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Sunday, May 29, 2011

Compressed Air Energy Storage (CAES)

Compressed Air Energy Storage (CAES) is a way to store energy generated at one time for use at another time. At utility scale, energy generated during periods of low energy demand (off-peak) can be released to meet higher demand (peak load) periods.

Compression of air generates a lot of heat. The air is warmer after compression. Decompression requires heat. If no extra heat is added, the air will be much colder after decompression. If the heat generated during compression can be stored and used again during decompression, the efficiency of the storage improves considerably.

There are three ways in which a CAES system can deal with the heat. Air storage can be adiabatic, diabatic, or isothermic:
  • Adiabatic storage retains the heat produced by compression and returns it to the air when the air is expanded to generate power. This is a subject of ongoing study, with no utility scale plants as of 2010. Its theoretical efficiency approaches 100% for large and/or rapidly cycled devices and/or perfect thermal insulation, but in practice round trip efficiency is expected to be 70%. Heat can be stored in a solid such as concrete or stone, or more likely in a fluid such as hot oil (up to 300 °C) or molten salt solutions (600 °C).
  • Diabatic storage dissipates the extra heat with intercoolers (thus approaching isothermal compression) into the atmosphere as waste. Upon removal from storage, the air must be re-heated prior to expansion in the turbine to power a generator which can be accomplished with a natural gas fired burner for utility grade storage or with a heated metal mass. The lost heat degrades efficiency, but this approach is simpler and is thus far the only system which has been implemented commercially. The McIntosh, Alabama CAES plant requires 2.5 MJ of electricity and 1.2 MJ lower heating value (LHV) of gas for each megajoule of energy output. A General Electric 7FA 2x1 combined cycle plant, one of the most efficient natural gas plants in operation, uses 6.6 MJ (LHV) of gas per kW–h generated, a 54% thermal efficiency comparable to the McIntosh 6.8 MJ, at 53% thermal efficiency.
  • Isothermal compression and expansion approaches attempt to maintain operating temperature by constant heat exchange to the environment. They are only practical for low power levels, without very effective heat exchangers. The theoretical efficiency of isothermal energy storage approaches 100% for small and/or slowly cycled devices and/or perfect heat transfer to the environment. In practice neither of these perfect thermodynamic cycles are obtainable, as some heat losses are unavoidable.
A different, highly efficient arrangement, which fits neatly into none of the above categories, uses high, medium and low pressure pistons in series, with each stage followed by an airblast venturi pump that draws ambient air over an air-to-air (or air-to-seawater) heat exchanger between each expansion stage. Early compressed air torpedo designs used a similar approach, substituting seawater for air. The venturi warms the exhaust of the preceding stage and admits this preheated air to the following stage. This approach was widely adopted in various compressed air vehicles such as H. K. Porter, Inc's mining locomotives and trams. Here the heat of compression is effectively stored in the atmosphere (or sea) and returned later on.

Compression can be done with electrically powered turbo-compressors and expansion with turbo 'expanders' or air engines driving electrical generators to produce electricity.

The storage vessel is often an underground cavern created by solution mining (salt is dissolved in water for extraction) or by utilizing an abandoned mine. Plants operate on a daily cycle, charging at night and discharging during the day.

Compressed air energy storage can also be employed on a smaller scale such as exploited by air cars and air-driven locomotives, and also by the use of high-strength carbon-fiber air storage tanks.

Source: http://en.wikipedia.org/wiki/Compressed_air_energy_storage

Monday, May 2, 2011

Theory of air compression 2

An air compression is a means by which one type of energy is converted to another. During this conversion certain losses occur because of the rise in temperature of the air as it compressed. In general practice, the air is stored in a receiver and heat is lost both in the receiver and pipe lines running to equipment. Since the rise in temperature of the air is a direct loss of energy. We want to keep it down to a minimum. The ideal method is to compress air isothermally but this is impossible in practice owing to lack of time necessary to affect transfer.
Water jackets and inter-cooling can be used to keep the temperature down. These have the effect of reducing the compression index (n) to something less than 1.4.

When air is compressed to a pressure to exceeding about 4 bar it is usual to compress it in stages, with intercooling between each stage. This considerably reduces the total amount of work required on the air.
For two stages compressing, the air is compressed in the first (low pressure) stage adiabatically from p1 to p2 and then enters the intercooler where it is cooled down to the original temperature. Its volume is thereby reduced to V2 which is on the isothermal line. This volume of air now enters the high pressure cylinder, and is compressed to the final pressure and volume (p3 and V3). The law of compression is assumed to be the same for both compressors, namely:

p Vn = C

The pressure of intercooling to give the minimum of work done is when:
 p2 = sqrt(p1 x p3)


Compression may be done in three or more stages to reduce the amount of work. Multistage compression approaches isothermal compression as the number of stages is increased.

Sunday, May 1, 2011

Theory of air compression

Air is not a perfect gas but for practical purpose the laws relative to perfect gases may be applied to it.

Boyle’s law states that: The absolute pressure of a gas varies inversely as the volume, provided the temperature remains constant.

p V = a constant

where: p = pressure in bar, V = volume in m3.

Charles’ law states that the volume of a gas under constant pressure, or the pressure of a gas under constant volume, varies as the absolute temperature. Therefore V varies as T, and p varies as T where T is the absolute temperature.

If the two laws are combined, we get:

p V / T = constant

The constant is usually denoted by R and therefore:
p V = R T

It can be shown that the value of the constant R applicable to air is 287.0 J/(kg K).
The relation between the pressure and volume of air during its expansion and compression may be represented by:

p Vn = R T

where ‘n’ has value which depends on the addition or subtraction of heat during the process.
When the temperature remains constant during compression or expansion they is said to be isothermal and the value of ‘n’ is one. In order to obtain pure isothermal compression it would be necessary to remove heat from the air at the same rate as heat is produced by the work done on the gas. When a gas expands and when no heat passes during expansion or contraction they is said to be adiabatic.

Saturday, April 30, 2011

Opportunity of Compressed Air Savings

Approximately 10 % of all electrical power used in industry comes from compressed air. This is proof of its widespread usage but it is also evidence of the potentially large saving in costs which could be achieved if the energy management opportunities are put into practice.

Normally, the purpose of compressed air systems in the industrial sectors is to deliver the necessary volume of air at the required pressure and temperature to the correct places. Compressed air is used for operating pneumatic equipments, cleaning purposes, and other general services. This is accomplished by a distribution system consisting of pipes, valves and fittings. The Compressed Air pipe work is arranged in the form of ring mains with interconnections to points of end-users.

Careful evaluation of existing compressed air systems can ensure against improper operation, and poor energy utilization. Alert design, operations, and maintenance personnel, with an awareness of energy management, can achieve significant savings in areas such as:
  • Detection and elimination of leaks.
  • Reduction of friction losses and the associated pressure drops.
  • Application of new technology.

Friday, April 8, 2011

Compressed Air System Energy-Reduction Case Study (Part 2)

Let's continue from [Compressed Air System Energy-Reduction Case Study (Part 1)]

Compressed Air Energy-Reduction Strategy

Project Goals and Implementation

Following the IAC assessment, FUJIFILM’s maintenance team formulated project goals and an implementation plan that centered on the utilization of existing facility infrastructure and equipment. The team’s implementation strategy was divided into three phases and focused on increasing the system’s storage capacity to handle production peaks and valleys; lowering air compressor operating pressure; repairing system leaks; and ultimately, operating the facility with one compressor. The team’s strategy was also aided by the company’s closure of its Orange Park, Florida, operations. This facility housed a 75 horsepower (HP) air compressor, a dryer, and a receiver, which the Dayton facility incorporated into its efforts.

