Unique Corrosion Concerns Affecting The Most Critical Of All Piping Systems
Within the realm of HVAC applications, data centers are considered the most critical. Absolutely flawless and uninterrupted service of the cooling system is required to maintain computer room temperatures, without which, failure of the computer hardware will occur. Although we still consider it a term relative to often unavoidable events, any larger data center “can never” be shutdown, and most are designed for 20 or more years of uninterrupted service.
“Never” Is A Relative Term
Corrosion, however, does not recognize the word “never,” and progresses relentlessly and without regard to the critical nature of any piping system. This is why data centers are given such higher level of chemical treatment protection, monitoring, and maintenance.
Potential problems at data center cooling systems still go unrecognized, however, since they are generally hidden from view. Corrosion monitoring, typically in the form of corrosion coupons, produce the same inaccurate corrosion rate information to data centers as they do to any other property, just with greater consequences. In response, multiple sets of corrosion coupons may be installed from different vendors to provide double or triple the volume of incorrect wall loss data.
Lower quality steel pipe in terms of its corrosion resistance as well as undersized dimensions means that the same preventative measures that worked so effectively at one facility built 20 years ago, may be totally ineffective at another. Although termed a “critical facility” from the beginning design stage, a savings through the use of lower cost foreign pipe, or in other areas, will often be revealed.
Design A Growing Issue
Piping layout design plays a major role in the corrosion problems we document. The interest to provide for total flexibility in operation and most importantly multiple redundancy has resulted in more complex piping designs which unknowingly add new corrosion threats. By-pass lines, crossovers, multiple feeds, dead end futures, and other features of most data center cooling systems create areas where particulates, microbiological growths, and iron oxide rust can deposit to cause significantly higher localized pitting. Drains and vents at each isolation point then produce a potential failure location. Small diameter by-pass connections, believed to prevent corrosion problems re actually worthless, and produce no benefit whatsoever. Water filtration, often large side stream sand filtration units incorrectly installed, barely offer any benefit. A few buckets of sediment in a large backwash settling tank means that the majority of airborne particulates and rust product has settled within the piping system itself.
Insulation at the condenser water piping, generally unnecessary, makes any ultrasonic corrosion monitoring program more difficult, and often leads to addressing those areas of the system most easily reached, rather than those of greatest threat. Chill water insulation is often insufficient although less of a concern since drier air exists at most data centers.
Understanding the vulnerabilities at a critical data center is a pre-requesite to a thorugh and informative ultrasonic piping assessment. For data centers especially, testing a few random sampling points will never produce the information necessary to either define the level of threat present, or assist in resolving the issue.
Corrosion threats exist at many low flow areas not always easily accessible. Threaded fittings typically present not only the greatest and most widespread threat, but can be very difficult repair depending upon their location. Under data floor chill water pipe is generally less of a concern in comparison to open condenser water piping, although still capable of presenting issues due to ineffective insulation, and dissimilar connections between steel and brass or copper.