Compressed Air Swg Technical Guide

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ENERGY AGREEMENTS PROGRAMME 2007 COMPRESSED AIR TECHNICAL GUIDE Sustainable Energy Ireland Compressed Air Technical Guide HANDY RULES OF THUMB 80-93% of the electrical energy consumed by a compressor is converted into heat. The installation of a heat recovery unit can reclaim anywhere from 5090% of the available thermal energy Every 1 bar in pressure reduction produces a 6-7% power saving Improving the efficiency of a compressed air system should begin with a strategic assessment of the core energy services and work its way back to the generation station One 4mm hole in a compressed air distribution pipe operating throughout the year can cost €2,005 P.A. on a typical compressed air system operating at 8 bar (electricity at an average unit cost of €0.10/kWh) A 1% reduction in compressor power consumption can be achieved through a 4oC reduction in inlet temperature Air velocity in the distribution main should not exceed 6 m/s Air velocity in distribution branch lines should not exceed 15 m/s A 50% increase above the maximum recommended air velocities increases system energy use by approximately 2% For areas with different production times, the use of zone isolation valves should be considered If a top-up compressor is being called 30-70% of the time, the economic case for the installation of a VSD machine should be investigated Page 2 of 40 Sustainable Energy Ireland Compressed Air Technical Guide TABLE OF CONTENTS HANDY RULES OF THUMB ............................................................................................................. 2 COMPRESSED AIR SYSTEM AUDIT – A STRATEGIC WALKTHROUGH....................................... 4 1.1 BENCHMARKING .................................................................................................................... 5 1.2 PROCESS MAP....................................................................................................................... 6 1.3 METERING/MONITORING AND TARGETING ................................................................................. 7 1.4 ENERGY REQUIREMENTS.......................................................................................................... 7 1.4.1 Avoid Misuse ................................................................................................................ 7 1.4.2 Turn the Equipment Off ............................................................................................... 8 1.4.3 Pressure Considerations............................................................................................... 8 1.4.4 Education/Training....................................................................................................... 9 1.5 DISTRIBUTION ....................................................................................................................... 9 1.5.1 Line Improvements and Pressure Drops ..................................................................... 9 1.5.2 Leak Detection Programme ....................................................................................... 10 1.5.3 Dedicated Air Receivers for End Users....................................................................... 12 1.6 TREATMENT ........................................................................................................................ 13 1.6.1 Treatment Equipment................................................................................................ 13 1.6.2 Localised Air Treatment ............................................................................................. 16 1.7 COMPRESSED AIR GENERATION.............................................................................................. 17 1.7.1 Compressor Sizing...................................................................................................... 17 1.7.2 Discharge System Pressure ........................................................................................ 17 1.7.3 Control ........................................................................................................................ 18 1.7.4 VSD Compressors ....................................................................................................... 21 1.7.5 Reduce Air Temperature (ambient air) ...................................................................... 21 1.8 PREVENTIVE MAINTENANCE ................................................................................................... 22 1.9 PURCHASING POLICY ............................................................................................................ 24 1.9.1 Compressors ............................................................................................................... 24 1.9.2 Treatment and End Users........................................................................................... 29 1.9.3 Seek Advice................................................................................................................. 29 1.10 HEAT RECOVERY .................................................................................................................. 30 1.11 COMPRESSED AIR AUDIT OVERVIEW ....................................................................................... 31 Resources……………………………………………………………………………………32 Page 3 of 40 Sustainable Energy Ireland Compressed Air Technical Guide COMPRESSED AIR SYSTEM AUDIT – A STRATEGIC WALKTHROUGH The goal of energy best practice is to aid a facility improve their market competitiveness by reducing energy costs from the bottom line of the budget. It does this by merging the most appropriate and efficient technology with suitable management strategies. This aids a facility improve its overall energy efficiency, environmental performance, system reliability and in many cases: productivity. Best practice emphasises assessing the entire system, rather than individual components. It adopts this holistic view of systems to identify potential energy saving opportunities and improvements. Upgrading a compressed air system through the procurement of the most efficient compressor technology can be productive but not nearly as valuable as a full system assessment. By establishing a holistic approach to managing the compressed air at a facility, savings in the region of 20-50% can often be found. As was evident during the course of the six audits at industrial facilities, some of the largest potential savings were identified by assessing the end user requirements and using this as the platform to optimise system performance. A compressed air system audit begins by assessing the service requirements and moves through the distribution network and onwards to the generation station. These deliberate and strategic actions are often described as steps in the onion diagram (Figure 1) which emphasises a full assessment of the core energy services as the first action taken when aiming to increase the efficiency of a system and move onwards through the system back to the generation station itself. Accordingly, the layout of this document is quite deliberate – it begins by discussing the typically efficiency opportunities seen at end users in industrial facilities and moves upstream through the system to the compressed air generation station itself. Figure 1 – Onion Diagram Principle in relation to a strategic assessment of a compressed air system audit Page 4 of 40 Sustainable Energy Ireland Compressed Air Technical Guide Size of Prize It is important to evaluate how much of site total energy usage is attributable to Compressed Air. If detailed metering not available this can be estimated using simple spreadsheet analysis, looking at installed capacity (kW), run hours and estimated running load. This determines whether the site should be looking at delivering savings through Capital investment (High Cost), Repair Replace Maintain Initiatives (Medium cost), or Operational Change (Low/No Cost). 1.1 Benchmarking The term benchmarking describes the process of measuring or estimating system power consumption – in the case of a compressed air system, it refers to overall power consumption. Before undertaking any kind of compressed air system energy efficiency improvements, a benchmarking exercise must be carried out. Without this benchmark or baseline of energy use, it is impossible to quantify ongoing system improvements. Field measurements rather than estimations are the most accurate means of establishing a benchmark. 