Calculating line loss for natural gas

it's been my experience to set regulator valves in their mid range ...either extreme side of op's limits are to subject to error's..imho:

5 - 20 psi.. = 12.5 + 7.5 / - 7

gl

Hello again Melanie

I just posted reply to yours in General. As said there, I don't think it will help your bill to reduce the main regulator pressure. But to calculate pressure loss in the 1000 ft pipe need to know maximum flow (actual or corrected to 14.73 psia, but need to say which). Also is it ¾" or 1" pipe? it makes a big difference. Also please explain Max water column= 38.5". And what gas is it? In Europe natural gas is mostly methane, but I believe in USA it is higher molecular weight (hence higher density and higher CV per unit volume)

If you still need pressure loss, post details above and I'll estimate it.

Cheers........Codey

Hi Codey,

I am arguing the fact that they calculate in line pressure but they won't budge. Therefore my pressure setting DOES affect my bill based on their usage factor calculations.

They come to my usage factor using this formula:

(they take my "actual meter read" and multiply it by the below usage factor to get my "billed usage". If my meter reads 94, they bill me for 151! My neighbor's "set pressure" is only .25 so his usage factor is less than one while mine is 1.61 but they say mine has to be set so high because I have a large meter.

The max water column (I have three regulators on 3 buildings and the 38.5 is simply the max rating on each) may not have anything to do with the needed pressure, I was just trying to list all the numbers I could find.

I am in Colorado, USA. Natural gas. Atmospheric pressure is 12.22. 1" pipe.

I don't know how to calculate anything else :( I hope that helps. Regardless, thank you for your time!

The selling of gas is based on energy, BTU's (or therms). Your meter does not count BTU's, only cubic feet. Therefore, if a customer requires higher than 7"wc, then a factor has to be applied to the uncorrected reading, or meter reading, to result in a just compensation for the energy delivered. If you have them lower their delivery pressure while using the same amount of BTU's, your factor will go down, but your meter reading will go up, resulting in the same dollar cost for the same amount of BTU's.

Your situation reminds me of the fellow who kept his swimming pool so warm during the winter that steam was rising from the water. Yet he screamed when his gas bill was $400. Maybe the horse in the barn does not need that much heat.

My barn and side house are LOCKED OUT. No horses and no heat. I have a 2600 sqft home that never goes over 65degrees in the winter (we even have nails so they CAN'T go over 65 even if we wanted to!) and I don't use my fireplace because it is for decoration only! I eat 80% of my meals out of the microwave!

I don't have a problem with my meter read, my "actual usage", I have a problem with the multiplier they use to JACK UP my bill!

My neighbor has a 8200 sqft home and because his only has .25#, his bill and mine work out to be the same! AND he has a HUGE gas range on his patio, a GAS dryer, a gas fireplace he uses, a gas heated jacuzzi, and TWO water heaters! HOW CAN THAT BE RIGHT??????? His usage is higher but he doesn't have the multiplier so we end up paying the same. I refuse to believe this is correct!

It probably isn't right, there could be something wrong, but I doubt it is in their compensation calculation. Comparing actual usage numbers probably isn't a valid comparison due to his lower line pressure.

Have you checked for leaks on your side of the meter?

We have checked for leaks. And I guess that is the point, if my pressure is lowered, my bills should calculate the same as his! His meter reads 90, he pays for 90. My meter reads 90, I pay for 145! We come in off the same gas line from the street onto our property. It reaches his meter, than mine.

I won't accept that his gas quality can be any different than mine when it comes from the same line and simply travels 1000 ft to my house! If that is the case it has to be the meter and in that case, I want a different meter!!!

This is all over my head and I guess I will let the lawyers duke it out.

Hello Melanie

Various poster agree with me that in principle the company's approach is sound (however much you don't like it, understandably!)

But one thing might be worth checking - do you actually get 10 psig in your pipe? (after the meter and regulator). If lower, you are being charged on the calc for 10 psig but your flow reading is higher. Pressure could be low for 2 reasons:-

1) supply main is above 10 psig, but the regulator between the main and your meter is set lower, or

2) supply main pressure is low. Provided it is higher than you need (max 1.39 psig from your OP, perhaps less as this is max rating) plus a little for pipe loss, say 1.5 psig total, everything will still work OK (the regulator goes wide open as set for 10), but your reading is high by

(12.22 + 10)/(12.22 + 1.5) = 1.62.

Clearly 1.5 psig in the main is plenty for your neighbour who only needs 0.25 psig.

Failing that, maybe it's not your meter that's reading high, perhaps his is reading low!

The fact that his take-off point is before yours is irrelevant.

