Where is the blind flange placed? Principle

The principle is to achieve isolation, facilitate disassembly and assembly, and ensure reliable safety performance.

Of course, they are installed only where necessary, and they must be easy to remove. Plug plates are used at the ends of pipes, at the locations where instruments are sealed off, or at manholes; it’s essential that they facilitate maintenance work

There is a cross-system that needs to be added at the end where cutting is possible; in other words, the blind flange cannot be removed just because cutting isn’t feasible； There’s no need to mention ordinary blocking blind plates.

What the people above said isn’t clear enough – blind plates must definitely be installed on the pipes entering and leaving the boundary area, but should they be placed before the valve or after it? For the valve assemblies at the nodes of utility and process pipelines, blind plates may be required in some cases; moreover, blind plates on utility pipelines should be installed on the outside of the valves that are close to the main pipeline. Similarly, blind plates may also be needed at the inlet and outlet of certain equipment – should they be placed before or after the inlet and outlet valves? Is there anything that can be explained in more detail?

Principle: Blind plates must be installed on pipelines that need to be isolated.

Reply to 5# wangdp: Generally, when a device needs to be disconnected from an external system for maintenance, a blind flange should be installed on the flange located on the side of the device, at the cut-off valve that marks the boundary between the device and the external system. This is something that becomes most apparent during maintenance work

For blind ends of pipes, spare ports on equipment, etc., there are no special requirements – it’s sufficient that they serve to isolate and seal.

As for whether it should be placed before or after the valve, this depends on the system that needs to be isolated; generally, it is located at the outer end of the pipeline valve connected to the equipment, that is, at the front of the inlet valve in the direction of flow, and at the back of the outlet valve

Blind plates are used for isolation and cutting off. Due to its excellent sealing performance, it is generally used as a reliable isolation method for systems that require complete isolation. A blind plate is a solid circle with a handle, used for systems that are normally in an isolated state. The 8-shaped blind plate has an 8-shaped design; one end of it is a blind plate while the other end is a throttle ring, but its diameter is the same as that of the pipeline, so it does not serve a throttling function. The 8-character blind plate is easy to use: it should be used at the blind plate end when isolation is required, and at the throttle ring end when normal operation is needed. It can also be used to fill the gaps resulting from the installation of blind plates in pipelines. Another feature is that the indicator is obvious, making it easy to determine the installation status. For example, the boundary zone is used for isolation to prevent the medium from flowing in the reverse direction. Selection method The blind plate should be installed at the locations where isolation (separation) is required, such as at the equipment connection ports, in front of and behind the isolation valve, or between two flanges. It is generally recommended to use an 8-shaped blind flange ； Plug plates (circular blind plates) can also be used for one-time-use components such as suppression and purging. **Standards: Flat steel pipe flange covers (GB/T9123.1-2000), Convex steel pipe flange covers (GB/T9123.1-2000), Concave steel pipe flange covers (GB/T9123.2-2000), Tenon-and-socket surface steel pipe flange covers (GB/T9123.3-2000), Ring-connected surface steel pipe flange covers (GB/T9123.4-2000). Production standards: HG/T20592-2009, HG/T20615-2009, GB/T9123.1-2000, GB/T9123.2-2000, GB/T9123.3-2000, GB/T9123.4-2000, etc

HG/T 20570.23 Installation of blind plates