AXI has researched and compiled a broad set of specifications and fundamentals regulating the practice of maintaining stored fuel oil. These specifications include regulations by the United States Government Nuclear Regulatory Commission, the not-for-profit Canadian Standards Association, standards declared by major corporations in the fuel oil industry, international standards developed by the ASTM and regulatory codes developed by the NFPA.
Although this document contains the most prominent standards by which to follow, it should not be considered a finite resource of information. New standards are released frequently so the practitioner should engage in a regular plan of research and education in order to maintain a
current knowledge base.
References in this document are made to certain testing standards and are condensed for brevity. In such cases, readers should review the actual long-form article in its entirety in order to obtain a complete understanding of the test and the standards explained.
United States Nuclear Regulatory Commission
Appendix B to ANSI N195-1976 should be used as a basis for a program to ensure the initial and continuing quality of fuel oil as supplemented by the following:
- The oil stored in the fuel-oil supply tank, and the oil to be used for filling or refilling the supply tank, should meet the requirements of Federal Fuel Oil Specification VV-F-800b (April 2, 1975); ASTM D975-77, “Standard Specification for Diesel Fuel Oils;” or the requirements of the diesel-generator manufacturer, if they are more restrictive, as well as the fuel-oil total insolubles level specified in Appendix B to the standard. The “cloud point” should be less than or equal to the 3-hour minimum soak temperature2 or the minimum temperature at which the fuel oil will be maintained during the period of time that it will be stored. If test results for viscosity or for water and sediment for fuel oil contained in the supply tanks exceed the limits specified in the applicable specification, the diesel should be considered inoperable. Fuel oil contained in the supply tank not meeting remaining applicable specification requirements should be replaced in a short period of time (about a week).
- Prior to adding new fuel oil to the supply tanks, onsite samples of the fuel oil should be taken. As a minimum, prior to the addition of new fuel, tests for the following properties should be conducted:
- Specific or API gravity
- Water and sediment
Test results for the latter two tests should not exceed the limits specified in the applicable specification. Analysis of the other properties of the fuel oil listed in the applicable specification should be completed within 2 weeks of the addition.
- The periodic sampling procedure for the fuel oil should be in accordance with ASTM D270-1975, “Standard Method of Sampling Petroleum and Petroleum Products.”
- Accumulated condensate should be removed from storage tanks on a quarterly basis or on a monthly basis when it is suspected or known that the groundwater table is equal to or higher than the bottom of buried storage tanks.
- Day tanks and integral tanks should be checked for water monthly, as a minimum, and after each operation of the diesel where the period of operation was 1 hour or longer. Accumulated water should be removed immediately. If it is suspected that water has entered the suction piping from the day or integral tank, the entire fuel-oil system between the day or integral tank and the injectors should be flushed.
- As a minimum, the fuel oil stored in the supply tanks should be removed, the accumulated sediment removed, and the tanks cleaned at 10-year intervals. To preclude the introduction of surfactants in the fuel system, this cleaning should be accomplished using sodium hypochlorite solutions or their equivalent rather than soap or detergents.
- If an event should occur that would require replenishment of fuel oil without the interruption of operation of the diesel generators, the method of adding fuel oil should be such as to minimize the creation of turbulence of the accumulated residual sediment in the bottom of the supply tank since stirring up this sediment during the addition of acceptable new incoming fuel has the potential of causing the overall quality of the fuel oil in the storage tank to become unacceptable.
Canadian Standards Association
CSA – 7.3 Fuel Supply - Emergency electrical power supply for buildings
- 7.3.1 – A quantity of fuel sufficient for operating the engine under full load for at least 2h shall be maintained on site at all times.
- 7.3.4 – The fuel shall meet the engine manufacturer’s specifications.
CSA – 11.5.5 Visual inspection of fuel (clear and bright test)
- 126.96.36.199 – General – All fuel supplied to the emergency generator set shall be clean and clear and bright as specified in Clause 188.8.131.52. Immediately upon completion of the annual fuel oil inventory maintenance specified in Table 5, the fuel oil shall be tested to verify that it is clear and bright. If the fuel fails the test, the tank shall be flushed to remove built-up sludge and impurities. Note: the purpose of this test is to detect possible water or solid contaminants in diesel fuel by visual inspection. The test method is based on ASTM D 4176.
