Chapter 14 - Storage Tanks

Usually cylindrical they vary greatly in size from 2ft to 200ft diameter mostly flat bottomed with either an open or conical top, some of the large tanks used in refineries have a floating top where the roof floats on top of the liquid to eliminate vapour loss.
Figure 14-1 shows a tank farm with a combination of fixed and floating roof tanks.
The maximum plate thickness for tanks is 1 ½” which limits the diameter of large storage tanks. As with vessels the piping designer is responsible for determining the nozzle orientations and the location of ladders, platforms and instrumentation. Fire regulations must be observed and design must be in accordance with NFPA (National Fire Protection Association) codes.

The wind and seismic loadings, available space and soil- bearing strength determine the optimal height to-diameter ratio. Reduced heights and wider shapes are preferred in windy or seismically active areas, or where soil bearing capacity is limited. As available plot space decreases and soil-bearing strength increases, tanks are designed to be taller with smaller diameters.
API Standard 620 covers the design and construction of large, welded, field-erected low-pressure carbon steel above ground storage tanks (including flat-bottom tanks) with a single vertical axis of revolution.
The rules presented in this standard cannot cover all details of design and construction because of the variety of tank sizes and shapes that may be constructed. Where complete rules for a specific design are not given, the intent is for the manufacturer-subject to the approval of the purchaser's authorized representative-to provide design and construction details that are as safe as those which would otherwise be provided by this standard
The tanks described in this standard are designed for metal temperatures not greater than 250° F and with
pressures in their gas or vapour spaces not more than 15 pounds per square inch gauge.
The basic rules in this standard provide for installation in areas where the lowest recorded one-day mean atmospheric temperature is -50° F. Appendix R covers low-pressure storage tanks for refrigerated products at temperatures from +40° F to -60° F.

API Std 650 establishes minimum requirements for material, design, fabrication, erection, and testing for vertical, cylindrical, aboveground, closed- and open-top, welded carbon or stainless steel storage tanks in various sizes and capacities for internal pressures approximating atmospheric pressure (internal pressures not exceeding the weight of the roof plates), but a higher internal pressure is permitted when additional requirements are met. This Standard applies only to tanks whose entire bottom is uniformly supported and to tanks in non-refrigerated service that have a maximum design temperature of 93°C (200°F) or less.


Above is an excerpt from the chapters of the book: Detail Engineering and Layout of Piping Systems 5th Edition.
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