Tubesheet bolting - not using Nuts!!

[Nafierfani]

Hi all

I am working on a fixed tubesheet which is bolted to the flange of channel. We always have used nuts and stud bolts to fasten tubesheet and channel, but this time we are going to thread the tubesheet and remove the nuts.

Have you ever had the same experience? What is the risk? What is the difference in the calculation?

Thanks in advance

 

[SnTMan]

Nafierfani, some of the downsides are: You can only tighten the joint from the channel side. No problem, if no obstructions.

In the future, it may be difficult to replace a damaged stud, as it may be seized into the tubesheet. You should flat or square one end of each stud for wrenching on.

If threads in the tubesheet are damaged, it can be difficult to repair.

It is a poor practice, you should have a really good reason to do so.

Only difference in the calculation is to check thread engagement into the tubesheet.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[EdStainless]

As Mike said, people avoid threads in the flange or tubesheet so as to make future maintenance more straightforward. Replacing a stud is a lot easier than trying to repair threads in a tubesheet.

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P.E. Metallurgy, Plymouth Tube

 

[MatthewL]

Ditto both replies, and would like to add this: using a threaded tubesheet makes reassembly after pulling the channel more difficult and increases the risk of damaged threads on the tubesheet. Frequently, when the channel is slightly misaligned with the tubesheet, the resolution is to use a flange bar (tapered shaft) to align the holes, allowing the first bolt/stud to be inserted. If the tubesheet is threaded, the bar can damage the threads. It will also make lining up the bolt/stud more difficult, because instead of simply inserting the bolt, it must be threaded into the tubesheet.

Matt

Quality, quantity, cost. Pick two.

 

[r6155]

My experience (year 1985): M220 x 2500 mm 750 kg stud for Reactor Pressure Vessel-Nuclear-.

No risk with this design. See UG-43 (g)for tapped hole

Regards
r6155

 

[EdStainless]

If you do this you should have non-threaded holes to use for alignment.
Then you can hang the tubesheet off of pins while starting the bolts.

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P.E. Metallurgy, Plymouth Tube

 

[r6155]

Non-threaded holes to use for alignment are not necessary.

1) Install all studs in threaded holes, then install the head channel. All studs are used for alignment.

I worked several times with figure UG-40 (a-2) similar as mentioned in 1)

Regards
r6155

 

[EdStainless]

There are no studs, he is using bolts. So pins would help out installation.

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P.E. Metallurgy, Plymouth Tube

 

[r6155]

Bolt shall be tensioned with de nut, NEVER with the head.
Stud shall be used for threaded hole.

Regards
r6155