10.3.1 Indirect Energy

Indirect energy in manufacturing is defined here as energy consumed by utilities of an assembly system. This includes energy consumed to maintain the environment such as lighting, heating, or ventilation. Frequently, indirect energy accounts for the vast majority of the overall energy consumed and should be considered for energy improvement gains. While indirect energy can be a large portion of the overall energy consumption, the direct energy related to production and assembly is the main focus of the remainder of this chapter.

10.3.2 Direct Energy

Direct energy is defined here as energy that immediately contributes to the assembly of components. It is further classified into value added and non-value added energy consumption, Figure 10.2. This has also been labeled primary and secondary energy or process and auxiliary energy [10–12]. Neugebauer et al. [12] focuses specifically on the use of this strategy for energy analysis of an assembly operation. Assembly processes are classified as primary (value added/process energy) and secondary (non-value added/auxiliary energy) energy consumption sources. Their approach is based on Lotter’s [10] method, called P-S analysis (Primary-Secondary).

Joining is the primary direct energy process occurring during assembly that is value added, and is generally supported by non-value added, direct energy processes such as manipulator positioning or robot movements. A number of well-recognized techniques for joining parts and subassemblies include mechanical, adhesive bonding, welding, brazing, and soldering. These techniques and their related energy consumption information are introduced in Section 10.4. The energy consumption of each technique differs due to the technology and auxiliary equipment required. When evaluating the energy consumption of these joining methods, consideration should be given to several factors:

• Value-added energy consumption: The energy needs for direct mating (i.e., value added energy) can vary greatly by primary joining methods. Furthermore, primary joining method energy needs can vary greatly by energy source.
• Non-value added energy consumption: A significant share of direct energy can be in the form of non-value added process energy, which facilitates the direct mating operation. Non-value added processes can take place before, during, and/or after direct mating and are necessary to ensure a successful join. These processes vary by joining method and in some cases, can require more energy than the direct mating process.
• Energy efficiency: The ratio at which energy inputs supplied to the processes are transformed into useful work (i.e., energy efficiency) is not uniform. Energy efficiency can vary greatly depending on energy source and joining technique.

10.4.1 Mechanical Assembly

Mechanical assembly consists of various fastening methods (permanent and non-permanent) to mechanically mate two or more parts and/or subassemblies. These methods can be achieved as follows: 1) inserting and subsequently tightening discrete hardware components, such as fasteners; and 2) designing or reshaping mating parts and/or hardware components to mechanically interfere with the geometry of each other (i.e., interference fit). The latter, in most cases, results in permanent joints, while the former methods allow for permanent or non-permanent assembly.

Many mechanical assembly processes transfer energy in the form of force, torque, and to a lesser extent in the form of heat. In mechanical assembly processes using threaded fasteners, energy is consumed to advance the fastener component between the mating surfaces and to provide relative force rotation (i.e., torque) to secure the assembly. Threaded fastener analysis has estimated that 80% to 90% of torque energy is absorbed by friction in the joint, resulting in as little as 10% of energy transferred into clamping force [13]. Processes involving the use of non-threaded fasteners also consume energy to advance the fastener component between the mating surfaces; however, some non-threaded fasteners require a deformation stage in which additional forces or temperature variations are introduced to permanently secure the joint. In a similar way, interference fits consume energy to advance either a mating part or hardware component; however, such processes may simultaneously do so under temperature variations to enable thermal expansion or contraction of the mating part. Processes that contribute to mechanical assembly are the shape altering processes required to facilitate mechanical assembly. These include the drilling of holes, and heating/cooling energy to support expansion/contraction.

Electricity, compressed air, and hydraulics are commonly used energy sources in many industrial applications that perform such mechanical assemblies [14]. Each of the different energy sources offer advantages and disadvantages for various drive properties (for example, power density, torque to inertia, velocity range, and response speed) [15]. Hydraulic systems have superior drive properties compared to electric and pneumatic. Electric is superior to pneumatic in velocity range and response speed while pneumatic is superior to electric in power density and torque to inertia [15]. In terms of energy, Thiriez and Gutowski [16] reported significant reductions in energy consumption for hydraulic driven systems when compared to electric. They determined that energy consumption in hydraulic driven systems exhibited a decreasing pattern as throughput increased, whereas energy consumption in electric driven systems remained constant. Similarly, Rydberg [17] indicated hydraulic drives operate at higher efficiencies compared to electric drives, especially at lower operating speeds. Bookshar [18] compared the energy consumption necessary to operate an electric and pneumatic power tool for a typical threaded fastener assembly application in an automotive final assembly plant. For this one assembly application, it was determined that electric assembly tools provided a significant energy savings (62%) over pneumatic tools due to inefficiencies in the pneumatic system.

