Gila River Indian Community (GRIC) TIP Development 

Source Specific Emission Limitations & Standards 

Technical Support Document 

June 10,2002 Version 

Section 7, Rule 6.0 -Aerospace Manufacturing and Rework Operations 

1.0 Introduction and Source ~escri~tion' 

Aerospace manufacturing and rework operations include all manufacturing facilities that 

produce an aerospace vehicle or component and all facilities that rework or repair these 

aerospace products. An aerospace vehicle or component is defined as, but not limited to, 

any fabricated part, processed part, assembly of parts, or completed unit of any aircraft 

including, but not limited to, airplanes, helicopters, missiles, rockets, and space vehicles. 

In addition to manufacturing and rework facilities, some shops may specialize in 

providing a service, such as chemical milling, rather than actually producing a component 

or assembly. In general, aerospace manufacturing and rework facilities are covered by 

the SIC codes listed in Table 1 - 1. However, facilities classified under other SIC codes 

may meet the definition of an aerospace manufacturing or rework facility. Table 1-2 lists 

the products included in aircraft, aircraft engines, and space vehicle and missile 

categories. 

TABLE 1 - 1. AEROSPACE MANUFACTURING SIC CODES 

1 3721 I Aircraft I 

SIC Code 

3 720 

Description 

Aircraft and Parts 

3 724 

3 728 

Aircraft Engines and~n~ine Parts 

Aircraft Parts and Eaui~ment 

3760 

3761 

Guided Missiles, Space Vehicles, and Parts 

Guided Missiles and S~ace Vehicles 

3 764 

3769 

Aerospace facilities may be divided into four market segments: commercial original 

equipment manufacturers (OEM), commercial rework facilities, military OEM's, and 

military rework facilities. The commercial OEM segment of the market includes the 

manufacture of commercial aircraft as well as the production of business and private 

Space Propulsion Units and Parts 

Swace Vehicle Eaui~ment 

4512 

458 1 

971 1 

1 "Control of Volatile Organic Compound Emissions fiom Coating Operations at Aerospace Manufacturing 

and Rework Operations", Emission Standards Division, U.S. Environmental Protection Agency, December 

1997. 

Air Transportation, Scheduled 

Aqorts, Flying Fields, and Services 

National Securitv 
aircraft. The military OEM segment of the market includes military installations and 

defense contractors that manufacture aircraft, missiles, rockets, satellites, and spacecraft. 

Rework facilities, both commercial and military, may rework many of the above end 

products. 
Table 1-2. Listing of Products Included in the Aerospace Industry 

I Category Products 

Reconnaissance 

ResearchlTest Bed 

Military Fixed-Wing Aircraft Attack Bombers 

Cargo/Transport/Refueling 

Early Warning 

Electronic Warfare 

Commercial Fixed-Wing 

Tiltrotor 

Training 

Training 

Utility 

Narrow Body Turbofans 

Aircraft 

Rotary-Wing Aircraft 

Wide Body Turbofans 

Turboprops 

Naval 

Scout/Attack 

Turboprop 

Reciprocating Engine-Powered 

Business & General Aviation 

Gas Turbine Engines 

Unmanned Aerial Vehicles and 

Transport 

Utility 

Aircraft Turbofan 

I Drones 1 1 

Missiles Air-to-Air 

Air-to-Surface 

Anti-Armor 

SpaceLaunch Vehicles 

Anti-Ballistic 

Anti-Shi~ 

Manned Systems 

Unmanned Svstems 

I Anti-Submarine 

Based on information f?om the Federal Aviation Administration and the U.S. Department 

of Commerce Bureau of the Census, there are an estimated 2,869 aerospace facilities. Of 

this number, 1,3 95 produce or rework commercial products, and 1,474 produce or rework 
military products. The combined VOC emissions from these facilities are estimated to be 

over 21 3,000 megagramslyear (Mdyr) (234,000 tonslyr). 

In addition to these facilities, there are numerous subcontractors that manufacture or 

rework aerospace vehicles or components. The subcontractors may work directly for the 

OEM or rework facilities, or indirectly through first line subcontractors. Because most of 

these subcon~ctors perform various types of work, they are often classified under nonaerospace SIC codes. Consequently, an estimate of the number of subcontractors cannot 

be made. One company alone, however, employs the services of over 5,000 

subcontracl~rs. 

Aerospace manufacturing facilities and rework operations typically are located in or near 

industrial centers in areas of medium to high population density. Aerospace 

manufacturing facilities range in size from small shops that produce a single aerospace 

component, such as propellers, to large corporations that produce the entire aircraft. 

