Eaten-up internals in X-changers 2

[harith07]

Hi,
What can normally be done if the baffles, tie rods, and partition plates are very badly corroded, totally useless, but the tubes are still in good condition? We are having turnaround currently and it only last for a month. I need to think of the most economical, easiest, practical and efficient way of holding the U-tube bundles together.
Thanks

 

[dcasto]

Change them to the same materials as the tubes? We tend to overlook these details sometimes, the non pressure containing parts. You need to study them the same as the pressure parts.

 

[Christine74]

It sounds to me like the tubes are alloy but the remainder of the internals are carbon steel.

If the tubes are in fact salvageable, you could saw cut the bundle behind the tubesheet, shortening them the tubes by an inch or two more than the tubesheet thickness, then replace the baffles with an alloy of a similar composition to that used for the tubes. Of course if the tubesheet is to be reused you would also need to extract the tube stubs prior to hanging the tubesheet.

This procedure would result in a small loss of surface area but potentially a large material savings.

-Christine

 

[rmw]

C-74,

Great idea except that there are tube cutters specially made for cutting tubes off right behind the tubesheet. It would result in a cleaner cut and less surface loss due to saw considerations and less clean up to the tubes. There are also tools for extracting the tube stubs. Any heat exchanger service/repair company should be able to do that part of the work.

rmw

 

[SnTMan]

harith07, it may be worth looking at just replacing the bundle. There are plenty of companies that specialize in this kind of quick-turn project.

Regards,

Mike

 

[harith07]

SnTMan,
If a bundle is to be replaced, a budget foreast has to be made way before the Turnaround. The problem is, the budget was not to fit replacing the bundle. I am just talking about modification that can last for couple of years until the next Turnaround, and until then we will surely be able to replace the bundle. It's all about dollars and cents.
Thanks

 

[SnTMan]

harith07, I undestand about the budget, I guess, but unless it's exotic materials, you might get a replacement for only a little more than your repair. Shop work is generally much cheaper than field work. If the unit is tight on surface, original performance might save the difference.

Well, we do what we have to do.

Regards

Mike

 

[deanc]

Depending on several things such as
fluid,pressure,time ....weld,weld-o-lets on the vessel walls at 180 degree locations. Thread thru small nylon or teflon rods between the tubes. Tye off and plug with bull plugs.