Photo Gallery B2:  Galvanized Steel to Brass Failures The direct connection of galvanized steel pipe to a brass valve is a near absolute guarantee of an advanced thread leak or failure.  This is due to the more aggressive attack of brass against the zinc protective finish of galvanized steel pipe.  Connecting copper to galvanized steel, which is less common but such as might exist at a domestic water system, produces a similar result.  The deterioration is very localized at the already weakened steel threads. Such events are far more common for open condenser water systems due to their generally higher corrosion activity.  The issue is less common for closed chilled or hot water systems, although the threat is always present.  For heated systems, such as domestic hot water, the impact is even further amplified since higher temperatures accelerate the corrosion process.  For cities like Chicago where galvanized steel pipe was inappropriately installed for domestic hot water service throughout the city, the installation of emergency brass shut-off valves only add to the problem. The vulnerability of galvanized steel pipe to this form of corrosion, generally unknown to the industry, is directly related to its time in service;…

Photo Gallery B1:  Galvanic Induced Failures Galvanic induced piping failures are due to the direct connection of two dissimilar metals having sufficiently different electrical potential.  Copper to  brass represents virtually no concern, while galvanized steel to brass will almost always produce an advanced failure.  Galvanic activity is rarely a concern for well maintained closed piping systems operating under low corrosion conditions of 0.5 MPY or less, with 60 year old properties still showing no measurable impact.  For newer piping systems, however, the threat is far greater due to the generally lower quality of today’s carbon steel pipe along with higher system corrosion levels. Corrosion activity of greater than 2.0 MPY are generally necessary for galvanic activity to introduce a threat, which is why this problem is mostly associated with open condenser water systems.  As system-wide corrosion activity increases beyond that amount, the impact of galvanic activity accelerates greatly   Blue-green deposits around the threads between a brass valve and steel pipe nipple, while showing no leaks or discolorization at the steel nipple to steel threadolet side, almost always confirms a galvanic condition and the higher probability of failure at the threads to the valve. Galvanic corrosion…

Photo Gallery Series B:  Corrosion Types And Conditions For HVAC, plumbing, and fire protection systems, the most common piping materials are carbon steel, galvanized steel, cast iron, ductile iron, copper, and brass.  Various forms of corrosion impact all such systems although the different forms of corrosion are relatively limited. Evidence of corrosion activity are often quite obvious, such as the encrustation of rust and scaling deposits around the threads, or the obvious weathering at an exposed condenser water line – indicators that should prompt immediate repairs.  Under deposit corrosion at a condenser water by-pass line, or erosion to copper pipe, on the other hand, provide no indication to their presence until a failure occurs.  Pinhole failures at today’s galvanized steel pipe may appear within a year, whereas it takes about 80 years for dezincification to produce a failure condition to older brass pipe. This series of Photo Galleries presents examples of different forms of corrosion common to the building industry, and to any other facilities similarly designed.

Photo Gallery A5:  Grooved Pipe Failures While we have found the various types of clamped pipe fittings used in HVAC and fire protection applications to provide many decades of outstanding and very reliable service, failures, when they do occur, have the potential to be utterly catastrophic.  Their basic design, while offering speed and cost savings, also introduce certain inherent vulnerabilities to corrosion. As for all piping systems, the threat is relative to the level of corrosion activity.  High corrosion activity, and especially MIC, typically focuses at the gap between pipe ends; often reaching the groove itself.  A resulting small leak at the groove, if left to continue, then produces a two front corrosion attack at its most vulnerable connection point.  Least of concern is a gasket related leak, which may require re-torquing of the bolts or a gasket and clamp replacement.  Where the groove is cut rather than rolled, substantial wall loss occurs similar to threading pipe.  Any error in rolling or cutting the groove, whereby the depth at one side is deeper and the opposite side more shallow, can produce an additional threat due to reduced clamping strength.  The common installation of carbon steel clamps…

Photo Gallery A4:  Active Pipe Leaks Leaking pipe or worse, a major failure, is often the beginning event which then prompts an investigation.  Renovations exposing heavily rusted pipe or fittings ready to fall apart at the turn of the wrench are another sure clue to the need to define piping conditions and affect repairs before a more serious failure occurs.  Water leaking from the pipe typically rates an immediate response, but not always. Emergency repair clamps are excellent but not always a feasible option depending on the physical conditions at the pipe itself.  While routing a leak to a drain is a reasonable emergency response, all too often that “temporary repair” is left to remain.  How quickly a leak is corrected is often dependent upon where the leak is occurring – with those in mechanical spaces or outdoor areas receiving far less attention.  …

