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# What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 12:52 PM

A friend of mine replaced his boiler: one of the checks he had to do was to measure the gas flow with the boiler running at its maximum capacity.

This is the display of his gas meter:-

So he counted the revolutions of the rotating dial over a period of time then multiplied by the figure on the meter "0.071 ft³/REV". Seemed reasonable but the result he got was much too low. After a little more research he discovered that one full revolution of the dial indicates 1 cubic foot, and his calculation produced about the right answer.

The question is what does "0.071 ft³/REV" mean?

I found this in a document about re-establishing the gas supply after doing any work.

____________________________________________________________________

Purge volume = 5x the meter badge capacity for installations with pipe up to 28mm

e.g. ( imperial meter(ft³) = 5x 0.071ft³ = 0.355ft³) (metric meter(M³) = 5x 0.002m³ = 0.010m³)

____________________________________________________________________

In fact 0.071 ft³ is about 2 litres so both these meters have the same "badge capacity", but, what does that mean?

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#1

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 1:26 PM

I think that's how many cubic feet per second the meter is rated at....

http://www.gb-gas.co.uk/gb-gas%20QuickReferenceGuide2014.2.2.pdf

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#2
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 2:28 PM

0.071 cubic feet per second is about 20% more than the 212 cubic feet per hour printed just above, and, which sounds more likely to be the rating.

Hmm that's interesting 212 cubic feet is very close to 6 (6.003171) cubic meters, and, 0.002 cubic meters per second is exactly 20% more than 6 cubic meters per hour, so it looks as though these two figures are related, and the original design was metric.

Still no real idea what they mean and why "/REV"?

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#3
In reply to #2

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 2:54 PM

Maybe it has to do with pressure...typical pressure vs maximum pressure...?

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#5
In reply to #3

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 10:46 PM

No, consumer gas meters measure the volume of gas delivered regardless of the flow rate or pressure (up to the limits of the meter of course).

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#23
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/13/2018 4:34 PM

Yes but the meter must have a window of working pressure that it is designed to work with....at a higher pressure the meter will deliver a higher volume per second....

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#25
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/13/2018 6:46 PM

Each service has a pressure regulator/flow limiter installed before the meter.

In case that fails, each meter has an upper limit on the pressure and flow rate that the meter can pass, said limit being higher than the pressure that is available in the street main.

Also, each appliance has an orifice that provides back pressure that further limits the flow under under normal conditions.

If a pipe inside the house is severed completely then see the first and second sentences.

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#26
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/14/2018 3:39 AM

That's right. Pressure after the regulator is usually 20mb in UK. The meter reads actual volume, so if the pressure were higher the mass flow, hence heat produced would be higher for a given volume reading. I don't know whether they quote GCV at standard pressure (atm or bar) or at that + 0.02, but difference 2% is probably about the accuracy of the meter.

Some appliances eg gas hobs have an orifice or adjustable valve, others, like boliers have an additional pressure regulator. So the pressure at the burner is unaffected if the meter pressure changes (within design limits).

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#4

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 4:23 PM

The question is what does "0.071 ft³/REV" mean?

I believe that the little rotary dial is only to indicate that gas is flowing when it is too slow to change the numbers. The value ".071" is 1/14, the amount of gas in cubic ft for each rotation of the metering device inside, and 14 is the gear ratio to convert to cubic feet. It seems to be a standard for gas meters.

http://www.abellcombustion.com/PDFs/x_Metris250GasMeter.pdf

Just my guess.

https://en.wikipedia.org/wiki/Gas_meter

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#6

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/09/2018 11:23 PM

The ".071ft3/rev" is known as the meter constant. The rotating dial pointer indicates the instantaneous flow, the time for a single full revolution indicates how long it takes for 0.071ft3 to flow. The "digital" numbers to the left indicate the total volume over time.

A trained technician with a stop watch can tell you how much gas passes through the meter by timing a single rotation of the pointer; i.e., if it takes 6 seconds then .071ft3 has flowed, .71ft3 will flow in one minute, and 42.6ft3 will flow in one hour, indicating an instantaneous flow rate of 42.6ft3/hr. The register to the left 4024.9 would increase to 4067.5 after an hour passes. All of this assumes that the speed of rotation doesn't change during the measurement interval.

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#7
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 6:37 AM

I don't think that's right. As the OP said, the pointer does 1 ft3/rev, confirmed (or at least corroborated) by the 0.5 halfway round.

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#10
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 9:24 AM

The 0.5 mark is simply half of one revolution, regardless of what one revolution means. For this particular meter, moving the pointer from 0 to 0.5 represents a total volume equal to 0.0355ft3 of gas, time has no influence unless you're calculating the flowrate.

