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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

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