1In existing installations, some simple measurements will serve. The most important measurements are power consumption and flow measurements. The next step is to determine if there are any correlations between power and key usage or process profiles. For example: production levels; seasons; daily profiles; shift patterns; etc. This step is vital in selecting the data to be employed for generating Energy Performance Indicators (EPI) and often incorporates some form of regression analysis. EPI’s facilitate optimising the supply and demand side of the compressed air system. The most popular EPI for a compressed air system benchmark is the ratio of energy consumed per normal meter cubed of compressed air (kWh/Nm3)2. Moving on from overall power consumption, in order to determine the overall performance of the compressors and the distribution network, it is necessary to gain an understanding of the pressure at strategic points throughout the system. Pressure readings should be taken at: • Compressor discharge points • Before and after filters • Before and after dryers • At the main distribution header • At critical users 1 It is a relatively simple exercise to incorporate field measurement into a system at the design stage however ad hoc measurement instrumentation can be costly in existing installations. 2 It should be noted that a comparison of your system’s performance against other systems (or even systems at your own plant) can be done, however it is a difficult exercise in data normalisation and serves little benefit. The difficulty stems from the myriad of system requirements characteristics across dissimilar (or similar) sites. For example, differing climatic conditions, pressure requirements, end user requirements, control, volume requirements, and filtering and drying requirements, leads to comparison of performance across systems cumbersome, and often renders the results meaningless. Page 5 of 40 Sustainable Energy Ireland Compressed Air Technical Guide The simultaneous readings taken at critical users aid the identification of potential opportunities for improvement. The ultimate goal of this exercise is become familiar with the dynamic pressure performance of the distribution system and to fill in a system process map (discussed in the next section). 1.2 Process Map A process flow diagram outlining the critical components of the compressed air system should be generated as part of any system audit. Such components should include: • • • • • • • • • Intake Filtering Components Compression Equipment Instrumentation and Control Cooling (either internal or external) Air Storage Equipment Drying and Filtering Equipment Distribution Layout (include various isolation valves, fluid traps, intermediate storage vessels and other equipment which have inherent pressure differentials) Points of Use (either by name or group) Metering Undertaking this exercise is vital in developing an understanding of the system. This map can be as detailed as the operator would like but a simple block diagram will suffice. In addition, this map should be thought of as a live document and it should be updated as more information is gathered (i.e. pressure readings throughout the distribution network, isolation valves (manual/automatic), etc.) and updated when any alterations are made to the system. Figure 2 – Typically High Level Process Map of a Compressed Air System Page 6 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.3 Metering/Monitoring and Targeting Where possible, metering should be a part of any new production or utilities expansion or machinery purchase - it is much cheaper to install it at the start that retrofit later. Improvements to metering, monitoring and targeting and KPI management will typically generate between 5-10% savings - a “size of the prize” evaluation will determine where is most appropriate to implement metering. The following equation can be used to justify metering expenditure: C = Apt 100 Where: C = Justifiable Metering Expenditure (€) P = Percentage Savings Expected A = Annual Energy Cost (€) T = Acceptable Payback (years) 1.4 Energy Requirements Compressed air is not an efficient means of transferring energy around a facility. The usable work delivered from an air-operated device is generally 8 times more expensive than an electrical equivalent. Accordingly, there is often significant scope to increase plant efficiency by reviewing end user requirements. 1.4.1 Avoid Misuse Minimising compressed air demand can be the most effective means of mitigating the power consumption of the compressed air system. The energy requirements served by the compressed air can often be better served through some form of local operation. Table 1 illustrates a snapshot of several energy requirements which could be better served by alternative means, and for a small fraction of the lifecycle costs. Energy Requirement Compressed Air Use Alternative Use Cool Electrical Cabinets Air Vortex Tubes Air Conditioning; Fans Hoists Area Cleaning/Debris Removal Pneumatic Hoists Transportation Compressed Air Blasts Creating a Vacuum Compressed Air Venturi Electrical Hoists Low Pressure Air; Brushes; Blowers; Vacuum Systems Conveyor; Blowers; Electric Actuators or Hydraulics Vacuum Systems; Vacuum Pumps; Multi Stage Venturis. Motors or Actuators Pneumatic Control Electric Devices3 Drying Compressed Air Blowers; Fans; Air Conditioning; etc. Cool; Aspiration; Mix; Agitate; Inflate; etc. Compressed Air Nozzle Arrangements Blowers Air Whips Table 1 – Sample Compressed Air Uses, with more Efficient Counterpart Technology 3 Ensure the retrofitted device is appropriate. Electric devices can often have less precise torque control and shorter operating lives than their pneumatic counterparts. Once again, it is a matter of selecting the appropriate technology to suit the end user requirement. Page 7 of 40 Sustainable Energy Ireland Compressed Air Technical Guide In order to determine if a pneumatic device is the correct choice, some key questions should be asked. As a result of using compressed air, are there: • • • Intrinsic safety enhancements? Significant productivity gains? Labour reductions? If the answer to all three are “no”, then alternate means of servicing the energy requirement should be explored. 1.4.2 Turn the Equipment Off If compressed air is not required for long periods, isolation valves (manual or automatic) should be installed on the line to minimise energy waste. In addition, manual valves should be installed to isolate header lines no longer in use. Pneumatic equipment which could be potentially left on for sustained periods when not required should also have some means of isolating the line. Standard operating procedures should be effective to ensure that compressed air flow to these energy requirements is isolated during non-operational periods. This is also an effective means of avoiding parasitic loads which are often present in distribution branches. 1.4.3 Pressure Considerations It is a common finding across audits to identify a situation where an end user is utilising unregulated compressed air. A pressure regulator is a device utilised to limit the maximum end of line pressure and is generally placed in the distribution system immediately upstream of end users. Without this device, the energy users utilise the maximum system pressure resulting in increased wear and tear; higher maintenance costs; and a shorter operational lifetime. In addition, local pressure reduction reduces artificial demand (leakage and other parasitic loads). If a situation occurs where one specific end user is dictating the pressure of the entire system, it is often more economic to replace or modify this component rather than increase the system pressure. For example, the bore of a solenoid stem could be increased, or the gear ratios can be changed, or similar mechanical advantages could be exploited before taking the easier, but more financially costly, route of increasing compressor discharge pressure at the generation station. Other possible solutions include boosters immediately upstream of the end users or a dedicated high pressures system. Pressure Reduction Savings Take for example a 150kW compressor running for 8400 hours P.A. Assume the efficiency of the compressor is 90% and the cost of electricity is 0.10 €/kWh. If the discharge pressure were reduced from 7.5 bar to 6.5 bar, a saving of over 6% in power consumption could be expected which translates into an annual monetary saving of €8,400. This substantial saving does not include the fringe savings which could be expected (reduced leaks, reduced component maintenance, etc.). Appropriate controls can often overcome such adverse conditions (Section 1.7.3), however in undertaking this opportunity, the discharge pressure should be stepped down in small increments and the performance of critical end users should be carefully monitored. Page 8 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.4.4 Education/Training Plant personnel often do not realise the relative cost of compressed air. However, operators and staff can be a valuable resource when adequately informed and respond well to energy programmes. As a result, it is vital that they receive the relevant training related to the efficient use of pneumatic plant machinery. 1.5 Distribution Tests and experiments have shown that for every 1 bar in pressure drop across the system, the resulting power consumption is increased by 6-7%4 (plus the additional cost of unregulated users). Accordingly, the distribution network can have a profound influence on the performance of the system. There are a number of steps, which can be taken to optimise the air distribution system. 