➲ HVAC & R Skills Worskhop
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Heat losses
Production Line 1
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for instance, using operations manuals for major equipment, directly observing equipment operation, estimating energy use from process conditions and valve positions, or through engineering calculations. |
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Review the goal and information required
When prioritising areas of gas use, involve site personnel that use or are affected by this equipment, process, building or area. They may be a valuable source of information when selecting and designing the most suitable metering system, and they may suggest additional benefits that improve other aspects of site operations.
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Gas input |
Steam boiler |
Production Line 2
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Step 2
Gas Steam Heat losses
Prioritise what to measure
Build an energy balance
Taking into account your primary goal, determine where your money would be best spent on gas measurement and monitoring.
Begin by building a preliminary energy balance based on what you already know. Use the results of your investigations into how much gas goes into the site( from gas bill information and identification of main areas of gas usage). Calculate or estimate how much gas is consumed by each area, process or major piece of equipment. Using this method, you should be able to quantify at least 80 % of the total energy consumption to a suitable level of accuracy.
See the example at the end of this section for a sample high-level energy balance that will help you set priorities for metering.
Industrial site
Other uses
Figure 8: Sankey diagram identifying all gas users on an industrial site.
at high pressures, a clamp-on ultrasonic flowmeter can be installed on the pipe.
Table 1 presents some common methods for estimating gas use when no meter is available.
Select equipment to measure and monitor
No organisation has an unlimited budget, so it is important to prioritise the equipment you want to measure and monitor. Determine priorities by comparing the amount of gas usage to the potential for that end-use equipment process to generate savings( which may be energy or production- related costs). Even with an incomplete energy balance, you can estimate the main equipment and areas of gas use by,
Computer from which an operator can access the information
Data acquisition server receives data from sensors and meters and sends commands to field equipment
Questions for site personnel:
• Do you have a recurring issue that could be solved with additional meters?
• If you had better information on energy use in your area of responsibility, how would you use it?
• With additional metering, you will know how much energy is used in your area. How could you use energy performance indicators( e. g. GJ per tonne of product, or GJ per m3) to improve what you are doing?
Step 3
Investigate and select energy management software and a long-term data storage solution
Ideally any new meter should be integrated into a SCADA system or BMS. A robust data collection and management system is essential for maximising the value of your meter and should form part of your gas measurement and monitoring plan. Such systems cover a wide range of hardware systems and software services with one example shown in Figure 9.
Computer or data centre
stores data for long-term record
If feasible, first build a coherent, reasonably accurate energy balance without the use of permanent metering. Rather than installing new meters, focus on analysis and monitoring of existing data.
If the existing data sets are not sufficient, state clearly what information is missing, then investigate how you can collect this information. Is a meter required or can you find out by another means( e. g. you may be able to establish a connection to the gas utility meter, or use hourly data from your gas retailer for the investigation)? Is a permanent meter needed that might require the plant to shut, or would a temporary meter suffice at this stage?
Temporary meters and data loggers can be a cheaper way to collect data and prioritise capital expenditure before installing a permanent meter. They also have another advantage: they don’ t disrupt production. For temperature, small data loggers can be installed easily along pipework or in tight spaces. For flow of liquids and gases
The SCADA sytem reads the measured flow and level, and sends the setpoints to the PLCs
PLC1 compares the measured flow to the setpoint, controls the pump speed as required to match flow to setpoint.
PLC2 compares the measured level to the setpoint, controls the flow through the valve to match level to setpoint.
Communication and control system includes all the equipment between the sensors, meters or equipment and the data acquisition server. It can include cables, modems, PLC, RTU …
Field equipment includes sensors, meters which create information and other devices which receive commands from controllers
Figure 9: Example of a process SCADA system.
16 | HVAC & R Nation | www. hvacrnation. com. au | August 2016