U.S. Army

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TABLE OF CONTENTS

SECTION 1 -- COMPRESSED AIR SYSTEM OVERVIEW

Introduction
Previous System Improvements
System Load Profile and Cost Analysis
Other Issues
Plant Compressed Air Survey

SECTION 2 -- CURRENT SYSTEM REVIEW

Main Compressor Room Supply
Wind Tunnel Supply System
Building 3150 Supply System
Building 3028 Supply System
Compressor Capacity Controls
Air Treatment and Air Quality
Basic System Header/Piping and Interconnecting Piping Between the Primary Air Compressors and the System
Flow Regulation at the Process
Auto Condensate Drains
Leak Management Programs
Cabinet Coolers
Blow Offs
Vacuum Generators
Air-Operated Diaphragm Pumps
Misapplied High Pressure Air

SECTION 3 -- GAS ENGINE-DRIVEN SYSTEM ASSESSMENT

Gas Engine-Driven System Design Factors
Operating Cost Comparison
Capital Cost Assessment

ACRONYMS

acfm - actual cubic feet per minute
bhp - brake horsepower
Btu - British thermal unit
CERL - U.S. Army Construction Engineering Research Laboratory
cfm - cubic feet per minute
CO - Carbon monoxide
ESPC - Energy Savings Performance Contract(ing)
gm/bhp/hr - grams per brake horsepower per hour
HVAC - Heating, ventilating and air conditioning system
NGEDAC - Natural gas engine driven air compressor
NOx - Nitrogen Oxide
psig - pounds per square inch gauge
scfm - standard cubic feet per minute

INTRODUCTION

The compressed air system at Picatinny Arsenal encompasses an extensive geographical area. Today, there are almost 27 miles of compressed air piping, joining 15 to 16 areas of production buildings. With air usage levels significantly less than those required during the height of production at the Arsenal, there are numerous opportunities to improve energy efficiency in the system and to further reduce system operating costs by implementing a gas engine driven compressed air system.

The main compressed air system is fed by a compressor plant in the main Power House Building 506. Average flow for the main system is 925 acfm at 80 psig with the system operating 8760 hours per year. The air delivered from the Power House is dried only with a water-cooled aftercooler. When the site visit took place on a 79°F ambient day, the compressed air system was delivering 80°F saturated air at 80 psig to the system.

There are three other independent compressed air systems:

• Wind Tunnel: A special application for projectile testing at supersonic, transonic, and subsonic speeds. This system requires higher pressure (110-120 psig) and significant storage (16,000 cubic feet) for proper operation. Average flow for the Wind Tunnel system is 2,200 acfm. The system operates 500 hours per year.
  
  
• Building 3150 - Machine Shop: This building houses a large machine shop and runs with its own air compressor supply. Average flow is 20 acfm with the system operating 8760 hours per year. There is no feeder line from the main air system to this building.
  
  
• Building 3028: This building also has no feed from the main air supply and currently has its own air system. Average flow is 40 cfm with the system operating 8760 hours per year.

There are also several dedicated systems in the Main Power House: one for engine starting of the 12-cylinder Caterpillar natural gas engine generator/fuel cell power system and one for the instrument air and HVAC control systems.

There are other dedicated control and fire suppression compressed air systems throughout the Arsenal. In general, these units are small horsepower duplex units with compressed air dryers. They do not normally run many hours a year and are not part of the main air system. These are not included in the system evaluation of this report.

In summary, Picatinny Arsenal has a large volume air system that is currently supplying a relatively small system demand. This "system downsizing" presents many opportunities for energy savings that are addressed in this report.

PREVIOUS SYSTEM IMPROVEMENTS

The Arsenal personnel have already implemented several key programs that have successfully lowered the energy cost.

Power House (506). Operating personnel have lowered the final discharge pressure to the system from 100 psig to 80 psig. This has reduced electrical demand by approximately 31.69 kW resulting in savings of $24,430 per year. Today the system still runs effectively at this reduced pressure level.

Building 3150. This system previously ran a 100 hp, 490 acfm Quincy Rotary Screw Compressor with apparent demand of 40 cfm or less, running 10% loaded continuously. This was a very inefficient mode of operation and resulted in excessive wear on the compressor. The system operated at 59.4 kW with an annual energy cost of $45,790.

