Natural Gas Flow Measurement Meter
Natural gas is a fossil fuel composed of a mixture of hydrocarbon gases. The primary components are methane, ethane and propane. It is the cleanest burning fossil fuel, producing byproducts of mostly carbon dioxide and water vapor. Natural gas provides approximately 25% of the United States’ total energy consumption. The United States annually produces about 24% of the world’s natural gas supply. Natural gas is used extensively in industrial and commercial applications, as well as widespread home use. Natural Gas flow meters from Eldridge Products can be very useful in the measurement of natrual gas flow.
Composition & PropertiesAs stated above, natural gas is made up of many hydrocarbons. Although natural gas is primarily a mixture of methane, ethane and propane, the remaining gases and their percentage of the overall composition can vary greatly. For example, the trace levels of H2S in the mixture sometimes lead to the natural gas being labeled as “sweet” or “sour”. However, the typical gas composition and the common range of variation are:
Sulphur odorant: 5 mg/m3 typical
DistributionNatural gas gets to the consumer in three steps:
Measurement and Heat ValueNatural gas is often measured in British Thermal Units (BTUs). One BTU is equal to the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit at atmospheric pressure. One cubic foot of natural gas has an average heating capacity of approximately 1000 BTUs. The actual heating capacity varies across the country, and from time to time at any given location, due to the previously noted variations in the gas mixture. It is typical to see variations of +/- 25, 50, or more BTU for a range of 950 to 1050 BTU’s. The utility company’s meter at the building exterior measures the consumed volume in hundreds of cubic feet (CCF); however the consumer’s bill normally measures the consumption in therms, where one therm is equal to 100,000 BTUs.
Gas BillingCustomers are billed by taking the gas meter reading in cubic feet and converting this value to therms and applying a thermal factor that is the product of the heat value of the gas times the gas density.
The formula for therms is:
Assume that the heat value is 1025 BTU’s per cubic foot at 2.5 PSIG:
The energy value of the gas in BTU’s is normally reliable, provided the utility company measures this value throughout the year and integrates it over time. However, the gas density due to pressure makes up the largest portion of the billing or thermal correction, and this is the most likely area for billing mistakes from the local gas utility. Consider the following example:
Could this really happen?Not only can it happen, but it happens daily throughout the country! Natural gas consumers who have purchased flow meters to audit the gas utility have, on a number of occasions, found discrepancies between the billing totals and flow meter totals. Upon further investigation, they have found the wrong gas density being used in the correction for the therms energy value and therefore the subsequent calculations for their utility charges. Depending on the total monthly usage, these discrepancies can be significant, resulting in artificially and inaccurately high overall operating costs.
Submetering the natural gas usage at strategically selected points in a facility shows how much gas is actually used at each metered location or work area and provides an overall total for the facility. This total is compared to the utility’s billing total as a means of verifying or disputing the charges. The key element in efficient submetering is a flow meter that measures the natural gas flow accurately without duplicating the utility company’s need for complicated and potentially erroneous corrections based on actual gas temperature and pressure. Thermal natural gas mass flow meters, such as EPI’s Master-Touch™, are ideally suited to this purpose. Contact Eldridge products today to learn more about natural gas flow measurement.