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 Post subject: Testing Exotic Stainless Steel
PostPosted: Feb Sun 11, 2018 5:09 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 10380
Location: Baguio City, Philippines
I started writing this last year when I was taking care of my father, who, at age 96, was still working every day. His business, which he specialized in for more than 50 years, is highly technical and extremely esoteric. Right up the alley for some of the members here.

He was one of the world’s foremost experts (if not the foremost expert) on P91 Stainless Steel. HIs business, Materials Technology Corporation, tested a lot of different materials, from ceramics, to plastic formulations for Ford vehicles, to glass beer bottles. The majority of their work involved P91 Stainless Steel. It’s a specific formula that is used in instances that put the metal under high temperatures and stress. The two most common places you find it is in oil refineries and power generating plants.

An example of the problem:

Power generating plants boil water to create steam to turn turbines. The steam created is moved through long pipes under pressure. The pipes are usually about two feet in diameter and two to three inches thick of high quality chromium-molybdenum stainless steel (P91). The steam travels through the pipes under high pressure and at temperatures that can reach around 1500ºF. It costs millions to manufacture and install each pipe line and it can take upwards of a year to complete the job.

Unfortunately, the pipes wear out over time. The first sign is they develop microscopic pin holes in them. Through them steam can escape and because the quantity is so small, the leaks are invisible. The frequency of the leak is ultrasonic, so it can’t be heard either. If undetected, a worker walking past such a leak could be killed instantly by the escaping steam.

After pinholes start appearing, the pipe may be just weeks away from a catastrophic failure. Weakened pipes have been known to explode and have sent shrapnel up to a quarter mile. An explosion like this not only destroys the pipe, it damages everything nearby and can injure or kill workers in the vicinity. The plant would then be off line for a year or more while repairs are done.

So the pipes need to be replaced before they fail, but they need to be kept in service as long as possible for economic reasons. That’s where my father comes in. He tests the metal and can tell you how much service life is left in the pipe.

Here’s how it’s done:

The pipeline in question is shut down temporarily. A couple foot section is cut out of the pipe and a new piece is welded in place so that service can resume. The sample section is shipped to Ann Arbor, Michigan.

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Once there the pipe section is cut into wedges and each wedge is cut into slices. It takes about $1000 in machining to turn the rough pipe into a testable specimen. The machined piece has threads on the top and bottom and a middle section that will be heated and put under stress. Because the pipe is curved it is necessary to add metal for the threads. This is done by electron beam welding additional pipe along the outside.

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After a few days in a CNC milling machine, the final piece, measured with micrometers to extremely precise measurements, gets plated and is ready to start the testing process.

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The next step is make up, where the specimen is threaded onto grips after liberally covering the threads with Milk of Magnesia to prevent them seizing (something my father came up with). It’s then hung in a frame and platinum thermocouples are placed at the top, middle, and bottom of the area to be tested and custom wires are added (two 25# rolls of wire cost $6000). At the bottom of the specimen are attached a couple of small mirrors.

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This assembly is then placed inside a furnace that has three zones of heat (top, middle, bottom).

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A mechanical load is added to place stress on the specimen. Some are dead weight machines, others have 10:1 ratio levers. A precise amount of weight is added.

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The furnace is then brought to temperature and carefully monitored over the life of the test (usually from a few months to a few years).

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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Sun 11, 2018 5:12 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 10380
Location: Baguio City, Philippines
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Telescopes are trained on the mirrors that are positioned to allow viewing of marks on the specimen and reflect back on a scale along the scope (another thing my father devised).

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At regular intervals (between one and several hours) a technician looks through the scope and records where the mark is.

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Over time this shows the stretching (creep) of the metal. The measurement accuracy is six-millionths of an inch. The test continues with the readings showing the progression of the creep. The test ends either when the testing time frame has elapsed or when the specimen fails and breaks (rupture).

One note: Hope not to be anywhere near a test when it ruptures. The sound of several hundred pounds of weights crashing to the floor is extremely loud and always unexpected. Even when you know a specimen is about to fail, the exact moment is always a surprise.