Photo Gallery B5:   Internal Rust Deposits Rust deposits are created in proportion to the amount of pipe metal lost.  At corrosion rates of 5 MPY or greater, substantial rust deposits can be produced, which in turn results in severe under deposit corrosion along with other operating problems.  While a large 12 in. diameter carbon steel condenser water piping system can easily tolerate a moderate to high corrosion rate of 5 MPY, the rust deposits created will migrate to lower flow smaller diameter lines where it has a far greater and more focused impact.  Common system features such as crossover lines, by-pass lines, full diameter headers, bottom futures, and other low-flow configurations then become the site of far greater corrosion loss.  Such deterioration is hidden from sight, unmeasurable except through ultrasound, and generally not known to exist. A cross section of any heavily deteriorated pipe will often show large growths of rust termed “tuberculation.”  Removing such rust deposits will then produce visual evidence of deep pitting proportional to the height of the deposit itself.  Conversely, an ultrasonic measurement of deep wall loss defines tuberculation deposits, at the same time that their visual observation defines deep under deposit…

Photo Gallery A3:  Thread Leaks The first and most common indicator to a corrosion issue, an impending failure, or pipe weakness problem is a leak at the threads.  With approximately 50% of its wall thickness cut away during installation, this area of pipe will always fail first, and with most threaded systems constructed of schedule 40 pipe, a remaining wall thickness of less than 0.085 in. at the thread cut is common. Various factors influence the severity of a failure such as the use of galvanized steel connected to a brass valve, age, operating pressure, physical impact, and pipe schedule.  Our finding of advanced failures of threaded thin wall schedule 10 and even ultra thin wall schedule 7 pipe for threaded branch lines at fire sprinkler systems, while still a shock to many building owners and engineers, should have been expected. A typical corrosion scenario for threaded pipe is for a small leak to develop and then seal itself due to rust and other internal particulates filling the void.  As the water and dissolved solids slowly migrate through the leak, the water evaporates to leave an encrustation of rust and scale that is seemingly growing along…

Photo Gallery A2:  Pipe Repairs The primary action in every piping failure is to stop the flow of water and the damage it causes as soon as possible.  Where shutting down service is not an option, this is often accomplished by the application of an emergency clamp and even the use of duct tape for lower pressure events.  A knife sharpened pencil or broom handle has actually saved the day for many engineering personnel having no other immediate means.  Rubber gasket material and band clamps work remarkably well for some smaller pinholes.  Emergency repairs buy time to schedule pipe replacement, conduct shutdowns, and make plans generally in proportion to the size and importance of the failure event. For many leaks, a quick temporary solution is found, but then left in place until a much larger and more damaging failure occurs – to no real surprise.  A temporary fix in the form of a catch basin and garden hose to a floor drain only lasts until the pipe corrodes sufficiently to rupture.  As this gallery shows, having some form of emergency repair bandage on hand or an inventory of pipe clamps of varying sizes is never a…

Photo Gallery A1:  Pipe Failures Many early occurring and often obvious signs of a corrosion or pipe weakness problem are ignored up until the moment that a failure occurs.   At that instant priorities change, with – the larger the failure, the greater the level of panic and overcompensation.  Most piping failures, at least initially, are small.  They may be in the form of a slow drip at a thread or ERW weld seam, a weeping pinhole at copper pipe, or some wet insulation.  Ironically, the greater the level of pitting within a piping system, the more likely its deepest penetration will produce an advance “tell-tale” warning indication that a larger failure event is on the way.  Low and extremely uniform wall loss occurring over  decades, on the other hand, may produce a substantially larger failure with no prior notice whatsoever. Worst events are always total pipe separation resulting in catastrophic failure and million dollar losses.  Fortunately, most piping failures provide an advance warning for those who are observant.  …

Photo Gallery Series A:  Leaks and Failures A pipe leak is often the beginning event which then prompts some form of investigation or response.  The first indication of weakness is very much dependent upon the piping system itself, in combination with its age, quality of the piping materials installed, maintenance or lack thereof, chemical treatment if appropriate, and other factors.  Premature thread leaks at condenser water systems are almost always the first indication of a condenser water problem, whereas leaks at grooved clamped fittings appear at more advanced stages of failure.  Copper pipe failures are typically in the form of pinholes, and similar to those at old dezincified yellow brass pipe.  Fire protection pipe can last over 100 years for schedule 40 standpipe service, yet only 5 years for a “dry” system constructed of schedule 7.  Heavily worn cast iron waste pipe can fracture with no advance notice whatsoever.  Any total thread separation failure usually spells disaster. Renovations exposing heavily rusted pipe or fittings ready to fall apart at the turn of the wrench are another sure clue to the need to define piping conditions before a more serious failure event occurs.  For dual temperature systems, any pipe that is…