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Cara Menghitung TangkiB t kBertekanan

Sri Handayani

April 2010

sri h ‐ pap ‐ april 2010

Main pressure vessel components andconfigurations.configurations.

1. Use this and following overheads todescribe main pressure vesseldescribe main pressure vesselcomponents and shapes.2. Shell is primary component thatcontains pressure Curved shapecontains pressure. Curved shape.3. Vessel always closed by heads.4. Components typically weldedtogethertogether.5. Vessel shell may be cylindrical,spherical, or conical.6 Multiple diameters thicknesses or6. Multiple diameters, thicknesses ormaterials are possible.7. Saddle supports used for horizontalddrums.• Spreads load over shell.• One support fixed, other slidessri h ‐ pap ‐ april 2010

Main pressure vessel components and shapes.p p

1. Most heads are curved h f h hishape for strength, thinness, economy.2 Semi‐elliptical shape is2. Semi‐elliptical shape is most common head shape.3. Small vertical drums typically supported by legs.• Typically maximum 2:1 ratio of leg length to diameter.• Number, size, and attachment details depend onVertical Drum

on Leg Supports

attachment details depend on loads.


Tall Vertical Tower

1. Nozzles used for:• Piping systems• Instrument connections• Manways• Attaching other equipment2 Ends typically flanged may2. Ends typically flanged, may be welded.3. Sometimes extend into vessel.


Vertical Reactor

1. Skirt supports typically used for tall vertical vessels:• Cylindrical shell• Typically supported from grade2 General support design (not just2. General support design (not just for skirts)• Design for weight, wind,

h kearthquake.• Pressure not a factor.• Temperature also apconsideration for materialselection and thermal expansion.


Spherical Pressurized Storage Vessel

1 S h i l t1. Spherical storage vessels typicallysupported on legssupported on legs.

2. Cross‐bracing typically used toabsorb wind and

h k l dearthquake loads.


Vertical Vessel on Lug Supports

1. Vessel size limits for lug supports:1 10 ft di t• 1 – 10 ft diameter

• 2:1 to 5:1 height/diameter ratioheight/diameter ratio2. Vessel located above grade.g3. Lugs bolted to horizontal structure.


Define scope of ASME Code SectionVIII S f ASME C d S i VIIIVIII : Scope of ASME Code Section VIII

• Section VIII used is most widely used code

• Objective: Minimum requirements for safe

construction and operation Assures safeconstruction and operation Assures safe design.

• Di ision 1 2 and 3 Three di isions ha e• Division 1, 2, and 3 Three divisions have different emphasis.


Section VIII Division 1

• 15 psig < P £ 3000 psig15 psig < P £ 3000 psig• Applies through first connection to pipe• Other exclusions• Other exclusions– Internals (except for attachment weld to vessel)vessel)– Fired process heatersP t i i t l ith hi– Pressure containers integral with machinery

– Piping systems


Section VIII, Division 2,Alternative RulesDifferences between Division 1 and 2

• Scope identical to Division 1 but requirements

Differences between Division 1 and 2.

differ

– Allowable stress

– Stress calculations

– Design– Design

– Quality control

– Fabrication and inspection

• Choice between Divisions 1 and 2 based on economics


Scope of Division 3 : Alternative Rules Hi h P V lHigh Pressure Vessels

• Applications over 10,000 psi

• Pressure from external source processPressure from external source, process reaction, application of heat, combination

of theseof these

• Does not establish maximum pressure

• limits of Division 1 or 2 or minimum limits for Division 3.


Structure of Section VIIISection VIII,

Division 1• Subsection A

– Part UG applies to all vessels• Subsection B

– Requirements based on fabrication method– Parts UW, UF, UB

• Subsection C• – Requirements based on material class• – Parts UCS, UNF, UHA, UCI, UCL, UCD,

UHT ULW ULTUHT, ULW, ULT• Mandatory and Nonmandatory

Appendices


Primary factors that influence pressurel i l l ivessel material selection

• StrengthStrength

• Corrosion Resistance

i d k• Resistance to Hydrogen Attack

• Fracture Toughness

• Fabricability


Material strength and l dpressure vessel design

• Determines required component thickness• Overall strength determined by:

Yi ld St th– Yield Strength– Ultimate Tensile StrengthCreep Strength– Creep Strength

– Rupture Strength• Strength: Material’s ability to withstand imposedStrength: Material s ability to withstand imposed loading.

