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what is fuel polishing in a generator?

Fuel polishing is the very fine filtration of diesel fuel to remove impurities like dirt and water, you’ll find everything you need to know. Start with BISON.

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As a proprietor, manager, designer, or installer of diesel generators, you may be familiar with the concept of diesel fuel polishing. But why is this topic gaining traction now? The answer lies in the alterations made to diesel fuel composition to adhere to air emissions regulations.

In most cases, diesel fuel doesn’t necessitate fuel polishing. It’s typically used up within a few weeks or months after it departs the refinery. Its storage duration in the generator fuel tank is relatively brief. For truck fuel, routine inspections and maintenance to eliminate water at the tank bottom can prevent biological problems and corrosion at the tank base.

Remember, understanding these factors is critical to efficiently managing your OEM BISON generator.

diesel generator polishing systems and filters

What is generator fuel polishing?

Fuel polishing is a technical process used to clean hydrocarbon and oil fuels that remain in storage tanks for future use. The stored diesel fuel undergoes a filtration process where contaminants are removed without fuel additives.

Contaminants can include sediment, microbial growth, and bacteria whose presence reduces the efficiency of generators.

The fuel polishing process also helps reduce the potential build-up of sludge, which typically occurs at the bottom of the diesel fuel tank.

Why is diesel fuel required to be polished?

Generators use different types of fuel. People who use diesel fuel often need to store it for long periods. Fuel storage tank can sometimes hold diesel fuel for up to ten years.

However, diesel fuel can begin to accumulate impurities within six months of storage. For example, it collects particles that turn into grease over time.

As diesel fuel is used, it can also draw foreign dirt into the tank. Dirt settles at the bottom of the tank. Therefore, diesel generators must be fuel cleaning.

Diesel fuel generators should have regular fuel quality tests followed by fuel polishing. Fuel polishing is crucial to this process, resulting in improved fuel quality and uninterrupted fuel supply.

tank bottom samples

When should fuel be polished?

Diesel fuel begins to deteriorate between 3 to 6 months post-refinement. Consequently, it is essential to consider a fuel polishing strategy. Here are three common strategies:

Annual Fuel Test with Contingency Polishing: Many facilities mandate annual testing for their emergency generator fuel. If a test identifies an issue, they’ll arrange for fuel polishing of the generator tank. However, this approach carries a risk of shutdown or failure. A more effective contingency plan involves monitoring fuel test parameters for degradation and arranging for fuel polishing based on this analysis, prior to failing the test.

Annual Planned Fuel Polishing and Testing: Some facilities allocate a budget for yearly fuel polishing and testing services to ensure consistent fuel quality. This strategy prevents most issues, but if a fuel tank has water or bio-contamination problems that can escalate upon reaching a critical level, the frequency may not be sufficient.

Installed Automatic Fuel Polishing Equipment: Most modern critical facilities have implemented automatic fuel polishing systems to guarantee ongoing fuel quality. These systems automatically initiate and cycle fuel in a tank, typically enabling one tank volume turnover per week.

Remember, maintaining high-quality fuel is crucial for your operations, so choose the strategy that best fits your needs.

four fuel samples

Benefits of diesel generator fuel polishing

New diesel fuel should be bright pink and completely transparent. As the fuel ages and begins to degrade, the color darkens, and visible particles can be seen.

Here are some of the benefits of diesel generator fuel polishing:

  • Improved system performance
  • Reduced wet stacking in diesel engines.
  • Environmental compliance
  • Less downtime
  • Increase equipment life and reliability

What is a generator fuel polishing system?

Generator fuel polishing system is a device that uses a combination of a fuel filtration system to clean the fuel. Some generators are equipped with a fuel polishing system. When this happens, fuel polishing can be done without needing an outside fuel polishing service.

If a generator does not have its fuel polisher, an engineer can be deployed from a generator maintenance service provider that offers a fuel polishing service.

Today, industrial mass backup power systems come with connected fuel polishing systems, which can operate automatically. The flow rate can be 25,000 liters of fuel polished within an hour.

Fuel polishing is an essential part of diesel generator maintenance. It should be held at least once a year.

how a fuel polishing system works

How a Fuel Polishing System Works

Unchecked fuel tanks are likely to accumulate harmful sludge at the bottom, which can cause problems for various parts of your generator as it circulates through the system. Natural processes lead to the accumulation of water and bacteria over time, contaminating your fuel and making it unsuitable for use. The preventive measure for this is to purify the diesel with a fuel polishing system.

Some generators come equipped with an integrated fuel polisher and gauge. This feature ensures automatic cycling and cleaning of fuel. Therefore, there’s no need to wait for a technician, you save on maintenance costs, and it further minimizes the risk of fuel contamination. Many of our clients find this feature highly beneficial, as we can install fuel polishers on both new and existing generators, depending on the site conditions.

For those who do not have a built-in fuel polisher, BISON China generator gactory provides professional fuel polishing services that can reach your location and clean your fuel safely without harming the environment.

How is fuel polishing monitored?

