Contaminants in Natural Gas (or: Another way to earn 300$/hr)

Over the years, I have had to call in a technician to service my natural gas furnace every year or two. It’s often annoying because they aren’t all very careful or equipped to fully service my furnace. They charge at least 200 dollars since I live outside the city and there’s always a fee for mileage. On the other hand, I’ve been there to watch them do it so many times that I know all the steps by now. For context, I live in Canada, near Calgary, so I rely on central heating between October to May, and I shut off the gas and electricity to it during the summer.

Last fall I resolved to service it myself, and it was even easier than I thought. However, I was surprised by the contamination I found. I decided this would have to be an annual thing. I just finished this year’s service today. I found less contamination, but certainly enough to affect its function. So at least I saved myself another service call.

This is an “old style” nat.gas furnace, with a pilot light, thermocouple, and a safety valve controlling the burner. When I opened it last fall, the pilot was almost completely clogged. No wonder it was hard to keep the pilot light lit. I’ll post a photo below.

My question is what’s causing this contamination?

There’s a powdery residue, reddish in colour everywhere the gas flows on the pilot, none on the burner. In the photo, the thermocouple is the cylinder at the top. Under it is the pilot burner, clogged with ash.

Before clean-up:

After clean-up:

Idk for sure, I’m not experienced in this, but NG usually has 3-5 ppm of sulfur. With the water vapor that is created in abundance, it seems sulfuric acid may be present. Then at high temperatures, I think of corrosion and rust, which can be many colors, including reddish. But, I’m speculating. Watching for an experienced reply.

Latexman response is good.

The natural gas in the distribution should be clean, “pipeline quality gas”. Just west & south of Calgary, there are gas wells w/ sulfur. Several years ago, there was a large side of a mountain completely covered in sulfur. Not sure if the sulfur mountain is still there.

Gas processing should remove all contaminants and deliver dry natural gas. Unfortunately, there are process upsets that contaminants and liquids get delivered to the pipeline and transported.

Sometimes, the heavier hydrocarbons condense during the transport process and mix w/ the dirt, scale, water carryover from gas processing facility, oil from rotating machinery, etc. and end up in the distribution system. At the pressure reducing locations for main distribution systems, a temperature drop occurs which may enhance the liquid carryover. My guess is that the gas temperature is around 40-45 degF there in Canada.

The photos “appear” similar photos i’ve seen for the combustion components for gas turbines. Liquid carryover is culprit #1. The liquids foul the combustion components and end up causing hot spots, wide spread of flame temperatures, in gas turbines.

Filters are then installed to help coalesce & remove these heavier hydrocarbons, liquids, etc. and prevent fouling of combustion components in gas turbines.

A suggestion would be to install a filter. I’ve long forgotten filtration specs and if i find them, i will post.

Meanwhile, here is a image of a typical pipeline quality gas specification in USA. Canada may have something similar, but i do not know where is it located in the CGA website.

If there are low points in your home gas piping, maybe you can inspect for liquids there. Of course, use precautionary measures when inspecting.

The best course of action is to tell your gas distribution company to install filters/coalescer downstream of pressure reducing station to remove any contaminants & liquids. If the fouling source is not resolved, there is potential for heating failures in the home.

For them to bill you for their problem is definitely not palatable.

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Thank you very much!
I will take sime time to digest this. I might also contact my gas utility and try to talk to an engineer about this. They should be able to sample and test for contaminants.
Do you get a sense that these contaminants (if they are there) would be more common or more likely to cause fouling in winter?

Yes, the big sulfur pile north of Calgary was there in the 90’s but gone by the 00’s. Now the site is a shopping mall!

Not sure it applies, but years ago, when I lived in town, the gas company had problems with salt in the gas.
Maybe the salt came from the gas storage facilities. But to think of it, there were gas leaks near the storage facilities. Burned up several buildings in the town near the storage facility.

the sulphur pile i recall was in the pincher creek area - 1997(ish). i recall a lot of gas wells in that area w/ sulphur.

