Blind Flanges ship with raised face (RF) default. Get a 4-hour quote with line-tab calculation per ASME B16.5 §4.2.
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Class 150-2500 in A105, A350 LF2, A182 F304/F316/F51/F55 — all NACE MR0175 qualified.
Blind Flanges (BL) are solid-disk pipe connectors with no center bore, used to terminate a pipeline, isolate a section for maintenance, or serve as a pressure-test closure. They allow easy access for inspection, cleaning, or future expansion without cutting the pipe. As an ASME B16.5 blind flange manufacturer and supplier based in Hebei, China, we produce blanks to ASME B16.5 (1/2"–24"), ASME B16.47 Series A (26"–60"), ASME B16.47 Series B (26"–60"), EN 1092-1 Type 05, JIS B2220 BL, and HG/T 20592.
A blind flange must withstand the same pressure-temperature rating as the mating companion flange. ASME B16.5 Table 2-1.1 (Group 1.1 carbon steel) and Table 2-3.1 (Group 1.9 low-temperature) define the maximum allowable working pressure (MAWP) by class and temperature. Per ASME B16.5 §4.2, the pressure rating of a blind flange equals the next-larger pipe size: a 12" Class 150 BL is calculated using the 14" gasket dimensions, not the 12" dimensions. This rule (sometimes called the "next-size-up rule") is a frequent source of miscalculation. Engineers specifying blind flanges must verify the gasket stress and bolt load calculations against this rule.
Class 150 carbon steel blind flanges are rated for 285 psi at 38°C up to Class 2500 at 6170 psi. ASME B16.47 large-bore Series A (Class 150–900) covers NPS 26"–60". Series B (Class 75–300) is the API 605 standard replacement. Large-bore blind flanges are typically produced from rolled plate and welded (for diameters above 36"), or forged (smaller sizes). Welded plate blinds are produced per ASME B16.47 §6.2 and require 100% radiographic examination of the weld per ASME V Article 2.
Paddle blanks (figure-8 blanks, spectacle blinds) are a variant for systems requiring periodic opening. They are split in half: one half solid (the blind), one half bored to the pipe ID. The paddle can be rotated between two gaskets to switch between blind and open without unbolting. Paddle blinds are preferred for systems with scheduled inspection (e.g. ASME VIII pressure vessels requiring annual internal inspection), where the operation must be verified with a hand-lever and not a wrench.
Materials stocked include A105 carbon steel (-29°C to +425°C), A350 LF2 low-temperature (-46°C normalized), A182 F11/F22/F91 Cr-Mo alloy for high-temperature service, A182 F304/F316/F316L stainless, 16MnDR Chinese low-temp, and duplex F51/F55. All supplied with EN 10204 3.1 mill certificate. NACE MR0175 hardness compliance on request for sour service applications. PED 2014/68/EU CE-marking under Module H or A2 available for EU shipments.
Manufacturing process: For Class 150–600 blind flanges up to NPS 24", we use open-die forging or closed-die forging from round billet. For B16.47 large-bore Series A (NPS 26"–60"), we use plate-rolled and welded construction per ASME B16.47 §6.2. Gasket face and bolt circle are machined on CNC vertical turning lathes. Surface finish Ra 3.2–6.3 μm (125–250 μin) for RF (raised face) and Ra 0.8–1.6 μm for RTJ (ring type joint) grooves.
Applications: pipeline end terminations (for future expansion), pressure test closures (hydrostatic test at 1.5× design pressure per ASME B31.3 §345), maintenance isolation (for replacing downstream valves without draining the upstream system), vessel head closures (per ASME Section VIII Div 1 UG-34), and instrumentation header terminations. Shipping from Shanghai/Qingdao/Ningbo in 14–30 days to major ports. Custom clearance documents include commercial invoice, packing list, certificate of origin (China Chamber of Commerce notarized), MTC EN 10204 3.1, and third-party inspection certificates (SGS / BV / TUV / Intertek) on request.. PED 2014/68/EU CE-marking is available under Module H or A2 for EU shipments. ASME U-stamp / U2-stamp certification available for pressure vessel nozzle closures.
A standard Blind flange is a solid disk that must be unbolted to open the line. A Paddle Blank (figure-8 blank) is split: one half is solid (the blind), one half has a hole matching the pipe ID. The paddle can be rotated between two gaskets to switch between blind and open without unbolting the joint. Paddle blanks are preferred for systems requiring periodic inspection (e.g. ASME VIII pressure vessels needing annual internal inspection) and for short pipe runs where bolting up a solid blank would be cumbersome.
ASME B16.5 §4.2 specifies that a blind flange is rated using the gasket dimensions of the next-larger pipe size. For example, a 12" NPS Class 150 blind flange is calculated using the 14" NPS gasket dimensions (because the 12" gasket doesn't surround a bore, there is no bore, so the gasket sits as if it were around the next-larger pipe). This 'next-size-up rule' is the most common cause of miscalculation when designing blind flange joints. We supply pressure-temperature rating curves on request.
Use a spectacle blind (paddle) when: (1) the line needs frequent isolation/re-opening (e.g. between two process units that alternate operation), (2) the pipe run is short and bolting up a solid blind is impractical, (3) ASME VIII pressure vessel requires periodic internal inspection, (4) the deadleg between two valves needs regular draining/venting. For permanent terminations with no scheduled re-opening, a standard blind flange is preferred (lower cost, no moving parts).
Blind Flanges (BL) are solid-disc pipe covers with no center bore, used to terminate a pipeline, isolate a section for maintenance, or serve as pressure-test closures. They conform to ASME B16.5 (1/2" to 24" NPS) and ASME B16.47 (>26" NPS), pressure ratings Class 150 (285 PSI) through Class 2500 (6,670 PSI), with materials from A105 carbon steel to 16MnDR low-temperature alloy. The pressure rating of a blind flange equals the next-larger pipe size: a 12" Class 150 BL is calculated per ASME B16.5 sec 4.2 using the 14" gasket dimensions. They are the standard specification for piping-end terminations and pressure-test heads.
Source: ASME B16.5-2020; EN 1092-1:2018.
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