What corrective action is taken when brazing a copper line to copper,to indicate brazing material is driest system and leak free?
A Clean the joint then apply more heat.
B Clean the joint and reduce heat
C Increase nitrogen bleed then apply heat
D Increase nitrogen bleed then increase heat.
2. Which vacuum reading indicate the driest system
100 microns, 40 microns, 29 in Hg, 0in Hg.
1. C Increase nitrogen bleed then apply heat would be my guess. But using a nitrogen bleed prevents oxidation and scaling and really has nothing to do with leaks. There really is no answer provided that would indicate a dry leak free system.
2. I would say the answer is 40 microns. If the answer had 29.92" Hg as a choice then it would be the driest system at 0 microns, but it said 29" Hg, which is between 20,000 and 25,000 microns.
But 29.92 in hg = 760002 microns
I posted a table below and was refering to the gauge pressure instead of absolute pressure. You're right, 29.92" Hg = 760,000 microns in absolute pressure, but 29.92" Hg = 0 microns in gauge pressure.
If the question is asking about absolute pressure, 0" Hg would be the lowest at 0 microns, but I don't know if that's even possible. Although it does say 100% vacuum in the chart. It might be a trick question, in which case 40 microns would be the most correct answer.
I'm thinking whether it's possible or not, 0" Hg absolute or 0 microns is technically the driest possible system.
Was this a question on the 313D exam?
Yes u are right . Thanks