Today the machine shop typically runs two small 4.7 hp tank-mounted units. Ten of these units (IMC) are located strategically around the building. The operating pairs are alternated as required. These units operate at 14.21 kW. Since they are commercial as opposed to industrial units, the motors are a low-efficiency, single-phase type. Today, the operating cost of $10,923 per year results in savings of $34,867 per year.

Building 3028. This building previously ran a 40 hp/35 kW 150 cfm Ingersoll Rand ESV non-lubricated, double-acting, water-cooled, single-stage compressor. At 40 cfm demand, this unit operated at 13.2 kW for a cost of $10,175 per year.

Today, air is supplied by a 25 hp Ingersoll Rand Model 3000, delivering 100 cfm at 100 psig at 27 bhp/22.8 kW. At 40 cfm average demand, this unit operates at approximately 8.8 kW over 8760 hours or $6,791 per year operating cost, a net savings of approximately $3,384 per year.

SYSTEM LOAD PROFILE AND COST ANALYSIS

Based on optimum performance of each compressor-compared to Load Cycle-and on discussions with plant personnel, load profiles and power usage assessments were developed for each of the main compressed air systems. Supporting details are provided in "Worksheets", which is included in the Plant Survey section of this report.

Measured Flow. Flow and pressure were measured for 24 hours beginning the morning of August 29, 2000. The flow measurement was taken with a Sierra-heated wire anemometer (0-20,000 fpm ( 3%). Readings were taken every 11 seconds average. The curve shown is with these readings averaging every 10 minutes.

The trended curve shows 800 scfm (900 acfm) in a continuous demand over the 24-hour period, both during production and non-production periods. Picatinny is essentially a one-shift operation. This indicates a significant number of leaks and/or process air "left on" during non-production hours. Both of these conditions represent an energy savings opportunity (refer to the Leak Management section). Arsenal personnel are in the process of determining which production activities were operating and which weren't. This information will help determine the source and level of opportunity.

Pressure. The pressure was recorded at the same trending rates and at the same point as the flow. The pressure transducer was zeroed out against a calibrated Helcoid DP250 digital test gauge. The pressure held a steady 79 to 80 psig during the entire test.

The actual plant electrical power cost for the combination of the main system and satellite subsystems, as running today, is in excess of $130,000 per year. The load profile or demand of this system is almost like "process air" and is relatively stable during all shifts. The full load operating range is 365 days a year, 24 hours a day, 8,760 hours a year (see flow meter readings).

There are not significant cost savings within the current air supply configuration for the main Power House, except for the potential for moving to gas engine drives. Moving the sub-systems associated with Buildings 3028 and 3150 to the main system would save roughly $13,000 annually based on being to supply at an incremental cost of $80 per cfm relative to the current cost averaging $300 per cfm for the 60 cfm requirement.

OTHER ISSUES

The electrical power cost per hour per "loaded cfm" of air used was determined. Electrical power cost is used as a qualifying factor since it is "real bottom line dollars." This is an absolute number and not a subjective or opinion. All paybacks for savings projects are estimated using the "full load operating efficiencies," which are very conservative.

If the compressed air is not used, the compressor either shuts off or unloads. If it shuts off, there is a 100% percent saving of the power cost. If it unloads, there is a 25 to 90 percent savings of the power cost.

It is important to note that all recoverable compressed air costs should also be considered, i.e., maintenance, water costs, depreciation, etc. Usually, the electrical power cost is between 50 and 75 percent of the total "variable compressed air costs." Associated maintenance and other costs will be, in all probability, at least 50 percent or more of the identified electrical power cost. Existing records may be available to estimate these more accurately.

PLANT COMPRESSED AIR SURVEY

The primary objective is to understand the basic system dynamics and identify the basic load/power profile today and what it will be when optimized with this data. The objective is to size and recommend an appropriate natural gas engine driven compressor to effectively carry the base load and optimize the natural gas engine savings over conventional electric driven units. This action is to evaluate this Arsenal's operating characteristics to reflect accurate and effective results with a natural gas engine driven air compressor demonstration unit.

There were also some specific selected questions such as:

• Determine what follow-up plans and actions would be appropriate to lower the overall compressed air energy cost in the continuing short and long terms.
  
  
• Evaluate the potential energy cost savings in compressed air demand side conservation programs:

  Leak control/management

  Specific demand side requirements
  

• Review appropriateness of all compressed air equipment to produce proper quality, quantity of usable compressed air power at the acceptable efficiency.
  
  
• Identify a relatively accurate load profile.

Identify your current electric power cost per cfm and per psig in order to calculate anticipated return.

