{"id":1990,"date":"2026-09-01T21:56:09","date_gmt":"2026-09-02T04:56:09","guid":{"rendered":"https:\/\/www.songhaiflanges.com\/?p=1990"},"modified":"2026-09-01T21:56:09","modified_gmt":"2026-09-02T04:56:09","slug":"blind-flange-types-dimensions-specification-guide","status":"publish","type":"post","link":"https:\/\/www.songhaiflanges.com\/zh\/blind-flange-types-dimensions-specification-guide\/","title":{"rendered":"Blind Flange Guide: Types, Dimensions, RF Face, Tapped Blind Flanges, and Specifications"},"content":{"rendered":"

A blind flange<\/strong> is a solid flange used to close the end of a pipe, valve, pressure vessel nozzle, pump connection, or inspection opening. Unlike a weld neck flange or slip on flange, it has no center bore for flow. Its purpose is to block the line, isolate equipment, support pressure testing, or leave a safe connection point for future expansion.<\/p>\n

This guide explains what is blind flange<\/strong>, common blind flange types<\/strong>, carbon steel blind flange selection, RF blind flange<\/strong> sealing, tapped blind flange<\/strong> options, blind flange dimensions, and the key specifications buyers should confirm before ordering.<\/p>\n

What Is a Blind Flange?<\/h2>\n

A blind flange, also called a flange blind, blank flange, blind plate, or pipe blind flange, is a bolted closure plate with flange bolt holes. It seals against a mating flange with a gasket and bolts. Because it completely blocks the bore, it is used where flow must stop at the end of a piping section.<\/p>\n

Blind flanges are common in oil and gas, chemical processing, power plants, water treatment, shipbuilding, pressure vessels, storage tanks, skids, and industrial maintenance systems. A blind flange on pipe can be temporary for testing and maintenance, or permanent for a closed branch and future tie-in.<\/p>\n

Why Blind Flanges Are Important<\/h2>\n

A blind pipe flange looks simple, but it performs a serious pressure-boundary function. It must resist internal pressure, gasket load, bolt stress, corrosion, temperature, and sometimes external loads from connected equipment. If the wrong blind flange size, pressure class, material, or face type is selected, the joint may leak or fail inspection.<\/p>\n

For this reason, a blind flange specification should include more than the words \u201cblind flange.\u201d The RFQ should define the standard, size, pressure class, material, facing, thickness, bolt pattern, gasket requirement, inspection, and any tapping or custom machining.<\/p>\n

Common Blind Flange Types<\/h2>\n

Blind flange types<\/strong> are usually described by facing, material, standard, pressure class, and optional machining. The table below summarizes common options:<\/p>\n\n\n\n\n\n\n\n\n\n\n
Blind Flange Type<\/th>\nMain Feature<\/th>\nTypical Use<\/th>\nKey Buying Check<\/th>\n<\/tr>\n<\/thead>\n
Raised face blind flange<\/td>\nRaised gasket seating surface<\/td>\nGeneral steel pressure piping<\/td>\nConfirm RF height, gasket type, and class<\/td>\n<\/tr>\n
Flat face blind flange<\/td>\nFull flat sealing face<\/td>\nCast iron, ductile iron, low-pressure systems<\/td>\nUse correct full-face gasket where required<\/td>\n<\/tr>\n
RTJ blind flange<\/td>\nRing groove for metal gasket<\/td>\nHigh pressure oil, gas, petrochemical service<\/td>\nConfirm ring groove and RTJ gasket size<\/td>\n<\/tr>\n
Tapped blind flange<\/td>\nThreaded hole or NPT tap added<\/td>\nDrain, vent, gauge, testing, sampling<\/td>\nConfirm tap size, location, thread type, and pressure rating<\/td>\n<\/tr>\n
Large diameter blind flange<\/td>\nHeavy closure for large pipe sizes<\/td>\nPipelines, vessels, waterworks, terminals<\/td>\nConfirm ASME B16.47 Series A\/B or drawing<\/td>\n<\/tr>\n
Custom blind flange<\/td>\nMade to drawing or special dimensions<\/td>\nReplacement equipment, non-standard nozzles<\/td>\nProvide full drawing and inspection requirements<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Carbon Steel Blind Flange<\/h2>\n

