|
When purchasing an air compressor,
allow for later growth, additional air equipment and for
"pressure drop" through your air hoses and
lines. We normally recommend twice as much capacity as
your present requirements. However, if you have a limited
budget, you can add another compressor at a later date.
When abrasive blasting within a
cabinet, the air requirement of the nozzle or air jet is
given in CFM. However, as blasting uses a continual supply
of air, you should either have twice the recommended
amount of air or plan on blasting on an intermittent
basis. If your compressor runs more than 2/3 of the time,
it is being overworked and will overheat and break down. A
compressor should NEVER run on a continual basis.
 In addition, the abrasive stream
rapidly enlarges the orifice size of the nozzle. In 4-8
hours, this nozzle will wear to the next size, requiring
even more air, increasing the overload on your air
compressor. The compressor runs harder and gets hotter as
this load increases.
All air contains a certain amount of
relative humidity. In coastal locations or on high
humidity days, this humidity is excessive. The temperature
of the air is increased as it is compressed. If a
compressor is running hard (continually running, without
recycling or resting), the air temperature will become
excessive, leading to the compressor tank becoming very
hot to the touch. This results in a breakdown of the oil,
with a resulting loss of efficiency. The only answer is to
allow the compressor to "rest" until it cools
down.
When running at high temperatures,
as the moist air is compressed and heated, it transforms
into a "vapor". This vapor-laden air will easily
pass through most water separators, eventually condensing
in the bottom of the abrasive blast cabinet funnel or
power gun where it is combined with the abrasive.
(Clogging results.) Also, as the nozzle orifice size
increases in size (gets larger) through wear, the
compressor works harder, puts out more moisture and the
pressure starts dropping because the compressor cannot
keep up with the increased load.
In summary, for satisfactory
operation when cabinet blasting or using any air tool
requiring large amounts of air, please observe the
following recommendations:
1. Change nozzles frequently --
consider going to a smaller size to save air, or using a
long-wearing Carbide Nozzle which will maintain its
orifice size for a longer period of time.
2. Do not blast continually. Take a
break
every 5 minutes to allow air compressor to cool.
3. If air compressor tank feels hot
(warm is normal), and is running continually, stop
operating the cabinet or air tool and allow compressor to
cool. Otherwise, compressor will overheat and eventually
break down. Compressors are not guaranteed against this
condition.
4. Compressor must recycle normally
on and off and run no more than 2/3 the time. No air
compressor is designed for continual operation. Know the
capacity of your compressor and the amount of air required
for your air tools, and allow a 50% overload factor for
best results. (Example: Tool requires 10 CFM air. You need
15 CFM as an overload factor.)
5. Use a minimum 3/8" ID air
hose up to 25 ft, from air compressor to cabinet. (Metal
piping is always preferred to air hose, as it allows the
moisture-laden air to condense in the piping, where it can
be removed later with the water separators. See LINK to
TIP TOOLS page for Metal
Piping Diagram.)
6. Keep abrasive and dust away from
the air compressor. Observe maximum air pressure
requirements for abrasive blast cabinet, and either set
your compressor to run within these limits or use a
pressure regulator valve (air regulator), to reduce the
air pressure to conform to the correct pressure
requirements.
7. Always wear NIOSH/OSHA approved
dust respirator and eye protection during operation, and
when loading or unloading parts or abrasive. Disconnect
air pressure from the unit before shutting down the unit
or servicing.
8. As a general rule when cabinet
blasting, use a small nozzle setup (4-8 cfm) for 3-5 HP
single-stage compressors and then only plan on blasting on
an intermittent basis (to allow proper cooling of the
compressor). Most popular nozzle setup is medium (10-15
cfm) for larger 5 HP air compressors putting out about
15-20 CFM air. The 15-20 CFM air will keep up with the
medium setup on a continual basis, but be sure to allow
compressor to rest by turning off the power gun
periodically. For 7-1/2 HP - 10 HP 2-stage air
compressors, a large nozzle setup is recommended (20-25
cfm).
9. Use only approved Air Compressor
Oil of the correct viscosity. This oil contains anti-foam
agents and is especially formulated for air compressor use
with rust, oil and oxidation inhibitors. Ordinary oil or
automotive-type oil will break down rapidly and result in
premature wear of inner parts. CHANGE OIL EVERY 100 HOURS
OF OPERATION.
*NOTE - Under extreme hard usage
where compressor runs hot, a higher viscosity oil is
recommended.
|
Solv
and Twin Etch. Having a large five foot long sand blasting
cabinet really helps in restoration, especially the doors, bumpers and
undercarriage parts. If you have space Scat
Blast model 970 cabinet from TIP Tools is just right for large items
like doors and fenders up to five feet in length. These cabinets are not
cheap for one time restorers but Tip Tools also sells part kits to make
your own. Various inexpensive cabinets can also be obtained from Harbor
Freight ( http://www.harborfreight.com
), Eastwood Automotive and other tool supply sources for limited budgets. Due to the large
volumes of air required, buy the largest compressor that you can afford 17
to 20 cfm or more, 60 to 80 gallon capacity tank. From my experience this
winter I would go for something around a 20 cfm compressor. Air
requirements go up when you get into pressure blasting outdoors. Use of
small home or shop type compressors can be used for limited duty time
requirements for small jobs.
