• If applicable

Posted Sunday, February 2nd, 2020

In our industry it is well known that an engine needs fuel to operate, and clean fuel at that. Just like your vehicle that you fill up to get too and from work, it’s not till you run out of gas that you appreciate the importance of this imperative detail. The same can be said for maintaining the fuel for backup/standby generators.

Power outages in a home can be salvaged by a candle or two while power is down for 10-20 minutes. But for critical buildings and times where extended power outage is apparent, keeping clean fuel in your tank becomes a high priority.

The below is a list to guide you on what we believe the 9 key points are to remember when looking into diesel fuel tanks for standby generators. From choosing the right tank for the job, to ensuring the fuel is clean.


Common fuel tanks for back up generators to ensure compliance now and going forward (especially if they are going inside or close to buildings in high-traffic areas) should ideally be a 4-hour fire rated fuel tank. These are constructed to either sit close by the generator whether it is located inside a building, or in a high foot traffic area, depending on allocated space. In cases where there is lower foot traffic and the generator is outside, a stationary diesel tank can work (such as the DC Series by Fuelchief) however compliance on separation distances and extra items needs to be adhered to.

Power Outage Image


The fuel tank run-time is calculated by the generator fuel consumption measurement at 100% load. This anticipates a worst-case scenario, assuming the potential for the generator to be fully loaded during a power outage. The 100% fuel consumption multiplied by 24 = a 24-hour tank. When selecting a fuel tank size keep in mind that generators don’t normally run at 100% load, so the actual run-time will likely be greater than 24 hours.

Power Outage Image


Local requirements can vary state-to-state and city-to-city for back up generators. In some applications, a specific run-time may be required to adhere to the local requirements. For example, in the health care industry, local requirements (or IL ratings) in some areas dictate that the fuel source for standby generators in critical, life-safety applications should be a minimum of 72 hours. Local requirements in other areas may specify more, or less. In critical situations the SuperVault is the most compliant and reliable tank to use and has been placed in such situations because of its meeting of IL4 and compliance in critical power situations.


When the physical size limit of a standby generator tank / sub-base fuel tank simply isn’t enough, a day-tank could be a viable option. A day-tank functions as the immediate fuel source for the generator, receiving fuel from a larger fuel storage tank. It can be a stand-alone tank mounted in close proximity to the generator, or it could be a sub-base tank with provisions to be used as a day-tank. In either case, a day-tank is typically designed to contain a small amount of fuel which is automatically replenished from the main standby tank. An example of this is in our Christchurch Hospital case study. The two cylindrical tanks based in the basement level of the hospital were the main source of fuel to the day-tanks located up in the roof of the hospital to ensure continued power in the face of an outage.

Fuelchief The importance of an emergency vent on your tank


AS/NZ, WorkSafe and EPA may dictate fuel tank requirements beyond run-time. In Australia and New Zealand, for example, certain regions have adopted additional safety and environmental requirements for fuel tanks, such as: extended tank venting (or additional emergency venting), IL ratings, fire ratings, fuel-spill containment at the fill port, on-site pressure testing, and high fuel level shut-off. These requirements, or similar, are being adopted in other countries around the world such as the US and UK as well. When in question contact your HSNO , Test Certifier or local government for more detail.


Fuel tanks sold in Australia and NZ need to meet certain standards around compliance (you can read more about this in our compliance section) Overseas, in the USA,  stationary generators typically comply with UL Standards (which you can read about here). UL142 is the most common, and the UL requirements cover the construction, performance, and markings of the tank. SwRI 95-03 ie the SuperVault, surpasses UL142 and UL2085 by ensuring the tank is 4-hour fire rated, and in the event of a natural disaster it is the only tank that can be repaired and reused (as all other tanks need to be replaced in entirety). Like UL142, SwRI 95-03 features include emergency venting, fill/withdraw, gauging, secondary containment, and openings for leak-detection monitoring. Like UL2085 standards SwRI 95-03 include the requirements of UL142, without the need to encase the fuel tank in concrete material or additional bunding, as the SwRI 95-03 rating ensures the tank is impact tested, fire tested, and multi-hazard tested. Above and beyond UL2085 tanks which are required to withstand a certain resistance to fire, vehicle impact, and projectiles, the SuperVault surpasses all effortlessly.


Standard diesel fuel comes in two grades: standard and winter. The local environment and climate is an important factor to determine the type of fuel used for a standby generator. Winter is more resistant to gelling in colder temperatures and can be used for colder climates (where if not used diesel gelling can occur as per picture). The energy output of standard diesel is slightly higher than winter, so it is preferred for warmer climates where the risk of gelling is lower. These fuel grades are often blended to provide the benefits of both, and to provide the suitable viscosity for local weather conditions. Fuel suppliers are usually familiar with the grade (or blend) necessary for the local climate.


Diesel fuel typically starts to deteriorate and form solids within six months if not maintained. For preventative maintenance, fuel treatment is available to extend the life and ensure the fuel is up to par and ready to perform in time of need. Routine maintenance and treatment helps fight micro-organism growth (such as diesel bug shown in picture), prevents gelling and stabilises the fuel. Further, to counter fuel issues, fuel polishing can be performed which removes water and sediment from the tank and filters contaminants. This is an economical, earth-friendly alternative to replacing fuel, as all of the fuel is recycled with no loss of product.


Fuel quality issues typically don’t show up until the generator is running under load during a power outage – when the reliability of your standby system is most important. Before fuel issues arise, quality and contamination tests can be performed to check for contaminants as well as the overall fuel quality. Contamination sampling can check for water contamination, bottom sediment, gel, flash, and cloud points. This testing that takes place needs to comply with ASTM Standards. Find out more about fuel quality testing via your local government or fuel supplier.


If you have questions about fuel tank selection, requirements, or if you need any information regarding routine maintenance for your fuel supply, please don’t hesitate to contact Fuelchief.


(Sourced: Clifford Power Systems)


Blog article by Praneel Lal