Fire case Process Flowsheets & Simulations
Explore 2 validated, solved Fire case simulation flowsheets in MaximaLabs — real components: propane, n_butane. Open any one directly in your browser.
Solved via: PENG-ROBINSON.
Relief system — the fire case, on the flowsheet
Two vessels on one fire zone, each protected by a relief valve, both discharging into a shared flare header. The point is that nothing here is retyped: the relieving temperature, pressure, composition and molecular weight come from the solved streams, and the flare's load is the sum of what the valves actually send it. The relief study, block by block. PSV_SEP is on the separator overhead: its scenario is the API 521 external fire, Q = C·F·A^0.82 over 45 m² of wetted surface, and the vapour rate is Q/λ with the latent heat taken from the property package at the relieving pressure rather than assumed. PSV_SURGE protects the surge drum on the classic blocked-outlet case — it relieves the whole inlet flow, which is a number the canvas already knows. Each reports its required orifice area with the API 526 letter above it. Why they are drawn as lifted. Both carry relieving: true, which models the relief case rather than normal operation. Turn it off and each valve is shut — the process passes through untouched and only the sizing is reported — but then the flare has no load to size against, and says so instead of inventing one. A design load only becomes a flow when you say the valve is open. What the flare adds that valve-by-valve sizing misses. A fire zone lifts every valve in it at once, so the header carries both loads together: that is what sets the built-up back pressure, and it is checked against the lowest-set valve on the header, because a back pressure a 20-barg PSV shrugs off will chatter a 6-barg one beside it. The tip is checked against the API 521 ~0.5 Mach blow-off limit, and the radiant flux at a receiver 60 m away against the 4.73 kW/m² personnel level, with the heat of combustion computed from the relief gas itself. Bounds, stated. A single header (the multi-branch network with per-source back pressures is the Flare network tool); a point-source radiation model with no wind tilt; no knock-out or seal drum; and the fire case is API 520's peak instantaneous rate, not a depressuring transient — that is the Depressuring / blowdown tool.
7 unit ops • PENG-ROBINSON
48 0
View & openLPG storage — fire case, PSV sizing and flare radiation
An LPG storage and truck-loading facility, built so the relief study that follows it is the real one: rundown from the fractionator is cooled, let down to storage pressure, held in a sphere, and pumped to a loading line. The process itself is deliberately simple — the demonstration is what you do with it next, using the Analysis panel's API 520/521 tools, which is the workflow HYSYS sells its Depressuring and Flare utilities on. Fire case (Analysis > Fire-case relief). The governing scenario for a pressurised LPG vessel. A 160 m2 wetted sphere in a pool fire with adequate drainage takes 2.77 MW of absorbed heat (API 521 environment factor 1.0); at a relieving pressure of 18 bar abs the stored 70/30 propane-butane boils at 338 K with a latent heat of 270 kJ/kg, so the PRV must pass 10.3 kg/s — an API 526 M orifice. Reaction force (Analysis > Relief reaction force). That same 10.3 kg/s leaving a 150 mm tailpipe chokes at 9.5 bar and 260 m/s, putting 17.7 kN on the pipe — the load the tailpipe supports have to carry, and the number that decides whether the discharge piping needs bracing. Flare radiation (Analysis > Flare radiation). Burning that relief load (46 MJ/kg, 30% radiated) releases 473 MW. From a 40 m radiant centre the API 521 exclusion zones come out at 64 m horizontal for continuous exposure, 18 m for emergency personnel access, and zero for equipment. The actionable result: a receiver 60 m away sees 2.5 kW/m2 — comfortably under the 4.73 kW/m2 personnel limit, but above the 1.58 kW/m2 continuous limit, so a permanently manned building there needs shielding or relocation. Thermal relief (Analysis > Thermal relief). A second, entirely different scenario on the same facility: the loading line blocked in full of liquid and warmed by the sun. 12 kW into trapped LPG (cubic expansion coefficient 3.9e-3 /K at 526 kg/m3) needs only 0.017 kg/s — a D orifice, the smallest API 526 size. Sizing this line for the fire case instead would oversize the valve by three orders of magnitude in area, which is exactly the mistake the separate tool exists to prevent. **.
7 unit ops • PENG-ROBINSON
76 0
View & open