unexpanded & expanded length of tube totubesheet joint

[212197]

in tube to tube sheet joint, certain unexpanded length is maintained. What is the purpose of keeping unexpanded length? What would happen if entire length is expanded except the end portion at shell side where if tube is expanded,it may get damaged.

 

[SnTMan]

212197, tubes are often expanded full depth of tubesheet less 1/8" or so to avoid the damage you mentioned. In my class of work this is routine, but costs a bit more than partial expansion. To me, that is money not worth saving

As regards Part UHX, shallower expansion depth can increase calculated tubesheet thickness.

Regards,

Mike

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

 

[212197]

pl. see the attachment. I want to know the reason of keeping 9 mm unexpanded length as shown in the attachment. What would happen if there is not such unexpanded length?

 

[Bokkel81]

Dear 212197,

Are you welding before expanding or expanding before welding?

When you expand the connection after welding, the 9mm free from weld secures that the amount of mechanical loading on the weld due to expanding is minimal.

 

[SnTMan]

212197, often for a welded joint the tube is lightly rolled to set the tube, then welded. This allows gases generated by welding to exit the joint on the shellside, helping to insure a sound weld. The tube may then be fully expanded, except for a margin at the weld itself and at the shellside.

This is what your detail appears to show.

Regards,

Mike

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

 

[212197]

pl. note that the welding is only at starting end from channel side (0.6 mm x 45 degree).Tubes are light rolled then welded & then expanded. On shell side there is no welding. You may refer attachment.

 

[SnTMan]

You don't want to full expand across the weld, it can damage (crack) it. I admit I've never seen this exact detail, the light roll portion is very shallow, but still, the foregoing applies.

Regards,

Mike

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

 

[212197]

based on above posts, I understand that the only purpose of keeping unexpanded length is to avoid transfer of load while expansion on the weld & thus avoiding potential damage in the weld.

 

[Bokkel81]

As I mentioned before, if you expand the tube next to the weld you will get a mechanical loading on the weld which can damage you weld. When you expand the tube is plastic deformed, the tube becomes flatter and a bit longer. So when you expand the tube next to a weld there will be a chance of cracks in the weld due to mechanical loading.