Collapsed Heat Exchanger Tubes 1

[Matador]

We concentrate the solids from 35% to 65% before it gets burnt in the recovery boiler. Steam is used on the shell side to evaporate the water.

Last week we noticed about 20 tubes in one section (not in front of the steam inlet) had collapsed.

Does anyone have any ideas or know whare I can get some reference material about what could cause this to occur.



Thanks in advance.

 

[kyong]

Most possible reason I can think is that tube side was in vacuum. It could occur if tube side were blocked and tubes were cooled down.

kyong

 

[MortenA]

Kyong seems right on the mark.

Best Regards

Morten

 

[Matador]

We sent a video camera down inside the tubes and noticed that they are indeed collapsed. The tube profile is a like a figure eight.

Last year when we noticed that the tubes were plugged and couldn't pressure wash them. Now we know that the collapsed tubes prevented the nozzle from going all the way through.

This shutdown we used water and compressed air to clean the tubes before sending the camera inside. We noticed that the collapsed tubes looked like a figure eight. (ie the centers were collapsed.)

Has anyone expereinced a situation where the there was localized collapsing of tubes. In out case it seems to have occured a couple of feet down from a baffle plate.

Thanks in advance.

 

[butelja]

Unless special considerations and additional notes are added to the hx specification, the code rules may end up with a design where the shell operating at design pressure may collapse the tubes if they are at a low or vacuum pressure. To my knowledge, the code doesn't consider the external pressure acting upon the tubes. We always include a note in the specification to cover this where it may be a problem. Also consider the possibility of collapsing the tubes during the shell side hyrotest after fabrication.

 

[TD2K]

What tube diameter and wall thickness are we talking about Matador?