of 1960’s products.  Older piping steam fitters would then challenge that statement by referencing pre WW II era pipe as being far superior.  Only ten years ago, 1990’s produced pipe was looked at as superior.

Today, anything produced 10 or more years ago is viewed as offering far greater quality and higher corrosion resistance.  And the scale continues its decline.

• Subjective vs. Hard Documentation

Although such quality assessments are clearly subjective and often based upon anecdotal memory and hearsay, CorrView International, LLC has accumulated a large volume of hard data to accurately substantiate the decline of American piping products.  With over 20 years in the field of ultrasonic pipe testing at building properties throughout the United States, we have amassed volumes of hard and irrefutable documentation showing a far greater corrosion induced impact to steel pipe products in recent years.

In fact we see many much older buildings still in service with their original pipe; buildings in most larger cities dating back to the 1920’s, for example.  Ultrasonic investigations of such properties routinely identify still excellent results for piping which is 70 years old or more.  Below we show various examples of older pipe serving continuously for as long as 111 years, and still capable of providing another 200+ years of service or more.  In such examples, ultrasonic measurement results have been fully supported by visual examination.  The remainder of this Internet site documents generally more recent piping systems, and their associated corrosion problems.

Older Pipe Examples

1928 – Fire sprinkler 6 in. main supply line showing minor cosmetic corrosion and with its wall thickness still at new ASTM schedule 40 specifications.	1964 – Chill water service 12 in. pump supply line.  A light coating of oxidation exists with high and uniform wall thickness still near new schedule 40 specifications.

1921 – Saved coupon cut-out from 8 in. fire sprinkler main showing some minor internal deposits but with extremely high and uniform wall thickness still near new schedule 40 specifications.	1901 – Steam condensate horizontal 4 in. main – likely the worst possible conditions for a steam system.  Only minor bottom pitting is present after 111 years of seasonal steam heating service.

While many factors exist to negatively impact modern day piping products that were not issued back 70 years ago, it is also fair to say that many technological improvements should have lengthened pipe service life.  Better chemical treatment controls and more intensive monitoring should have reduced corrosion rates.  Biocides were not used at cooling systems operating in the 1950’s.  Where no chemical corrosion inhibitors would have been used in an early closed hot water heating system from 1910, very effective inhibitors are now available.  Water filtration is now standard where unheard of decades ago.  Water treatment consultants now aggressively monitor piping systems and the effectiveness of the chemical treatment programs.

The effectiveness of chemical inhibitors have greatly varied from high effective sodium chromate used up to around the year 1986, and less effective phosphonates common today.  Unquestionably, a wide variance in conditions exist to explain or suggest differences in pipe service life.

In fact there are four main issues which explain both the perception and physical reality of today’s pipe not reaching their service life expectations:

• Corrosion Coupon Inaccuracy

Over 20 years of ultrasonic investigations have proven the inaccuracy of corrosion coupons; with overwhelming evidence of such provided within this website.  Yet, they remain the standard by which pipe corrosion is measured and will remain so.  In decades past where corrosion activity was commonly to 1 MPY or below for a condenser water system, low corrosion coupon results would provide a closely accurate result.

Today, however, corrosion rates may range to 10 MPY and as high as 50 MPY for a cooling tower system and still produce low 0.5 MPY corrosion rate results measured by corrosion coupons.  Water treatment consultants utilize the very same test method – thereby only confirming an inherently inaccurate result.  Such results are looked upon favorably by chemical treatment suppliers and surprisingly even building owners; often believed even where failure or evidence of high rust deposits suggest otherwise.  View an actual Case History investigation where a total reliance on corrosion coupons ultimately resulted in the failure and replacement of the entire condenser water piping system.

• Physically Undersized Pipe

Pipe is defined according to schedule by ASTM, the American Society for Testing and Materials.  Each pipe schedule has a published wall thickness depending upon its pipe size – Schedule 40, A53 carbon steel 12 in. pipe at 0.406 in. for example.  ASTM provides a manufacturing tolerance of + or -12.5% for steel pipe, however, which means that the pipe can be provided at between 0.355 in. and 0.457 in., a 25% range, and still be considered acceptable for service.