A carbon steel blind flange<\/strong> is one of the most common choices for general industrial piping. Carbon steel grades such as ASTM A105 are widely used for forged blind flanges in oil, gas, water, steam, and utility service. They offer strength, machinability, availability, and cost efficiency.<\/p>\n

When specifying a blind flange carbon steel<\/strong> item, confirm the pressure class, temperature range, corrosion allowance, coating, gasket compatibility, and whether low-temperature impact testing is required. Carbon steel may need painting, galvanizing, or other surface protection in outdoor, wet, or marine environments.<\/p>\n

Steel Blind Flange vs Stainless Steel Blind Flange<\/h2>\n

A steel blind flange<\/strong> may refer to carbon steel, alloy steel, or stainless steel. Carbon steel is economical for many non-corrosive services. Stainless steel blind flanges are used when corrosion resistance, cleanliness, or chemical compatibility is more important.<\/p>\n

Common stainless grades include 304, 304L, 316, 316L, 321, 347, duplex, and special alloys. For chemical, food, pharmaceutical, seawater, or chloride-containing service, stainless steel or duplex blind flanges may be required. Material selection should follow the piping specification, not only stock availability.<\/p>\n

RF Blind Flange and Raised Face Blind Flange<\/h2>\n

An RF blind flange<\/strong> has a raised face sealing surface. The raised face concentrates bolt load onto the gasket area and is widely used in ASME steel flange systems. A blind flange raised face<\/strong> design normally mates with another raised face flange using a compatible ring gasket or spiral wound gasket.<\/p>\n

Do not mix raised face and flat face flanges without engineering review. Bolting a raised face steel blind flange to a flat face cast iron flange can overstress the weaker flange. Always confirm the mating face type, gasket style, and torque procedure before installation.<\/p>\n

Tapped Blind Flange and Blind Flange With Tap<\/h2>\n

A tapped blind flange<\/strong> is a blind flange with one or more threaded holes machined into it. A blind flange with tap<\/strong> can be used for drain connections, venting, pressure gauges, sample ports, hydrotest connections, flushing, nitrogen purging, or instrumentation.<\/p>\n

Common tap types include NPT, BSP, and project-specific threads. The tap size and location should be shown on a drawing. For pressure service, the remaining wall thickness around the tapped hole, thread engagement, plug rating, and sealing method must be checked. A tapped blind flange is not simply a standard blind drilled anywhere in the field.<\/p>\n

Blind Flange Dimensions and Size<\/h2>\n

Blind flange dimensions<\/strong> depend on the standard, nominal pipe size, pressure class, and facing. Important dimensions include outside diameter, thickness, bolt circle diameter, number of bolt holes, bolt hole diameter, raised face diameter, raised face height, RTJ groove dimensions, and any tapped hole details.<\/p>\n

Searches such as 4 blind flange<\/strong>, 6 blind flange<\/strong>, 3 blind flange<\/strong>, and 2 blind flange dimensions<\/strong> are incomplete unless the pressure class and standard are also known. A 4 inch Class 150 blind flange is not the same as a 4 inch Class 300 blind flange. A 6 inch ASME blind flange may also differ from an EN, DIN, JIS, AWWA, or custom blind flange.<\/p>\n

Blind Flange Specification: What to Include<\/h2>\n

A complete blind flange specification<\/strong> should include the following details:<\/p>\n

    \n
  • Standard: ASME B16.5, ASME B16.47 Series A\/B, EN 1092-1, DIN, JIS, AWWA, API, or customer drawing<\/li>\n
  • Size: NPS, DN, or exact custom dimensions<\/li>\n
  • Pressure class or rating: Class 150, 300, 600, 900, 1500, 2500, PN rating, or project rating<\/li>\n
  • Material: carbon steel, stainless steel, duplex, alloy steel, nickel alloy, or special material<\/li>\n
  • Facing: RF, FF, RTJ, tongue and groove, or special face<\/li>\n
  • Dimensions: OD, thickness, bolt circle, bolt holes, face height, and gasket seating area<\/li>\n
  • Optional machining: tapped hole, center hole, custom groove, counterbore, or lifting hole<\/li>\n
  • Inspection: MTC, PMI, UT, PT, MT, hardness, impact test, pressure test, or third-party inspection<\/li>\n
  • Surface treatment: anti-rust oil, painting, galvanizing, pickling, passivation, or custom coating<\/li>\n<\/ul>\n

