Petroleum Refining Design and Applications Handbook. A. Kayode Coker

of 0.85–1.27 mm/s (2–3 in./min).

      9 9. Gas velocity in gas/liquid separators, m/s (ft/s), with k = 0.11 (0.35) for systems with a mesh deentrainer and k = 0.0305 (0.1) without a mesh deentrainer.

      10 10. Entrainment removal of 99% is attained with 102–305 mm (4–12 in.) mesh pad thickness; 152.5 mm (6 in.) thickness is popular.

      11 11. For vertical pads, the value of the coefficient in step 9 is reduced by a factor of 2/3.

      12 12. Good performance can be expected at velocities of 30–100% of those calculated with the given k; 75% is popular.

      13 13. Disengaging spaces of 152–457 mm (6–18 in.) ahead of the pad and 305 mm (12 in.) above the pad are suitable.

      14 14. Cyclone separators can be designed for 95% collection of 5-µm particles, but usually only droplets greater than 50 µm need be removed.

      VESSEL (PRESSURE)

      1 1. Design temperature between −30 and 345°C is 25°C (−20° F and 650°F if 50°F) above maximum operating temperature; higher safety margins are used outside the given temperature range.

      2 2. The design pressure is 10% or 0.69–1.7 bar (10–25 psi) over the maximum operating pressure, which-ever is greater. The maximum operating pressure, in turn, is taken as 1.7 bar (25 psi) above the normal operation.

      3 3. Design pressures of vessels operating at 0–0.69 barg (0–10 psig) and 95–540°C (200–1000°F) are 2.76 barg (40 psig).

      4 4. For vacuum operation, design pressures are 1 barg (15 psig) and full vacuum.

      5 5. Minimum wall thickness for rigidity: 6.4 mm (0.25 in.) for 1.07 m (42 in.) diameter and under, 8.1 mm (0.32 in.) for 1.07–1.52 m (42–60 in.) diameter, and 9.7 mm (0.38 in.) for over 1.52 m (60 in.) diameter.

      6 6. Corrosion allowance 8.9 mm (0.35 in.) for known corrosive conditions, 3.8 mm (0.15 in.) for noncorrosive streams, and 1.5 mm (0.06 in.) for steam drums and air receivers.

      7 7. Allowable working stresses are one-fourth the ultimate strength of the material.

      8 8. Maximum allowable stress depends sharply on temperatureTemperature (°F)−20–6507508501000(°C)−30–345400455540Low-alloy steel, SA 203 (psi)18,75915,65095502500(bar)12901,070686273Type 302 stainless (spi)18,75018,75015,9506250(bar)129012901100431

      VESSELS (STORAGE TANKS)

      1 1. For less than 3.8 m3 (1000 gal.), use vertical tanks on legs.

      2 2. For 3.8–38 m3 (1000–10,000 gal.), use horizontal tanks on concrete supports.

      3 3. Beyond 38 m3 (10,000 gal.) use vertical tanks on concrete foundations.

      4 4. Liquids subject to breathing losses may be stored in tanks with floating or expansion roofs for conservation.

      5 5. Freeboard is 15% below 1.9 m3 (500 gal.) and 10% above 1.9 m3 (500 gal.) capacity.

      6 6. A 30-day capacity often is specified for raw materials and products but depends on connecting transportation equipment schedules.

      7 7. Capacities of storage tanks are at least 1.5 times the size of connecting transportation equipment; for instance, 28.4-m3 (7500 gal.) tanker trucks, 130-m3 (34,500 gal.) rail cars, and virtually unlimited barge and tanker capacities.

      Source: The above mentioned rules of thumb have been adapted from Walas, S.M., Chemical Process Equipment: Selection and Design, copyright 1988 with permission from Elsevier, all rights reserved.

       Physical Properties Heuristics.

	Units	Liquids	Liquids	Gases	Gases	Gases
		Water	Organic material	Steam	Air	Organic material
Heat capacity	kJ/kg °C	4.2	1.0–2.5	2.0	1.0	2.0–4.0
Density	kg/m3	1000	700–1500		1.29 at STP
Latent heat	kJ/kg	1200–2100	200–1000
Thermal conductivity	W/m °C	0.55–0.70	0.10–0.20	0.025–0.07	0.025–0.05	0.02–0.06
Viscosity	kg/ms	0°C 1.8 × 10−3	Wide Range	10–30 × 10−6	20–50 × 10−6	10–30 × 10−6
		50°C 5.7 × 10−4
		100°C 2.8 × 10−4
		200°C 1.4 × 10−4
Prandtl no.		1–15	10–1000	1.0	0.7	0.7–0.8

      Source: Turton, R. et al., Analysis, Synthesis, and Design of Chemical Process, Prentice Hall International Series, 2001.

       Typical Physical Property Variations with Temperature and Pressure.

	Liquids	Liquids	Gases	Gases
Property	Temperature	Pressure	Temperature	Pressure
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