Twenty or more years ago, most pipe manufactured had a wall thickness which was at or above its ASTM defined dimension to provide a benefit for any property where wall thickness was higher than necessary.  This is why any investigation of older properties from the 1950’s will still often show high wall thickness at and even above new ASTM specifications – the combination of oversized pipe and low corrosion activity.  In an investigation of a New York City Rockefeller Center property built in 1959, testing of the 24 in. condenser water pipe identified wall thickness consistently near its original extra strong specification of 0.500 in. after more than 53 years in service.

Today, however, that trend has changed to show most pipe manufactured at below to substantially below its ASTM defined wall thickness.  Few examples of new pipe ready for installation have produced thickness measurements at or above ASTM specifications, and in fact, most pipe we find at construction sites today is nowhere near their expected wall thickness.  The high incidence of undersized pipe suggests against it being a random event.

Undersized pipe has varying impact based upon piping system involved, pipe schedule, and pipe size.  Smaller diameter pipe, commonly threaded, is most heavily impacted, and will produce a very noticeable loss in service life where only 0.065 in. of available wall thickness may exist under the best conditions.  Fire protection systems, due to their use of thin wall schedule 10 and schedule 7 pipe, can have their service greatly reduced by a 12.5% reduction in wall thickness.  Larger welded pipe is less affected, although at a moderate corrosion rate of 2 MPY, new 12 in. schedule 40 pipe undersized to 0.050 in. represents a theoretical loss of 25 years of service life.

• Higher Corrosion Susceptibility

Again, this is a subjective perception by many experts within this field but one also proven by CorrView International, LLC after two decades and hundreds of ultrasonic investigations spanning buildings from 1 year old to the year 1898.

Investigations of older building properties where pipe was installed at different times will always show lower corrosion activity at the older pipe.  Visual evidence alone of older piping systems, exposed to the elements without any form of coating protection, attests to the natural corrosion resistance of older piping materials.  Wrought iron pipe, commonly found at older buildings constructed prior to 1970, had a form of internal grain structure which inherently opposed corrosive attack and pitting.  The elimination of ASTM A72 wrought iron pipe from service in 1965 is clearly one major factor in explaining the higher corrosion found at more modern building properties.

While visual and ultrasonic evidence exists that there are differences between new and older carbon steel pipe products, we have seen no formal explanation to this observation, nor any interest in the issue.

• Foreign Pipe Products

Not intended as a nationalist statement, but we have generally found foreign produced pipe product to be of lower quality, having a greater incidence of physical defects, and exhibiting greater vulnerability to corrosion.  Galvanized pipe has been shown to flake off the galvanizing when being rolled with an end groove.  Foreign made galvanized pipe has been documented to fail within two years and less.  A surprising volume of foreign pipe, commonly ERW grade or having a welded longitudinal seam, arrives with the seam obviously incomplete – a clear sign of poor quality control.  Most pipe is again undersized similar to American pipe products.

Susceptibility to corrosion is unquestionably higher for foreign pipe, although when metallurgically tested, will be typically found to meet ASTM chemical and physical property specifications.  In piping systems where foreign pipe products have been installed from varying sources, we have actually graphed our results to show different corrosion rates for each country’s product, even within the same piping system.  One contradiction to this statement is again the more rare examples of older foreign pipe such as German products made in the 1930’s, where ultrasonic testing has still shown it to be in near new condition.

The explanation for such difference is a metallurgical one which has not been investigated to our knowledge.  Although many building specifications today call for domestic produced pipe only, a surprising volume of foreign pipe is still installed – not identified as such until a failure occurs and investigation is initiated.  As the difference in corrosion susceptibility shrinks between American and foreign pipe products, however, this issue becomes of less importance.

• Caution Necessary

As even a brief review through this Internet site overwhelmingly illustrates, corrosion within the HVAC and plumbing industry is widespread and potentially catastrophic to many building properties.  For some, a lack of proper maintenance and / or chemical treatment control is the obvious fault.  Engineering design oversights and the failure to consider water flow velocity and particulate settlement is another cause.

But for others, one or more hidden contributors, rarely investigated or even considered, will impact its operation within a few years to even months after entering service.

While obviously difficult to assay and physically test each pipe delivery to determine its suitability for service, certain basic observations to piping stamp, country of origin, wall thickness, physical condition, and a review of its conformity to the mechanical design specifications can avoid future problems.

© Copyright 2023 – William P. Duncan, CorrView International, LLC