Extracting bundle of floating head heat exchanger 3

[Stefan2211]

Dear All,
we are facing the problem that we can't remove the bundle of our horizontal shell&tube heat exchanger. Weight of bundle is 9t. Design floating head (drawing attached).

Problem: hx has severe fouling and is leaking. Leaks are expected to be caused by uneven thermal expansion due to debris collected between the baffle plates and reducing heat transfer (pic), mechanical stress as we have non corrosive fluids (hydrocarbons).

Assumed reason that bundle stuck in the shell:
Solids (coke) has has settled down at the botom of the shell between the baffle plates (high and tolerance of baffle plates to shell is to small. Bundle can't be moved at all.
We tried to pull with 16 t forklift, used hydraulic jack at floating end to push it and to break it loose - no success. There might be also a deformation of the shell due to uneven heat distribution since we expect a lot of residue (coke - pic is from different unit) has settled at the bottom so free tubes have a different thermal expansion than the covered tubes.Chemicals doesn't work as coke is quite inert to most common used chemicals

We will try once again with larger hydraulic jacks to break the bundle loose and then pull (see right side of marked drawing). If that fails we will need to cut the shell. Red marked cutting of a window is not suitable acc to the vendor as the shell will collapse once the section is welded back (heat impact and shrinking - many attempts failed with other clients). They agreed to follow the green marked strategy to cut the shell in 3 pieces. But even then rewelding will be a challenge. Please note that only the pic with tubesheet (leaks) is the particular unit. The other pics are from an other unit but we were able to extract the bundle. Any suggestion? Thanks in advance

 

[pierreick]

Hi,
Let you try ultra high pressure cleaning , you can use the nozzles at the bottom of the HX to introduce the gun and the hose.

Pierre

 

[Stefan2211]

Pierre, we use normally 15000 PSI hydro jetting but you can't clean the shell side without extracting the bundle first. You would only reach the 1st baffle plate section. The debris is basically like hard coal.

 

[georgeverghese]

Reminds me of Hell on Earth days at my first job 35years ago with maintenance crews screaming blue murder having to deal with bad actors in the plant during an outage - blocked heat exchangers, tripped compressors, DEG, furnace explosions. Those were happy days. Good luck with the hydraulic jacks, Stefan - SAFETY FIRST. Looks like a TEMA AET HX.

 

[LittleInch]

So what can you remove?

Can you remove the whole thing or at that second set of flanges?

Can you drill as et of 1" holes and add screwed in nozzles to jet out coke or maybe even a set of say 4" coupons to get some mechanical cleaners in there. if you do this just in front of where the tube supports / baffle plates are would be a good place to start.

Flood the shell with lubricating oil (thin) and let it soak in for a while?

whatever you do please let us know how it goes - looks errr "interesting".

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Stefan2211]

Hi George, lol.......thanks for the your encouraging comment. Yeah it is still the rest of the coke we produce 2 years ago and lst year when the EDG failed to kick in after power failure. Shutdown since January......Even if I manage to pull the bundle I still have to find the cause of the > 13 leaks and how to fix it.

 

[Stefan2211]

Ok LittleInch some pics as fun part even though I still hv no idea how to deal with it. I soaked with diesel, no success, I used chainblocks and forklift to pull with an impact but not 1 mm moved.I used 160 t crane as fix point and a 16 t forklift.......no chance. The coke residue basically were up to 20 micron fine solids which agglomerated when solvent was removed and is became solid rock. Hydro jetting an drilling was necessary for the tubes. Some tubes took hours to clear. But now I need to get the bundle out to clean the shellside and investigate the cause of damage. The attached pics are basicall the downstream hx which we were able to pull. Enjoy the pics.........
Btw. I was thinking of putting it vertically on the tube sheet and pull the casing like a sleeve just to break it loose. But it is also an expensive job as eqipment etc is difficult to get here in Batam island. It is also not the safest way to stand it up.

