API Publ 2510A:2010 pdf download

API Publ 2510A:2010 pdf download.Fire-Protection Considerations for the Design and Operation of
Liquefied Petroleum Gas (LPG) Storage Facilities.
2.9.4 VAPOR SPACE OXYGEN CONCENTRATION
Provisions for drawing gas samples from the vapor space br laboratory analysis of the oxygen concentration should be provided. Sec A. 1.2 in API Standard 2510 for general requirements for sample connections. Fixed oxygen analyzers are usually not needed. Information on oxygen concentration can be used to determine whether it is safe to vent the vessel vapor space to a flare system.
2.9.5 TEST INSTRUMENTS AND ALARMS
Critical instruments and alarms should be designed and installed to permit on-stream testing and repair of all components in the instrumentlalarm loop.
2.10 Relief Systems
2.10.1 GENERAL
2.10.1.1 Properly designed pressure relief systems are essential to the integrity of LPG storage facilities. They are necessary to limit pressure buildup, under certain operating conditions or emergency contingencies, to levels acceptable for vessels and associated equipment. The ovcrpressure protection system must also provide for safe disposal of relief materials in order to avoid the creation of other hazards.
2.10.1.2 Requirements and recommended practices for relief systems on LPG equipment are discussed in 5.1.6, 6.6.3, 6.6.4 and A.1.5 in API Standard 2510.
2.10.1.3 In considering sizing of pressure relief protection for LPG storage vessels, the two most important contingencies are fire and overfihling. The potential for each of these contingencies should be evaluated, and the relief valve should be sized for the larger of the two relief flow requirements. Operationally, overfihling presents the greatest risk, but the design pressure of some storage facilities can he sufficiently high to prevent overpressure from the fill system.
2.10.1.4 When relief valves discharge directly to the atmosphere, as is common in most storage installations, release of liquid LPG to the atmosphere is an unacceptable situation. The resultant formation of large vapor clouds can cause flammable vapors to spread over wide areas and possibly reach an ignition source. Either the discharge from such relief valves must he tied to a closed disposal system (see 2.10.3), or positive design (see 2.9.1) or operational steps (see 3.3.2) must be taken to guard against overfill.
2.10.1 .5 If positive design or operational steps are taken to prevent overfill, it is acceptable to discharge pressure relief valves directly to the atmosphere. In many cases no flare or closed disposal systems are available. Relief valves and discharge systems must be adequately designed with equal importance given to sizing both the valve and the discharge piping. When the releases go directly to the atmosphere, the provisions of 2.10.2 must be considered.
2.10.2 ATMOSPHERIC RELIEF SYSTEMS
2.10.2.1 Either design or operational steps or both must be taken to ensure that liquid will not be released as a result of overfill ing. Re! iable gauging and high-level instrumentation are essential. Operator awareness of the high risks associated with liquid overfill and resultant attention to filling operation precautions are also essential. Means of rapidly interrupting the tilling operation by remote or automatic shutdown of pumps on fill lines should be considered (see 5.1.5.5, 5.1.6.5.2, and A. 1.3 in API Standard 2510).
2.10.2.2 Assuming only vapor release, the discharge stack should point vertically and be in accordance with 5.1.6.5 in API Standard 2510 and API Recommended Practice 521. Dispersion calculations affirm that vapor release from relief valves with this arrangement will be diluted below the flammable range while still within the jet momentum release plume (see API Recommended Practice 521). A release will not create wide area flammable clouds at grade as long as the exit velocity of the vapor is 100 feet per second or more and there is no liquid carryover into the discharge. Also, should the release be ignited in a fire, the burning plume will not impinge on any other equipment to cause localized failure. The radiant heat to the vessel may be sufficient to raise the metal temperatures to dangerous levels: therefore, application of water to the top of the vessel may he advisable for prolonged releases that have ignited.