Protection of Packed Floating Tubesheet 1

[SnTMan]

Question for the Shell & Tube folks.

Has anyone ever used some means to protect the O.D. of a packed floating tubesheet (TEMA --W) during insertion of the bundle into the shell?

I'm thinking of maybe some heavy duty heat-shrink film wound around the O.D. or something similiar. Unfortunately clearance is small, 1/16" diametral at the packing flange. Not much space to work with

Thanks in advance for your suggestions.

Regards,

Mike

 

[TJOrlowski]

SnTMan,
Is there a reason the OD of the tubesheet needs protection? Do you just have a large diameter and very long bundle, and are worried about it dragging on the bottom of the shell?

What's the diametral clearance of the tubesheet throughout the shell? Is the shell pipe, or rolled and welded plate?

What about using a heavy lubricant, or maybe an applied PTFE?

-TJ Orlowski

 

[SnTMan]

OK, holiday out of the way, back to my crisis...

TJO, yeah the concern is marring the OD of the floating tubesheet, which is sealed with o-rings at the gland.

Cu-Ni TS, steel shell, shell is R&W, 28 ID, TS is 27 3/4 OD, clearance at packing flange is 1/16 diametral. 24 ft bundle.

For reasons I won't go into we were not able to make the baffle OD larger than the FTS OD and in fact as toleranced baffles could be 1/32 smaller. Who knows what as-built clearances are.

Right now, I am leaning towards padding the thing with a SALES ENGINEER.

In case that is not feasible, I am working on a plan B

Regards,

Mike

 

[TJOrlowski]

Well depending on how symmetrical your shell sections are, and how good the fit-up on the circ seams and clean the ID welds are, you have 1/8" radial clearance in the shell itself.

If you can put your O-Ring retainer or packing gland on AFTER the bundle is in the shell, that should make things easier. Length of the bundle is definitely an issue here.

Is the bundle fully assembled, with the tubes already rolled to the rear tubesheet? If not, what about putting the bundle in the shell without the rear tubesheet on it? Do you have room / clearance to put the rear tubesheet on after the bundle is installed in the shell? You'd just have to make sure the tube nest doesn't get twisted or mis-aligned somehow.

How high is the ceiling in the shop? We have what I call "the hole" which is 16 feet deep, which we use to remove tubes on retube jobs. Any possibility of installing the bundle vertically, or maybe standing the bundle up and sliding the shell over it?

If you have anything long enough you could use, what about making some "slide-rods" out of round bar, putting them THROUGH the bundle in lots of places, supporting it on each end, and then using it to guide the bundle through the shell.

At the end of the day putting something protective on the outside edge of the tubesheet may be your best bet. I feel your pain on this one. Just because it's easy to draw doesn't mean it's easy to assemble.

Hope it works out.

-TJ Orlowski

 

[rmw]

Sales Engineer --- Nah, too greasy.

Is there any lubricant that is not permitted - that would be considered to be a contaminant?

One assumption made here is that you have 1/8" radial clearance on each side. This assumes that the shell is perfectly round and that the weld beads are flush with the shell ID. I doubt either is the case. You may have some serious pushing (or pulling) ahead of you.

I think you are just going to have to figure out what lubricant is able to be used and grease it up pretty good. Sales Engineers are out.

rmw

 

[rmw]

And...

How far along into the design are you?

This may be too late, but I am very familiar with large Hx bundles which have to be drug into their shells (actually the shells are drug up onto the bundle) which have skid rails designed into the baffle supports. They are typically U-tube, so no tight tolerances to deal with.

Is it too late to design a skid rail or rub rail into the baffles?

rmw

 

[SnTMan]

rmw, no skid bars, etc and unfortunately too late to add them. Like you I doubt shell is perfectly round, however, welds are supposed to be ground flush.

TJO, I like the vertical insertion idea, however it is not usable by either us or the owner. Same for the idea of installing FTS afterwards.

Looking at attaching a "skid plate" or something similar to the FTS.

Thanks for the help.

Regards,

Mike

 

[WBH]

SntMan,

Seen this several times, heavy duty lubricants/grease, shrink wrap and even protective tape used for gasket surfaces. All of these failed to protect the surface of the machined hub. Even with grinding all internal welds flush, inserting templates with the same tolerances.

Check inside edges of nozzles and provide with a radius. Also check out of roundness at the nozzles, and ensure complete contour of the nozzle edges and weld to the shell, check with an ID template.

If possible rotate the shell to ensure no nozzles are in the bottom of the shell. Blow out or otherwise clean ID of the shell immediately before installing the bundle.

I would try some thin gasket material like garlock you can buy in a roll and cut to the necessary size. Then secure with shrink-wrap. Should provide some protection.

As others have noted above your shell is not perfect, minor deviations at different locations will cause problems. I don't like to see this design used due to this and other problems with the split rings and over tightening of the flanges deforming the hub along with other maintenance issues.

Let us know your results.

 

[SnTMan]

Situation is in flux....details tomorrow

 

[SnTMan]

What a mess.

To be brief: Job originally sold as replacement bundles, but to include "shipping shells". Shop insists shell needed to to pressure test shell side of bundles (air-soap test of tube joints), tube side to be hydro'd. Eng Mgr and Sales Egr make site visit to confirm dimensions, taking with them a tape measure. Field dimensions dictate the baffle OD to be as noted above, equal to FTS OD. Project Egr unable to incite any concern toward damage to the FTS during bundle install. Job proceeds.

Customer informs he intends, on reciept of bundles, to remove from shipping shell, clean and reinsert, pending need for bundles to be installed in equipment. Project Egr unable to incite...etc.

Job nears completion. Shop is alarmed that a real danger exists of damage to the FTS. Egr Mgr and Sales Egr take novel step of contacting customer, who informs bundle is fine crated. However shop insists test shell be retained.

Redesign: Cut off packing flange, add thin plate flange to shell end. Insert bundle using skid plate under FTS. Remove skid plate, fit packing flange over FTS, bolt shell, packing flange and test ring together using a common set of bolts. Air-soap test shell side. Replace test ring with test cover, hydro tubeside.

Not known is how customer is to insert bundle with out damage to FTS. His problem I guess.

Regards,

Mike

 

[Duwe6]

Thanx for the "afterwards" info. I learned something.

And liked the idea of using the Sales "Engineer" as an assembly softener with integral lubrication. I've been reliably informed that personnel left in vessels can be removed using a strong nitric/HF acid passivation solution. But not stainless steel belt-buckles. Guess what i wear during vessel entries?

 

[SnTMan]

Duwe6, glad you learned from this, not a total loss then

Regards,

Mike