    Blind Flange on Pipe: Installation Considerations<\/h2>\n

    Installing a blind flange on pipe<\/strong> requires the same care as any bolted flange joint. The mating flange face must be clean and undamaged. The gasket must match the flange standard, size, class, face type, and service conditions. Bolts should be tightened gradually in a cross pattern using the specified torque or tensioning method.<\/p>\n

    During hydrostatic testing, the blind flange may carry full test pressure. Make sure the blind flange, gasket, bolting, and mating flange are rated for the test condition, not only normal operating pressure. For large blind flanges, handling and lifting safety should also be considered because blind flanges are usually heavier than open-bore flanges.<\/p>\n

    Blind Plate, Pipe Blind, and Skillet Blind<\/h2>\n

    Terms such as blind plate<\/strong>, pipe blind<\/strong>, pipe+blinds<\/strong>, and skillet blind flange<\/strong> can mean different things depending on the plant. In some sites, they refer to standard blind flanges. In others, they may mean line blanks, spectacle blinds, paddle blinds, or spade blinds used for positive isolation.<\/p>\n

    If the application is process isolation for maintenance safety, confirm whether the project needs a standard blind flange or a line blank device. A spectacle blind or spade blind is often used between two flanges for visible isolation, while a blind flange closes the end of a line.<\/p>\n

    Common Misspellings: Blind Flang, Blind Flg, Bling Flange<\/h2>\n

    Search terms such as blind flang<\/strong>, blind flg<\/strong>, and bling flange<\/strong> are usually misspellings of blind flange. In purchasing documents, however, informal abbreviations should be avoided. Use the full product name plus standard, size, class, material, and face type to prevent mistakes.<\/p>\n

    For example, \u201cASME B16.5, NPS 6, Class 300, RF blind flange, ASTM A105, with 1\/2 inch NPT tapped hole at center\u201d is much clearer than \u201c6 blind flange with tap.\u201d<\/p>\n

    Choosing a Blind Flange Manufacturer or Supplier<\/h2>\n

    A reliable blind flange manufacturer<\/strong> or blind flange supplier<\/strong> should be able to confirm dimensions, material traceability, machining capability, inspection requirements, and documentation. For custom blind flanges, large diameter blind flanges, tapped blind flanges, and pressure vessel blind flanges, engineering review is especially important.<\/p>\n

    Ask whether the supplier can provide material certificates, heat numbers, PMI testing, NDT reports, surface protection, and packing suitable for export. For critical projects, third-party inspection and drawing approval before production may reduce risk.<\/p>\n

    Common Mistakes to Avoid<\/h2>\n

    Do not order a blind flange by size alone. Do not assume a slip blind flange means the same thing as a slip on flange. Do not drill a tapped hole in a pressure blind without checking wall thickness and rating. Do not reuse damaged gaskets during pressure testing. Do not mix RF, FF, and RTJ face types without confirming the mating flange and gasket.<\/p>\n

    Also avoid using a standard blind flange where a spectacle blind or spade blind is required for safety isolation. The correct isolation device depends on plant procedure and piping design.<\/p>\n

    Conclusion<\/h2>\n

    A blind flange<\/strong> is a solid bolted closure used to block flow, isolate systems, close pipe ends, and support testing or future expansion. Correct selection depends on blind flange type, material, face, pressure class, dimensions, gasket, bolting, and optional tapped connections.<\/p>\n

    Songhai Flanges supplies carbon steel blind flanges, stainless steel blind flanges, RF blind flanges, tapped blind flanges, large diameter blind flanges, pressure vessel flanges, and custom forged flange solutions. If your project requires a blind flange manufacturer<\/strong> with standard or custom capability, sharing drawings, service conditions, and inspection requirements will help the engineering team recommend the correct blind flange specification.<\/p>","protected":false},"excerpt":{"rendered":"

