Issue 06.95
LINDE AG
Werksgruppe Verfahrenstechnik und Anlagenbau
Hollriegelskreuth
bei Munchen
Orig.:TAW/Dr.Hock
1
LINDE STANDARD
Material Selection
for Alkaline Service
Checked: TAEiRetter
v
Appr.:
129-30
TAN/Hent.
Total 2 Pages
SupersedesIssue 12.91
Scope
This standardshall applyto the materialselectionand manufactureofvessels,pipingand appertainingvalvesmadeof
metallicmaterialsusedfor alkalineservice.“Alkalineservice”shall comprisethe followingrich and lean fluidsfor
chemicalwash units for gasescontainingC02 and/orH2S:
- Aqueoussolutionsof alkalihydroxides,(i.e. NaOH,KOH)with concentrations>1,0percentby weight.
- Organic,alkalinesolutionslike suliinole,sulfoline,MEA,DEA and MDEA.
- Aqueous,inhibitedsolutionsof potassiumcarbonate(13enfieldwash).
- AqueousNH3-solutions.
2
Purpose
The measuresdescribedin this standardshallpreventdamagesdueto stresscorrosioncracking.
3
Measures for Organic Alkaline Solutions and Aqueous Inhibited Solutions of Potassium
Carbonate and Aqueous NH3-Solutions
3.1 Materials
- For temperaturess 160”Cferriticcarbon-and/orC/Mn-steelswith nominalyieldstrength< 355 N/mm2shallbe
used.For pressurevesselsa corrosionallowanceof 3 mm is required.
- For chloride-freecausticsolutionsausteniticCrNi-steels,Ti-stabilizedor with C < 0,03V0maybe used.
3.2 Welding
- Dissimilarjoints, i.e. weldedjoints betweenausteniticand ferriticsteelsare not permitted.
- Socketweldsare not permitted.
- Filler materialsshallbe matchingwith the base metal;for ferriticsteelsthe yield strengthof the weld depositshall
not be considerablyhigher than that of the base metal.
3.3 Stress-relieving
A thermal stress-relievingof ferriticsteelsis required:
- For all pressure-retainingweldsin MEA-service.
- For pressurevesselswith designpressures>5 bar.
- For weldedjoints in contactwith the fluid, if the designtemperatureis above50”C.
- For bent pats with cold deforming> 5%, if the designtemperatureis above50°C.
After stress-relievingweldingoperationsor coldworkingare ~ allowedon thesecomponents.
4
Measures for Aqueous Solutions of Alkali Hydroxides with Concentrations
>1,0 Percent by Weight
4.1 Materials
- For causticconcentrations< 30V0by weightwith chloridecontents< O,lYO
by weight(as NaCl)and temperatures
< loooc”ferriticcarbon-and C/Mn-steelswith nominalyield strengths<355 N/mm*shallbe used.For pressure
vesselsa corrosionallowanceof 3 mm is required.
- For chloride-freecausticsolutionswith concentrations< 50Y0by weightand temperatures< 120°CausteniticCrNisteels,Ti-stabilizedor with C < 0,03°/0,maybe used.
4.2 Welding
- Dissimilarjoints, i.e. weldedjoints betweenausteniticand ferriticsteelsare not permitted.
- Socketweldsare not permitted.
- Filler materialsshallbe matchingwith the base metal;for ferriticsteelsthe yield strengthsof the weld depositshall
not be considerablyhigherthan that of the base metal.
Page 2
Issue 06.95
LS 129-30
LINDE AG Werksgruppe Verfahrenstechnik und Anlagenbau
4.3 Stress-relieving
Athermal stress-relievingofferriticsteelsisrequired:
Forvesselswithdesignpressures >5bar(independentofthe designtemperature)
Forweldedjoints incontact with the fluid, ifthe designtemperatureis abovethe curveofdiagram 1.
For bentparts withcolddeforming >5%, ifthe designtemperatureis abovethecurveofdiagram 1.
Afterstress-relievingweldingoperationsor coldworkingare ~allowed on thesecomponents.
100
90
80
70
60
50
40
I
30
0
5
10
15
20
25
30
Caustic Concentration( % by weight)
Diagram 1: Stress-relievingof carbonsteelsafter manufacturein the NaOH/KOH-service.
Revision:Revised.
PreviousIssues:02.70 (withdrawnsince03.S7),07.89,04.91, 12.91
Copyrightreserved.