Single and two-phase flows of shear-thinning media in safety valves

Moncalvo, D.; Friedel, L.

doi:10.1016/j.jhazmat.2009.03.046

Cited by 4 publications

(5 citation statements)

References 4 publications

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“…Unsatisfactory results were obtained only with the 16.5 % PVP solution at the lowest relieving pressures, perhaps due to presence of minibubbles in the liquid. The CFD calculations show that the minimum viscosities in the safety valve lie in the slit between the seat and the disk, as originally supposed by Moncalvo and Friedel [4]. Fluid acceleration and recirculation cause viscosity decrements also elsewhere in the safety valve body.…”

Section: Discussionsupporting

confidence: 65%

“…The density of each aqueous solution is assumed to be constant during the flow and equal to the value measured by Moncalvo and Friedel [4]. The viscosity is instead modeled using the generalized Carreau Yasuda model in Eq.…”

Section: Methodsmentioning

confidence: 99%

“…In a recent publication, Moncalvo and Friedel [4] measured the mass flow rate of shear-thinning aqueous solutions of polyvinylpyrrolidone (PVP) in a LESER Type 441 DN 25/40 safety valve with a seat diameter of 23 mm and a lift of 2.2 mm for relieving pressures up to 6.5 bar. It was observed that the mass flow rate was almost unaffected by an increment in the relative weight of the polymer in the solution.…”

Section: Introduction and State Of The Artmentioning

confidence: 99%

“…Given the importance that CFD has obtained in the chemical and manufacturing industry, this alternative is applied here using the original data of Moncalvo and Friedel [4]. A quantitative evaluation of the CFD calculations is given by a cross-comparison between the measured and the calculated mass flow rates.…”

Section: Introduction and State Of The Artmentioning

confidence: 99%

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A Computational Investigation on the Flow of Non‐Newtonian Polymers in Safety Valves

Moncalvo

Friedel

Jörgensen³

2010

Chem Eng & Technol

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At the moment, very little knowledge is available about the flow of shear-thinning media in safety valves. In this paper, the flow of aqueous solutions of polyvinylpyrrolidone with a zero-shear viscosity between 0.3 and 3 Pa s in a LESER Type 441 DN 25/40 safety valve with a lift of 2.2 mm for relieving pressures up to 6.5 bar is computed using ANSYS FLUENT 12. According to these calculations, the lowest values of the dynamic viscosity are reached in the slit between the seat and the disk due to the large local velocity gradients. A more moderate increment in the fluidity of the solutions is observed also in the recirculation zone outside the disk when the stream from the rear of the valve meets the one from the front. A preliminary study suggests that the experimental flows may be turbulent in the slit and then evolve into a laminar profile in the discharge pipe. For this reason, the calculations are carried out assuming laminar, turbulent and transitional flows. The predicted mass flow rates are close to each other and to the measured values, except at relieving pressures close to ambient. The major cause of deviation seems to be the entrainment of air microbubbles, whose elongation may be responsible for additional shearing in the solutions with large polymer weight.

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Section: Discussionsupporting

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Section: Introduction and State Of The Artmentioning

confidence: 99%

Section: Introduction and State Of The Artmentioning

confidence: 99%

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A Computational Investigation on the Flow of Non‐Newtonian Polymers in Safety Valves

Moncalvo

Friedel

Jörgensen³

2010

Chem Eng & Technol

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“…Darby and Molavi (1997) developed a correction factor that covers a greater range of Reynolds numbers. When using these formulas for non-newtonian liquids, the pressure relief valves are oversized according to Moncalvo and Friedel (2009).…”

Section: Liquidsmentioning

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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