AIRCRAFT BEARING CLEANING

Revision Date: 4/04
Process Code: Navy/Marines: IND-002-09; Air Force: CL01; Army: CLD
Usage List: Navy: High; Marines: None; Army: None; Air Force: None
Alternative For: Chlorofluorocarbon (CFC)-12 vapor degreaser
Compliance Impact: Low
Applicable EPCRA Targeted Constituents and CAS Numbers: Freon (CAS: 76-13-1), Naphtha (CAS: 8030-30-6), Stoddard solvent (CAS: 8052-41-3), and 1,1,1-Trichloroethane (CAS: 71-55-6)
Overview: Naval Aviation Depot (NADEP), North Island, California, in association with the Navy Environmental Leadership Program (NELP), evaluated and implemented an alternative cleaning system that meets established military cleaning requirements to use while refurbishing aircraft bearings. The system uses Isopropyl alcohol (IPA)/Cyclohexane vapor degreasing as an alternative to solvent cleaning.

Stoddard solvent (PD-680), 1,1,1-Trichloroethane [1,1,1, TCA, Class I ozone-depleting substance (ODS)], and L&R-222 (Stoddard solvent and naphtha) are typically used to clean aircraft bearings during refurbishment. The cleaning process uses a cascading line of solvent immersion tanks to remove grease, oil, and carbon from the bearings. Following the cleaning process, a thin, residual solvent film remains on the bearings, which must be removed, according to the drying standards, before refurbishing can continue. Normally, the residual film is removed using a Class I ODS (FreonŽ, CFC-12) vapor degreaser.

The IPA/cyclohexane vapor degreaser eliminates the use of ODSs. The system uses IPA and cyclohexane as an alternative to the Stoddard solvent cleaning system. The IPA/cyclohexane system is a self-contained immersion cleaner with a wash sump, an ultrasonic rinse sump, and an offset boil sump. The cleaning process involves immersing the bearings in a bath of IPA vapor. The vapor condenses on the bearings and flushes the surface clean of contaminants. When the bearing is withdrawn, cooling coils flush any residual IPA off the bearings.


Compliance Benefit: Switching to the IPA system decreases the amount of hazardous waste generated from aircraft bearing cleaning since there is no waste solvent generated. The reduction of hazardous waste helps facilities meet the requirements of waste reduction under RCRA (40 CFR 262) and Executive Order 13148. It may also help facilities reduce their generator status and lessen the amount of regulations (i.e., record keeping, reporting, inspections, transportation, accumulation time, emergency prevention and preparedness, and emergency response) they are required to comply with under RCRA (40 CFR 262). Additionally, the IPA system uses less chemicals than the freon system thereby decreasing a facility's chance of meeting reporting thresholds for hazardous chemicals under SARA Title III (40 CFR 355, 370, and 372) and EO 13148. Since ODSs, such as TCA and CFC-12, are not used in the IPA system, using this alternative technology will also help facilities meet the requirements under 40 CFR 82, Subpart D and EO 13148 requiring federal agencies to maximize the use of safe alternatives to Class I and Class II ODSs. Furthermore, a facility would decrease the likelihood that they would need to meet the National Emission Standards for Hazardous Air Pollutants (NESHAP) for halogenated solvent cleaning (40 CFR 63) if it switches to an IPA system. The facility may also decrease the need to require an air permit under Title V (40 CFR 70 and 71) since there may be a decrease in VOC emissions.

The compliance benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g., the amount of workload involved.
Materials Compatibility:


 No materials compatibility issues were identified.
Safety and Health: Consult your local industrial health specialist, your local health and safety personnel, and the appropriate material safety data sheet (MSDS) for specific precautions and proper procedures to implementing this technology.


Benefits:
  • Meets established drying standards and eliminates the use of a Class I and Class II ODS.
  • Helps the Department of Defense achieve ODS phase-out goals.
  • Reduces cost.
  • Reduces hazardous waste generation and overall air emissions.
  • Reduces operating labor.
  • Reduces worker exposure potential to toxic fumes.

 
Disadvantages:
  • Requires large initial investment.
  • Uses flammable solvents (IPA/cyclohexane).
Economic Analysis: The following cost elements compare replacing a CFC-12 vapor degreaser with an IPA/cyclohexane vapor degreaser.

Assumptions:

  • Capital and installation costs include cost for equipment purchase, construction labor and materials, permits, and operator training.
  • Operational and maintenance (O&M) costs include the following:
    • Utilities and consumables including electricity, fuel, water, wastewater treatment, compressed air, and solvents.
      • Freon system uses 2,184 lb./yr. of the Stoddard solvent
      • IPA/cyclohexane system uses 313 lb./yr. of virgin IPA/cyclohexane
    • Waste disposal includes the following:
      • Freon system: 4,118 lb./yr. of chlorinated and non-chlorinated solvent
      • IPA/cyclohexane system: 245 lb./yr. of oil and grease and approximately four spent filters.
    • Labor and overhead include the following operating and maintenance labor:
      • Freon system: 12 hr./day for about $25 per hour
      • IPA/cyclohexane: 1.33 hr./day for about $25 per hour
    • Maintenance parts and supplies include damaged parts and supplies required during maintenance

Table 1. Cost Comparison for IPA Vapor Degreaser versus Freon Vapor Degreaser

 

IPA System

Freon System
Capital and Installation Costs: $110,000 $0
Operational Costs:    
Utilities and Consumable: $2,938 $2,277

Waste Disposal:

$255 $4,282
Labor and Overhead: $9,303 $81,432
Maintenance Parts & Supplies: $2,208 $200
Total Costs: (not including capital and installation costs) $14,704 $88,191
Total Income: $0 $0
Annual Benefit: -$14,704 -$88,191

Economic Analysis Summary:

    Annual Savings for IPA System: $73,487
    Capital Cost for Equipment/Process: $110,000
    Payback Period for Investment in Equipment/Process: 1.5 yrs.

Click Here to view an Active Spreadsheet for this Economic Analysis and Enter Your Own Values. To return from the Active Spreadsheet, click the Back arrow on the Tool Bar.


NSN/MSDS:
Product NSN Unit Size Cost MSDS*
A-Prime 2S Precision Cleaning System None Identified N/A $N/A N/A
Portable Solvent Tank None Identified N/A $N/A N/A
CO2 Gas Cylinder Chiller None Identified N/A $N/A N/A

*There are multiple MSDSs for most NSNs. The MSDS (if shown above) is only meant to serve as an example.


Approving Authority: Appropriate authority for making process changes should always be sought and obtained prior to procuring or implementing any of the technology identified herein.


Points of Contact: For more information
Vendors: This is not meant to be a complete list, as there may be other manufacturers of this type of equipment.

Forward Technology, A Crest Group Company
Precision Cleaning Division
3050 Ranchview Lane North
Minneapolis,  MN   55447
Phone: (763) 559-1785
Fax: (763) 559-3929
Home Page: http://www.forwardtech.com/


Related Links:

Do You Degrease, Clean And Dry Precision Bearings?, Navy Environmental Quality Initiative (EQI)
IPA/Cyclohexane Vapor Degreaser, Pollution Prevention Equipment Program (PPEP) Book


Sources: Navy Environmental Leadership Program
Supplemental: Picture of Aircraft Bearing Cleaning using an IPA Vapor Degreaser

Picture of Aircraft Bearing Cleaning using an IPA Vapor Degreaser