This was the first trial to pull and set it on the scafflolding

This was second attempt with tightening the strut bolts and press it into the shell (from floating end). 4x4 was bent and we used small hydraulic jack....Failed

This is a leak and it looks tube is torn on the circumference about 270 Deg. Th end shows the coke blocking the tube. Please note, this is 25.4 x 2 mm SA179 and we hv no corrosive fluids and pressure is below 6 bar.
So it can only be thermal stress due to expansion problems ..

 

[LittleInch]

Can you roll it along its axis through 180 degrees?

Then hammer the daylights out of what is now the roof? Basically use its own weight to peel it off the surface just enough to pull it out?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Stefan2211]

I was thinking about it too but such rolling unit is probably impossible to get here beside the fact that I rather think its a mechanical problem with the baffle plates and a deformation of the shell or bundle.

 

[LittleInch]

Can't you lay it on some large timbers where you have no nozzles around the circumference and just roll it over using a crane or may a dozen people and some wedges?

It probably is a mechanical fit issue, but worth a try to use its own weight to free it from the surface tension and adhesion.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Stefan2211]

Well, not easy but before cutting we might need to look into it again. An island is always an issue for equipment supply

 

[MJCronin]

Nothing lasts forever ....

I suggest that you perform a cost study and contact a TEMA fabricator about a complete HX replacement or retain the channel and consider a replacement of only the bundle and the far side head

If you are forced to chose between replacement of the entire bundle or performing extensive tube cleaning, replacement and repair, then the cost of complete replacement may not be much different.

Bundle replacement also has the benefit and peace of mind of a brand new unit and the assurance that you will not find yourself in the same clogging predicament a year of two from now!!

There may also be some benefits from some design improvements made to a replacement unit (larger tube spacing or a different tube pattern ?) Perhaps even some ports added to the shell for periodic spray clean out ??

Oooops ... I forgot .... your boss just said that there will be no HX replacements !!! ..... Why ?.... Because there is no money in the budget and he said so !!!

Please keep us in the loop and tell us of your final fix

MJCronin
Sr. Process Engineer

 

[Compositepro]

One possible approach is to attach vibrators to the tube sheet and saturate the deposits with a penetrating oil (oil and diesel mixture). The idea is to get the solid deposits to fluidize. Pull periodically, not constantly, until things break loose. This will take some time. When you get some movement, it is often best to alternately push then pull, so you do not keep compacting the deposits.

 

[Stefan2211]

Thnks Compositepro,
Such equipment is not available here especially during covid logitic also difficult.

 

[georgeverghese]

Company managers at my old plant, after some cases of equipment thermal failure due to lack of cooling water resulting from failure of emergency DEG to start up on total power failure, decided to increase the frequency of simulated power failure test runs of the DEG to get better assurance that the DEG wont fail to start on power failure again. Seemed to have worked. The emergency DEG unit seemed to be almost permanently manned by a few mechanical and electrical maintenance men.

 

[Stefan2211]

Hi MJCronin,

Yes new unit but..........as you know
pipe material from Japan, Korea or Europe 2-3 months ex works
building it 3 months...........No budget ..no time either. So need to get plant running by repairing and replace unit asap.

 

[Stefan2211]

George, it was an internal issue knowing that the EDG does not kick in in auto mode due to some MCC issues but not informing and rectifying the problem.

 

[Stefan2211]

Update on cleaning process Blue tube have been found leaking
Red tubes are blocked and need manual drilling. Hydrojetting 15000 psi cant get it out
1. pass is solvent vapor in tubes - 2. pass is condensate (last 4 bottom rows).

Will take another week to get it cleaned in the tube side.

 

[TiCl4]

Stefan,

Are there any higher hydrojet pressures available on your island? 15,000 psi is low for hard, asphalty deposits. I’m not surprised it is ineffective. You would be better served with 40k, preferably 55k lancing.

 

[Stefan2211]

TiCl4, unfortunately not. And during covid is is all more complicated to get things in and out. Have you had experience with 40k pressure?