Support plate (baffle) - floating tube sheet heat exchangers 1

[Mandalore]

Hi!

Could anyone explain me, why the support plate (the baffle next to the floating tube sheet) in floating head heat exchangers (for example BES TEMA type) has usually cut out piece of material? Not like standard segmental baffle, just for example small square inside the diameter of the support plate. Is it necessary? Why can not it be done as a full diameter plate (baffle)?

Best regards!
Dawid

 

[SnTMan]

Mandalore, it can be done as a solid plate, but normally has the cutout to prevent a stagnant area between the support plate and the tubesheet.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Mandalore]

Mike, thank you so much for the answer.

So the only result of the construction without window in the support plate will be reduction of the heat exchange area equal to the outer surface of all tubes between the support plate and the tubesheet, right?

Regards,
Dawid

 

[SnTMan]

Yeah, but it also possible that any solids in the flow can accumulate in the dead space.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Mandalore]

Reffering to you experience, what will it cause? Anything special? Or maybe more difficult cleaning during downtime?

 

[SnTMan]

Yeah, could cause more difficult cleaning. You should understand that my experience is on the design / fab side, not operations though.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Mandalore]

Anyway thank you one more time for your answers.

Regards,
Dawid

 

[EdStainless]

It is important to have circulation because any fouling could prevent the floating tubesheet from moving, and then everything is in trouble. There are various styles of cutouts, probably each mfg has his own favorite.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

Deposits are frequently a cause of under deposit corrosion.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[SnTMan]

Excellent additions, Ed & IM

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Mandalore]

Thank you for the information.
I would like to go one step further: I have found a few information that the window in the support plate is mandatory for floating head but not necessary for U-tubes. I have found a few drawings as well where the U-tube budnle has solid support plate. What is the difference between these two solutions, excluding issue which EdStainless described (preventing of floating). In my opinion fouling and UDC probability is the same for U-tube and floating head.

What do you think about it?

 

[marty007]

Just to throw it out there, I have also seen many floating head heat exchangers without the kind of support plate you're mentioning.

Taking this back to the basics, can anyone shine a light on the benefit of such a baffle? Why is it there in the first place? Why not just shorten the tubes a little and locate the tubesheet where the last baffle would have been?

 

[SnTMan]

Well, hard to generalize, so many different services and owner preferences, but:

The floating head support plate is generally used in an exchanger with a removable shell cover, and its job is to support the floating end of the bundle when the shell cover is removed. The floating head must extend from the shell so the bolting is accessible. A floating head exchanger may also not have a removable shell cover, and in this case the floating head support plate is generally omitted.

The support plate in a U-tube exchanger is there to support the tubes, all of them. It is generally used when the shell inlet / outlet nozzle is located ahead of the U-bend tangent. In this arrangement the U-bends are often considered ineffective in the ratings calculations. When the I/O nozzle is located beyond the bends, another type of U-bend support is often used either a strip type support or a drilled plated fitted to the U-bends themselves.

Now, back to Mandalore's last post, I feel the same considerations with stagnant areas apply as well, and it is generally my practice to cut the U-bend support top & bottom, outside the tubefield of course.

Regards,

Mike

An afterthought: An floating head exchanger must be a T-Type, not an S-Type to use a non-removable cover, the entire floating head must fit thru the shell. Packed floating heads are a different animal altogether.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[marty007]

Mike,

Thanks very much, I hadn't considered the aspect of supporting the the tubesheet when the shell is opened. Learn something new everyday!

Cheers,
Marty

 

[SnTMan]

marty007, sure, glad to share the little I know

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

A lot of explanation of "support plate" is in TEMA.
Also help to extract and insert the tube bundle in the shell.

Regards
r6155

 

[ashaykadam]

How much should be the extent of cut out in Support Plate for Floating Head Heat Exchanger?
Is there any criteria regarding % open area as per TEMA or Good Engineering Practice?

Ashay Kadam
Mechanical Engineer
India.

 

[r6155]

I use solid support plate to reduce unsupport tube span and avoid vibrations.

Regards
r6155

 

[SnTMan]

ashaykadam, I am not aware of anything formal on that, but the usual practice I am familiar with is to size the cutout such that 3 to 5 tubes in any direction about the periphery of the tubefield are captured by the support plate.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand