Abstract: The article will provide an overview of operational challenges faced by data centers and effective solutions by using latest Honeycomb and Gas Phase Filtration technology. It will also cover the case studies from industrial and commercial sector outlining the role and importance of gas phase filtration technology in controlling gaseous contamination.
For efficient working of data centers, data center managers have to overcome various operational challenges such as :
Data centers may have harmful environment arising from infiltration of outdoor particulate or gaseous contaminants. They are more prone, if the offices are situated near to landfill sites, sewerage/drains, high density traffic, process industries, etc. Infiltration of these gaseous contaminants can lead to electronic corrosion, which can result in increased downtime, low productivity, electronic equipment disturbance and failure. Most of the challenges stated above, can practically be tackled by incorporating a Gas Phase Filtration equipment in data centers. A Gas Phase Filtration equipment removes contaminants and eliminates downtime by removing corrosive gases through the process of chemisorption.
A data center or computer center is a facility used to house computer systems and associated components, such as telecommunications and storage systems. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g., air conditioning, fire suppression) and security devices. (Source: Wikipedia)
IT operations are a crucial aspect of most organizational operations. One of the main concerns is business continuity; companies rely on their information systems to run their operations. If a system becomes unavailable, company operations may be impaired or stopped completely. It is necessary to provide a reliable infrastructure for IT operations, in order to minimize any chance of disruption.
India is on the verge of witnessing a boom in the Data Center space with the Data Center business currently already above Rs. 10,000 Crores.
While the size of particulate contaminants is upto 0.1 microns which can be removed by using particulate filters; gas phase contaminants are usually much smaller.
Effects of AIRBORNE CONTAMINATION on data center equipment can be broken into three main categories:
One mechanism by which dust degrades the reliability of printed circuit boards involves the absorption of moisture from the environment by the settled dust. The ionic contamination in the wet dust degrades the surface insulation resistance of the printed circuit board and, in the worst-case scenario, leads to electrical short circuiting of closely spaced features via ion migration.
Deliquescent relative humidity, the relative humidity at which the dust absorbs enough water to become wet and promote corrosion and/or ion migration, deter-mines the corrosivity of dust. When the deliquescent relative humidity of dust is greater than the relative humidity in the data center, the dust stays dry and does not contribute to corrosion or ion migration.
Leakage current due to dust that settled on printed circuit boards increases exponentially with relative humidity. Keeping the relative humidity in a data center below 60% will keep the leakage current from settled fine dust within the acceptable sub range.
For data center without air-side economizer, the ISO class 8 cleanliness may be met simply by the choice of the following filtration:
ASHRAE Recommended Environment for Temperature & Moisture (ASHRAE 2008, 2011)
Temperature : 18°C (64.4°F) to 27°C (80.6°F)
Low-end moisture : 5.5°C (41.9°F) dew point
High-end moisture : 60% relative humidity or 15°C (59°F) dew point
For data centers located in areas which have traces of corrosive gases, Gas-Phase Filtration of inlet air and air in the data center is highly recommended.
Sulfur-bearing gases, such as Sulfur Dioxide (SO2) and Hydrogen sulfide (H2S) are the most common gases causing corrosion of electronic equipment. SO2 and H2S alone are not very corrosive to silver or copper but the combination of these gases with gases such as NO2 and / or Ozone are very corrosive. The corrosion rate of copper is a strong function of relative humidity, while the corrosion rate of silver has lesser dependence on humidity.
Two common modes of IT equipment failures due to environmental contamination are as follows:
Copper creep corrosion on printed circuit boards
Corrosion of silver termination in miniature surface-mounted components
ASHRAE recommends that data center operators maintain an environment with corrosion rates within the following guidelines:
It is important to understand that while ISA standard – 71.04 (ISA 1985) is only based on copper corrosion levels, measuring of silver corrosion levels is as important for the following two main reasons:
Typical silver corrosion rate in one of data center in USA due to presence of SO2 & NO2.