Mechanical joining offers many advantages that include: 1) low equipment cost; 2) no thermal degradation of parts; 3) little to no required surface preparation; and 4) ease of assembly in non-permanent mechanical assemblies. On the other hand, joining in mechanical assembly can be highly energy inefficient depending on the energy source of the joining equipment. Mechanical assembly can also require the use of fasteners, which increases product weight. For transportation applications this can result in lower energy efficiency throughout the product life cycle [19].

10.4.2 Adhesive Bonding

Adhesive bonding is a joining process in which a bonding agent is used to join two or more parts. The bonding agent, also commonly referred to as an adhesive, is generally a polymer substance capable of joining materials through chemical or physical property changes between the joining surfaces. The joining surfaces are referred to as adherents.

There are several types of adhesives that differ in terms of their strength, durability, and processing technique. In general, adhesives can be separated into two distinct groups: adhesives that are derived from materials of natural origin (i.e., natural adhesives), and adhesives that are produced industrially from synthetic polymers (i.e., synthetic adhesives). In modern day assembly, synthetic adhesives dominate the joining processes in adhesive bonding, specifically structural adhesives. This is particularly the case in manufacturing processes because of their high-strength bonding capabilities and resistance to environmental factors. Applications range from high-strength requirements common in load-bearing structures (i.e., structural adhesives) to holding adhesives in non-load carrying applications (i.e., nonstructural adhesives).

Adhesives may take on a number of physical forms, such as liquids, pastes, powders, sticks, or films. Irrespective of initial physical form, the adhesive must be in fluid form at the time of application to enable intimate contact between the adhesive and the adherent. It must then harden (i.e., cure) to a cohesive solid, with the exception of pressure-sensitive adhesives, as these do not harden. During the curing process, the physical properties of the adhesive are altered and it transforms to a solid state to achieve surface attachment. Some adhesives cure through the application of heat, time (through solvent evaporation or absorption), radiation, light, moisture, pressure, catalyst, activators, and/or multicomponent reactions. Table 10.1 presents the advantages and disadvantages of common curing processes.

The reliability and durability of the bonded joint is heavily dependent on the adhesion of the adhesive to the surfaces, the cohesion of the adhesive, and the properties of the bonded materials. Furthermore, a reliable and durable joint requires proper impregnation of the surface by the adhesive, close mating of the surfaces, and maximization of the bonded surface area. Cognard [21] describes the operations to produce a bonded joint as follows:

1. Surface preparation, which allows for the adhesion of the adhesive to the adherents;
2. Preparation of the adhesive;
3. Coating/dispensing of the adhesive to one or both of the adherents;
4. Drying, waiting time, open time;
5. Heat reactivation of the adhesive;
6. Joining of the adherents;
7. Pressing; and
8. Curing, hardening, polymerization of the adhesive to form a solid bond.

Of the process operations in adhesive bonding, the surface preparation stage is widely acknowledged as the most critical stage in the bonding process [22–24]. This is expected since adhesion is a surface phenomenon. Ebnesajjad [25] noted that in surface pretreatment of a metal surface, cleaning using a solvent or other chemical is always required, and treatment to improve corrosion resistance is almost always required. It was also noted that plastics require entirely different surface pretreatment methods than metals. Surface preparation methods used in industrial manufacturing can be classified as follows [26]:

• Mechanical, such as grit blasting, grinding, and brushing;
• Chemical, such as acid degreasing, and phosphatizing;
• Physical, such as flame treatment, and plasma treatment;
• Electrical, such as corona treatment.

