Photo Gallery B4:  Under Deposit Corrosion Under deposit corrosion, often termed “cell corrosion,” is an aggressive pitting condition commonly associated with an internal settlement and buildup of rust deposits within a piping system.  It can be initiated by rust migration and settlement from other areas of the system, and is also related to the production of heavy rust tuberculation on the pipe’s surface.  Over time and through the progression of various chemical transformation, very localized and severe wall loss takes place. As we have repeatedly stated to our clients – it is not the rate of corrosion in MPY which defines the remaining service life of a piping system, but the volume of rust created and its deposition in dead-end and low-flow areas which dramatically accelerates localized pitting activity.  Even a moderate to high 5 MPY corrosion rate at a condenser water system will still provide extended service life in terms of the pipe wall lost, with such loss at standard 0.375 in. pipe still providing 70 years of service before reaching failure status.  Yet, oxidizing that volume of steel into potentially 50 cubic feet or more of rust product may destroy specific areas…

Photo Gallery B3:  Corrosion Under Insulation CUI, otherwise known in the trade as “Corrosion Under Insulation,” represents one of the most damaging forms of corrosion to any piping system operating under cold temperatures – such as chill water, dual temperature, and domestic cold water.  It develops slowly over decades hidden from view, with few building owners or operators actively seeking to identify its presence.  It can also develop under insulated pipe exposed to outdoor weathering, although that is technically a different condition. The impact from CUI is directly related to pipe temperature, area humidity, the type and thickness of its insulation, and an effective moisture barrier.  Supply pipe at typically 10° F lower temperature always suffers the worst.  Contrary to claims by the insulation industry, fiberglass insulation provides a very poor barrier to moisture by its paper foil covering.  Proof positive to this fact is provide in just some of the examples we have documented in this gallery.  Although the level of deterioration to the pipe does not equal the thickness of rust product, it can often well exceed internal corrosion levels.  And unlike internal corrosion which is typically uniform for most cold water…

Photo Gallery A6:  Pressed Copper Failures Copper pipe generally provides trouble free service – almost.  Although not immune to corrosion and actually more vulnerable to specific issues such as velocity induced erosion and cavitation, copper pipe is being turned to more and more as evidence of lower service life for steel pipe appears.  In cases where wall thickness has been high yet failures have occurred at elbows, metallurgical lab testing has commonly identified erosion caused by the almost insignificant failure to camfer or bevel the inside diameter of each connection.  As a result of this very minor installation defect not well recognized, turbulence and cavitation at the downstream side of the connection can produce severe pitting resulting in its failure. For much older properties, “TP” or threadless copper pipe was typically brazed in place.  Virtually indestructible, it has been documented to show almost no wall loss after 85 years of service.  Soldered standard Type C copper then took over as the standard – only to be substantially replaced in its construction through the elimination of soldering. For pressed copper pipe assembly systems, however, in which each fitting is swaged or squeezed onto the copper pipe with…

Photo Gallery A7:  Unconventional Pipe Repairs While in the ideal world a pipe leak or failure would be addressed by immediately taking the system off-line and replacing the pipe, such cannot always be done for an assortment of reasons.  Emergency pipe clamps are also not always available, may not be of the correct size, or may not fit.  Where failures occur at anything other than at a smooth straight length of pipe, such as at the threads, a clamped joint, tee, elbow, valve, or some other fitting, emergency repair clamps simply cannot be used; requiring the system to be shut down if the failure is large enough.  Yet for many, a quickly sharpened pencil or cut-off broom handle have saved the day. For small leaks, further options may suffice – such as the use of a slice of rubber gasket material held on by a hose clamp – unquestionably the most common repair we encounter.  Final repairs may then be carried out as soon as possible, or the issue forgotten.  A slow drip at a  thread may take days to fill up a 5 gallon bucket; emptied every week.  A larger leak may result in that…

Photo Gallery I4:  Plate & Frame Heat Exchangers Plate and frame type heat exchangers play a critical role in separating one piping system from another or by isolating the transfer of heating or cooling.  They are critically important for isolating critical HVAC equipment, such as heat pumps with their extended network of smaller diameter piping, and prevent the more aggressive corrosion activity inherent for open condenser water service.  Heat pump systems constructed without heat exchangers, running open condenser water through their elaborate network of small diameter threaded schedule 40 steel pipe, have produced some of the worst results identified in our UT investigations; requiring major pipe replacement in under 10 years. Early attempts back in the 70s at “free cooling” by directly cross connecting the condenser water system into the chill water system during colder months ultimately proved to not be really “free” at all.  The modification included the installation of a large strainer type water filter installed to clean the condenser water before it was injected into the chill water system.  Capable of removing only larger particulates exceeding 110 micron, such strainers let through the majority of debris, which for an open system falls in the range of about…