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#13
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 2:09 PM

But in the original post the OP said

"So he counted the revolutions of the rotating dial over a period of time then multiplied by the figure on the meter "0.071 ft³/REV". Seemed reasonable but the result he got was much too low. After a little more research he discovered that one full revolution of the dial indicates 1 cubic foot, and his calculation produced about the right answer."

We don't know whether he used an independent flowmeter, or just watched the rotating dial and the RH moving digit (the one reading 9), which would appear to be a bit of a circular argument, but he'd notice if it was a factor 1/0.071 = 14 out. I agree the 0.5 is superfluous, we hardly need telling that point is one-half turn, whatever the measurement is.

And looking at the pic it's a good bet the RH digit advances 1 digit for 10 full turns of the pointer. The main 4 figures show consumption in 100s ft3, which is how it was usually expressed, at a GCV 1 therm = 105 BTU/100ft3.

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#15
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 2:32 PM

Codemaster is right: I thought I'd explained in the OP that my friend determined that the rotating dial was 1 ft³ per revolution, which is why we couldn't understand the use of "/REV" on the label.

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#16
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 5:20 PM

And how did your friend determine that, by using a calibrated source or from a forum on the internet?

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#17
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 6:55 PM

Whether or not he had an independent, calibrated flowmeter, he would have a good idea what the flow should be at maximum boiler output, so he would be able to tell whether the dial was 0.071 or 1 ft3/rev.

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#18
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/11/2018 5:04 AM

Exactly.

The boiler was clearly working "reasonably well": by using 1ft³/rev in the calculation he got the expected flow rate.

And of course it doesn't take long to confirm that ten revs of dial causes an increment in the 10 ft³ red digit.

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#8

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 6:47 AM

It seems a bit odd. I'd be tempted to guess it's the volume for one rotation of the metering mechanism, as Rixter said in #4. Though putting the figure on the meter causes more confusion than help IMO.

But a quick google says most modern meters are diaphragm type, if this is one it would be ft³/stroke, not /rev. But meters nowadays in UK are in m3, so maybe it isn't a diaphragm type, but a nutating piston or other rotary type.

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#9
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 9:13 AM

The actual mechanism is irrelevant, the revolution being referred to is the rotation of the pointer, which is directly turned by the mechanism, a single cycle of which is known as the stroke. The pointer is also a safety feature since the slightest movement of gas through the mechanism will cause the pointer to move.

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#14
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 2:20 PM

Yes, that's pretty much what I said. But a single cycle on this meter is not known as the stroke, it says per rev. Not that it makes any difference what you call it. You seem to be agreeing that the 0.071ft3 per rev (or stroke) relates to the internal mechanism, not the rotating pointer.

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#19
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/11/2018 10:31 AM

I see the source of the confusion, there are different styles of meter registers. The one in the OP has a meter factor next to the dial, the other style does not, it does the multiplication for you by clearly stating what one revolution represents, as these two show.

Misunderstanding corrected!

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#20
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/11/2018 11:25 AM

OK thanks. I remember those antiques well

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#11

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 11:40 AM

The meter reads out in cubic feet.

The .071 cf/rev is the volume of the meter cavity. The guidance to purge 5 x the badge capacity means that if you were connecting and purging, you would need to run .355 cubic feet through the meter to fully purge it. There is likely a 14:1 gear reduction between the internal mechanism and the pointer shaft and a 10:1 reduction between the pointer and the dial currently reading 9.

UGI Meters is currently dissolved and was part of a big kerfuffle concerning inaccurate readings in the UK that allegedly overcharged utility customers.

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#21
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/12/2018 12:46 PM

Have you ever tried to find out what a unit of gas is? I have tried and no one could or would give me a strait answer, I asked whether it was a cu ft or part there of & they start with, Its the amount of gas it takes to raise the temperature of a pint of water by so many degrees, and still not what that amount is, it's all a con.

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#22
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/13/2018 10:51 AM

I don't see what the problem is. Nowadays in UK it's measured in m3, and you could call that a unit. The supplers quote the (gross) calorific value, usually around 39 MJ/m3, though it varies a bit depending on the make-up of the gas.

To complicate things, they charge per kWh, so MJ is divided by 3.6 for the bill.

