Pipe Pressure Rating Guide - Barlow Formula & Charts

Pipe pressure rating, officially hu ua Maximum Allowable Working Pressure (MAWP), yog qhov siab tshaj plaws hauv siab uas cov yeeb nkab tuaj yeem muaj kev nyab xeeb ntawm qhov ntsuas kub. Qhov no yog qhov txawv ntawm qhov tawg siab, uas yog lub siab uas cov yeeb nkab yuav tawg. MAWP suav nrog qhov tseem ceeb ntawm kev nyab xeeb (feem ntau 3.5x ntawm qhov kawg tensile lub zog ntawm ASME B31.3), ua kom cov yeeb nkab ua haujlwm zoo nyob rau hauv nws cov qauv txwv thoob plaws hauv nws lub neej tsim. Kev xaiv cov yeeb nkab nrog qhov ntsuas tsis txaus siab yog ib qho ntawm feem ntau cov hauv paus ntsiab lus ntawm kev lag luam piping tsis ua hauj lwm, ua rau cov dej xau, kev puas tsuaj loj, thiab kev nyab xeeb.

Qhov tshwm sim ntawm kev xaiv qhov ntsuas siab tsis raug tuaj yeem ua rau hnyav. Ib cov yeeb nkab ua haujlwm saum nws MAWP tuaj yeem muaj kev tawm los (mus tas li deformation), nkag mus rau qhov kub siab, lossis tam sim ntawd tawg tawg. Hauv cov chaw petrochemical, cov yeeb nkab tsis ua haujlwm tau ua rau hluav taws kub, tawg, thiab tso tawm tshuaj lom. ASME B31 code series tsim kom muaj qhov tsawg kawg nkaus rau cov yeeb nkab siab tsim thoob plaws cov ntawv thov sib txawv: B31.1 rau cov kav dej fais fab, B31.3 rau cov kav dej, B31.4 rau kev thauj mus los hauv kav, thiab B31.8 rau kev xa roj. Kev nkag siab txog cov cai cai no yog qhov tseem ceeb rau kev nyab xeeb thiab ua raws li kev tsim cov kav dej.

Tus qauv Barlow yog qhov sib npaug ntawm kev suav cov theoretical tawg siab ntawm cov yeeb nkab:P=2St/D, qhov twg P yog sab hauv siab (MPa), S yog tso cai rau kev ntxhov siab (MPa), t yog nominal phab ntsa thickness (mm), thiab D yog sab nraud txoj kab uas hla (mm). Rau kev xam MAWP, qhov tso cai rau kev ntxhov siab S yog coj los ntawm ASME Tshooj II Ntu D ntawm qhov ntsuas kub tsim, thiab phab ntsa thickness t yog qhov nominal thickness minus manufacturing kam rau ua rho tawm corrosion. Cov mis xav tias nyias- cov kab mob ntawm phab ntsa (D / t > 10), uas siv rau feem ntau ntawm cov txheej txheem cov kav dej.

Piv txwv kev suav (Barlow Formula - Theoretical MAWP):Rau 4-nti SCH 40 A106 Gr.B yeeb nkab ntawm ambient kub:
OD=114.3 mm, Phab ntsa=6.02 mm, S=137.9 MPa (A106 Gr.B ntawm 38 degree)
P=2 x 137.9 x 6.02 / 114.3=14.5 MPa (~ 2100 psi)

Nco ntsoov tias ASME B31.3 code formula (t=PD / 2 (SE + PY))) yields qis MAWP ntawm kwv yees li 10.9 MPa rau tib cov yeeb nkab vim suav nrog kev sib koom ua haujlwm zoo E thiab kub coefficient Y. Cov lus hauv qab no siv cov qauv ASME B31.3 thiab sawv cev rau cov cai-.compli. Rau kev sib piv, qhov tawg siab (siv qhov tsawg kawg nkaus tensile lub zog S=415 MPa rau A106 Gr.B) yuav yog kwv yees li 43.7 MPa, muab qhov kev nyab xeeb ntawm kwv yees li 3.0 tiv thaiv tawg. Qhov no qhia txog qhov kev saib xyuas ntawm MAWP suav. Lub siab ua haujlwm tiag tiag yuav tsum nyob hauv qab ntawm MAWP, thiab feem ntau cov qauv tsim yuav tsum muaj cov npoo ntxiv tshaj qhov kev ua haujlwm siab.

