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Old 03-18-2020, 02:24 PM
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Default Another Set Of Gas Spuds

We have a large job coming up, where the facility, has since day one have burnt oil, they now want to have the ability to burn either oil or natural gas. The area does not have natural gas, too mountainous, too few people and a poor utility infrastructure. They have decided to set the facility up as a burner of compressed natural gas, trucked to the facility in specially designed tank trailers. The compressed natural gas station, will have 10 tanker bays, with tank trailers in transit on a daily basis.

The original burner was sold as an oil burner with the possibility of future gas hook up. The original seller, sold the burner with the gas ring, but none of the other parts of the necessary for gas operation, so I’ve had to fabricate multiple pieces to get the burner set up for gas operation.

The needed (40) 3/8” stainless steel pipe x 4-1/4” gas spuds with (10) 3/16” gas holes, in a diamond pattern, with a sealed top.

I started with (40) 3/8” x 5” stainless steel nipples, then cut to the correct length, the holes drilled, the end of the nipple tapped for a 1/4” npt stainless steel pipe plug, the cut off flush, then faced in the lathe. The next set is for a smaller burner, so the spud sizing and orifice size and pattern will differ.
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Last edited by platypus20; 03-18-2020 at 02:31 PM.
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Old 03-18-2020, 03:43 PM
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Wow that's a lot of work! how did you layout the holes, do you have a indexing head?
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Old 03-18-2020, 03:54 PM
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Knowing the GNAP it is right between his ears.
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Old 03-18-2020, 05:17 PM
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Wow that's a lot of work! how did you layout the holes, do you have a indexing head?
I drew a line on the spud, had 4 marks on the centering jig, that place the center holes on the line. Then rotated the spud about 45 degrees, then centered the next set of holes between the holes on the line, then rotated the spud so it was 45 degrees the other size the line, then drilled the last set of holes.
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Old 03-18-2020, 07:44 PM
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Just out of curiosity, how specific are these to each boiler? I assume the hole sizing, spud length etc. are all specific to a particular size burner? I have made burners for propane forges and spent some time tuning them to get to where I was happy, so it wouldn't surprise me if these were very burner specific. Is that something that someone mass produces somewhere if necessary, or does it come down to custom making them for each boiler?
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Old 03-19-2020, 07:40 AM
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Just out of curiosity, how spe,cific are these to each boiler? I assume the hole sizing, spud length etc. are all specific to a particular size burner? I have made burners for propane forges and spent some time tuning them to get to where I was happy, so it wouldn't surprise me if these were very burner specific. Is that something that someone mass produces somewhere if necessary, or does it come down to custom making them for each boiler?
Yeah, they are pretty specific to a particular burner, I made about 50 different styles of spuds over the years. The burner throat diameter, along with diffuser configuration effect the length. Inlet gas pressure, fuel type (natural gas, propane, hydrogen or methane), cubic footage required, flame stability and combustion readings (CO and Nox readings) effect spud diameter, orifice size and hole configuration. Sometimes its install the spuds and set up and run the boiler, I’ve had jobs, where multiple spud changes where necessary to get the burner to run at its best. I’ve had jobs, where there was 3 different spud lengths and mixed hole configurations.

Also site variances also effect the burner operation, elevation, stack configuration and draft conditions. Then there is gas supply issues, is it steady are the gas pressure regulators function properly, were they properly sized.

It’s all about the fuel/air mixture, we are looking for the smoothest operation, with the best combustion numbers and repeatability. About 99% of our burner have modulation, where the firing rate changes, on a constant basis. Its can be very easy to get a burner to run at a single firing rate, the real issue for us is the modulation part, getting a stable, smooth, clean flame or a wide firing range can be a challenge, remember at times were firing up to 40 to 75 million BTUs at times.
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Last edited by platypus20; 03-19-2020 at 10:22 AM.
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Old 03-19-2020, 07:52 AM
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Quote:
Originally Posted by platypus20 View Post
Yeah, they are pretty specific to a particular burner, I made about 50 different styles of spuds over the years. The burner throat diameter, along with diffuser configuration effect the length. Inlet gas pressure, fuel type (natural gas, propane, hydrogen or methane), cubic footage required, flame stability and combustion readings (CO and Nox readings) effect spud diameter, orifice size and hole configuration. Sometimes its install the spuds and set up and run the boiler, I’ve had jobs, where multiple spud changes where necessary to get the burner to run at its best. I’ve had jobs, where there was 3 different spud lengths and mixed hole configurations.

It’s all about the fuel/air mixture, we are looking for the smoothest operation, with the best combustion numbers and repeatability. About 99% of our burner have modulation, where the firing rate changes, on a constant basis. Its ca n be very easy to get a burner to run at a single firing rate, the real issue for us is the modulation part, getting a stable, smooth, clean flame or a wide firing range can be a challenge, remember at times were firing up to 40 to 75 million BTUs at times.
Looking thru the glass winder at the ones at work, I see a large round flame, with a heavy amount of swirling going on. Looks long like a hot air balloon flame.

Supposed to be "ultra low Nox" burners, and the factory sends a "tuner" every fall.
(I suggested they get the GNAP in, but they ship a guy in from Oklahoma....)
And he don't fit in ANY flat rate box the USPS offers.....

As you mentioned, firing rates go down to IIRC 25% of full, and are still
required to "make emissions" to meet Pa rules.

Or so they tell me (all of this)..I have no idea myself.

WVa has much less rules...was talking with an engineer friend of mine that
works over there some times (just west of Pizzaborg a few miles)

Last edited by digger doug; 03-19-2020 at 08:01 AM.
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Old 03-19-2020, 08:05 AM
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Quote:
Originally Posted by digger doug View Post
Looking thru the glass winder at the ones at work, I see a large round flame, with a heavy amount of swirling going on. Looks long like a hot air balloon flame.

Supposed to be "ultra low Nox" burners, and the factory sends a "tuner" every fall.
(I suggested they get the GNAP in, but they ship a guy in from Oklahoma....)
And he don't fit in ANY flat rate box the USPS offers.....

As you mentioned, firing rates go down to IIRC 25% of full, and are still
required to "make emissions" to meet Pa rules.

WVa has much less rules...was talking with an engineer friend of mine that
works over their some times (just west of Pizzaborg a few miles)
I’ve seen the turndown ratio, the difference between low fire and high fire fuel consumption rates, as high as 20:1

There are federal stack emission standards and then there are local emission requirements, usually based on the density of boilers in a given metropolitan area and average local air quality readings, then there are state requirements (California and a few others) that are more stringent than the federal requirements.

The swirl is important, you want enough swirl to get a well blended mixture, a consistent fuel/air mix across the flame front. But not too much swirl, then the flame becomes “busy”, taking on a blow torch look, which can effect the heat release rate and usually has a loud harmonic sound level.
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Old 03-19-2020, 08:55 AM
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Quote:
Originally Posted by platypus20 View Post
.

The swirl is important, you want enough swirl to get a well blended mixture, a consistent fuel/air mix across the flame front. But not too much swirl, then the flame becomes “busy”, taking on a blow torch look, which can effect the heat release rate and usually has a loud harmonic sound level.
Now that you mentioned it, the swirl might be up to 90 degrees, kinda hard to look at (I have NO idea what I should be looking for).

Also, It sounds like a oxy/propane torch with too much Ox, a short bushy flame.

As I am looking right in the other end (opposite the burner, about 20' away)
I don't see any "feather" or much of a secondary flame.
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Old 03-19-2020, 12:06 PM
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"Spuds"....and now you got me hungry.....
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