GOST 12836 PN 2.5–PN4.0 Blind Flange, straight from Hebei

If you’ve ever had to cap a pipeline in a tight shutdown window, you know the humble Blind Flange can make or break the schedule. This one comes out of North Guzhuangying Village, Ansu Town, Xushui District, Baoding, Hebei—an area that, to be honest, has quietly become an engine for Eastern European and CIS pipeline hardware. Standard is GOST 12836; pressure classes run PN6 up to PN63 (yes, PN2.5 and PN40 options are doable), and sizes DN15–DN500. I’ve walked these shops; the routine is rigorous and—surprisingly—pretty nimble.

What it is and why buyers pick it

A Blind Flange closes the line for pressure testing, isolation, or future tie-ins. Compared with temporary caps, it’s safer at higher PN ratings, easier to re-open, and—if machined right—keeps gasket stress uniform. Many customers say they like the predictable bolt stress and the fact that inspection teams accept it without fuss.

Key Specifications (GOST 12836)

Process flow, briefly

• Material prep: mill cert review (CT20/16Mn or 304/316), UT screening; cut-to-size.
• Machining: OD, thickness, bolt circle; RF/FF surfacing; deburr and stamp.
• Treatments: stress relief for thick sections; rust‑proof oil or paint.
• Quality: dimensional gauges per GOST 12836; surface roughness check; hardness sampling (CS ≈ HB 120–180).
• Testing: hydro proof test (where specified); PMI for stainless; packaging with edge guards.

Service life? In benign media, a carbon‑steel Blind Flange can run 20–30 years; stainless often longer, corrosion permitting.

Where it’s used

Refining turnarounds, gas distribution headers, district heating loops, chemical isolation spools, and test packages. I guess the most common use I see is pressure testing new branches before tie-in—quick, safe, reversible.

Vendor snapshot (selection)

Customization

Non-standard thickness for high gasket stress? Spiral-wound compatibility grooves? Marking to Russian/CIS conventions? All are routine. For sour service, a 316L Blind Flange with low-ferrite control and PMI is typical.

Mini case notes

District Heating, DN400 PN16: 16Mn Blind Flange, RF finish Ra ≈ 3.2 μm, hydro proof at 24 bar for 10 min—no seepage. Client feedback: “Bolting lined up first shot.”

Chemical Tie‑in, DN80 PN40: 316L Blind Flange for chloride media, PMI 100%, gasketed with graphite SWG. After 9 months, flange face showed negligible wear in inspection report.

Certifications and data points

• ISO 9001 QMS; EAC availability for EEU markets.
• EN 10204 3.1 MTC; hardness and roughness logs archived per batch.
• Typical flatness tolerance held within ≈ 0.3 mm for DN≤300 (project-specific).

References

1. GOST 12836 — Steel blind flanges, dimensional and technical requirements.
2. GOST 33259:2015 — Steel pipe flanges, general specifications.
3. EN 10204:2004 — Metallic products, types of inspection documents (3.1).
4. ISO 9001:2015 — Quality management systems, requirements.
5. TR CU 032/2013 — On safety of pressure equipment (EAC).