| Overview: |
High and medium pressure
water blast systems are used for paint stripping surfaces with low-volume
water streams at pressures ranging from 3,000 to 15,000 psi (medium pressure
operations), and from 15,000 to 55,000 psi (high-pressure operations).
The medium pressure systems may be augmented with blast water additives
and/or surface treatments. For example, sodium bicarbonate may be added
to the water stream, or environmentally compliant chemicals may be applied
to painted surfaces prior to water blasting. High-pressure systems typically
use pure water streams. With both medium and high-pressure water systems,
specialized nozzles can be used to achieve effects ranging from a relatively
gentle, layer-by-layer removal of organic paints to removal of metal flame
spray coating and other tough, tightly adherent coatings. The process
water, paint, and residue are collected by the effluent-recovery system
for filtering the paint and residue, removing leached ions (copper, cadmium,
lead, etc.), microparticulates, chlorides, sulfates, nitrates, and other
contaminants. The water is passed through a coalescing tank to remove
oils and film, a through charcoal filter, microfilters and, finally, a
deionization system to ensure that the water is Type IV or better deionized
water. The recovered deionized water is recycled back into the process.
Currently, WR-ALC
at Robins AFB uses a medium pressure water system (12,000 - 15,000 psi).
The system is used for coating removal on the C-5, C-130, and F-15 aircraft
and also some off-aircraft components. The system is used with either
a non-hazardous air pollutant chemical remover, sodium bicarbonate blast
media, or by itself depending on the coating being removed.
|
| Compliance
Benefit: |
Use of high and medium
pressure water paint stripping as a replacement for chemical paint strippers
results in the following compliance benefits:
- Elimination or
reduction of volatile organic compounds (VOCs) used as strippers, which
are associated with the formation of smog typically regulated by state
and local air pollution control districts.
- Elimination or
reduction of hazardous air pollutants (HAPs) in strippers which are
regulated by federal, state, and local regulations including the National
Emissions Standards for Hazardous Air Pollutants (NESHAPs) (40 CFR
63).
- Elimination or
reduction of SARA Title III reporting (40 CFR 300, 355, 370, and
372; and EO 13148).
- Reduced volumes
of organic wastes, which must be managed as hazardous waste under 40
CFR 260 and related sections.
- Reduced potential
for release of hazardous substances in reportable quantities (40
CFR 110 and 302).
- Reduced occupational
exposures, which are regulated under 29 CFR 1910.
- Decreased water
use as required under EO 12902.
Compliance benefits
include: 1) reduced recordkeeping and reporting requirements under the
Clean Air Act Title V Operating Permits Program, NESHAPs Program, and
SARA programs, 2) reduced administrative burden associated with hazardous
waste (i.e., tracking, plans, reports, training), and 3) reduced administrative
burden associated with OSHA (i.e., training and recordkeeping).
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 material compatibility
problems have been documented for use of high and medium pressure water
processes to de-paint metallic surfaces. However, according to Mr. Randy
Ivey, Materials Engineering (WR-ALC/TIEDM) medium and high-pressure water
streams can damage composite and honeycomb thin skinned materials. The
use of specific chemicals to augment medium pressure water processes must
be evaluated on a case-by-case basis.
|
| Safety
and Health: |
Proper design, operation,
and maintenance of the equipment is required for its safe use. Proper
personal protective equipment is also recommended.
Consult your local
industrial health specialist, your local health and safety personnel,
and the appropriate MSDS prior to implementing this technology.
|
| Benefits: |
- Reduces hazardous
waste by 90%
- May be adjusted
to Sselectively removes individual coating-layers
- Pre-washing and
masking is not needed in most applications
- No size limitations
for parts being stripped
- Process water
reclamation units capture removed paint and recirculate water.
- Wastewater stream
compatibility with industrial wastewater plants must be determined on
a case-by-case basis taking into account the characteristics of the
waste stream and plant's capability.
- Low implementation
cost utilizing simple robust equipment
- Reduces the process
material costs significantly
- Reduces labor
hours for the stripping process by 50%
- No dust or airborne
contaminants generated
- Requires no cleanup
after stripping
- Specific additives
will control flash rusting and give long term portection.
|
| Disadvantages: |
- High capital
costs
- May not remove
corrosion
- The characteristics
of the coatings to be removed may impact personal protection and waste
collection/disposal considerations
- Coating debris
sludge is a potential hazardous waste
- Wastewater disposal
requirements depend on the toxicity of the coating being removed
- Workers must
be protected from direct impingement of the water jet
- Operator training
is required
- Water can penetrate
and/or damage joints, seals, and bonded areas
- Additives to
the water may have an adverse effect (i.e., flash rusting) on the surfaces
being cleaned
- Stripping rate
varies with the type of paint, coating condition and coating thickness
- This technique
is not appropriate for composite or honeycomb thin skinned materials
- The medium pressure
water stripping process works well as a supplement to chemical paint
stripping, but is not recommended as a stand alone paint removal process
for complete aircraft stripping. It has many successful applications
as a part/component stripping process. Medium pressure water without
abrasive additives, such as sodium bicarbonate, does not always remove
paint completely. High-pressure water is not a technology that has proven
effective for off-aircraft component paint stripping. Capital investment
for high pressure water paint stripping is cost prohibitive.