Key concepts to consider if a Level II Audit is implemented:

• Identify and target opportunities for compressed air savings in the demand side.
  
  
• Outline plans for point of use pressure and quality management.
  
  
• Evaluate characteristics and appropriateness of central compressed air control system.
  
  
• Identify savings potential in use of air saving devices-nozzles and auto drains.
  
  
• Identify savings potential in replacement or re-evaluation of "misapplied air" - cabinet coolers, vacuums, pumps, and bearing cooling.
  
  
• Review total piping system and leaks. Develop action plan to remove as much pipe as possible, then repair leaks on what is left.

Note that during the site visit, a significant air leak was identified in an above-ground, rusted-out distribution line under enclosed walkway between Building 807 and Building 810. This creates an EPA violation (oil in ground) and a significant "safety issue" (possible blowout). The audit team pointed this out to Arsenal personnel on site and at the "wrap-up" meeting and recommend this leak and any others like it be "corrected immediately."

Above-Ground Leak Needing Immediate Repair

POWER HOUSE BUILDING 506 MAIN COMPRESSOR ROOM SUPPLY

The basic air supply consists of running either compressor Unit 1 or 2. Unit 1 is currently not operational. Both units are 18 1/2" and 11 1/2" x 8 1/2" stroke, double-acting reciprocating Ingersoll Rand 200 bhp (1130 acfm at 100-110 psig) compressor with 5-step unloading.

These units are the most power efficient units on the Arsenal and have a capacity control system, which effectively translates lower air demand with lower input energy.

The audit team observed Unit 2 running and except for a little too much oil from the oiler, it appeared to be in very good shape. These units are applied excellently and there are no more power efficient units available in this size class. They are still state-of-the-art systems.

75 HP Atlas Copco. Two-stage, water-cooled, single-acting DR 2 compressor with water-cooled heads and jackets. This unit is smaller and is 10% less driver efficient than the XLE. Parts are usually hard to obtain for these since they are manufactured in Belgium. The unit should be run as little as possible.

40 HP Gardner Denver. WXE air-cooled delivering 157 acfm at 41 BHP. It is also a 2-stage, single-acting unit and relatively old. It is also 10% less efficient than the XLE and should be run as little as possible.

25 HP Champion R70-12. 25 HP two-stage, single-action, tank-mounted (120 gal) reciprocating compressor delivering 91 cfm at 27 BHP. This unit is 15% less efficient than the XLE and should be run as little as possible.

These three back-up units will certainly not be required in the future if the NGEDAC unit is installed and the system is optimized, unless a significant low load condition occurs. Consideration should be given to using these units at selected places within the production areas, if required.

BUILDING 266 WIND TUNNEL SUPPLY SYSTEM

Current system runs on one of two Sullair two-stage lubricated rotary screw compressors. These are very efficient at full load (almost the same as XLE) and it runs full load approximately 500 hours a year. These are excellent state-of-the-art units and well applied.

There is a productivity problem with these units during supersonic operations caused by too slow top end refill. This is a result of the type of modulation control system in use. We will recommend a modification to correct this problem.

Other units in the Wind Tunnel area include:

Sullivan WN4 600 hp horizontal, double-acting, reciprocating, water-cooled unit. This unit is very old (1937) and has been taken out of service. It has not been removed and is still piped into the system. The discharge valve leaks on this unit is a constant leak. Estimate size 30 cfm (energy cost to supply this leak = $3,000 /yr). It is recommended that the piping should be disconnected and capped off and the compressor removed.

Gardner Denver 15 hp AD, tank-mounted compressor that does not seem to run at all. It is rated at 57 cfm at 100-110 psig. If not used in the wind tunnel today, this unit could perhaps supply an effective point of use need in the future. It is a good-quality industrial unit.

BUILDING 3150 SUPPLY SYSTEM

In addition to the new 25 HP Ingersoll Rand tank-mounted, there is an IMC (aluminum) 5 HP tank-mounted compressor installed as back up. Maintenance on these units is performed by Capital Equipment. They also maintain the two (2) Curtis tank-mounted 5 HP units used for HVAC controls. The IR 25 is heavy-duty industrial compressor and current state of the art for this type of unit, but it is significantly less efficient (15%) than the main XLE.

