need to change the bolt length description

The bolt description is set from the Bolt Specification referenced in the Bspec attribute of the Piping Specification that contains your valve and flange.
The SPCO items in the Bolt Specification also have Detail text reference that I think you can edit to change the bolt description.

Change the actual length or the description of the bolting components?

If you have two sets of equal flange pairs but want different bolting you need to set the attribute BSEL on one set and add a BSEL selector to the bolt spec itself

Actually the description text is fine. only the length has to be changed. for example '110 LONG STUD BOLTS' is a description. i need to change the value 110. in new bolting its auto updated. so thats the problem.

yes. I tried changing the flange thickness but it didn't work in my case. so I will try setting attribute BSEL. please guide me the steps included.

Do you only need to change the bolt length for a single specific valve? Which means other valves of the same type will still have 110mm?

Then using BSEL is right way to go.

You will need to create a new SPCO item in your bolt specification. Your new SPCO item needs its Bltref attribute refer to a new SBOL item.  You can adjust the bolt length by modifying the Xtralength attribute of the SBOL item

If you want to change the bolt length for all of the instances of the valve in the project, then you need to edit the properties of the CATE of the valve.

May I ask what is the new bolt length from the current 110mm?

For a specific bore type flange connection wherever bolt comes in, I need to change the value. I will try the steps you suggest and will get back to you

110 should be changed to 95 in all 25MM bore flange bolts

I think it is a bit risky to modify something right now without understanding how bolt specifications works, because there might be unwanted effects.

Please read the following online AVEVA help article.

https://help.aveva.com/Aveva_Everything3D/2.1/ISOUG/wwhelp/wwhimpl/common/html/wwhelp.htm#href=ISOUG5.05.01.html&single=true

After reading the online AVEVA help about how bolting works, hopefully we will be able to assist you better.

THIRUNAVUKKARASU R said:

yes. I tried changing the flange thickness but it didn't work in my case. so I will try setting attribute BSEL. please guide me the steps included.

Since you said that you tried to reduce the flange thickness of the catalogue, but the extracted bolt length did not changed from 110mm to 95mm, then I think that 110mm is the minimum length in the Bolt table used by your Bolt specification, 

If you will add 95mm on the bolt table available length (or switch to a more appropriate bolt table that has 95mm length), then changing the flange thickness of the catalogue should now work and produce the desired 95mm bolt length.