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Someone To Blame

The corrosion of HVAC piping systems and their related equipment presents the most potentially damaging losses to any private, industrial or commercial property next to the threat of fire.  Direct losses exist in pipe repair and replacement costs, but often the most far reaching losses are in the form of litigation due to water/property damage and lost productivity.  Some of the most damaging pipe failures we are aware of have shut down entire high rise office buildings, or caused extensive damage to multiple floors of tenant space.

Where a building property has the responsibility of providing basic heating and cooling services as part of their lease contract, the failure of any large and pressurized piping system, especially where significant water damage is concerned, means a very expensive repair and damages bill for those responsible.

• Chemical Treatment No Guarantee

Methods to minimize corrosion and monitor its severity exist, but do not necessarily guarantee trouble free service.  Corrosion caused leaks can occur even though top quality water treatment is provided, and greatly varying pipe conditions can be found in different areas.  Certain failures, in fact, may be totally unrelated to the general quality of the chemical water treatment service, and instead be due to other design and operating conditions.

Corrosion monitoring is often performed at only the largest or more critical facilities, and where current or past corrosion problems have raised interest in monitoring future losses.  In general, smaller properties place less emphasis on corrosion control.  Likewise, a smaller chemical water treatment company is often less likely to recommend corrosion monitoring to their clients unless some special circumstance exists or request is made.

• Corrosion Coupon Deficient

Corrosion testing traditionally is in the form of corrosion coupons, which have been documented to under report the true corrosion activity within a piping system by 10 times or more.  Coupons report the effectiveness of the water treatment chemicals in slowing wall loss against new virgin steel under controlled conditions, but not chemical efficiency in protecting the actual piping.  The presence of any interior deposits reduce inhibitor effectiveness greatly, and where a heavy accumulation exists, can prevent the chemical inhibitor from providing any corrosion protection whatsoever.  In addition, one set of coupons at one location of the property can never represent the many forms of corrosion possible due to different piping conditions.

While corrosion coupons are often presented as a quantitative measurement of system corrosion activity, or assumed to represent such by building and plant operators, this is not the case. Often it is not until a failure or corrosion problem arises and other diagnostic testing is performed that the lack of true wall loss measurement by corrosion coupons is realized.

Our experience in ultrasonically testing condenser water piping systems has frequently documented clients who had operated assuming a 0.250 mil per year (MPY) coupon based wall loss estimate, when in fact the true loss was 4-5 MPY.  In the years of operation where high corrosion losses were occurring, valuable time to identify and correct the problem were lost.  In far too many examples, however, a property owner or operator only realizes that a corrosion coupon result does not represent actual pipe corrosion after a corrosion problem is clearly evident.
Various Causes Possible

Except where an engineering defect, installation deficiency, or some other physical fault exists, most piping failures due to corrosion problems are extremely difficult to define.  The true cause of a piping failure may be due to:

• • Make-up water quality
  • Current chemical water treatment effectiveness
  • Prior chemical water treatment effectiveness
  • Inadequate chemical feed equipment
  • Microbiological presence
  • Operating conditions
  • Stray electrical fields
  • Local air quality conditions
  • Corrosion susceptible pipe
  • Initial system cleaning and start-up
  • Installation of thin wall pipe
  • System draindown
  • Low flow or dead end conditions
  • Particulate settlement

While one or a combination of underlying and often unknown conditions may contribute to a pipe leak or failure, legal liability to some degree will be placed upon the property owner or operator who “should have known” of such condition.

© Copyright 2024 – William P. Duncan, CorrView International, LLC