| Overview: |
Plastic
Media Blasting (PMB) is a dry abrasive blasting process, designed to replace
chemical paint stripping operations and conventional sand blasting. This
process uses soft, angular plastic particles as the blasting medium, and
has proven more efficient than chemical paint removal.
PMB is performed
in a ventilated enclosure such as a small cabinet (glove box), a walk-in
booth, a large room, or airplane hanger. The PMB process blasts the plastic
media at a much lower pressure (less than 40 psi) than conventional blasting.
PMB is well suited for stripping paints, since the low pressure and relatively
soft plastic medium have virtually no effect on the surfaces beneath the
paint. PMB is currently authorized by NAVAIR for multiple uses down to
0.016-inch aluminum skins.
After blasting, the
media is passed through a reclamation system that consists of a cyclone
centrifuge, a dual adjustable air wash, multiple vibrating classifier
screen decks, a dense particle separator, and a magnetic separator. The
denser particles, such as paint chips, sand, grit, and aged sealant particles,
are separated from the reusable blast media, and the reusable media is
returned to the blast pot. Typically, media can be recycled ten to twelve
times before it becomes too small to remove paint effectively. Waste material
consists of blasting media and paint chips. The waste material may be
classified as a RCRA hazardous waste because of the presence of metals.
An alternative solution to handling a potential hazardous waste is to
contact one of the many vendors that will "lease" the blast media to the
facility and then use the waste media in the manufacturing process for
consumer products, such as bathroom sinks and plastic yard pots and benches.
Plastic media are
manufactured in 7 types and a variety of sizes and hardnesses. A military
specification (MIL-P-85891) has been developed for plastic media. The
specification provides general information on the types and characteristics
of plastic media. The plastic blasting media types are:
- Type I Polyester
(Thermoset)
- Type II Urea formaldehyde
(Thermoset)
- Type III Melamine
formaldehyde (Thermoset)
- Type IV Phenol
formaldehyde (Thermoset)
- Type V Acrylic
(Thermoplastic)
- Type VI Poly (allyl
diglycol carbonate) (Thermoset)
- Type VII Starch-g-acrylic
PMB facilities typically
use a single type of plastic media which they use for all of their PMB
work. The majority of DOD PMB facilities use either Type II or Type V
media. Type V media is not as hard as Type II media and is gentler on
substrates. Type V media is more commonly used on aircraft. Type II is
better for steel-only surfaces.
PMB facilities typically
use a single type of plastic media which they use for all of their PMB
work. The majority of DOD PMB facilities use either Type II or Type V
media. Type V media is not as hard as Type II media and is gentler on
substrates. Type V media is more commonly used on aircraft. Type II is
better for steel-only surfaces.
The pollution prevention
benefits of this technology as compared to sandblasting concern the reuse
of the blasting media, which greatly reduces the volume of spent media
generated. When compared to chemical paint stripping, this technology
eliminates the generation of waste solvent.
PMB is being used
at Puget Sound, Charleston, and Portsmouth Naval shipyards; Naval Aviation
Depots (NADEPs) North Island and Cherry Point; and Naval Surface Warfare
Center (NSWC) Indian Head, as well as other Navy activities and throughout
the Army and Air Force. Plastic media glove boxes and enclosed blasting
booths have been installed at depot and intermediate level aircraft maintenance
activities to remove paint from support equipment and components. A blast
media lease and recycle program is currently in place at many facilities,
including NADEP Cherry Point. A more detailed list of organizations within
the DOD depot maintenance community that have implemented PMB operations
is provided in Appendix III of Joint Paint Removal Study; Final Report
Plastic Media Blast, Joint Depot Maintenance Analysis Group, Technology
Assessment Division, June 1994.
|
| Compliance
Benefit: |
Use of plastic media
blasting paint stripping will help a facility decrease the amount of solvents
used and stored on site and therefore, decreases the possibility that
the facility will meet reporting thresholds for solvents under 40 CFR
355, 370 and EO 12856. In addition, plastic media blasting generates
less hazardous waste than traditional sand blasting operations. The decrease
in 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 their regulatory burden (e.g. recordkeeping,
reporting, inspections, transportation, accumulation time, emergency prevention
and preparedness, emergency response) under RCRA, 40 CFR 262. Moreover,
plastic media blasting uses less water and electricity than chemical depainting
operations in accordance with the requirements of EO 12902.
