BABBIT coating
05-31-2012, 02:44 PM,
#1
BABBIT coating
Dear all,

We intend to do babbit coating using a TAFA 04T equivalent wire on bearing surfaces that already have a layer of babbit on

Also, we would need to degrease the bearing surface prior to coating on it. Please advise until what temperature we should heat the bearings ( and should we do it from the outside, that is, shell side) ensuring no damage to the babbit layer, as the melting point of babbit is very low.

please also advise the pressure we should maintain whilst blasting ( we intend to use aluminum oxide 80 mesh size) to prepare the surface for application of bond coat followed by the layers of babbit. We are a little diffident in blasting the surface given the softness of babbit.

Help would be appreciated as there are a large number of bearings to be re- babbitted if we can do it right!

Regards

Shantanu Newar
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06-01-2012, 10:14 AM,
#2
RE: BABBIT coating
Hi Shantanu

interesting and challenging application, a couple short answers, maybe others will elaborate.

1. Its preferred not to coat Babbitt on top of existing babbitt whenever possible
2. If you must coat babbitt on babbit, typically a tinning layer of a low melting solder in paste form is applied over the existing babbit. Blasting existing babbit will embed the blast grit in surface. Preheat is a challenge as well
3. Not recommended, but common in some markets, is using GTAW welding with a 3.2mm babbitt wire and carefully build up babbitt by "welding"

Stephen James Booth
www.ipsteknokraft.com
www.teknokraft.com
Indonesia WhatsApp +6281905603262

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06-01-2012, 06:39 PM,
#3
RE: BABBIT coating
(06-01-2012, 10:14 AM)Stephen Booth Wrote: Hi Shantanu

interesting and challenging application, a couple short answers, maybe others will elaborate.

1. Its preferred not to coat Babbitt on top of existing babbitt whenever possible
2. If you must coat babbitt on babbit, typically a tinning layer of a low melting solder in paste form is applied over the existing babbit. Blasting existing babbit will embed the blast grit in surface. Preheat is a challenge as well
3. Not recommended, but common in some markets, is using GTAW welding with a 3.2mm babbitt wire and carefully build up babbitt by "welding"
Hi Stephen,

Thanks for your advice.

Point taken about the problems relating babbit over babbit. Please advice that we we then machine and remove all the existing babbit, would you suggest a coating with gas flame or ARC on the duly blasted shell surface. Also, we intent to apply a NiAl bond coat....your comments on the same please

Regards

Shantanu
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06-02-2012, 06:19 AM,
#4
RE: BABBIT coating
Dear Shantanu,
Spraying Babbit is extremely difficult as it gives away extremely toxic and hazardous fumes. Its always better to avoid spraying babbit, if you can do by other methods.
Vijay Deshpande
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11-08-2014, 11:42 AM,
#5
RE: BABBIT coating
Hello everybody,
I read your answer on babbit topic and I saw you have a lot of practical experience in babbit applications. I'm trying now to apply on a big bush from a cement factory (crusher) but I have big problems with adherence. I understand from your advices that before spraying babbit to increase the adhesion is better to preheat the bush (200C). OK total agree but I must spray on both sides of the bush and this means that the depot on both surfaces must be made in the same time after preheating. Correct?
Circumstances:If I have to repair only the inside surface how will I proceed? Because if I will preheat at 230C this will affect the outside layer. Or not? Can advice someone?
If I make a thread this will increase the adhesion? Take in consideration that the bush have the outside axis eccentrically and inclined beside internal axis. The outside diameter is 900mm and inside diameter 700mm.
Regarding the water based flux and tin powder mixture can you be more specifically, how are these two components used? If you need more details please contact anytime. Thank you.
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11-08-2014, 05:47 PM,
#6
RE: BABBIT coating
(11-08-2014, 11:42 AM)cristi.genes Wrote: Hello everybody,
I read your answer on babbit topic and I saw you have a lot of practical experience in babbit applications. I'm trying now to apply on a big bush from a cement factory (crusher) but I have big problems with adherence. I understand from your advices that before spraying babbit to increase the adhesion is better to preheat the bush (200C). OK total agree but I must spray on both sides of the bush and this means that the depot on both surfaces must be made in the same time after preheating. Correct?
Circumstances:If I have to repair only the inside surface how will I proceed? Because if I will preheat at 230C this will affect the outside layer. Or not? Can advice someone?
If I make a thread this will increase the adhesion? Take in consideration that the bush have the outside axis eccentrically and inclined beside internal axis. The outside diameter is 900mm and inside diameter 700mm.
Regarding the water based flux and tin powder mixture can you be more specifically, how are these two components used? If you need more details please contact anytime. Thank you.
Hi Cristi,

Sounds like a fun job!

Tinning the surface is a good idea, but not absolutely necessary. To increase the adhesion, you could do the following;

1. Use a very coarse sprayed bond coat of either Molybdenum or nickel-aluminum powder cored wire. These are "self bonding", meaning they will sort of micro-weld to the surface, and their rough surface gives a good anchor for the Babbitt.

2. Make sure the surface is abrasive blasted with clean grit; garnet or AlO2 is preferred.

3. Arc or flame spray wire? Or are you using flame spray powder? Flame spray wire will be best, but make sure he flame is fuel rich (reducing) so that the oxides are minimized.

4. When applying the first coating pass, try to angle the gun in such a way that the spray dust goes over the area just coated and not the uncoated surface. This way, spray dust will not interfere with the bond of the first pass.

If you decide to tin, your surface needs to be smooth but sanded clean (mechanically clean), then solvent cleaned (chemically), and then you can preheat only the surface to be tinned.

Remember, the tinning is done at a pretty low temperature, so you can just heat the surface with a large rosebud torch and just tin the area around the torch and not the entire shell. It takes a while for heat to get complexly through the shell.

If you are worried about the other side melting, just wrap a wet towel around it to keep it cool.

You can use a flux similar to this one;

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Or better yet, this E-127 tinning paste specifically used for tinning bearing shells;

(link dead)
(link dead)


The flux is washed away with water after you are done tinning. Make sure you wash the entire shell.

Just prior to spraying, start heating the surface again (you will see the tin go from dull to shiny) and apply your first coating pass. It will slightly melt into the wet, tin surface. You can use the rosebud torch just ahead of the spray gun to maintain a wet surface. Again, if you are worried, keep a wet towel wrapped around the other side of the shell to keep it cool.

After the first pass, there is no need to keep the shell hot.

Hopefully this helps you. Send some photos when you have a chance.

Regards,

Jim Weber



James K. Weber Consulting LLC
114 North Clinton Ave.
Bay Shore, NY 11706
(631)767-8099

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