Aerospace rework facilities, however, are usually large facilities that must be able to 

rework or repair every facet of several models of large commercial or military aircraft. 

The hours of operation at aerospace manufacturing and rework facilities may vary greatly 

due to the production backlog at each facility. The hours of operation may range from 8 

hours (or less) per day, 5 days per week, to 24 hours per day, 7 days per week. 

Aerospace manufacturing and rework operations typically consist of the following basic 

operations: materials receiving, machining and mechanical processing, coating 

application, chemical milling, heat treating, cleaning, metal processing and finishing, 

coating removal (depainting), composite processing, and testing. Many aerospace 

manufacturing and rework facilities may employ all of these processes in their 

operations, as with an OEM facility that produces the entire aerospace vehicle. However, 

an aerospace facility may only employ a subset of these operations, as with a facility that 

produces a single component or assembly or a facility that provides a service such as 

chemical milling. Of these operations, coating application and solvent cleaning are the 

significant sources of VOC emissions and are the focus of this rule. Other emissions 

fiom these facilities are addressed by other regulations including emissions fiom chrome 

plating (40 CFR 63 Subpart N), emissions from degreasing and solvent cleaning (Section 

V1.D - VOC Requirements), and emissions fiom combustion sources. Emissions from 

aircraft engine testing are not specifically regulated anywhere in the United States. 

The following subsections provide a description and background on the coating 

operations and solvent cleaning operations that are the focus of this rule. 

1.1 Coating Application Operations 

A coating is a material that is applied to the surface of a part to form a decorative, 

protective, or functional solid film. The most common coatings are the broad categories 

of nonspecialized primers and topcoats that are regulated for major sources under the 

Aerospace NESHAP (i.e., 40 CFR 63 Subpart GG). There are also numerous specialty 
coatings that provide additional performance characteristics, such as temperature, fluid, 

andlor fire resistance, flexibility, substrate compatibility, antireflection, temporary 

protection or marking, sealing, adhesively joining substrates, enhanced corrosion 

protection, or compatibility with a space environment. Each material is different because 

it must meet individual performance standards particular to a specific design. The quality 

of the coatings is critical to the airworthiness and safety of the final product. Aerospace 

vehicle manufacturing is strictly controlled by the Federd Aviation Administration, the 

Department of Defense, and specific customer requirements. Industry specifications for 

coatings are dictated by these requirements. Such specifications are often difficult to 

change, requiring long time periods to test and approve new formulations and 

alternatives. 

Most aerospace coatings are solvent-borne, which contain a mixture of organic solvents, 

many of which are VOCs. The most common VOC solvents used in coatings are toluene, 

xyleae, methyl ethyl ketone, and methyl isobutyl ketone. The VOC content of a coating 

can differ significantly for the various coating categories. 

Sealing - 

Sealants, predominately composed of polysulfide, are applied throughout the aerospace 

vehicle structure primarily to seal out moisture and contaminants to prevent corrosion, 

such as on faying (i-e., closely or tightly fitting) surfaces, inside holes and slots, and 

around installed fasteners. They are also used to seal fuel tanks and pressurized 

components. Sealants are applied using tubes, spatulas, brushes, rollers, or spray guns. 

Sealants are often stored frozen and thawed before use, and many are two-component 

mixtures that cure after mixing. Typically, a sealant is applied before assembly or 

fastener installation, and the excess is squeezed out or extruded from between the parts as 

the assembly is completed. This ensures a moisture-tight seal between the parts. 

Adhesive Bonding - 

Adhesive bonding involves joining together two or more metal or nonmetal components. 

This process is typically performed when the joints being formed are essential to the 

structural integrity of the aerospace vehicle or component. Bonding surfaces are 

typically roughened mechanically or etched chemically to provide increased surface area 

for bonding and then treated chemically to provide a stable corrosion-resistant oxide 

layer. The surfaces are then thinly coated with an adhesive bonding primer to promote 

adhesion and protect from subsequent corrosion. Structural adhesives are applied as 

either a thin film or as a paste. The parts are joined together and cured either at ambient 

temperature, in an oven, or in an autoclave to cure the adhesive and provide a permanent 

bond between the components. 

Nonstructural adhesives are used to bond materials that are not critical to the structural 

integrity of the aerospace vehicle or component, such as gaskets around windows and 

carpeting or to nonstructurally joined components. These adhesives are applied using 

tubes, brushes, and spray guns. 
1.2 Solvent Cleaning Operations 

Cleaning agents for hand-wipe, flush, and spray equipment cleaning consist of solvents 

such as methyl ethyl ketone, methyl isobutyl ketone, toluene, various solvent blends, or 

alkaline materials. 

