Storage Tanks and Pressure Vessels

8/10/2019 Storage Tanks and Pressure Vessels

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Calculation of TankVolume

A tank may be a single geometrical element, such as acylinder, a sphere, or an ellipsoid. It may also have acompound form, such as a cylinder with hemisphericalends or a combination of a toroid and a sphere. Todetermine the volume, each geometrical element usuallymust be calculated separately. Calculations for a full tankare usually simple, but calculations for partially filledtanks may be complicated.


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To calculate the volume of a partially filledhorizontal cylinder refer to Fig. 1 !1"#.Calculate the angle a in degrees. Any units oflength can be used, but they must be the samefor H, R, and L. The li$uid volume


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This formula may be used for any depthof li$uid between %ero and the full tank,

provided the algebraic signs areobserved. If H is greater than R, sin acos a will be negative and thus will addnumerically to a&'(.# . Table 1 !)*

gives li$uid volume, for a partially filledhori%ontal cylinder, as a fraction of thetotal volume, for the dimensionless ratioH/D or H/2R.


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+erry s " th edition-

Table 1 !'


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The volumes of heads must be calculated separately andadded to the volume of the cylindrical portion of the tank. Thefour types of heads most fre$uently used are the standarddished head,/ torispherical or A0 2 head, ellipsoidal head,

and hemispherical head. 3imensions and volumes for all fourof these types are given in Lukens S un Heads, Lukens !nc.,"oatesville, #ennsylvania. $ ro%imate volumes can also becalculated by the formulas in Table 1 !)'. Consistent unitsmust be used in these formulas. (8 th ed: Table 10-60)


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A partially filled hori%ontal tank re$uires the determination of thepartial volume of the heads. The 4ukens catalog gives appro5imatevolumes for partially filled 6a5is hori%ontal7 standard A0 2 andellipsoidal heads. A formula for partially filled heads, by oolittle!Ind. &ng. "hem., 21, 322323 (1928)], is

where in consistent units ' ( volume, R ( radius, and H ( de th o)li*uid.


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3oolittle made some simplifyingassumptions which affect thevolume given by the e$uation,but the e$uation is satisfactoryfor determining the volume as afraction of the entire head. Thisfraction, calculated by 3oolittle sformula, is given in Table 1 !))as a function of H/Di +H is thede th o) li*uid, and Di is theinside diameter . Table 1 !))

can be used for standarddished, torispherical, ellipsoidal,and hemispherical heads withan error of less than 8 percent ofthe volume of the entire head.The error is %ero when H/Di ( -,-. , and .-. Table 1 !)) cannotbe used for conical heads.

"errys 8 th ed: Tabe 10-61


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9hen a tank volume cannot be calculated or whengreater precision is re$uired, calibration may benecessary# This is done by drainin$ 6or filling7the tank and measuring the volume of li$uid. Themeasurement may be made by weighing, by acalibrated fluid meter, or by repeatedly filling smallmeasuring tanks which have been calibrated byweight.


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%ivera, &ourelane '#h - *101


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Pressure Vessels A pressure vessel is a closed container designed to holdgases or li$uids at a pressure substantially different from

the ambient pressure. a vessel in which the pressure is obtained from an

indirect source or by the application of heat from an

indirect source or a direct source The vessel proper terminates at-6a7 the first circumferential :oint for welded endconnections;6b7 the face of the first flange in bolted flange

connections; or6c7 the first threaded :oint in threaded connections.


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+ressure vessels include but are not limited tocompressed gas storage tanks 6i.e., air, o5ygen,nitrogen tanks, etc.7, anhydrous ammonia tanks,hydro pneumatic tanks, autoclaves, hot waterstorage tanks, chemical reactors and refrigerantvessels, designed for a pressure greater than1' psi and a volume greater than ' cubic feet involume or one and one!half cubic feet in volumewith a pressure greater than ) psi.


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+ .% /: -1# 23 3452% "4%T2+ 4 "% .% / &


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olted +lan$ed 5ointsFlanged :oints are used for connecting pipes and instrumentsto vessels, for manhole covers, and for removable vessel

heads when ease of access is re$uired.Flanges may also be used on the vessel body, when it isnecessary to divide the vessel into sections for transport ormaintenance.Flanged :oints are also used to connect pipes to othere$uipment, such as pumps and valves.0crewed :oints are often used for small diameter pipeconnections, below * mm. Flanged :oints are also used forconnecting pipe sections where ease of assembly anddismantling is re$uired for maintenance, but pipework willnormally be welded to reduce costs.


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7 & -52 T +rocess vessels are built up from preformed parts,cylinders, heads, and fittings, :oined by fusion

welding. ?iveted construction was used e5tensivelyin the past 6prior to the 1 * s7 but is now rarelyseen e5cept on very old plants.Cylindrical sections are usually made up from platesections rolled to the re$uired curvature. Thesections 6strakes7 are made as large as ispracticable to reduce the number of welds re$uired.The longitudinal welded seams are offset to avoid acon:unction of welds at the corners of the plates.


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3ivision 1- Contains general rules and is mostcommonly followed, particularly for low pressurevessels.

3ivision 8- Contains alternative rules that are morerestrictive on materials, design, temperatures,

design details, fabrication methods, andinspection, but allow higher design stresses andhence thinner vessel walls. 3ivision 8 rules areusually chosen for large, high!pressure vesselswhere the savings in metal cost and fabricationcomple5ity offsets the higher engineering andconstruction costs.

4 3 6American 0ociety of echanical 2ngineers7 2


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3ivision #- Contains alternative rulesintended for vessels with design pressuresgreater than 1 , psig. It does notestablish a ma5imum pressure for vesselsdesigned in accordance with 3ivision 1 or3ivision 8, but provides alternative rules

that can be followed for thicker!walledvessels.


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Storage Tanks and Pressure Vessels

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