Cov txiaj ntsig kev ntxhov siab tso cai yog lub hauv paus ntawm kev ntsuas ntsuas ntsuas. Cov txiaj ntsig no tau teev tseg hauv ASME Tshooj II Ntu D rau ntau txhiab cov khoom siv-qib- kub ua ke. Qhov kev ntxhov siab tso cai yog muab los ntawm qhov tsawg kawg nkaus ntawm: ib qho -peb ntawm qhov tsawg kawg nkaus tensile lub zog ntawm chav tsev kub, ob-feem peb ntawm qhov tsawg kawg nkaus yield zog nyob rau hauv chav tsev kub, los yog qhov nruab nrab creep rupture zog rau 100,000 teev muab faib los ntawm 1.5 ntawm qhov kub thiab txias.

Khoom siv	Qib	Tso cai Stress ntawm 38℃(MPa)	Tso cai Stress ntawm 400℃(MPa)	Max kub (degree)
A106	Gr.B	137.9	82.7	538
A335 P11	1.25Cr-0.5Mo	137.9	96.5	593
A335 P22	2.25Cr-1Mo	137.9	96.5	593
A335 P91	9Cr-1Mo-V	172.4	103.4	649
TP 304 SS	304	117.2	79.3	816
TP 316 SS	316	117.2	82.7	816

Nco ntsoov tias qhov tso cai rau kev ntxhov siab txo qis ntawm qhov kub siab. Qhov no kub derating nyhuv yog feem ntau pronounced rau carbon steel, uas muaj ib tug 40% txo ntawm ambient kub thiab 400 degree. Alloy steels zoo li P91 tuav ntau dua ntawm lawv qhov chaw nyob ib puag ncig- qhov kub thiab txias ntawm qhov kub siab, ua rau lawv qhov kev xaiv rau siab - qhov kub thiab txias. Cov hlau tsis muaj steel, thaum muaj qhov qis dua ambient - qhov kub thiab txias tso cai, tswj lawv lub zog zoo dua ntawm qhov kub siab tshaj 600℃.

Cov lus hauv qab no qhia txog kev ua haujlwm siab rau A106 Gr.B carbon steel yeeb nkab ntawm qhov kub thiab txias. Cov txiaj ntsig no yog nyob ntawm nominal phab ntsa thickness thiab tsis suav nrog kev tiv thaiv corrosion. Kev ua haujlwm tiag tiag yuav sib txawv raws li kev ua haujlwm tshwj xeeb thiab cov cai siv tau.

NB (inch)	SCH 40 (MPa)	SCH 80 (MPa)	SCH 160 (MPa)
1/2"	24.8	34.1	44.8
1"	20.9	28.5	40.5
2"	13.5	19.4	31.6
4"	10.9	15.6	25.2
6"	8.8	13.8	18.1
8"	7.8	12.3	14.7

Qhov kub thiab txias derating yog qhov txo qis hauv kev cia siab thaum ua haujlwm kub nce. Qhov tshwm sim no tshwm sim vim cov hlau tsis muaj zog ntawm qhov kub siab. Rau cov pa roj carbon steel, qhov kev ntxhov siab tso cai tseem nyob mus li mus txog 200 degree, ces pib txo qis. Ntawm 400 degree, qhov kev ntxhov siab tso cai ntawm A106 Gr.B yog kwv yees li 60% ntawm nws qhov chaw nyob -tus nqi kub. Ntawm 500 degree, nws poob rau kwv yees li 40%.

Stainless hlau muaj qhov zoo ntawm qhov kub thiab txias heev vim nws cov oxidation tsis kam thiab creep zog. Thaum 304 stainless hlau muaj qhov qis dua ambient - qhov kub thiab txias tso cai rau cov pa roj carbon steel (117.2 MPa vs 137.9 MPa), nws qhov kev cia siab ntawm 600℃yog kwv yees li 48 MPa piv rau xoom rau carbon hlau (uas tsis tso cai siab tshaj 538℃ib ASME code). Rau ultra-siab- daim ntawv thov kub siab tshaj 600 degree, npib tsib xee{12}}raws li alloys xws li Alloy 617 (UNS N06617) yog siv, nrog rau kev ntxhov siab ntawm 20-30 MPa ntawm 900℃.

Txhua ntu ASME B31 code muaj cov cai tshwj xeeb rau kev txiav txim siab ntsuas. ASME B31.1 (Power Piping) tswj cov kav dej hauv cov chaw tsim hluav taws xob hluav taws xob thiab cov chaw tsim khoom lag luam. Nws yuav tsum tau tsim kom muaj siab raws li cov kev cai ntawm ASME Tshooj I rau boiler sab nraud piping thiab muab kev sib npaug sib npaug rau cov yeeb nkab ncaj, khoov, thiab ceg txuas. ASME B31.3 (Cov Txheej Txheem Piping) yog cov cai siv dav tshaj plaws rau cov nroj tsuag tshuaj thiab petrochemical. Nws siv cov qauv Barlow-raws li txoj hauv kev nrog lub siab tsim tuab txiav txim siab los ntawm: t=(P x D) / (2 (SE + PY)), qhov E yog qhov ntev ntawm qhov sib koom ua ke zoo thiab Y yog qhov kub thiab txias - nyob ntawm coefficient.

