digital steam engine indicator

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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Re: digital steam engine indicator

Post by Steam Captain » Thu Dec 10, 2020 5:12 pm

So, let's see. I'm still looking for a better way to have the files uploadabl, as gofile removes the files after 10 days of inactivity.

But for now, I try to stick with renewing the link until my head if free enough for looking for a more solid solution. So, if the link doesn't work anymore, it means I lost track of the expiration date and I'll renew the link as soon as I can.
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Re: digital steam engine indicator

Post by Steam Captain » Thu May 13, 2021 10:10 pm

Little update:

Since the cheap pressure transducer I've been using so far leaves much to be desired and makes the indicator useful for very low rpms only, I am now trying to get my hands on a better pressure sensor - hopefully one used as a combined sparkplug-sensor-design for internal combustion engines.

Furthermore, although the display I've been using does work technically, the type of data and the way I want it to be displayed wouldn't be possible on an Arduino. It just doesn't have the computing power for a real GUI application. That's why I've learned the python programming language. I've been programming a computer program to display everything properly. I first want to make it work on PC and hopefully it isn't as hard to create a smartphone app from that point on. I don't understand everything yet, but I'm on it. The good thing is: By using a GUI app, I can reduce all the things to be calculated on the Arduino to a minimum and outsource all the digital-value-to-readable-content processing to device with large processing speed.

I'm not a friend of wireless solutions for sensors, but I guess it'll greatly reduce the wire salad and render the indicator accessible more easily by one or more devices.

So, for me, it boils down to getting my hands on a kHz pressure transducer and working on the GUI program. All the additional features I've mentioned earlier are just not that hard to implement.
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Re: digital steam engine indicator

Post by TahoeSteam » Fri May 14, 2021 8:05 pm

I picked up these transducers. Expensive. Work with an app on phone or tablet via Bluetooth.

https://transducersdirect.com/product-c ... ansducers/
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Re: digital steam engine indicator

Post by cyberbadger » Sat May 15, 2021 1:03 am

TahoeSteam wrote:
Fri May 14, 2021 8:05 pm
I picked up these transducers. Expensive. Work with an app on phone or tablet via Bluetooth.

https://transducersdirect.com/product-c ... ansducers/
How do you pipe one of these sensors up, the datasheet says "40 to 185°F". My boiler gives between 350-384F when she's hot.

Normally I would consider a siphon tube to isolate the temperature a bit, but that could affect the measurement.

-CB
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Re: digital steam engine indicator

Post by marinesteam » Sat May 15, 2021 11:30 pm

cyberbadger wrote:
Sat May 15, 2021 1:03 am
TahoeSteam wrote:
Fri May 14, 2021 8:05 pm
I picked up these transducers. Expensive. Work with an app on phone or tablet via Bluetooth.

https://transducersdirect.com/product-c ... ansducers/
How do you pipe one of these sensors up, the datasheet says "40 to 185°F". My boiler gives between 350-384F when she's hot.

Normally I would consider a siphon tube to isolate the temperature a bit, but that could affect the measurement.

-CB
It's common to use a length of bare tube between the heat source and the transducer. The length is dependent on the temperature of the pressure source. A more expensive option is to use an isolation diaphragm

Cheers.
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Re: digital steam engine indicator

Post by cyberbadger » Thu May 20, 2021 2:43 pm

marinesteam wrote:
Sat May 15, 2021 11:30 pm
It's common to use a length of bare tube between the heat source and the transducer. The length is dependent on the temperature of the pressure source. A more expensive option is to use an isolation diaphragm
The valve manufacturer Noshok has a page where they say that a pigtail steam siphon,
Reduces temperature by 75° F/ft. on average.
- this is also the average for a typical pipe.
Up to 140 °F: The majority of pressure gauges will provide peak performance in this range.
- Unless you get a special gauge this is max temperature you would want to expose a typical pressure gauge to.

They have various products that perform similar or even better.

https://www.noshok.com/support/support- ... lications/

If all of this is correct, the 4" steam siphon on my primary gauge is only reducing the temperature by 25° F. I'm glad my gauge is rated for 400F ambient and process temperature up to 600F degrees...

-CB
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Re: digital steam engine indicator

Post by fredrosse » Fri May 21, 2021 9:09 am

That Noshok data is very conservative, and with our steamboats generally operating in the open air, the cooling of the gauge loop is much more effective than they indicate. Both of my boiler attached pressure gauges (one very small, 2 inch diameter, the other larger, about 4 inch diameter) can be touched by hand with steam pressure up. Anything over 140F will burn me, so the loops provide good protection from the 365F saturated steam temperature.
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Re: digital steam engine indicator

Post by cyberbadger » Fri May 21, 2021 11:36 am

I have had small 2" or less gauges fail under steam, but I believe the failure mode was from pulsation, not perhaps temperature. When the gauges broke, I had a shut off valve so it wasn't a big issue.

I still feel really weird putting plastic close to steam.

-CB
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Re: digital steam engine indicator

Post by TahoeSteam » Fri May 21, 2021 7:30 pm

I placed these transducers directly into 1/4" ntp brass tee that only had a 2" long 1/4" NTP brass nipple attached. Both on HP (150PSI) and LP. Ran for quite a while like that. No issues
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Re: digital steam engine indicator

Post by Steam Captain » Mon Jun 14, 2021 2:24 pm

Correct, a syphon won't work. The elasticity brought into the equation by adding a syphon would completely ruin any recognizability of a pV-graph.
I've tried to get my hands on a pressure transducer, but the answer I got was always "We only sell to commercial buyers" - Those pressure sensors would have been perfect. They worked up to 400°C and covered all pressure ranges below the Gpa scale. And they were small (M5 thread). BUT they didn't want to sell.

I secretly settled for spark plug pressure sensors right now unless there'll be a source of a good pressure sensor to switch them out. The challenge is, that almost all pressure sensors on the buyable market are not suitable because they simply measure too slowly and not just a little, but several orders of magnitude too slowly.
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