Application – Data Centers

• Systems Overview

The operation of any critical data center greatly depends upon the reliability the HVAC and fire suppression systems.  As data centers grow larger and more complex, so must their cooling operations.  With potentially billions of dollars flowing through the servers each day, a shut down is simply not an option.

While there is always the intention to minimize water carried through any computer or server room, certain realities are unavoidable.  Electrical equipment produces heat which needs to be removed through either condenser water feeding air conditioning units or chill water feeding air handling units – both options presenting very different threats.  Condenser water inherently has a higher corrosion rate over chill water, yet typically does not require insulation nor is subject to sweating and external corrosion as for chill water pipe.  Most cooling pipe is run under the computer floor making a failure less immediately noticeable where it is in close proximity to electrical services and cabling.

More of a concern, the entire area must be protected in the event of a fire.  This threat had thought to have been resolved by the design and installation of dry and pre-action fire sprinkler systems that would carry no water until a true fire emergency occurred.  Dry and pre-action fire sprinkler systems are similar in their piping layout but in fact are “dry” in name only.  They can be called dry systems, viewed as such, expected to drain fully, and believed to hold no water over critical computer and electronic equipment, but the fact remains that all such systems contain some water in all horizontal lines.  Filled just once for its initial testing, some volume of water will remain due to the virtual impossibility of removing it completely – an event which then impacts the pipe from that point forward.  Of the many misconceptions that exist regarding fire protection systems, believing that a dry fire system is actually “dry” tops the list.  Its remaining water, covered with abundant air and oxygen, then initiates an accelerated and often very aggressive attack against the pipe.

Various speculative theories and practices exist in reducing the threat of water carried next to sensitive electronics although ultimately the threat can never be eliminated.

• Common Vulnerabilities

  • • HVAC

HVAC systems are critically important to any data center facility and typically consist of chill water, condenser water and hot water heating.  The condenser water system is limited to a relatively small portion of the building between the outdoor cooling towers and chillers located within the mechanical room, although some older designs favor condenser water serving interior compressor units.  While a leak at the condenser water system would not directly impact the critical equipment for most data centers, its failure, depending upon the extent, can potentially shut down the refrigeration chillers themselves.

This has been addressed through various forms of redundancy as well as both large chill water storage tanks as well as ice storage – solutions on one hand, but new vulnerabilities on the other.

With plans for future upgrades and greater operator control, it is common for multiple by-passes, and other dead end future configurations to be included as part of any condenser water system design.  Although well intended, such features also introduce hidden weaknesses to the system, given that areas of low or no flow conditions are ideal locations for internal rust product and captured particulates to settle, causing aggressive and localized under deposit corrosion.

Unlike like past condenser water designs where pipe headers would be reduced at each chiller, pump, or cooling tower take-off, they now remain at their maximum diameter – in effect transforming all headers into large settling tanks.  Efforts mistakenly believed to eliminate this threat by installing small by-pass lines at each header end are actually worthless.  Water filtration, commonly installed to most data centers as a precautionary measure, are generally inadequate to control the problem and are installed improperly.  The presence of water filtration may suggest that rust and dirt is being removed, when in fact little to no benefit exists.

A more immediate risk to the critical data center equipment is caused by the chill water system.  Compared to the larger mains which move water throughout the building, much smaller pipe typically runs-out to the individual air handler units.  As pipe diameter decreases so does its initial wall thickness, thereby raising its vulnerability should a corrosion condition develop.  Increasing the level of risk is the fact that this smallest diameter pipe, if not copper, is typically schedule 40 and threaded.  An additional threat to all chill water systems is the fact that they can suffer  external wall loss due to moisture condensation as well as allow any water droplets to migrate.  For data centers, the possibility of failure at the server cooling system is a constant and very costly concern.

• • • Fire Sprinkler

As fire suppression systems have become more complex, they have also become more vulnerable to not only failure in terms of leaks, but also failure in terms of their proper functioning.  Various attempts have been made to reduce the the threat, such as the move toward galvanized steel pipe, but with often opposite results.  Part of the issue relating to leaks is the much higher corrosion occurring to dry and pre-action fire sprinkler systems caused by 5 main issues:

• • • • • • The use of thinner piping materials such as thinwall schedule 10 and ultra thinwall schedule 7
          • Threading thinwall schedule 10 and thinner pipe
          • The fact that dry and pre-action fire pipe is never actually “dry”
          • Lower quality steel pipe
          • Poor quality galvanized pipe

While the unwanted release of water from a fire sprinkler system is the primary concern for any data center, a far greater threat exists given the amount of iron oxide rust product that can be produced over time.  This is always a lesser concern for galvanized steel pipe due to its more localized mechanism of failure, and primarily impacts carbon steel dry and pre-action fire sprinkler systems.

Although the presence of internal rust product cannot be measured ultrasonically, loss of wall thickness can be measured.  This wall loss can then be translated into a rough theoretical estimate of internal rust deposit by calculating the volume of pipe wall loss along the bottom and lower sides in comparison to the less affected top and estimating the volume of less dense rust product created from its oxidation.

The result is a theoretical estimate of rust product, which is a new feature of our latest enhanced report format, as described elsewhere on this site.

• Pipe Related Issues

Declining material quality is one of the foremost problems for any building property.  As we have overwhelmingly documented on this site, there are significant differences in quality and corrosion resistance between pipe manufactured decades ago and recently manufactured pipe.  For condenser water and chill water, corrosion inhibitors can still provide good wall loss protection if strictly maintained, but for fire systems, corrosion inhibitors are not employed.  This means that service will be entirely dependent upon both material quality and system design, installation and maintenance.

• Top Failure Locations

HVAC

• • • • • Condenser water
        • Threaded condenser water lines
        • Smallest diameter threaded chill water
        • Dissimilar metal connections
        • Drain lines, future connections, by-passes and low flow zones
        • The bottom of any large header

Fire Sprinkler

• • • • • Building inlet line
        • Pipe prior to a fire booster pump
        • Areas of greatest water movement
        • Dry and pre-action fire sprinkler systems
        • Thinwall schedule 10, 7, or 5
        • Threaded schedule 10 or 7 pipe

• Testing Priorities

With the specific vulnerabilities defined above, areas of priority for testing can be easily established.  When evaluating the condition of HVAC systems it is important to recognize that the highest corrosion activity is generally present throughout the condenser water system, and specifically at areas having low or no flow.  A top priority location would be at any chill water pipe within server rooms and specifically at the smallest diameter feeds from the mains.

© Copyright 2005 – 2025 – William P. Duncan, CorrView International, LLC