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 Post subject: Questions about CN&W 1385's recent airpump test
PostPosted: Wed Nov 18, 2020 8:18 pm 

Joined: Wed Jun 13, 2012 10:38 pm
Posts: 312
Location: Copenhagen, Denmark
https://www.midcontinent.org/category/cnw-1385/

Is there anyone that can provide me with a copy of the rules that are mentioned in Mid Continent's latest update?

I am most specifically interested in reading about the orifice diameter relative to the desired pressure, and the other specifications a serviceable pump is supposed to live up to when in renovated condition.

An official document is definitely most desirable!

Thanks

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Stuart Harrod
Steam shop machinist
Nordsjællands Veterantog
Veterantoget.dk


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 Post subject: Re: Questions about CN&W 1385's recent airpump test
PostPosted: Wed Nov 18, 2020 9:17 pm 

Joined: Wed Oct 31, 2007 10:40 am
Posts: 95
Location: Chama, NM
It can be found in the Code of Federal Regulations, 49 CFR Part 230.71 Orifice testing of compressors. You will have to scroll down the page a little.


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 Post subject: Re: Questions about CN&W 1385's recent airpump test
PostPosted: Thu Nov 19, 2020 2:16 pm 

Joined: Wed Jun 13, 2012 10:38 pm
Posts: 312
Location: Copenhagen, Denmark
Thank you for the link Russ! Definitely found what I was looking for.

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Stuart Harrod
Steam shop machinist
Nordsjællands Veterantog
Veterantoget.dk


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 Post subject: Re: Questions about CN&W 1385's recent airpump test
PostPosted: Thu Nov 19, 2020 8:52 pm 

Joined: Thu Aug 05, 2010 2:06 am
Posts: 235
Hi Stuart,
A few more details about the process & some of the thinking. The test is designed to measure the volume of air a compressor can deliver in a set amount of time. The number of strokes in the listing is the condemning limit so if the compressor makes one more than that it must be repaired. In the adedenda of Part 230 is drawing 16 which gives a bit more detail on how to make an orifice.

Detail on the accepted process can be had from the Westinghouse pamphlets for at least the 9 1/2 and cross compound compressors and the International Correspondence Schools A-1 Air Brake pamphlet. All three are almost word for word and I'm attaching the ICS version.

As a side note we did not consider this in any way to be The Official orifice test but a test of the pumps using the orifice as a load. We were putting steam to them for the first time as they came out of the shop and were happy as could be that they even ran. According to the mathematics one pump delivered 12% above the limit and the other 42% above the limit and were overjoyed about that........mld


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Orifice Test.pdf [704.28 KiB]
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 Post subject: Re: Questions about CN&W 1385's recent air pump test
PostPosted: Sat Nov 21, 2020 12:53 am 

Joined: Wed Aug 25, 2004 11:16 am
Posts: 709
Food for thought,

There are a couple of things missing from the video. You want to do this test at full operating pressure. I have seen a steam starved pump fail but when the boiler pressure was increased 20 psi it passed. In the old code the orifice edges of hole are to be sharp. and per the Locomotive and Boiler Inspectors Handbook by A. J. O'Neil that the test is in order to maintain approximate 80 per cent efficiency for such pumps.

Robby Peartree


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 Post subject: Re: Questions about CN&W 1385's recent airpump test
PostPosted: Sat Nov 21, 2020 8:04 pm 

Joined: Thu Aug 05, 2010 2:06 am
Posts: 235
Hi Robby,
And a bit of fertilizer to help grow that food for thought:
The 1385 was last running at 150psig which is the same pressure the traction engine was rated for. A little more on that - the procedures call for throttling the steam pressure going to the pump to maintain pressure and if you're that close to needing full rated boiler pressure the pump is probably already pretty tired.

The new code (230.71(b) drawing 16) still calls for the edges of the hole to be sharp and also specifies the land around the orifice to be 1/16" thick. As a side note, the pipe cap used had been milled inside and out to 1/16" so we could get a nice sharp edge on the hole.

230.71(b) 2 also reflects the Inspector's Handbook (paraphrasing here) in that any pump not listed in the table must be capable of maintaining no less than 80% of the manufacturer's rated capacity.

mld


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