AMS 2769 Dew Point

[AidanMc]

I have a question regarding dew point measurements per AMS 2769. I was wondering if anyone has dealt with this before and can help me out before I have to contact Nadcap. I assume that some of the people on here have experience with aerospace specifications such as these.

The spec reads "In lieu of sampling dew point at each furnace, the gas may be sampled at the end of each leg of supply piping, at the furthers point from the supply" (Paragraph 3.2.1.1). Currently, we sample dew points quarterly at each of our furnaces with an old instrument but I am hoping to move to putting a single permanent instrument in to provide alarms and simpler auditing. The question I have is with the term 'leg'. We have one main supply line from our nitrogen supply to our furnaces, each furnace has approximately 15'-20' of pipe off that main line before it gets to the furnace.

Would this mean we have a single leg of supply piping or would each furnace count as it's own leg? Related but not important to me now, how long would the line to the furnace have to be before it counted as it's own leg, in your opinion?

Thank you for any help you can give me.
-Aidan

Aidan McAllister
Metallurgical Engineer
Automotive Enthusiast

 

[EdStainless]

It won't help you much, but we chose to put an instrument on each furnace. They are set up to be able to measure both incoming gas and furnace atmosphere.
We did this because our furnaces are far apart.
In your case I don't see 20' as being a leg, this is just a service drop.
You would need to sample at the farthest point in you entire distribution system.
Though it might be good to contact your registrar and ask their opinion.

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