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Air Compressors


#1

Hello everybody: I am looking to buy an air compressor for my
sandblaster. At this point I don’t have a wax injector but I wil
be buying one in the future. I have two questions 1. Regarding
the brand name of the compressor, I am looking at a Coleman 2hsp
4 gallon tank versus a Campbell Housfield compressor with the
same horsepower and tank size. I have heard bad things about the
Campbell Housfield compressor but it has the longer warranty.
Does anyone have any experience with either of these two
compressors? 2. Capacity that I will need. With the sandblaster
I only need a 1/2 hsp motor with a small tank, I figured that if
in the future I would possibly be running both machines it would
be better to buy a bigger machine to compensate for this, I
figured that I needed double the size. If anyone has any
suggestions It would be greatly appreciated.

Cary James
Cary James Designs
P.O. Box 336 Manuels,Nfld
A1W 1M9


#2

Cary: The best way to measure the performance of an air
compressor is by how many cubic feet per minute of air and at
what pressure a pump will produce. This varies broadly among
compressors of the same horsepower.

Most air tools are rated for air consumption. You also need to
realize that air compressors should only run about 30 minutes per
hour of continuous usage to supply the amount of air you need
otherwise they overheat. The volume of the pump output and the
size of the tank all figure into this equation.

I bought a compressor that I thought was overkill only to find
out that it just meets my minimum requirements. When it comes to
compressed air, you can never have to much. All the more reason
to do the math before purchasing. Also consider future needs.

Kenneth Gastineau


#3

Hi Cary,

 Capacity that I will need.  With the sandblaster I only need a
1/2 hsp motor with a small tank,  I figured that if in the
future I would possibly be running both machines it would be
better to buy a bigger machine to compensate for this, I
figured that I needed double the size. 

The size of your compressor should be based on the requirements
of the tools, applications it will be used with. In the US, most
pneumatic tools list the air consumption in terms of cubic feet
per minute (cfm) and maximum pressure, pounds per square inch
(psi). In other counties other units of measurement are used,
but the idea’s the same, a way to measure volume of air used per
unit of time & maximum pressure. Check the specifications of the
tools you want to use with the compressor. If they require
different pressures (psi), use the highest pressure. If more
than 1 tool will be used at a time, add the cfm requirements of
all tools. Double the cfm requirements for safety.

To power a tool, a compressor must be capable of producing air
at the require volume (cfm) and pressure (psi). The 2
requirements are at opposite extremes, as the required pressure
goes up the compressor’s ability to produce the volume at that
pressure goes down (and vice versa).

Using sandblaster is similar to keeping a compressed air hose
open (to the size of the nozzle) 100% of the time. This
application requires lots, cfm, of air. A wax injector on the
other hand, requires a relatively small amount (about 1 cu. ft.)
of air, just enough to pressurize the wax pot to a given
pressure.

One characteristic of compressors with small tanks and low cfm
outputs, is they run a lot. The compressor running for extended
periods can be annoying and the unit may not be rated for that
large a duty cycle. Some may not be able to keep up with the cfm
requirements of sand blasters.

The horsepower rating of a compressor is an indication of the
maximum pressure & cfm output. The lower the hp rating the lower
the capacity of the compressor. Getting the larger hp (within
reason) unit will prevent future frustration when using it.

Sandblasting requires the use of ‘dry air’. When air is
compressed, it looses some of the moisture it was holding. This
moisture accumulates in the compressor tank as water. If not
drained periodically, you may get water mixed with the air &
this ‘wet air’ might affect the performance of the tools being
used. Be sure the compressor tank has a drain valve on it. The
drain valves are usually located on the low spot of the tank.

Sorry, I can’t give you any personal use reccomendations for
Coleman of CH, I use a larger industrial type compressor.


#4

Hi Roxana, A few things to consider about compressors. What is
its duty cycle; 50% to 100%?(time running to charge tank) How
many cubic feet per minute @ what pressure delivery? What is the
sandblasters’ air requirement? ALSO how noisy is it? Many
small compressors are LOUD and annoying. A high speed
compressor will not last(1500rpm or more) as long as a slow
speed(500 t0 800rpm.) If your use is only occasional you can
skip this consideration. A ten gallon storage tank can be added
in line to increase system capacity for $50 to $75. I have run a
lg wax injector on my small compressor with ease for years(3/4hp
$ gal tank w/10gal additional storage.) I also run my Gravermax
on this system. For Sandblasting I use a 6.5hp w/60gal tank,
light to medium duty(running about 25% of the time in use
cycle.)

Marcus Amshoff