Hand-Wipe and Flush Cleaning - 

Aerospace components are cleaned frequently during manufacturing to remove 

contaminants such as dirt, grease, and oil, and to prepare the components for the next 

operation. Cleaning is typically performed by a hand wiping process using a wide variety 

of cleaning solvents. Assemblies and parts with concealed or inaccessible areas may be 

flush-cleaned by passing the cleaning agent over, into, or through the part. The cleaning 

agent is then drained from the part and the procedure is repeated as many times as 

necessary to ensure the required cleanliness. 

Spray Gun and Coating Line Cleaning - 

Spray guns and coating lines used to apply the various 'coatings used at aerospace 

facilities must be cleaned when switching hm one coating to another and when they are 

not going to be immediately reused. Spray guns can be cleaned either manually or with 

enclosed spray gun cleaners. Manual cleaning involves disassembling the gun and 

placing the parts in a vat containing an appropriate cleaning solvent. The residual paint is 

brushed or wiped off the parts. After reassembling, the cleaning solvent may be sprayed 

through the gun for a fd cleaning, Paint hoseslcoating lines are cleaned by passing the 

cleaning solvent through the lines until all coating residue is removed. Enclosed spray 

gun cleaners are self-contained units that pump the cleaning solvent through the gun 

within a closed chamber. After the cleaning cycle is complete, the guns are removed 

from the chamber and typically undergo some manual cleaning to remove coating residue 

from areas not exposed to the cleaning solvent, such as the seals under the atomizing cap. 

2.0 GRIC Source Profile 

Two sources currently located and operating on GRIC land comprise the aerospace 

manufacturing and rework source category. Those sources are: 

Honeywell (formerly Allied Signal) 

AMTI (Advanced Material Technologies, Inc.) 

Honeywell 

This facility is an aircraft engine and auxiliary power unit (APU) test facility. Units 

tested include Turbofan, Turboshaft, and Turbojet engines. JP8 and Jet A hels are stored 

and used in testing. There are 5 open test cells and 3 enclosed test cells. Multiple 

portable generators are used for power. Emissions from this facility occur from internal 
he1 combustion in the test engines and diesel powered generators, JP8, Jet A, and diesel 

he1 storage and loading, and minor VOC material usage. 

This facility refurbishes jet engine parts (APU). Major process operations include metal 

stripping, fluoride cleaning, pressure treatment of castings, coating operations, grit 

blasting, and electroplating. Emissions fiom this source are associated with combustion 

emissions from powder coating operations (3 gas-fired aluminizing furnaces), gas and 

solvent cleaning processes (VOC), grit blasting (PM), vapor degreasing (TCE), masking 

(TCE), and acid processes in the electroplating operations. PM fiom grit blasting is 

controlled in a dust hog bag filter. A 16,000 cfin (cubic feed per minute) caustic scrubber 

installed in 1997 controls acid gas emissions from the electroplating operations. 

3.0 Technical Review - Emissions Units, Pollutants, and Control ~echnolo~ies~ 

3.1 Emissions Units and Pollutants 

Various activities at aerospace manufacturing and rework facilities result in emissions. 

In general, these emissions can be divided into two categories. The first category 

represents dose emission-producing activities that are general in nature and not 

necessarily related specifically to the aerospace industry. Emission sources that Ml in 

this category include combustion sources (i.e., heaters, boilers, curing ovens, diesel 

generators, etc), certain solvent cleaning operations (i-e., vapor degreasers and cold 

cleaners), metal plating operations, and abrasive blasting operations. These nonaerospace specific emission sources are not addressed by this rule. 

The second category of air emissions from aerospace manufacturing and rework facilities 

are those that are more specific to the aerospace industry. Air emissions, primarily 

volatile organic compounds (VOCs), result mainly fiom the sealing, painting, depainting, 

bonding, finishing application processes including material storage, mixing, applications, 

drying, and cleaning. These emissions are composed mainly of organic solvents which 

are used as carriers for the paint or sealant and as chemical coating removers. Most 

aerospace coatiqgs are solvent-based, which contain a mixture of organic solvents, many 

of which are VOCs. The most common VOC solvents used in coatings are toluene, 

xylene, methyl ethyl ketone, and methyl isobutyl ketone. The most common VOC solvent 

used for coating removal is methylene chloride. The VOC content ranges differ for the 

various coating categories. 