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: |
Storage and handling
of plastic media and blast waste associated with this process pose no
compatibility problems. Prior to using plastic media for depainting operations,
personnel should check applicable military specifications [such as (MIL-P-85891)]
and operations manuals for the PMB systems. Plastic media cannot be used
with a system designed for other types of media, without some important
modifications. Some military specifications do not allow PMB for depainting
certain types of materials (i.e. fiberglass, certain composites, honeycomb
sandwich structures, and some applications with thin-skinned aircraft
components). In certain cases, PMB can inhibit crack detection by fluorescent
penetrant inspection on some of the softer alloys used for aircraft components
(e.g. magnesium).
|
| Safety
and Health: |
As with any blasting
operations, airborne dust is a major safety and health concern. Proper
precautions should be taken to ensure that personnel do not inhale dust/particulate
matter. Additional protective measures should be taken when stripping
lead chromate- or zinc chromate-based paints, as these compounds may be
hazardous. Inhalation of lead and zinc compounds can irritate the respiratory
tract, and some compounds are known to be carcinogenic. Prolonged exposure
can affect respiration and the central nervous system. Operators must
wear continuous flow airline respirators in accordance with OSHA requirements
as specified in 29 CFR 1910.94 when blasting operations are in progress.
Consult your local
industrial health specialist, your local health and safety personnel,
and the appropriate MSDS prior to implementing this technology.
|
| Benefits: |
- Media can be recycled
(10-12 recycling events)
- Wastewater disposal
costs (typical in chemical paint stripping operations) are virtually
eliminated with PMB
- Eliminates the
production of waste solvents when compared to chemical paint stripping
|
| Disadvantages: |
- Substantial capital
equipment investment is required
- Quality of stripping
is dependent on skill and experience level of the operator
- Military specifications
do not allow PMB for depainting certain types of materials
- May not remove
corrosion products
- While this waste
may be exempt from Resource Conservation and Recovery Act (RCRA) regulation
as a hazardous waste, it may be classified as a hazardous material for
transportation purposes.
|
| Economic
Analysis: |
PMB
systems can range in cost from $7,000 for a small portable unit to $1,400,000
for a major facility for aircraft stripping. The following information on
investment costs and costs/payback for PMB systems at Hill AFB, Utah, was
provided in Joint Paint Removal Study; Final Report; Plastic Media Blast,
Joint Depot Maintenance Analysis Group, Technology Assessment Division,
June 1994. According to the Air Force Corrosion Program Office, the capital
cost for PMB for large aircraft (cargo) increases by orders of magnitude,
for example, $12,000,000 for C-5. In such cases, however, the cost savings
achieved by utilizing PMB versus chemical stripping do not increase proportionally,
so payback will not occur in two years as indicated in the following economic
analysis.
In 1987, Hill AFB
gathered data during the stripping of F-4 aircraft using chemical stripping
and PMB.
Assumptions:
- Labor rate: $45/hr.
- Work load = 75
aircraft/yr.
- Labor per airplane:
183 hrs for blasting, 364 hrs for chemical stripping.
- Chemical procurement
cost: $11.40/gallon.
- Chemical use per
airplane: 468 gallons.
- Plastic media
procurement cost: $1.76/lb.
- Plastic media
used per airplane: 1,500 lbs.
- Water treatment/disposal:
$8.24/1000 gallons.
- Water usage per
airplane: 200,000 gallons.
- Electricity usage
costs per airplane: PMB = $173; chemical stripping = $333.
- Paint and solvent
waste disposal: Paint and solvent waste disposal: 0.51 ton per airplane
at $2000/ton
- Spent media and
blast waste disposal: 0.85 ton per airplane at $260/ton.
- Water purchase
costs: $0.43/1000 gallons.
- Maintenance costs
per airplane: PMB = $1,333; chemical stripping = $667.
- Cost per airplane
to strip parts which can’t be done using PMB: $667.
Annual
Operating Cost Comparison for PMB and Chemical Stripping
|
|
| |
PMB
|
Chemical
Stripping |
| Operational
Costs: |
|
|
| Labor: |
$617,600 |
$1,228,500 |
| Chemical: |
$0 |
$400,100 |
| Plastic
Media: |
$198,000 |
$0 |
| Water
Treatment/ Disposal: |
$0 |
$123,600 |
| Electricity: |
$13,000 |
$25,000 |
| Hazardous
Waste Disposal: |
$16,600 |
$76,500 |
| Water: |
$0 |
$6,500 |
| Maintenance
Cost: |
$100,000 |
$50,000 |
| Cost
of parts not done by PMB: |
$50,000 |
$0 |
| Total
Operational Costs: |
$995,200 |
$1,910,200 |
| Total
Recovered Income: |
$0 |
$0 |
| Net
Annual Cost/Benefit: |
-$995,200 |
-$1,910,200 |
|
|
Economic Analysis
Summary
Annual Savings
for PMB: $915,000
Capital Cost for Diversion Equipment/Process: $1,400,000
Payback Period for Investment in Equipment/Process: < 1.5 years
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|
| Approving
Authority: |
PMB is not authorized
for use on aluminum and magnesium components that require a fluorescent
penetrant inspection. NAVAIR has authorized PMB use on metal substrates
under specific process control parameters at intermediate and depot level
activities. See NAVAIR 01-1A-509 for specific limitations. NAVAIR has
also authorized PMB for depainting certain carbon/epoxy composite structures
and some specific metal/honeycomb structures. NAVAIR has not authorized
PMB for depainting fiberglass and some specialized composites, including
carbon-bismaleimide layups. This recommendation should be implemented
only after engineering approval has been granted by cognizant authority.
