Settled sediments in plate exchanger
Settled sediments in plate exchanger
(OP)
Hi!
We have several plates heat exchangers in our facility. In a closed circuit, runs treated water that cools an electric generator, and in an open circuit runs non-treated water, on counter flow.
Due to the high quantity of sediments in the open circuit, the thermal flow decreases almost every month and it is necessary to dismount the heat exchanger to clean all the settled sediments in the plates.
¿Is there any difference between stainless steel and titanium, just talking about the sediment settling? ¿Is there another way to control the water quality, besides chemical products or filters (¿coatings, etc?)?
The chemical products implies more, and strict ambiental controls, and about the filters, instead of dismounting the exchangers, we would need to replace filters continuously.
Thanks,
JuanMC
We have several plates heat exchangers in our facility. In a closed circuit, runs treated water that cools an electric generator, and in an open circuit runs non-treated water, on counter flow.
Due to the high quantity of sediments in the open circuit, the thermal flow decreases almost every month and it is necessary to dismount the heat exchanger to clean all the settled sediments in the plates.
¿Is there any difference between stainless steel and titanium, just talking about the sediment settling? ¿Is there another way to control the water quality, besides chemical products or filters (¿coatings, etc?)?
The chemical products implies more, and strict ambiental controls, and about the filters, instead of dismounting the exchangers, we would need to replace filters continuously.
Thanks,
JuanMC





RE: Settled sediments in plate exchanger
But, if designed well, changing filters can be cheap, quick and easy. Or, at least, easier than dismounting HX, seperating and cleaning plates, reassembling, leak checking, disassembling, repairing leaks, reassembling....
RE: Settled sediments in plate exchanger
But we're thinking about changing the characteristics of the plates, looking for a decrease of the "adhesiveness" (sorry, i'm not sure if it is the right word to say it) of the sediments, so we wouldn't need to change or clean nothing at all.
Thanks!
RE: Settled sediments in plate exchanger
i suspect that someone, likely a salesman, decided that compactness (i.e. exchanger size) was best. sorry, i should not guess . . .
best to determine particle size of the sediment material and then design and install a filter to remove all sediment material before entering exchanger. depending upon fluid temperatures, suspended minerals may precipitate from the fluid, thus be deposited onto exchanger surface.
treating the exchanger surface is a bandaid approach and may very well not resolve the problem.
either replace the exchanger, install a filter, or continue cleaning as is currently practiced. best choice is to install a filter as replacing the exchanger will only continue the same problem.
good luck!
-pmover
RE: Settled sediments in plate exchanger
htt
Take a look at the Auto-Klean line of metal edge filters.
http://www.cuno.com/industrial/gas.shtml
RE: Settled sediments in plate exchanger
I have heard about magnetic conditioners, so I thought there could be something similar to deal with our sediments.
Now, after i read more about the mag-conditioners, i've realized that those would be useless for our intentions.
I guess we must use the traditional cleaning ways.
Thanks a lot!
RE: Settled sediments in plate exchanger
RE: Settled sediments in plate exchanger
I suspect that someone sized the PHE's for a design with a lots of safety factor in the duty and the flows and in normal service they don't have enough water flow on the open water circuit side to maintain adequate velocity.
Check your design and see what can be done to maintain the design water flow on both sides of the plate.
On the other hand, PHE's make the best filters in the world if your water has particles in it larger than the flow passages between plates. If that is your problem, look at the links UncleSyd gave you and start there and get a good self cleaning filter to protect your Hx's.
rmw
RE: Settled sediments in plate exchanger
RE: Settled sediments in plate exchanger
Syd and rwm have it. Good self flushing pre-filters and higher flow velocities.
Stainless is almost immune to flow erosion, unless you have a lot of debris. Get the flow speed up.
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RE: Settled sediments in plate exchanger
When calculating for PHE type of heat exchangers, please do not use a fouling factor (as is done for shell and tube). But it might be better to take an overdesign of just a couple of percent on HTC (5-10%). In your situation, it might even help to take out some plates, if you have a lot of overdesign (Overdesign makes happen what you try too avoid, in case of a PHE).
The best way would be to calculate the exact right PHE, and then choose a PHE with same number of plates, inlet dimensions, width ect, but only with a longer plate (for example look at the APV or Sondex series).
As a solution for filtering, you can look at http://www.bernoulli.se/Eng/ This company manufactures self cleaning filters, which are used in combination with PHE's.
RE: Settled sediments in plate exchanger
Let me explain a little further our problem:
I'm talking about heat exchangers of a little hydroelectric plant (50 Mw). As I said before, there is treated water running by one path, and non-treated water on the other side.
The non-treated water cools the refrigeration water, which runs in a closed circuit, unlike the non-treated water. This one (non-treated) is taken from the discharge of the hydroturbine, so, the intake of this water is the same than the used for the turbine. There is a little dam, to provide the water, so, according to the surface-level variation, we have seasons with poor water quality and sometimes, we have very clean water (on high levels).
It's hard to have a "proper" HEx size, because the operation conditions are changing all the time (despite we have almost constant temperatures during the year, the capacity of the HEx changes).
The exchangers has Titanium plates, with nitrile gaskets. We're waiting for hydrologic studies of the sediments to know if there is biological growth or simple sediments over the plates.
The manufacturer suggest the use of sodium hydroxide or sodium carbonate to control the biological growth, or nitric, citric or phosphoric acid to control the common sediments (metal oxides, corrosion products, silt, alumina). Yet, the non-treated circuit is open to a river, so we can't use chemical products without having a proper environmental control, which is almost as expensive as dismounting the plates and wash them manually.
Finally, that's the problem!.
Thanks again to all of you, i'll keep on reading to find the best option, and looking for what would we need to use the chemical products.
JuanMC