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#27
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/14/2018 12:07 PM

I've heard several times of natural gas being measured in therms, defined as "a unit of heat equivalent to 100,000 Btu or 1.055 × 108 joules". However, it doesn't directly cross to cubic feet or cubic meters as the pressure, moisture content and purity all have effects on the final heating value. I worked at Portland General Electric for a while and they had issues from time to time with moisture, particulates and low heating value on Canadian natural gas that they were purchasing at the time for a gas turbine generating station. They were at the tail end of the pipeline and even had issues with air that had somehow been injected into the pipeline, probably from a valve operator somewhere along the line.

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#28
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/14/2018 12:39 PM

Just out of interest, who did you ask? Even in the days when the sun never set on the Union Jack, I can't imagine anybody coming up with a definition like that .

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#29
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/17/2018 6:38 AM

The local gas company, & no matter how many times I asked, "What does it mean in actual cubic capacity" and no one could or would tell me.

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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/17/2018 6:50 AM

Pathetic! You wouldn't expect the secretaries to know, but you'd think they could dig out somebody with enough technical knowledge to help.

But I don't think it's a problem in practice. Your consumption is measured in m3 (if it's an old meter reading ft3 they'll convert the reading to m3), the CV is given in MJ/m3, to work out the heat you've had, and you're charged for that (actually per kWh, as I said in #22)

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#12

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/10/2018 1:52 PM

Surely 0.071ft3 is the amount of gas per revolution like it says on the dial.

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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/13/2018 4:43 PM

Smoke and mirrors,,,,just pay the bill....haha

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#31

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/24/2018 1:01 PM

I sent the same question to the "media relations" contact at UGI and he forwarded it to the technical training manager. He just sent me this reply:-

______________________________________________________________________

Sorry for the delay in answering I was on 2 weeks vacation and just getting caught up.

To answer you question a badge is a term used in Europe and simple means the amount of gas a meter is rated and design to pass with zero pressure drop in the line and is listed on the tag or badge.

With that said the meter photo you sent is listed for 212 Cubic Feet of gas per hour. You can get a hire capacity with a slight pressure drop in the gas fuel line. The test dial showing to the right is what we call a ½ foot dial and it is used only to set up and check equipment and test the fuel line for leak on a lock up 10 minute test.

How to calculate:

One revolution is ½ cubic feet or 500 btuh. It is a test dial not a badge.

Clocking a gas test dial:

Operate just the appliance to be calculated.

Because of the btuh(hour), 3600 seconds in one hour.

Example: one revolution takes 15 seconds, 3600 divided by 15 = 240 x 500 (btuh) = 120 cubic feet or 120,000 btuh

New gas equipment is normally very close to it’s rating plate but you do the meter test dial clocking test to be sure it is perfect and not over or under gassed. It within 10% no harm will result but it does make a difference with the furnace or boilers performance during peak times.

If you give me your address I can send you a simple tip card chart we use to test and check input on equipment.

Regards,

___________________________________________________________________________________

Needless to say, I will write to thank him, but, to point out that the bit which really threw us was the .071 ft³/REV

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#32
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### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/25/2018 6:00 AM

I wrote back:-

Thanks ,

Hope you had a good holiday.

All good and useful stuff, but, the bit which confused us was the “ ·071 ft³/REV “ .

We’re guessing that that’s the volume of gas needed to produce a full “cycle” of the internal measuring mechanism, and, that that is geared down by 14 to produce a full revolution of the cubic foot dial (we think it’s a full cubic foot rather than a half).

Thanks again for taking the time to reply.

Best Regards

And very quickly got this reply:-

You are correct.

Keep in mind the pressure in the meter and your fuel size etc. has a bearing on the input results.

_____________________________________________________________________

By coincidence the utility company replaced my friends meter yesterday (we think they suspected the old one had gone out of calibration because he recently got photovoltaic solar panels with an attachment which routes any spare capacity to heating water). The “new” one is just a refurbished old one, but, it is all metric; the “badge says “6 m³/hr”, and, “V 2 dm³”. Clearly 6 m³ is almost exactly 212 ft³, and, 2 liters is very close to 0.071 ft³. But in this case the V clearly stands for volume.

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#33
In reply to #32

### Re: What is the Badge Capacity of a Gas Meter, and Why Does it Say /REV?

05/25/2018 7:06 AM

You got a poor answer first time, and the second not much better IMO.

Of course one rev is a full cubic foot, not a half. You've checked it against the 10ft3 digit.

"Keep in mind the pressure in the meter and your fuel size etc. has a bearing on the input results." is a typical bit of waffle. The pressure in the meter is determined by the upstream regulator and stays practically constant. What does he mean by "your fuel size etc"? And "input results"? The meter gives an output, not an input.

Your friend's meter looks like a metricated version of the earlier model. Still can't see why they bother putting V 2 dm3 on the front.

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