Pipe Corrosion And Its Growing Threat To Office Building and Plant Operations

Bill Duncan , Technical Representative

East Coast Industries, Inc.

P.O. Box 344

Edison, NJ 08818

The corrosion of steel piping and its related components is a continuous and virtually unstoppable process. Even with the application of available countermeasures, pipe corrosion exists as one of the most potentially damaging threats to any private, industrial, or commercial property - second only to fire.

Corrosion activity affects HVAC piping systems to varying degrees generally dependant upon the piping service, quality of the steel, age, its size and layout, joining method, chemical treatment protection, engineering design, and the specific corrosion mechanism involved. For many properties, the net result is an added maintenance problem, greater energy costs, unnecessary threat and liability, property damage, high remediation expense, and in the most extreme examples - the need for partial or total pipe replacement.

Once established, most corrosion conditions are difficult, if not impossible to eliminate or even control. Various investigative resources are required in order to firmly identify the problem - itself a major undertaking.View a photo gallery of different corrosion types.

A very first step toward resolving any corrosion problem is to establish the overall condition of the piping system through a general ultrasonic investigation. Clearly identified problem areas can then be further defined through the use of metallurgical and microbiological analysis.

By comparing metallurgical against ultrasonic test results, it is often possible to identify the extent and severity of the corrosion condition within the piping system. Well documenting not only the corrosion mechanism itself, but the remaining integrity of the entire piping system, is critically important in order to minimize the potential damage from leaks caused by any planned corrective actions.

Trends Favoring Higher Corrosion Rates

Ten years of experience in ultrasonic pipe testing at hundreds of commercial office properties and plant operations has documented how environmental concerns and government restrictions, combined with less tolerant engineering practices and cost cutting, have greatly reduced the life expectancy of most new HVAC piping installations.

Today's corrosion inhibitors have proven to be less effective under real world operating conditions when compared to prior chemical agents such as chromate and hydrazine. Under low flow or dead end conditions, corrosion and pitting often increases considerably. Whereas a 1 mil per year (MPY) corrosion rate for a condenser water system could be reasonably expected decades ago, a 5 MPY rate is now often considered acceptable, and costs significantly more to achieve.

The greater corrosion susceptibility of present-day steel pipe products is another major factor in producing many high corrosion problems, and exists beyond any reasonable control of the property owner or plant operator. With many foreign sources of piping products well recognized for their lower corrosion resistance, specifying domestic steel is strongly recommended - although offers no guarantee of fewer problems.

Together, these two elements alone can produce corrosion rates of above 25 MPY, which, virtually unheard of 30 years ago, now raise the potential to destroy any piping system within 10 years.

Another factor seen at more recent commercial properties where piping failures have occurred relates to the specified piping schedule. Most early U.S. office buildings constructed prior to 1940 used extra strong pipe exclusively throughout. In the 1950's, thinner standard and schedule 40 pipe started being substituted for less critical services such as chill water, fire sprinkler, drain lines, domestic water, and secondary water systems. From 1970 onward, extra heavy or schedule 80 stock might only be found at more critical and corrosion susceptible condenser water and high pressure steam lines. Beginning in the 1980's, however, virtually all building services piping, excepting those serving excessive operating pressures, have been specified using standard or schedule 40 material.

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