Project success, then, depended on the accomplishment of four specific goals:
  • To increase system redundancy, therefore increasing
    system reliability
  • To reduce system maintenance costs
  • To reduce overall facility energy use
  • To eliminate the use of nitrogen when compressed air
    systems are down.
Phase I
Phase I was justified using maintenance-cost-reduction estimates. Labor was billed as a maintenance expense to the existing budget. During this phase, the facility installed Orange Park’s 75 HP air compressor in Building 5, a receiver in Building 6, and a 2-inch airline from Building 5 to Building 6. The 60 HP air compressor in Building 6 was then shutdown for repair and established as a backup unit. The building’s piping was also combined with its heat installation. Phase I was completed in May 2008.

Phase II
The Dayton facility justified Phase II to FUJIFILM Corporate by utilizing total project energy-saving estimates. During this phase, piping was installed from Building 5 to Buildings 1 and 6, and an additional receiver was installed in Building 1. The existing 50 HP air compressor and dryer in Building 1 were
shutdown for maintenance and repair and established as a backup unit. This established the 75 HP air compressor in Building 5 as the facility’s central unit. Phase II was completed in March 2009.

Phase III
During Phase III, the maintenance team developed and implemented a Leak Detection and Repair (LDAR) program (completed in the fall of 2009), and developed a quarterly preventative maintenance program to repair system leaks and reduce the amount of compressed air losses. Additionally, the facility gathered data that indicated a 2 PSIG drop in pressure resulted in a 1% reduction in cost. The team reduced compressor set pressure to 105 PSIG, which resulted in POU delivery of 98 PSIG.

Source: http://www1.eere.energy.gov/industry/saveenergynow/pdfs/fujifilm_case_study.pdf

Thursday, April 7, 2011

Compressed Air System Energy-Reduction Case Study (Part 1)

FUJIFILM Hunt Chemicals U.S.A. Achieves Compressed Air System Energy-Reduction Goals with a Three-Phased Strategy.
In an attempt to eliminate equipment failures and downtime issues associated with the plant’s compressed air system, FUJIFILM Hunt Chemicals U.S.A.’s in-house maintenance team worked with a team of faculty and students from the Tennessee Technology University Industrial Assessment Center (IAC) to conduct an assessment at its Dayton, Tennessee, facility to identify opportunities for improvement. Following the assessment, the team formulated an implementation plan that would increase the system’s reliability, reduce system maintenance costs, reduce the facility’s overall energy use, and eliminate the use of nitrogen when compressed air systems are down.

The Energy Situation
The Dayton facility was experiencing excessive downtime due to chronic air compressor failures and significant inefficiencies throughout its compressed air system. In 2007 alone, system operating costs totaled over $45,000, with maintenance and repair costs exceeding $17,000. The problems FUJIFILM was experiencing were also causing frequent interruptions in the facility’s production operations. Due to the nature of these operations, the facility could not afford to experience the downtime required to complete compressed air system maintenance. The facility was depending on a backup operating system that relied on the utilization of onsite nitrogen, which is normally reserved for processing flammable materials. While maintenance staff were certified in both quality and environmental-management systems—ISO 9001 and 14001 standards, respectively—they lacked the parts and system expertise needed to effectively support the
compressed air generating equipment.

Additional Costs Incurred with Old Compressed Air Scheme:
  • Maintenance = $1,296
  • Nitrogen Backup = $7,921
  • Repair = $7,877
  • TOTAL = $17,094
Furthermore, the frequency of equipment failures indicated inherent and systemic inefficiencies, including unutilized capacity generation and overstated requirements. These issues led the facility Maintenance Manager, Manuel Calero, and his team to partner with the Tennessee Technology University IAC, sponsored by the U.S. Department of Energy’s Industrial Technologies Program (ITP), to conduct an overarching assessment of the Dayton facility’s compressed air system. ITP’s IAC program provides eligible small- and mid-sized manufacturing plants with no-cost energy assessments. In 2008, a team of engineering and technology students and faculty from Tennessee Technology University visited the Dayton plant to conduct the compressed air system assessment to identify potential savings opportunities.

Developing a Baseline
The IAC and in-house maintenance team’s first step was to baseline the system’s demand-side air requirements to determine the system’s actual efficiency. The site’s original compressed air system scheme consisted of two Ingersoll Rand air compressors, located in Buildings 1 and 6.1 Compressed air in these buildings was used in a variety of processing operations that facilitated material delivery through a system of pipelines. Major uses of the air included the operation of pneumatic control devices, such as actuator valves and cylinders, and liquid transfers via air diaphragm pumps to appropriate storage tanks. These transfer rates
were critical to maintaining quality in both the process and product. To establish the baseline, the IAC team calculated the cost of air production; gathered initial measurements of energy, flow, pressure, and leak load; and estimated energy consumption, which was then correlated to the appropriate production levels. The team also conducted energy surveys with the assistance of Ingersoll Rand. This effort required connecting amp and flow meters to each compressor for five days. This allowed the facility to accurately assess energy versus standard cubic feet per minute generated and used. Results of the assessment showed that both facility compressors were set to run at 120 pounds per square inch (PSIG), but were only delivering between 90 to 95 PSIG at point of use (POU), and were, at times, dropping as low as 80 PSIG. Additional findings demonstrated that higher air use was occurring during transfers—as opposed to reactions—and that the system’s air use was cyclical, depending on production. It was also confirmed that Production Line 1 had
excess capacity. The compressed air distribution system also contained significant leaks. A concurrent review of existing system dryers indicated subpar performance and explained undue levels of moisture in the system. Most importantly, though, the data indicated that the Dayton facility could be operated using only one compressor.

Read more details in [Compressed Air System Energy-Reduction Case Study (Part 2)]

Wednesday, April 6, 2011

Stabilizing System Pressure

Stabilizing system pressure is an important way to lower energy costs and maintain reliable production and product quality. The need to stabilize system pressure should be guided by the compressed air demand patterns and the minimum acceptable pressure level required for reliable production. High-volume intermittent air demand events can cause air pressure to fluctuate, which is often misinterpreted as insufficient pressure. In some cases, improperly set compressor controls will cause another compressor to start, but because of the time required for the new compressor to ramp up, there will be a shortfall of air supply to the system. Such a delay can cause the system pressure to decay, resulting in lost production. Three methods can be used to stabilize system pressure: adequate primary and secondary storage, Pressure/Flow Controllers (P/FCs), and dedicated compressors.