Energy consumption in adhesive bonding varies depending on the chosen design considerations, such as surface pretreatment, processing steps, adhesive, and adherent material. The factors influencing energy consumption in adhesive bonding are numerous, and, to illustrate this, consider the different forms of adhesives – liquids, pastes, powders, and films – that have roughly ten different curing modes at various temperatures and times. Furthermore, there are multiple application methods used to apply the adhesive, methods of pressing the adherents to ensure a reliable bond, and methods to prepare the surface prior to the application of the adhesive. Thus, general energy consumption trends in adhesive bonding are difficult to characterize, resulting in energy consumption of adhesive bonding being dependent on the exact combination of bonding parameters. For surface pretreatment methods, Ebnesajjad [25] reported average power consumption for ultrasonic vapor degreasing, plasma treatment, and corona treatment, at an estimated 10W/in², 100W, and 1000W, respectively. Although no power consumption estimates were provided for flame treatment, it requires the use of high temperatures, with flame temperatures reported to exceed 2000°C. Similarly, no power consumption estimates were provided for mechanical preparation methods; however, certain mechanical preparation methods, such as grit blasting, often use compressed air, which is widely documented for its energy inefficiencies [27].

Adhesive bonding offers a number of attractive features including: 1) the ability to produce permanent joints for dissimilar materials; 2) permits joining of fragile and thin parts; 3) distribution of the load over the entire surface area of the joint as opposed to localized spots or seams; 4) lighter weight parts; and 5) relatively low curing temperatures (60°F to 650°F), as compared to welding and brazing, which eliminates significant thermal distortion of parts.

The major limitations of adhesive bonding include: 1) long processing time (e.g., curing and processing steps); 2) limited service temperatures; 3) limited bond strength compared to other permanent joining methods; 4) surface preparation requirements; and 5) varying levels of toxicity, ecological, and fire hazards. Although, to the authors’ knowledge, no such review has been presented on the energy and environmental considerations of surface preparation methods, due to their energy intensive nature, these processes are expected to be significant contributors to the overall energy use of adhesive bonding processes.

10.4.3 Welding, Brazing, and Soldering

Welding is a material joining process in which two or more parts (typically metal) are permanently coalesced at their contacting surfaces by establishing a metallurgical atom-to-atom bond. This bond can be achieved through application of heat and/or pressure. Most welding processes supply energy, in the form of heat, to induce a material state change by melting the contacting surfaces so that the parts and/or subassemblies can be joined (i.e., fusion welding). In a limited number of welding processes, energy is supplied in the form of pressure or a combination of pressure and heat to force the joining surfaces together (i.e., solid-state welding). In solid-state welding, if heat is introduced to the welding process, the contacting surfaces are heated to alter the material state to plastic condition (below the surface material melting point).

Brazing is a metal joining process in which a filler metal is melted and distributed between the joining surfaces of two or more parts. In contrast to welding, no melting occurs in the contacting surfaces of the component; melting only occurs in the filler metal. Energy inputs in brazing are primarily in the form of heat. Energy sources used for brazing include electric coils, fuel gas flames, and gas oil. Soldering, similar to brazing, is a metal joining process in which a filler metal is melted and distributed between the joining surfaces of two or more parts. Soldering and brazing are similar, but the temperatures in brazing far exceed those in soldering.

Energy inputs for welding, brazing, and soldering are generally supplied in the form of heat. Power is the rate at which energy is delivered per unit of time from the heat source to the part, and is expressed in Watts. Hence, power transferred to the part per unit surface area is defined as the power density, and is expressed in Watts/millimeter². Each type of heat source has the capability of supplying heat at different power densities (W/mm²), as well as at different temperatures. Power density and temperature can be used as a valid energy comparison among welding, brazing, and soldering processes, with power density being the most universal of the two methods. Although there is an approximate linear relationship between temperature and energy input, temperature as an energy indicator is limited to select processes [28]. Figure 10.3 shows the power densities of several fusion welding processes. At high energy densities, nearly all of the heat produced is transferred to the component; little to no heat is wasted [29]. Efficiencies for high energy density processes are rated up to 100% efficient [28, 30], whereas arc welding processes are rated up to 85% efficiency [28, 31]. Briskham et al. [32] investigated the energy use of two welding processes (resistance spot welding, friction stir spot welding) and one mechanical assembly process (self-pierce riveting). For resistance spot welding, friction stir spot welding, and self-pierce riveting, energy use (per thousand joints) was 20kWh, 2kWh, and 2.2kWh, respectively.

Welding, brazing, and soldering consume energy in four primary ways: 1) supplying heat and/or pressure for surface joining, 2) shielding from atmospheric effects, 3) removing surface contaminants, and 4) post-processing the joined surface. The heat energy generated (and subsequent heat losses) must support each of these direct and indirect processes to permit successful joint formation. The first two steps generally take place in all welding operations, whereas all steps are common for brazing and soldering. While certain welding applications require indirect processes, such as thermal and mechanical treatments to remove surface contaminants, such processes are not necessary in all welding applications [33].

