Compliance News: NFPA 110-2013 Edition Addresses Generator Fuel Oil Management

By David L. Stymiest, PE, CHFM, CHSP, FASHE



The 2013 edition of NFPA 110 was recently released by the NFPA Standards Council. Chief among the changes in this edition were several changes, including informational Annex recommendations, intended to improve emergency power supply system (EPSS) reliability through better fuel oil management processes. The excerpts below are only partial excerpts, and readers should review the full text of the updated standard, which is available at www.nfpa.org/110. In the discussion below, note that all Annex language is not mandatory, rather it is advisory only and contains recommendations for user consideration.

Paragraph 7.9.1.3 was modified to stipulate that “tanks shall be sized so that the fuel is consumed within the storage life, or provisions shall be made to remediate fuel that is stale or contaminated or to replace stale or contaminated fuel with clean fuel.” Although these are not in NFPA 110, some popular remediation techniques incorporate filtering of the stored fuel through a series of water separators and media filters, periodic centrifuge cleaning/polishing with high pressure tank agitation and/or mechanical tank cleaning with auxiliary filtration.


Chapter 8 (Routine Maintenance and Operational Testing) applies to both new and existing systems and equipment. Paragraph 8.3.8 was modified to clarify that “A fuel quality test shall be performed at least annually using appropriate ASTM standards.” Chapter 2 (Referenced Publications) does not list appropriate ASTM standards because they are not specifically referenced in the main body of the standard. Since there is no ASTM standard specification for natural or synthetic gas, the NFPA 110 Annex indicates that “industry generally uses pipeline specifications for natural gas quality.” However, the NFPA 110 Annex does list the following ASTM standards for fuel oil systems because they are specifically discussed in the Annex:
          ASTM D 975, Standard Specification for Diesel Fuel Oils
          ASTM D 1835, Standard Specification for Liquefied Petroleum (LP) Gases

Because fuel oil contaminants (including water) in fuel oil storage tanks can be found in the bottoms of storage tanks, new Annex language now recommends that “special attention should be paid to sampling the bottom of the storage tank to verify that the stored fuel is as clean and dry as practicable and that water, sediment, or microbial growth on the tank bottom is minimized.” The new Annex language also states that ASTM D 975 contains test methods for existing diesel fuel.

As a caution – excessive water or other contaminants in a fuel oil storage tank or elsewhere within the fuel oil system can cause emergency generators to fail. This and other fuel oil system issues have been recognized as the second leading cause of EPSS failures. Starting system issues are recognized as the primary cause of EPSS failures. The NFPA 110 recommendations on sampling can help to minimize the potential for this fuel system-related failure mode.

Annex paragraph A.7.9.1.2 contains more recommendations concerning water contamination-related failures and management techniques – “Fuel storage tanks should be kept as dry as possible and have provisions for water drainage on a regular basis. The presence of water can lead to microbiological contamination and growth, which in turn can lead to general or pitting corrosion of steel tanks and components, possibly resulting in filter plugging, operational issues, or a hydrocarbon release to the environment.”

Annex paragraph A.7.9.1.2 also discusses the importance of broader inspection techniques – “Regularly scheduled surveillance of the fuel allows the operator(s) to evaluate the condition of the fuel and make important decisions regarding the quality of the fuel dedicated to reliable operation of the prime mover.” Although it is not a requirement, Annex Figure A.8.3.1(a) Suggested Maintenance Schedule for EPSSs, has recommended weekly checks for water in the Level 1 EPSS fuel oil systems for several editions.

Annex paragraph A.5.1.1(1) contains explanatory material and recommendations regarding EPSS diesel fuel. It now states that the grade of diesel fuel used in an EPSS diesel engine “should be based on recommendations from the diesel engine manufacturer and ASTM D 975.”

Annex paragraph A.5.1.1(1) also discusses special precautions recommended for outside storage tanks – “If diesel fuel is stored outside for long-term storage, it may be necessary to use a winter or arctic grade of diesel fuel or to take precautions such as insulating and heat-tracing fuel tanks and lines to ensure that fuel will flow to the prime mover under the coldest possible conditions.”

The NFPA 110-2013 Annex also goes on to warn against the use of certain biodiesel fuels in EPSS applications, such as in A.5.1.1(1) – “Where possible, the purchaser of fuel for the prime mover should specify a diesel fuel that does not contain biodiesel, which can accelerate the degradation of the diesel fuel if stored longer than 6 months.” Further related discussion is in Annex paragraph A.5.5.3 – “biodiesel blends up to B5 (ASTM D 975, Standard Specification for Diesel Fuel Oils) have much shorter shelf lives than conventional diesel fuel [ultra-low sulfur diesel (ULSD)] and can accelerate degradation processes, endangering the entire diesel fuel supply.”

Annex paragraph A.5.5.3 also contains recommendations regarding fuel oil storage tank sizing – “Consideration should be given to sizing tanks in order to meet minimum fuel supplier delivery requirements, particularly for small tanks. Consideration also should be given to oversizing tanks.”

Annex paragraph A.5.5.3 also contains recommendations and explanatory material regarding fuel storage management – “Where fuel is stored for extended periods of time (e.g., more than 12 months), it is recommended that fuels be periodically pumped out and used in other services and replaced with fresh fuel.”

The NFPA 110-2013 Annex also recommends additional fuel oil system management techniques in paragraph A.7.9.1.2 – “To optimize the long-term storage of fuels for prime movers, the fuel tanks should be kept cool and dry, and the tank as full as possible. Tanks that are subject to temperature variations can experience accelerated fuel degradation, especially if the tanks are outside and above ground or close to an extreme heat source if stored inside a structure. The more constant and cooler the tank temperatures, the less likely temperature-related fuel degradation will occur.”


Annex paragraph A.7.9.1.2 also makes recommendations concerning the air space above the fuel oil within the storage tank, which can be influenced by the size of the tank, the rate of fuel oil usage, the emergency management requirements, the age of the fuel, etc. – “Tank ullage (air space) should be kept to a minimum. Excess air space allows for warm, humid air to enter the tank and condense moisture during the cool evening. Also, prolonged exposure to ambient air, which is 20 percent oxygen, can facilitate oxidative degradation of the fuel.”

And finally, in Annex paragraph A.7.9.1.2, NFPA 110 advises that “Fuel maintenance and testing should begin the day of installation and first fill in order to establish a benchmark guideline for future comparison. Laboratory testing services should always be sought from a qualified or certified petroleum laboratory.”

NFPA Disclaimer: Although the author is Chair of the NFPA Technical Committee on Emergency Power Supplies, which is responsible for NFPA 110 and 111, the views and opinions expressed in this message are purely those of the author and shall not be considered the official position of NFPA or any of its Technical Committees and shall not be considered to be, nor be relied upon as, a Formal Interpretation. Readers are encouraged to refer to the entire text of all referenced documents. NFPA members can obtain NFPA staff interpretations at www.nfpa.org.