Primary and Secondary Storage

One or more compressed air applications having large, intermittent air demands can cause severe, dynamic pressure fluctuations in the whole system, with some essential points of use experiencing inadequate pressure. Such demand is often of short duration; properly sized primary and secondary storage can supply the needs of the intermittent demand. The time interval between the demand events is adequate to restore the storage receiver pressure without adding compressor capacity. Primary storage receivers can:
  • Prevent frequent loading and unloading of compressors
  • Collect condensate, which may be carried over from the aftercooler and moisture separator
  • Provide some radiant cooling to reduce moisture content and air dryer load if located in a cool location and installed upstream of the dryer
  • Provide dampening of pressure pulsations from reciprocating compressors.
    Secondary storage receivers can be used to:
  • Supplement the primary receivers to stabilize system pressure and thus keep unneeded compressors from starting
  • Supply adequate compressed air for a single intermittent event of a known duration.
The secondary receiver should be located as close to the end use as is practicable and its pressure rating must be at least equal to that of the primary receiver(s).

Pressure fluctuations may also occur due to inadequate storage or because the system pressure is at or near the lowest level of the compressor pressure control band. If a large, intermittent demand event occurs when the pressure is at or near the lowest level in the control band, the pressure in the distribution piping falls even further, affecting critical end-use applications. In such a case, the installation of a relatively small receiver with a check valve upstream of the application causing the demand event may address the problem.

Pressure/Flow Controllers

A Pressure/Flow Controller (P/FC) is a device that serves to separate the supply side of a compressed air system from that system’s demand side. P/FCs use the principle of operating compressors to fi ll and store air in receivers at higher pressures. P/FCs then reduce the pressure and supply it to the system at the pressure required by that system’s compressed air applications. P/FCs work with pilot-operated regulators or electronic controls to sense and monitor the system’s pressure downstream of the valves. Controlled pressure and adequate upstream storage are critical to satisfactory performance. P/FCs normally respond rapidly to demand fl uctuations and maintain system pressure within a narrow band. For peak demand events, suffi cient storage is necessary to release the stored air quickly into the system to maintain required downstream pressures within an acceptable tolerance. With proper design and system controls, storage can be used to meet air demand and reduce compressor run time.

Dedicated Compressors

Applications some distance from the main compressor supply or those with pressure requirements that differ from the main system requirements may be served by a dedicated compressor. Small or unit type compressors (generally up to 10 hp maximum) can be very suitable for an application whose pressure level is higher than that of the plant’s other applications. Generally, such compressors can be located close to a point of use, avoiding lengthy piping runs and pressure drops; are adaptable to a wide range of conditions such as temperature, altitude, and humidity; and do not require separate cooling systems.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air8.pdf

Monday, April 4, 2011

Remove Condensate with Minimal Air Loss

Removing condensate is important for maintaining the appropriate air quality level required by end uses. However, significant compressed air (and energy) losses can occur if condensate removal is done improperly.
Excess compressed air loss during condensate removal can occur due to several factors. Following shows several condensate removal methods and the characteristics of each method.

Manual operation:
  • Operators manually open valves to discharge condensate.
  • Depends on people opening valves at the appropriate time for the necessary amount of time.
  • Often leads to excess loss because air escapes when the valves are left open to drain the condensate.
Level-operated mechanical float traps:
  • Use a float connected by linkage to a drain valve that opens when an upper setting is reached and closes when the drain is emptied.
  • Require considerable maintenance.
  • Are prone to blockage from sediment in condensate.
  • Are prone to getting stuck in open position (leak excess air) and in the closed position (does not allow condensate to be drained).
  • Inverted bucket traps may require less maintenance, but will waste air if the condensate rate is inadequate to maintain the liquid level in the trap.
  • Most suited for a fully-attended powerhouse operation with scheduled maintenance.
Solenoid-operated drain valves:
  • Have timing devices that can be set to open for specified amounts of time at pre-set adjustable intervals.
  • The period during which the valve is open may not be long enough for adequate drainage of accumulated condensate.
  • The valve will operate even if little or no condensate is present, resulting in air loss.
  • Require strainers to reduce contaminants, which can block the inlet and discharge ports of these devices.
Zero-loss traps:
  • Have a float or level sensor that operates an electric solenoid or ball valve to maintain the condensate level in the reservoir below the high level point, or a float activates a pneumatic signal to an air cylinder to open a ball valve through a linkage to expel the condensate in the reservoir to the low level point.
  • Wastes no air.
  • Considered very reliable.
  • Reservoir needs to be drained often to prevent the accumulation of contaminants.
Other Points to Consider

Drain the condensate often and in smaller quantities rather than less frequently and in larger quantities. Consider oversized condensate treatment equipment to handle unexpected lubricant loading and to reduce maintenance. All drain traps should be inspected periodically, with parts repaired or replaced as required. If replacement is the decision, consider using zero loss drain traps.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air13.pdf

Thursday, March 31, 2011

Preventive Maintenance Strategies for Compressed Air Systems

A brewery neglected to perform routine maintenance on its compressed air system for years. As a result, two of its centrifugal compressors, whose impellers had been rubbing against their shrouds, were unable to deliver the volume of air they were rated for and one of those units had burned up several motors during its lifetime. In addition, plant personnel did not inspect the system’s condensate traps regularly. These traps were of a type that clogged easily, which prevented the removal of moisture and affected product quality. Also, the condensate drains were set to operate under the highest humidity conditions, so they would actuate frequently, which increased the system’s air demand. As a result, energy use was excessively high, equipment repair and replacement costs were incurred unnecessarily, and product quality suffered. All of this could have been avoided through regular maintenance.

Like all electro-mechanical equipment, industrial compressed air systems require periodic maintenance to operate at peak efficiency and minimize unscheduled downtime. Inadequate maintenance can increase energy consumption via lower compression efficiency, air leakage, or pressure variability. It also can lead to high operating temperatures, poor moisture control, excessive contamination, and unsafe working environments. Most issues are minor and can be corrected with simple adjustments, cleaning, part replacement, or elimination of adverse conditions. Compressed air system maintenance is similar to that performed on cars; filters and fluids are replaced, cooling water is inspected, belts are adjusted, and leaks are identified and repaired.

A good example of excess costs from inadequate maintenance can be seen with pipeline filter elements. Dirty filters increase pressure drop, which decreases the efficiency of a compressor. For example, a compressed air system that is served by a 100-horsepower (hp) compressor operating continuously at a cost of $0.08/kilowatt-hour (kWh) has annual energy costs of $63,232. With a dirty coalescing filter (not changed at regular intervals), the pressure drop across the filter could increase to as much as 6 pounds per square inch (psi), vs. 2 psi when clean, resulting in a need for increased system pressure. The pressure drop of 4 psi above the normal drop of 2 psi accounts for 2% of the system’s annual compressed air energy costs, or $1,265 per year. A pressure differential gauge is recommended to monitor the condition of compressor inlet filters. A rule of thumb is that a pressure drop of 2 psi will reduce the capacity by 1%.

All components in a compressed air system should be maintained in accordance with the manufacturers’ specifications. Manufacturers provide inspection, maintenance, and service schedules that should be strictly followed. Because the manufacturer-specified intervals are intended primarily to protect the equipment rather than optimize system efficiency, in many cases, it is advisable to perform maintenance on compressed air equipment more frequently.

One way to tell if a compressed air system is well maintained and operating efficiently is to periodically baseline its power consumption, pressure, airfl ow, and temperature. If power use for a given pressure and flow rate increases, the system’s efficiency is declining. Baselining the system will also indicate whether the compressor is operating at full capacity, and if that capacity is decreasing over time. On new systems, specifications should be recorded when the system is fi rst installed and is operating properly.