Table 10.2 summarizes energy influencing advantages and disadvantages of the primary joining methods in assembly [19]. An advantage of the mechanical joining method is the relatively low primary energy required to join components. However, depending on the energy source, these processes can be very inefficient and have comparable energy use to high energy processes [34]. Other disadvantages of the mechanical joining methods are that it can require additional hardware components, drilling of holes to facilitate joining, and increase in the overall product weight. These factors translate to an increase in material use, scrap, and fuel consumption (in the case of automobiles, aircraft, and other modes of transportation). Adhesive bonding offers advantages in the low energy inputs required to join components. It allows for the bonding of dissimilar and lightweight materials. Furthermore, when compared to mechanical bonding, adhesive bonded products enable lower overall weights due to the lack of additional hardware components [19]. It is believed that the chief disadvantages, in terms of energy use within adhesive bonding, arise in the indirect processes (i.e., surface preparation, heating, ventilation, etc.) required to facilitate the bonding of components. Of all the joining methods, welding, brazing, and soldering require the largest amounts of energy to facilitate joining. In terms of primary joining energy, welding is the most energy intensive.

Joining processes in assembly can be characterized by a number of multistep processes, energy sources, material compositions, and process configurations. In the context of assembly, these factors are all interdependent and can significantly influence energy use. Thus, it is critical that joining methods be considered from design to fabrication to ensure minimal energy is consumed throughout assembly.

10.6.1 Case Study Energy Consumption Analysis Approach

In order to properly evaluate energy use of the assembly process, each energy input was considered and each process was categorized to gain insight into the full energy consumption picture. The approach taken in this case study was to consider both the energy consumption at the individual process level (direct value added and direct non-value added) as well as the facility level (indirect) to account for energy consumption for assembly processes and for maintaining the work environment. This approach differs from that described in Section 10.5 in that it also includes the energy consumption at the indirect, facility level. Once each process was categorized, the energy source was determined to properly estimate its energy consumption. The energy inputs considered in this case study are battery, electric, pneumatic, and hydraulic.

Energy auditing is a widely used method for estimating energy consumption in commercial, residential, and industrial facilities. As defined by the Standard EN 16247-1 [36], energy auditing is “a systematic procedure to obtain an adequate knowledge of the profiles of energy consumption of an existing building or group of buildings, an industrial and service private or public, in order to identify and quantify in terms of cost effectiveness of energy saving opportunities and the relationship of what is revealed.” In industrial assembly facilities, primary energy sources are in the form of electricity and fuels. These sources are then either used directly or converted into secondary energy sources, such as pneumatic, hydraulic, or battery powered energy. The energy audit of the assembly operation in question serves to identify all energy streams in the assembly process. Therefore, the assembly system was first analyzed to determine all of the energy consuming processes associated with the assembly system. Second, each energy consuming process is itemized. Third, energy consuming processes are classified by each process, equipment, and/or systems by energy source. Next each process, equipment, and/or system, is categorized according to the process data requirements shown in Table 10.3. Although the focus of this case study was not on indirect energy, it should be noted that as much as 73% of the energy consumption in industrial facilities is consumed in lighting, heating, ventilation, and air conditioning (HVAC) [37].

Following identification and classification of the processes, equipment, and/or systems by energy source, assembly energy consumption can be calculated using the procedure outlined in Example 10.6(a). Each assembly process, equipment and/or system is quantified in the facility. During this time, we also record equipment specifications. Next, the operation time is determined using usage logs, meters, or rough estimates. The data gathered in Steps 1 – 3, are used as inputs for the energy consumption equations (Eq. 10.10–10.13). Estimation of assembly energy consumption is presented in Kilowatt-Hours.

10.6.2 Assembly Process Categorization

In the case study, assembly processes, similar to Section 10.3, are assigned to one of two categories: direct and indirect processes. Table 10.4 organizes the case study processes by types and lists the common energy sources for each process along with a list of variables of interest, which are necessary to estimate the annual energy consumption in Kilowatt-Hours (KWh).

