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• efforts to determine the best energy reduction project for a target manufacturing process;

• implementation costs of using the monitoring tools;

• efforts to analyze the cost-benefit ratio of the project against corpo- rate ROI standards. Depending on the selected

monitoring tools, the skill level of the staff, and the specific details of the facility, some of these costs may be trivially small but other costs may be significant. During the past 30+ years, many

Fig. 3. Measurements of the header pipe air pressure and power consumption after the compres- sors are turned off are used to determine aggregate compressed air leakage rate.

more sensing subsystems are included in the solution. Technical obstacles exist to add-

ing different types of sensors to supplement existing, commercial- off-the-shelf technologies (COTS) dedicated to measuring power use in a metalcasting facility. For example, to analyze furnace operations, melt temperature and melt weight may be needed in addition to gas or electric- ity consumption. Another example might be an efficiency improvement project focused on compressed air systems, in which header pipe air pressure and compressor outlet air flow measurements may be needed in addition to electrical power consump- tion data. Some widely used types of energy

monitoring meters may not be useful for energy efficiency projects due to their time resolution or the acces- sibility of their data. For example, electricity-use monitoring at 15-min- ute intervals between measurements (time resolution) will not be adequate to analyze some compressed air systems that dynamically change operating parameters in 2 to 5-second time intervals. In order to correlate power with these types of dynamically changing parameters such as air pres- sure and air flow, better time resolution is needed. Similarly, foundry furnace efficiency projects probably need better

38 | MODERN CASTING April 2015

than 15-minute time resolution to correlate temperature and melt weight with energy usage.

Although an initial energy effi-

ciency project may utilize a simple power monitoring data logger, the challenge of adding synchronous process-indicating sensors to a “black- box” dedicated power data logger can be significant. In addition to performing near-

simultaneous measurements of dis- parate sensors, tools must be easy to use, low-cost and provide broad data accessibility to be successful in identi- fying return on investment (ROI) validated energy savings opportuni- ties. If data are not easily accessible in real-time by facility personnel, the likelihood of an effective and success- ful energy project diminishes. Te process of identifying and val- idating energy-use reduction projects typically require energy-use monitor- ing tools. Costs associated with these tools must be included in the overall ROI analysis of energy efficiency improvement projects, including • the acquisition cost of monitor- ing tools;

• engineering training costs associ- ated with learning to use monitor- ing tools;

• the ongoing costs of retrieving power-use data;

• efforts to analyze power-use data;

types of sensors have become smarter through the integration of network connectivity features, mixed ana- log and digital signal processing capabilities, on-chip data storage, and other digital electronic features. Some of the digital features that have made smart sensors particularly useful include the integration of real-time clocks, threshold acti- vated alarms, virtual sensor creation through multi-sensor data fusion and CPU-based intelligent signal inter- pretation. Many of these advanced smart sensors are currently available as COTS integrated circuits. To better utilize smart sensor

technologies, a group of govern- ment, industry and academic sensor researchers have worked to create a family of standards for various types of wired and wireless smart sensors. Tis set of standards is known as the IEEE 1451.x family of smart sensor interfacing standards and provides a standard way to access data, format data and access electronic data sheets detailing various properties of the smart sensor.

Measurements in Metalcasting Te sensor interface hardware

platform described in this article is based on a derivation of the original IEEE1451.2-1997 smart sensor interface standard. Tis smart inter- face enables the use of COTS legacy sensors (not smart sensors) to have many of the properties of advanced, integrated circuit based, “plug-and- play” smart sensors. Tis approach was used to identify power usage and provide

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