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…