A Carbon Monoxide Accident Waiting to Happen

Unknown

I am enclosing an article from the Summer/Fall 2005 Issue of GAMA Magazine. GAMA is Gas Appliance Manufacturers Association.

This is definetly a reason to TEST and TEST often as you will not always know what the BTU content of the gas may be. I look forward to your comments. I am sorry it is a little long but I did not want to leave anything out.

NEW GAS SUPPLIES WILL AFFECT APPLIANCE SERVICE

The natural gas supply in the United States is changing. As the volume of liquefied natural gas (LNG) imported into the United States over the next five to 20 years or so, the characteristics of the natural gas supp] y will change even more.

Many heating contractors and technicians may not realize what this will mean to their troubleshooting and maintenance routines. It will mean there is something more to look out for during routine and emergency service. It may also mean increased maintenance opportunities, to adjust customers' heating systems to bum the new gas mixtures cleanly and most efficiently.

According to Frank Stanonik, chief technical advisor for the Gas Appliance Manufacturers Association (GAMA), contractors will need to find out the specific heating value of the gas delivered in their vicinity in order to find out whether or not gas appliances are burning at the right input rate.

What's A Wobbe?

In almost all gas appliances, gas flows into the burner through an orifice, which is part of the means to control the input rate of the appliance, Stanonik explained. The usefulness of the Wobbe number is that for any given orifice, all gas mixtures that have the same Wobbe number will deliver the same amount of energy.

The Wobbe number (or Wobbe index) of a fuel gas is found by dividing the higher heating value of the gas in Btu per standard cubic foot (scf) by the square root of its specific gravity with respect to air.

Pure methane has a Wobbe number of 1,363. The Wobbe numbers of natural gas piped to most homes in the United States range from 1,310 to 1,390, although in anyone area of the country it will not fluctuate widely around an historical average that is between those two extremes, Stanonik pointed out.

High Wobbe VS. Low Wobbe

If the new gas has a higher wobbe number, which usually translates to a higher heating value, this will increase the temperature of the heat exchanger and increase the thermal stressing of that component in furnaces, boilers, room heaters, and commercial heaters. This increased level of heat at the burner and in the combustion chamber will raise the temperature of components in direct contact with the burner flame or installed within the appliance.

If those components are heated beyond their temperature ratings, component failure and appliance operational problems will occur. Even if the elevated component temperature does not exceed its temperature rating, it still may be beyond the designed or normal operational temperature range of the component. In that case, premature failure of the component may result.

Common devices that are in direct contact with the flame include flame sensors or other ignition-proving devices, Stanonik explained.

The obvious things a contractor might see are a larger-than-normal flame, he said, soot inside the combustion chamber, flame impingement on components, or a high limit tripping. These symptoms are not specific to gas quality, of course, but gas quality will need to be considered in the troubleshooting process.

If the new gas has a lower Wobbe number, which usually translates to a lower heating value, the gas appliances will be underfired. The appliance will not deliver as much energy as it's designed to do, generally resulting in decreased performance of gas appliances.

Space heating appliances of all types will have to operate longer to provide the heat required for the space; water heaters will have slower recovery times, and cooking appliances will either cook longer or cook unsatisfactorily. It will not result in higher fuel bills, Stanonik added.

“The consumer probably won't see a change in (the energy} bill" he said. 'There will be a change in the comfort level. They may notice that it takes longer to get the house warm."

A significant change in the Wobbe number in either direction presents potential problems due to increasing carbon monoxide production, according to GAMA. It can be caused by incomplete combustion that results from major changes in the air-fuel mixture occurring at the burner, or it can be caused by flame impingement on surfaces within the combustion chamber that alters the combustion process.

"On appliances with properly designed and operating venting systems, this is not an immediate problem in and of itself," Stanonik said. "But it is indicative of improper operation of the appliance. If such a condition develops, it should not be allowed to continue as normal operation."

Contractors also can check for a difference in flame characteristics. such as size and color. Stanonik said that underfiring or significant overfiring both may cause a more yellow flame.

"A lot of contractors are used to performing that kind of visual inspection," he said, noting that contractors also should look for sooting in the appliance, specifically on the heat exchanger's surface. "Many of the symptoms are things that contractors will know to look for anyhow,"

Relatively Easy to Fix

Can contractor service equipment so that combustion is complete, to match the new fuel's Wobbe?

"Absolutely yes," answered Stanonik. "If the new fuel is within the acceptable range of interchangeability and if he's aware of the situation, he can adjust the appliance to put it back on rate."