There are also some units now out of service that need to ultimately be removed, specifically:

Ingersoll Rand 40 HP ESV NL

71/2 HP Brunner tank-mounted unit (on mezzanine)

BUILDING 3028 SUPPLY SYSTEM

The ten IMC single-phase, 5 hp SP tank-mounted units are a commercial class, somewhat lighter-duty compressors. At the moment, the load cycle as described by plant personnel appears well applied. These are lower initial cost units that are basically "throw away" when any major repair is required. They are at least 20 percent less power efficient than the main Power House air compressor XLE.

If these units in both 3150/3028 we put into back up and air was supplied from the main Power House (XLE), there will be an approximate $13,000 per year electrical energy savings if these two buildings could effectively be fed from the main Power House (506). This recovery should be compared to the cost of extending main compressed air lines to the two buildings.

COMPRESSOR CAPACITY CONTROLS

The two most effective ways to run air compressors are at full load and off. Capacity controls are methods or restricting the output air volume delivered to the system, while the unit is still running. This is always a compromise and on a specific power (cfm/HP) basis is never as efficient as full load. For details on reciprocating, rotary screw and centrifugal, unloading controls, refer to the materials under the MISCELLANEOUS notebook tab.

Reciprocating Controls

The main Power House base reciprocating compressor is double acting, water-cooled unit with five-step unloading. This is an efficient compressed air unloading system, reciprocating five-step unloading will efficiently translate percentage of "less air used" into almost a comparable reduction in energy cost. (See Article & Curves under the MISCELLANEOUS notebook tab.)

Rotary Screw Controls

The two most common controls used are modulation and online/offline. Modulation is relatively efficient at very high loads-and very inefficient at lower loads. Online and offline is a very efficient commercial control available for loads below 60% when properly applied with adequate time for blow down. There are several other ("rotor length adjustment" or "variable displacement," and "variable speed drive") that have very efficient turn down from 100% load to about 60% load.

These controls must be installed properly to operate correctly and efficiently. The installation should have piping and storage available close to the unit with no measurable pressure loss at full load to allow the signal to closely match the air requirements. Also the systems at Picatinny have some modulation units (Sullair) and some online/offline (Atlas Copco). All appear to be installed properly and run correctly.

Recommendations

Short Term. All of the units involved have or are very close to having unloading controls capable of translating "less air used" into a comparable reduction in power cost. These controls will work effectively with your current piping and air receiver storage situation.

Long Term. With the system stabilized and balanced in the main Power House (506), consider a microprocessor-driven centralized full networking electronic control system. This will automatically place the most efficient machine online and assure no more than one partial loaded unit at a time.

AIR TREATMENT AND AIR QUALITY

General Air Treatment Concepts

Eliminating water/oil in air systems. The correct way to eliminate water and oil in your air system is to clean and dry the air immediately after it is produced in the compressor room. Then you can store clean dry air in a separate air receiver and flow it to the system as required.

Addressing water and oil carryover problems in a compressed air system. The water (condensate) and oil carryover problems in an air system are real and we can expect them to increase in magnitude in the extreme weather.

Guidelines regarding water and oil carryover control in compressed air systems.

1. Generally, it is best to eliminate the water and oil at the air source before it enters the air system.

2. Every 20ºF increase in temperature doubles the "moisture load" the compressed air will hold.

3. Compressed air dryers are usually capacity rated with 100ºF, 100 psig inlet air conditions. At 120ºF, 100 psig, the dryer's capacity rating is reduced by 50 percent.

4. Putting "dry or oil free" air into your system 90percent of the time and then allowing wet/oily air in sporadically 10 percent of the time will, in reality, give you a 'wet/oily system all the time." The liquid water and/or oil will fall out in the piping system continuing to "re-entrain" and contaminate and/or collected in the "low spots" of the system, thus recontaminating as it is pulled into the flowing compressed air system. A wet/oily system may well take many months of continued flow of clean dry air to "clean up."

5. Identify required pressure dew point.

Refrigerated air dryers. Refrigerated dryers require a refrigeration system to mechanically cool the air. The lowest possible consistent pressure dew point with a non-cycling dryer is +40ºF. Cycling dryers not only save power (60-75 percent), but also can deliver a lower pressure dew point (down to +35F to + 38ºF). Picatinny has some refrigerated dryers throughout the system, most in the dedicated control/fire air systems.