1.5.1 Line Improvements and Pressure Drops The system process flow map outlined in section 1.2 can help identify areas of excessive pressure drops (e.g. plugged filters; undersized hoses, regulator and lubricators, tubes, filters; moisture separators; after coolers; restricted supply lines; poorly designed distribution networks; etc). For angle connections, it is best to replace tee connections with directional angle entry connections or swept tees. The turbulence caused by a 90o connection can cause pressure drops resulting in backpressure sending a false ‘unload signal’ to the compressors, which can potentially cause excessive compressor cycling. Incorrect pipe sizing or restrictions are a major source of pressure loss in the system. For example, the interconnecting distribution network from the compressor supply to the header distribution piping should create no pressure loss. However, such losses are commonplace, especially in more antiquated networks where numerous changes have occurred. Interconnecting pipes between compressors or systems often require close attention. It is vital that they are carefully designed to ensure that they are not sending back any false signals to the compressor. However, such piping strategies can be beneficial where top-up air can be provided from one system rather than operating a backup compressor. A rings main is generally the most efficient type of distribution layout. The local feeding mains can flow up to 15m/s. However, in order to prevent adverse pressure drops, the flow velocity in the main header sections should not exceed 6m/s. As a rule of thumb, a well-designed and maintained system should not have pressure drops of greater than 0.2 bar between the end of the treatment centre and the farthest point in the system. 4 Carbon Trust GPG385 – Energy Efficient Compressed Air Systems Page 9 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.5.2 Leak Detection Programme Leaks are an unfortunate but regular feature in compressed air distribution networks. Typically, the energy requirements served by a compressed air system are intermittent in nature; however leaks are constant and potentially significant. The monetary cost of leaks can be quite startling, and surprising. Compressed Air Leaks One 4mm hole in a compressed air distribution pipe can cost €2,005 P.A. on a typical compressed air system operating throughout the year and at 8 bar (Figure 3). In addition to the monetary costs, leaks can cause significant pressure drops resulting in excessive compressor cycling. Attempts are often made to combat pressure loss in a system where excessive leakage is a problem by increasing system discharge pressure. However, this only exacerbates the problem by increasing the leakage rate and creating more leaks in the future. Figure 3 – Proportionate Costs of Leaks in a Compressed Air System for Range of Pressures Leakage levels at facilities are typically as high as 20-30% and levels as high as 50% are not unusual. In order to move forward with any leak reduction programme, it is important to benchmark the current leakage rate. The extent to which a compressed air system is leaking can be easily determined during non-production hours through assessment of Monitoring & Targeting (M&T) data (if present) or through manual pressure indicator readings in the distribution network with some quick calculations. Page 10 of 40 Sustainable Energy Ireland Compressed Air Technical Guide Determining Current Leakage Rate In the absence of a compressed air M&T system capable of delivering snapshots of compressed air flow during non-production times, facilities can use the Start/Stop Method. 1. Turn off all end users 2. Start the compressors and measure the time interval for the compressor to load and unload (the compressor will load and unload due the existing leaks in the system) 3. Repeat a number of times to determine the average Leakage (%) = [(Tx100)/(T+t)] T = Time On Load (mins), t = Time Off Load (mins) The leakage percentage will be below 10% in a well-maintained system, while losses as high as 20-30% will occur on poorly maintained systems. Locate the Leaks Leakage can occur at any point in a compressed air system, but the most common culprits include piping joints, drains, relief valves, drain valves, flexible hose pipes, filter and lubricator units, pressure regulators, condensate traps and thread sealants. The best means of locating compressed air leaks is an ultrasonic acoustic detector capable of identifying the high frequency noise synonymous with compressed air leaks. When this technology is not available, simpler methods such as applying soapy water to the distribution network and waiting for bubbles to form is just as effective. Repair the Leaks Fixing the leaks is often as simple as tightening connections or applying sealant at strategic points. However leaks will be found that require the replacement of faulty components. In all instances, select the highest quality fittings, disconnects, hoses, tubes, etc. and install them as appropriate with high quality thread sealant. A 10% reduction in leakage, which is a modest target for leakage in any system, would often be gained as a result of carrying out an intensive leak reduction programme. Leak Reduction Programme Due to the large savings associated with a regular Leak Detection Programme, the potential savings associated with this opportunity to save energy often results in payback periods of less than 1 year. A leak reduction program will involve identification (tagging), tracking, repairing, recording and verification. Page 11 of 40 Sustainable Energy Ireland Compressed Air Technical Guide The most valuable tool in combating leakage in the system are personnel who should be brought onboard and actively engaged in the programme. Plant personnel will often become actively engaged in a leak reduction programme. Knowing that a reduction in leaks will lead to a more comfortable working environment will often result in more active involvement from personnel. The goal of any programme is to make individual departments responsible for usage. Accordingly, flow to these departments should be monitored to ensure that area ownership is taken. Facilities utilising significant volumes of compressed air should aggressively engage in a Leak Detection Programme and carry out a bi-annual compressed air leakage survey. Finally, it is important to bear in mind that one of the most effective means of reducing compressed air leakage is to reduce the distribution pressure. Network Installation Selection Where possible, the distribution pipework network should be welded. This is especially important where access to main headers is difficult or compressed air is required on a 24x7 basis making any leak reduction programme almost impossible. The potential economic losses as a result of operating a distribution in poor condition outweigh the capital cost associated with installing high quality connections. 1.5.3 Dedicated Air Receivers for End Users Air receivers are beneficial in industrial applications where air pressure is subject to large fluctuations or variations. In these situations, the increased compressed air requirement is compensated by air from the local air receivers thus minimising idling at the generation station. The air receivers are subsequently replenished slowly using a flow/control valve to minimise peak energy demand on the compressor station. In addition to reduced compressor cycling, air receivers provide protection for end users that require high pressure by minimising the system pressure drop off while supporting the speed of transmission response in supply. Page 12 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.6 Treatment Compressed air system performance is typically enhanced through appropriate treatment. Air treatment equipment is required to adequately prepare the air to meet the energy requirements of end users. However, it is vital to marry the treatment facilities with the actual end user requirements. Inappropriate treatment for the compressed air system can be a major source of energy waste. 