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Blind flange

Blind flange

Blind flange is a flange without holes in the middle , for sealing the pipe plug. The effect is the same as the welding head and the threaded cap, except that the blind flange and the threaded cap can be removed at any time, while the welding head is not. There are many forms of sealing surface, such as full plane, bump surface, concave and convex surface, tenon groove surface and ring connection surface.

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1  In the initial stage of driving preparation,during the strength test or tightness test of the pipeline, no Examples of blind plate application (3 sheets)
In the case of simultaneous operation of the connected equipment (turbine, compressor, gasifier, reactor, etc.), a blind plate shall be installed at the connection between the equipment and the pipeline.

2  When the device stops, if the pipe is still in operation, a blind plate is arranged at the cut off valve.

3  When the device is multi-series, the main pipeline from the outside of the boundary area is divided into one thousand sub-pipelines into each series, and a blind plate is arranged at the cutting off valve of each branch pipeline.

4  When the device needs to be repaired, checked or switched regularly, the equipment involved needs to be completely isolated, and a blind plate is set at the cut off valve.

5   When a process pipe (e. G. Nitrogen pipe, compressed air pipe) is connected to the equipment, the end plate is arranged at the cut-off valve.

6  Clean the low point of the equipment and pipeline, if the process medium needs to be centralized in the unified collection system, set up the blind plate after cutting off the valve.

7  Equipment and piping exhaust pipe, drain pipe, sampling tube should be installed behind the valve blind or wire plug. Non-toxic, other than materials not hazardous to health and non-explosive hazards.

8 When the installation is built by stages, there are interlinked pipes set up at the cut-off valve for subsequent construction.

9 Some auxiliary pipes that need to be completely cut off when the device is in normal production, generally, blind plates should be set up.

matters need attention

1. Under the premise of satisfying the technological requirements, the blind board is as few as possible.

2. The blind board must be marked normally on or off normally.

3. The position of the blind plate in the cutting valve, upstream or downstream, shall be determined according to the cutting effect, safety and process requirements.

4  Flange blind plate is not galvanized when used in oil medium system, hot galvanizing should be used in other medium system. The minimum weight of galvanizing layer of stainless steel blind plate is 610g / m ~ 2, hot dip galvanizing quality inspection is according to cb*/z343.

Manufacturing technique

Forging blind flange , casting blind flange , cutting blind flange.Among them forging product price is highest, medium plate is second, cast forging is lowest. Casting is the second most important process. The quality of forging and plate is good, casting and forging a little worse.

The difference of casting flange and forging flange from the production process

Cast flange, blank shape and size accurate, small processing, low cost, but casting defects (porosity. Crack. The internal structure of the casting is less streamlined (if it is cutting parts, the streamline is worse); the forging flange is generally lower in carbon content than the casting flange, less prone to rust, better in forging streamline, compact in structure and superior in mechanical properties to the casting flange; If the forging process is not proper, the grain size will be large or uneven, the hardening crack will occur, and the forging cost will be higher than that of the casting flange. Forgings can withstand higher shear and tensile forces than castings. The advantages of castings are that they can produce more complex shapes and lower cost, while forgings have the advantages of uniform internal structure and no harmful defects such as pores and inclusions in castings.


Forging blind  flange:the forging process is generally composed of the following processes: selecting high quality billet blanking, heating, forming and cooling after forging.Forging processes include free forging, die forging and membrane forging. In production,different forging methods are chosen according to the quality of forgings and the number of production batches.

Casting flange:the flange shape size is accurate , small processing, low cost, but has  casting defects (the hole ,the crack,the inclusion); poor streamline shape of inner structure of castings (even worse in case of cutting parts).

Forging and custting are the common manufacturing method of flange.Generally speaking, forging flange quality is better, generally through die forging production, crystal structure, high strength, of course the price is more expensive.

Cutting flange:cut out the disc of the inner and outer diameter and thickness of the flange directly on the center plate, and then process the bolt hole and the water line. The flange produced in this way is called a cutting flange, the maximum diameter of this flange plate width limit.

Manufacture standard

national standards:HG20601-2009,HG20602-2009 ,HG20622-2009.

Marine standard:GB/T4450-1995.

Mechanical standard :JB/T86.1-94,JB/T86.2-94.

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