Heat Exchangers and Super Heated Steam?

ok, one thing at a time,

Its used to condense superheated steam at 5 psi and 375 F and heat up water.

- sounds like your using it as regen

One thing to get the energy out of the steam, you have to condense it.

As far as 5 lbs of steam thats nothing, it's about 212 degrees.

whats the volume in lbs/hour of steam?

And your right getting that transfer is difficult, this is done by impingement the steam right onto the tube,

- As far as super heated steam

?????

- I do not know the flowrate of the water but the bundle may be undersized.

Whats the surface area?

- as far as life, 8 years may not be bad. have you had the water test for minerals and hardess, tube bundle may be fouling.

- As far as cracking,

1.) what type of HX is it, U-tube, counterflow.

2.) What type of stainless, (could be 304SS with what your said)

3.) is it ASME cert. with a "U" stamp.

4.) where is it cracking, give a clue to the actual cause.

5.) what the start-up procedure, do your run water, and then open the steam, could be thermal shock.

I think I covered it, but if not, others would post added info.

Your find this out, and we can come up with some answers i'm sure,

Design Flow rates of water and steam would be useful.

Is it really 110F water or is it colder than that?

what is the tube diameter?

Do the old tubes show any sign of fouling on the water side?

Is shall side baffled for multiple steam passes?

Are there any operrational pressure and temperature readings from both sides at inlet and outlet?

What kind of flow controls on either the steam or water? If steam is shut off, does the shell have a vacuum breaker?

Anyone else with curious minds?

"- sounds like your using it as regen"

must have started too early this morning posted by mistake, don't know where I got that from with the info provided, and the steam temperature is about 320 degrees not 212 or 375

What kind of steam trap is installed?

Any vertical lift for the condensate, or is it all downhill to a receiver or pump?

Stainless steel, heat and calcium = cracked stainless. check your condensate for calcides. Even calcium in insulation will cause this if it gets wet. We cracked up a 100 foot ss tower with 5/8" plate that had to be taken down in pieces.

calcium in insulation? I did not know that, I knew chlorides

The steam is going through the tubes??????

If yes then is wrong (inefficient). why???because condesate steam is at 220 F.

So if you have too much condesation then actually is like reducing the surface area for heat transfer. Also there is a possibility of water hammering through the passes (you mention four?)

On the other hand if you use steam at the outside of the tubes (on shell site) then the steam can removed more easier , with out flow restrictions or hamering

i replied 2 times but the matter did not print.????

What is your Question?

Is it water not being heated up to 180F? or Is it reasons for damage to heating coils of the heat exchanger or Is it Super heated steam?

The reason the water is not being heated up is because the heat exchanger has reached a "stall" conditions being temperature controlled becuse of either condensate lifting from steam traps/ wrong type & under capacity steam traps.

The coils have drastically water logged and resulting in excessive water hamering of both coils inside and condensate lines outside. Under these conditions there is extensive damage to heating coils and steam trap internals.

The only option is to take the steam trap (preferbly Ball Float thermostatic) ideally sized by gravity slope to a Packaged Condensate Power Pump if more than one Heat Exchangers involved. If only this Heat Excanger involved then remove steam trap and take the discharge of the heat excanger to the receiver of the condensate power pump. Install the Steam Trap at the discharge of the pump to return to overhead main.

As regards Superheated steam this is like gas and delays heating because it has to wait it it reaches saturation temperature before condensing.

This if not desuperheated will increase process heating time like in your case.

Prefer installing a de-superheater with Water Control Valve & temperature controller to spray water in fine mist to de superheat.

Ducon, you are right.

I think a wrong trapping system, wrong type and/or under capacity steam trap is the reason of the problem. Installing a new steam trap with the appropriate type and position, and maintaining the steam at tube side not shell side -as suggested by Guest- can overcome the problem of insufficient heating of water.

Asak & Thanks.

We've a lot of Dye Houses here and they all use Theis HT Dyeing Machines. All have Heat exchangers which are Temperatured-control with Control Valves and everbody lifts condensate from the steam traps. its like monkey see - monkey do type of a thing here. They copy what the other guy did and all land up with the same problem of water hammering, water logging & stalling of the heat exvchangers as he is experiencing.The condensate Power Pump is the the only solution if he wants to return his cndensate.