1.6.1 Treatment Equipment Moisture and contaminants carried over from the compressed air generation facility can cause damage to sensitive end users that require high quality air. In order to maintain the integrity and safety of the system, compressed air must be kept moisture-free and particulate-free. Accordingly, humid compressed air must be dried appropriately to extract the moisture from the stream and prevent precipitation. The technology employed to treat (filter and dry) compressed air has a significant energy consumption implication (Table 2). Decisions based solely on capital economics often leads to selection of the most inefficient technology rather than more energy efficient equivalents. Dryer Type Deliquescent Refrigeration Membrane Waste Heat Regenerative Desiccant Heatless Desiccant Heated or External Blower Desiccant Heatless Pressure Dew-point +10oC +3 oC -20 oC -20 oC -40 oC -40 oC -70 oC Filtration Requirements General Purpose None Before & After Before & After Before & After Before & After Before & After Added Energy Cost 1% 3-5% 28% 3-5% 10-18% 8-12% 15-21% Table 2 – Typical Additional Costs for Drying Compressed air treatment typically requires filtering and drying equipment – invariably housed in the compressed air generation station, however situations do occur where it makes more economic sense to only treat a portion of the air. The general rule of thumb is that the higher the quality of air, the greater the compressed air system costs (initial capital and system running costs). Selecting the appropriate drying technology for your requirements can achieve significant savings over the compressor lifecycle (Table 2). Much work has been carried out to bring classification to major contaminants. Table 3 and Table 4 illustrate the classes and typical requirements set out in ISO 8573.1 (Air Quality Classifications Standard). To choose the required class, assess the required dew point, the permissible remaining levels of oil and remaining dirt particles. For examples, Class 3-4-1 would require a refrigeration dryer with a high quality coalescing filter. Accordingly, all end users should be disaggregated according to air quality, quantity and pressure requirement. These key parameters dictate the end user grade with the required quality determined by the end users dryness and contamination level requirements (Table 4). Page 13 of 40 Sustainable Energy Ireland Compressed Air Technical Guide Quality Class DIRT Particle Size in Micron 1 0.1 WATER Pressure Dewpoint oC at 7 barg -70 OIL (including vapour) mg/m3 0.01 2 1 -40 0 3 5 -20 1 4 40 +3 5 5 - +7 25 6 - +10 - Recommended Dryer Desiccant Desiccant or Membrane Desiccant or Membrane Refrigerated or Membrane High Inlet Temp. Inlet High Inlet Temp. Inlet Table 3 – Air Contamination Classes (ISO 8573.1) Application Classes Air Agitation Air Bearing Air Gauging Air Motors Brick and Glass Machines Cleaning of Machine Parts Construction Conveying, Granular Products Conveying, Powder Products Fluidics, Power Circuits Fluidics, Sensors Foundry Machines Food and Beverages Hand-operated Air Tools Machine Tools Mining Micro-electronics Manufacture Packaging and Textile Machines Photographic Film Processing Pneumatic Cylinders Pneumatic Tools Process Control Instruments Paint Spraying Sand Blasting Welding Machines General Workshop Air Typical Quality Classes Dirt Water Oil 5 3 3 2 3 2 3 3 2 4-1 5 4 4 5 4 4 4 4 5 5 4 4 3 3 3 2 2 4 4 4 2-1 2 2 4 5 4 3 1 2 5-4 5-4 4 3 5 4 5 5 4 1 1 1 3 3 4 1 1 1 3 5 3 4 4 4 2 3 2 3 3 3 3 3 4 5 4 4 5 4 Table 4 – Typical Application Requirements Page 14 of 40 Sustainable Energy Ireland Compressed Air Technical Guide The following sections present a high level discussion of many of the common treatment facilities employed in industrial facilities. For a more detailed discussion of compressed air treatment, GPG 216 – Energy Saving in the Filtration and Drying of Compressed Air is an excellent starting point. Desiccant Air Dryers Twin tower desiccant dyers are generally thought to be one of the most effective dryer types. These dryers are split into two main groups: heatless and heated. Heatless dryers employ compressed air to regenerate the towers while heated dryers use electrical heating elements in the desiccant bed. One opportunity to save energy with desiccant tower dryers is efficient management of the dewpoint set point. The dewpoint is often needlessly set to -40oC, however a temperature of 15oC below the lowest winter temperature would suffice; in Ireland, a set point of -20oC would typically suffice. In all situations, compressed air drying should be appropriate to the energy service requirements and a holistic assessment of the system should be undertaken before undertaking any treatment alterations. Desiccant dryers rely on air or heat from the dry tower to regenerate the wet tower. The frequency of column changeovers, and the associated amount of purge air, is set assuming the dryer is used at maximum capacity – invariably on a set time schedule. As dryers are rarely used to their maximum capacity, expensive purge air is wasted. Dewpoint controllers are capable of controlling the purge cycles of towers by only engaging the purge cycle when it is required and can be an effective cost avoidance tool. The heatless type dryers are more expensive to operate, as they require anything from 10-18% of the total airflow during the purging process. The heated-type does not require the same volumes of air but do require hot air, which should be considered against the reduction in the amount of purge air. Some tower arrangements are orchestrated in such a way that they use a mixture of heat and heatless strategies. If a system’s energy requirements do not require air with a low dewpoint, the regeneration of non-duty section of the dryer can be facilitated by utilising the waste heat of compression (before the after-cooling)5. The compressor load and cooling efficiency will determine the actual range, however the dewpoint normally falls within -20oC to -30oC. The energy cost for such arrangements is often as low as 3%. Refrigerated Dryers Refrigerated dryers offer significant savings for a compressed air plant. Moisture in the compressed air stream is removed by condensing water vapour into a liquid. Accordingly, the air stream is cooled to the desired dew point. This process takes place in a heat exchanger and well designed refrigerated dryers can achieve dew points of 3oC – as long the compressed air temperature downstream of the dryer does not drop below this temperature, no liquid water will be present. 5 The screw compressor should be an oil free type or the air to be employed for regeneration should be appropriately treated (which can add to the overall cost of the solution). Page 15 of 40 Sustainable Energy Ireland Compressed Air Technical Guide It is vital to ensure refrigerated dryers are adequately maintained. A non-performing refrigerated dryer can have dewpoint temperatures as high as 12-16oC resulting in large quantities of water being carried over to the distribution network. Filters It is important to only install the type of filter(s) that are actually required. This will minimise pressure drops – thereby reducing compressor power consumption. There are three main types of filters: particulate filters for the removal of solid particles; coalescing filters for the removal of lubricant and moisture; and adsorbent filters for the removal of very fine contaminants. It is often the case that system components within the compressor station dictate which filter type is required. For example, a particulate filter and a coalescing filer should be installed before a desiccant-type dryer to prevent fouling of the desiccant bed. Additional filtering may be required to maintain the integrity of components downstream (a particle removal filter is normally used as an after-filter to prevent desiccant dust being carried over into the system). A watchful eye should be maintained on all pressure differentials across the treatment components on a system. Pressure differentials should not exceed 0.3 bar across the filters. 1.6.2 Localised Air Treatment In any system audit, the treatment regime should always be investigated. For example, it is common to identify a situation where the entire volume of compressed air is treated (drying and filtering) to meet the requirements of 5% of the energy requirements. In such instances, localised treatment of the compressed air immediately upstream of the critical end user should be investigated. The economics of such strategies are often excellent, with typical paybacks of 2 years or lower depending on the relative size of the systems. Page 16 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.7 Compressed Air Generation It is vital to gain an understanding of the system energy flow for this significant energy user. Figure 4 illustrates the typical energy flow for a compressor operating throughout the year at 7 bar. It is common to find compressed air system where only 4-8% of the energy utilised during the initial compression cycle is converted into usable energy. The most significant losses occur during the initial compression cycle itself. Figure 4 – Sankey Diagram illustrating the Energy Flow of a Typical Inefficient Compressor System 1.7.1 Compressor Sizing A more thorough description of compressor types is outlined in section 1.9.1, however the key point is that a facility should work with the vendors of generation technology to optimise a system so that the system components work to meet the requirements of the site and not the other way round. Inappropriate technology can fuel the costs associated with the system and complete redesigns may often be required. During any audit, a matrix should be generated and filled with any data related to configuration, make, capacity, pressure rating and other key parameters. 