- 184.108.40.206 – Description – The fuel shall be placed in a transparent bottle or container (see Clause 220.127.116.11) and examined to determine whether it is clear and bright. Samples for the clear and bright test shall be obtained from the bottoms of the storage and day tanks.
- 18.104.22.168 – Equipment – A dry, capped, clear glass bottle or container capable of holding 250 to 1000 ml of liquid shall be used. The bottle or container shall have a clear, undistorted bottom and be thoroughly washed before the test.
- 22.214.171.124 – Procedure – The following procedure shall be followed.
- Wash the fuel sample bottle or container before gathering each sample.
- Let the sample settle for 1 min to remove air bubbles
- Observe the sample against a light background for a clear and bright condition. Swirl the bottle or container to create a vortex (free water and solids tend to collect beneath the vortex).
- 126.96.36.199 – Interpretation of test results – The samples shall be clear and bright. Record the visual clarity as clear and bright or not clear and bright. Record whether particulate matter or water was seen at the bottom of the vortex. Note: The term “clear and bright” has no relation to the natural fuel oil color. Fuel oil color varies from water white, to stray color to amber depending on the processing and/or crude source. Clear and bright fuel has no floating or suspended matter. Brightness is a quality independent of the sample color and refers to the lack of suspended or free water in the sample bright fuel tends to sparkle.
NFPA Codes & Standards
NFPA 20 Standard for the Installation of Stationary Pumps for Fire Protection
8.6.4 Fuel Supply Maintenance states that “tanks shall always be filled by means that will ensure removal of all water and foreign material”
NFPA 25 Standards for the Inspection, Testing Maintenance of Water-Based Fire Protection Systems
Appendix B calls for a maintenance schedule to check to make sure diesel systems are free of water.
NFPA 30 Flammable and Combustible Liquids Code (2008)
21.8.8 Requires tank owners to establish a procedure for checking and removing remaining water from the bottom of the storage tanks.
NFPA 110 Standard for Emergency Power and Standby Power Systems (2010)
- 188.8.131.52 All fuel tanks and systems shall be installed and maintained in accordance with NFPA 30, Flammable and Combustible Liquids Code; NFPA 37, Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines; NFPA 54, National Fuel Gas Code; and NFPA 58, Liquefied Petroelm Gas Code.
- 184.108.40.206* Fuel system design shall provide for a supply of clean fuel to the prime mover.
- Annex 220.127.116.11 - Commercial distillate fuel oils used in modern diesel engines are subject to various detrimental effects. The origin of the crude oil, refinement processing techniques, time of year, and geographical consumption location all aid in the determination of fuel blend formulas. Sulfur, naturally occurring gums, waxes, soluble metallic soaps, water, dirt, and temperature all begin to degrade fuel as it is handled and stores. These effects begin at the time of fuel refinement and continue until consumption.
- Proper fuel storage is critical to engine start-up, efficiency and longevity. Storage tanks should be kept water-free and have provisions for drainage on a scheduled basis. Water can contribute to steel tank corrosion and the potential development of microbiological growth where fuel and water interface. Copper and its alloys, along with zinc or zinc coatings, should be avoided in fuel-handling systems. These elements can react with fuel to form certain gels or organic acids, resulting in clogging of filters or further system corrosion. Stable storage temperatures are conducive to fuel health. Tanks that are aboveground and subject to extreme daily temperature variations cause fuel to degrade more rapidly. This is further exacerbated with large aboveground tanks that are less than full. Airspace allows for condensation that can further add to the contaminant levels. Reflective exterior tank coatings reduce but do not eliminate the solar heating effect. Scheduled fuel maintenance and testing help to reduce or nearly eliminate fuel contamination. Fuel maintenance filtration can remove contaminants and water and return fuel to conditions where it will provide reliability and efficiency for standby generators when called upon in emergency conditions. Fuel maintenance and testing should begin the day of installation and first fill to establish a benchmark guideline for further comparison. Fuel monitoring and testing services are available nationwide from many companies.
- 18.104.22.168 Tanks shall be sized so that the fuel is consumed within the storage life, or provision shall be made to replace stale fuel with clean fuel.
- 8.3.8 A fuel quality test shall be performed at least annually using tests approved by ASTM international standards.
