AIRCRAFT BEARING CLEANING

Revision Date: 8/01
Process Code: Navy/Marines: ID-02-09; Air Force: CL01; Army: CLD
Usage: Navy: High; Marines: None; Army: None; Air Force: None
Alternative for: Chlorofluorocarbon (CFC)-12 vapor degreaser
Applicable EPCRA Targeted Constituents: Freon (CAS: 76-13-1); Naphtha (CAS: 8030-30-6); Stoddard Solvent (CAS: 8052-41-3); 1,1,1-Trichloroethane (CAS: 71-55-6)
Overview: Naval Aviation Depot, North Island (NADEP), 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), 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 ozone-depleting substance (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 When the bearing is withdrawn, cooling coils flush any residual IPA off the bearings.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, Appendix, and 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, emergency response) they are required to comply with under RCRA, 40 CFR 262. Additionally, the IPA system uses less chemicals than the freon system which decreases a facility’s chance of meeting reporting thresholds for hazardous chemicals under SARA Title III (40 CFR 370 and Executive Order 12856). 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 Executive Order 12843 requiring federal agencies to maximize the use of safe alternatives to class I and class II ozone depleting substances, to the maximum extent practicable. Furthermore, a facility would decrease the likelihood that they would need to meet the NESHAP for halogenated solvent cleaning (40 CFR 63, subpart T) if it switches to an IPA system. The facility may also decrease the likelihood 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 a general guideline 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 OD.
  • Helps the Department of Defense (DOD) 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

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 reverse arrow in the Tool Bar.

 
Approving Authority:
Approval is controlled locally and should be implemented only after engineering approval has been granted. Major claimant approval is not required.

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


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

 

Points of Contact: Navy:
Mr. Ed Bonnes
Navy Environmental Leadership Program
NAS North Island
San Diego, CA 92135
Phone: (619) 524-6330
DSN: 524-6330
FAX: (619) 524-6519
Email: bonnes.ed.k@asw.cnrsw.navy.mil

 

Vendors: Forward Technology Inc.
Minneapolis,  MN   55441
Phone: (800) 369-1489 


Sources: Navy Environmental Leadership Program


 

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