Photo Gallery I3:  Refrigeration Chillers Most refrigeration machines see an annual cleaning and inspection of their condenser water tubes, at which time it offers an excellent report card evaluation as to the corrosion control provided.  Accumulations of rust and chipscale within the waterbox is a clear indication to a higher than normal corrosion condition.  Other indicators are a rusted and pitted tubesheet, waterbox, and heads.  A white coating at the tubes strongly indicates a high scaling condition whereby cycles a concentration have been maintained at higher than acceptable levels.  Any difficulty in cleaning the tubes with an appropriately sized brush is further proof to a high scaling condition. A large volume of plugged tubes is a clear indication to a long-term corrosion condition as well as the lack of interest to correct the problem. The evaporator or chill water side of a refrigeration machine traditionally experiences far less corrosion activity and is therefore of lesser concern.  Rather than annual cleaning and inspection, most evaporator sections are cleaned and inspected every 3 to 5 years.  …

Photo Gallery I6:  Proper Dielectric Fitting Installation This photo gallery illustrates the correct installation of a dielectric fitting and its purpose to eliminate the electrical conductivity between steel or galvanized steel and copper or brass.  We generally find the need for dielectrics unnecessary where corrosion activity is very low, as should exist for most closed piping systems maintaining corrosion activity at below 0.5 MPY.  Decades ago, open condenser water systems rarely had any insulation between dissimilar metals yet experienced no measurable corrosion increase.  This we have always attributed to the superior quality and inherent corrosion resistance of older pipe in combination with more effective corrosion control chemicals of that time.  Even where brass met galvanized steel, problems were rare. Today, conditions are quite the opposite.  Direct galvanized steel to copper or brass connections are an almost certain guarantee of a galvanic induced failure.  Failures of new galvanized steel pipe threaded up to a brass valve have occurred in under 8 years.  Likewise, any open condenser water system lacking dielectrics is almost guaranteed to see their first thread failures at those areas.  The specification for dielectric fittings are a near necessity for open condenser water systems – yet are also specified…

Photo Gallery I7:  Improper Dielectric Fitting Installation A remarkably common finding in our ultrasonic investigations relates to the incorrect installation of galvanic fittings or isolators, also known as “dielectrics.”   Although such fittings were virtually unheard of within the HVAC industry 40 years ago , the much higher levels of corrosion activity occurring today demand control of this added corrosion threat.  For that reason, dielectric fittings are often one of the first steps taken in response to a corrosion condition or piping failure. Dielectric insulators are recommended by chemical treatment providers as well as many corrosion consultants as the solution for many different corrosion conditions even though they offer no possible benefit.  The recommendation to replace all smaller threaded pipe nipples with dielectrics is appropriate where thread leaks are occurring at the brass valve connections, but offers no benefit in solving a high system wide 7.5 MPY corrosion condition.  The fact that galvanic fittings were not installed to  some examples of brass drain valves does not mean that they are responsible for corrosion activity elsewhere given that the impact of galvanic corrosion is very limited to the area of the connection point only.  For many corrosion scenarios, and especially where…

Photo Gallery I8:  Working On-Site Our work has taken us on a journey throughout the United States from Alaska to Puerto Rico, and beyond.  Although the scenery may change, building piping designs remain relatively similar, with the only real changes related to material specifications, design adaptations, and maintenance provided.  A more significant difference exists in a property constructed in the past 20 years to older properties 75 years ago, than exists for those built in Australia verses the United States.  …

Photo Gallery E5:  Structural Tank Supports Unlike internal pipe corrosion, external corrosion, whether occurring to the pipe itself, pipe supports and bracing, structural steel, or any other steel component of the building property is generally due to a lack of maintenance.  Internal pipe corrosion is always present, and can be estimated either through ultrasonic investigation or suggested through the observation of other indicators such as rust deposits, failed mechanical seals, lost heat transfer efficiency, etc.  External corrosion activity is not only far more obvious, but it is also far easier to avoid or correct. Often, structural corrosion will produce a secondary impact against other critical building components. For most, long term corrosion initially results in small pinhole leaks.  Much older riveted tanks experience leaks at the rivets and overlapped seams before pinholes at the wall.  Similar to piping, older tanks had a much heavier wall thickness allowing them to survive longer.  Common to all square or rectangular tanks is the advanced deterioration of internal I-beam supports and cross bracing, as opposed to those tanks supported at the exterior wall.  Bowed side walls of any tank strongly suggests heavy internal corrosion and a far more serious threat than a weeping pinhole.