PD-12:   Pipe Substitution Introducing The “Weakest Link” Scenario Of A Chain Into A Piping System The finding of substantially thinner pipe intermixed with heavier pipe of the correctly specified ASTM wall thickness is not uncommon.  The typical scenario is for an ultrasonic testing investigation to show generally uniform results when suddenly pipe wall thickness plummets to suggest a major corrosion threat. A worse event is to discover the issue following an unexpected piping failure. In reality, however, it is not some localized severe form of corrosion activity, but the substitution of schedule 40 pipe for schedule 80 in a high pressure steam service line, schedule 10 or schedule 20 substitution for a schedule 40 condenser water line, or schedule 7 substitution for schedule 10 in a fire sprinkler system.  Ultrasonically measuring dramatically different but uniform wall thickness at each side of the weld joint between adjacent sections of pipe is irrefutable proof that pipe substitution has occurred. A Side By Side Example In the photograph at left, an ultrasonic piping investigation into a high corrosion condition unexpectedly revealed multiple examples…

PD-11:   Pipe Specifications Comparison Of Various Schedules And Wall Thickness Values For Carbon Steel Pipe The following tables offer a good visualization of the differences which exist for various common size carbon steel pipe at different ASTM thickness schedules.  The dimensions of the blue thickness bars are technically to scale, although they may display and print out differently depending upon your specific computer and monitor resolution. The tables are meant to serve as a general guide in illustrating the different relevant thicknesses between different pipe schedules, and their importance to reliable system operation – not as an absolute dimensional template. This table of wall thickness dimensions clearly illustrates the significant difference which exists between standard and extra strong pipe.  A much greater difference exists at the larger diameter piping, although the additional pipe wall is usually most needed at the smaller and typically threaded pipe sizes. For 10 in. and under, schedule 40 is equal to standard pipe, and schedule 80 is equal to extra heavy – although for larger sizes, the thickness of schedule 80 defined pipe will increase significantly.

PD-10:   Galvanized Steel For Hot Water Service An Inherent Chemical / Physical Limitation Of Galvanized Steel Pipe, And Why It Should Never Be Used In Any Hot Water Service Galvanized steel is commonly used for many building related piping systems including domestic cold water, sanitary waste, compressed air, storm drain, vent, and fire protection.  Its zinc protective coating has far greater resistance to corrosion than steel and essentially serves as a sacrificial anode to cathodically protect the underlying steel surface as long as the zinc remains.  Once the zinc protective coating fails, a more intense and focused deterioration of that affected area typically occurs. In its earliest stage of failure, zinc deterioration may impact one or a few areas and penetrate through with the aggressiveness of a drill bit.  Where localized penetration is less severe and the corrosion process continues over a more widespread surface area, substantial rust product is produced as a result of a corrosion process which oxidizes the steel to approximately 12 times greater volume of less dense iron oxide. Although not recommended, and with copper now the preferred…

PD-09:   Undersized Steel Pipe A Simple Dial Caliper Wall Thickness Measurement May Reveal Surprising Results The first use of steel pipe to carry liquids or gas can be traced back to 1815 when an inventor joined together discarded American Revolution musket barrels to transport coal gas throughout London to fuel home lanterns and stoves.  Soon after, in 1825, inventor Cornelius Whitehouse designed a process whereby flat steel plate was bent and formed into a rounded shape and “butt-welded” along its longitudinal seam – a process continued relatively unchanged to this day.  The first true manufacturing plant for steel pipe opened in Philadelphia, PA in 1832. Historically, the earliest non-metal pipe used for water transport was bamboo, dating back to 2,000 B.C.  Greater strength and flow volume demand eventually led to the use of hollowed out tree logs, which were used to construct Boston’s public water supply system in 1652.  Still to this day, examples of wooden pipe are unearthed at older American cities such as New York City and Boston.  While most are out of service, some surprisingly still remain active.

PD-08:   Moving In The Wrong Direction Changes In Piping Trends Which Have Occurred Over The Past Few Decades Over the past 30+ years, CorrView International, LLC has performed numerous ultrasonic investigations of either very old pipe installed in the early 1900’s, or at properties where a combination of old and new pipe exist.  That work offers a remarkable demonstration of how government restrictions and excessive environmental regulations have reduced the quality and corrosion resistance of today’s steel piping products. Combined with less tolerant engineering practices, thinner pipe materials, cost cutting, less effective corrosion inhibitors, as well as other factors, most new piping installations can be expected to provide significantly less service life than those built many decades earlier. Higher Quality Of Older Pipe First and foremost is the unquestionable superiority in quality and corrosion resistance of pre World War II pipe to that manufactured today – whether foreign or domestic.  Our ultrasonic testing of steam systems from 1911 have shown a minimal loss of only perhaps 20% from the original wall thickness.  Testing of some galvanized steel domestic water risers…