ASME B31.4 (Pipeline Transportation) siv rau cov kua hydrocarbon thiab lwm cov kav dej ua kua. Nws siv txoj hauv kev tsim qauv uas qhov kev ntxhov siab ntawm kev tsim lub siab yuav tsum tsis pub tshaj qhov feem pua ntawm cov khoom tau teev tseg yam tsawg kawg nkaus yield zog (SMYS). Piv txwv li, ib qho qauv tsim ntawm 0.72 txhais tau hais tias qhov kev ntxhov siab hoop yog txwv rau 72% ntawm SMYS. ASME B31.8 (Gas Transmission) siv txoj hauv kev tsim qauv zoo sib xws tab sis nrog qhov chaw nyob - cov xwm txheej tshwj xeeb raws li cov pej xeem nyob ze ntawm lub raj xa dej, xws li 0.72 (nyob deb nroog) txog 0.40 (siab-cov nroog ceev ceev).

Kev ntsuam xyuas hydrostatic yog tus qauv txheej txheem rau kev txheeb xyuas qhov siab ncaj ncees ntawm kev tsim cov kav dej. Kev ntsuas siab feem ntau yog 1.5 npaug ntawm qhov kev tsim siab ntawm qhov ntsuas kub, tab sis tsis tsawg dua 1.5 npaug ntawm MAWP ntawm qhov ntsuas kub. Kev ntsuas siab yuav tsum tau khaws cia rau lub sijhawm yam tsawg kawg nkaus (feem ntau 10 feeb rau cov tshuab me me, ntev dua rau cov tshuab loj) thaum tag nrho cov pob qij txha thiab cov kev sib txuas raug tshuaj xyuas rau cov dej xau. Kev ntsuas pneumatic yog siv thaum kuaj hydrostatic tsis zoo (xws li cov tshuab uas tsis tuaj yeem zam dej, xws li oxygen lossis cryogenic kev pabcuam). Txawm li cas los xij, kev sim pneumatic muaj kev pheej hmoo ntau dua vim tias lub zog khaws cia hauv cov pa roj compressed thiab yuav tsum tau ceev faj ntxiv. Saib pebHydrostatic & Pneumatic Test Guide(54) rau cov txheej txheem ntxaws.

Kev lag luam tshuaj feem ntau ua haujlwm ntawm cov chav kawm siab ntawm 150 # mus rau 600 #, nrog rau cov txheej txheem dav dav ntawm 150 # lossis 300 #. Cov txheej txheem siab dua xws li hydrocracking thiab ammonia synthesis ua haujlwm ntawm 900 # txog 2500 #. Kev lag luam fais fab siv cov kev ntsuas siab tshaj plaws, nrog rau ultra-supercritical steam cycles ua haujlwm ntawm 2500# txog 4000# thiab kub txog li 620 degree. Cov kev mob hnyav no xav tau cov khoom siv siab- alloys xws li P92 thiab nickel{15}}raws li superalloys. Roj thiab roj pipeline pressures feem ntau yog nyob rau hauv ntau yam ntawm ANSI 300 mus rau 900 chav kawm, txawm hais tias lub ntsiab kis tau tus mob kab yuav ua hauj lwm ntawm lub siab tshaj 2000 psi.

Thaum xaj cov yeeb nkab rau ib daim ntawv thov tshwj xeeb, muab cov hauv qab no los xyuas kom raug xaiv: tsim siab thiab kub, cov kua nruab nrab (xws li corrosivity), cov cai siv tau (ASME B31.3, B31.1, thiab lwm yam), yuav tsum muaj kev tiv thaiv corrosion, thiab tej yam tshwj xeeb uas yuav tsum tau (kev pabcuam qaub, kev ua raws NACE, thiab lwm yam). ManufacturerPipe pab pawg neeg tsim khoom tuaj yeem pab xaiv cov khoom siv zoo, lub sijhawm, thiab cov txheej txheem tsim khoom rau koj cov kev xav tau tshwj xeeb. Peb kuj tseem muab cov txheej txheem uas tsis yog- qauv phab ntsa thickness customization rau cov ntawv thov uas cov txheej txheem teem caij tsis txaus lossis tshaj- tau qhia.

Hu rau peb pab neeg ua haujlwm engineering rau cov kws tshaj lij kev taw qhia thiab kev sib tw nqi ntawm cov yeeb nkab rau koj cov kev xav tau tshwj xeeb.

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