High Pressure Storage in Cylindrical Vessels (Bullets)
Site Location and Spacing
Minimum spacing requirements for cylindrical storage vessels shall be in accordance with API Std 2508 and API Std 2510 as applicable. On above grade installations, the major axis of the vessel shall be pointed away from heavily populated areas, vital or valuable equipment, or large-volume flammable liquid storage, whether located in plant or on neighboring property. It is preferred that above grade vessels be located
downgrade and downwind from ignition sources and arranged to prevent any possible flow of flammable liquids into the vessel area. Grade the area and provide drainage so that liquids will not collect adjacent to or under the cylindrical vessels. In refineries, for maximum protection against fire exposure, either increase the minimum distance requirements given in API Std 2508 and API Std 2510 by 100 percent or provide
special protection. Do not locate storage vessels within the same diked enclosure as atmospheric flammable liquid storage.
Recommended distances for cylindrical storage vessels from other refinery facilities are as follows:
a. From occupied buildings, process units, and continuous ignition sources such as process unit heaters or flares: 75 m.
b. From atmospheric flammable liquid storage: 30 m. [Exception: The recommended distance from atmospheric storage tanks of less than 2385 m3 capacity is 15 m.]
Special fire protection shall be provided in refinery installations by fixed water spray, vapor depressuring, or fire resistant insulation as required in the Fire Protection Systems standard.
Underground Storage Tanks | Safety Considerations for Plant Layout Levels
Underground Storage Tanks
Underground storage tanks shall be limited to fuel tanks associated with fuel dispensing facilities. The following standards shall be used where applicable for locating and siting underground storage tanks:
a. API Recommended Practice 1615 (1996), “Installation of Underground Petroleum Storage Systems”
b. PEI RPI100-97 (1997), “Recommended Practices for Installation of Underground Liquid Storage Systems,”
c. API 1631 “Interior Lining of Underground Storage Tanks,”
d. API Standard 2610 (1994), “Design, Construction, Operation, Maintenaince, and Inspection of Terminal & Tank Facilities,
NFPA 30 (1996), Flammable and Combustible Liquids Code.”
Refrigerated and Cryogenic Storage
Refrigerated tanks are for low-temperature storage of LP-gas, ethylene or other hydrocarbons above-101°C.
Refrigerated storage tanks shall be separately diked and spaced a minimum of 75 m from process equipment. Locate downwind and down grade from ignition sources.
Ethylene Storage
The layout and spacing of ethylene tanks shall be generally in accordance with NFPA 59A, Chapter 2 for LNG tankage. Individual impoundment dikes shall be constructed for each tank. Drains from diked areas shall overflow to the contaminated runoff sewer. Access shall be provided on three sides of all impounded areas for the application of hose streams for cooling. Cryogenic service tanks at temperatures below -101 °C shall be installed to meet applicable requirements of NFPA 59A.