1.7.2 Discharge System Pressure The location of the compressor signal should be considered in any assessment. Any pressure drops upstream of this signal must be overcome by the compressor in order to achieve the correct set point. The compressor signal is typically located at the discharge of the compressor Page 17 of 40 Sustainable Energy Ireland Compressed Air Technical Guide package, however certain precautions should be taken if it is located downstream of the treatment instruments. For example, the control range pressure setting should be reduced to allow for the associated pressure drop. In addition, provision should also be made for exceeding the maximum allowable discharge pressure in the event of pressure differential becoming excessive. 1.7.3 Control The control system employed at the compressor station is one of the most critical determinates of energy consumption for the system. Effective control of the compressed air demand profile is required to ensure efficient system operation, low maintenance costs and optimum performance. A high performance control system is capable of running efficiently at periods of high and low demand operating within a fixed pressure regime and delivering the required volume of air. The primary objective of the control system is to run the minimum number of compressors and turn off any equipment that is not required. During any system audit, it is important to assess the demand profile. If the load is typically transient in nature, there may be a case for advanced and sophisticated system controls. On the other hand, if a facility’s profile highlights short bursts of significant demand, then there may be a case for some form of system or local storage. Accordingly, it is vital to assess both individual compressor control and system compressor control strategies. Individual Compressor Control Strategies Figure 5 illustrates two alternate compressor controls, which maintain a minimum system pressure of 6.0 bar. The system pressure is monitored so that when the pressure reaches a maximum pressure, the compressor output is reduced, and when the minimum system pressure is reached, the compressor is increased. The difference between the two pressure levels is termed the pressure range. The more antiquated control systems were slow and imprecise and they were characterised by wide control ranges. The new and more accurate control systems are far more precise. A smaller control range lends itself to a far lower average discharge pressure, which means significant power savings. In addition, tighter control of discharge pressure has additional benefits including less leakage and an increase in production quality control. Figure 5 – Impact of Control on System Pressure Page 18 of 40 Sustainable Energy Ireland Compressed Air Technical Guide There are five main types of controls, which can be employed for individual compressors: Start/Stop This is the simplest of all four controls. It can be employed for reciprocating or rotary screw type compressors where the motor is turned on or off in response to the discharge pressure. This type of compressor is employed where energy requirements are infrequent, as repeated stop-starts of a motor will cause it to overheat and require more frequent maintenance. Load/Unload This is one of the most common control strategies employed for rotary screw compressors. The motor runs continuously but it unloads the compressor when the discharge maximum pressure is reached. The system is ‘loaded’ (compressed air is directed into the distribution system) when the system pressure minimum set point is reached. An unloaded rotary screw compressor will continue to use 15-35% of full load energy while providing no useful work. Modulating This form of compressor control throttles the inlet air to meet the compressed air load. This form of control can be employed for screw and reciprocating compressors however it is more common for centrifugal machines. Multi-step (Part Load) Compressors can be designed to operate in stages so that the power consumption is proportional to the compressor output requirement. Such partially loaded conditions can achieve significant savings and this form of control is found on reciprocating compressors. Variable Speed Drives This form of control is gaining a wider acceptance as the industry begins to reap the rewards of recent advances in technology. A detailed overview is outlined in section 1.7.4. System Control Strategies In addition to individual compressor control, system compressor control strategies are required when a number of compressors are employed to generate the required flow of compressed air. These kinds of strategies are best suited to demand profiles B, C and D in Figure 6. The more antiquated form of control – involving pressure switches, which turned compressors on and off, as required – should be avoided as it leads to excessive system pressures (often as much as 1.5 bar). More energy efficient control strategies have emerged in recent times which can aid a facility reduce power consumption considerably. Sequencing Controls Sequencers orchestrate the actions of a number of compressors to meet demand as energy efficiently as possible by operating on a tight pressure range for the system. It does so by sequencing or staging individual compressor capacity to meet system demand. One compressor is designated as ‘master’ and additional compressors provide ‘top-up’ or trim (Figure 6). Periods of operating as master compressor should be shared amongst the pool of compressors to reduce maintenance costs. Network Controls This newer form of system control orchestrates the actions of multiple compressors individually and in terms of the system. Accordingly, individual controllers are networked together sharing operating information and other pertinent data. This is currently one of the most efficient means of controlling system pressure on the market ensuring the most efficient compressors perform the duty cycle for the system. Page 19 of 40 Sustainable Energy Ireland Compressed Air Technical Guide Figure 6 – Optimum Compressor Sequencing Strategies to meet Demand Profile Flow/Control Valve A Flow/Control Valve serves to separate the supply side from the demand side of the compressed air system. These components facilitate operating compressors close to their optimum pressures in order to maximise their efficiency so that the pressure on the demand side can be minimised to meet actual energy requirements. Careful consideration is required as to the size parameters for these components as they can be a source of excessive pressure drop due to poor sizing considerations. Air Receivers Storage or air receivers placed at strategic points in a system, which accommodate transient events, is a form of system control. This can be an effective tool in minimising compressor power consumption when a slow replenishment of these storage devices can be facilitated using an appropriate flow/control device . Higher-pressure supply air is fed into these storage vessels at a predetermined rate and available to meet variations in load thereby suppressing the instantaneous demand profile. This suppression has the effect of reducing instantaneous compressed air requirements while maintaining a reliable source of compressed air at a lower pressure. It should be noted that using receivers can only supplement compressors during very short periods of high demand. Page 20 of 40 Sustainable Energy Ireland Compressed Air Technical Guide It is important to install zero loss drain traps and ensure they are fitted with special acid resistant coating for oil free systems. Such automatic traps reduce maintenance. As identified in one of the facilities, if air receivers are located outdoors, trace heating technology should be employed to prevent icing during the cold season. 1.7.4 VSD Compressors Traditionally, a number of compressors provide the base load at a facility with one compressor providing top up. A standard compressor operating in this top up mode cannot ramp up and down to track transient demands; airflow is typically controlled by a valve that modulates between open and closed positions. Unfortunately, this method results in a higher discharge pressure, lower part load efficiencies, and increased overall power consumption. Accordingly, a strong economic case can often be made for installation of Variable Speed Drive (VSD) motor for the compressor at facilitates displaying inherently variant demand profiles for the top up compressor (demand profiles C and D in Figure 6). Capable of being fitted to reciprocating, rotary vane and screw machines, VSD motors control over a close pressure band minimising artificial demand and the need for control valves. These units are capable of a more dynamic air discharge to meet the demand at the required pressure. It does this by varying the speed of the compressor motor, which dramatically reduces energy consumption. In addition, the compressor is enabled with software to sense when it should be taken offline. Other benefits include reduced wear and tear of the compressor; compressor lifecycle extension; and increased compressor stability due to smooth start-ups. VSD motors can be integrated into existing machines however VSD controllers and motors supplied in conjunction tend to offer superior performance. It should be noted that if a unit is likely to be operated at 100%, a VSD compressor should not be procured; tests have shown a performance reduction in VSD compressors when 100% loaded. From experience, a case can often be made for the installation of a VSD compressor when loads for the top-up compressor lie in the 30-70% range. 