Cheers.........Codey

You could ask them to replace the meter, or ask them to prove the meter out and you could probably witness the test but I don't think that is what is wrong. I can sympathize with your frustration, dealing with a faceless corporate entity can be a nightmare, especially when they tell you "it is right because I told you so."

This next section you may already know so I apologize if it seems I'm talking down to you, that is not my intent.

I think a lot of the confusion is that the bill says "actual" usage. When an engineer uses the term actual to describe a gas volume, it means the actual volume taken up by that gas at the current temperature and pressure. Volume in a gas is inversely related to pressure (higher pressure = lower volume) and directly related to temperature (higher temperature = higher volume). Natural gas though is typically sold in "standard" volume, that is, the amount of volume that a given mass of gas would take up at a fixed pressure and temperature (typically 14.696 psia and 60 °F). The net effect is that the gas company is taking your "actual" usage and converting it to your "standard" usage because your "actual" usage is unique to your conditions and is not a reliable measure of how much gas you consume.

In your neighbor's case, he is running very close to the standard pressure so his multiplier is very low and his "actual" and "standard" numbers are almost identical. In your case, the pressure is much higher, so the mass of gas that passes through in your "actual" number is roughly double your neighbor's so your multiplier is more like 2 instead of 1 to get to your "standard" number. What that means, assuming the meter is correct, is that on a mass basis, a pounds of gas basis, you are consuming double what your neighbor is consuming.

Another way to look at it would be if you and your neighbor each had 1000' of pipe that was completely empty of natural gas and his regulator was set at 0.25 psig and yours was set at 10 psig and you both opened your meters for a little bit. Once you filled the pipe and then closed off the meters, he would have roughly half the amount of gas in his line that you would have in your line. He could run his furnace for one day and you could run yours for two days (assuming they are identical), primarily because he runs his main line at such a lower pressure.

If you suspect that you should be using less gas than him (standard basis), then I would start checking for reasons why yours would be higher like leaks, old appliances, bad insulation, etc. I wouldn't get a lawyer involved (any lawyers reading this, I'm sorry) because they tend to make stuff more complicated and it will end up costing you money for them to tell you there isn't much they can do.

I have no problem being talked down to on matters of which I have no formal education! Your explanation was terrific. I guess I don't understand that merely if the line holds more gas, per your example, yet I am not using it, why am I being charged for it? If I have a resevoir that holds 500 gallons but only drink 2, why should I have to pay for what sits in such a large resevoir? If I am pumping gas and fill my car with 2 gallons, why should it matter how large the tank is holding the gas?

I look at it this way...why not set everyone's home up with a large meter, high pressure, and then charge everyone at my rate? They'd make a lot of money that way! lol

All these answers have been very helpful in helping me to understand their calculations as I was confused at the fact the people who build the inner workings of the meters said:

The equation is simple...Amount you use x gas therm (energy content value). Pressure has nothing to do with energy content. The amount you use is the issue and has to be independent of pressure. Each orifice or regulator has a min. line pressure to operate properly. Once that is exceeded they are doing what they are supposed to do and that is regulate the gas flow.

Now after reading all of this I am fine accepting the gas company's calcs. However, the issue still lies with the fact I want the smaller set up. Then my resevoir is smaller! lol I am also switching out my gas boiler to an electric...that should help and certainly lessen the load.

The lawyers are already involved...court case is in June. They have offered to settle based on the fact they admitted to billing errors and incorrect rates (and offered me compensation to cover the errors and headache of 15 months of calling and research), however I still want the meter/pressure situation reviewed before I sign.

Thanks again. You were a phenomenal help.

If the meter is incorrectly set up and they are billing you incorrectly, then the suggested fixes I had probably don't need to be checked.

Always glad to help, it is nice to have someone that responds to questions and keeps in touch with the thread, you wouldn't believe how often someone asks a question and we get no response after we start to answer.

:) I can't imagine not responding to those who go out of their way to help!

For all those who don't respond...THANKS!!! Keep it up for those of us who do care and truly appreciate it!

Melanie

I'm trying to help! Ref my post #15 - do you have 10 psig at your meter? It's not difficult to measure and if you have less you are being overcharged. You don't need to follow my reasoning and calculation (though I imagine you do), but if anybody doesn't agree they would likely have said so by now.

One poster suggested it may not be 10 psi but 10" wg. That is above the minimum of your regulator ranges so if it is 10" wg your kit would probably work OK (depending on the actual pressure setting). 10 psi is very high for a domestic gas supply, 10" wg is a lot nearer the norm.