3.2 Controls 

The principal technique used by the aerospace industry to control VOC emissions fiom 

coating application and cleaning is product substitution, which eliminates or reduces the 

generation of emissions. The emission reduction is obtained using less energy and 

producing less waste than using a control device to achieve the same emission reductions. 
The VOC emissions may be controlled by replacing products containing high 

concentrations of VOCs with ones that have reduced or eliminated VOCs. Different 

aerospace manufacturers use different processes to produce their product. Therefore, 

they typically have different specifications for the coatings and cleaning solvents used on 

the components of the end products. Each individual facility must evaluate the ability of 

the new product to maintain standards of quality and performance. In addition, the 

potential overall environmental benefit of the reformulated products must be carefully 

evaluated. 

A second major method of emissions control for the aerospace manufacturing and rework 

industry sector is the use of improved equipment and application methods. When 

combined with reduced solvent coatings and cleaners, these additional changes are 

effective at addressing aerospace VOC emissions. 

The following sections describe the available product substitutions for coatings and 

cleaning solvents and typically employed equipment changes. While alternative 

methods, such as control devices (carbon adsorbers, incinerators, etc.), are occasionally 

used to reduce emissions, they represent emission reductions that go beyond reasonably 

available control levels and are, therefore, not discussed below. 

Coating Substitutions - 

Waterborne and high solids materials are generally used for coating substitutions. 

Specialty coatings typically have relatively low usage, so reformulation of these coatings 

to lower VOC contents does not produce significant air quality benefits nor is it 

economically feasible for the paint suppliers. Paint suppliers and the aerospace industry 

generally have targeted high volume materials for reformulation efforts. Therefore, 

lower VOC formulations are not available for most of the low-volume speciahy coating 

categories. 

Equipment Changes - 

The aerospace industry has implemented several equipment changes that directly reduce 

the level of VOC emissions. While there are equipment changes that effect emissions 

from every process, the three changes predominantly used in the industty are high 

transfer efficiency spray guns, spray gun cleaners, and conventional high transfer 

efficiency methods. Each of these equipment changes is discussed below. 

High Transfer Efficiency Spray Guns 

Emissions from spray coating operations can be reduced through the use of spraying 

systems with higher transfer efficiency. Transfer efficiency, expressed as a percentage, 

can be defined as the ratio of coating solids actually applied to the surface of the 

component being coated to the total amount of solids released from the spray gun. 

Spraying systems with a higher transfer efficiency can coat the same dace area using 

less coating. Therefore, the VOC emissions resulting from the use of this equipment are 
reduced compared to applying the same coating with conventional spray equipment. The 

transfer efficiency values reported in this section depend on coating sprayed, part 

configuration, spray booth air velocity, and other variables. 

Most aerospace components are coated using manual spray equipment utilizing 

conventional air spray or airless spraying technology. The following sections discuss two 

types of high transfer coating application equipment generally used in the aerospace 

industry for the application of primers and topcoats: high volume, low pressure (HVLP) 

and electrostatic. (Note that the use of these types of high transfer efficiency for specialty 

coatings is limited.) 

High Volume Low Pressure Sprav Guns - High volume low pressure and 

electrostatic spraying systems are the primary high efficiency spray methods used 

by the industry. High volume low pressure spray guns use high volumes [lo to 25 

standard cubic feet per minute (scfin)] of low pressure 12 to 10 pounds per square 

inch gauge (psig)] air to deliver the paint. The lower air pressure creates a lower 

particle speed, resulting in a more controlled spray pattern with less overspray and 

bounce back fkom the substrate, thus improving transfer efficiency. 

High volume low pressure systems have been in use in the United States for 

approximately 10 years. In early systems, turbines were used to supply a high 

volume of low pressure air to the spray guns through large hoses. The second 

generation used compressed air with an air regulator to maintain the required low 

pressure. The third and cwrent generation of HVLP equipment uses restrictors 

within the gun to reduce the atomization pressure to a maximum of 10 psi at the 

air cap. 

One disadvantage of HVLP spray guns is that some very high solids coatings are 

difficult to atomize due to their higher viscosities. However, when a turbine is 

used, the temperature of the atomizing air increases which aids in reducing the 

viscosity of the coating. Other disadvantages of HVLP spray guns are that they 

cannot be used with extension nozzles, and they may slow production rates 

because of the low fluid delivery rates. 

It is estimated that HVLP equipment can be used to apply approximately 80 

percent of the coating currently used in the aerospace industry, including primers, 

waterborne coatings, and both single and two-component topcoats. As an 

example, a medium sized comerciaVrework facility utilizing HVLP equipment 

in combination with high solids paints has had a reduction of 22 to 30 percent in 

coating usage for various aircraft types. The HVLP technology has proven easy 

to use and maintain. It also provides high transfer efficiency and appears to be the 

preferred spray technology in the aerospace industry at this time. 

