| Overview: |
A
vacuum sanding system is essentially a dry abrasive blasting process (e.g.,
sand, steel, or plastic media blasting) with a vacuum system attached to
the blast head to collect the blast media and the removed coating material
(paint or rust). The unit then separates the used blast media from the removed
coating material. The remaining blast material is recycled for further use
and the coating material is disposed.
This system is designed to replace chemical paint stripping, and has three
added advantages. The first advantage is the collection of both the blasting
media [e.g. sand, plastic media blast (PMB) or other media] and the collection
of the waste coating material being removed. The second advantage is that
the media is separated from the waste material by a reverse pulse filter.
The media is reused in the system, thereby minimizing the quantity of medium
required. The third advantage is that, due to the confinement of the blast
material, this technology may be used where it is impractical to use traditional
sandblasting or chemical stripping.
This system is a stand-alone system, including the air compressor to drive
the system. It is portable (skid mounted) and can be moved by a forklift.
The air compressor is a trailer unit (2-wheeled).
If PMB is used as the media in the vacuum sanding system, the used media
can be passed through a reclamation system that consists of a cyclone centrifuge,
a dual adjustable air wash, multiple vibrating classifier screen decks,
and a magnetic separator. In addition, some manufacturers provide dense
particle separators as a reclamation system. The denser particles, such
as paint chips, 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 locate
a vendor that would "lease" the blast media to the base and then recycle
the media to recapture the metals. (See Plastic Media Blasting [PMB] Paint
Stripping Process.)
The effect this technology has on pollution prevention is that the portable
vacuum sander removes coatings and corrosion from composite or metal structures
while capturing the media and solid waste. Vacuum sanding may eliminate
airborne particulate matter and potential hazardous lead dust exposure.
When compared to chemical paint stripping, this technology eliminates the
generation of waste solvent.
Vacuum sanding has been used at NAVSTA Everett located in Everett, Washington.
The original application of this technology was to remove paint on asphalt
as well as for maintenance of large service pipelines leading to NAVSTA
Everett. When NAVSTA Everett de-paints pipelines on naval piers, the U.S.
EPA requires complete recovery of waste materials, making both traditional
sand or water blasting and chemical stripping impractical.
This is an abrasive blasting process and not associated with traditional
sanding using an abrasive paper. This system has potential applications
for paint removal on buildings/facilities and structures within the Air
Force. It has only very limited application for paint removal on aircraft
when used with plastic media. This system would be effective for accomplishing
selective area paint removal where paint-stripping facilities are not available.
The system would also work well to supplement other stripping methods, as
an example to remove paint from areas that were masked during paint removal.
|
| Compliance
Benefit: |
Use of a vacuum sanding
system will help a facility decrease the amount of stripping chemicals
used and stored on site and therefore, decreases the possibility that
the facility will meet reporting thresholds for those chemicals under
40 CFR 355, 370 and EO 12856. In addition, less hazardous waste
is generated in vacuum sanding compared to traditional sandblasting or
chemical stripping since the blast media can be reused. 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 regulatory burden under RCRA, 40
CFR 262 (i.e., record-keeping, reporting, inspections, transportation,
accumulation time, emergency prevention and preparedness, emergency response).
Moreover, the vacuum sanding system decreases a facility’s need to obtain
an air permit under 40 CFR 70 and 71.
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 sand or plastic media and blast waste associated with this process
pose no compatibility problems. Collection systems should not mix different
types of waste (i.e., pipeline paint and paint from asphalt) to ensure
the most economic disposal can be obtained for each. Prior to using plastic
media for de-painting operations, personnel should check applicable military
specifications [such as (MIL-P-85891)] and operations manuals for the
PMB systems. Some military specifications do not allow PMB for de-painting
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 on some
of the softer alloys used for aircraft components (e.g. magnesium).
|
| Safety
and Health: |
Airborne dust, which
is a major safety and health concern with any blasting operations, may
be eliminated using the vacuum blasting system. In order for the vacuum
system to be effective, the vacuum and blasting head must be kept in contact
with the material being stripped of paint or corrosion. Therefore, training
in the proper use of the equipment is essential. In addition, eye protection
and hearing protection are recommended.
Consult your local industrial health specialist, your local health and
safety personnel, and the appropriate MSDS prior to implementing this
technology.
|
| Benefits: |
- Improves personnel
safety - eliminates airborne particulate matter and potential lead dust
exposure hazard.
- May eliminate
the need for the use of respirators while blasting.
- Separates waste
material from blasting media, therefore, the media can be recycled
- Vacuum sanders
are versatile and can use multiple media types.
- Wastewater disposal
costs (typical in chemical paint stripping operations) are virtually
eliminated with vacuum sanding.
- Eliminates the
production of waste solvents when compared to chemical paint stripping
- Unit is portable
and contains a self-supplied power/air compressor
- Minimal emissions
from portable (mobile source) diesel air compressors, so no air permit
required.