Desiccant dryers. Desiccant dryer regeneration types remove moisture vapor by "adsorbing" it to activated alumina desiccant beads (see the materials under the MISCELLANEOUS report tab. These dryers can consistently deliver a pressure dew point to -40ºF or lower, which removes much more water than conventional refrigeration units. To regenerate the wet tower while the other tower is drying, requires the use of heat in some form and some dry air to "sweep" or "purge" the exchanged moisture out. Desiccant dryers are usually rated at the same 100ºF inlet, 100 psig conditions.

Current Air Treatment System

The only dryers noted were in the dedicated systems:

Wind Tunnel - desiccant
Engine Starting - desiccant
Instrument Air/Control Air - desiccant and refrigeration.

All these dryers are sized to their particular application and must have their own air supply. These units normally run a very limited number of hours per year, and therefore, offer few significant opportunities for energy recovery. Nothing we observed would change this opinion. If in the future this changes, then that operation should be reviewed again.

The main Power House air is dried by water-cooled aftercoolers delivering 80°F saturated on a 79°F day. This is about as good as you can expect. The smaller units throughout the system have appropriate air- or water-cooled aftercoolers that appear to be satisfactory.

The Wind Tunnel use outside-mounted air-cooled after cooler to a dryer. This appears to work very well.

There are no compressed air line filters in the main Power House air (506).

BASIC SYSTEM HEADER/PIPING AND INTERCONNECTING PIPING BETWEEN THE PRIMARY AIR COMPRESSORS AND THE DISTRIBUTION SYSTEM

Basic Header Piping. Headers were checked at appropriate points with a single test gauge and there was little or no pressure loss in the header systems. Subsequently, we believe that the header system today can deliver the required air to any area without any significant pressure loss. Any low-pressure problems encountered will, in all probability, be in the feeds from the header to the area. The header runs between building is long, extensive, and old. There are leaks that have rusted through the pipe that create not only lost air but are also a safety issue.

Interconnecting Piping. Air is being delivered from the compressors to the interconnecting piping ranges between 78 psig and 80 psig and getting into the main air system at 78 to 80 psig. This is an apparent pressure loss of 0 psig, which is very good.

FLOW REGULATION AT THE PROCESS

Some flow regulators are probably set at higher than necessary feed pressure to the process, with some wide open to full header pressure. In this type of operation, it is very important that the actual inlet pressure to the process be known and that the lowest effective pressure be held steady for the proper product quality. Picatinny may need to install storage bottles downstream of the regulator to "close up" the pressure readings at rest and at operation. The minimum effective pressure at operation, established at the unit, for each product run needs to be established and adhered to.

AUTO CONDENSATE DRAINS

Automatic drain traps come in three categories. Level Operated Mechanically Activated Drains do not waste air, but are prone to clogging and require continuing maintenance to assure operation. These work best in a "Power House situation" where continuing regular attention is part of the system.

Dual Timer Electronic Drains use an electronic timer to control the number of times per hour it opens and the duration of the opening. The theory is that you adjust the times to be sure to fully drain the condensate and minimize the open time without water that wastes compressed air. The reality is that the cycles either do not get reset from the original factory settings (which causes condensate build up in the summer) or they get set wide open and not closed down later in cooler weather thus wasting more air. When they 'fail open', they blow at a full flow rate of about 100 cfm.

Consider that the usual factory setting is 10 minutes with a 20-second duration. Consider that 1500 scfm of compressed air will generate about 63 gallons a day in average weather or 2.63 gallons per hour. Each 10-minute cycle will have .44 gallons to discharge. This will blow through a 1/4 " valve at 100 psig in approximately 1.37 seconds. Compressed air will then blow for 18.63 seconds each cycle, 6 cycles a minute will equal 111.78 seconds per hour of flow or 1.86 minutes per hour of flow. This will waste about 3.1 cfm. A 1/8" valve will pass about 100 cfm. The total flow will be 100 x 1.86 = 186 cubic feet in 1 hour 60 minutes = 3.1 cu ft/min average. Energy cost/lost air = $ 310 /year/valve.

Level Operated/Electronic Drains can receive the signal to open from the condensate high level and the signal to close from the condensate low level. These waste no air and from a power cost standpoint, are the best selection and their reliability is usually many times greater than the level operated mechanical.

There is no doubt that automatic drain traps are a much better idea than manual drains for Picatinny's circumstance. The Arsenal should take the following action:

* For air conservation and enhanced performance, all dual timer electronic drains and manual drains should be replaced by level-actuated electronic or air-operated drains. Timer-activated drains or dual-timer drains may not be able to handle "heavy loads" of condensate unless continuously "monitored during the summer conditions."