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The points are then plotted in a graph and my father would look at the graph and could tell the length of time left before the pipe in service would fail.

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At the time of his death last year he was working on a problem that he identified with every power plant in the world, and one that potentially could affect the US power grid. It involved identifying weaknesses in portions of electron beam welded pipes before they became problems. He had set out a complicated series of tests to see if his theory was valid. It would have taken a few years to complete and he was in the process of procuring funding to progress with the portions he couldn’t afford on his own. I know he had all the intricate nuances worked out in his head, as we talked about it several times, but I don’t know if he had related the problem to anyone that could actually understand it that would also want to investigate and find a solution.

The company still exists, but there is a vacuum in the technical director position. He would have turned 97 in a few days.


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Sun 11, 2018 8:43 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 7228
Location: Portland Oregon
With a background in aircraft and aerospace machining I can relate to a lot of what I saw being done in those pictures. What an incredible setup he had going there.
Ed


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Sun 11, 2018 2:16 pm 
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Joined: Mar Sun 30, 2008 1:45 am
Posts: 194
Location: Oakland Township, Michigan
I worked for Westinghouse PGSD as a consultant in the early 80's. Thank you for sharing Alan. Very interesting.

-Matt

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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Sun 11, 2018 2:47 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1434
Location: Jackson, TN
Alan,

Quite interesting, I'm guessing your dad was a mettalurgist?

I worked for years in the metals industry, mostly aluminum. I was always impressed with the complexity of the metal sciences. On the surface it might appear simple and straight forward, but the underlying science is very complicated.

Metallurgists tend to be geeks of the highest order :P
Most of them are good at gracefully 'dumbing' things down for laymen who really do not really grasp all the science.

Thanks for posting.
Tim


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Sun 11, 2018 11:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8221
Location: Litchfield Minnesota USA
All I can say is, WOW! What an operation!

Mark D.


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Mon 12, 2018 12:18 am 
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Joined: Aug Thu 20, 2015 3:09 pm
Posts: 1020
Location: Albion, CA, USA, 95410
Really neat. Enjoyed reading it, it does great honor to your Dad.


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Mon 12, 2018 12:57 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2013
Location: seabeck,wa. usa
Thanks Alan. Enjoyed it. Very interesting.


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Mon 12, 2018 1:18 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12825
Location: Omak,wa,usa
Hello Alan
yes thank you for posting about this and I know a guy who ran a business in California who tested metals for aircraft
sincerely rich


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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Mon 12, 2018 3:00 am 
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Joined: Jun Fri 05, 2015 4:59 am
Posts: 286
Location: Southeastern Litchfield County, CT
Very fascinating, Alan - thank you for posting those pictures and explaining them. It never ceases to amaze me just how much goes on 'behind the scenes' to enable the things (like electrical power) that so many in our society take completely for granted without even an inkling of the incredible technology, development and knowledge behind them.

It sounds like your dad was a most impressive guy - even more so that he was still active and doing this in his mid nineties! I hope he had related as much as possible to others at his company - it's a shame to lose a brilliant mind like that.

-Pat

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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Mon 12, 2018 3:45 am 
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Joined: Mar Sun 11, 2007 6:55 am
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Location: Mission Viejo, southern California
Thanks for such an interesting article. What became of the business?

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 Post subject: Re: Testing Exotic Stainless Steel
PostPosted: Feb Mon 12, 2018 12:16 pm 
Site Admin

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10380
Location: Baguio City, Philippines
The company is still in operation. The staff there is top notch at all the operation required to prepare the specimens and run the tests. The company has an outstanding reputation for quality and reliability in it's work. The final technical decision are done by the clients alone, rather than in consultation with my father. Since there are only a few such operations in existence, it is unlikely that the business will stop any time soon. Currently there are test running that won't be completed for a few years, so it can't just stop.

I wish I had taken a photo that showed more of the place overall. There are probably close to two hundred test machines in the building; some considerably larger than the ones in the pictures.

Here's one photo that didn't fit into the narrative, weights that all weight precisely the same amount. The gold one is the standard; the silver ones are all drilled to match:

Attachment:
weights.jpg
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