For Air Force applications,
plastic media blasting must not be used on any aircraft or weapon systems
without the knowledge and approval of the appropriate system manager,
office(s) having engineering authority on the specific airframe(s) and
the Air Force Corrosion Program Office. This process is contained in T.O.1-1-8,
but the use of it requires approval by the engineering authority of the
specific Weapon System Manager or Equipment Item manager with in the Air
Force.
PMB equipment authorizations
are listed in the Air Force Table of Allowance (TA) 480. The following
PMB recycling statements of work (SOW) are available through PRO-ACT:
(a) "Statement of Work for Service Contract to Lease Plastic Media," prepared
by Ogden Air Logistics Center and (b) Composite Leasing Corporation Letter,
11 April 1996, which provides a service contract outline.
|
| NSN/MSDS: |
| Product |
NSN |
Unit
Size |
Cost |
MSDS* |
| Phenol
Formaldehyde (Abrasive Grain) |
5350-01-326-9942 |
50lb
bag |
$141.38
|
|
| Urea
Formaldehyde (Abrasive Grain) |
5350-01-326-8222 |
50lb
bag |
$85.05
|
Click me |
*There are multiple MSDSs for most NSNs.
The MSDS (if shown above) is only meant to serve as an example.
|
| Points
of Contact: |
Air Force:
Air Force Corrosion Prevention and Control Office
AFRL/MLS-OLR (Bldg. 165)
325 Richard Ray Blvd.
Robins AFB, GA 31098-1640
Phone: (478) 926-3284
DSN: 468-3284
Email: AFCORR@robins.mil
Henry Rodriguez
Nellis Air Force Base
99 CES/CEVP
4349 Duffer Drive
Suite 1601
Nellis AFB, NV 89191
Phone: (702) 652-6097
DSN: 682-6097
FAX: (702) 652-2021
Supervisory Materials
Engineer
Polymers/Composites/Testing Branch
AIR - 4.3.4.4
Mark Meno
Code 4.3.4.2
Naval Aviation Depot
PSC Box 8021
Cherry Point, NC 28533-0021
Phone: (252) 464-7166
DSN: 451-7166
FAX: (252) 464-8108
Email: menomd@navair.navy.mil
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| Vendors: |
This is not meant
to be a complete list, as there are other manufacturers of this type of
equipment.
Pauli System
1820 Walters Court
P.O. Box 2589
Fairfield, CA 94533
Phone: (707) 429-2434
FAX: (707) 429-2424
Schlick-America Inc.
P.O. Box 1028
Randallstown, MD 21133-0374
Phone: (410) 655-0770
FAX: (410) 521-0483
Contact: Mr. Bob Corcoran
Composite Leasing
Corporation, Inc.
P.O. Box 102
Minocqua, WI 54548
Phone: (800) 677-4568
FAX: (715) 356-3952
Contact: Mr. Brian Lund
Service: Leasing Services
Composition Materials
Company, Inc.
125 Old Gate Avenue
Milford, CT 06460
Phone: (800) 262-7763
FAX: (203) 874-6505
Service: Leasing Services
L.S. Solutions, Incorporated
P.O. Box 309
Deer Park, TX 77536
Phone: (281) 478-6522
FAX: (281) 478-6531
Service: Leasing Services
US Technology
220 7th St. SE
Canton, OH 44702
Phone: (800) 634-9185
Contact: Mr. Vince Librizzo
Service: Leasing Services
Solid Strip
P.O. Box 102
Minocqua, WI 54548
Phone: (800) 677-4568
FAX: (715) 356-3952
|
| Sources: |
Joint Paint Removal Study; Final Report;
Plastic Media Blast, Joint Depot Maintenance Analysis Group, Technology
Assessment Division, Dayton, Ohio; June 1994; (513) 296-8296.
N.E. Wasson, Jr., P.E., "Dry Stripping the C-5 and B-52 in the World’s
Largest Dry Stripping Installation", Proceedings of the Second Annual
AF Worldwide Pollution Prevention Conference, June 2, 1993.
Butch Green, LMTCE Code 343, Naval Aviation Depot, Naval Air Station Jacksonville,
June 1996.
Mark Meno, NADEP Cherry Point, July 1996 and November 1999.
Brian Lund, Solidstrip, Inc., June 1996.
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