DESIGN of
PRESSURE VESSEL Disu Disusu sun n oleh oleh : Agu Agus s Suwar uwarno no PUSPET PUSPETIND INDO O - GRESIK GRESIK
• Pres Pressu sure re vess vessel els s are are used used in many any industries (e.g., hydrocarbon processing, chemical, power, pharmaceutical, food and beverage). • The The mec mecha hani nica call des desig ign n of of mos mostt press pressur ure e vessels is done in accordance with the requirements contained in the ASME Boiler and Pressure Vessel Code, Section VIII.
Main Pressure Vessel Components - Shell - Head - Nozzle - Support
SHELL • The The she shellll is the the prim primar ary y com compo pone nent nt that that contains the pressure. Pressure vessel shells are welded together to form a structure that has a common rotational axis. Most pressure vessel shells are either cylindrical, spherical, or conical in shape.
HEAD • Head Head is part part/c /com ompo pone nent nt to clos close e at at bot both h end of shell. • Head Heads s are are typ typic icall ally y cur curve ved d rat rathe herr tha than n fla flat. t. • Curv Curved ed conf config igur urat atio ions ns are are str stron onge gerr and and allow the heads to be thinner, lighter, and less expensive than flat heads. Heads can also be used inside a vessel.
NOZZLES • A noz nozzl zle e is is a cylin cylindr dric ical al comp compon onen entt tha thatt penetrates the shell or heads of a pressure vessel. The nozzle ends are usually flanged to allow for the necessary connections and to permit easy disassembly for maintenance or access.
• Nozz Nozzle les s are are applications:
used used
for for
the the
foll follow owin ing g
– Attach piping for flow flow into or out out of the vessel. – Attach instrument instrument connections, connections, (e.g., level gauges gauges,, thermowe thermowells lls,or ,or pressur pressure e gauges) gauges) – Provide Provide access access to the vessel vessel interior interior at at manways. – Provid Provide e for direct direct attach attachmen mentt of other equi equipm pmen entt items items,, (e.g. (e.g.,, ahe aheat at excha exchang nger er or mixer).
SUPPORT • The The typ type e of of sup suppo port rt that that is used used depe depend nds s primarily on the size and orientation of the pressure vessel. In all cases, the pressure vessel support must be adequate for the applied weight, wind, and earthquake loads. • The The des desig ign n pre press ssur ure e of of the the vess vessel el is not not a consideration in the design of the support since the support is not pressurized. • Temp Temper erat atur ure e may may be a con consi side dera rati tion on in suppo support rt design from the standpoint of material selection and provision for differential thermal expansion.
Material Selection Factors • The The mai main n fac facto tors rs that that influ influen ence ce mate materia riall selection are: • Strength • Corros rosion Re Resistance • Resi Resist stan ance ce to Hydr Hydrog ogen en Atta Attack ck • Fracture To Toughness • Fabricability
Strength • Stren Strengt gth h is a mat mater eria ial'l's s abil abilit ity y to with withst stan and d an imposed force or stress. Strength is a significant factor in the material selection for a particular application. • Stre Streng ngth th dete determ rmin ines es how how thi thick ck a component must be to withstand the imposed loads
Corrosion Resistance • Corr Corros osio ion n is is the the deter deterio iora ratio tion n of of met metal als s by by chemical action. A material's resistance to corrosion is probably the most important factor that influences its selection for a specific application. • The mo most common me method th that is is use used d to to address corrosion in pressure vessels is to specify a corrosion allowance. A corrosion allowance is supplemental metal thickness that is added to the minimum thickness that is required to resist the applied loads.
Resistance to Hydrogen Attack • If this this hydrog hydrogen en diffus diffusion ion continu continues, es, pressu pressure re can build build to high levels within the steel, and the steel can crack. • At ele eleva vate ted d tempe tempera ratu ture res, s, ove overr appr approx oxim imat atel ely y 600° 600°F F (315,5C), monatomic hydrogen not only causes cracks to form but also attacks the steel. Hydrogen attack differs from corrosion in that damage occurs throughout the thickness of the component, rather than just at its surface, and occurs without any metal loss. • In add addit itio ion, n, onc once e hyd hydro roge gen n atta attack ck has has occu occurr rred ed,, the the metal cannot be repaired and must be replaced. • Inst Instea ead, d, mat mater eria ials ls are are sele select cted ed suc such h that that the they y are are resistant to hydrogen attack at the specified design conditions.