Standards from the Fuel Industry
“Diesel fuel can be stored for 6 months to a year…longer periods can be accomplished thorugh use of periodic filtrations and addition of fuel stabilizers and biocides” – Exxon
“Typical issues [with diesel fuel] are a result of water bottoms accumulating over a period of time in the storage tank that can lead to filter plugging and equipment corrosion along with a large amount of tank bottom material. The entire industry has noticed this increase in filter plugging tencency. The filter can only handle a certain amount of sediments and only for a certain period of time” – Shell, exerpt from “Water Management in Storage Tanks”
“As diesel gets older, a fine sediment and gum forms in the diesel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvationa nd the engine stopping…” – BP Fuel News, Feb. 2002
“Those who store diesel fuel for a prolonged period i.e., one year or longer, can take steps to maintain fuel integrity…add an appropriate stabilizer, use a fuel quality management service to regularly test the fuel, and as necessary, polish it…install a dedicated fuel quality management system that automatically tests and purifies the fuel and injects fresh stabilizer.” – Chevron
American Petroleum Institute
Proper Handling Definition
“Proper handling” entails documenting…fuel quality as product is transported throughout the supply chain to maintain the original product specification.
Manual of Petroleum Measurement Standards
Chapter 10.6 Standard Test Method for Water and Sediment in Fuel Oils by the Centrifuge Method (ANSI/ASTM D1796)
Describes the laboratory determination of water and sediment in fuel oils in the range of 0 to 30% volume by means of the centrifuge procedure.
In-Situ and On-Site Biodegradation of Refined and Fuel Oils
This report reviews more than 200 technical articles published between 1988 and 1991 in the area of on-site and in-situ bioremediation of petroleum hydrocarbons. It focuses specifically on current field and laboratory research related to petroleum hydrocarbon biodegradation including biodegradation of crude oil and solvents.
Interior Lining and Periodic Inspection of Underground Storage Tanks
Methods for…removing sediment, and cleaning interior surfaces of steel and fiberglass tanks…
Tank Inspection, Repair, Alteration and Reconstruction
- The minimum requirements for maintaining the integrity of storage tanks.
- Reasons for inspection and causes of deterioration of storage tanks
- Tools and equipment for tank inspection
- Evaluation of tank bottom conditions
Guidelines and Procedures for Entering and Cleaning Petroleum Storage Tanks
This RP provides guidance and information on the specific aspects of tank cleaning, in order to assist employers (owners/operators and contractors) to conduct safe tank cleaning operations in accordance with the requirements of Std 2015.
ASTM International D975, Section X2. Storage and Thermal Stability of Diesel Fuels
- X2.6.1 A plan for monitoring the quality of bulk fuel during prolonged storage is an integral part of a successful program.
- X2.6.2 Stored fuel should be periodically sampled and its quality assessed.
- X2.7.1 Contamination levels in fuel can be reduced by storage in tanks kept free of water, and tankage should have provisions for water draining on a scheduled basis.
ASTM Fuel Oil Rating (Diesel)
Rating................. Fuel Description
A-2................. Refinery fresh fuel
A-4................. Watch closely – aging has begun
A-5................. Advanced aging and oxidation
A-6................. Badly aged – not recommended
A-7................. Severe aging – do not use
There are four simple steps that need to be put in place to assure compliance to the above requirement of clean fuel for the prime mover; (1) have your fuel tested annually, (2) control microbial contamination, (3) treat the fuel for stability, (4) remove water and sediment regularly.
1. Two (2) fuel samples need to be drawn annually. One from dead bottom for visual inspection for free water and debris. The second sample from the supply line to the prime mover and sent to an accredited laboratory for testing for existing particulate and stability using ASTM Approved Test Methods.
2. A biocide introduced to the fuel, per manufacturer recommendation, will control microbial growth within the diesel fuel storage tank. Care must be taken to select a biocide that is registered with proper Federal and State agencies.
3. There are a variety of chemical additives (treatments) that increase diesel fuel stability, are self-dispersing and do not require costly injection systems for introduction to the stored fuel.
4. Removing water and sediment regularly can be accomplished by filtering of the stored fuel through a series of water separators and media filters. Portable equipment can be contracted or a stand alone, automated filtration system can be permanently installed directly to the diesel fuel storage tank. When installing a permanent system, NFPA Equipment Requirements, Labeled and Listed apply.