Since around 2003, the International Fire Code (IFC), section 5704 – Storage, has required that ALL above-ground storage tanks, regardless of capacity, be provided with an approved means or method of overfill prevention. In this article we will look at what the code prescribes as the flammable liquid tank’s safe upper limit and the requirement for the “over-fill” prevention. Before we get started, for those of you who only wish to meet OSHA compliance minimums, I will state this up front…OSHA does require over-fill protection, BUT ONLY when the storage tank is located INSIDE a building.
1910.106(b)(4)(iv)(h) Tanks inside buildings shall be equipped with a device, or other means shall be provided, to prevent overflow into the building.
As for NFPA 30 – FLAMMABLE AND COMBUSTIBLE LIQUIDS CODE, in 2008 the code was revised to require overfill prevention requirements ONLY on tanks larger than 1320 gallon capacity. ( See NFPA 30, Chapter 21 Storage of Liquids in Tanks — Requirements for All Storage Tanks, with a referal to API 2350, Overfill Protection for Storage Tanks in Petroleum Facilities for additional guidance. NFPA 30 goes even further in its requirements and should be the RAGAGEP of choice for those seeking world-class type design and protection.
First lets establish the IFC/State Fire Code requirements:
(emphasis added by me)
CHAPTER 57 FLAMMABLE AND COMBUSTIBLE LIQUIDS
SECTION 5704 STORAGE
5704.2.9 Above-ground tanks
5704.2.9.7 Additional requirements for protected above-ground tanks
5704.2.9.7.5 Overfill prevention
Protected aboveground tanks shall NOT be filled in excess of 95 percent of their capacity. An overfill prevention system shall be provided for EACH tank. During tank-filling operations, the system shall comply with ONE of the following:
1. The system shall:
1.1. Provide an INDEPENDENT means of NOTIFYING the person filling the tank that the fluid level has reached 90 percent of tank capacity by providing an audible OR visual alarm signal, providing a tank level gauge marked at 90 percent of tank capacity, or other approved means; and
1.2. AUTOMATICALLY SHUT OFF THE FLOW of fuel to the tank when the quantity of liquid in the tank reaches 95 percent of tank capacity. For rigid hose fuel-delivery systems, an APPROVED MEANS shall be provided to empty the fill hose into the tank after the automatic shutoff device is activated.
2. The system shall reduce the flow rate to NOT MORE than 15 gallons per minute (0.95 L/s) so that at the reduced flow rate, the tank will not overfill for 30 minutes, and AUTOMATICALLY SHUT OFF FLOW into the tank so that none of the fittings on the top of the tank are exposed to product because of overfilling.
For those of you wanting to use NFPA as your RAGAGEP…
21.7 Operation of Storage Tanks.
21.7.1 Prevention of Overfilling of Storage Tanks. Facilities with ABOVEGROUND TANKS LARGER THAN 1320 GAL (5000 L) storing CLASS I OR CLASS II LIQUIDS shall establish procedures OR shall provide equipment, OR both, to prevent overfilling of tanks.
21.7.1.1 Facilities with aboveground tanks that receive and transfer Class I liquids from mainline pipelines or marine vessels shall establish AND follow formal written procedures to prevent overfilling of tanks utilizing ONE of the following methods of protection:
(1) Tanks shall be gauged at intervals in accordance with established procedures by personnel CONTINUOUSLY on the premises during product receipt. Acknowledged communication shall be maintained with the supplier so flow can be shut down or diverted in accordance with established procedures.
(2) Tanks shall be equipped with a high-level detection device that is EITHER independent of any gauging equipment OR incorporates a gauging and alarm system that provides electronic self-checking to indicate when the gauging and alarm system HAS FAILED. Alarms shall be located where personnel who are on duty throughout product transfer can arrange for flow stoppage or diversion in accordance with established procedures.
(3) Tanks shall be equipped with an independent high-level detection system that will automatically shut down or divert flow in accordance with established procedures.
21.7.1.2 Alternatives to instrumentation described in 21.7.1.1(2) and 21.7.1.1(3) shall be allowed where approved as affording equivalent protection.
21.7.1.3 Instrumentation systems covered in 21.7.1.1(2) and 21.7.1.1(3) shall be wired FAIL-SAFE, such that valid alarm conditions or system failures create an alarm condition that will notify personnel OR automatically shut down or divert flow.
21.7.1.3.1 WRITTEN INSTRUMENTATION PERFORMANCE PROCEDURES shall be established to define valid alarm conditions and system failures in accordance with API 2350, Overfill Protection for Storage Tanks in Petroleum Facilities.
21.7.1.3.2 System failure shall include but not be limited to the following:
(1) Loss of main electrical power
(2) Electrical break, short circuit, or ground fault in the level detection system circuit or the alarm and signal circuit
(3) Failure or malfunction of the level detection system control equipment or signaling devices
21.7.1.4 FORMAL WRITTEN PROCEDURES required by 21.7.1.1 shall include the following:
(1) Instructions covering methods to check for lineup and receipt of initial delivery to tank designated to receive shipment.
(2) Provision for training and monitoring the performance of operating personnel by supervisors.
(3) Schedules and procedures for inspection and testing of gauging equipment and high-level instrumentation and related systems. Inspection and testing intervals shall be approved but shall not exceed 1 year.
21.7.1.5 An underground tank shall be equipped with overfill prevention equipment that will either alert the transfer operator when the tank is no more than 90 percent full by triggering an audible and visual high-level alarm or automatically shut off the flow of liquid into the tank when the tank is no more than 95 percent full.
21.7.1.5.1 Other methods of overfill protection shall be permitted as approved by the authority having jurisdiction.
21.7.1.6 Shop-fabricated aboveground atmospheric storage tanks, constructed to the recognized standards of 21.4.2.1.1, shall meet the requirements of 21.7.1.6.1 through 21.7.1.6.4 whenever the vertical length from the tank bottom to the top of the fill, normal vent, or emergency vent exceeds 12 ft (3.7 m).
21.7.1.6.1 An approved means shall be provided to notify the tank filling operator of the pending completion of the tank fill operation at the fill connection.
21.7.1.6.2 An approved means shall be provided to stop delivery of liquid to the tank prior to the complete filling of the tank.
21.7.1.6.3 In no case shall these provisions restrict or interfere with the functioning of the normal vent or emergency vent.
21.7.1.6.4 The manufacturer of the tank shall be consulted to determine if reinforcement of the tank is required. If reinforcement is deemed necessary, it shall be done.
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