Electrostatic Spray Guns - With electrostatic spray systems, atomized particles of 

coating acquire an electric charge as they pass through a high voltage field at the 

end of the spray nozzle. This electric charge causes the particles to be attracted to 
the parts being painted, which are electrically grounded. Although other 

substrates can be pretreated with conductive coatings, this technology is primarily 

used for metal parts. The electrostatic effect can be utilized in conjunction with 

air spray, airless, and air-assisted airless systems to enhance the transfer 

efficiencies of these basic technologies. See Table 3-1 for examples of percent 

reduction obtained at various facilities using electrostatic spray guns or 

electrostatic spray guns in combination with HVLP spray guns. 

Spray Gun Cleaning 

Spray guns are typically cleaned at the end of every job, as well as between color 

changes. Manual cleaning of spray guns involves disassembling the gun and placing the 

parts in a tray containing an appropriate cleaning solvent. The residual paint is brushed 

or wiped off the parts, then cleaning solvent is sprayed through the gun after it is 

reassembled. Various methods are used to minimize the resulting emissions hm spray 

gun cleaning and are discussed below. 

Enclosed System - Enclosed spray gun cleaners are completely enclosed units 

that spray the cleaning solvent through and over the spray gun. The enclosed unit 

eliminates most of the exposure of the cleaning solvent to the air, thereby greatly 

reducing the VOC emissions from evaporation. 

Nonatomized Cleaning - Cleaning solvent is placed in the pressure pot and forced 

through the gun with the atomizing cap in place. No atomizing air is used. The 

cleaning solvent hm the spray gun is directed into a vat, dnun, or other waste 

container that is closed when not in use. 

Disassembled S~rav Gun Cleaning - Manual cleaning with the components 

cleaned by hand in a vat, which is closed when not In use. Alternatively, the 

components are soaked in a vat, which is closed at all times except when 

components are being inserted or removed. 

Atomizing Cleaning - Cleaning solvent is forced through the spray gun and the 

resulting atomized spray is directed into a waste container that is fitted with a 

device designed to capture the atomized solvent emissions. 

Conventional High Transfer Efficiency Application Methods 

Conventional high transfer efficiency application methods for primers and topcoats 

include dip, roll, brush, and flow coating (use of these methods for specialty coatings is 

limited). These methods are discussed below. 

Dip Coating - With dip coating application, parts are immersed into a tank of 

coating. The parts are then removed fiom the tank and held over it until the 

excess coating drips back into the tank. This method is simple and allows many 
different parts to be coated with high transfer efficiency. However, dip coating is 

limited to parts that can fit into the dip tank. Other parts difficult to dip coat could 

include complex parts that would trap the coating, allowing unequal coating 

thickness 

Roll Coating - In roll coating application, a series of mechanical rollers are used 

to coat flat surfaces. This method achieves high efficiency with high rates of 

application and automation. However, roll coating is limited to flat parts. 

Brush Coating - In brush coating application, brushes and hand rollers are used to 

apply the coating manually. This method is used with operations (e.g., touch-up 

and detail painting) that cannot tolerate the overspray associated with spray gun 

application. For example, if a facility needs to paint only the tail section of an 

airplane, it may be easier to brush coat this area than to mask the entire plane to 

protect the rest of the shell hm overspray. This application method typically 

involves high labor costs, increased production time, and poor coating thickness 

control. 

Flow Coating - In flow coating application, the part is conveyed over a closed 

sink, and a pumped stream of coating gently flows over the surface of the part. 

The excess coating is drained into the sink, filtered, and pumped to a holding tank 

for reuse. Flow coating is typically limited to flat sheets and noncritical parts. 

Coating thickness is difficult to control using flow coating. 

Hand-Wipe Cleaner Substitutions - 

Product substitutions for hand-wipe cleaning that are prevalent in the aerospace industry 

can be classified as aqueous, semiaqueous, citrus-based, and reduced vapor pressure. 

Each category is discussed below. 

Aqueous and Semi-aqueous 

Aqueous and semi-aqueous cleaners contain water as the base component rather than an 

organic solvent or mixture of solvents. Other components may include corrosion 

inhibitors, alkaIinity builders, and organic surfactants, depending on the desired soil 

removal properties. Aqueous and semi-aqueous cleaners have been used in non-critical 

areas where strict cleanliness requirements do not have to be met, or where there are no 

confined spaces that may trap residues of the cleaner. 