1.7.5 Reduce Air Temperature (ambient air) It is common to find the compressors located in a utilities building where it is drawing warm air from neighbouring utilities equipment (boilers, etc.). Compressors should be located in a wellventilated area, or capable of drawing inlet air from ambient conditions where possible. A 1% reduction in compressor power consumption can be achieved through a 4oC reduction in inlet temperature6. 6 GPG 385 – Energy Efficient Compressed Air Systems Page 21 of 40 Sustainable Energy Ireland 1.8 Compressed Air Technical Guide Preventive Maintenance Preventative Maintenance is an important tool that should be employed to mitigate energy consumption and achieve components’ energy saving potential. A number of potential problems can arise in systems that are not regularly maintained (i.e. reduced compressor efficiency; increased leaks; excessive pressure differentials; poor air quality; reduced equipment lifecycles; etc.). The main areas, which should be incorporated into any maintenance regime, are discussed below: Equipment Actions Compressors Ensure all belts are adequately tensioned and working effectively every 400 hours of operation (too tight – can lead to excessive wear, too loose – can lead to slippage and energy waste). Ensure the operating temperature is ‘as per specification’ Ensure all lubricants are ‘as per specification7’ Inspect oil levels daily and take action as appropriate (ensure the correct volume is maintained as too much can be equally as damaging as too little). Ensure the lubricant filters are changed ‘as per specification’. Ensure all heat exchanger and intercooler surfaces are clean and foul free. Poor motor cooling can have a multitude of adverse effects such as increased motor temperatures and windings resistances; shorter motor life; increased downtime; increased maintenance; etc.). Filters Inlet filters should be cleaned to ensure the compressor is not subjected to excessive and undue loading stress levels. Inspect and clean ‘as per specification’ or when the pressure differential dictates (pressure drop should not exceed 0.3 bar). Dryers Inspect and clean ‘as per specification’ or when the pressure differential dictates. The pressure differential should not exceed 0.3 Bar. Ensure the dryer inlet temperature does not exceed 35oC. Check pressure dew point against specification and service requirements. Water Cooling System Inspect all key parameters associated with the water-cooled systems Inspect fans and pumps to ensure they are operating at peak performance Separators Air Receivers Distribution Inspect and clean ‘as per specification’ or when the pressure differential dictates (pressure drop should not exceed 0.7 Bar however an earlier change often makes economic sense). Check and clean all drain traps (an open trap is a substantial compressed air leak, a drain trap stuck in closed will cause condensate to become backed up resulting in carry over to the end users). Inspect for leaks (section 1.5.2) 7 Utilising low-grade lubricants can have an extremely adverse effect on the performance of a compressor leading to increased wear and tear; lower generation efficiency and a reduced lifecycle. Page 22 of 40 Sustainable Energy Ireland Compressed Air Technical Guide Training for the efficient operation of a compressed air plant should be considered as part of a holistic approach to the management of the system. Such a training schedule should include an action plan to aid operators, maintenance, facility managers and management staff to: • Benchmark the Performance of a Compressed Air System • Identify Compressed Air Leaks • Identify Preventative Maintenance Tasks/Checklist • Undertake System Analysis • Understand Controls Ultimately, those undertaking the course should understand the components in a system and how they interact to dictate the system’s operation and energy consumption. Any training package should have some form of follow-up evaluation to ensure participants are employing the intellectual capital leveraged from the training. Figure 7 – Acceptable pressure losses throughout compressed air system8 8 Acceptable pressure losses may be significantly less depending on equipment utilised in the plant. The figures quoted in this figure merely serve as a guide for a typical system. Page 23 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.9 Purchasing Policy Successful management of a compressed air system is not limited to operation and maintenance. Adequate structures must be put in place to ensure that any future purchases of components are based on lifecycle economics. The capital costs which are initially paid during the procurement stages for compressor components pale in significance to operating costs (Figure 8). Accordingly, it is vital that the lifecycle costs associated with these pieces of equipment are evaluated before any decisions are made. This applies to all components on the system, not just those in the compressor station. Typical Cost of a Compressed Air System over a Ten Year Period Maintenance 10% Capital Cost 15% Energy Cost 75% Figure 8 – Typical 10-year Lifecycle Costs of a Compressed Air System9 Pressure Reduction Policy As equipment is being refurbished/replaced/purchased, there should be a policy of reducing pressure requirements. For example, some companies have a programme of replacing 6 bar actuators with 4 bar actuators when machines are being refurbished. Nitrogen If Nitrogen is generated on site, it may be possible to recover some compressed air from the N2 system, depending on usage and generation profile. 1.9.1 Compressors It is vital to select a compressor to match the load at your facility. Operating oversized compressors as a means of generating compressed air is extremely inefficient as the intrinsic performance characteristics of compressors lead to a larger energy requirement per volume of compressed air generated at part loads. Smaller compressors with appropriate and suitable 9 GPG 241 - Energy Savings in the Selection, Control and Maintenance of Air Compressors Page 24 of 40 Sustainable Energy Ireland Compressed Air Technical Guide control for the facility’s requirements should be procured and installed to service the facility’s requirements. This generally prepares a plant for any ad hoc additions to the compressed air system going forward. Figure 9 –Pressure Limitations Vs Flow Capacity for Three Compressor Groups The capacity of the system requires careful consideration during the procurement stages. For example, the capacity should not be taken as simply the sum total of the maximum user requirements; the median air consumption for all end users should be summed to determine the system capacity. In addition, periods of high short-term demands should be supplied with air from local air receivers strategically located throughout a facility. Be mindful of vendor specifications of performance; they are typically based on ideal conditions, which may bare little in common with physical plant conditions. Another point for consideration is whether or not to procure lubricated compressors. For example, oil-free rotary screw and reciprocating compressors tend to be more expensive to operate, higher initial costs and higher maintenance. However, the treatment facilities required for lubricant compressors can often lead to inefficient systems if not properly maintained. A detailed survey of the end use requirements and existing equipment should be carried out before making this decision. There are many different types of compressors, however in most cases, multiple-stage compression results in more efficient operation. Multiple-stage means that the final discharge Page 25 of 40 Sustainable Energy Ireland Compressed Air Technical Guide pressure is generated over several steps. Efficiency is significantly increased as a result of the cooling of air between stages, thereby reducing the volume and work required to compress the air. The three main types of compressors are Reciprocating Compressors, Rotary Screw Compressors, and Centrifugal Compressors. A brief overview for each of these types is discussed below; for a more detailed discussion, consult GPG 241 - Energy Savings in the Selection, Control and Maintenance of Air Compressors. Page 26 of 40 Figure 10 – Comparison of Common Compressors (Good Practice Guide 241) Rotary Screw Compressors Rotary Screw Compressors are the most common compressors used in industry today and do have many inherent advantages over reciprocating compressors including a lower