A flange blind plate is a flange assembly used to close the end of a pipe or the interface of a device. It has no central through holes and connects it with a mating flange to form a complete seal, temporarily or permanently blocking the flow of media. Its core function is an isolated pipeline system, which is suitable for equipment maintenance, stress testing, system segmentation and other scenarios. It is an indispensable safety isolation device in industrial pipelines.
Model and standard
International common standards:
National Standard (GB/T 9123): According to the pressure level, it is divided into PN6~PN160.
American Standard (ANSI B16.5/ASME B16.47): Class 150~Class 2500.
European Standard (EN 1092-1): Type 05 (blind plate flange).
Common types:
Plate blind plate: solid circular plate, suitable for permanent closure.
8-word blind plate: One side is a blind plate and the other side is a throttling ring, which can be rotated and switched to the opening and closing state.
Spacer/Spade: Temporarily inserted into the flange to achieve isolation.
Core features
Absolute sealing
The design of no inner holes completely blocks the flow of the medium. The sealing surface (protrusion surface RF, ring groove surface RTJ, etc.) is pressed through metal or non-metal gaskets, and the leakage rate is approaching zero.
High pressure bearing capacity
The pressure coverage range is wide, up to PN160 (national standard) or Class 2500 (US standard), suitable for high-pressure steam, oil and gas pipelines.
Diversified materials
Conventional materials: carbon steel (Q235, A105), stainless steel (304/316L).
Special materials: Duplex steel (2205), titanium alloy (Gr.2), nickel-based alloy (Inconel 625), used for strong corrosion or extreme temperature environments.
Flexible adaptability
The outer diameter of the blind plate and the size of the bolt hole are exactly matched with the flange of the same specification. The valve or equipment flange can be replaced directly without the need to modify the pipeline.
Excellent temperature resistance
Carbon steel blind plates are suitable for temperatures of -29℃~425℃, and stainless steel blind plates can reach -196℃~800℃ (depend on material and heat treatment process).
Technical parameters
Project Parameter Description
Nominal diameter DN15~DN2000 (supports non-standard customization)
Nominal pressure PN6~PN160 / Class150~Class2500
Applicable temperature -196℃ ~ +800℃ (adjust according to the material)
Sealing surface form: protruding surface (RF), ring groove surface (RTJ), full plane (FF)
Surface treatment Anticorrosion coating (epoxy resin), mirror polishing (food grade)
Thickness standard: Perform according to ASME B16.48 or GB/T 9123
Application areas
Petrochemical: The interfaces of the reactor and storage tank are closed, and toxic media are isolated during maintenance.
Power system: boiler pressure test, steam pipeline sectional pressure test.
Shipbuilding: Temporary sealing of pipeline system during debugging.
Water treatment plant: The end of the pump station pipeline is blocked to prevent backflow pollution.
LNG storage and transportation: Safe isolation during maintenance of ultra-low temperature pipelines.
Selection suggestions
Type selection:
Permanent closure: Plate blind plate is selected, which is low in cost and reliable in sealing.
Need to switch frequently: select Spectacle Blind to enable opening and closing by rotating.
Temporary isolation: Use a combination of Spade + gaskets for quick disassembly and assembly.
Material matching:
Corrosive media (such as hydrochloric acid, hydrogen sulfide): stainless steel 316L or Hastelloy C276.
High temperature steam (>450℃): chromium molybdenum steel (15CrMo) or nickel-based alloy (Incoloy 800).
Sealing surface selection:
High-voltage system (Class 600 or above): Ring groove surface (RTJ) + metal ring pad is preferred.
Low-pressure water system: Protrusion surface (RF) + rubber gaskets can meet the needs.
Installation and maintenance
Installation specifications:
Clean the sealing surface to ensure no scratches, rust or particles remain.
The bolts are tightened in diagonal order in steps, and the torque value must comply with the standards (see ASME PCC-1).
The 8-character blind plate needs to be installed to prevent misoperation.
Maintenance points:
Check the bolt pretension regularly, and use a disc spring to compensate for thermal slack in high temperature working conditions.
When stored for a long time, apply anti-rust grease on the sealing surface and cover the protective cover.
Things to note
Safety risk: After the blind board is installed, the “blind board has been sealed” sign must be hung to prevent accidents caused by misoperation.
Extreme working conditions: ultra-low temperature (<-100℃) or strong vibration environment, it is recommended to use a necked butt-welded blind plate (WN Blind) to enhance structural strength.