Fracture Toughness • Fract Fractur ure e tou tough ghne ness ss refer refers s to to the the abil ability ity of a material to withstand conditions that could cause a brittle fracture. The fracture toughness of a material can be determined by the magnitude of the impact energy that is required to fracture a specim specimen en using using Char Charpy py V-notch V-notch test. test. • Gene Genera ralllly y , the the fra fractu cture re toug toughn hnes ess s of of a mate materi rial al decreases as the temperature decreases. The fracture toughness at a given temperature varies with different steels and with different manufacturing and fabrication processes.
Fabricability • Fabricability refers to the ease of construction and to any special fabrication practices that are required to use the material. • Pres Pressu sure re vess vessel els s comm common only ly use use wel welde ded d construction. The materials used must be welda eldab ble so that hat ind indiv ivid idua uall com compo pone nent nts s can be assembled into the completed vessel.
DESIGN • Design Conditions and Loadings • All All pre pressu ssure re vesse vessels ls must must be desi design gned ed for for the the most severe conditions of coincident pressure and temperature that are expected during normal service. Normal service includes conditions that are associated with: – Start up. – Norm Normal al ope opera rati tion on.. – Devi Deviat atio ions ns fro from m nor norma mall oper operat atio ion n that that can can be be anticipated (e.g., catalyst regeneration or process upsets). – Shutdown.
DESIGN PRESSURE • Gene Genera ralllly, y, des desig ign n pres pressu sure re is is the the maxi maximu mum m inte intern rnal al pressure, that is used in the mechanical design of a pressure vessel. • For For full full or partia partiall vac vacuum uum condit condition ions, s, the design design pressu pressure re is applied externally and is the maximum pressure difference that can occur between the atmosphere and the inside of the pressure vessel. • Some Some pre press ssur ure e vess vessel els s may may expe experie rienc nce e both both int inter erna nall and external pressure conditions at different times during their operation. • The The mec mecha hani nica call des desig ign n of of the the pres pressu sure re vess vessel el in this this case is based on which of these is the more severe design condition. (see UG-21)
Operating Pressure • Oper Operat atin ing g press pressur ure e is is the the press pressur ure e to be used in operating condition. • The The ope operat ratin ing g pre press ssur ure e mus mustt be be set set base based d on the maximum internal or external pressure that the pressure vessel may encounter.
• The The foll follow owin ing g fact factor ors s must must be be cons consid ider ered ed:: – Ambie Ambient nt temper temperatu ature re effects effects.. – Normal Normal oper operatio ational nal varia variation tions. s. – Pressure Pressure variatio variations ns due due to changes changes in the vapor pressure of the contained fluid. – Pump or compre compressor ssor shut-off shut-off pressure pressure.. – Static Static head head due due to the liqu liquid id level level in the the vessel. – Syste System m pressu pressure re drop drop..
– Norm Normal al prepre-sta start rtup up acti activit vitie ies s or or othe other r operating conditions that may occur (e.g., vacuum), that should be considered in the design.
Design Temperature • The The des desig ign n tem tempe pera ratur ture e of of a pres pressu sure re vesse vessell is is the maximum fluid temperature that occurs under normal operating conditions, plus an allowance for variations that occur during operation. • The The max maxim imum um tempe tempera ratur ture e used used in desig design n sha shallll be not less than the mean metal temperature (through the thickness) expected under operating conditions for the part considered (see 3-2). • The The min minim imum um meta metall tem tempe pera ratur ture e use used d in in des desig ign n shall be the lowest expected in service.
Operating Temperature • The The Ope Opera rati ting ng tem tempera peratu ture re is is flu fluid id temperature that occurs under normal operating conditions. • The The ope opera rati ting ng temp temper erat atur ure e mus mustt be be set set based on the maximum and minimum metal temperatures that the pressure vessel may encounter.
Other Loadings • The The loa loadi ding ngs s tha thatt mus mustt be be con consi side dere red d to to determine the minimum required thicknesses for the various vessel components are as follows: – Interna Internall or external external design design pressu pressure. re. – Weight Weight of the the vessel vessel and and its normal normal contents contents under operating or test conditions. – Supe Superi rimp mpos osed ed static static react reactio ions ns from from the the weight of attached equipment (e.g., motors, machinery, other vessels, piping, linings, insulation). – Load Loads s at attac attache hed d of inte intern rnal al com compo pone nent nts s or vessel supports.