Using Table 10.4, the assembly processes within the station of study on the assembly line can be categorized in order to more easily calculate the annual energy consumption. The number of pieces of equipment totals 59, which includes direct and indirect related processes, while the direct value added and direct non-value added processes account for 38 of those. The processing equipment used within the area of study can be seen in Table 10.5, where it has been separated into direct energy (value added/non-value added) and indirect process equipment by source type. The equipment used in the direct value added processes includes torque guns, which are used for different assembly operations. Direct non-value added processing equipment consists of positioning and delivery operations such as hoists used for lift assist, chain drive advancing the product through the assembly line, and the material delivery by fork trucks and tow tractors.

The value added direct processes include torque tools that use many different energy sources like electric, battery, pneumatic, and hydraulic. The pneumatic tools are the most common in this station on the assembly line and can include items like an Uryu ULT100, which uses compressed air as a power source. Battery powered torque tools are the next most common energy source and include tools such as a Milwaukee M18 FUEL™ 3/8” Impact Wrench and a DeWalt 12-Volt Max Li-Ion Cordless 3/8” Impact Wrench. The electric torque tools used on the assembly line consist of items like an Atlas Copco ETD ST101-750-25 or an Atlas Copco ETX72-450CT that are powered directly by the electrical system. Hydraulic tooling used on the assembly line consists of items like an Alcoa Huck PowerRig 918-5, which uses an electric hydraulic pump to power the tools.

The non-value added direct processing equipment consists of tools for positioning and material delivery like hoists or fork trucks. Tools used to move and position the components and product consists of items like Harrington NER003S hoist and a Hyster E50Z 48V forklift. The hoists used on the assembly line are all electric powered. All of the forklift and tow tractors are battery powered. Lastly, the chain drive advancing the product along the assembly line uses an electric motor. Indirect processing equipment that maintains the assembly environment includes lights for an acceptable visible working environment and comfort fans to keep suitable temperature for the assembly operators. Each one of these items is also powered by the facility electrical supply.

10.6.3 Case Study Energy Analysis Results

Having achieved process categorization and energy source identification, it is possible to estimate the annual energy consumption. Using the variables of interest from Table 10.5, the annual energy consumption of each piece of equipment is estimated. Table 10.A.1 in Appendix 10.A summarizes the list of equations used to estimate the annual energy consumption. This section identifies several example calculations using the equations from Table 10.A.1 to estimate the annual energy consumption for both direct and indirect process equipment. Each item is estimated based on annual energy consumption in KWh in order to maintain the ability to compare each process consistently.

Value added direct energy assembly process equipment includes items with energy sources like battery powered, pneumatic, electric, and hydraulic. The annual energy consumption for the battery powered tools was estimated by identifying first the working voltage of each tool and the battery capacity it uses in Amp-Hours (Ah). Multiplying these two values yields an estimate of the energy in Watt-Hours for each charge of the battery. Then, by identifying the number of charges required per day and estimating the number of production days annually, the estimated annual energy consumption for each tool is calculated. An example calculation can be seen in Example 10.6(b) and Table 10.6.

Annual energy consumption of pneumatic powered tools must be estimated differently from battery powered tools but follows the same principle of estimating daily KWh consumption and multiplying that across the number of production days annually. Each pneumatic tool has a cubic feet per min (CFM) rating, which is used to estimate energy consumption. It is assumed that every 4 CFM a pneumatic tool consumes equates to 1 horsepower (HP) rating. Once the HP rating is calculated for each tool, it is converted to Kilowatts using the relationship 1HP = 0.746 KW. To estimate the daily KWh consumption of the pneumatic tool, the KW rating and estimated daily processing time the tool are multiplied. A sample calculation can be seen in Example 10.6(c) and Table 10.7 below.

The annual energy consumption for the remaining electric and hydraulic direct processing equipment was calculated using the same method; taking the HP or KW rating of a piece of equipment, estimating the annual hours of use and multiplying them to get the annual KWh consumed. The hydraulic tools use an electric pump that pushes the hydraulic fluid to the tool so the energy consumed by the tool equals that of the electric motor within the hydraulic unit.

Direct non-value added processing equipment annual energy consumption was calculated using the same method as the electric and battery powered direct process tools. The daily energy consumption was calculated by using either the HP or KW rating of the electric motor or the battery capacity and then multiplying over the number of production days annually. The positioning equipment, hoists, and chain drive are electric powered and the material delivery equipment, fork trucks, and tow tractors are battery powered.