capital cost; lower maintenance costs; smaller size and reduced vibration and noise. Rotary Screw machines generally have an oil carry over of around 4ppm, however the air can be appropriately treated for oil-free requirements. Inherently oil free machines can be procured where required. As with all compressor purchases, a full lifecycle economics investigation should be carried out before selecting the appropriate technology. Reciprocating Compressors Reciprocating compressors were historically the most commonly used compressors. However, the higher capital and maintenance costs have reduced their market dominance in recent years. Despite this, it is generally accepted that multi-stage version of these units are the most efficient compressor type. Centrifugal Compressors Centrifugal compressors are generally only suitable for high volume applications with little variance in the demand load. These compact units are available in two, three and four stage compression technology. Generally centrifugal compressors are three stage units – which tend to be more efficient than rotary screw compressors – with inherent efficiencies approaching those of double-acting reciprocating compressors. Care should be taken at plants near river estuaries or ponds; freezing fog can potentially blind the elements of fine filters employed for centrifugal compressors. In such cases, appropriate protection should be taken – for example installation of swirl prefilters or heated face elements. Vane Compressors Vane Compressors can be found in higher demand applications however they are not normally the first choice for industrial compressed air supply applications. Typically, vane compressors don’t have actual receivers, but are designed to run continuously. This on-off control responds to signals from pressure switches Discriminating Vendor Components Evaluating brands of compressed air components can be a daunting task. Discriminating through the performance criteria associated with pneumatic equipment can be difficult as vendors often publish data at conditions that benefit their products. In order to differentiate bids from vendors in a meaningful manner, vendors should be asked to quote at the same inlet conditions, operating pressure etc to enable easier analysis (i.e. performances quoted to ISO1217 (Displacement Compressors Acceptance Tests)). An educated buyer can discriminate through this information by prudent examination, meaningful discussion with vendors and where necessary, discussion with energy experts. Sustainable Energy Ireland Compressed Air Technical Guide 1.9.2 Treatment and End Users As discussed previously, end user requirements have a profound impact on the holistic performance of a compressed air system. Accordingly, it is vital to ensure that certain measures are taken to ensure no adverse effects result from the procurement of unsuitable equipment. In all cases, vendors should work with facilities to ensure the maximum performance of the system can be assured. System components should be selected based on pressure drop; pressure requirement; airflow rate and temperature – this information should always be available from vendors. Aftercoolers, separators, filters, dryers, regulators, lubricators, hoses and connections should be selected to have the minimum possible pressure drop for rated conditions. A number of end user components (valves, etc.) have internal leaks as part of the design. Where possible, a purchasing policy should be generated to ensure that such devices are not purchased and more energy efficient equivalents are sought. 1.9.3 Seek Advice Engaging a qualified third party specialising in compressed air during the procurement stages should not be overlooked. The augmentation of practical experiences, industry knowledge and cost saving exercises gained from a number of other sites is always of considerable benefit. Page 29 of 40 Sustainable Energy Ireland Compressed Air Technical Guide 1.10 Heat Recovery Due to a large quantity of energy released to atmosphere during the normal compression cycle, there is significant scope to recover the air/water utilised to cool the compressed air. Typically, 80-93% of the electrical energy consumed by a compressor is converted into heat. The installation of a heat recovery unit should be considered as these units can reclaim anywhere from 50-90% of the available thermal energy. These units are available for both the air-cooled and the water-cooled compressors. However despite this large reserve of energy, most facilities do not have any form of heat recovery system installed. In order to consider upgrading a compressor system for a heat recovery unit, there must be neighbouring and an appropriate thermal energy requirement. Such thermal energy requirements would include: space heating; industrial process heating; water heating; or boiler feed-water preheating (Figure 11). Figure 11 – Heat Recovery Options (Good Practice Guide 238)10 Air-Cooled Rotary Screw Compressors Packaged Air-cooled rotary screw compressors are ideal for heat recovery options and generally only require a small number of modifications. Ambient air is passed across the system’s aftercooler and lubricant cooler where it is heated as it extracts the heat from both the compressed air and the lubricant. When employed for space heating, they generally only require the additional ducting, an additional fan to overcome any back pressure on the compressor cooling fan setup, and some 10 Good Practice Guide 238 offers an excellent overview of assessing the benefit of employing heat recovery for a compressed air system. Page 30 of 40 Sustainable Energy Ireland Compressed Air Technical Guide sort of thermostatic damper control to maintain thermally comfortable conditions. As a general rule, for every 2m3/min of capacity at full load, there is just over 10 kW of available energy. The recovery efficiency of typically 80-90% for such arrangement and air outlet temperatures of 1520oC above ambient air inlet temperatures are typical11. Another option is the extraction of waste heat from the lubricant coolers found in packaged water cooled reciprocating or rotary screw compressors to generate hot water. A heat exchanger can be employed to extract the waste heat and generate water, which can be utilised for a variety of processes at the plant. Additional controls may be required to ensure the operator can vary the heat extracted from the unit. Water Cooled Compressors Although not as common due to the additional stage of heat exchange required to recover heat from water-cooled compressors, optimising a water-cooled compressor system for recovery can still be an economically attractive option. Typical heat recovery efficiencies range from 50-60%. Many water-cooled compressors tend to be quite large meaning there is typically vast quantities of heat available from these machines. 1.11 Compressed Air Audit Overview A full system audit will highlight the true ‘cost’ of compressed air and detail a programme of opportunities that should be followed to improve the efficiency and productivity at a facility. Compressed Air audits can be carried out by in-house personnel however a ‘fresh pair of eyes’ in the form of a specialised compressed air expert should always be considered. Several firms specialise in compressed air audits and will have augmented a great deal of experience and knowledge from other facilities. While it is an additional expense to secure the services of compressed air experts, the recommendations which result from these investigations usually means they pay for themselves within a short period of time. The quality and comprehensiveness of audits can vary greatly. Accordingly, some simple rules of engagement are advised. An auditor should be fully system (and component) independent and display complete vendor impartiality. In addition, a compressed air system audit should go beyond merely focusing on the compressor station but focus on the holistic performance as laid out in this document. There are various categories of audits. It is often the case that a more thorough audit will be required incorporating some intensive data mining to determine the appropriate technology or control which would lead to the most economically justifiable savings. The extra time and expenses are often justifiable as the opportunities highlighted during these audits frequently pay for themselves in a relatively short period of time. 11 When air is drawn in from ambient conditions, some form of frost protection may be required. If the air is drawn in from an indoor area (and the recovered air is released in a different area), care must be taken to ensure the static pressure in the compressor room is not overly reduced as this has an adverse affect on compressor efficiency. Page 31 of 40 Sustainable Energy Ireland Compressed Air Technical Guide RESOURCES I Useful Compressed Air Websites II Good Practice Guides III Self Assessment Template Compressor Types Page 32 of 40 Sustainable Energy Ireland Compressed Air Technical Guide I Organisation SEI Compressed