– Wind, Wind, snow, snow, and seism seismic ic reactio reactions. ns. – Cyclic and dynamic dynamic reactions reactions that that are caused by pressure or thermal variations, or by equipment that is mounted on a vessel, and mechanical loadings. – Test Test pre pressu ssure re comb combin ined ed with with hydr hydros osta tatic tic weight. – Impa Impact ct reac reacti tion ons s suc such h as as tho those se that that are are caused by fluid shock. – Temper Temperatur ature e gradien gradients ts within within a vessel vessel component and differential thermal expansion between vessel components.
MAXIMUM ALLOWABLE STRESS VALUE • The The max maxim imum um allow allowab able le stre stress ss valu value e is is the maximum unit stress permitted in a given material used in a vessel constructed under these rules. • The The maxi maximu mum m allow allowab able le tens tensilile e stre stress ss values permitted for different materials are given in Subpart 1 of Section II, Part D.(see (see UG-23) -23)..
MAXIMUM ALLOWABLE WORKING PRESSURE • The The max maxim imum um allo allowa wabl ble e wor workin king g pre pressu ssure re for for a vessel is the maximum pressure permissible at the top of the vessel in its normal operating position at the designated coincident temperature specified for that pressure. • It is the the lea least st of the the val value ues s fou found nd for for max maxim imum um allowable working pressure for any of the essential parts of the vessel and adjusted for any difference in static head that may exist between the part considered and the top of the vess vessel el.( .(se see e UG-9 UG-98) 8)
CORROSION • The The user user or his his desi design gnat ated ed agen agentt shal shalll speci specify fy corrosion allowances other than those required by the rules of this Division. Where corrosion allowances are not provided, this fact shall be indicated on the Data Report. • Vesse Vessels ls or parts parts of vesse vessels ls sub subje ject ct to to thi thinn nnin ing g by by corrosion, erosion, or mechanical abrasion shall have provision made for the desired life of the vessel by a suitable increase in the thickness of the material over that determined by the design formulas, or by using some other suitable method of protection. (see UG-25)
THICKNESS SHELL UNDER INTERNAL PRESSURE (CYLINDRICAL SHELL) See UG-27
CIRCUM STRESS (LONGITUDINAL JOINT)
OR
t = minimum required thickness P = internal design pressure R = inside radius of the shell course under consideration, (pertimbangkan C.A.) S = maximum allowable stress value (see UG-23 and the stress limitations specified in UG-24) joint efficiency for, or the efficiency of, E = joint appropriate joint in cylindrical or spherical shells, or the efficiency of ligaments between openings, which ever is less.
LONGITUDINAL STRESS (CIRCUM JOINT)
OR
CONTOH Thickness for Internal Pressure • Inside Diameter - 10’ - 6” • Desi Design gn Press ressur ure e - 650 650 psig sig • Desi Design gn Tem Tempera peratu ture re - 750° 750°F F • Shel Shelll & Hea Head d Mat Mater eria iall - SA-5 SA-516 16 Gr. Gr. 70 70 • Corr Corros osio ion n All Allow owan ance ce - 0.12 0.125 5 in. in. • 2:1 SemiSemi-Ell Ellipt iptica icall heads, heads, seamle seamless ss • 100% 100% rad radio iogr grap aphy hy • Vesse Vessell in vapor vapor ser servi vice ce
• The The min minim imum um thic thickn knes ess s or or max maxim imum um allowable working pressure of cylindrical shells shall be the greater thickness or lesser pressure as given by formula Circumferential Stress (Longitudinal Joints) or Longitudinal Stress (Circumferential Joints)
SPHERICAL SHELL
THICKNESS OF SHELL AND TUBES UNDER EXTERNAL PRESSURE
SYMBOL DEFINED • A = factor determined from Fig. G in Subpart 3 of Section II, Part D. Cylinders having Do /t values less than 10, see UG-28(c)(2). • B = p factor determined from the applicable material chart or table in Subpart 3 of Section II, Part D for maximum design metal temperature • Do = outside diameter of cylindrical shell course or tube • E = modulus of elasticity of material at design temperature. Taken from the applicable chart in Subpart 3 of Section II, Part D. • L = total length, in. (mm), of a tube between tube sheets, or design length of a vessel section between lines of support.
