Flanges

Module from the Piping Engineering Curriculum curriculum.

Module 5 — Flanges, Gaskets & Bolting · Learning Objectives · 1. Read a flange rating table (B16.5) for pressure-temperature limits · 2. Select flange facing (RF, FF, RTJ) by service and pressure class · 3. Identify gasket types and when to use spiral-wound vs ring joint vs kammprofile · 4. Apply API 6A / API 6BX ratings for high-pressure wellhead and wet service · 5. Specify ASTM A193 B7 / A194 2H bolting and when to upgrade to B7M (NACE) · ASME B16.5 Pressure-Temperature Ratings (A105 CS) — psig

Temp °F	Class 150	Class 300	Class 600	Class 900	Class 1500
–20 to 100	285	740	1480	2220	3705
200	260	675	1350	2025	3375
400	200	635	1270	1900	3170
600	140	550	1095	1640	2735
700	110	535	1065	1600	2665
800	80	410	825	1235	2060
Gasket Selection
Gasket Type	Temp Range °F	Press Range psig	Typical Use	Facing	Notes
Non-asbestos sheet	–20 to 500	< 300	Utility, air, water	RF or FF	Low cost
Spiral wound (SWG)	–320 to 1000	Up to 2500	Process, hydrocarbon	RF	Most common refinery
Kammprofile	–320 to 1000	Up to 2500	High cycle, high-T	RF	Reusable, tight
Ring-type joint (RTJ)	–50 to 1000	Class 900+	High P/T, wellhead	RTJ groove	Metal-to-metal seal
Double-jacketed	–20 to 900	< 600	Heat exchanger	RF	Soft filler core
Elastomer (O-ring)	Per elastomer	Low	Instrument, utility	RF groove	Viton –40 to 400
Bolting Quick Reference
Bolt Grade	Nut Grade	Service Temp	Wet H2S / NACE	Min UTS ksi	Notes
A193 B7	A194 2H	–50 to 1000 °F	No (too hard)	125	Standard carbon/alloy
A193 B7M	A194 2HM	–50 to 800 °F	Yes (HRC ≤22)	100	NACE MR0175
A193 B16	A194 4 or 7	To 1100 °F	No	110	Alloy, hot service
A193 B8	A194 8	–425 to 1500 °F	Limited	75	Austenitic SS
A320 L7	A194 4 or 7	–150 to 650 °F	No	125	Low-temp impact tested
A453 660	A194 8F	–320 to 1200 °F	No	130	Cryo + high-T

Source: Piping_Engineering_Curriculum_v1.xlsx · Sheet: Flanges

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