|
| Economic
Analysis: |
The
capital cost for high and medium pressure water processes will vary considerably,
depending upon the process and its application. Capital costs for medium
pressure systems range from $40,000 to $70,000 and capital costs for high-pressure
systems range from $850,000 to $1,500,000. According to PRO-ACT, the cost
of water is an integral part of the process and potential savings due to
recycling and elimination of surface washing following chemical paint stripping.
|
| Assumptions:
|
- 3 aircraft will
be de-painted per month
- External paint
area of each aircraft: 937.8 ft2
- Strip rate for
one aircraft: 2 ft2/min for Water Process, 0.22 ft2/min for
Chemical Process
- Labor rate: $30/hr
- Electricity:
$0.08/kw-hr
- Paint and solvent
sludge disposal cost: $4/gal
- Dry paint waste
disposal cost: $2/lb
Water Process
- Total labor requirements
for one aircraft: 7.8 hr/aircraft
- Material costs:
$445/aircraft
- System electrical
requirements: 907 kw-hr/aircraft (see attached note JLR)
- System maintenance
cost: $311/aircraft
- Dry paint waste
residue: 30 lb/aircraft
Chemical Process
- Total labor requirements
for one aircraft: 71 hr/aircraft
- Chemical procurement
cost: $10/gallon
- Chemical consumption
for a 937.8 ft2 aircraft: 35 gallons/aircraft or $350/aircraft
- Paint and solvent
waste: 87 gal/aircraft
Annual
Operating Cost Comparison for High Pressure Water Paint Stripping and
Chemical Paint Stripping
| |
Water Stripping
|
Chemical
Stripping
|
|
Operational
Costs:
|
|
|
|
Labor:
|
$8,400
|
$76,700
|
|
Material
|
$16,000
|
$12,600
|
|
Energy
|
$2,600
|
$0
|
|
Waste Disposal
|
$2,200
|
$12,528
|
|
System Maintenance:
|
$11,200
|
$0
|
|
Total Operational
Costs:
|
$38,200
|
$101,828
|
|
Total Recovered
Income:
|
$0
|
$0
|
|
Net Annual
Benefit/Cost:
|
-$38,200
|
-$101,828
|
| Economic
Analysis Summary |
| Annual Savings
for Water Stripping: |
$63,628 |
| Capital Cost
for Diversion Equipment/Process: |
$1,175,000 |
| Payback Period
for Investment in Equipment/Process: |
<19 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: |
Medium pressure water
paint removal is an approved process in T.O.1-1-8. However, use of this
process requires approval by the engineering authority of the specific
Weapon System manager and Equipment Item Manager. High-pressure water
paint removal systems are not recommended by the Air Force corrosion Program
Office and technical guidance for the process is not provided. Use of
this process must be approved by the engineering authority of the specific
Weapon System Manager and Equipment Item manager.
For Air Force applications,
high and medium pressure water paint stripping 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.
|
| NSN/MSDS: |
|
Product
|
NSN
|
Unit
Size
|
Cost
|
|
Hi-Press.
Water Gun Cleaner
|
4940-01-413-5600
|
ea.
|
$2,421.05
|
|
10-100
Hose
|
Pending
|
ea.
|
$822.60
|
|
| Points
of Contact: |
Navy:
Mr. Scott Mauro
Naval Facilities Engineering Service Center, ESC 423
1100 23rd Avenue
Port Hueneme, CA 93043-4370
Phone: (805) 982-5318, DSN: 551-5318, Fax: (805) 982-4832
Email: maurosm@nfesc.navy.mil
Air Force:
Mr. Larry Garrett or Mr. Richard Slife
Materials Engineering (WR-ALC/TIEDM)
420 2nd Street, Suite 100
Robins AFB, GA 31098
Phone: (912) 926-4489, DSN: 468-4489, Fax: (912) 926-1743
Air Force Corrosion
Prevention and Control Office
AFRL/MLS-OLR (Bldg. 165)
325 2nd Street
Robins AFB, GA 31098-1640
Phone: (912) 926-3284, DSN: 468-3284
|
| Vendors: |
The following is
a list of high and medium pressure water system vendors. This is not meant
to be a complete list, as there may be other manufacturers of this type
of equipment.
Aqua Miser®
Carolina Equipment and Supply
Mr. Chris Fulmer
7251 Cross County Rd.
N. Charleston, SC 29418
Phone: (800) 394-4987, (803) 760-3000, Fax: (803) 760-3500
(Medium pressure water systems)
O'Connell Jetting
Systems
Mr. Mike Richardson
3195 "H" Park Road
Benicia, CA 94510
Phone: (800) 320-4848, (707) 747-4848, Fax: (707) 747-6372
NLB Corporation
29830-T Beck Road
Wixom, MI 48393 2824
Phone: (800) 394-4587, (248) 624-5555, Fax: (248) 624-0908
|
| Sources: |
N/A
|
