Friday 2 March 2012

Standby generator fuel contamination

I paid my annual visit to Data Centre World in Olympia London yesterday. Several items caught my attention. One of those was the IPU Fuel conditioning stand. I'd read about the "diesel bug" problem a couple of months ago but not really paid much attention, but it could be an important issue for Data Centres/businesses which depend on diesel powered standby generator for their electricity backup. This may be an issue which IT managers think is purely a responsibility for the facilities manager, but at the very least they should ensure that their FM colleagues have considered the issue. Similarly if your business operates in a multi-tenanted building it may be appropriate to ask the Landlord how they approach this matter.

Essentially the diesel bug is contamination in diesel fuel arising from bacterial, fungal, yeast growths which can grow in water contaminated diesel. The diesel bug can grow in to a mat which floats between the interface of diesel/water layers. The mat can also form as a plaque on the inner surface of the diesel tank, pipework and filters. If that mat is disturbed chunks can float off and be sucked into the fuel filters of a diesel motor, such as a standby generator. In a way it is a bit like the diesel engine is having a heart attack as essential feeds are blocked. The by-products of the diesel bug can also create acidic conditions which can corrode metal tanks and fittings.

If the fuel filter of  diesel motor becomes clogged with contaminants the motor will be starved of fuel and cut out. This is not a good thing if there is no mains power and your data centre is depending on the standby generator. Even in N+1 resilient generator configurations the risk is high if the fuel is contaminated.

Diesel fuel in the UK can contain up to 7% bio-diesel. Bio-diesel is hygroscopic, which means it is prone to absorb water vapour from the air. In the diesel storage tank this absorbed water can separate out in to the base of the tank, potentially leading to the diesel bug. If the water reaches the injectors of the diesel engine it can cause serious damage to those injectors.

IPU were offering fuel polishing units which can be installed, either permanently or as a mobile unit, to remove contaminants, such as water, from the stored diesel in the fuel tanks of a standby generator. They also provide assistance in testing the fuel to detect contamination and bacterial growth. The stagnant conditions of a standby generator fuel tank could mean that the problem of the diesel bug in your fuel does not become apparent until you most need the generator for an extended period of operation. Short monthly test runs might only create only minor disturbance in the fuel tank, but a longer term run in a live regional outage could see your generator failing and sustaining serious damage.

The fuel polishing technique could also be used to avoid the potential problem of contaminated fuel being delivered by tanker to your main tank during a period of extended mains power outage, such as a regional power outage. One solution may be to deliver the fuel to a holding tank, polish it and test it before releasing it to the main fuel tank(s). The equipment required to polish the diesel is not terribly expensive, it is a technology which has been around for some time in the maritime and transport industry.

I'll certainly be adding this topic to the check list of questions I use when auditing a data centre site for physical security. It is a risk factor that can be avoided.

There is a short video of the IPU system in operation:

Here's another useful blog site on generator issues.

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