Materials

Module from the Piping Engineering Curriculum curriculum.

Module 2 — Piping Materials & Spec Selection · Learning Objectives · 1. Select carbon steel, low-alloy, stainless, and duplex for common refinery services · 2. Apply MDMT and impact test rules per B31.3 §323.2.2 and Table A-1 · 3. Recognize galling, chloride SCC, HTHA, and wet H2S service limits · 4. Read a piping line class sheet and decode material spec codes · 5. Identify when to require NACE MR0175 / ISO 15156 hardness control · Material Selection by Service

Service	Primary Material	Alt / Upgrade	Key Concerns	Reference	Typical Class
Hydrocarbon (low-S, <500 °F)	A106-B / A53-B CS	A333-6 for cold	Corrosion allowance 0.125"	IPE-EP-5-2-1	150-300
Hot oil (500–750 °F)	A335 P5 or P11	A335 P22 at creep	HTHA above 450 °F H2	API RP 941	300-600
Sour gas/liquid (wet H2S)	NACE-compliant CS	A312 TP316L if severe	SSC, SOHIC, HIC, HB ≤22 Rockwell	NACE MR0175	300-600
Amine service	CS with PWHT	Upgrade to 304L	Alkaline SCC, velocity ≤5 ft/s	API RP 945	150-300
Caustic (>50 °C, >50% NaOH)	304L/316L SS	Monel 400	Caustic SCC above thresholds	NACE SP0403	150
Hydrogen > 1000 psig, > 430 °F	A335 P11/P22, P91	321H or 347H SS	HTHA (Nelson Curve)	API RP 941	900-1500
Cryogenic (–50 to –150 °F)	A333-6 low-temp CS	A312 TP304 / 304L	Charpy impact at MDMT	B31.3 §323.2.2	300-600
Chloride service	Duplex 2205	Super duplex 2507	Pitting / CSCC	NACE SP0175	300
Air / nitrogen (utility)	A53-B galvanized	CS painted	External corrosion	IPE-EP-5-2-2	150
Instrument air	304/316 SS tubing	Copper (legacy)	Dew-point < –40 °F	ISA 7.0.01	150
Common ASTM Specs Quick Reference
Spec	Form	Grade	Max Temp °F	Use	MDMT Basis
A106	Seamless pipe	Gr. B	800	CS process piping	Impact per B31.3
A53	ERW/seamless pipe	Gr. B	750	CS low-temp limited utility	–20 °F without impact
A333	Low-temp CS	Gr. 6	650	Cryo & cold service	–50 °F, tested
A335	Alloy pipe seamless	P5, P11, P22, P91	1100+	Hot oil, hydrogen	Per grade
A312	Stainless pipe	TP304/304L/316/316L/321/347	1500	Corrosive / high-temp	–425 °F many grades
A790	Duplex stainless	2205, 2507	600	Chloride/offshore	–50 °F
A358	EFW stainless	Class 1 or 3	1500	Large diameter SS	Per grade
A234	Butt-weld fittings	WPB, WP11, WP22	Match pipe	Elbows, tees, reducers	Match base
A105	Forged CS flanges/fittings	—	800	Flanges	Impact if < 32 °F
A182	Forged alloy/SS	F11, F22, F304, F316, F321	Match pipe	Flanges, forged fittings	Per grade

Source: Piping_Engineering_Curriculum_v1.xlsx · Sheet: Materials

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