The advantages of using aqueous and semi-aqueous cleaning solvents include reduced 

VOC emissions. Disadvantages are increased production time due to slower evaporation 

rates, possible decreased efficiency, and possible increase in wastewater treatment 

requirements. In addition, aqueous cleaners may not be applicable to all aerospace parts, 

especially those components that have small confined spaces where the cleaner residues 

cannot be adequately removed. 
Citrus-Based 

Citrus-based terpenes such as d-limonene are the primary components in many 

alternative cleaning solutions. While these solutions have high VOC contents, their 

vapor pressure is very low, leading to reduced evaporation rates. These cleaners have 

been found to be effective in some cleaning operations except for cleaning prior to 

adhesive bonding. Some disadvantages include possible worker sensitivity, VOC 

emissions, lack of rinseability in water, and increased production time due to slower 

evaporation rates. 

Reduced Vapor Pressure 

Reduced vapor pressure cleaning solvents have a maximum VOC composite vapor 

pressure of 45 millimeters of mercury (mrnHg) at 20°C. Cleaning solvent emissions are 

reduced because their lower vapor pressure leads to reduced evaporation rates. These 

cleaners are effective in many cleaning operations except for some limited operations 

such as cleaning oxygen systems. 

4.0 Regulatory Review 

4.1 Tribal Programs/Rules 

A review of U.S. tribal air quality programs was performed to define the baseline of 

existing tribal rules and source specific standards. This review was conducted jointly 

between RTP and the GRIC. At the time of this review, no tribal programs or rules were 

identified that specifically pertained to the Aerospace Manufacturing and Rework source 

category. 

4.2 Federal Programs and Regulations 

There are a number of Federal NSPS and NESHAP regulations that are potentially 

applicable to non-aerospace specific activities that may occur at aerospace manufacturing 

and rework facilities (i.e., 40 CFR 60 Subpart D, 40 CFR 60 Subpart K, 40 CFR 63 

Subpart T, and 40 CFR 63 Subpart N among others). 

In addition to these non-aerospace specific regulations, there is a promulgated NESHAP 

standard (Subpart GG) specifically applicable to major aerospace manufacturing and 

rework facilities2 and a NESHAP standard currently being developed to regulate 

emissions fiom aircraft and rocket engine testing activities. As well, EPA has developed 

Control Technique Guidelines (CTG) for aerospace manufacturing and rework facilities. 

Most existing SIP regulations governing aerospace manufacturing and rework are based 

on EPAYs CTG. The CTG also serves as the basis is the rule defined in Section 5 of this 

2 The term "major" in this context means a potentially affected source that has the potential to emit more 

than 10 tons per yea. of any single hazardous air pollutant or 25 tons per year of any combination of 

hazardous air pollutants. 
document. Tables 4- 1 and 4-2 summarize the key emission limits and work practice 

standards found in Subpart GG and the Aerospace CTG respectively. 

Table 4- 

Equipment I 

process Unit 

Cleaning Operations 1 

Housekeeping Measures 

40 CFR 63.744(a) 

Cleaning Operations / 

Hand-wipe Cleaning 

40 CFR 63.744(b) 

. 40 CFR 63 sub^ 

Pollutant I 

Parameter 

HAP & VOC 

HAP & VOC 

~rt GG Summary 

Emission Limit I Standard (Units) 

Place solvent laden cloth in enclosed 

containers. 

Store fresh and spent solvent in 

closed containers. 

Conduct handling and transfer of 

cleaning solvents in a manner to 

minimize spills. 

Cleaning solvents must meet one of 

the following requirements: 

Aqueous: Cleaning solvents in 

which water is the primary 

ingredient. 

Hydrocarbon-based: Cleaners that 

are composed of photochemically 

reactive hydrocarbons andlor 

oxygenated hydrocarbons and have a 

maximum vapor pressure of 7 mm 

Hg at 20 OC (3.75 in. &I20 and 

68 OF). These cleaners also contain 

no HAP. 

Have a composite vapor pressure of 

45 mm Hg (24.1 in. H20) or less at 

20 OC (68 OF); or 

Demonstrate that the volume of 

hand-wipe solvents used in cleaning 

operations has been reduced by at 

least 60% from a baseline adjusted 

Spray Gun cleaning 

40 CFR 63.744(c) 

Cleaning Operations / - 

or their equivalent: 

Enclosed system.; 

Nonatomized cleaning; 

Disassembled spray gun 

HAP & VOC 

cleaning; 

for production. 

Use one or more of the techniques, 
Table 4-1. 40 CFR 63 Sub~art GG Summarv 

Equipment I 

Cleaning Operations I 

Flush Cleaning 

40 CFR 63.744(d) 

HAP & VOC 

Pollutant I 

Parameter 

vapor capture. 