Be sure your auto drains are set up to work effectively. Some examples are:

• Drains should not be tied together to a common header
• Be sure all drains can be checked easily for operation
• Be sure all drains are properly "vented."

The survey of the condensate handling system revealed several issues. Arsenal personnel stated that the condensate goes to a mechanical oil/water separator and then to the storm sewer and lake. The discharge is monitored constantly to assure no EPA violation according to plant personnel. If this is always in effect, there is no apparent problem.

If Picatinny is discharging filtered condensate to a storm sewer or in some other manner to ground water (Federal EPA minimum is 10 ppm) or are required to separate it by local water treatment facility, this issue should be discussed in detail.

LEAK MANAGEMENT PROGRAMS

With a campus facility of this type, an effective leak control program could well save in the average range of 300 to 400 cfm which could be $ 30,000 to $ 40,000 potential annual power cost savings. The estimated recoverable value is $ 25,000 /yr.

To effectively control and manage leaks in such an extensive operation as Picatinny Arsenal, we believe that a continuing economical program must be in place. Generally speaking, the most effective programs are those that involve the production supervisors and operators in a positive manner working with the maintenance personnel.

Accordingly, the TMS Team recommends:

In the short-term set up a continuing leak inspection by Maintenance Personnel so that for a while, each primary sector (see drawing) of the plant is inspected once a quarter or at a minimum, once every six months to identify and repair leaks. A record should be kept of these findings and overall results.

In the long-term consider setting up programs where the production people (particularly the operators and their supervisors) are positively motivated to identify and repair these leaks. The Project Cost Section includes a quotation for your information on a very effective ultrasonic leak locator.

The Project Cost Section also lists some electric-operated automatic ball valves that can be installed in the main feed line to a piece of equipment and be wired in so as to open and close when the machine is powered up or shut off and thus eliminate off-production leaks and open air left on.

CABINET COOLERS

There may be cabinet coolers in use in the facility. Some with refrigeration (1,500 Btu), some with compressed air-driven vortex coolers; and some may just have compressed air blowing into them. These all may be able to be replaced with "heat tube" cabinet coolers with a potential savings of 3.5 to 4 kW each.

The initial cost for this range is usually in the $700 to $750 range with a potential resultant electric savings of $1,000-$2,000/year each.

BLOW OFFS

Picatinny may have 1/8" and 1/4" lines running as blow off on units at 80 psig. These will use 8 to 35 cfm each.

An alternate is an air amplifier which takes less compressed air and through Venturi action amplifies the usable air by pulling in significant amounts of ambient air and mixing it directly into the air stream. These have amplification ratios up to 25:1. Using 10 cfm of compressed air would generate a savings of 25 cfm compressed air per 1/4" blow off and flow 250 cfm total air at the process.

For example, 1/4" one-foot-long tube will flow 35 cfm at 80 psig inlet. Annual cost power of $ 3500 /yr/ea. Place a variable flow Venturi nozzle to amplify flow on the end of this tube and it will now only use 10 cfm and flow 250 cfm at the work.

VACUUM GENERATORS

Production may use vacuum generators. Vacuum generators are:

• Very convenient
• Very responsive
• Very inefficient compared to positive displacement pumps, e.g., rotary screw, reciprocating

Note that energy cost escalates as vacuum goes down with Venturi generators. Energy cost also falls as vacuum goes down after about 14" with positive displacement pump. It is very important to only run a Venturi vacuum generator to a minimum vacuum and a minimum acceptable "on time" cycle at the lowest possible pressure.

For example, if generator uses 60 scfm at 80 psig, it can pull a 20" vacuum in about .25 seconds. If shut off at 20" vacuum, total air demand will be about .25 scfm with Energy Cost = $25 /yr. If allowed to run continuously, air usage 60 scfm with Energy Cost = $ 6000 /yr.

AIR-OPERATED DIAPHRAGM PUMPS

Air-operated diaphragm pumps are generally used because they tolerate aggressive conditions relatively well and run without catastrophic damage even if the pump is dry. Efficiency is not usually considered.

There are several areas to pursue here in the future to perhaps generate significant air savings:

Is the air-operated diaphragm pump the right answer? An electric pump is significantly more power efficient. Electric motor driven diaphragm pumps are available.

Consider the installation of electronic or ultrasonic controls to shut the pumps off automatically when they are not needed. Remember the pump uses the most air when it is pumping nothing.

