Blind Flange

The formal name of the Blind flange is flange cover, and some are also called blind flange or pipe plug. It is a flange without a hole in the middle, used to seal the pipe opening. The function is the same as that of the head and the pipe cap, except that the blind plate seal is a detachable sealing device, while the seal of the head is not intended to be opened again. There are many types of sealing surfaces, including flat surface, convex surface, concave-convex surface, tongue-and-groove surface and ring connection surface. The materials include carbon steel, stainless steel, alloy steel, copper, aluminum, PVC and PPR.

Blind flanges are mainly used to completely isolate the production medium to prevent the production from being affected or even causing accidents due to the loose closure of the shut-off valve. Blind plates should be set at locations that require isolation, such as the equipment connection port, before and after the shut-off valve, or between two flanges. 8-shaped blind plates are often used; plug-ins (round blind plates) can also be used for one-time use locations such as pressure and purging.

Functions and classification of blind flanges

From the appearance, blind plates are generally divided into plate-type flat blind plates, 8-shaped blind plates, plug-ins, and gaskets (plug-ins and gaskets are blind to each other). Blind plates have the same functions as heads, pipe caps, and welding plugs for isolation and cutting. Due to its good sealing performance, it is generally used as a reliable isolation method for systems that need to be completely isolated. A plate-type flat blind plate is a solid circle with a handle, which is used for systems that are in an isolated state under normal conditions. The 8-shaped blind plate is shaped like an 8, with a blind plate at one end and a throttling ring at the other end, but the diameter is the same as the pipe diameter of the pipeline and does not play a throttling role. The 8-shaped blind plate is easy to use. When isolation is required, the blind plate end is used, and when normal operation is required, the throttling ring end is used. It can also be used to fill the installation gap of the blind plate on the pipeline. Another feature is that the marking is obvious and the installation status is easy to identify.

Production process

Generally divided into four types: forging, casting, middle plate cutting, and casting. Among them, the price of forged products is high, followed by middle plates, and casting is low. Casting is the second process. The quality of forging and middle plates is good, and casting is slightly worse.

Application parts of blind flanges

1. In the initial start-up preparation stage, when the strength test or tightness test of the pipeline is being carried out, if it cannot be carried out at the same time as the connected equipment (such as turbines, compressors, gasifiers, reactors, etc.), it must be installed at the connection between the equipment and the pipeline.
2. When the device is stopped, if the pipeline is still in operation, it is installed at the cut-off valve for various process material pipelines connected to the boundary area outside the boundary area.
3. When the device is multi-series, the main pipeline from the outside of the boundary area is divided into several thousand pipelines to enter each series, and it is installed at the cut-off valve of each branch pipeline.
4. When the device needs to be regularly maintained, inspected or switched to each other, the equipment involved needs to be completely isolated, and it is installed at the cut-off valve.
5. When the process pipeline of the pressurized pipeline, replacement gas pipeline (such as nitrogen pipeline, compressed air pipeline) is connected to the equipment, a blind plate is installed at the cut-off valve.
6. The low points of the equipment and pipelines are drained. If the process medium needs to be concentrated in a unified collection system, it is installed after the cut-off valve.
7. Blind flanges or threaded plugs should be installed behind the valves of exhaust pipes, drain pipes and sampling pipes of equipment and pipelines. Non-toxic, non-hazardous and non-explosive materials are excluded.
8. When the device is constructed in stages, blind flanges are installed at the cut-off valves of interconnected pipelines to facilitate subsequent engineering construction.
9. When the device is in normal production, some auxiliary pipelines that need to be completely cut off should generally be equipped with blind flanges.