The fuel polishing controller monitors the condition of the equipment. The controller can connect to a remote building management system or cloud-based monitoring. Here are the items that are monitored:

a) Dirty filters

Filters are monitored by differential pressure from the inlet to the outlet. When the rated differential pressure is sensed instead of the alarm being activated, it indicates that filter replacement is required.

b) Water in coalescing filters

Water in the coalescer separates from the fuel and settles at the bottom of the filter. As water accumulates, the level rises to the point where the water sensor is triggered, and an alarm is triggered. The water can be drained, and the alarm will reset.

c) Pump flow

A flow sensor proves that the fuel pump is working properly. If not, the controller will show a pump alarm for troubleshooting.

d) Leak detection

The pump and filter assembly must include a containment base in case of fuel leaks and facilitate filter changes. A leak sensor will trigger an alarm on the control panel and stop pump operation until the problem is fixed.

bison's fuel polishing service

Dirt in Diesel Fuel

As diesel fuel ages, particulates tend to precipitate out of the solution. If you’ve ever handled aged diesel, you’d notice a gritty texture. When observed in a glass container, this older fuel appears murky compared to the clean, vibrant appearance of fresh fuel.

Operational engines naturally draw in dirt into their fuel supply. An excess of this can lead to premature filter blockages and potential engine failures. Tiny dirt particles that bypass the fuel filter can cause significant wear on engine components, especially in newer models equipped with high-pressure fuel rails.

Over time, dirt eventually settles as sediment at the bottom of tanks. Unfortunately, there’s no efficient method to eliminate this sediment. As it accumulates, it necessitates expensive tank cleaning procedures and temporary decommissions engines.

Fuel Polishing is an effective solution to this issue. It efficiently removes dirt from stored fuel, thereby preventing the aforementioned problems. Invest in fuel polishing to maintain the quality of your stored fuel and the longevity of your engines.

Diesel fuel contamination

Generator engines can be used regularly and operated correctly and to specification. However, inside the fuel tank, out of sight, free and adsorbed water is gradually accumulating by condensation and even fuel delivery with high water absorption. As evening temperatures drop, water condenses out of the fuel and builds up inside the tank.

If water is on the bottom of the storage tank, the filter clogs bacteria colonies, and fungi will grow at the fuel/water interface. The product of these colonies is acidic sludge.

When the fuel/water interface becomes high enough to reach the engine’s fuel supply tube, which may be inches above the bottom of the tank, microbes that clog the filter will be drawn into the fuel system and stop the engine.

99% of all fuel pollutants, Including water, are heavier than fuel and will be found at the bottom of the storage tank. Drain the water from the bottom of the tank, and the microorganisms will die.

It is, therefore, essential that the intake supply tubes of the fuel polishing system are located at the bottom of the storage tank. Failure to do so may result in an unexpected engine shutdown.

microbes in diesel fuel

Microbes in diesel fuel

Virtually all diesel fuel contains some moisture. Moisture accumulates in diesel tanks as condensate droplets on exposed tank surfaces, as dissolved water in the fuel, and as the water layer beneath the fuel microbes depends on this water for growth.

In addition, microbes rely on organic and inorganic molecules as fuel for nutrition. Consequently, some species attack the fuel directly, growing at the expense of hydrocarbon and non-hydrocarbon fuel components. Biodegradation of fuel, in support of microbial growth, directly affects pollution.

Change color, the heat of combustion, pour point, cloud point, detergent and anticorrosive properties as microbes selectively attack fuel components. Sulfur-containing molecules are metabolized by a series of species, ultimately producing high concentrations of hydrogen sulfide.

In addition to making new cells, many microbes produce metabolites that promote further invasion. Surfactants facilitate the elution of the fuel, resulting in the formation of a cloudy, inverted emulsion layer above the fuel/water interface. Polysaccharide slimes create microenvironments where mixed populations of bacteria and fungi carry out biodegradation reactions leading to single degradation.

The slime also acts as a barrier, protecting the microbes from the preservatives. Various organic acids (primarily 2-4 carbon atoms) are also produced as by-products of bacterial and fungal growth.

Water in diesel fuel

Water can enter fuel storage tanks from:

  • Rainwater seeping over tank fittings
  • Water in delivered fuel
  • Water from moisture in the air

Water is the most common source of moisture in the air. Fuel tanks are vented. When the fuel is delivered to the tank, the air escapes. When fuel is drained, air enters the tank to fill the void. Any moisture in the air will condense in the relatively cool space inside the tank.

As the temperature rises during the day, the fuel expands, pushing the air out of the tank. The fuel condenses as the temperature drops at night and air enters the tank. This is called diurnal breathing. This can be a significant cause of water entering the tank.

Water is denser than fuel, so inside the tank, it slowly settles to the bottom, forming a layer of water. This layer of water causes significant problems.

The water-fuel interface is an environment where biogrowth can initiate and thrive. This can cause quality test failures, and extreme algae growth and clogging of engine filters can lead to failure.

The water layer can be corrosive that attacks the steel tank bottom. Steel tanks now include warnings about this problem. Water in the fuel can be drawn into the fuel system, where it can cause failure and wear.

Fuel polishing removes water from stored fuel and prevents all these problems.

fuel polishing in generator FAQ

In general, fuel polishing should be done at least once a year. Staff in power backup should routinely check how long diesel fuel has been stored. This practice helps in increasing the reliability of generators.

Diesel fuel, upon delivery, generally begins to deteriorate within a six-month timeframe. The degradation process can be primarily attributed to four key factors: Dirt, Water, and Bio-Growth.

  • Dirt: Accumulation of particulates can affect the performance of the fuel.
  • Water: Moisture contamination can lead to issues like bacterial growth.
  • Bio-Growth: Microbial activity can cause the fuel to break down over time.

Understanding these factors is crucial for maintaining the integrity of your diesel fuel. Stay informed and ensure the longevity and efficiency of your fuel supply.

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