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Life Threatening

Corrosion, once it has been identified at a fire protection system, is typically viewed exclusively in terms of the cost for pipe replacement.  By the time it is finally recognized, years of deterioration have often occurred.

With repair, corrosion remediation, and with the removal of rust deposits a difficult and often unlikely to succeed option, partial or complete fire pipe replacement is often the only alternative – at tremendous expense and inconvenience.

• Greater Problems Today

The incidence of corrosion problems at fire piping, virtually unheard of 25 years ago, has now become an every day issue.  Approximately 30% of our involvement in corrosion and ultrasonic pipe testing today relates to failures at fire protection systems.  With some of the oldest fire protection piping at near 90 years old still in excellent condition, and capable of providing many decades of additional service.  Clearly there are factors related to more recent installations which are responsible for today’s more advanced failures.

The predominant use of thin wall schedule 10 pipe, more corrosion susceptible steels, poor quality galvanizing, insufficient grade, and seamed pipe are the primary physical influences often associated with premature fire system failure.  Installing thin wall schedule 10 pipe rather than schedule 40 not only cuts its wall thickness in half, but can reduce service life by 500%.

Dry sprinkler systems, now more frequently installed, are associated with some of the most advanced and complete piping failures we have documented.  A dry system presents inherently greater threat due to the fact that inadequate grade always allows water and moisture to remain within the lines – the source of dramatically higher corrosion losses.  In reality, it is never “dry.”

Frequent testing, flushing, and draining requirements regularly bring into every fire system abundant fresh oxygenated water to raise corrosion levels.  With corrosion against steel pipe directly related to available oxygen, the potential benefits of such test procedures to confirm the operation of key system components has ironically resulted in the premature destruction of the fire piping itself.

Flushing procedures to clear a fire protection system of accumulated iron oxide rust and debris are of extremely limited effectiveness in such a widespread network of horizontal dead-end and often air-bound piping – thereby allowing most rust product to remain behind.  This photograph at left of a 4 in. main fire distribution line, regularly drained and flushed, easily proves such argument.

And if the above factors are not a sufficient detriment to fire protection systems in themselves, add the more recent threat of microbiologically influenced corrosion, or MIC.  Where even a severe general corrosion condition may take 10 years to produce a leak, microbes in the water supply can literally eat and dissolve their way through 6 in. schedule 10 steel fire pipe in under one year.

Unquestionably, multiple forces exist against modern fire protection systems to produce threats and concerns still not widely understood nor recognized within the fire protection and building operations industries.

• Different Consequences

The similarity between a corrosion problem at a fire protection system and other HVAC or plumbing related piping systems ends with the economic cost of replacement and interference with regular building operations.  A relatively small corrosion induced pipe failure at a high rise commercial office building can easily exceed $1 million in just water damage alone.  Replacement of a condenser cooling or domestic water system for a 40 story high rise office building can mean an unexpected expenditure exceeding $10 million.

The failure to provide sufficient cooling water to the mainframe computers of a major financial institution are estimated at millions of dollars per minute of downtime.  Huge economic losses indeed, but rarely does such corrosion-related failure result in the loss of life.

Corrosion at a fire sprinkler system, however, directly impacts the life blood of the fire protection system itself – water, and negates the central purpose of every other single piece of equipment designed and installed into the fire system.  Fire sensors, alarms, pumps, control panels, actuating valves, sprinkler heads, and standpipe connections are all designed with the primary interest to move abundant water to the source of the fire as quickly as possible.

Water pressure, flow rate, sprinkler head location and their density, orifice size, discharge times for dry pre-action systems, and every other conceivable aspect of a fire protection system are precisely defined by NFPA Chapter 13.  The frictional loss of water based upon the internal surface resistance of new pipe, the flow resistance of each fitting, valve, and elbow, and most importantly, predictions of flow rate based upon inside pipe diameter, define a fire protection system that is expected to supply the required volume of water to every point of the system on demand.

Assumptions are made by everyone that fire protection systems, as designed and installed, will be in similar physical condition when called upon in a real fire emergency – whether that call is tomorrow or decades away.

• Corrosion’s Terrifying Impact

Internal pipe corrosion, however, influences every aspect of a fire protection system – from interfering with the proper operation of individual equipment components, to constricting inside pipe diameter and reducing flow.  In its most severe form, corrosion may produce through wall penetration and / or sufficient internal rust deposits to clog the smallest branch lines and sprinkler heads entirely.

Is there even the slightest possibility that the huge volume of loose rust shown above in the 4 in. main, after being forced into this 1-¼ in. branch line of the same fire system, would allow any water through the smaller orifice of a 3/8 in. sprinkler head?

Obviously not.  And yet this condition remained unknown for years until multiple leaks prompted an ultrasonic investigation.  This fire system, as most, was assumed functional because regularly prescribed testing and flushing indicated accept-able results.  In fact, no fire protection existed!

• Unstoppable Loss

Corrosion is an unstoppable force of nature seeking to revert steel back to its original form of iron.  It is extremely difficult to control for even HVAC systems having the benefit of constant circulation and the daily addition of chemical inhibitors and high-tech electronic monitoring.

But unlike HVAC systems, which are typically designed with a corrosion factor taking into account lost heat transfer efficiency due to deposit buildup and reduced wall thickness due to corrosion, no such consideration for fire protection systems exists.  Fire piping is installed with the unreasonable expectation that no significant corrosion will occur to impact system performance.