Cheers.......Codey

Hi codey,

The 10psi from the meter is probably required to be able to deliver the volume required through a 1000 ft of pipe and then to 3 separate gas consuming units where it is regulated down to the working pressure for those units. The owner has neglected to say what the maximum demand is when all units are operating at the same time , quite likely 5psi could not deliver the volume required through such a long pipe therefor 10psi is quite realistic. The owner is going to have a lot of problems trying to dispute these requirements and the charges applied unless there are leaks or incorrect pressure setting which is easy to confirm.

Hello garth

Did a quick headloss check on 1000ft of 1" pipe. Assuming methane, at 5 m³/h (176 cfh). This flow gives about 70 kW so likely to be generous. Δp = 0.156 psi = 4.3" wg. If the gas is higher MW flow for same power is lower so lower Δp. As you say there is some loss for the regulators (but not added together, they're in parallel) but I don't think my idea as a possible explanation is ruled out.

Cheers.......Codey

Hi Garth,

Not sure what you mean by maximum demand, but here are the only specs I know...

Barn (regulator: 6-15inwc...only gas requirement is a 32,000 BTU water heater)

Side House (regulator: 6-15inwc...only gas requirement is a 32,000 BTU water heater, no cooking set up, etc.)

Main House (regulator: 5-8.5inwc...270,000 BTU boiler, 32,000 BTU water heater, 2 -27,000 BTU fireplaces, gas range in kitchen) *The fireplaces do not get used as they are for decoration only but I realize they have to calculate for "potential load" so I listed them.

The barn and the side house are "locked out" so no gas goes to them...but as previously mentioned the gas company says they have to have a set up for potential load. I don't understand why it couldn't be lowered and then if I ever had them "unlock" the line they could bump it back up. Would it make a difference if I had the meter moved closer to the buildings so there was only 100 ft between the meter and the house?

Thanks!

Thanks for trying to help! The gas company sticks by the fact I have 10psig at the meter. I have ordered an independent line pressure test for next week, both at the meter and at my house.

They don't consider my house "domestic" due to the fact I also have lines running to an 8000 sqft barn, a 1000sqft side house and my main house, 2600sqft. Although the barn and side house are "locked out", so no gas goes to them, the gas company says I must keep the same meter config due to the "potential load".

I think I am going to follow someone's advice about looking into moving the meter closer to my buildings, hence lessening the pipe length.

In Alberta, Canada the gas is billed CF used X Btu/cf x by the current price on the open market for gas averaged over a set period. We also have a choice of who we want to gas from. Free market.

What the heck does the atmospheric pressure have to do with the gas meter. A gas meter is an enclosed piece of equipment that has a wheel that allows a set volume of 'gas' per chamber and counts the number of turns of the wheel, which you see on the face with all those little needles. The gas meter outside here is a Rockwell International Type E61 and is totally hermetically sealed complete with tamper proof wires. There is no vent to atmosphere to compensate for any changes in the weather that might occur.

The gas company might be charging you at a commercial rate, but then that should be lower. OK you got me with that atmosphere stuff, you need to get hold of your Government and start screaming on this.

You do not appreciate how psi at 5000ft above sea level affects the calculations neither does the person who gave you a good answer.

The meter measures volume not pressure, imagine the meters bladder as a balloon if you fill this with 1cu ft of gas at the local atmospheric pressure of 12.22 psi, then take this balloon down to sea level it will shrink in volume to something less than 1cu ft. But it has the same amount of Btus in it. Therefore if you now fill it with more gas to 1 cu ft it will contain more Btus of gas, so the calculation takes this into account that at 5000ft above sea level the customer receives the correct billing for the lower amounts of Btus she receives for every Cu ft of gas received.You can also see that the meter balloon filled with 10psi instead of 5 psi would would have twice as many Btus and the gas burners are burning Btus not pressure or Cuft so whether they are delivered at 5psi or 10psi is irrelevant apart from operational requirements.

If you work out the formulae for 14.73 psi at sea level you will see the multiplier factor is larger ie there is more Btus of heating value in 1 cu ft of gas than at 5000ft.

If the customer suspects she is paying to much it would be a good idea to shut down all the gas burning equipment but leave all valves open, if there are any leaks the meter will indicate consumption somewhere on the system this leakage can then be isolated by closing valves to the various sections until the meter stops moving.

Thanks for the explanation, but if you look at my calculations it's based on BTU's per cubic foot. The gas company here sells btu's delivered, not cu ft. Sometimes the gas company will revise the price per BTU/cu ft, depending on how good or bad the gas is, being delivered. We live in a gas field, so the suppliers switch suppliers depending on price, futures etc, etc... and stuff changes.

