Blind Flange Types: Field Notes, Specs, and What’s Changing

If you’re sorting through blind flange types this year, you’ve probably noticed two things: lead times are better than 2022 (finally), and customers are asking for traceability plus sour-service documentation by default. In plants, the humble blind is still the easiest, safest way to isolate a line, prep for hydrotest, or leave room for future expansion. Simple component, serious job.

Where they’re used (and why)

Refineries, midstream block stations, FPSOs, and power plants use blinds to blank off dead legs, valve outlets, test headers, you name it. Maintenance teams like tapped blinds with jacking screws—less drama during removal. In brownfield work, blind flange types with RTJ grooves show up on higher-pressure sour gas lines, while raised-face (RF) flat out dominates water and steam services.

Typical specifications (real-world picks)

Type	Size Range	Pressure Class	Material	Facing	Standards
RF Blind	NPS 1/2″–48″	Class 150–900	A105N, A350 LF2	125–250 AARH	ASME B16.5/16.47
RTJ Blind	NPS 1″–36″	Class 600–2500	A105, F51/F53 (≈ for sour)	R/BX Grooves	ASME B16.5, API 6A (select)
Flat Face	DN15–DN1200	PN10–PN40	P235GH, A516 Gr.70	FF	EN 1092-1
Spectacle/Spade	Up to NPS 24″	Class 150–600	A516, SS316L	RF/RTJ	MSS SP-44, B16.48

How they’re made (quick process flow)

Materials: Forged carbon steel (A105/A105N), low-temp (A350 LF2), stainless (304/316L), duplex for chloride + H2S. Methods: open-die forging, solution/normalizing heat treatment, CNC profiling, facing (serrated ≈ 3.2–6.3 μm Ra), drilling, RTJ groove machining. Testing: PMI, hardness, dimensional to ASME B16.5/EN 1092-1, NDE (UT/MT), hydrotest around 1.5× design where specified, helium leak on request. Docs: 3.1/3.2 MTRs, heat traceability, NACE MR0175 for sour selections. Real-world service life? 20–30 years in clean water/steam; 5–15 in sour/chloride with proper alloy.

• Typical hardness: 170–220 HB (A105N, post-normalizing)
• Surface finish: RF 125–250 AARH; RTJ groove to B16.5 tolerances
• Hydrotest sample: No leakage at 1.5× MAWP, 10 min hold (ISO 5208)

Vendors at a glance

Vendor	Certifications	Stock Range	Lead Time	Strengths	Notes
HBJY Pipeline (Hebei)	ISO 9001, PED, CE (≈)	RF/RTJ 1/2″–48″	2–4 weeks typical	Custom machining, docs	Origin: INDUSTRIAL DISTRICT OF NORTH CIRCLE, MENGCUN, CANGZHOU CITY, HEBEI PRVINCE, CHINA
Regional Stockist A	ISO 9001	Common RF up to 24″	Ex-stock	Fast delivery	Limited RTJ grooves
OEM Mill B	ISO 9001, API (select)	Project sizes 30″+	6–10 weeks	Large dia., PED	MOQ applies

Customization, coatings, and feedback

Customization trends: tapped holes/jacking bolts, PTFE or FBE coatings, NACE-compliant duplex, spectacle sets to B16.48, and laser-etched heat IDs for digital MTRs. Many customers say the small premium for RTJ finish pays for itself in leak-free restarts.

Mini case study

A Southeast Asia refinery swapped aging RF blinds on a 24″ steam header for serrated RF A105N with jacking screws. Downtime during the next turnaround dropped ≈18% on that line—mostly because removal was cleaner and no re-facing was needed. Simple change, real savings.

What’s next

Expect more duplex in stock, tighter RTJ groove QC, and better digital traceability. Honestly, blind flange types don’t change often—but documentation and service guarantees absolutely do.

Authoritative citations

1. ASME B16.5: Pipe Flanges and Flanged Fittings (latest edition).
2. EN 1092-1: Flanges and their joints—Steel flanges.
3. ISO 5208: Industrial valves—Pressure testing of valves.
4. NACE MR0175/ISO 15156: Materials for use in H2S-containing environments.
5. ASME B16.48: Line Blanks; API 6A: Specification for Wellhead and Christmas Tree Equipment (groove refs).