This move by design engineers and contractors from extra heavy to standard grade pipe has taken a further and more risky step in the past 10 years with the use of thin wall schedule 10 or schedule 20 steel in many fire sprinkler and condenser water systems - often with disastrous results.

8 Year Old Schedule 10 Condenser Water Pipe

For a section of 8 in. condenser water pipe that would have provided an extra heavy wall thickness of 0.500 in. for a 1950's property, or 0.322 in. at a facility constructed of schedule 40 in 1985, the frequently seen use of schedule 10 now provides only 0.188 in. of available wall thickness under substantially higher corrosion conditions.

Advanced failures are therefore quite frequent where schedule 10 is employed, and easy to understand in viewing the above relative illustration of pipe wall thickness. View a more detailed comparison of various wall thickness values for carbon steel pipe.

Unavoidable Corrosion Threats

Not all piping failures can be attributed to a high corrosion rate however. To a great degree, many of the current problems seen at commercial office buildings and plant facilities are simply age related. With many building properties reaching 40 years of service or more, the cumulative effects of even a moderate and generalized corrosion condition will add up to produce substantial material losses.

A low (and rarely seen) 1 mil per year (MPY) corrosion rate at 12 in. schedule 40 condenser or chill water pipe, while seemingly minor, actually results in the annual loss of 12.8 lbs. of steel for every 100 linear feet of pipe. Multiplied by the number of years in service and overall length - and the true magnitude of system corrosion takes on much greater significance than when reported simply as 1, 2, or 5 mils per year.

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