The EMIS Audit

The Meter Types Appropriate for Function assessment is to make sur e that the
meters being used have the correct range, measurement units, and process
conditions for the application and surrounding environment. Facilities are scored on
a 0 to 10 scale based on their ability to use the appropriate meters for the
application.
The Meter Installation Satisfactory assessment is to make sure that the
mechanical installation of the meters is correct, the metering s ystems are eas y to
maintain and calibrate, calibration records are kept, and that the piping is
appropriate for the m eter. Facilities will be scored on a 0 to 5 scale based on thes e
requirements.
Meter Accuracy and Repeatability is the final assessment for utility meters. As
meters start to age their performance will start to decline without the proper
maintenance, calibration and periodic inspections. Reference materials that illustrate
proper calibration and maintenance procedures should exist. Also, external factors
and process conditions can contribute to errors in measurement.
Some common things to remember when ass essing meters are:
� Meters that measure volumetric gases or vapors often require external pressure
and temperature compensation. Natural gas measurement using turbine
meters requires pressure and temperature compensation to reference
conditions.
� It‟s ideal to measure mass rate when the desired outcome is mass total.
Steam for example is typically measured as mass rate and is then converted to
energy total.
� The range of highest to lowest flow rates that can be measured are called
rangeability or turn-down ratio.
� Metering signals need to be correctly compensated in the host (PLC) s ystem.
An example would be meter k -factor. The meter k -factor is used to convert
pulse trains into measured volumes.
� The ratios of PT (voltage or potential transformers) and CT (current
transformers) must match the receiving devices.
� The ranges of PT and CT must be appropriate for measurement against name
plate ratings on electrical equipment.
� W hen serial data is transmitted, requirements to handle roll -over of any register
values in the meter or host (PLC) system must be confirmed. An example is
when passing short integer values.
4.5.2 Utility Drivers
Utility drivers are factors that can influence how much energy is being used for a
given EAC. Three types of utility driver are recognized:
� Production Drivers
� Environmental Drivers
� Operational Drivers
Production drivers are typically:
� Production volumes;
� Product type, if different operating conditions exist based on product type;
� Building occupanc y hours .
EMIS Ma nu al Page | 35
Part A