• Material Weakness

Ultimately, the service life of a fire sprinkler system is a question of pipe quality, wall thickness, and its inherent corrosion resistance, verses the corrosive potential of the local water supply and water flow.  Seamed pipe, and pipe of some foreign manufacture, almost always suggests the potential for greater corrosion activity before the system is even filled.  The use of thin wall schedule 10 pipe simply doubles the potential negative effect of any individual physical weakness or corrosion condition.

Galvanized pipe, still viewed as the solution to the corrosion of carbon steel and widely used in dry fire systems, rests its effectiveness at providing long service life entirely upon the quality of the zinc protective finish.  Where the galvanized finish holds, corrosion activity is prevented. Where it fails, however, the entire corrosive potential in that area then focuses its attack upon one or more small areas to produce deep localized pitting and penetration best described as having been produce by a drill bit.

Nearly impossible to evaluate for future service life prior to installation, the use of galvanized pipe often means a hopeful expectation of corrosion-free operation, but with the more likely result of more advanced failure over carbon steel.  Combining multiple factors such as poor quality galvanized seamed pipe in a dry fire system with inadequate pitch virtually guarantees a corrosion problem that will render it totally worthless in under 10 years, and often sooner.

Pipe quality is still generally unquestioned as long as it meets the ASTM specifications.  Local water quality, which can vary greatly in terms of its chemical properties such as hardness, pH, conductance, alkalinity, chlorine content, and of course MIC, is starting to be considered in estimating future corrosion problems at fire pipe.  Any such planning, however, is likely far less than required to fully address the potential impact of corrosion which can evolve from a very wide variety of sources.

• Inherent Threat

For most building owners / operators, such inherent corrosion threat remains generally unrecognized.  Signing off on the installation of a new fire protection system implies decades of useful service life, and a system which has the necessary safeguards through design, technology, maintenance, and inspection to ensure its effective operation if ever called into service.

Fire protection contractors install a system design carefully defined down to bolt size and the spacing distance between pipe hangers.  Fire protection consultants and engineers follow well thought out and frequently improved guidelines in designing an automatic and very effective response to a wide range of potential fire threats.  Every possible aspect of a fire protection system seems to have been more than adequately defined except to address the inevitable and unstoppable deterioration of the steel pipe by water itself.

• Documented Failure

On April 30, 1998, an electrical fire erupted in the laundry room of a nursing home in Lamoni, Iowa.  While the sprinkler heads functioned correctly, no water was released due to them being totally plugged with heavy rust deposits.

Fortunately, no loss of life occurred due to the quick actions of the rescuers, but the outcome could have easily been tragic.  Further investigation into the failure showed that maintenance was current, and that the fire sprinkler system had been inspected and regularly tested according to NFPA Chapter 25 standards.  A similar event near Philadelphia in 2000 caused a woman’s death.

Laboratory identification to the presence of MIC throughout the piping system pinned a cause to the Iowa fire sprinkler failure, and raised important awareness to a seemingly new problem.  By focusing attention mostly toward MIC and at specific geographic areas of the United States, however, the potential for similarly clogging sprinkler heads due to rust product produced by more common generalized forms of corrosion, far more prevalent, was entirely overlooked.

• Not Just MIC

Today, severe rust found within a fire protection system is automatically suspected as MIC, until laboratory testing usually proves otherwise.  In fact, by approximately 5 to 1, the majority of failure problems found at fire protection piping are the result of generalized and pitting corrosion which is present to some degree in most fire systems.  It is a worldwide concern.

MIC certainly accelerates pipe deterioration, and raises the potential to destroy a fire system at phenomenal corrosion rates exceeding 0.100 in. of steel per year.  Equal and potentially greater threat exists, however, due to more slowly occurring and gradual effects of generalized corrosion over longer periods.  To the building owner / operator, however, the net effect is the same – with the problem hidden entirely from view until revealed by the first leak.

• Failure Before Fire

Today, the economic impact and life threatening consequences of corrosion to fire pipe still remains generally unrecognized and too often ignored.  Indeed, no worse time exists to discover a corrosion problem within a sprinkler system than during an actual fire emergency.  Although the use of heavier pipe is one obvious answer to longer system life, it also has a negative aspect as well, given that under corrosive conditions, a greater amount of rust product will be produced.

Ironically for many property owners, their use of thin wall schedule 10 fire pipe, leading to a more advanced failure, also provided an earlier notification of a hidden corrosion problem prior to an actual fire.  In such cases, expensive pipe replacement can be viewed as the cost of avoiding far greater tragedy.

• Major Liability

The failure of fire protection piping after 50 years is a reasonable product of nature – corrosion, and old age.  Its failure after 2 years is someone’s fault.  Property owners reference a fire system designed for long service life and toward which a testing and maintenance agreement indicated no cause for concern.  Installation contractors cite a fire system design followed explicitly.  For all those involved, defense rests that corrosion is a natural occurrence, hidden from view, and therefore unknown and beyond their control.

Extensive litigation often follows, with the final cost of repair or replacement ultimately borne by the insurance company.  Death as a result of a fire sprinkler failure only increases such conflict exponentially.

• Changes Required

The assumption that a fire sprinkler system will perform as designed, 10 or more years after installation, may require new consideration – regardless of the testing and maintenance checks currently performed.  Although the overwhelming majority of fire protection systems will function flawlessly when called upon, sufficient threat remains to warrant further pro-active measures.

With the current trend in fire protection continuing toward those factors responsible for more advanced failures, tragedies such as occurred in Philadelphia will increase.  Greater recognition of this problem, aided by more invasive testing and monitoring for hidden corrosion conditions, exists as the only response currently available.

You can view and download our two page handout on this subject below.

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