The total annual energy consumption in KWh for the case study is shown in Example 10.6(d) and Table 10.8. The majority of energy consumed in the station is by the material delivery processes (fork trucks) and the facility processes, like lighting. Combining Table 10.4 to categorize processes and the equations for energy estimations in Table 10.A.1 allowed for the calculation of annual energy consumption of assembly processes. Table 10.A.1 also has additional considerations for each of the energy sources not included in this analysis. These considerations can impact the total energy use and energy efficiency of the case study assembly system and should be included in assembly energy analyses if able.

Comparison of the direct and indirect energy consumption in the assembly case study can be seen in Figure 10.4. The indirect energy consumption accounts for 42% of the total energy consumed while the process related energy of the direct value added and non-value added account for 58%. The value added processes accounts for only 5% of the overall energy consumption. In total, 95% of the energy consumption is used for either indirect processes that maintain the assembly environment or for direct non-value added processes that support direct value added assembly processes.

The composition of the direct non-value added energy consumption can be seen in Figure 10.5. The vast majority of the energy consumption for direct non-value added processes is from material handling processes. The energy consumed by the material delivery processes accounts for 94% of the total direct non-value added energy consumption while the energy consumption of the positioning equipment is negligible. Similarly, the battery powered direct non-value added processes accounts for 94% of the energy consumption. The composition of the direct non-value added energy consumption by energy source is shown in Figure 10.6.

Comparison of the direct value added processes by energy source type can be seen in Figure 10.7. The energy expended on the direct value added processes is dominated by two energy sources, pneumatic and electric. Processes that are pneumatically powered account for 53% of the total direct value added energy consumption while the electric powered direct value added processes account for 40% of the total direct value added energy consumption. The remaining 7% of the energy consumed is by the hydraulic and battery sources, 5% and 2% respectively.

Pneumatic and electric powered tools account for 93% of the total direct process energy consumption mainly because of the amount of tools for each source and the application for heavier assembly. A useful way to compare the different types of tools by energy source type is to look at the power rating for each tool rather than the total amount of energy consumption. This is because of differences in processing times for the tools that may alter overall energy consumption. The power rating, HP or KW, is a sufficient way to compare the energy intensity rather than the gross amount of energy consumed by a tool. Table 10.9 shows the average KW rating for each source type for all of the pieces of equipment in the scope of the case study. Hydraulic powered equipment has the largest average KW rating for an energy source with 7.46 KW while battery powered tools had the smallest with 1.48 KW.

The top five energy intensive assembly processes are listed in Figure 10.8. These processes include both direct value added and direct non-value added processes and rank each process grouping by energy intensity. The top two energy intensive processes are major assembly, which is defined as assembly of large components, and feeding, such as the chain drive. The next three energy intensive processes include another major assembly process, a material delivery process, and a minor assembly process which is defined as an assembly of a small component. Details of the assembly processes in Figure 10.8 cannot be disclosed by the manufacturer.

10.6.4 Discussion and Recommendations

Many aspects must be considered when evaluating assembly energy consumption within the manufacturing enterprise. Categorizing processes before calculating energy provides a comprehensive view and a viable framework to determine of energy use and costs. Identifying the major contributors to energy consumption within assembly processes allows for easy identification of assembly activity cost improvement opportunities. As the cost of energy increases, it becomes more important to identify opportunities to reduce assembly process impact on costs and energy consumption. The reduction of energy consumption can increase profitability and competitiveness for an organization. The process categorization and energy calculations described through this case study illustrate one approach for evaluating the energy consumption of assembly processes and improving the performance of an organization. Development of unique frameworks or modifications to the presented frameworks here in this chapter may be required for other assembly systems.

Case study recommendations:

• Evaluate total amount of energy consumed by source type, then identify the most energy intensive tools/processes. The battery powered tools offered the lowest energy intensity for tool energy source type; thus, results suggest converting pneumatically powered tools to battery power. This recommendation also takes into account the potential for air leaks in the pneumatic system, which is not accounted for in the energy intensity rating of the tools.
• Evaluate direct value added/non-value added vs. indirect energy then direct value added vs. non-value added energy to identify the largest energy consumers. The indirect energy consumption accounts for a large percentage and provides a good opportunity for energy reduction; however, once indirect energy is addressed, improves to direct, value-added operations will be required.