• P = external design pressure. • Pa = calculated value of maximum allowable external working pressure for the assumed value of t • Ro = outside radius of spherical shell. • t = minimum required thickness of cylindrical shell or tube, or spherical shell, in. (mm) • ts = nominal thickness of cylindrical shell or tube, in. (mm)
CYLINDRICAL SHELL AND TUBES •
Hitung nilai dari Do/t. A. Bila nilai Do/t ≥ 10, 10, ikut ikutii step step beri berikut kut:: – Step 1, Asumsikan nilai tebal t, dan hitung rasio L/Do dan Do /t. – Step 2, Lihat Fig. G pada Subpart 3 of Sectio tion II, II, Pa Part D. D. Pa Pakai nilai L/Do /Do sesuai perh perhit itun unga gan n yang yang dida didapa patt pada pada step step 1: •
Bila nilai L/Do > 50, 50, maka maka L/Don L/Donya= ya=50. 50.
•
Jika nilai L/Do < 0.05, maka L/Do nya = 0.05.
• Step 3, 3, Tarik garis dari L/ L/Do ke kurva Do/t sehi sehing ngga ga ada ada tit titik ik poto potong ngan an.. Dar Darii tit titik ik terse ersebu butt dit ditarik arik gari garis s lagi lagi ke area area fact actor A untu untuk k mem mempe pero role leh h nila nilaii fac factor tor A. A. • Step 4, Cari nilai B, dengan memasukkan nila nilaii fact factor or A yang yang dipe dipero roleh leh ke graf grafik ik/c /cha hart rt tabula tabularr sesuai sesuai mater material ial yang yang dipa dipakai kai,, di subpart subpart 3 ASM ASME E II D.(co D.(conto ntoh h fig-CS fig-CS1un 1untuk tuk carbon steel and low alloy steel). Tentukan kurv kurva a mate materi rial al/t /tem empe pera ratu ture re disai disain n yang yang akan dipakai.
Cont Conto oh graf grafiik untuk ntuk menca encari ri nil nilai B
• Step 5, Tarik garis dari nilai A ke kurva material/temperature material/temperature yang dimaksud. Pada Pada per perpo poto tong ngan an gari garis s tsb tsb,, tar tarik ik gari garis s ke arah rah area B untuk memperoleh nilai lai B. • Step 6, hitung maksimum allowable external pressure (Pa) dengan menggunakan nilai lai B yang didapat dari step 5 dengan rumus:
• Step 7, 7, Ji Jika ni nilai A te terletak pada se sebelah kiri kurv kurva a mater materia ial/ l/tem tempe pera ratur ture, e, perh perhitu itung ngan an Pa meng menggu guna naka kan n rumu rumus: s:
• Step 8, Bandingkan nilai Pa yang yang dida didapa patt dari dari perhitu perhitunga ngan n di step step 6 dan dan 7 dengan dengan desig design n pressure P. Jika Pa
• Bila Do/t < 10. • Step1, langkah kerja sama seperti step 1s/d 5 untuk Do/t≥10 untuk memperoleh nilai B: – Jika Jika Do/t Do/t < 4, nil nilai ai facto factorr A bisa bisa dih dihitu itung ng dengan rumusan:
untu untuk k nil nilai ai A ket ketem emu>0 u>0.10 .10,, dite ditetap tapka kan n A=0,10 A=0,10
• Step 2, Bila nilai B sudah didapat, hitung maksi maksimu mum m allowa allowable ble exter external nal press pressure ure (Pa1) dengan rumusan:
• Step 3, 3, hitung Pa2 de dengan rum rumusan:
• Step 4, 4, Bandingkan nilai Pa1 dan Pa Pa2, yang leb lebih kecil diambil sebagai Pa. Band Bandin ingk gkan an Pa deng dengan an P, jika jika Pa
EXTERNAL PRESSURE PADA SPHERICAL SHELL • Step 1, buat asumsi tebal material yang dipakai, t, dan dan hit hitu ung nil nilai fakt faktor or A den denga gan n rum rumus usan an::
• Step 2, Masukkan nilai A yang didapat ke chart yang yang sesu sesuai ai pada pada ASME ASME II D. D. Tari Tarik k gari garis s ke arah arah kurv kurva a mate materi rial al/t /tem empe pera ratu ture re hing hingga ga kete ketemu mu titi titik k perpoton tongan. Bi Bila nilai A be berada di se sebelah kir kiri kurva, kurva, perhi perhitun tungan gan Pa mengi mengikuti kuti step step 5.
