Hi Steve, Your equation and Kester's formula are exactly the same, just different arrangements.  Use your equation you should also get 37.16  lb, not 39.86. The AIM calculations assume that you have to first remove some solder to make room for the addition (in this case, approximately 15.8 lb),  Since the pot volume stays the same, 13.75 lb tin is all you need, and 2.05 ib bar solder to top off the pot. Yu-Shan Han  
 > Date: Thu, 14 Mar 2013 18:56:54 -0400
> From: [log in to unmask]
> Subject: [TN] Low Tin Levels in wave solder pot...
> To: [log in to unmask]
> 
> Hi All,
> 
> I know this is an old question, and I forgot exactly how to determine how much tin you should add to a wave solder pot when the tin gets low. The existing wave solder machine at my new employer that they have now has a 500-lb pot, and the last analysis that was done had the solder at:  60.25% Sn / 39.61% Pb, everything else was within limits. Obviously the tin content needs to be corrected.
> 
> I talked to my old buddy Ed Popielarski about this and he referenced me to a link from Kester that has the calculation at this link at the bottom of the page. According to this formula, I need to add around 37.16 lbs of tin to the pot:
> 
> http://www.galco.com/techdoc/kstr/14-6337-0027_td.pdf
> 
> Then AIM solder has this calculation at the bottom of the page at this link. This one says I’ll need to add around 14 lbs. of tin:
> 
> http://www.advprecision.com/pdf/Solder_Pot_Maintenance.pdf
> 
> And Indium offered this formula to my boss (it’s a cut and paste from a email that he forwarded to me), which I’m having a hard time following (but I can be dense sometimes), I don’t see how they came up with the 39.86 lb figure:
> 
> I did a quick calculation. If you have a 500 lb. pot and the tin level is at 60.25%, you want to add 39.86 lbs. of tin to bring it back to 63%. 
> 
> Here is the equation I always use: let assume you need to add X: 
> 
> (500*0.6025 + X)÷(500+X) = 0.63
> 
> X=39.86
> 
> So I wonder why the discrepancies between the solder mfg formulas? The tin content that they say I should add ranges from around 14 – 40 lbs. Can anybody help refresh this old geezers mind?
> 
> Steve
> 
> 
> 
> 
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