Protection of storage tanks from two‐phase flow due to fire exposure

Fisher, Harold G.; Forrest, Harry S.

doi:10.1002/prs.680140307

Cited by 5 publications

(2 citation statements)

References 9 publications

(11 reference statements)

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“…If the process material is entirely gaseous, the total exposed area [13] (instead of wetted area) and a multiplier of heat‐transfer‐reduction factor of 0.3 should be used in the righthand side for all Eqs. 6, 6a, and 6b.…”

Section: Calculation Of Minimum Water Flow Rate To Absorb the Heatmentioning

confidence: 99%

A heuristic approach of calculating spray water flux needed to avert fire‐induced runaway reactions

Das

2006

Process Safety Progress

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In general all reactions have some heat effects. When the ability of the equipment to remove the heat is exceeded by the heat generated by a reaction, a hazardous situation called a runaway reaction may take place. Sometimes the exothermicity of runaway reactions is so high that the size of an emergency vent becomes impractical to install. A water spray system can sometimes be used to avert a fire‐induced runaway reaction. Because the water spray system has a finite activation time, insulation helps to prolong the time required to reach the decomposition temperature. This article concludes that the required water flux to avert the fire‐induced runaway reaction may be conservatively estimated by adding the water flux necessary to maintain an unbroken water film on the external surface of the equipment and the water flux necessary to absorb the fire heat after allowing for the splash loss and the in‐flight loss. When adequate spray water is used, the metal temperature of the insulation jacket cannot theoretically exceed the boiling point of water thereby ensuring the avoidance of fire‐induced runaway reactions whose adjusted onset decomposition temperature exceeds 100 ° C. Fire‐induced runaway reactions with lower onset temperature can also be avoided depending on the initial temperature of the contents, mass of the contents and equipment, insulation thickness, and fire duration, for example, but a detailed calculation including dynamic simulation is necessary and the burden of proof lies with the designer. The reliability of the spray water system must be maintained high to include its credit as an environmental factor defined according to NFPA 30 to avoid the fire‐induced runaway reaction as a scenario. Although API RP 521 does not allow any credit for sprinkler water, it allows credit, unlike NFPA 30, for insulation thickness and thus a runaway reaction can be avoided by using insulation alone according to API RP 521. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006

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Section: Calculation Of Minimum Water Flow Rate To Absorb the Heatmentioning

confidence: 99%

A heuristic approach of calculating spray water flux needed to avert fire‐induced runaway reactions

Das

2006

Process Safety Progress

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“…The governing equations and associated charts for this model are exposed in DIERS project manual among others (Fisher et al, 1992;ISO 4126-10, 2010;Fisher and Forrest, 1995). Christ et al (2011), in a very interesting contribution, give some recommendations for the case of external heating.…”

Section: Vapor/liquid Disengagementmentioning

confidence: 99%

Safety life cycle analysis applied to the engineering of pressure relief valves in process plants

Basco Montia

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Chemical plants and other industrial installations process and store hazardous materials, which represent a certain risk to people, equipment and the environment. Overpressure is one of the most common upsets in process plants and relief devices (pressure relief valves, rupture discs, overpressure-vacuum valves) are required on process equipment to prevent internal pressures from rising to levels, which could cause catastrophic equipment failure. They are the ultimate line of protection against equipment rupture and are therefore extremely critical safety elements. However, this criticality is not always accounted for in existing plants and in the engineering of new ones, as a lot of pressure relief systems audits performed recently, especially in US, have demonstrated. As an example, a 2014 report from Siemens Energy, Inc. of Houston, pointed out that, after performing 1,197 pressure relief systems audits between 2005 and 2014, consisting of 174,943 pieces of equipment and 80,372 pressure relief devices, 47% of the relief devices had a deficiency, e.g. 13,4% were undersized. In another statistical study focused on the maintenance process of pressure relief valves conducted in 1995 and based on 13,000 items inspected in the workshop, it was found that 18% of the valves only opened at a pressure higher than 110% of the set pressure and 3% did not open at a pressure of twice the set pressure. Therefore, it is clear that a methodology for increasing the reliability of pressure relief devices would be very useful. A new methodology has been developed in this thesis based on an extension of the safety life cycle concept developed for the safety instrumented systems, according to the IEC 61511. This new methodology covers all the steps of the life cycle of a pressure relief valve: a) risk analysis; b) safety requirements specification; c) design; d) reception, installation and checking; e) operation, maintenance and revision; f) management of change; g) decommissioning h) verification and i) documentation and technical audits. This methodology has been applied to three existing petrochemical plants, obtaining results that validate it as a useful tool in the target of increasing the reliability of pressure relief valves. Les plantes químiques i altres instal·lacions industrials processen i emmagatzemen materials perillosos, els quals representen risc per les persones, per els equips i per el medi ambient. La sobrepressió es una de les pertorbacions mes freqüents en les plantes de procés i els dispositius d’alleugeriment de pressió (vàlvules de seguretat, discs de trencament, vàlvules de sobrepressió-buit) són necessaris per prevenir que les pressions internes dels equips a pressió arribin a nivells, que puguin ocasionar la ruptura catastròfica del mateix. Aquests dispositius són l’ultima capa de protecció abans de la ruptura del equip i són, per tant, elements de seguretat molt crítics. Malauradament, aquesta criticitat no se la te sempre en compte en les plantes existents, ni tampoc en la enginyeria i construcció de plantes noves, com moltes auditories de sistemes d’alleugeriment de pressió realitzades recentment, especialment als Estats Units, han demostrat. Per exemple, un informe de Siemens Energy, Inc. de Houston del any 2014, indicava que després de haver realitzat 1197 auditories dels sistemes d'alleugeriment de pressió entre l'any 2005 i 2014, consistint en 174943 equips i 80373 dispositius d’alleugeriment de pressió, un 47% dels dispositius tenien una deficiència, per exemple, 13,4% estaven subdimensionats. En un altre estudi estadístic focalitzat en el manteniment de vàlvules de seguretat realitzat a l’any 1995 i basat en 13000 vàlvules inspeccionades al taller, es va trobar que el 18 % nomes obrien a una pressió mes alta que el 110% de la pressió de tarat i un 3% no obrien ni a una pressió del doble de la tarat. En conseqüència, esta clar que una metodologia per incrementar la fiabilitat dels dispositius d'alleugeriment de pressió seria molt útil. Una nova metodologia s’ha desenvolupat en aquesta tesi basada en una extensió del concepte del cicle de vida de seguretat funcional desenvolupat originalment per els sistemes instrumentats de seguretat, d’acord amb la IEC 61511. Aquesta nova metodologia avarca totes les etapes del cicle de vida d’una vàlvula de seguretat: a) anàlisi del risc, b) especificació dels requisits de seguretat, c) disseny, d) recepció, instal·lació i comprovació, e) operació, manteniment i revisió, f) gestió del canvi, g) donar de baixa h) verificació i i) documentació i auditoria tècnica. Aquesta nova metodologia ha estat aplicada a tres plantes petroquímiques existents, obtenint resultats que la validen com una eina útil per l’objectiu de augmentar la fiabilitat de les vàlvules de seguretat

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References

1998

Guidelines for Pressure Relief and Effluent Handling Systems

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Protection of storage tanks from two‐phase flow due to fire exposure

Cited by 5 publications

References 9 publications

A heuristic approach of calculating spray water flux needed to avert fire‐induced runaway reactions

A heuristic approach of calculating spray water flux needed to avert fire‐induced runaway reactions

Safety life cycle analysis applied to the engineering of pressure relief valves in process plants

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