Based on test results of corrosion, it is possible to classify the environment into one of 4 severity levels as outlined in Table below:
Corrosion Level in terms of (in Angstrom) as per ISA
| Class | Severity Level | Copper Reactivity | Comments |
| G1 | Mild | <300Å | An environment sufficiently well-controlled such that corrosion is not a factor in determining equipment reliability. |
| G2 | Moderate | <1000Å | An environment in which the effects of corrosion are measurable and corrosion may be a factor in determining equipment reliability. |
| G3 | Harsh | <2000Å | An environment is which there is a high probability that corrosive attack will occur. These harsh levels should prompt further evaluation resulting in environmental controls or specially designed and packaged equipment. |
| GX | Severe | >2000Å | An environment in which only specially designed & packaged equipment would be expected to survive. Specifications for equipment in this class are a matter of negotiation between user & supplier. |
To understand this better, it is important to relate these conditions with typical levels of various corrosive gases (in ppb) in the controlled environment. The same are given in Table below:
| Parameters | G-1 Mild | G-2 Moderate | G-3 Harsh | G-X Severe |
| H2S | < 3 | < 10 | < 50 | > 50 |
| SO2 | < 10 | < 100 | < 300 | > 300 |
| Cl2 | < 1 | < 2 | < 10 | > 10 |
| NOx | < 50 | < 125 | < 1250 | > 1250 |
In summary, data center equipment should be protected from corrosion by keeping the relative humidity below 60% and by limiting the particulate and gaseous contamination concentration to levels at which the copper rate is less than 300 Å per month and silver corrosion rate is less than 200 Å per month.
To help Data Center facility managers to take corrective steps in time, real-time monitoring is also recommended with gas- phase filtration air-cleaning systems, in order to track the efficiency of the filters. Two types of real-time reactive monitors are commercially available. One is based on measuring the rate of increase of corrosion product mass using a quartz crystal micro-balance. The other determines gaseous corrosivity by measuring the rate of electrical resistance increase of metal thin films.
There are mainly two ways of reducing gaseous contaminants in the environment which are as follows:
Wet scrubbers operate on the principle of passing contaminated air thru the liquid media having properties to dissolve the unwanted corrosive gases. These scrubbers are normally used for protecting the external environment.
In dry scrubbers the contaminated air is passed through adsorbant in granular form, impregnated with active chemicals to adsorb the unwanted gases and then nutralize/oxidise the same thru chemical reaction.
This filtration principle is also known as Chemisorption. The contaminated impurities in air are adsorbed and is chemically neutralized. The contaminated air is passed through pre-filters which traps suspended impurities. The air stream is then passed through chemical media beds to chemically oxidize/ neutralize gaseous impurities. The air is then passed through particulate final filters before supplying into the data center. Typically, Chemical media beds are designed with media face velocity of 80 -125 FPM.
Chemicals in media beds get consumed over a time as these react with gases which are adsorbed in the media. The goal is therefore for the chemical filter to have the maximum amount of chemical for chemical reaction for a given physical size/geometry and air carrying capacity with minimum pressure drop. Till date, chemical filtration was being done by granular or pelletized media which causes substantial pressure drop hence requiring greater fan power leading to more power consumption for the same work done.
Typical configurations of Gas Phase Filtration System commercially available are:
While effective in controlling the desired levels of corrosive gases in Data Centers, limitations of these granular/ pelletized media based systems are:
Above limitation in using granular based dry scrubbers in commercial installations led to technologies allowing adsorbtion media in Honeycomb matrix to be impregnated with active chemicals in micropores of the substrate.
The new macro porous honeycomb matrix based chemical filter can hold very large amount of chemical for chemisorption and has ability to neutralize even ultra-low concentration of gaseous contaminants. This new technology can remove contaminant gases, odorous gases or volatile organic compounds more efficiently and effectively from air supply stream.
These filters provide:
To help better understanding of the various technologies available for gas phase filtration, Figure gives snap shot of Evolution of Gas Phase Filtration technologies.
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