• Higher strength material ® thinner component.• Describe properties that are used to define strength.


Importance of corrosion resistance ini l l imaterials selection.

• Deterioration of metal by chemical actionDeterioration of metal by chemical action• Most important factor to consider• Corrosion allowance supplies additional thickness• Alloying elements provide additional resistance to corrosion

• Corrosion is thinning of metal.Corrosion is thinning of metal.• Adding extra component thickness (i.e., corrosion allowance) is most common method to address corrosioncorrosion.

• Alloy materials are used in services where corrosion allowance would be unreasonably high if carbon steel

dwere used.


Resistance to Hydrogen Attack

• At 300 ‐ 400°F, monatomic hydrogen forms molecular hydrogen in voids

• Pressure buildup can cause steel to crack• Above 600°F, hydrogen attack causes irreparable damage

through component Thickness• Low‐temperature H2 attack can cause cracking.• Higher temperature H2 attack causes through‐thickness

strength loss and is irreversible.strength loss and is irreversible.• H2 attack is a function of H2 partial pressure and design

temperature.• Increased alloy content (i e Cr)• Increased alloy content (i.e., Cr)• increases H2 attack resistance.• Reference API‐941 for “Nelson Curves.”

Hydrogen attack can damage carbon and low‐alloy steel.sri h ‐ pap ‐ april 2010

Maximum Allowable Stress

• Stress: Force per unit area that resists loadspinduced by external forces• Pressure vessel components designed tokeep stress within safe operational limits• Maximum allowable stress:Includes safety margin– Includes safety margin

– Varies with temperature and material• ASME maximum allowable stress tables forpermitted material specifications


ASME Maximum Allowable Stress


Design conditions and loadings to be considered in l h i l d ipressure vessel mechanical design.

• Determine vessel mechanical design• Design pressure and temperature, other g p p ,loadings

• Possibly multiple operating scenarios to y p p gconsider

• Consider startup, normal operation, p, p ,anticipated deviations, shutdown

• Worst case operating scenario determines p gmechanical design.


Design Pressure


Temperature Zones in Tall Vessels

Design temperature as a mechanical design condition

1 Margin required between1. Margin required between operating temperature and design temperature.

2 M i d i2. Maximum design temperature

needed to determine allowable

stress and thermal expansionp

considerations.

3. CET needed for material selection

considering brittle fracture.

4. There may be a wide temperature

variation between the bottom andvariation between the bottom and

top of a tall tower.sri h ‐ pap ‐ april 2010

Additional Loadingsh f l d l d• Weight of vessel and normal contents under

operating or test conditions

S i d t ti ti f i ht f• Superimposed static reactions from weight of attached items (e.g., motors, machinery, other vessels piping linings insulation)vessels, piping, linings, insulation)

• Loads at attached internal components or vessel supportssupports

• Wind, snow, seismic reactions

• Highlight other loads that must be considered in theHighlight other loads that must be considered in the mechanical design.

• These other loads may govern the mechanical designThese other loads may govern the mechanical design in local areas.


* Cyclic and dynamic reactions caused by pressure or thermal variations, equipment pressure or thermal variations, equipment mounted on vessel and mechanical loadingsequipment mounted on vessel, and mechanical loadings

* Test pressure combined with hydrostatic weight* Impact reactions (e.g., from fluid shock)* Temperature gradients within vessel component and differential thermal expansion between vessel componentsdifferential thermal expansion between vessel components

Weld Joint Categories


Weld Joint CategoriesWeld Type


Weld joint efficiency vs. Joint Type,

Category Radiographic ExaminationCategory, Radiographic Examination.

