In the field of chemical engineering, there is a requirement that the length of the bolt should not be too long or too short, and the flange bolt should be left with 2 to 3 wires. For this part of the requirements, this public number has a simple introduction, see: Basic knowledge - Why should the bolt leave 2-3 wires
So how to determine the length of the bolt supporting the flange?
First of all, we definitely need to determine the thickness of the flange.
We can inquire the corresponding thickness of different types of flanges by referring to various standards. Here you can refer to GB/T 9124.1-2019 "Steel pipe flange: PN series". From this standard, we can obtain different types, different sealing surfaces, different nominal diameters and different nominal pressures under the thickness of the flange.
Secondly, we need to determine the thickness of the gasket between the flanges.
This in turn involves a series of standards, such as: GB/T 4622.1-2022 "Winding gaskets for pipe flanges Part 1: PN series" and so on. Of course, although the gasket has thickness requirements, its thickness will be reduced in the fastening state. Moreover, under normal circumstances, the thickness of the gasket is about 4 mm, so in order to quickly calculate the length of the flange supporting bolts, we can directly set the thickness of the gasket to 4 mm or 5 mm.
Then, you need to determine the length of the nut to be matched with the bolt.
This still needs to query the standard to obtain the required nut length, usually the standard to query for these two standards: GB/T 6170-2015 "Type 1 hex nut" GB/T 6175-2016 "Type 2 hex nut".
We can see that the nut length of a type 1 nut is about 0.8 times its large diameter. The length of a type 2 nut is approximately 1 times its large diameter. Therefore, we can quickly determine the length of the nut by the screw thread type of the nut, usually we choose 1 times the size of the nut.
In addition, we also need to determine the length of the reserved bolt.
Since our bolt needs to leave 2 to 3 wires after fastening the nut, it is necessary to determine the corresponding length of these 2 to 3 wires. We also need to query the corresponding standards, such as: GB/T 196-2003 "Basic dimensions of ordinary threads". From the standard, we can obtain the corresponding pitch of different types of threads, so as to calculate the length required for 2 to 3 threads.
Finally, we also need to determine the number of bolts and thread specifications corresponding to a flange. These two data can also be obtained from the standard GB/T 9124.1-2019 "Steel pipe Flanges: PN Series". The standard lists different flange types, nominal pressures, the number of bolts corresponding to nominal diameters, and bolt thread specifications.
After the above steps, we can calculate the length of the bolt required, the length of the bolt includes: the thickness of two threads, the thickness of the sealing gasket, the thickness of the two nuts, and the height of the reserved 4~6 threads.
The above calculation process is very complex and requires querying a large number of criteria. Moreover, the calculation process is complicated and time-consuming.
How to solve it? Coincidentally, in order to solve the query and calculation problems of flange matching bolts, this public update adds the query and calculation function of the number and length of flange matching bolts.
The new function is located in the flange model screen. By selecting the flange type, you can quickly query the number and length of bolts supported by the flange.
Thank you