Empty the used cleaning solvent 

Emission Limit I Standard (Units) 

Atomizing cleaning with 

each time aerospace parts or 

assemblies, or components of a 

coating unit (with the exception of 

spray guns) are flush cleaned into an 

enclosed container or collection 

system that is kept closed when not 

in use or into a system with 

eauivalent emission control. 

Primer and Topcoat 

Uncontrolled Coatings - 

Primers 

40 CFR 63.745(c) 

HAP & VOC Organic HAP emissions from 

primers shall be limited to an 

organic HAP content level of no 

more than: 350 g/L (2.9 lblgal) of 

primer (less water) as applied or 540 

g/L (4.5 lblgal) of primer (less 

water) as applied for general 

aviation rework facilities. 

VOC emissions from primers shall 

be limited to a VOC content level of 

no more than: 350 g/L (2.9 lblgal) of 

primer (less water and exempt 

solvents) as applied or 540 g/L (4.5 

lblgal) of primer (less water and 

exempt solvents) as applied for 

general aviation rework facilities. 
Process Unit 

Primer and Topcoat 

Uncontrolled Coatings - 

Topcoats 

40 CFR 63.745(c) 

Table 4-1. 40 CFR 63 Subpart GG Summary 

Primer and Topcoat 

Coatings - Primers and 

Topcoats 

40 CFR 63.745(d) 

Equipment 1 

Parameter 

HAP & VOC 

Pollutant I 1 Emission Limit I Standard (Units) I 

Organic HAP emissions fiom 

topcoats shall be limited to an 

organic HAP content level of no 

more than: 420 g/L (3.5 lblgal) of 

coating (less water) as applied or 

540 g/L (4.5 lblgal) of coating (less 

water) as applied for general 

aviation rework facilities. 

I Organic HAP emissions ikom selfpriming topcoats shall be limited to 

an organic HAP content level of no 

more than: 420 g/L (3.5 Iblgal) of 

self-priming topcoat (less water) as 

applied or 540 g/L (4.5 lblgal) of 

self-priming topcoat (less water) as 

applied for general aviation rework 

facilities. 

VOC emissions hm topcoats shall 

be limited to a VOC content level of 

no more than: 420 g/L (3.5 Iblgal) of 

coating (less water and exempt solvents) as applied or 540 g/L (4.5 

Iblgal) of coating (less water and 

exempt solvents) as applied for 

general aviation rework facilities. 

VOC emissions hm self-priming 

topcoats shall be limited to a VOC 

content level of no more than: 420 

g/L (3.5 Iblgal) of self-priming 

topcoat (less water and exempt 

solvents) as applied or 540 g/L (4.5 

lblgal) of self-priming topcoat (less 

water) as applied for general 

aviation rework facilities. 

Each control system shall reduce the 

operation's organic HAP and VOC 

emissions to the atmosphere by 8 1 % 

or greater, taking into account 

cahe and destruction or removal 

efficiencies. 
Table 4-1. 40 CFR 63 Subpart GG Summary 

Application Methods 

40 CFR 63 63.745(f) 

Equipment I 

Process Unit 

Primer and Topcoat 

primers and topcoats (including selftopcoats) shall be applied 

using one or more of the approved 

application techniques listed in 40 

CFR 63.745(f)(l). 

Pollutant 1 I Emission Limit I Standard (Units) 

All application devices used to apply 

primers or topcoats (including selfpriming topcoats) shall be operated 

according to company procedures, 

local specified operating procedures, 

andfor the manufacturer' s 

specifications, whichever is most 

stringent, at all times. Equipment 

modified by the facility shall 

maintain a transfer efficiency 

equivalent to HVLP and electrostatic spray application techniques. 

Parameter 

HAP & VOC For non-exempt applications, all 
Process Unit 

Primer and Topcoat 

Inorganic HAP Emjssions 

Existing Sources 

Table 4-1. 40 CFR 63 Subpart GG Summary 

Non-exempt application 

Equipment 1 

methods 

40 CFR 63.745(g) 

Pollutant 1 I Emission Limit I Standard (Units) 

Parameter 

Inorganic HAP Apply these coatings in a booth or 

hangar in which air flow is directed 

downward onto or across the part or 

assembly being coated and 

exhausted through one or more 

outlets. 

Control the air stream fiom this 

operation as follows: (i) For existing 

sources, the owner or operator must 

choose one of the following: 

(A) Before exhausting it to the 

atmosphere, pass the air stream 

through a dry particulate filter 

system certified using the methods 

described in$63.750(0) to meet or 

exceed the efficiency data points in 

Tables 1 and 2 of 65.745(g); or 

(B) Before exhausting it to the 

atmosphere, pass the air stream 

through a waterwash system that 

shall remain in operation during all 

coating application operations; or 

(C) Before exhausting it to the 

atmosphere, pass the air stream 

through an air pollution control 

system that meets or exceeds the 

efficiency data points in Tables 1 

and 2 of 65.745(g) and is approved 

by the permitting authority. 
Table 4-. 

