A105N DRILLED BLIND 2

[engresague]

Hi,

Could you assist me about the considerations to take into account both technical and normative, for drilling and to thread an A105N blind flange existing at a pipeline end..??

The idea is to install an array of eccentric drain, because it is necessary to drill and connect a threaded pipe with check and ball valve. For drain water after hydrotest.

The pipeline is for regular gasoline at 8.6 bar (125psi) MOP.
Pipe API 5L Gr. B DN 12" Sch. 60
The blind is ASME B16.5 A105N DN 12" Class 150
The drain is proposed of pipe ASTM A106 Gr B Sch. 80, threaded with seal weld. Check and ball valve DN 1" rating 1500 SW.

Thanks in advance

 

[BigInch]

Never had a problem with making a 1" threaded hole for a drain in a 12" flange. It might take awhile to drain a pipe through a 1". Don't you just want to depressure? Might consider a plug valve for that rather than a ball, if you might want to regulate the pressure blow down rate.

 

[KevinNZ]

There is a table in B16.5 that tells you how large a hole you can put into a blind flange before the flange as to be full hub thickness. 1" in 12" is fine.

 

[LittleInch]

This has been looked at extensively - search on "hole in blind flange" or "tap blind flange" on this site or look at this one

http://www.eng-tips.com/viewthread.cfm?qid=371342

An off centre hole in a blind flange does not, officially, comply with ASME B 16.5. at which point you should calculate it according to ASME VIII, which usually tells you the blind isn't thick enough...

In reality people do it all the time and the key items to look at in B 16.5 are figure 11 and table 6.

Like ~BI says, it will take an eternity to drain a 12" pipe through a 1" tapping. Also you can't drill it right on the edge of the pipe - too close to the sealing face so there will always be some water left in it.

Far better to manufacture a proper test end and bolt that to the end of your pipeline with a 4" drain line inserted as a weldolet.

You talk about an " an array of eccentric drain". what does that mean - Lots of holes? How many?

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