I'll phone the guys at the gas company tomorrow and ask them to explain the atmospheric compensation thing to me. I realize what your trying to say, but for some reason, I'm not able to get my head around it. Maybe it's because Boston Bruins lost in OT. lol

Garth,

I love the suggestion about shutting everything down and having someone at the meter to check movement.

Now I have a weekend project before all the pressure tests and meter accuracy check.

Thanks!

Give the details as asked for a rough estimative. But keep in mind that the pressure loss is primarily related to the gas velocity and so your consmption. The worst case will be your higher possible consumption. If it varies too much, maybe the calculation will not be usefull. In my opinion, you should concern about it only if you're experiencing malfunction to any equipment due to low inlet pressure. In this case, in high flow circumstances, a larger pipe could be needed, or a pressure regulator or intermediary valves with higher CV.

Psi is similar to voltage, it's present, but doesn't really do any thing until you have flow. The flow of gas is what you need to be looking at. How much is required at the barn and at the same to the house. The main gas line, is much line the power line outside, its at 14,400 Volts. Why would you tell the power company to lower the voltage one the main line? If you are having problems with the flow or pressure, then I would look at your regulators. Most regulators are sized to psi-flow-psi, not psi-psi. In other words your regulator can handle the psi it might not be able to handle the flow required. (undersized)

I agree. They don't. They are charging me by calculating in the line pressure!

I don't understand how the line pressure should have anything to do with my usage! They will not budge they say the commission approved their calculations but I DON'T UNDERSTAND THE LOGIC!

My neighbor's calculation is the same but his "set pressure" is only .25 and therefore his usage factor is only .91! They say I have to have a larger meter because of the three buildings (barn, house and side house). They all have regulators so what does the line pressure have to do with anything!!! I just don't understand but if I have to play by their rules, I need to argue and PROVE that my line pressure can be lowered to 5psi. My neighbor's and my meter are SIDE BY SIDE and come in off the same line from the street! HIS METER IS FIRST! Therefore they are bumping up my pressure AFTER his meter. UGH. I'm so frustrated. I appreciate your time~!

Here is their calculation.

Flying high has explained it quite well but you have not grasped the significance of the pressure factor.

Simply one cubic ft of gas at 10psi has twice as much Btus as one cubic ft of gas at 5psi. So your meter calculation has to be factored to allow for this delivery. If your equipment consumes X amount of Btus [ assuming your plumbing can deliver X amount of Btus at 5psi ] you will have to pay the same amount. so you are not being robbed.

The regulators at the end of the line regulates the pressure down to the psi required by the equipment to work properly they don't care what pressure they are supplied with so long as the inlet pressure remains above the outlet pressure.

I guess I am not grasping it. I simply don't believe a house 1/3 the size, that uses 1/3 the gas can possibly cost the same. It is illogical.

How a 2600 sqft home and an 8200 sqft home costs the same is beyond me (when he uses MUCH more...I don't have a gas dryer like he does, I don't have a jacuzzi like he does, I don't use a gas grill like he does, I don't use a fireplace like he does and I have 1/3 the space to heat!!!).

Calculations or no calculations, SOMETHING DOESN'T ADD UP!

Why do you care what their reg is set at? The billing will be the same for the same cf you use, as they use a different factor to account for the different pressure. Like other posters have said, to calculate pressure drop, you've got to know the flow in each section of pipe; the length and pipe size of each section. Also, depending on how large your load is at the end of the piping, 5# at the meter may not be adequate to provide a large enough P1 inlet pressure at the final reg for it to pass the load it needs to pass.

I would say that they are using the line pressure to correct their meter measurement to give them a better idea of how much gas you are actually using. They probably sized the meter with a reference pressure of 14.73 psia and when the downstream pressure is 10 psig, they have to correct the calculation upwards to get your actual gas flow.

If you lowered the value to 5 psig, the "fix" would go down but the pressure drop across the meter's orifice (or whatever it is that they use to indirectly measure your flow) would increase correspondingly, leaving your bill unchanged. The pressure correction is really trying to compensate for the density change in the gas from ~0 psig to 10 psig. Going down to 5 psig might make them tinker with the meter as well (change out their measuring device).

I wouldn't worry very much about the line loss in 1000' of pipe, but if you really need it, we would have to have your expected maximum flow rate.

Setting the regulator to the minimum on the range could create some adverse downstream affects, not to mention that the main regulator would operate on the very low end of it's spectrum which could cause some pressure fluctuations that you don't really desire. Your other regulators (the houses and the barn) might be sized for the upstream pressure to be 10 psig in which case lowering it to 5 psig might require you to put in new regulators for those locations.

The gas company is ultimately lazy and resetting the regulator would make them reset their billing structure/meter and due to their laziness and greed, would probably charge you a chunk of change to make this happen.