Tube Sagging in a New Heat Exchanger

What diameter tubes? What is the span between supports where the sag is seen? How much sag? Are you sure the tube isn't bent? How many tubes are sagging? All of them?

Why did you doubletriple post?

tube I.D is 20 mm and the span between supports is about 500mm. Not all the tubes, only some are sagged.

Then those that are "sagged" are probably bent, then.

What does the Client's specification have to say about bent tubes? If it doesn't then any desirable re-work is going to be at the Client's expense.

Why can't they be straightened or even replaced with straight ones? Why is this question even appearing on CR4?

That span sounds low. You say the tubes are 15 m long and there are 17 baffles and supports. 15m / 17 = 705mm and that's if the tubes go through all the supports. If these are segmental baffles, many of the tubes could have twice that span. Is there a pattern to the sagged ones, such as the ones with longest span between supports?

I suppose you could tell the fabricator to remove one tube and make sure the holes through the baffles and supports are aligned.

In any case, if the inability to see light through the tubes is just due to free sagging, that alone is probably not cause for concern. Hopefully, whoever designed the exchanger checked for potential tube vibration problems.

What will be the effect if not corrected and the exchange take in service at high temperature and pressure?

That is the concern.....It seems you have the support is alright. The sagging could be a number of possibilities, such as: Did it come that what from the manufacturer?

Did you put a Stop Work, Hold or Non Compliance Tag on it?

You have to also ask yourself this question, Is the Tube Damaged,? you really did not elaborate on this. And remember this is a blog, we can make all kind of recommendations, But,.... we are doing it blindly, It still comes down to it being your responsibility.

The exchange still under construction. tube sheet welding and fixed on the shell. But during tube to tube sheet expansion, in some tubes we where no able to see the light for other end and as per the manufacture this may happen in long tube heat exchange.

But may concern is the sagging due to an issue of the baffle and supporting plates or the tube it self.

Any suggestion to find the sagging acceptance or tolerance and in which code can I got it?

the other concern if we accept it as per the manufacture says ( this normal for long tubes) what could be the effect on the heat exchanger efficiency and tube life.

Straight or U-Tube Heat Exchanger?

Also, how much of a 'sag' as well as wall thickness of tube.

If there is no physical damage, a hydro-test may be all that is required.

May be a good idea if you go this route to have a boroscope to inspect the inside of the tube. (Seamless or Welded?)

Keeping in mind, that these are only options, the responsibility is still yours.

it is a straight seamless tube of 6 mm thickness.

tube physical damage is not suspected.

The forum still does not know what the Spec says on the topic, despite an earlier request for that information.

The OP doesn't know what the spec is either.

It would trouble me if I could not see through a tube due to deformation, no matter what the spec.

I don't know. But, as usual, I have an opinion.

Put some spacers between the tubes and keep them straight.

No, wait! That costs money, we can't do that. Let's fish for something to justify our sub-standard tubing.

<Bye>

Or he's looking for one of these.........

alzawamri,
Could you provide the following details for a deeep analysis?
Construction Code of Heat Exchanger
Complete material specification (ie, ASME SA 213 T11,T22, T23,T91..... etc)
Tube wall thickness in milli meters (including corrosion allowance)
Tube diameter in milli meters
Operating Temperature of Heat Exchanger
Operating pressure of Heat Exchanger
Any applicable International client specifications , Contract documents, NACE, API etc..

With a 20mm i.d. and 6mm wall, these should be quite stiff tubes. Is it really known that they are sagging, or could they be otherwise obstructed from a full view through?

If you say that there are a few tubes that are sagging, my advice is that you have a look at the both ends of the tubes that are sagging there could be a slight angle cut on the tube ends that may have occurred during the sizing of the tube,this creats the tube expander from not sitting square on the tube end during expansion this creats the tube to pull one side and that is most probably the slight sag that could be seen other wise one of those tube holes on the plate could be slightly out or bored on a slight angle.