    Learn what a blind flange is, common blind flange types, carbon steel blind flange selection, RF blind flange and raised face designs, tapped blind flange options, blind flange dimensions, sizes, and specifications.<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[85,230,253,214],"tags":[1100,1106,1087,1094,1110,1109,1125,1084,106,1108,1119,1074,983,1120,1080,1082,1076,1118,1097,1103,1092,1096,1105,1104,1085,1099,1072,1079,1075,1077,1093,1098,1073,355,1111,1112,576,458,459,1116,1088,155,463,292,462,648,188,1113,1123,464,476,472,470,1124,941,1114,1095,1086,962,475,1121,1091,733,1122,1081,1089,1117,1107,1102,1101,566,565,578,461,465,1083,1078,1115,1090],"class_list":["post-1990","post","type-post","status-publish","format-standard","hentry","category-blind-flanges","category-product-guide","category-product-knowledge","category-technical-guide","tag-2-blind-flange-dimensions","tag-3-blind-flange","tag-4-blind-flange","tag-6-blind-flange","tag-ansi-blind-flange","tag-asme-blind-flange","tag-blank-flange","tag-blind-flang","tag-blind-flange","tag-blind-flange-asme-b16-5","tag-blind-flange-bolt-pattern","tag-blind-flange-carbon-steel","tag-blind-flange-dimensions","tag-blind-flange-gasket","tag-blind-flange-manufacturer","tag-blind-flange-on-pipe","tag-blind-flange-pipe","tag-blind-flange-pressure-rating","tag-blind-flange-raised-face","tag-blind-flange-rf","tag-blind-flange-size","tag-blind-flange-specification","tag-blind-flange-specs","tag-blind-flange-supplier","tag-blind-flange-types","tag-blind-flange-with-tap","tag-blind-flanges","tag-blind-flg","tag-blind-pipe-flange","tag-blind-pipe-flanges","tag-blind-plate","tag-bling-flange","tag-carbon-steel-blind-flange","tag-carbon-steel-flange","tag-class-150-blind-flange","tag-class-300-blind-flange","tag-custom-blind-flange","tag-custom-flange-manufacturer","tag-custom-forged-flanges","tag-ff-blind-flange","tag-flange-blind","tag-flange-dimensions","tag-flange-factory-china","tag-flange-inspection","tag-flange-manufacturer-china","tag-flange-material-selection","tag-flange-specifications","tag-forged-blind-flange","tag-hydrotest-blind-flange","tag-industrial-flange-manufacturer","tag-industrial-flanges-supplier","tag-large-diameter-blind-flange","tag-large-diameter-flange-manufacturer","tag-line-blank-flange","tag-mtc-certificate","tag-npt-tapped-blind-flange","tag-pipe-blind","tag-pipe-blind-flange","tag-pipe-flange-dimensions","tag-pipe-flange-manufacturer","tag-pipe-isolation-flange","tag-pipeblinds","tag-pmi-testing","tag-pressure-test-blind-flange","tag-raised-face-blind-flange","tag-rf-blind-flange","tag-rtj-blind-flange","tag-skillet-blind-flange","tag-slip-blind-flange","tag-slip-on-blind-flange","tag-spade-blind","tag-spectacle-blind","tag-stainless-steel-blind-flange","tag-stainless-steel-flange-manufacturer","tag-stainless-steel-flange-supplier","tag-steel-blind-flange","tag-tapped-blind-flange","tag-threaded-blind-flange","tag-what-is-blind-flange"],"_links":{"self":[{"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/posts\/1990","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/comments?post=1990"}],"version-history":[{"count":1,"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/posts\/1990\/revisions"}],"predecessor-version":[{"id":1991,"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/posts\/1990\/revisions\/1991"}],"wp:attachment":[{"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/media?parent=1990"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/categories?post=1990"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.songhaiflanges.com\/zh\/wp-json\/wp\/v2\/tags?post=1990"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}