First, the contractor needs to find out what the actual heating value of the gas is for the day he is out providing service. This entails calling the service utility and asking what the heating value is for the gas it is providing that day. Then the contractor clocks the appliance and measures its firing rate using the home's gas meter, is it’s firing higher or lower than the normal input rate?

Next, the contractor should adjust the appliance to go back to its proper firing rate with this new fuel.

In times past, Stanonik said, some contractors adjusted the firing rate based on an average heating value of 1,000 Btu per cubic foot..

In old days it would work, but now that rule-of-thumb adjustment may not be good enough: he said, adding, "This may become another reason why people should really start to make it a practice to have their appliances checked once a year. There is more motivation."

In the end, contractors need to educate their customers about the importance of annual system maintenance.

"As new appliances are installed or serviced, it is vitally important that installers and service technicians make sure that those appliances are operating at their nameplate hourly input rating: Stanonik said. "In order to do that, the technician will need to know the heating value of the gas being delivered at that time, using an assumed nominal value will not be good enough."

GAMA's Actions

Recognizing the need to understand and manage this situation, a coalition of gas transmission and distribution companies, gas utilities, GAMA, and other interests was formed: the Natural Gas Council (NGC). One of the products of the National Gas Council was the development of a set of interim guidelines for gas interchangeability.

These interim guidelines were submitted as a recommendation to the Federal Energy Regulatory Commission (FERC) in early March. In essence, the interim guidelines state that for any specific service territory, the quality of the new gas supply (as measured by the Wobbe number) should not vary by more than + or - 4 percent from the gas that has been supplied historically in that service territory. At the same time as these interim guidelines are being implemented, the industry hopes to learn more about the performance of end-use equipment using the anticipated new natural gas supplies. In GAMA’s case, that equipment includes residential and commercial appliances.

For more information, visit www.gamanet.org.

Steamhead (in transit)

Yet another reason

to test everything often.

With this in mind, it seems like a good idea to set the input rate a bit lower than the nameplate rating to avoid problems that would occur if changes in the gas supply cause the input rate to rise. What do you think, Tim?

Firedragon_4

Thanks for the e-mail Tim!

I'm going to post my answer here and I will relate this over to fueloil, being my fuel d'jour :-)

If we get an 'off-spec' fueloil, even with fixed pump pressures and nozzles, that are similar to your regulators and orifice openings, things can go bonkers and they generally lead to 'cold-soaks' and 'running saturations'.

Over the years there have been mess-ups with off-spec fuels and in the late 1980's and early 1990's there were just too many that where shrugged off. It's now my opinion that it was due to off-spec fuels.

Lately, there has been virtually no mention of these mess-ups and IMO it's because the refiners, importers, distributors and wholesalers wised up and realized they were going to get caught.

Today, I think oil is more closely scrutinized and with a $2.50 to $3.00 per gallon price coming up it should be. BTW, shoot the Wall Street speculators!

Good or bad things seek their own level and if this causes the problems you are concerned about I think you are correct in forecasting it will do the same.

I think after the insurance business pays a few claims and starts looking at subregation the gas industry will wise up.

Fuel oil is on a hit list with the insurance companies due to the oil tank leakage problem and a lot of soot claims. I'm hearing loud and clear that now that UST's are virtually gone they are now after AST's, there's a posting elsewhere on The Wall that proves that out.

Soot claims are due to inadequate testing and careless service procedures. Many in our combined industry have decided that quantity is more important than quality, but with the oil industry quality was a former trademark.

I think I see reality catching up for the gas industry and I hope the decision makers in your industry (gas) don't repeat the mistakes that the oil industry has made.

'Those who fail to learn from the past are doomed to repeat it,' goes the aphorism. IME, sometimes the best way to learn from the past is not to repeat it, but to try your best to reinvent it, today that's called 'thinking outside the box', but I've been slandered for saying things like that.

Regretfully, the boys from the 'but we always did it that way' school would rather die as traditionalists than make their mark as individualists, JMO!

But, if this issue brings out anything is that we need to 'test, test, test', but why is it that only educators and those that have been sued sing this song???

Hi-ho, hi-ho, it's off to work I go, with my testing gear and a lot of cheer, hi-ho, hi-ho!

See ya.

Constantin

Interesting Read, Thanks Timmie!

While I understand that the LNG may have a different heating value, etc. than the natural gas extracted in the US, it still doesn't explain why, allegedly, a lot of customers will have to have their gas-line seals replaced due to exposure to gas derived from LNG.