Air and Gas Institute British Compressed Air Society Link Useful Compressed Air Websites Details (From web-site) www.sei.ie http://www.cag i.org Since 1915, the Compressed Air and Gas Institute (CAGI) has been the leading organization representing manufacturers of compressed air system equipment, including air compressors, blowers, pneumatic tools and air and gas drying and filtration equipment. For over 80 years, the Institute has been working to improve production, proper use and increased distribution of equipment used in compressed air and gas systems. http://www.brit ishcompresseda irsociety.co.uk BCAS is the UK trade association for manufacturers, distributors and end users of compressed air and vacuum products and services. BCAS actively represents the interests of members and the compressed air industry to both UK Government, European and international institutions. BCAS was formed in 1930 at the instigation of Government, the primary purpose to provide a forum for British manufacturers to encourage the manufacture of products for import substitution. The inaugural meeting was held January 8, 1930 at the Institution of Civil Engineers. FL0069A - Everyone's Guide to Saving Energy in Compressed Air The Carbon Trust http://www.the carbontrust.co. uk/energy GPG385 - Energy efficient compressed air systems GPCS369 - Compressed Air Leakage Reduction Through the Use of Electronic Condensate Drain Traps ECG040 - Compressing Air Costs - Generation Enhanced Capital Allowances (ECAs) enable a business to claim 100% first-year capital allowances on their spending on qualifying plant and machinery. There are three schemes for ECAs: - Energy-saving plant and machinery Enhanced Capital Allowances. http://www.eca .gov.uk - Low carbon dioxide emission cars and natural gas and hydrogen refuelling infrastructure - Water conservation plant and machinery Businesses can write off the whole of the capital cost of their investment in these technologies against their taxable profits of the period during which they make the investment. This can deliver a helpful cash flow boost and a shortened payback period x-Pneumatic http://www.xpneumatic.com Substantial energy savings in all industries where compressed air is used in production 1. faster cylinder speeds, depending on cylinder configuration. In optimal applications, speeds can be as much as 200-300% faster. 2. energy cost reductions of more than 30%. 3. air exhaust cuts of almost 1/2, reducing air filter needs 4. noise level reductions in the production unit 5. other cost reductions with reduced air needs, simpler valve setup, no need for speed regulators Page 33 of 40 Sustainable Energy Ireland Organisation Link Compressed Air Technical Guide Details (From web-site) Technical database During the course of a year we are repeatedly asked similar questions, some technical and some pretty fundamental. To assist compressed air users everywhere, we have compiled a Technical Database. Browse Technical Database >> Dictionary of Compressed Air Terms. Cashflo http://www.cas hflo.co.uk/index .html The History of some Compressor types. The Properties of Air. The Discovery and make-up of our Atmosphere. An Introduction to Compressed Air Dryers. A Theoretical Energy Calculation for a compressor. Safety, Health and The Environment with respect to the compressed air user. UK Statutory Legislation Compressed Air Challenge http://www.co mpressedaircha llenge.org The Compressed Air Challenge is a voluntary collaboration of industrial users; manufacturers, distributors and their associations; consultants; state research and development agencies; energy efficiency organizations; and utilities. This group has one purpose in mind - helping you enjoy the benefits of improved performance of your compressed air system. More about the Compressed Air Challenge. Click here to purchase the BestPractices Manual. If you are a CAC Sponsor, please refer to the Secure Sponsor Area of this website to purchase the BestPractices Manual. Page 34 of 40 Sustainable Energy Ireland Compressed Air Technical Guide A number of Good Practice Guides (GPG’s) have been published by the Carbon Trust. These are freely available on www.carbontrust.co.uk or www.energymap.ie. The textual description of each guide outlined below is taken from the carbon trust website. Good Practice Guide 216: Good Practice Guide 238: Energy Saving in the Filtration and Drying of Compressed Air. Heat Recovery from Air Compressors This guide provides advice on practical ways of improving the energy efficiency of filtration and drying operations. The guide starts by describing the contaminants that may be present in air, and gives guidance on selecting the level of treatment appropriate to the application. The different equipment available for treating air are described, with details of associated energy costs and energy-saving opportunities. This guide offers advice on practical ways of recovering and utilising waste heat from air compressors. An outline procedure, illustrated with examples, is provided for assessing the likely benefits of recovering waste heat. Worked examples of some of the calculations involved are included to assist in assessing the economics of a particular situation. Case studies are included which demonstrate the savings that can be made. This guide will help plant engineers, energy managers and industrial users of compressed air to minimise the energy costs associated with treating air through best practice. It complements Energy Consumption Guide (ECG) 42, ‘Compressing Air Costs - Treatment’. Page 35 of 40 Sustainable Energy Ireland Compressed Air Technical Guide Good Practice Guide 241: Good Practice Guide 385: Energy Savings in the Collection and Maintenance of Air Compressors. Energy Efficient Compressed Air Systems This guide shows how to select, control and maintain plant to bring down the cost of generating compressed air. It describes how to carry out a thorough assessment of site compressed air requirements. Guidance on plant selection is provided, exploring opportunities to reduce operating, energy and capital costs at the design stage. It emphasises that small differences in plant efficiency can save far more than the initial difference in capital cost. The guide also covers efficient control options and necessary maintenance for long-term reliability and energy efficient operation. Case studies throughout the text provide practical examples of the savings that can be achieved. The information is drawn together in a worked example of specifying and analysing quotes for air compressor installation. The guide covers stationary compressor installations generating pressures between 5 and 14 barg and will be of particular benefit to maintenance and plant engineers. Compressed air is often described as the fourth utility. Despite it being an expensive form of energy, compressed air is essential in many industries. There are many opportunities to make a compressed air system more efficient. Many industrial users of compressed air could reduce their cost of compressed air by over 30% with minimal investment. This guide looks at managing the air system, reducing misuse of air, the distribution network, compressor selection and control, air receivers, air treatment and condensate management. This 36-page guide includes a glossary and a useful series of checklists. Page 36 of 40 SELF ASSESSMENT TEMPLATE A template for entering the details of a compressed air system has been developed. The spreadsheet can be found on SEIs website at: www.sei.ie/energyagreements. The input fields have drop-down menus to assist with correct filling. Data entered can assist with understanding the associated costs of compressed air, and can also be a useful reference when using external consultants in the assessment of system performance. Enter compressor details, storage, filters, dryers, etc. Also input end use requirements for the site. Sustainable Energy Ireland Compressed Air Technical Guide Page 39 of 40 Sustainable Energy Ireland Compressed Air Technical Guide This document is an output from SEI’s Energy Agreements Programme Special Working Group on Compressed Air 2007. The following companies participated in the special working group: Company Astellas Ireland Ltd, Dublin Boliden Tara Mines Intel Ireland Pfizer Little Island Vistakon Johnson & Johnson Xerox Europe, Dundalk RPS Ltd. FDT Ltd. Air Technology Ltd. Lokalenergi SEI Representative(s) Alan Timms Dónal O Murchú James Clancy / Kevin Geoghegan Martin O'Connor Patrick Liddy / John Coffey Tom DeLasa / Padraig Murphy Elmer Morrissey / Richard Morrisson Michael Clancy Eric Harding Bo Kuraa David McAuley Role Participating Company Participating Company Participating Company Participating Company Participating Company Participating Company Consultant Consultant Consultant Consultant Project Leader The guide can be downloaded from SEIs website: www.sei.ie/energyagreements Content prepared by: Unit 3, University Technology Centre, Curraheen Road, Cork. Date: July ‘07 Tel: 021 - 4804600 Fax: 021 – 4804658 Page 40 of 40