Cavitation article complete, Please Review

[yARIC008]

Well here it is
http://www.samantha.cc/cavitationartic.html

I'm not sure if I'm just supposed to give this to Mel, but either way, I'd like everyone to read it and make sure I have my information perfect. If there is anything people think I should add, let me know. Any grammar mistakes, lemme know.

I've checked everything best to my ability but i'm sure there is probably something I have missed. Once everyone puts in their two cents I guess Mel then can put it up on the tech articles and hopefully anyone with questions ever again will be able to get everything they need from there.

Only thing I really need to finish it off is the procedure of how to tell you have cavitation damage. There is a way such as getting which ever cylinder you are studying at BDC then putting pressurized air in there and gauging the leak and such. If there is an article out there, please someone let me know, and i'll put a link in there, or if someone feels they know what the procedure is and wants to write it all out, i'll include that too.

Anyways, hope you guys like it, I spent quite a few hours on it, and at least got it done ahead of schedule, woho!

Also, i should probably add more terms to the glossary.

 

[82fordtruck]

I can't get that link to work.

EDIT: Never mind.

 

[82fordtruck]

I like it. I like your format a lot, and think there is a lot of useful information there.

You do mention other types of cavitation, but fail to adequately explain them. Cavitation is caused from the boiling of the water, not a vacuum. When you reduce the pressure in something, by making it flow very fast, the pressure can drop below the vapor pressure, causing it to boil, and then return to a liquid form when the pressure comes back.

This is very much what happens on a boat engine, when the water flowing over the prop has to go very fast, the pressure on it drops. This is also what you hear when the faucet is barely on, and that whistling noise comes out, or when you crimp off a garden hose almost all the way, and that noise comes out if it.

This, however, is very nitpicky.

The only other thing I would change, and I know little about it, is to explain how the SCA helps.

Keep up the good work!

 

[82fordtruck]

I have been thinking about it, and the explanation for the boiling of the coolant is enough that many people may not understand it without a technical background, and it's such a minor detail, that for the audience, it may be better to leave it like it is.

I suppose this is a question for Mel.

I would like to know how SCA works.

 

[yARIC008]

I don't think boiling is the right term to use for these bubbles is it? Here is a small quote i found from another site.

"Cavitation is the formation of bubbles (voids, really--they're basically tiny vacuum pockets) in fluid under tension"

That's what happens here, the coolant becomes under tension because it is pushed away by the walls then yanked back. Then bubbles of vaccum form and then collapse. In my diagrams i didn't really talk about bubbles i just had one big area of vacuum form and then collapse. I kinda mentioned that it wouldn't happen that pretty but maybe i should mention vacuum bubbles.

Also, check out the question Q: What Chemical in the SCAs bonds to the metal walls?, does that explain SCAs enough, or should i talk about it more?

Maybe I should have just a question dedicated to just the question, How do SCAs function?

 

[yARIC008]

Just realized I should mention ELCs aswell.

 

[82fordtruck]

I don't even know what ELC's are. I run Cat ELC in my truck... guess I should.


OK, water boils at 212 degreed F at sea level. As you lower pressure, water boils at a lower temperature. Under a light vacuum, you can boil water at body temperature. I remember a lesson in High School physics discussing this phenomemon. It came right before phase diagrams. You look young enough to still get a headache thinking about that stuff, and be able to remember high school.

This is why cooling systems are under pressure. It raises the boiling temperature. Antifreeze is added to cause boiling point elevation/ freezing point depression. This is caused by impurities in the water, which allow it to not freeze at night or boil over in the summer.

These voids do have a lower pressure, but "vacuum" is technically the wrong word. This is a vapor bubble, caused by the boiling of the coolant that occurs at low pressures.

As I said, this is nitpicking, but I think it's what you wanted, right?

I do not know if you got your information at a truck website or a thermodynamics / heat transfer source, but I bet it makes a diference.