1. Weld joint efficiency, E, is a measure of weld quality j y, , q yand accounts for stress concentrations.2. E is needed in component thickness calculations.sri h ‐ pap ‐ april 2010

Summary Of ASME Code Equations


ASME Code equations for variousd i lcomponents under internal pressure.

Ci f ti l t i i i d• Circumferential stress governs minimum required component thickness in most cases.

• Longitudinal stress may govern local thickness inLongitudinal stress may govern local thickness in some cases (e.g., under wind or earthquake loads).

i S d i f i l• Review ASME Code equations for internal pressure design.* May calculate required thickness permitted May calculate required thickness, permitted pressure, component stress.

* Must account for corrosion allowance. Must account for corrosion allowance.


Different types of closure heads may be used

• The 2:l semi‐The 2:l semielliptical head is the most common.


HemisphericalHead to Shell Transition

Thickness transition at Head to Shell Transitiona hemispherical head.

1. Required thickness of a hemispherical head is about half that of theabout half that of the connected cylindrical shell.2 M t h t d2. Must have a tapered thickness transition in the head to end upmatching the shell thickness.


Sample Problem toProblem to illustrate calculationof required shell andhead

thickness for internalinternal pressure.


Sample Problem 1 ‐ Solution

1 Th i1. The corrosion allowance ( C = 0.125 in. ) must )be added to obtain the inside radiusinside radius.

2. The corrosion allowance must be added to the calculated thicknessthickness.


1. Review the relevant1. Review the relevant equation for a hemispherical head.

2. Note the sources for2. Note the sources for the relevant parameters and how corrosion allowance is accounted for.


Design For External Pressure and C i SCompressive Stresses

• Compressive forces caused by dead weight wind• Compressive forces caused by dead weight, wind, earthquake, internal vacuum

• Can cause elastic instability (buckling)y ( g)• Vessel must have adequate stiffness– Extra thickness– Circumferential stiffening rings• Buckling of a shell under external pressure or

i f i l t lcompressive forces is analogous to column buckling under a compressive force.

• Addition of stiffener rings reduces effectiveAddition of stiffener rings reduces effective buckling length.


• ASME procedures for cylindrical shells, heads, conical sections Function of:conical sections. Function of:

– Material– DiameterDiameter– Unstiffened length– Temperaturep– Thickness(Parameters that affect compressive strength)

1. Highlight the main parameters that affect b kli t thbuckling strength.

2. ASME Code has design procedure for each type of shell or head.of shell or head.


Stiffener Rings

1. Stiffener rings reduce the buckling length of a shell d b ith i id t idand may be either inside or outside.

2. Stiffener rings are not used for heads.sri h ‐ pap ‐ april 2010

Sample Problem to illustrate calculation of required li d i l h ll thi k f t lcylindrical shell thickness for external pressure.


1. Corroded shell diameter andthickness are used in the calculations.2 Th iff d l h f h h ll2. The unstiffened length of the shellmust include part of the head depth.

1. Note how Factor A is determined from these curves.1. Note how Factor A is determined from these curves.

2. After determine Factor A, go to applicable material chart.sri h ‐ pap ‐ april 2010

Factor A ‐ Figure 4.12Factor A Figure 4.12


1. Different material charts are used for different material types. This is chart used for most carbon and lowalloy steels.

f2. If A is under curves:

• Move up to intersect with temperature line.

• Move right to get B.

• B is then used to calculate allowable external pressure.

3. Since A is to left of curves in our case, must use lt t dalternate procedure.


1. Pa is calculated using indicated equation qbecause A is not under curves.

2. Must use E from curves at design temperature.


Exercise 2 ‐ Requiredh k f lThickness for Internal Pressure

• Inside Diameter ‐ 10’ ‐ 6” Inside Diameter 10 6• Design Pressure ‐ 650 psig• Design Temperature ‐ 750°F• Design Temperature ‐ 750 F• Shell & Head Material ‐ SA‐516 Gr. 70C i All 0 125 i• Corrosion Allowance ‐ 0.125 in.

• 2:1 Semi‐Elliptical heads, seamless• 100% radiography• Vessel in vapor service


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