Costing of Pressure Vessels 1. Quick Method: simple cylindrical vessels 2. Costing by Weight: more complex shapes

Quick Method

Pressure and Material Factors: F BM =f(F P xF M ) go to Figure 5-46

Bare Module Factors

Tower Packings

Trays

Cylindrical Vessel Cost Cost of internals added onto vessel cost for packed or trayed columns. Heated vessels cost more. Pressure Material

What about more complex shapes? Estimate cost based on weight of vessel

Contributions to Weight Vessel shell (cylindrical or conic sections) Vessel heads Cost of manways, skirts, nozzles Cost of auxiliaries - platforms, ladders, handrail Total weight = (weight of shell + weight of heads)x1.1 (for flanges, auxiliaries etc.)

Hoop Stress Calculation Pressure stress < tensile strength of shell t R p S = maximum tensile stress (Pa) C s = corrosion allowance (m) t = wall thickness (m) p = gauge pressure (Pa) R = vessel radius (m) (Ulrich pp 250)

Tensile Stress for Metals Strong function of temperature!

Vessel Heads Singh, 1990 (Course Pack) Hemisphere Ellipsoidal Torispherical (Most common) Conical Sphere Need to match head thickness to shell thickness.

Torispherical Heads L=crown or dish radius r=knuckle radius R=vessel radius

Torispherical Heads Singh, 1990: SE = effective stress = 0.9S p, t, C s as before L = dish radius r = knuckle radius M = factor Typically: L=2R; r=R/8, so