| 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.
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 SARA Title III
(40 CFR 300, 355, 370, and 372) as well as Executive Order (EO) 13148,
Greening the Government Through Leadership in Environmental Management.
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;
the Pollution Prevention Act (42 USC 13101-13109); and EO 13148; 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 13123, Greening the
Government Through Efficient Energy Management.
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: |
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
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* |
| Plasti-Grit Type II Hard (MIL-P-85891) |
5350-01-326-9942 |
50lb bag |
|
Click
me |
| Plasti-Grit Type V (MIL-P-85891) |
5350-01-327-8460 |
50lb bag |
|
Click
me |
*There are
multiple MSDSs for most NSNs. The MSDS (if shown above) is only meant
to serve as an example. To return from the MSDS, click on the Back arrow on the Tool Bar.
|
| Approving Authority: |
Appropriate authority for making process changes should always be sought and obtained prior to procuring or implementing any of the technologies identified herein.
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.
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.
|
| 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.
Pauli System
1820 Walters Court
Fairfield, CA 94533
Phone: (707) 429-2434
FAX: (707) 429-2424
URL: http://www.paulisystems.com
Composite Leasing Corporation, Inc.
P.O. Box 102
Minocqua, WI 54548
Phone: (800) 677-4568 or (715) 356-7130
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 or (203) 874-6500
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
|
| Related Links: |
Do You Remove Paint Using Chemical Paint Stripping? - Navy Environmental Quality Initiative (EQI)
Plastic
Media Blast Booth - P2 Equipment Program
Glovebox Abrasive Blast Unit - P2 Equipment Program
|
| 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.
|
| Supplemental: |
Picture of
Plastic Media Blast Booth
Picture of Glove
Box Plastic Media Blaster
|
