Blind flange types, explained by someone who’s spent too long in pump rooms

If you’re speccing shutdown hardware or sealing off a troublesome spool, you’ve probably already Googled [blind flange types]. Short version: a blind flange is a solid plate that allows you to isolate, pressure-test, or simply park a line safely. The useful bit—especially for maintenance teams—is how quickly they bolt in and out without exotic tooling.

What’s trending in 2025

Two shifts, honestly: buyers want NDE-backed traceability, and they want corrosion resistance without 12-week lead times. Duplex and 316L blinds are inching up in share, and RTJ facings are holding steady in upstream. Many customers say they’re consolidating SKUs—ordering a core mix of [blind flange types] to cover Class 150–600 in carbon steel plus a small stainless set for chemical duty.

Quick specs (real-world picks)

Parameter	Options / Range (≈ values; real-world use may vary)
Sizes	NPS 1/2″–48″ (DN15–DN1200)
Pressure	ASME Class 150–2500; PN10–PN420
Materials	ASTM A105/A105N, A350 LF2 (low temp), A182 F304/F316, A694 F52–F65, Duplex 2205/2507
Facing	RF, RTJ, FF, TG/MF
Standards	ASME B16.5, B16.47 A/B, MSS SP-44, EN 1092-1
Testing	UT/MT/PT, PMI on alloy grades, hardness; EN 10204 3.1 certs
Coatings	Black oxide, anti-rust oil, epoxy paint (where specified)

Process flow (how good ones are made): billet selection → closed-die forging → normalizing/tempering → CNC machining and facing serration → drilling per bolt pattern → NDE (UT/MT) → PMI for stainless/duplex → marking/pack → final inspection against ASME/EN drawings. Typical service life: ≈10–20 years depending on media, pH, and cycles.

Where they’re used (and why)

• Hydrocarbon units: RTJ blinds for high pressure test blinds, sour service per NACE.
• Water & wastewater: RF A105 blinds for isolation; epoxy-coated when outdoors.
• Chemicals & pharma: 316L for clean service; smooth serration helps gasket seating.
• LNG/cryogenic: LF2 material with impact-tested heat lots, conservative torque.

Advantages? Frankly, speed and certainty. A good set of [blind flange types] lets maintenance shut in, pressure up to 1.5× design for a few minutes, then swap gaskets without drama.

Vendor comparison (field-notes level)

Vendor	Strengths	Certs	Lead time	Notes
JY Pipeline (Hebei, China)	Forging + machining in-house; strong RTJ range	ISO 9001; EN 10204 3.1	≈7–15 days ex-stock	Origin: Industrial District of North Circle, Mengcun, Cangzhou
EU Mill A	Advanced metallurgy; tight traceability	ISO 9001, PED	≈3–6 weeks	Premium pricing, superb docs
Trader B	Budget	Varies	≈2–4 weeks	Check heat traceability closely

Testing, data, and paperwork

Dimensional checks to ASME B16.5/B16.47, surface finish 125–250 AARH (RF), RTJ grooves to spec; UT per ASTM A388 on forgings; impact tests for LF2 at -46°C (where required); hardness typically 120–187 HB for A105. MTRs per EN 10204 3.1 are standard. For sour service, mills declare NACE MR0175 compliance on chemistry and heat treat.

Customization and a quick case

Customization: oversized thickness for temporary test blinds, tapped center ports, lifting lugs, special paint systems, and gasket pairing advice (spiral wound vs. RTJ ring numbers). It seems that small tweaks save big money in outage windows.

Case study: a Southeast Asia refinery swapped a mixed set for 316L RF blinds and A105 RTJ blinds (NACE compliant). Test pressure 1.5× design for 10 minutes, leak rate 0 visible; turnaround shaved ≈6 hours. Feedback from the maintenance lead: “The machining was clean; bolts torqued evenly—no rework.”

Author’s note: I’ve seen shops cut corners on serration and stamping. Don’t. Good [blind flange types] start with good forging stock and boring documentation.

References

1. ASME B16.5: Pipe Flanges and Flanged Fittings.
2. ASME B16.47: Large Diameter Steel Flanges.
3. EN 1092-1: Flanges and their joints.
4. NACE MR0175/ISO 15156: Materials for H2S service.
5. ISO 9001: Quality Management Systems.