Natural Gas Conversion Units

Hello aikhh,

A normal cubic meter (Nm³) is the metric expression of gas volume at standard conditions and it is usually defined as being measured at 0 °C and 1 atmosphere of pressure

A standard cubic meter (Sm³) is the metric expression of gas volume at standard conditions and it is defined as being measured at:

by DIN 1343, a temperature of 273.15K ( 0°C)
by ISO 2533, a temperature of 288.15K (15°C)
and 1 atmosphere of pressure.

mmBtu is a different measure altogether. It a measure of the energy given by the gas when it burns.

Hope this helps,

Mike

Dear Mikerho,

Thank you very much of you explaination.

Regards

Mr.Mikerho has answered well. use following with your Gas rates for Gas mmBtu calculation.

CALCULATION COST STEAM/HR AT BOILERS

BASED ON GAS RATES JULY 1^ST.2008.

(BASED ON THERMAX TWO OF THOMSON COCHRAN MAINTENANCE MANUAL)

JULY 2008:

15000 LB/HR(6800 KG/HR) = 19.6 X 1,000,000 = 19,600,000 BTU

1 CFT GAS PRODUCED = 970 BTU

CFT = 19600000/970 = 20206.19 CFT

MMBTU = 20206.19 X 1000/ 1000000 = 20.21 MMBTU

AT 80% EFFICIENCY = 20.21 + 4.9 = 25.11

Cost per 1 MMBTU = RS. 329.54 JULY 1^ST. 2008 RATES OF 31% INCREASE

COST OF 24.5 = RS.329.54 X 25.11 = RS.82743.75 /HR FOR 15000 LBS/HR

COST/LB STEAM = RS.0.55/LB STEAM

COST/KG STEAM = RS.1.213/KG STEAM

COST/T STEAM = RS.1213.63/T STEAM AT 80% EFFICIENCY

Hi aikhh,

Nm3 and sm3 are unit for gas flow rate at prefixed condition.

Nm3 indicates Gas flow rate at normal condition i.e. 1.0 atm pressure and 0 deg C. While, Sm3 indicates Gas flow rate at standard condition i.e. 1.0 atm pressure and 15 deg C. So 1 sm3 = apx. 1.05 Nm3.

Now MMBTU is milion metric British thermal unit indicates energy value of Hydrocarbon which varies based on Gas composition. For typical NG composition i.e 90-91 % methane, 4-5% ethane, 0.5% N2 and other C3,C4 you can consider value as 39000 Btu/scm.

At any variation of pressure if unit are given in sm3 or nm3 then they are already standardized but you can convert them also in M3 by taking into account ideal gas equation P1*V1/T1=P2*V2/T2 where 1 can be considered standard condition and 2 can be considered as pressure at which you want to calculate volume.

I hope this will solve your purpose.

Somewhere on the bill for the gas used will be found a number giving the average calorific value of the gas supplied. The tariff will be based upon the calorific value supplied, and not on the absolute volume supplied (which varies with pressure, of course). The calorific value of the gas is the missing cog in the machine.

Hi,

Well done PWS he added the missing link. You need three parts to calculate the cost only the volume (Normally at 1atm and 15C) the Calorific value and the cost per unit.

You may find on your bill that a correction factor of say 1.024 has been applied to the 'metered' volume this will be because your meter doesn't justify having a pressure (and temperature) compensator on board; this usually happens in large commercial/industrial meters and therefore they are making an allowance for the upstream supply conditions.