PD-07:   Heat Exchangers The Ultimate Safeguard For Critical Or Problem Condenser Water Applications Excessive corrosion activity can devastate a condenser water system or open process piping in as little as a few years.  Generally co-dependent upon pipe size, a corrosion rate of 25 mils per year (MPY) can deteriorate ASTM A 53 standard 12 in. piping to its minimum safe limit in only 10 years, and its 1-1/2 in. threaded distributions lines in as little as 2 years or less. High corrosion rates exceeding 8 MPY are typically due to under deposit or cell corrosion, microbiologically influenced corrosion (MIC), and various advanced forms other than general corrosion.  Often, such advanced corrosion activity can develop even though no obvious physical signs suggest a problem, and where years of corrosion coupon monitoring show low corrosion rates. Difficult To Control Once Established Unfortunately, all aggressive forms of corrosion are difficult, if not impossible, to control and correct using standard procedures once the problem has been firmly established.  Most advanced corrosion mechanisms produce wild variations of pitting or depth penetration into the pipe, extensive…

PD-05:   Higher Corrosion Activity 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, and to the use of thinner piping schedules, lower grade of materials, worse pipe manufacturing quality, and different joining methods. Other changes have been in the mechanical piping layout design itself, with the interest in reduced cost a primary factor. A Negative Evolution For HVAC systems, and specifically for condenser or process water systems, changes in materials alone have had a significant impact. Issues such as foreign pipe products, ERW welded pipe, undersized wall thickness to minimum ASTM limits, greater corrosion vulnerability, less effective chemical corrosion inhibitor protection, and overall lower pipe quality across the board.  All such factors have resulted in modern piping systems where corrosion loss in just a few years can exceed the total wall loss of an equivalent 70 year old piping system. A recent…

PD-04:   Clamped/Grooved Type Pipe Construction Making Sure Your Pipe Service Life Is Not Cut In Half During Construction Clamped/grooved type piping construction is today employed in a variety of applications, and growing in use.  Once seen primarily at fire sprinkler service and temporary applications, grooved clamped construction is now commonly found in condenser water piping from large 24 in. diameter main risers to smaller 2 in. distribution lines.  Grooved pipe is installed at chill and secondary water systems, as well as for domestic water applications.  In the many examples we have seen, we have documented grooved clamped pipe to provide excellent service over many decades. Similar for any piping system, the ultimate service life is often determined by its design, operating conditions, chemical treatment protection, pipe schedule, materials used, and quality of construction.  Long service life is typically available by following established maintenance guidelines, along with certain preventative measures – such as water filtration and close attention to the chemical water treatment.  Grooved clamped pipe will often provide service reliability equal to welded pipe, but in those examples where a moderate to…

PD-03:   Severe Chill Water Pipe Corrosion Why A Very Heavy Payback Now Exists For The Earliest “Free Cooling” Systems Operating refrigeration equipment is a major budget expenditure for any building property.  In winter climates especially, running large and expensive refrigeration chillers when the outdoor temperature is likely colder than the chill water produced seems a major contradiction in logic. Back in the 1970’s, the solution was to directly connect the cold condenser water into the chill water piping system – thereby eliminating the use of the centralized refrigeration chillers under certain temperature and humidity conditions.  At the time, the only concern for this modification was the introduction of captured airborne particulates into the chill water system and the potential for fouling.  This issue was presumably resolved by adding a full flow water filter at the cross connection line between the condenser water and chill water piping – in reality, a superbly inadequate solution now showing up 30-40 years later in the form of major chill water pipe corrosion. Virtually all such “free cooling” units were retrofit modifications to the existing refrigeration plant;…

PD-02:   Galvanized Pipe Failure How A Simple Engineering Design Error from 100 Years Ago Is Now Requiring Widespread Pipe Replacement All piping systems have an inherent lifespan which may or may not be influenced by certain actions by the building property owners and engineers.  For HVAC systems and specifically for condenser or cooling tower water supplied to the refrigeration chillers, chemical inhibitors can be maintained to reduce corrosion activity to tolerable levels.  Boilers, steam systems, and hot water heating systems are also chemically protected.  For fire protection systems, chemical control is available but generally not provided, with the deterioration of the system wholly dependent upon pipe quality, thickness, the frequency of testing required and the volume of new fresh water introduced. For plumbing systems, material selection becomes the critical issue since no chemical corrosion inhibitor can be introduced to potable drinking water.  Sanitary waste lines are typically constructed using extra heavy cast iron or ductile iron pipe offering a lifespan of between 75 and 100 years.  Supply piping for domestic cold water and hot water systems are today typically constructed using copper…