Types of Maintenance

Maintaining an air compressor system requires caring for the equipment, paying attention to changes and trends, and responding promptly to maintain operating reliability and effi ciency. To assure the maximum performance and service life of your compressor, a routine maintenance schedule should be developed. Time frames may need to be shortened in harsher environments. Proper maintenance requires daily, weekly, monthly, quarterly, semi-annual, and annual procedures. Please refer to the Compressed Air System Best Practices Manual for the types of procedures that are relevant to the compressors and components in your system. Excellent maintenance is the key to good reliability of a compressed air system; reduced energy costs are an important and measurable by-product. The benefi ts of good maintenance far outweigh the costs and efforts involved. Good maintenance can save time, reduce operating costs, and improve plant manufacturing efficiency and product quality.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air6.pdf

Tuesday, March 29, 2011

Maintaining System Air Quality

"Maintaining the proper air quality level is essential for keeping compressed air energy costs down and to ensure reliable production."

Poor air quality can have a negative effect on production equipment and can increase energy consumption and maintenance needs. The quality of air produced should be guided by the quality required by the end-use equipment. The air quality level is a function of the levels of particulate, moisture, and lubricant contaminants that the end uses can tolerate. Such air quality levels should be determined before deciding whether the air needs additional treatment. Compressed air should be treated appropriately but not more than is required for the end-use application. The higher the quality, the more the air usually costs to produce (in terms of initial capital investment in equipment, energy consumption and maintenance).

Once the true end-use air quality requirements have been determined, the proper air treatment equipment can be configured. Separators, filters, dryers and condensate drains are used to improve compressed air quality. Treatment equipment maintenance is critically important for sustaining the desired air quality levels.

Grouping Equipment with Similar Air Quality Requirements
One strategy to improve air quality is to group end uses having similar air quality requirements in reasonably close proximity and install the appropriate air treatment equipment to serve these end uses with a minimum of distribution piping. Some-times, grouping similar requirements of best quality air together is not always practical; if the requirement for this class is sufficiently high (70% or more of total), consider supplying the entire plant with this air quality level. If practical, separation of groups of end uses requiring similar pressure and air quality also allows some compressors and air treatment equipment to be located close to the end uses.

Filtration
Through proper filtration, appropriate air quality levels can be achieved. Because some end uses may require a higher level of air quality than others, it may not be necessary to have the entire airflow filtered to the highest level of air quality. Filters cause pressure drop that increases as the elements become fouled. Filters should be rated for the maximum anticipated operating pressure, but should be sized for the maximum anticipated rate of flow at the anticipated minimum operating pressure. The three types of compressed air filters (particulate, coalescing, and adsorption) have different functions and must be selected for the appropriate application.

Dryers
Compressed air dryers can be very effective at removing condensate from compressed air. Dryers are of three types: deliquescent, refrigerated, and desiccant. Deliquescent dryers provide a Pressure Dew Point (PDP) of 20°F lower than the dew point of the air entering them. Refrigerated dryers provide a PDP of between 35°F and 38°F and desiccant dryers can provide a PDP as low as -100°F. Dryers should be sized for the maximum anticipated rate of fl ow and must be matched to the air quality requirements. Overdrying wastes energy.

Separators
Moisture separators and condensate traps are used to remove condensate from the air stream. Because the fi rst step in condensate removal is to separate it from the air stream, moisture separators should follow each intercooler and aftercooler.

Condensate Traps
There are four main types of condensate drains: manual, level-operated mechanical (fl oat) traps, electrically-operated solenoid valves and zero-loss traps with reservoirs. Traps should allow removal of condensate, but not compressed air, and should not be left open.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air12.pdf

Monday, March 28, 2011

Engineer End Uses for Maximum Efficiency

Compressed air is one of the most important utility requirements of many industrial manufacturing plants because it directly serves processes and applications such as pneumatic tools, pneumatic controls, compressed air operated cylinders for machine actuation, product cleansing and blow-off applications. Ensuring an appropriate, stable pressure level at the end-use applications is critical to the performance of any industrial compressed air system. End uses that are engineered for maximum efficiency can help provide the consistent supply of compressed air that ensures reliable production.

To ensure the efficiency of compressed air end-use applications, a number of steps should be taken:
  1. Review the pressure level requirements of the end-use applications. Those pressure level requirements should determine the system pressure level. Because there is often a substantial difference in air consumption and pressure levels required by similar tools available from different manufacturers, request exact figures from each manufacturer for the specific application. Do not confuse maximum allowable with required pressure.
  2. Monitor the air pressure at the inlet to the tool. Improperly-sized hoses, fittings and quick disconnects often result in large pressure drops. These drops require higher system pressures to compensate, thus wasting energy. Reduced inlet pressure at the tool reduces the output from the tool and, in some cases, may require a larger tool for the specified speed and torque.
  3. Avoid the operation of any air tool at “free speed” with no load. Operating a tool this way will consume more air than a tool that has the load applied.
  4. Check the useful life of each end-use application. A worn tool will often require higher pressure, consume excess compressed air, and can affect other operations in the immediate area.
  5. Air tools should be lubricated as specified by the manufacturer, and the air going to all end uses should be free of condensate to maximize tool life and effectiveness.
  6. End uses having similar air requirements of pressure and air quality may be grouped in reason-ably close proximity, allowing a minimum of distribution piping, air treatment, and controls.
  7. Investigate and, if possible, reduce the highest point-of-use pressure requirements. Then, adjust the system pressure.
  8. Investigate and replace inefficient end uses such as open blowing with efficient ones such as vortex nozzles.
Case Study: A New Compressed Air Application is Configured for Maximum Efficiency
A large, custom printing company installed a more technologically-advanced printing machine that could increase the output of its existing units. However, the initial configuration of the new printing machine more than doubled the compressed air demand of the entire site. After a thorough review, the plant personnel realized that it would be more cost-effective for the new machines to be redesigned to consume less air at lower pressures than to increase compressor capacity at all of the company’s printing plants. Once the printing machines were reconfigured, the total air demand per printing machine was reduced from 27 standard cubic feet per minute (scfm) to 4.5 scfm and the need for 100 pounds per square inch gauge (psig) compressed air was eliminated, resulting in substantial avoided costs in energy and capital expenditures.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air10.pdf

Friday, March 25, 2011

Eliminate Inappropriate Uses of Compressed Air

Compressed air generation is one of the most expensive utilities in an industrial facility. When used wisely, compressed air can provide a safe and reliable source of power to key industrial processes. Users should always consider other cost-effective forms of power to accomplish the required tasks and eliminate unproductive demands. Inappropriate uses of compressed air include any application that can be done more effectively or more efficiently by a method other than compressed air. The table below provides some uses of compressed air that may be inappropriate and suggests alternative ways to perform these tasks.

Potentially Inappropriate Uses could be replaced by following suggested alternatives:
  • Clean-up, Drying, Process cooling: Low-pressure blowers, electric fans, brooms, nozzles
  • Sparging: Low-pressure blowers and mixers
  • Aspirating, Atomizing: Low-pressure blowers
  • Padding: Low to medium-pressure blowers
  • Vacuum generator: Dedicated vacuum pump or central vacuum system
  • Personnel cooling: Electric fans
  • Open-tube, compressed air-operated vortex coolers without thermostats: Air-to-air heat exchanger or air conditioner, add thermostats to vortex cooler
  • Air motor-driven mixer: Electric motor-driven mixer
  • Air-operated diaphragm pumps: Proper regulator and speed control; electric pump
  • Idle equipment (Equipment that is temporarily not in use during the production cycle.): Put an air-stop valve at the compressed air inlet
  • Abandoned equipment (Equipment that is no longer in use either due to a process change or malfunction.): Disconnect air supply to equipment
Example
The table below shows inappropriate uses of compressed air in an automobile assembly plant. The plant took several action steps identified in the table to eliminate or reduce these inappropriate uses. Peak flow is identified in cubic feet per minute (cfm).


