Author Topic: 313 d question  (Read 2001 times)

Offline preetnep

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313 d question
« on: December 01, 2015, 11:04:52 AM »
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.

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Re: 313 d question
« Reply #1 on: December 01, 2015, 02:25:59 PM »
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.

Offline preetnep

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Re: 313 d question
« Reply #2 on: December 01, 2015, 05:18:39 PM »
But 29.92 in hg = 760002 microns

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Re: 313 d question
« Reply #3 on: December 01, 2015, 08:07:22 PM »
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?

Offline preetnep

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Re: 313 d question
« Reply #4 on: December 02, 2015, 08:51:39 AM »
Yes u are right . Thanks