Equipment I 

Process Unit 

Primer and Topcoat 

Inorganic HAP Emissions 

New Sources 

Non-exempt application 

methods 

40 CFR 63.745(g) 

Depainting Operations 

Non-HAP-Based Chemical 

Strippers 

Non-exempt applications 

40 CFR 63.746(b) 

40 CFR 63 Subg 

Pollutant I 

Parameter 

Inorganic HAP 

HAP 

rt GG Summary 

Emission Limit I Standard (Units) 

Before exhausting it to the 

atmosphere, pass the air stream 

through a dry particulate filter 

system certified using the methods 

described in $63.750(0) to meet or 

exceed the efficiency data points in 

Tables 3 and 4 of 63.745(g); or 

Before exhausting it to the 

atmosphere, pass the air stream 

through an air pollution control 

system that meets or exceeds the 

efficiency data points in Tables 3 

and 4 of 63.745(g) and is approved 

by the permitting authority. 

Each owner or operator of a new or 

existing aerospace depainting 

operation subject to this subpart 

shall emit no organic HAP from 

chemical stripping formulations and 

agents or chemical paint softeners. 
Process Unit 

Depainting Operations 

Organic HAP-Based 

Chemical Strippers 

Non-exempt applications 

40 CFR 63.746(c) 

Table 4-1. 40 CFR 63 Subpart GG Summary 

Chemical Milling Maskant 

Application Operations 

Housekeeping 

40 CFR 63.747(b) 

Equipment 1 

Parameter 

HAP 

Pollutant / I Emission Limit I Standard (Units) I 

HAP & VOC 

All organic H&' emissions fiom the 

operation shall be reduced by the use 

of a control system. Each control 

system that was installed before the 

effective date shall reduce the 

operations' organic HAP emissions 

to the atmosphere by 81 percent or 

greater, taking into account capture 

and destruction or removal 

efficiencies. 

Each control system installed on or 

after the effective date shall reduce 

organic HAP emissions to the 

atmosphere by 95 percent or greater. 

Reduction shall take into account 

capture and destruction or removal 

efficiencies, and may take into 

account the volume of chemical 

stripper used relative to baseline 

levels (e-g., the 95 percent efficiency 

may be achieved by controlling 

emissions at 81 percent efficiency 

with a control system and using 74 

percent less stripper than in baseline 

applications). The baseline shall be 

calculated using data fiom 1996 and 

1997, which shall be on a usage per 

aircraft or usage per square foot of 

surface basis. 

Conduct the handling and transfer of 

chemical milling maskants to or 

fiom containers, tanks, vats, vessels, 

and piping systems in such a manner 

that minimizes spills. 
Table 4-1. 40 CFR 63 Subn 

1 Equipment I I Pollutant I 

Uncontrolled Maskants 1 

Process Unit 

Chemical Milling Maskant 

Non-exempt Operations 

40 CFR 63.747(c) 

Parameter 

HAP & VOC 

Chemical Milling Maskant 

Uncontrolled Maskants 

Control System 

Requirements 

40 CFR 63.747(c) 

Handling and Storage of 

Waste 

40 CFR 53.748 

HAP & VOC 

HAP 

art GG Summary 

Emission Limit I Standard (Units) 

Organic HAP emissions fiom 

chemical milling maskants shall be 

limited to organic HAP content 

levels of no more than 622 grams of 

organic HAP per liter (5.2 lblgal) of 

Type I chemical milling maskant 

(less water) as applied, and no more 

than 160 grams of organic HAP per 

liter (1 -3 lblgal) of Type 11 chemical 

milling maskant (less water) as 

applied. 

VOC emissions from chemical 

milling maskants shall be limited to 

VOC content levels of no more than 

622 grams of VOC per liter (5.2 

lblgal) of Type I chemical milling 

maskant (less water and exempt 

solvents) as applied, and no more 

than 160 grams of VOC per liter (1.3 

lblgal) of Type I1 chemical milling 

maskant (less water and exempt 

solvents) as applied. 

Each control system shall reduce the 

operation's organic HAP and VOC 

emissions to the atmosphere by 8 1% 

or greater, taking into account 

capture and destruction or removal 

efficiencies. 

Conduct the handling and transfer of 

waste to or fiom coi&ners, tanks, 

vats, vessels and piping systems in 

such a manner that minimizes spills.