The plant audit showed that the energy used to generate the compressed air averages 18 kW/100 cfm. The aggregate electric rate at the plant is $0.05 per kWh.

Annual savings = [kW per cfm] x [cfm savings] x [# of hours] x [$ per kWh]


= 18/100 x [(150 x 6,500) + (1,000 x 5,000) + (800 x 3,500)
+ (750 x 3,500)] x $0.05
= $102,600

Net savings:
Calculate electric energy costs for the motor-driven vacuum pump, fans, and actuators, and subtract these costs from the annual savings calculated to determine the net savings. Note that there will be a one-time cost of installation for the added equipment.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air2.pdf

Wednesday, March 23, 2011

Effect of Intake Air on Compressor Performance

The effect of intake air on compressor performance should not be underestimated. Intake air that is contaminated or hot can impair compressor performance and result in excess energy and maintenance costs. If moisture, dust, or other contaminants are present in the intake air, such contaminants can build up on the internal components of the compressor, such as valves, impellers, rotors, and vanes. Such build-up can cause premature wear and reduce compressor capacity.

"When inlet air is cooler, it is also denser. As a result, mass flow and pressure capability increase with decreasing intake air temperatures, particularly in centrifugal compressors."

This mass flow increase effect is less pronounced for lubricant-injected, rotary-screw compressors because the incoming air mixes with the higher temperature lubricant. Conversely, as the temperature of intake air increases, the air density decreases and mass flow and pressure capability decrease. The resulting reduction in capacity is often addressed by operating additional compressors, thus increasing energy consumption.

To prevent adverse effects from intake air quality, it is important to ensure that the location of the entry to the inlet pipe is as free as possible from ambient contami-nants, such as rain, dirt, and discharge from a cooling tower. If the air is drawn from a remote location, the inlet pipe size should be increased in accordance with the manufacturer’s recommendation to prevent pressure drop and reduction of mass flow. All intake air should be adequately filtered. A pressure gauge indicating pressure drop in inches of water is essential to maintain optimum compressor performance.

When an intake air filter is located at the compressor, the ambient temperature should be kept to a minimum, to prevent reduction in mass flow. This can be accomplished by locating the inlet pipe outside the room or building. When the intake air filter is located outside the building, and particularly on a roof, ambient considerations are important, but may be less important than accessibility for maintenance in inclement or winter conditions.

How to Select an Intake Air Filter
A compressor intake air filter should be installed in, or have air brought to it from a clean, cool location. The compressor manufacturer normally supplies, or recom-mends, a specific grade of intake filter designed to protect the compressor. The better the filtration at the compressor inlet, the lower the maintenance at the compressor. However, the pressure drop across the intake air filter should be kept to a minimum (by size and by maintenance) to prevent a throttling effect and a reduction in compressor capacity. A pressure differential gauge is one of the best tools to monitor the condition of the inlet filter. The pressure drop across a new inlet filter should not exceed 3 pounds per square inch (psi).

Inlet Filter Replacement
As a compressor intake air filter becomes dirty, the pressure drop across it increases, reducing the pressure at the air end inlet and increasing the compression ratios. The cost of this loss of air can be much greater than the cost of a replacement inlet fi lter, even over a short period of time. For a 200 horsepower (hp) compressor operating two shifts, 5 days a week (4,160 hours per year) with a $0.05/kilowatt hour (kWh)
electricity rate, a dirty intake filter can decrease compressor efficiency by 1%–3%, which can translate into higher compressed air energy costs of between $327 and $980 per year.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air14.pdf

Monday, March 21, 2011

Determining the Right Air Quality for Your Compressed Air System

Knowing the proper air quality level required for successful production is an important factor in containing compressed air energy and other operating costs, because higher quality air is more expensive to produce. Higher quality air requires additional air treatment equipment, which increases capital costs as well as energy consumption and maintenance needs. The quality of air produced should be guided by the degree of dryness and filtration needed and by the minimum acceptable contaminant level to the end uses.

Level of Air Quality: Plant Air
Applications: Air tools, general plant air

Level of Air Quality: Instrument Air
Applications: Laboratories, paint spraying, powder coating, climate control

Level of Air Quality: Process Air
Applications: Food and pharmaceutical process air, electronics

Level of Air Quality: Breathing Air 
Applications: Hospital air systems, diving tank refill stations, respirators for cleaning and/or grit blasting

Compressed Air Contaminants
Compressed air contaminants can be in the form of solids, liquids, or vapors. Contaminants can enter a compressed air system at the compressor intake, or can be introduced into the air stream by the system itself.

Air quality class is determined by the maximum particle size, pressure dewpoint, and maximum oil content allowed. For more information, see ISO 8573-1 Compressed Air Quality Classes in the Compressed Air System Best Practices Manual. (See references in sidebar).

One of the main factors in determining air quality is whether lubricant-free air is required. Lubricant-free air can be produced either by using lubricant-free compressors, or with lubricant-injected compressors and additional air treatment equipment. The following factors can help one decide whether lubricant-free or lubricant-injected air is appropriate:
  • If only one end use requires lubricant-free air, only the air supply to it should be treated to obtain the necessary air quality. Alternatively, it may be supplied by its own lubricant-free compressor. If the end uses in a plant require different levels of air quality, it may be advisable to divide the plant into different sections so that air treatment equipment that produces higher quality air is dedicated to the end uses that require the higher level of compressed air purification.
  • Lubricant-free rotary screw and reciprocating compressors usually have higher initial costs, lower efficiency, and higher maintenance costs than lubricant-injected compressors. However, the additional separation, filtration, and drying equipment required by lubricant-injected compressors will generally cause some reduction in system efficiency, particularly if the system is not properly maintained.
Careful consideration should be given to the specifi c end use for the lubricant-free air, including the risks and costs associated with product contamination before selecting a lubricant-free or lubricant-injected compressor. Centrifugal compressors also offer an alternative for plants whose end uses require lubricant-free air.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air5.pdf

Friday, March 18, 2011

Determine the Cost of Compressed Air for Your Plant

Most industrial facilities need some form of compressed air, whether for running a simple air tool or for more complicated tasks such as the operation of pneumatic controls. A recent survey by the U.S. Department of Energy showed that for a typical industrial facility, approximately 10% of the electricity consumed is for generating compressed air. For some facilities, compressed air generation may account for 30% or more of the electricity consumed. Compressed air is an on-site generated utility. Very often, the cost of generation is not known; however, some companies use a value of 18-30 cents per 1,000 cubic feet of air.