Is Picatinny running most of the time at the lowest possible pressure? The higher the pressure, the more air used. For example, often a filter pack operation, the pump does not need high pressure except during the final stages of the filter packing cycle. Controls can be arranged to accomplish lower pressure in the early stages and higher pressure later which may generate significant savings.

MISAPPLIED HIGH PRESSURE AIR

High pressure air being used for very low pressure applications is not an efficient use of energy. A close review of your system should be made and measurements taken to identify if there is any potential energy savings in using an alternate source of low pressure air in the production area.

This section provides a preliminary assessment of the opportunity for gas engine driven compressors at Picatinny Arsenal. The assessment is based on three key design factors:

Operating the new system as a fully hybrid system with the existing electric system



Meeting environmental requirements of the area



Improving the current demand system so that the air requirements for the new system are minimized, along with producing system operating costs for the Arsenal

GAS ENGINE-DRIVEN SYSTEM DESIGN FACTORS

The conceptual design for the Picatinny gas engine driven system is based on providing the full requirements of the main system at Picatinny, but configured as full hybrid system in conjunction with the existing electric system. In this way, the existing electric system can serve as a back-up to the gas engine system if the gas system has a planned or unplanned shutdown or if the air requirements of the base are suddenly increased.

Using this approach, the Department of Defense can gain experience with not only operating a gas engine driven system, but also integrating it with electric systems to improve overall compressed air system reliability and reduce operating costs. This flexibility is especially important given the increasing uncertainty associated with the price and supply reliability of most energy sources.

Environmental issues are key areas to address in any major project on this nature, particularly on the East Coast. The assessment is based generating up to 0.70 gm/bhp/hr for NOx and 0.48 gm/bhp/hr for CO.

The current demand for compressed air of 925 acfm can be reduced by an estimated 500 acfm. This reduction can be accomplished by reducing leaks (a potential reduction of 300 acfm throughout the day) and shutting off equipment during non-production periods (a potential reduction of 200 acfm during the non-production period from 6 pm to 6 am).

The gas engine driven system evaluated in this study reflects the reduced demand level, even though the original demand level would make the gas-driven system appear to be even more cost-effective.

OPERATING COST COMPARISON

Table 1 displays the electrical energy costs for the Main Power House System for both the current demand level and the reduced demand level. Annual electrical costs are $99,487 for the current system and $57,612 for the modified system, a savings of $32,000 annually. Maintenance contract costs for both are estimated at $11,800 annually given the age and condition of the machines. The sum of the operating costs for energy and maintenance costs is $111,287 for the current demand level and $69,412 for the modified level.


Table 1. Electrical Energy Costs (Annual) - Main Power House

Table 2 on the next page displays the estimated operating cost for two types of gas engines: 3406TA and the slightly smaller 3306TA. Annual fuel costs for the 3406TA system are $28,976 annually and $26,206 for the 3306TA system. The 3306TA system is some $32,000 less in energy costs than the current electric system based on the modified air demand level. The number increases to $56,000 annually based on the original air demand level.

Contract maintenance costs are $28,908 annually for the 3406TA system and $21,900 for the 3306TA system. This is some $10,000-17,000 higher than with the electric system.

The sum of the operating costs for energy and maintenance contract are $57,884 for the 3406TA system-some $12,000 less than the electric system on an annual basis. The sum of the operating costs for energy and maintenance contract are $48,106 for the 3306TA system-some $21,000 less than the electric system on an annual basis.


Table 2. Cost Comparison: Natural Gas Engine 3406TA/3306TA

Blended Power Rate = 3.41 MCF. Based on NG/water-cooled engine @ 80 psig with
1,000 Btu per ft3 MCF


Estimated Fuel Costs: Gas Engine System 3406TA:

CAPITAL COST ASSESSMENT

Table 3 displays capital cost estimates for three configurations of the natural gas engine-driven systems: IR 3406, GD3406, and GD3306. The capital costs include the catalytic converter and a placeholder estimate for installation costs.

Without consideration to potential cost reductions resulting from negotiating or utility rebates, the capital costs for the natural gas systems are on the order of $150,000.

Table 3. Capital Expenditure Need For Picatinny

¹ Add $4,000 for air-cooled engine and compressor and water-cooled aftercooler -- air-cooled installation may be preferable with adequate ventilation.

² Based on a generation limit of NOx 0.70 gm/bhp/hr and CO 0.48 gm/bhp/hr.