Scrap the debris off your pilot/burner and give the gas company to analyze or tell them to collect and sample. This is a matter for them to investigate and if a potential hazard, they need to deal with it. If there is a substance other than natural gas being transmitted down the pipeline, they are the responsible party. Yes, the gas supply into gas transmission system is constantly monitored. process upsets have resulted in non-pipeline quality gas entering the transmission system for brief periods. the “hope” is that this gas blends w/ other gas resulting in no anomalies downstream. the distribution gas should be routinely tested via the gas chromatograph; however, those molecules may not be capable be being tested via gas chromatograph.

tell them to search and look for low point in distribution piping. they can easily collect samples by removing a section of pipe or otherwise at these low points. this can easily be done in a few hours work.

another possibility is the gas producers inject liquids into the well to enhance production. gas processing methods may not remove. once upon a time . . . upon starting the turbine driven compressors after being idle all summer, the inlet scrubber started filling with liquids. when collecting a sample of the liquid, the liquid expanded similar to spraying insulating foam, then settled into an oil base liquid in about a minute. never saw anything like this before and truly baffling. gave us hell for a long time. fouled up gas turbine fuel control valves, fouled up turbine hot section, fouled up versa valves (used on valve actuators w/ natural gas the power source for valve actuators) - you can imagine the issues there when ESD occurred, and the list is long. It just fouled up everything. versa valves were rebuilt yearly; just a fouled up situation. another contamination source was turbine oil. in 1-year, a production location consumed +50, 50-gallon barrels of turbine oil. quite the anomaly! that oil went down the pipeline. so that oil carried all debris, etc. that was in pipeline. yep, it is not a perfect world, it takes good techs, smart leaders, etc. to get these matters resolved. of course, a wise consumer can be of help too!
btw, the operator that caused this harm is now gone from the area and most people are glad!

wish you good luck!

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I had have a 100,000 btu furnace at work that needed a new thermocouple three years in a row. It turns out it was getting way overheated by the pilot flame. The thermocouple must be adjusted so that only the tip, where the junction is, is touching the flame and getting only hot enough to keep the gas valve latched open. It has now been been about five years since the last thermocouple change. Think about it; thermocouples have their temperature limit, which is far lower than the flame temperature.

I agree though that the carbon build-up in the picture must be due to some liquid hydrocarbons in the gas. Dust, spider webs, and insects in the air mixer of the pilot light are another common problem, which is prevented by annual cleaning.

Most gas valves also have an adjustment screw for pilot flame size. A flame twice the size of another will collect contamination at twice the rate. The default adjustment is fully open.

Carbon residue will cause corrosion when the pilot is off in high humidity.

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I will go look for that screw!

Now that you point it out, the thermocouple is probably well immersed in the pilot flame, rather than touching the tip, as you say. I can adjust that.

Hmm, problem with adjusting that is it will probably lead to the pilot going out as I try various positions before getting it in the right spot. I don’t mind relighting the pilot, but “another” resident of my household certainly does mind… I guess I’d better proceed carefully.

Look what I found here, from the chamber of commerce:

Enhancing Alberta’s Natural Gas System | Alberta Chambers of Commerce

Key take away:

> Currently, there are no quality specifications for natural gas at the delivery point for consumers in Alberta and this can adversely impact downstream users.

Spar; I was visiting a friend who was a technician at the Kananaskis Hydro Generating Station.
Friend was changing a light bulb in the kitchen.
Friends wife was repeatedly reminding him to make sure the power was off.
After abut the tenth or twelfth reminder, friend wispered to me;
“I don’t think that my wife realizes that I work with 230,000 Volts all day.”
A prophet is without honour in his own home?

Be extra careful with the pilot light, Spar. grin

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Most interesting and surprising.

if there are no regulatory gas quality requirements, then gas transmission companies are likely applying their own and hopefully with sound fundamental principals.

for federally regulated gas quality requirements, call a TransCanada office and talk with an engineer in the design/operations group or see the below link.

Other references:

Also, refer to: Codes and Standards | Canadian Gas Association

and particularly: CSA Z662 – 19 Oil and gas pipeline systems

it appears the CSA regs are not publicly available w/out payment.

@WaRoss - thanks for the laugh!

Thank you Bill, your point is well taken, and received with a smile. I do not, in fact, work with 230kV all day, nor with flammable gasses, for that matter. There comes a point where I must stop tinkering and call the pro who does.

Bill sometimes I wish I was as wise as you - because I have to herd a lot of cats at my workplace, and all I seem to do some days is get their dander up. When I tell them to stop or warn them of a coming or past mistake, I can’t always soften the blow.