It's also fairly entertaining to hear the gas industry claim that the heating value of gas does not vary that much... All that testing I had to do to get the gas water heater certified on multiple mixtures of fuels was for the sheer fun of it? UL, or whoever wouldn't require it, if the gas companies weren't doing it!

Conversations with manufacturers has also shown that the gas coming out of a pipe is not nearly as consistent as the gas company wants us to believe. The rotting seal issue is simply the latest icing on the cake.

Christian Egli

This gas WOBBE factor is enough to leave me all wobbly

I would love to see appliances with continuous monitoring and display of gas issues.

I understand it is the mission of gas utilities is to supply as at 100,000 BTU / CCF. I have to trust they do so honestly or else I would not be charged correctly for the energy I use, since the gas meter measures CCF with no correction for heating value. Meters do correct for temperature and pressure though.

The first thing that comes to my mind is: shouldn't we have WOBBE compensated gas meters?

I always look suspiciously at my meter. Utilities always rush in to test a meter that is experiencing an unusual decrease in consumption (because of a new boiler or new insulation), but they never do so when there is an increase in usage. Shouldn't I worry at least just as much as the utility? What? The WOBBE worry me?

Now, gas companies have long served us a cocktail of gases. Whatever is available. Methane, propane, even the gas that percolates from our garbage dumps. When they add propane, they also stretch the mixture with compressed air to dilute the energy content. A watered down drink.

If anything, I will never expect to find that the gas I am delivered has a higher energy content than the standard natural gas. Why would a utility do that? Selling compressed air is just too good an opportunity for increased profits.

There's no reason to complain, really, since the energy content is set, probably by law, at the 100,000 BTU / CCF.

So, what's next to influence the WOBBE?

Specific gravity, as the formula states. And this, too, is obvious since dynamic gas flow through an orifice is directly related to specific gravity but also temperature and pressure. So the utility messes with the first parameter, but me in turn, within the particular piping and usage within my building I will mess with the two other parameters.

So, who perpetrates the worse offense? I am not sure. How significant can these variations possibly be? I don't expect orders of magnitude.

I count a lot on the gas valve, which through its magic, corrects lots of my problems. I am guessing and hoping that we will have to find the WOBBE correcting gas valve. Easy... science to the rescue and people like you, Tim, thanks for sharing your knowledge.

A quick glance at a data book gives me a specific gravity for methane at 0.55; propane at 1.5; butane at 2; air, of course, at 1.

This means in a home filled with air, leaking methane will float up the chimney and out, or alternately, up the stairway into the rooms where we sit and can smell it before things go boom. It is rather safe.

With a gas like propane and I guess the heavier WOBBE gases, the opposite happens. When it leaks, it floods the basement and when it arrives at the level of the pilot, it goes boom. This time we had no warning upstairs.

Something to think about, the WOBBE and the BOOM factor. None such with good old coal, energy packed and dug from our own back yard.

I believe Baltimore is THE harbor where we can unload liquefied petroleum gases from incoming ships. Is that place busy right now?

Happy as always to dump my thoughts. Best regards.

Bob Harper

Wobbe-wan-kanobe (Timmie)

With about 33 terminals for LNG planned, Baltimore won't have to worry about being the only Al Quaida target port...

This is going to get interesting. We routinely refer to the properties of gases using specific gravity. This should correctly be used only for solid or liquid phase materials. Therefore, the sp. gr. of liquid phase C3H8 is 0.504 with a vapor density of 1.50 at 60F. As the composition of the gas gets heavier, so these numbers will rise. BTW, the numbers for butane are 0.582/ 2.01 and methane at 0.3/0.60

This freaks out a lot of people because they are taught the sp. gr. of these gases with the numbers that are actually the vapor density yet no one outside of gas suppliers rarely calls it that.

When guys first read this, they freak and query, "you mean to say LP is LIGHTER than air at 0.504?" No, it is lighter than WATER and will rise just like an oil slick. A gallon of propane weights about 4.2 pounds while water weighs about 8.24 lbs/ gallon. At a Vapor Density of 1.50, it is heavier than air and will sink waiting to strike like one of those camougflaged bucket mouthed fish on those nature shows. You walk by and POW! Got ya!

Now, we have to re-train our guys to report the Wobbe index?? I think this may turn into the Woe Be Unto You index....

