Gas Metering: Confusing Volume Units

Gas metering installations have configuration requirements that if not followed can lead to inaccuracies in reporting.

CHP waste heat boiler

With ever increasing utility costs, carbon taxes and resource scarcity the importance of utility metering is now greater than ever. However correctly metering utilities within a site is more complex that generally thought. Whether it be for Electric, Steam, Water, Gas or Air the requirements and installation conditions can have major effects on the effectiveness of your metering installation.

In this series of metering articles we explore some common examples of where metering installations are wrongly configured. In industry these types of mistakes can have major implications on the accuracy of your reporting. In this edition we explore gas metering.

So what needs to be considered and how could it affect your site?

How is natural gas measured?

Natural Gas supplied to your site is measured and billed in ‘standard metres cubed’ (Sm³) with the calorific value of gas also provided in MJ/Sm³. ‘Standard meter cubed’ is gas at conditions of temperature: 20 °C, pressure: 1.01325 bara.

However, typically sub meters such as those used on boilers provide readings in ‘normal meters cubed’ (Nm³). This is gas at Temperature: 0 °C, Pressure: 1.01325 bara. To change between the two a multiplication factor must be applied.

Why is this significant?

Consider the following example: A utility manager has some new boiler gas meters installed without understanding how to collect the data correctly according to the meter output units and pressure conditions. The gas in the sites M&T system is incorrectly reading in normal metres cubed. Since the conversion has not been applied, when the gas savings and boiler efficiencies are reported for the year, gas consumption has been understated, therefore delivered savings are overstated.

Where assumed efficiencies are applied to volumes of gas burnt in Boilers or CHP engines for use in energy supply contracts, misunderstanding of gas units can lead to big over (or under) charges.

A lack of knowledge in gas conversions can also lead to significant errors in reporting. This can also mean data provided for carbon tax purposes, CHPQA and EUETS could be inaccurate.

What’s the solution?

When collecting meter data into M&T packages a full understanding of the meters output and operating conditions is required to report data accurately. Applying the correct factors according to variables such as pressure and temperature is one of several important considerations for accurate metering.

How can we help?

Our core focus is improvement in identification, reduction and control of product losses, energy water and effluent. We have experience in scoping, selecting, installation and commissioning of all types of utility metering. Through well designed metering solutions we make sure the greatest savings are delivered and the best value is delivered to our client.