• Step 3, cari nilai B dengan menarik perpo perpoto tong ngan an ke area area B. • Step 4, 4, hi hitung nilai Pa,dengan rumus:
• Step 5, Hitung nilai Pa dengan rumus berikut, bila nilai A berada disebelah kiri graf grafik ik sepe sepert rtii step step 2: 2:
• Step 6, bandingkan Pa terhadap P, bila: Pa
BUKAAN NOZZLE
• A = total cross-sectional area of reinforcement required in the plane under consideration (see Fig. UG-37.1) (includes consideration of nozzle area through shell if Sn /Sv <1.0) <1.0) • A1 = area in excess thickness in the vessel wall available for reinforcement (see Fig. UG-37.1)includes consideration of nozzle area through shell if Sn /Sv <1.0) <1.0) • A2 = area in excess thickness in the nozzle wall available for reinforcement (see Fig.UG-37.1) • A3 = area available for reinforcement when the nozzle extends inside the vessel wall (see Fig. UG-37.1)
• A41, A42, A43 = cross-sectional area of various welds available for reinforcement (see Fig. UG-37.1) • A5 = cross-sectional area of material added as reinforcement (see Fig.UG-37.1) • c = corrosion allowance • D = inside shell diameter • Dp = outside outside diameter of reinforcing element (actual size of reinforcing element may exceed the limits of reinforcement establish ed by UG-40; however, credit cannot be taken for any material outside these limits).
• d = finished diameter of circular opening or finished dimension (chord length at mid surface of thickness excluding excess thick ness available for reinforcement) of non radial opening in the plane under consider ation, in.(mm) [see Figs. UG-37.1 and UG-40] • E = 1 (see definitions for tr and tr n) n) • E 1 = 1 when an opening is in the solid plate or in Category B butt joint; or = joint efficiency obtained from Table UW-12 when any part of the opening passes through any other welded joint
• F = correction factor which compensates for the varia tion in internal internal pressure pressure stresses stresses on different different planes with respect to the axis of a vessel. A value of 1.00 shall be used for all configu rations except that Fig. UG-37 may be used for integrally reinforced openings in cylindrical shells and cones. [See UW16(c)(1).] • h = distance nozzle projects beyond the inner surface of the vessel wall. (Extension of the nozzle beyond the inside surface of the vessel wall is not limited; however, for reinforcement calculations, credit shall not be taken for material outside the limits of reinforcement established by UG-40.)
• K 1 = spherical radius factor (see definition of tr and Table UG-37). • L = length of projection defining the thickened portion of integral reinforcement of a nozzle neck beyond the outside surface of the vessel wall [see Fig. UG-40 sketch (e)] • P = internal design pressure (see UG-21), psi (MPa) • R = inside radius of the shell course under consideration • Rn = inside radius of the nozzle under consideration • S = allowable stress value in tension (see UG23), 23), psi (MPa (MPa))
allowable ble stre stress ss in nozzle nozzle,, psi (MPa) (MPa) (see (see S , Sn = allowa above) • Sv = allowa allowable ble stres stress s in vessel vessel,, psi (MPa) (MPa) (see (see S , above) • Sp = allowable stress in reinforcing element (pla (plate te), ), psi psi (MPa (MPa)) (se (see e S , above). • fr = strength reduction factor, not greater than1.0 [see • UG-41(a)] • fr 1 = Sn /Sv for nozzle wall inserted through the vessel wall. • fr 1 = 1.0 for nozzle wall abutting the vessel wall and for nozzles shown in Fig. UG-40, sketch (j), (k), (n) and (o). • fr 2 = Sn /Sv • fr 3 = (lesser of Sn or Sp ) /Sv • fr 4 = Sp /Sv
• t = specified vessel wall thickness,24 (not including forming allowances). For pipe it is the nominal thickness less manufacturing manufacturing under tolerance allowed in the pipe specification. • te = thickness or height of reinforcing element (see Fig. UG-40) • ti = nominal thickness of internal projection of nozzle wall • tr = required thickness of a seamless shell based on the circum ferent ferential ial stres stress, s, or of a forme formed d head, head, comput computed ed by the rules of this Division for the designated pressure. • tn = nozzle wall thickness.24 Except for pipe, this is the wall thickness not including forming allowances. For pipe, use the nominal thickness [see UG-16(d)]. • trn = required thickness of a seamless nozzle wall • W = total load to be carried by attachment welds (see UG-41)
• Design for Internal Pressure. • The total cross-sectional area of reinforcement A required under internal pressure shall be not less than (1 − fr 1 ) A = dtrF + 2tn trF (1 • Design for External Pressure The reinforcement required for openings in single-walled vessels subject to external pressure need be only 50% of that required in formula above.
MODEL SAMBUNGAN NOLLZE YANG DITERIMA SESUAI UW 16.