- Minimizes the
clean up time since blast material is contained
- Other activities
can continue nearby without interruptions.
|
| Disadvantages: |
- Substantial capital
equipment investment is required
- Used blasting
materials and waste coating material may have to be disposed as a hazardous
waste
- Operator training
is critical to success and safety of operation
- Operator time,
maintenance requirements, handling, and disposal of waste varies upon
material to be stripped
- Quality of stripping
is dependent on skill and experience level of the operator
|
| Economic
Analysis: |
Vacuum
sanding systems can range in cost from $17,000 to $40,000, excluding the
portable generator to operate the system. The following information on investment
costs and costs/payback for a vacuum sanding system at NAVSTA Everett, Washington
was published in the Arthur
D. Little report Site Assessment Pollution Prevention Equipment at NAS North
Island SUBASE, Bangor, NAVSTA Pascagoula, and NAVSTA Everett, August 1995.
The following analysis compares a vacuum system to a traditional sand blasting
system (although the sand blasting system may not be able to be used based
on EPA constraints described in the overview).
Assumptions:
- Labor rate: Vacuum
Sanding (VS) and Traditional Sandblasting (TS) - $45/hr.
- Work load: VS
and TS - 7200 square feet de-painted per yr.
- Rate of de-painting:
VS and TS - 4 square feet per minute
- Total hours
per year including setup/operation/cleanup: VS - 40 hrs/yr; TS - 80
hr/yr.
- Materials: VS
- plastic media rental cost $2.50/lb, includes disposal of waste segregated
from media x 1,500 lbs/yr = $3,750/yr; TS -
material cost $1.50/lb x 1,500 lb = $2,250/yr.
- Disposal: VS
- $0; TS - $.60/lb x 15,000 lb + $36/drum x 25 drums = $9,900
- Utilities: VS
and TS - Diesel fuel $1.00/gallon x 60 gallons/yr = $60
- Equipment maintenance:
VS - $2,200; TS - $700
Annual
Operating Cost Comparison for Vacuum Sanding versus Sandblasting
| |
Vacuum Sanding
|
Sandblasting
|
|
Operational
Costs:
|
|
|
|
Labor:
|
$1,800
|
$3,600
|
|
Material:
|
$3,750
|
$2,250
|
|
Energy:
|
$60
|
$60
|
|
Waste Disposal:
|
$0
|
$9,900
|
|
System Maintenance:
|
$2,200
|
$700
|
|
Total Operational
Costs:
|
$7,810
|
$16,510
|
|
Total Recovered
Income:
|
$0
|
$0
|
|
Net Annual
Cost/Benefit:
|
-$7,810
|
-$16,510
|
Economic Analysis
Summary
Annual Savings
for Vacuum Sanding: $8,700
Capital Cost for Diversion Equipment/Process: $64,000
Payback Period for Investment in Equipment/Process: < 8 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 reverse arrow in the Tool Bar.
|
| Approving
Authority: |
For Air Force applications,
vacuum sanding system paint stripping process 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 Prevention and Control Office.
Currently, the Air Force provides no technical guidance on the use of
this type of equipment. However, this equipment may be employed wherever
abrasive blasting technology is approved for the coating removal process.
This would not require any engineering approval as long as the technical
requirements for the blasting process such as nozzle distance (12 to 24
inches), nozzle pressure, media type, etc., are met. Note: it would probably
require some significant design change to have a vacuum head to support
the nozzle distance and this would be very unwieldy for use on aerospace
equipment.
|
| NSN/MSDS: |
None identified.
|
| Points
of Contact: |
Air Force:
Air Force Corrosion Prevention and Control Office
AFRL/MLS-OLR (Bldg. 165)
325 Richard Ray Boulevard
Robins AFB, GA 31098-1640
Phone: (478) 926-3284
DSN: 468-3284
Email: AFCORR@ROBINS.MIL
Navy:
Penny Sue Jones
Puget Sound Naval Shipyard
Code 106.32
1400 Farragut Avenue
Bremerton, WA 98314
Phone: (360) 476-0127
DSN: 439-0127
FAX: (360) 476-8550
Email: jonesps@psns.navy.mil
|
| Vendors: |
Empire Abrasive Equipment
Company
2101 West Cabot Blvd.
Langhorne, PA 19047
Phone: (215) 752-8800
For PMB Leasing Services, See Plastic Media Blasting (PMB) Paint Stripping
Process.
This is not meant
to be a complete list, as there may be other suppliers of this type of
equipment.
|
| Sources: |
Mr. Brad Baum,
Baum & Associates, Inc., May 1996
Ms. Chris Mahendra, Naval Air Warfare Center, Lakehurst, NJ, May 1996
Ms. Penny Sue Jones, Puget Sound Naval Shipyard, February 2000.
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