Compressed air is one of the most expensive sources of energy in a plant. The over-all efficiency of a typical compressed air system can be as low as 10%-15%. For example, to operate a 1-horsepower (hp) air motor at 100 pounds per square inchgauge (psig), approximately 7-8 hp of electrical power is supplied to the air compressor. To calculate the cost of compressed air in your facility, use the formula shown below:

Where:
bhp: Motor full-load horsepower (frequently higher than the motor nameplate horsepower—check equipment specification)
0.746: conversion between hp and kW
Percent time: percentage of time running at this operating level
Percent full-load bhp: bhp as percentage of full-load bhp at this operating level
Motor efficiency: motor efficiency at this operating level

Example
A typical manufacturing facility has a 200-hp compressor (which requires 215 bhp) that operates for 6800 hours annually. It is fully loaded 85% of the time (motor efficiency = .95) and unloaded the rest of the time (25% full-load bhp and motor efficiency = .90). The aggregate electric rate is $0.05/kWh.

Cost when fully loaded =


Cost when fully unloaded =



Annual energy cost = $48,792 + $2,272 = $51,064

Typical Lifetime Compressed Air Costs in Perspective—Costs Over 10 Years
Assumptions in this example include a 75-hp compressor operated two shifts a day, 5 days a week at an aggregate electric rate of $0.05/kWh over 10 years of equipment life.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air1.pdf

Wednesday, March 16, 2011

Compressed Air System Control Strategies

Improving and maintaining compressed air system performance requires not only addressing individual components, but also analyzing both the supply and demand sides of the system and how they interact, especially during periods of peak demand. This practice is often referred to as taking a systems approach because the focus is shifted away from components to total system performance.

Matching Supply with Demand
With compressed air systems, system dynamics (changes in demand over time) are especially important. Using controls, storage, and demand management to effectively design a system that meets peak requirements but also operates efficiently at part-load is key to a high performance compressed air system. In many systems, compressor controls are not coordinated to meet the demand requirements, which can result in compressors operating in conflict with each other, short-cycling, or blowing off—all signs of inefficient system operation.

Individual Compressor Controls
Over the years, compressor manufacturers have developed a number of different types of control strategies. Controls such as start/stop and load/unload respond to reductions in air demand by turning the compressor off or unloading it so that it does not deliver air for periods of time. Modulating inlet and multi-step controls allow the compressor to operate at part-load and deliver a reduced amount of air during periods of reduced demand. Variable speed controls reduce the speed of the compressor in low demand periods. Compressors running at part-load are generally less efficient than when they are run at full-load.

Multiple Compressor Controls
Systems with multiple compressors should use more sophisticated controls to orchestrate compressor operation and air delivery to the system. Network controls use the on-board compressor controls’ microprocessors linked together to form a chain of communication that makes decisions to stop/start, load/unload, modulate, and vary displacement and speed. Usually, one compressor assumes the lead role with the others being subordinate to the commands from this compressor. System master controls coordinate all of the functions necessary to optimize compressed air as a utility. System master controls have many functional capabilities, including the ability to monitor and control all components in the system, as well as trending data, to enhance maintenance functions and minimize costs of operation. Most multiple compressor controls operate the appropriate number of compressors at full-load and have one compressor trimming (running at part-load) to match supply with demand.

Pressure/Flow Controllers
Pressure/Flow Controllers (P/FC) are system pressure controls that can be used in conjunction with the individual and multiple compressor controls described above. A P/FC does not directly control a compressor and is generally not part of a compressor package. A P/FC is a device that serves to separate the supply side of a compressor system from the demand side, and requires the use of storage. Controlled storage can be used to address intermittent loads, which can affect system pressure and reliability. The goal is to deliver compressed air at the lowest stable pressure to the main plant distribution system and to support transient events as much as possible with stored compressed air. In general, a highly variable demand load will require a more sophisticated control strategy to maintain stable system pressure than a consistent, steady demand load.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air7.pdf

Monday, March 14, 2011

Compressed Air Storage Strategies

Compressed air storage can allow a compressed air system to meet its peak demand needs and help control system pressure without starting additional compressors. The appropriate type and quantity of air storage depends on air demand patterns, air quantity and quality required, and the compressor and type of controls being used. An optimal air storage strategy will enable a compressed air system to provide enough air to satisfy temporary air demand events while minimizing compressor use and pressure.

The use of air receivers is especially effective for systems with shifting air demand patterns. When air demand patterns are variable, a large air receiver can provide enough stored air so that a system can be served by a small compressor and can allow the capacity control system to operate more effectively. For systems having a compressor operating in modulation to support intermittent demand events, storage may allow such a compressor to be turned off. By preventing pressure decay due to demand events, storage can protect critical end-use applications and prevent addi-tional units from coming online.

Air entering a storage receiver needs to be at a higher pressure level than the system pressure. A good air storage strategy will allow the differential between these two pressure levels to be sustained. To accomplish such a pressure differential, two types of devices can be employed: Pressure/Flow Controllers (P/FC) and metering valves.

A P/FC is a device that serves to separate the supply side of a compressed air system from the demand side. In a system that employs P/FCs, the compressors generally operate at or near design discharge pressure to ensure that the P/FC receives air at a higher pressure level than it will discharge into the system. This allows the pressure in the demand side to be reduced to a stable level that minimizes actual compressed air consumption. P/FCs are added after the primary receiver to maintain a reduced and relatively constant system pressure at points of use, while allowing the compressor controls to function in the most efficient control mode and discharge pressure range. Properly applied, a P/FC can yield significant energy savings in a system with a variable demand load. See Figure 1.


For situations in which just one or a few applications have intermittent air demand, a correctly-sized storage receiver close to the point of the intermittent demand with a check valve and a metering valve can be an effective and lower cost alternative. For this type of storage strategy, a check valve and a tapered plug or needle valve are installed upstream of the receiver. The check valve will maintain receiver pressure at the maximum system pressure; the plug or needle valve will meter the flow of compressed air to “slow fill” the receiver during the interval between demand events. This will have the effect of reducing the large intermittent requirement into a much smaller average demand. See Figure 2.


Sunday, March 13, 2011

Alternative Strategies for Low-Pressure End Uses

Compressed air is expensive to produce. Because compressed air is also clean, readily available, and simple to use, it is often chosen for applications in which other methods or sources of air are more economical. To reduce compressed air energy costs, alternative methods of supplying low-pressure end uses should be considered before using compressed air in such applications. Many alternative methods of supplying low-pressure end uses can allow a plant to achieve its production requirements effectively.

Before deciding to replace a low-pressure end use with an alternative source, it is important to determine the minimum practical pressure level required for the application.

Alternative Applications to Low-Pressure End Uses

Existing Low-Pressure End Use: Open blowing, mixing
Potential Alternatives: Fans, blower, mixers, nozzles
Reasoning: Open-blowing applications waste compressed air. For existing open-blowing applications, high efficiency nozzles could be applied, or if high-pressure air isn’t needed, consider a blower or a fan. Mechanical methods of mixing typically use less energy than compressed air.

Existing Low-Pressure End Use: Personnel cooling
Potential Alternatives: Fans, air conditioning
Reasoning: Using compressed air for personnel cooling is not only expen-sive, but can also be hazardous. Additional fans or an HVAC upgrade should be considered instead.

Existing Low-Pressure End Use: Parts cleaning
Potential Alternatives: Brushes, blowers, vacuum pumps
Reasoning: Low-pressure blowers, electric fans, brooms, and high-efficiency nozzles are more efficient for parts cleaning than using compressed air to accomplish such tasks.

