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Discussion Starter #1
I just stumbled over something new to me, "rubber" valve balls. It sounds great, giving 100% seal, wich very often isn't the case with steel balls. I suppose the problem really lies with valve ballseats not beeing perfect ;-) Also, these balls are lighter, and supposedly operate much quicker. Does this improve efficiency?

I've ordered the rubber balls from www.knupfershop.de , and I willbe trying them out next week. Only problem is, my Aster uses 3mm and 4mm balls, but Knupfer only offers 3,1 and 4,7mm balls. The "rubber" material is called "Viton", I think it's a trademark, and handles heat, steam, oil etc

Has anyone else already tried this? Where did you get them?
 

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Posted By Pauli on 02/23/2008 7:40 AM
I just stumbled over something new to me, "rubber" valve balls. It sounds great, giving 100% seal, wich very often isn't the case with steel balls. I suppose the problem really lies with valve ballseats not beeing perfect ;-) Also, these balls are lighter, and supposedly operate much quicker. Does this improve efficiency?

I've ordered the rubber balls from www.knupfershop.de , and I willbe trying them out next week. Only problem is, my Aster uses 3mm and 4mm balls, but Knupfer only offers 3,1 and 4,7mm balls. The "rubber" material is called "Viton", I think it's a trademark, and handles heat, steam, oil etc

Has anyone else already tried this? Where did you get them?


Pauli,
  I've replaced all of the SS check valve balls in my Aster Hudson with Nirtil balls supplied by Diana and Tom Eaton of Sulphur Springs Models.   I don't remember the size of each ball offered (three sized offered when I purchased) but I can tell you that the middle size ball was a perfect replacement.  Since I made this change I have not had a check valve or whistle valve issue.
  One last thing, I only replace the check valve balls on the boiler.  I didn't make the changes on the tender pump.  If I have a stuck or leaking ball problem on the hand pump, I find a shot of white vinegar thru the seat cleans up any deposits without a problem.
  Hope this helps.
 

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Hi 
Just make sure the material is rated for steam and temperature. There is  a material (I can't remember which one) that is used for "O" rings which when exposed to high temp. turns into a gooey mess which is highly corrosive. I remember reports of people having to have fingers amputated due to this.
Regards,
Gerald 
 

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Nitrile is perfect for the job, whatever you do though DO NOT replace your safety valve SS balls with Nitrile to stop leaks!

DM-KOttawa
 

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Hi Pauli,

As mentioned Nitrile Balls are perfect for Asters I have changed all mine in my Asters including my new 9F if you need the 3mm they are 1/8th and the 4mm 5/32nd they will be 10 thou bigger but that will not be a problem :D.

Viton Balls are different but with the low pressure of our locos you can use them as well. If you also want to try the Nitrile Balls you can get them here http://www.pollymodelengineering.co.uk/index.asp I know there UK based but they will post.

As the ealier post says DO NOT fit these into a safety valve.

Tony
 

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Discussion Starter #6
Thanks for the tip Tony! Have you had any clear experience as to the benefits of "elastic" valve-balls?

(Living in Sweden, I've only experienced some US companies that either won't or can't send abroad ;-)
 

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Hi Pauli,

Sorry I thought you were in the States, contact Polly if they do not want to send them I'll purchase them and post them to you PM me off line.

Although I have never had problems with Stainless Balls after changing them in my Aster Battle of Britain they are noticably better and she is using less water. At the moment I have had no problems and get far better performance from the water system as a result. You'll be amazed at how much further open the by-pass valve is when pulling an average load.

Tony
 

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Pauli,
according to my material sheet nitrile and Viton have about the same hardness, though Viton is superior at higher temperatures. It is mostly used for high quality seals in industrial applications. If you purchased your Viton balls from Knupfer, you can'y go wrong. They have 30+ years of experience with life steam (second generation family business) and are the founders of the famous Sinsheim indoors live steam event.
Regards
 

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Discussion Starter #9
I exchanged all steel balls for the viton balls today. It works fine to use the 4,7mm balls from Knupfer to replace the original 4mm balls from Aster. The hand- and axlepump ball seats are more than 5mm diameter, so the balls can move completely free.

The most important valve ball to exchange, has to be the feedwater valve on the boiler. I figure one probably looses steam this way with a steel ball. So steaming up should go quicker, and running efficiency should also improve.
 

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Discussion Starter #10
WARNING! Replacing the original 4mm Aster stainless steel balls with larger 4,7mm probably requires shortening upper and bottom banjo bolts on axle pump with 1mm - else the pump will not pass water in any direction! As I wrote above, valve seat diameter is enough. Also, I had no problem with the tender bfeedwater pump!

I may be simpler if you get the above mentioned correct diameter nitrile instead... ;-)

However, this simple uppgrade, changing to slightly flexible viton or nitrile valve balls, still remains really worthwhile in my opinion!!!
 

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Pauli

Of course, there is nothing wrong with regular stainless steel ballls in the axle pumps of engines. Aster designed the axlepump on the P8 to have the correct tolerances when using SS balls. Why replace the balls on the axle pump of a new engine? Surely you couldn't have determined that the pump wasn't working efficiently since you haven't run the engine more than once, and that was without a load to test the delivery of the pump. Perhaps you should test the engine beforehand using OEM parts, instead of modifying the axle pump seat tolerances.

On engines that I have worked on, Stainless steel balls work just fine with no leaking, I cannot claim the same success with nitrile balls, as I have had numerous fluke balls than would not seat properly. Seating a SS ball is not all that difficult, so long as you have a sacrificial ball to give a good whack and create an impression on the seat.

Still, although I am old fashioned in the way of water delivery, please do report your findings with the resized rubber balls.
 

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Discussion Starter #12
I agree that the engine most likely works "fine" = with normal efficiency. This is after all a proven technology.

However, it goes wiyhout saying, that a somewhat less heavy / lighter ball works quicker. And, a slightly soft ball will give a tighter seal. A lot of people who have changed, say they will never again use steel balls. And in a lot of other places, soft materials are used to give superior seals - like O-rings.

In any case, the upgraded water-system works very well. I'm now into my 3rd running hour, and I'm pleased.

Before re-mounting the the axle-pump, after shortening the banjo bolts, I tried to blow or suck air through the pipes - closing action even with very little force (=slow driving?), was immediate. And seal was really 100% :)

In a few years, I expect these balls will have replaced most steel valve balls.
 
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