Ok,its getting late.
C.U. later, Bob

bob_50

WOBBE-GONE

Isn't that a lake somewhere? Seriously, aren't home heating appliances a little behind the times. Large boilers continiously monitor and adjust combustion with systems like Oxy-trim etc.. Your car has an oxygen sensor in the exhaust pipe to do the same. With small cheap micro-processors just build a burner that monitors and regulates firing rate,pri and sec air co2 c0 nox etc. We can call it Wobbe-gone. bob

Steamhead (in transit)

Actually, I think

the LNG terminal is south of Baltimore, somewhere along the Western Shore of the Chesapeake Bay. IIRC they put it there so it wouldn't be near a major city that would be difficult to evacuate in case of disaster.

jerry scharf_3

wrong on the BTU/cuft assumption

Christian,

When we visited HTP, Brian French told about how all the gas utilities hated him. He used to send out empty bags, have the tech with the offending system fill them with gas from the meter and send it back. He would then run them through his gas chromatograph, and found anythng between 700 and 1600 BTU/cuft. The providers probably thought they were giving the customers a bargain with that high end stuff... Now when wholesalers do "custody exchange" of gas, they have continuous BTU/cuft testing (every minute or so) and pay for the BTUs delivered.

It was after this that I realized how hard it must be to be trying to squeeze maximum efficiency and low CO out of boilers that have to run in such field situations.

jerry

jerry scharf_3

asking for my wobbe number

Timmie,

So the next time I'm setting up a gas device, I will call the local utility. I am sure I will get a courteous, professional and prompt response for the currently delivered gas' wobbe number.

Let's all do this so we can compare (laugh about) the results.

jerry

Unknown

It gets interesting

I called three different utilites and sked to speak to there gas supply people. I was lucky enough to get connected to two of them. Neither one of them had ever heard of Wobbe????

I did find one utility person who I know personally who had heard about it but was not up to being able to tell me what the Wobbe number for their gas would be.

My local gas company list the BTU content average number on my bill so I figured mine out. The BTU content here locally is 1027 BTU's per cu bic foot. I then found the square root of .6 (specific gravity) to be .7745966. I divided the square root number into 1027 and my local Wobbe number is 1325. Here locally we have set burners up for years at an assumed BTU number of 1050 so this sure changes things.

Just a side note there is an ongoing attempt to build two additional LNG terminals one in Providence (Keyspan) and one in Fall River, Mass. The feds approved Fall River but rejected Providence. There is a big political battle about this whole LNG thing. Now we have Wobbe, well woe be unto all of us.

I will be taking that article and writing my answers to each phase of the article in an upcoming issue of the HVAC Insider. That is the only trade paper that I can write for as all the others are impossible to get them to print articles from other than there own special writers. I apologize for that but I will keep you posted and for those who do not get HVAC Insider let me know if you want to receive it (FREE) and I will see that you get on their mailing.

Keep the comments coming as I will include them in my article if they are pertinent.

Jim Davis_3

Natural Gas BTU's


this week I had a student/instructor that had just visited the CSA test labs. They have a caloric meter on their gas line. In one hour the BTU's of the gas changed from 935 btu per cu. ft. to 1027 btu's per cubic foot. They told him that this is becoming normal and makes it almost impossible to rate appliances today. The BTu's across the country and from altitude to altitude are infinitely different. That is why using gas pressure and clocking meters is a dangerous way to set up a burner. Combustion analyzers measure reality. They determine flame color and size not the eyeball!!! The only wobbe I need sits on the dash of my car. Wait that is a wobble. Same thing if that is what you plan to depend on.

Christian Egli

To be more specific

I did make this 100,000.00000 BTU/CCF assumption with a little cynicism, but I never imagined the tolerance bracket was that large. Per CCF this would be from 70,000 to 160,000 BTU.

Wow, now I’ll be looking at my gas bill with an evil eye.

I note also, that on my gas bills, the utility computes everything to something like 10 significant digits, to make it look like this is highly accurate stuff. What’s the deal with that?

A question to the oil guys. When charging for a full tank of heating oil can you actually get away with leaving it only 70% full?

Also, I am wiping the words specific gravity from my vocabulary. Indeed, vapor density is much clearer. I do think it is less confusing to speak in terms of units of weight per units of volume (with temperature and pressure qualifications) rather than to use the specific gravity figures which are unit-less numbers relative to the qualities of another substance (while leaving lots of the temperature and pressure issues up in the air).

I believe metric people speak mostly in terms of density and volumic mass, specifying the units all the time.

But, of course, this will apply to the gas utilities only within their comfortable range where anything between -30% to +60% is close enough.

[Deleted User]

Actually,

the Maryland LNG Terminal is @ Cove Point, well south of Baltimore. That is where the product, that WGL says is eating their seals, is coming from.