Existing Low-Pressure End Use: Air motors and air pumps
Potential Alternatives: Electric motors, mechanical pumps
Reasoning: The tasks performed by air motors can usually be done more efficiently by an electric motor except in hazardous environ-ments. Similarly, mechanical pumps are more efficient than air-operated double diaphragm pumps. However, in an explosive atmosphere and/or the pumping of abrasive slurries, the application of a double diaphragm pump with appropriate pressure regulating and air shut-off controls may be appropriate.

Case Study: Low-Pressure End Uses are Replaced with Alternative Applications

A bottling plant was using compressed air in some applications that could be better supported with less energy-intensive methods. The plant was cooling and hardening bottlenecks by blowing cool, compressed air on them. Also, some of the blow mold machines were continuously blowing compressed air through air jets onto the pre-form feed lines to prevent them from jamming. Lastly, the plant’s stackers in the packaging area were using compressed air-operated venturi vacuum producers to pick up and position dividers between layers of bottles. To cool the bottlenecks, the application of a small blower that would blow cool air from chilled water was recommended. The installation of an electromechanical vibrator was identified as the best way to prevent the feed lines from jamming. Finally, a central vacuum system having energy costs that were 30% lower than that of the venturi devices was shown to be as effective as the existing system. The annual compressed air energy savings from implementing these simple modifications was $80,000.

Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air11.pdf

Saturday, March 5, 2011

How An Air Compressor Works

There are many things that you might want to know about how an air compressor works.

Compressed Air Operations ManualYou will be able to find many interesting pieces of information out about the air compressors, and you should be able to know how they work. This is a very important factor in the overall impression of the air compressors.

First of all, the air compressors are going to harness the wind at an amazing rate. This is something that many people have wanted to do because air is something that is very useful. The wind can show us that. There is nothing like being able to sit down on a windy day and know that you are going to be able to get the most out of your air compressors. However, you have to understand how they work, first of all.

There are many different types of air compressors. Some are used in building and creating, and some are used in order to convert air to things that we can use, like breathable gas. Most of the time they work in the same way.

They work through using a chamber. The chamber is pressurized, and this pressure is what leads to the harnessing of the air. The air is harnessed through the pressure. This is often hard to comprehend. However, if you think about the way that it works, it is very simple. The air is pulled in through an opening which it cannot exit from. The air enters a chamber and more and more air is pulled in. it is not simply allowed to fill, but more air is pulled in than there is room for. The air compressor continues to pull in more and more air so that it is very tight. Then, the air is compressed even further. After this process is done, the air compressor is full.

Because the way that the chambers inside of the machine work, and because of the very small nozzles, the air is forced out with great speed when it is finally released. This means that the air compressors can be hooked up to anything and then the air can be used. The air compressors themselves simply gather the air into them and then press the air very tightly. The machines are able to do this through pressure. Once the air has been held tightly, it can be released and can be very powerful. It is the release of this air that is what causes it to be used. The air is pushed out of the nozzles at a great speed. However it is pushed out at a very controlled speed. You have complete control over the air.

You can use the air compressors for many things. One of the things that it is used for is to hook up to a nail gun. This helps to drive the nails into the wall at a much faster and stronger pace than a hammer. You can build something much faster this way and it is going to be much easier for you to use. This is a very popular use for the air compressor because it is going to allow you to be sure that you have made the most out of the air. It can also be used in things like power washing. Here, it is hooked up to spray washers or other items and when the air is released, the washers will do their job much better. This way, the air works to propel the water and it can get done much faster. There are also air compressors that aide people. For instance, one of the most popular types of air compressors is the kind that converts the gasses into breathable air so that a person can go diving and still be able to breathe. This is a very popular type of air compressors and it works in the same way. These are very different from the main types of air compressors though. With these, the air is not released in the same way, and it is not sent out in such a hurry. With the other types of air compressors, it is.

Yet you have to be very careful with the air compressors. You should be sure to only use the air compressor for what it is intended. Doing something else with the air compressor, no matter how it benefits you and what you want to accomplish, is going to be bad for the air compressor. You want to be sure that you are able to use this for years and years, so be absolutely sure that you are only using it for what it is meant to be used.

Published At: Isnare.com Free Articles Directory - http://www.isnare.com/

Wednesday, February 23, 2011

Compressed Air Leaking? Is It The Valve Or Is It The Cylinder?

"Reducing air leaks in your plant can save thousands of dollars annually. "
Compressed air is one of the most costly forms of energy you can use in your plant, of course, it's one of the most versatile, fast and strong too.

When it's "quiet time" in the plant, wander around the machinery and listen. You will often hear the gentle (or perhaps not so gentle) hissing of air escaping from the exhaust port of your air valves.

The sound of compressed air "chewing up your dollars" as it wafts to atmosphere can be muted if your air valves have mufflers in the exhaust ports, but nevertheless, it can be heard.

Also, there are commercially available ultra-sonic compressed air leak detectors on the market. If your plant doesn't have a "quiet time", which would enable you to actually hear the leaks yourself, investing in an ultrasonic leak detector can bring substantial payback in energy savings.

Usually you'll have one air valve connected to one air cylinder. Usually that cylinder will be double acting - which means that it will have two air lines running to it, and as the air valve shifts back and forth, air will alternatively flow to the cylinder through one line or the other. When it's flowing into one line to the cylinder, the other line is allowing the air at the other end of the cylinder to flow through the valve to exhaust.

While an air valve and cylinder are doing work of course there will be air being exhausted continuously from the air valve exhaust ports.

It's when the machine is down, when it's doing no useful - and hopefully money generating work for you - that air should not be escaping through the valve exhaust ports. At this point that loss of compressed air is just that; loss - of profits - of money.

Inside, the two ends of the cylinder are separated by a piston. The piston is what drives the rod out and back as the cylinder cycles.

Around that piston will be an air seal that "crunches" between the side of the piston and the inside of the cylinder barrel, effectively stopping air from flowing by (bypassing) the piston.

In time that seal will wear, and air will start bypassing into the other side. This means that this air now has an open path from the supply side down the other air line to the valve, and thence to the exhaust port. And a gentle (or not so gentle) hiss occurs as your compressed air dollars exhaust to atmosphere.

Or....inside your air valve there is, too, a series of seals that normally prevent air from getting from the air supply side into the exhaust side of the valve, and then out the exhaust port. And that air, as it gently (or not so....etc. ) is pouring your compressed air dollars from the plant air supply.

So, which is it that's leaking; the seal around the piston in the cylinder, or the seal inside the valve that stops the incoming air from getting across to the exhaust port without going up to the cylinder?

Have a look at the cylinder. If the rod is out, air will be entering the air port at the rear of the cylinder. If the cylinder is in - retracted, the air will be coming into the cylinder at the rod end.

Take the air line that is charged, that is, the air line that is supplying air to the cylinder, and crimp it. Many air lines are made of polyethylene or polypropylene, and it's quite easy to make a bit of a bend in the air line, effectively shutting off air to the cylinder.

Listen at the valve. If the air has stopped escaping the valve's exhaust port, then it's the seal in the cylinder that's at fault.

If, after ensuring that the air to the cylinder is completely stopped, air continues to exhaust from the exhaust port of the valve, then it's the seal inside the air valve that's at fault.