Thank you everyone for your input. It's helping out alot.

I dont think we have a steam trap for our heat exhangers. They just take steam in the shell and condense it and the water goin through the tubes gets heated up in the process. But our tube bundles get ruined, destroyed almost. River water runs through the tubes and superheated steam at 375 degrees F is being condensed in the shell. The cracking of the tubes is in all different parts of the heat exchanger. It has no pump also it just drains to our conensate tank. The steam comes in from the top, hits steel plates connected to the tube bundle and goes through three sections seperated by two baffles. The steam comes in from two different parts at the top on the right and left sides and the heat exchanger is split in the middle by a steel plate blank.

Is the primary purpose of this heat exchanger to heat the river water or to condense the superheated steam?

What is the quality of the river water? Is it raw, or do you run through a strainer, filter, or other water pre-treatment?

Where does the hot river water flow?

From your sketch, I would think have a U-tube bundle in the heat exchanger, and I think that tube fouling from hard water and river mud are the source of performance problems with water not reaching 180F. If the water needs treatment before using it in your process, I would try to relocate the treatment to be before this heat exchanger.

U are right. What is the quality of the River water? How hard is it?

Are the tubes ss 304/316 only or ss 304L/316L.

If ss 304/316 only then irrespective they are stainless steel rust will take place with the quality of non treated river water and this is where they are cracking.

If ss 304/316L then where they welded with Argon under controlled conditions?

There has to be an answer hidden somewhere or is he not aware of the exact type of tube material & its welding?

If he is taking as per his sketch direct to a condensate tank with no gravity flow then there will be water logging giving rise to silent hammering resulting in the cracking.

Did you try to increase the steam pressure?

It's not a U-tube bundle, it has a straight tube bundle, the water is directed by the end caps on the shell. The river water is strained, but that is all. The purpose of the heat exchanger is pretty much just to get some use out of our 5psi exhaust steam and to help warm up the raw water before it goes into our hot process softener. But super heated steam's heat transfer coefficient is not good and it is also hard on the equipment. I'm wondering if the super heated steam is the root cause for our tube bundles getting destroyed. And if so if it would be worth it to put a control valve system and a de-superheating station on the steam lines going into the heat exchanger to raise efficiency since saturated steam has a much higher heat transfer coefficient, but most of all to save our tube bundles. They are very expensive.

What is the diameter, wall thickness and material of the tubes?

Have you checked on a heavier wall thickness?

Suggest you go to Spirax Sarco site and check up their tutorials .

Also contact both Spirax & Armstrong and they may help you out.

That is an excellent site.

alrite thanks for your replys

the tube diameter is half inch made out of stainless steal, im not sure what grade and i dont know what the wall thickness is

How are the tubes destroyed? cracking, bursting, warping, plugged?

If straight tube bundle, is one end free to float, or are both end fixed to the shell?

If one tube sheet is floating, is the shell surface smooth enough to allow the sheet to slide back and forth? Any irregularities to cause the floating sheet to bind up and get stuck?

Both ends of the tube bundle are fixed and the tubes look like their bursting and cracking.

You've to contact your heat exchanger manufaturer or scan google and find out some reputable manufactuer to help answer your cracking problem. If both ends are fixed then the tubes are bulgeing and cracking. Try Armstrong International - they make tubular heat exchangers and they may answer the reasons.

Soory can't help you much now but do keep posted if you get the right answer.

Armstrong is good, so is Bell & Gossett div of ITT.

Fixed tube sheet with large temp differences has a lot of thermal expansion stress that has no place to go. I would guess either manufacturer would recommend a U-tube bundle or a bundle with the return tube sheet with a floating tube sheet.

How would a U-tube bundle help? Also how would a floating tube bundle help? I'm just curious. Thanks.

One end of the tube bundle is fixed to the tube sheet, whilee the other end is free to expand and contract with thermal changes. A heat exchanger with both ends fixed does not have this flexibility so the tubes are stressed more. The other option would be to determine the added tube thickness needed to withstand the stress, and I'm not that smart.

For you application with raw river water, the floating tube might be a better but more costly option. The tubes can be cleaned easily in place, U-tubes have a bend that is a natural spot to collect dirt and is difficult to pass a brush through.