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What Is a Diesel Tank Breather and Why Is It Important?

March 22, 2022

Everything You Need to Know About Diesel Tank Breathers – and Why You Need Them

Fuel represents one of the highest operational costs for many businesses, with fuel stores representing millions of dollars. Businesses that rely on fuel being readily available need to be sure that it’s accessible and ready for use. They also need to be certain that fuel stores are safe and clean.

From the time fuel is delivered to a worksite, through its transfer and storage, to the time it is consumed by a vehicle or stationary machine, it is crucial that the condition of the fuel and the tanks containing it are protected. Dirty fuel and damaged tanks lead to costly equipment downtime and introduce a significant risk of environmental and safety incidents.

There are several steps a business can take to ensure the safety and cleanliness of fuel stores; these range from fuel sampling, scrubbing, and stock rotation to the regular maintenance of fuel storage tanks. Regardless whether you are trying to maintain a bulk fuel storage tank or tank farm, or the diesel tank on a single piece of mobile equipment, there is a lot of value in having high quality filtered tank breathers installed.

Why do fuel tanks need to be vented?

Whether used for bulk fuel storage or on-board fuel tanks, all fuel tanks are prone to expansion and contraction as the volume of fuel within them changes. This is predominantly due to two factors:

  1. Environmental – When diesel and other fuels get warmer, they expand and take up a greater volume. This is totally normal. During the day, the sun warms up fuel farms, diesel storage tanks, fuel tanks on vehicles, and the fuel contained within them. Because of the temperature increase, the fuel expands. During the evening, ambient temperatures drop, and the same amount of fuel has a lower volume.
  2. Fuel is added and consumed – In industrial applications such as mine refuelling and other heavy industries, mobile plants utilise a significant amount of fuel. Whilst the machines are working, fuel is being consumed, and less fuel remains in the tank over time. During refuelling, large amounts of fuel get transferred into tanks at high flow rates. Large amounts of fuel entering and exiting the tank quickly is even more of a factor when it comes to bulk fuel installations.
diesel tank breather

Tank venting allows air to move into and out of a fuel tank and equalise with the pressure outside the tank. If air cannot exit a fuel tank quickly enough as it is being filled, then pressure will build up inside the tank, potentially leading to tank damage, spills, and sprays. Suppose air cannot enter a fuel tank quickly enough when fuel is consumed or dispensed from it. In that case, the opposite occurs, and a vacuum is created inside the tank. Pressure build-up, vacuum, and repeatedly exposing a tank to both leads to tank degradation, including ballooning, splits, and major tank ruptures. Appropriate tank venting solutions allow for air to enter or be exhausted from the tank at a sufficient rate to avoid excessive tank pressurisation. Regardless whether they are being used for bulk fuel storage or they are located on a vehicle, diesel fuel tanks require a tank vent or tank breather, potentially both, for optimum equipment safety and performance.

What is a diesel fuel tank breather?

diesel fuel tank breather is a valve apparatus that is connected to a fuel tank vent, which enables the tank to ‘breathe’. It allows for the optimum intake of air as fuel is released from the tank, and expulsion of air as fuel is deposited into the tank (or expands within the tank). An appropriately matched fuel tank breather is able to exhaust air at the maximum rate fuel is expected to be deposited into the tank, avoiding tank pressurisation. It will also allow for air to be drawn into the fuel tank at the maximum rate the fuel is expected to be consumed or dispensed from the tank, avoiding vacuum. Some diesel fuel tank breathers also filter incoming air, contributing to fuel cleanliness.

Some best practices for a diesel fuel tank breather to work optimally and safely include:

  • all breather hoses installed in such a way as to avoid kinks and pinch points
  • hose installation avoids the build-up of debris such as dirt / mud / ore (such as a U-bend)
  • the system is regularly inspected and maintained to ensure filters are replaced before they become clogged, and that all hardware and hoses are in good working order, not blocked or obstructed
  • exhaust air (containing hydrocarbon fumes) should be directed away from electrical and hot engine components, preferably to ground
  • incoming air should be as clean as possible (sometimes a tank breather can be installed remotely from the fuel tank to achieve this)
  • excessive breather hose length should also be avoided, because this in itself can contribute to the build-up of pressure / vacuum

Are there different types of fuel tank vents and fuel tank breathers?

There are several different types of vent valves and breathers for fuel tank applications, including:

  • Unfiltered tank vents, which are free-to-air, may incorporate functionality for a traditional auto shut-off diesel refuelling system, and can be connected with a filter canister to maintain fuel cleanliness to the equipment OEM specifications
  • Filtered tank vents, available in differing grades to prevent the introduction of large dirt, water, and dust particles into the fuel tank and the fluid stream
  • Fine-filtered tank vents, which are designed to exclude particulate contaminants greater than 3 microns in size. This is mandatory for many modern diesel engines due to the very small internal tolerances
  • Fine-filtered remote fuel tank breathers, which can allow for very high refuelling rates, fluid dispensing rates, and only filter incoming air (to maximise the working life and efficacy of filters)
  • Specialist tank overfill prevention and tank safety products such as vented level sensors, which trigger refuelling to stop at the optimum ullage with zero pressure build-up in the tank. Anti-spill rollover protection and pressure relief valves may also be incorporated

There are a wide variety of tank breathers and fuel tank vents produced by different manufacturers – in terms of, for example, the flow rate capacity that can be accommodated, the mechanism of action, and the level of filtration available, among other things. Therefore, it is important to consider these factors when selecting the most appropriate tank breather for each application.

While it is necessary to ensure the fuel tank breather can accommodate the flow rate, due consideration must be given to the installation of another safety mechanism, in the form of a tank overfill protection system. Particularly with refuelling systems designed for high flow bulk fluid transfers. When tank overfill occurs, liquid flows out through the tank vent and breather. Fuel spills occur, pressurisation can cause fuel tanks to rupture, and diesel sprays onto hot engine components and electrical systems can cause fires. A primary tank overfill protection solution such as Banlaw FillSafeTM effectively mitigates the risks associated with tank overfill and may even enhance productivity!

Contact Banlaw today for assistance in selecting the correct diesel tank vents and remote tank breather assemblies for your fleet, fuel farm or bulk fluid storage tanks.

For more information on how Banlaw can help your business improve fuel storage, cleanliness, fluid transfer safety, and system maintenance capabilities, contact Banlaw today. Click here for our International contact details, or to connect with our Australian fuelling system specialists.