Regardless of which is the culprit, the air valve or the cylinder, get it fixed....fast! Compressed air costs a bundle. You don't want to waste it.

Published At: Isnare.com Free Articles Directory - http://www.isnare.com/

Wednesday, February 2, 2011

Minimize Compressed Air Leaks

Leaks are a significant source of wasted energy in a compressed air system, often wasting as much as 20%-30% of the compressor’s output. Compressed air leaks can also contribute to problems with system operations, including:
  • Fluctuating system pressure, which can cause air tools and other air-operated equipment to function less efficiently, possibly affecting production
  • Excess compressor capacity, resulting in higher than necessary costs
  • Decreased service life and increased maintenance of supply equipment (includ-ing the compressor package) due to unnecessary cycling and increased run time.
Although leaks can occur in any part of the system, the most common problem areas are couplings, hoses, tubes, fittings, pipe joints, quick disconnects, FRLs (filter, regulator, and lubricator), condensate traps, valves, flanges, packings, thread seal-ants, and point-of-use devices. Leakage rates are a function of the supply pressure in an uncontrolled system and increase with higher system pressures. Leakage rates identified in cubic feet per minute (cfm) are also proportional to the square of the orifice diameter.

Leak Detection
The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize high frequency hissing sounds associated with air leaks. These portable units are very easy to use. Costs and sensitivities vary, so test before you buy. A simpler method is to apply soapy water with a paintbrush to suspect areas. Although reliable, this method can be time consuming and messy.

Example
A chemical plant undertook a leak-prevention program following a compressed air audit at their facility. Leaks, approximately equivalent to different orifice sizes, werefound as follows: 100 leaks of 1/32” at 90 pounds per square inch gauge (psig), 50 leaks of 1/16” at 90 psig, and 10 leaks of 1/4” at 100 psig. Calculate the annual cost savings if these leaks were eliminated. Assume 7,000 annual operating hours, an aggregate electric rate of $0.05 kilowatt-hour (kWh), and compressed air generation requirement of approximately 18 kilowatts (kW)/100 cfm.

Cost savings = # of leaks x leakage rate (cfm) x kW/cfm x # of hours x $/kWh

Using values of the leakage rates from the above table and assuming sharp-edged orifices:

Cost savings from 1/32” leaks = 100 x 1.46 x 0.61 x 0.18 x 7,000 x 0.05 = $5,611
Cost savings from 1/16” leaks = 50 x 5.72 x 0.61 x 0.18 x 7,000 x 0.05 = $10,991
Cost savings from 1/4” leaks = 10 x 100.9 x 0.61 x 0.18 x 7,000 x 0.05 = $38,776
Total cost savings from eliminating these leaks = $57,069

Note that the savings from the elimination of just 10 leaks of 1/4” account for almost 70% of the overall savings. As leaks are identified, it is important to prioritize them and fix the largest ones first.


Suggested Actions
  • Fixing leaks once is not enough. Incorporate a leak prevention program into operations at your facility. It should include identi-fication and tagging, tracking, repair, verification, and employee involvement. Set a reasonable target for cost-effective leak reduction—5%-10% of total system flow is typical for industrial facilities.
  • Once leaks are repaired, reevaluate your compressed air system supply. Work with a compressed air systems specialist to adjust compressor controls. To maximize energy savings, compressor run time must be reduced to match the reduced demand.
Source: http://www1.eere.energy.gov/industry/bestpractices/pdfs/compressed_air3.pdf

    Sunday, January 2, 2011

    11 Tips for Air Compressor Maintenance

    Now that you've invested in an air compressor to run all of your air tools you're going to have to learn how to keep it up and running. Because the standard handyman's air compressors don't typically require daily upkeep, it's easy to forget about them and neglect their upkeep. This can be a costly oversight so it's vital for you to keep an eye on the following maintenance tips.

    Maintenance Tip 1: Read and Follow Your Air Compressor's Manual

    Nothing stops an air compressor faster than an owner who doesn't read the owner's manual. 
    There's going to be some simple tips in there for you that will help you to get a nice long life out of your air compressor - simple stuff for you to do that you would never have thought to do unless you read it. Plus, if you don't follow the rules in your air compressor manual there's a chance that you'll void your warranty. That in itself should be enough of an incentive to read the "flipping" manual.

    Maintenance Tip 2: Drain The Moisture From The Tanks

    Reciprocating Compressors:: Operation and MaintenanceThe receiver tank collects moisture from the air that it's compressing - especially if you live in a humid climate. Most tanks have a valve for draining this moisture that accumulates and it's up to you to make sure that these are drained regularly. Before draining the water you should be sure to release the air pressure from the tanks.

    Maintenance Tip 3: Clean Intake Vents

    If you force your air compressor to work too hard to intake air you're losing power on your compression. This will gradually degrade the quality of your tool. Be sure to keep your intake vent as clean as possible and check them regularly especially if you're working in a dusty or dirty environment.

    Maintenance Tip 4: Tighten All Fasteners

    Your air compressor's a running, vibrating engine and it will loosen its screws, nuts and bolts on a regular basis. Be sure to check these periodically and tighten them up if you find any that have jiggled loose.

    Maintenance Tip 5: Check Hoses Regularly

    Check all your hoses periodically as they are the veins of your air compressor. If they become cracked or corroded they could soon begin to leak and then put undue strain on the rest of your compressor's components. Be sure to check them and replace them if you find them cracked or damaged.

    Maintenance Tip 6: Test the Safety Shutdown System

    Your air compressor may have a built in safety shut down. The function of this system is to shut off your compressor if it's getting too hot, or if the engine's oil pressure is too low. This test will help you ensure a longer lasting compressor.

    Maintenance Tip 7: Check and Change Air Filters As Needed

    A filthy air filter is only hurting your air compressor by allowing dirty air from the outside in, plus forcing it to work harder to intake air. Check your filters regularly and change them if you notice a heavy build up of dust and dirt. Change every six months or so if you use it infrequently.

    Maintenance Tip 8: Clean the Fuel Tank

    As with any engine you need to periodically clean out the fuel tank to ensure optimal operating conditions. You should look to clean out the engine on your air compressor once every year or so to remove any residual build up from the fuel. This will preserve the life of your engine.

    Maintenance Tip 9: Check and Change the Compressor Oil

    If you're running a compressor that uses oil you should be checking it on a daily basis to make sure that your machine is topped off. Then, every 500-1000 hours of use you should be changing this oil to ensure maximum functioning of your air compressor.

    Maintenance Tip 10: Change the Separator Element

    The separator element prevents the excessive use of oil, but it has to be replace periodically. Keep your compressor in top condition by replacing the separator element every 1,000 hours of operation.

    Maintenance Tip 11: Clean the Heat Exchangers

    If your heat exchangers are dirty then they can't do their job, which is to reduce the operating temperatures of your air compressor. Clean them regularly to keep your operating temperatures down and increase the life span of your air compressor.

    By following the tips above you'll ensure a nice long life for your air compressor, plus the jobs that you use it for will go faster and more productively. A well maintained air compressor is a wonderful machine for any job site or workshop, so keep yours running smoothly.

    Charlie Slagle and his ToolCrib team deliver discount power tool prices at ToolCrib.com! Visit http://www.ToolCrib.com for great prices on great power tools today!

    Article Source: http://EzineArticles.com/?expert=Charlie_Slagle

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