The expert says customers will not notice any increase in consumption & the appliance will only have to run a little longer to do its job. Guess he never heard of steam boilers.

So now we not only have to be concerned about having enough incoming gas pressure, but the btu content du jour. And that may change from minute to minute. Guess it's time to follow many Germans. Wood lot - here I come. Wonder what the btu content of red oak is?

Firedragon_4

Oil is sold

by the metered gallon like gasoline. There's no such thing as buying a tank full, it's all done as top-off's in gallons.

When a house is sold the tank will be measured in inches of volume. The inches are converted to gallons and we're back to gallons again.

I hope I made that understandable.

Unknown

Jim Davis

with all this fluctuation you will almost have to go out and check your last job in a week from now as all you set up will have changed as the gas changes. To my thinking even with a good combustion setup and test it will be useless in a day or two. This could end up being a nightmare at some point. I am trying to come up with a point of burner setup for local techs here in RI and also Mass. I am sort of looking for a safe point of adjustment. I would appreciate any input you have on this Jim or any others. I feel that a safe procedure relative to this flucuating situation needs to be developed.

I realize that BTU content has fluctuated for years but this is a very drastic change. I have already had several jobs in the past two years with problems caused by high concentration of LNG being vaporized into the gas line and seeming to accumulate in one area. Sooted up boilers and furnaces that had been properly set up by a contractor and myself with excellent combustion analysis figures and very low CO. Three months later we have four units sooted up. I was called in on these units by the contractor as he had a problem before on these. I did not realize unitl just recently that our porblem was LNG with a higher BTU content.

Bob Harper

alternative fuels

The BTU content of a pound of kiln dried wood is about 8660 regardless of species. The species determines the approximatel equilibrium moisture content. You can take a pound of pine, kiln dry it to 5% m.c. and it will absorb water from the air to an equilibium m.c.% of maybe 12-15% while you can get most hardwoods to stay down in the 8-10% range. The softwoods tend to be hygroscopic. Since hardwoods are denser, the same size log holds more BTUs than a similar sized softwood log.

The new energy bill in the Senate would give tax credits up to $3K for a one time purchase of a pellet stove among other fuels.

All this BS we have to put up with from the NG companies has been a way of life dealing with the LP suppliers. We tested samples of LP from the Philly region and found they varied from a sp. gr. of 1.50 to 1.56. There is a pipeline terminal in Eagle, Pa. that originates in Belvediere, Texas that supplies HD-5 propane (less than 5% propylene). However, with approx. 300 refineries to shop from, you never know where they got it or what the analysis is. When you are experiencing problems such as delayed ignition, sooting, poor combustion, or overfiring, you sometimes try to contact the LP gas supplier for a copy of the analysis of the last batch he delivered to Mrs. Smith. I've rarely gotten cooperation from them.

Then you have the utility laying pipelines to new homes only to setup an LP aeration station at the entrance. We did not test our appliances with this hybrid fuel nor is it listed with it. Therefore, we wash our hands of any sequelae until they can supply either US grade 'A' NG or LP gas. The utility can pay for cleaning up any sooting and they can pay us to make the conversion when its available. They could have avoided this mess by setting the place up for LP and budgeting in for conversions when it becomes available in a yr or two.

No end to the mis-adventures. Our dilemma is there has not been litigation of a high enough profile and price tag to call public attention to it. We need an AJ trial to get the industry to clean up their act. I ain't holding my breath. As Bette Davis warned: "Hold on, we're in for a bumpy ride!"

Firedragon_4

For Jim and Tim,

excuse me for being the gas trainee instructor! :-)

What is the gas industry going to do if time accepted practices such as meter clocking and pressure settings aren't going to do it anymore?

Combustion testing is the way, no doubt, but that takes care of right now, this second. If people are seeing the fluctuations that Jim describes even combustion testing is useless when you walk out the door, FACT!

Whatever you guys come up with please keep us all in the loop. The two gas OEM's I'm working for are having me preach pressure testing, clocking and combustion testing, but I don't see any of them being a cure-all when it comes to the Woobe factor.

Having lived through this on oilheating units you guys are in for it, FACT!

Unknown

Well it seems that

people in the gas industry are like the rest of us they have never heard of the WOBBE INDEX. I just received two e-mails from friends of mine who work for different gas companies and they never heard of this index. One of them actually works in gas supply.

Very strange I wonder if any one in Canada has heard of this????

Unknown

Oh Canada have you ever

heard of the WOBBE INDEX?

[Deleted User]

Yahoo results

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6777776

Have not read it yet, but looks intersting. Something that Tim could sink his teeth into.

ME