 

[82fordtruck]

Q: What Chemical in the SCAs bonds to the metal walls?

A: Molybdate and Nitrites are the chemicals in SCAs that bond to the metal walls and provide cavitation protection. Some SCAs from different companies may use other chemicals or one or other. Therefore once you start using a certain SCA you should keep using it instead of mixing various types. The most recommended is Ford's VC-8 and/or Fleetguard's DCA-4 because they provide the same protection and are able to mix.


I read the above quote, but it does not say HOW It happens. Why does this not act just like the water and cavitate as well?

 

[Cowboy_Customs]

I think the artical was very well detailed. I read the whole thing, every last word of it, and you did specificaly answer what it is about SCA's that helps. (the componants it is that bond to the cylinder walls to form like a little barrier)
A little Q little at the bottom with the rest would probably be a good idea.

My one thing that I belive should be added is just exactly how much should be added, I know you said 2 bottles, but how many ounces, or pints, or whatever. Perhaps, what ratio (amount of fluid SCA : 1 gallon of coolant) is a better answer, because that could also be applied to other larger, and smaller engines as well. Obviously it would be up to the owner to know just what the total coolant capacity his/hers motor, rad, and hoses, n accessories, the vehicle holds.

But other then my 2cents, AWESOME tech article!


:draw

 

[yARIC008]

Ah, good point about how much SCA to add, i believe it's one pint per 4 gallons, but i'll write that in there.

Also, i just updated it all a bit, i added a question about RDTs and ELCs and added those terms to the glossary.

Also, I'll make a question that specifically asks how SCAs work.

Also, about the bubbles, yeah, i see what your saying, I updated the caption in the last diagram picture, tell me what you think. I said a good example is when you shove your hand through water say in a swimming pool and see bubbles form, this is basically cavitation right? And also updated a little bit in the part that asks why are some engines immune.

If that hand through water example isn't good, any other good easy to understand examples?

 

[yARIC008]

OKay, updated again with what is the ratio of SCAs to coolant?, how to test coolant levels and how often?, and how do SCAs work what do they actually do?

 

[Agnem]

The job search has me pretty busy today, so I haven't had time to review the article yet, but I would not worry about the science of it all too much. Just try to nail down what the common belief is, and go with that. We want people to read the article and think "oh crap... I better go dump some SCA's in my truck right now", because that IS what they should do. We don't want them to get so confused in the details that they forget the purpose of the article. Good to post it here and get input from the experts so that it can be the best article on the net. When your ready for publishing, send me the web pages in a zip file.

 

[82fordtruck]

I would tend to agree with Mel, I am regretting saying anything at all. I guess it really does not matter in the big scheme of things.

However, i did, and here are some neat pictures and articles, from universities and such. #5 is incredible, make sure you see that one.


http://www.mcnallyinstitute.com/09-html/9-10.html

http://www.mcnallyinstitute.com/01-html/1-3.html

http://www.corrosion-doctors.org/Forms/cavitation.htm

http://www.flow3d.com/appl/lavalcavitation.htm

http://cavity.ce.utexas.edu/kinnas/cavphotos.html#cavhydro

http://cavity.ce.utexas.edu/kinnas/impeller/DSCN2377.JPG

http://cavity.ce.utexas.edu/kinnas/images/prop_cav.gif

http://cavity.ce.utexas.edu/

 

[yARIC008]

Yes, as long as people take the time to read the article they'll know exactly what to do. It addresses everything from "I've never treated my engine and this is the first i've heard of this, what do i do?" and "I've been done in by cavitation, how do i fix my engine and what are my options" to "how exactly do SCAs function"

Anyways, it's pretty indepth and i've tried to lay it out as neat as possible, so even is people don't have time to read the whole thing they can find their particular question and go right to it.

Mike, those links are awesome. I included one of them under the history of cavitation.

Still someone needs to find the procedure of how to diagnose cavitation

 

[budtoh3zo]

I think you got it really well done for the everyday guy