User Manual

Additional Considerations 27
TIER 4 MAINTENANCE
Most typical 185 cfm/90-100 psi tow-behind air compressors feature
diesel engines small enough that they do not require diesel exhaust
fluid, or a diesel particulate filter to clean exhaust emissions. But be
sure to understand specific diesel engine maintenance requirements
before heading down the highway.
For systems that require diesel exhaust fluid, the reservoir will
probably need to be filled once for every few tanks of diesel fuel
burned. Diesel particulate filters may need periodic regeneration to
burn off the accumulated soot inside the filter. On some models, this
may require ceasing work until the regeneration is complete.
SAFETY EXCESS FLOW CHECK VALVES
Another way to prevent hose whip is to install a safety excess flow
check valve, sometimes called an air fuse. OSHA requires an air fuse
on any hose with an inside diameter (ID) greater than 1/2-inch.
See OSHA Standard OSHA 29 CFR 1926.302 (b) (7).
Installed at the output of the air compressor, should the air fuse
detect a sudden drop in pressure, it closes shut and prevents
additional compressed air from entering the hose. Once tripped, air
fuses automatically reset once the fault in the air hose has been
corrected.
Air fuses are sized for the
pressure and flow rate required
by the air tools in use. One-size
does not fit all. Consequently,
air fuses are not a standard
feature supplied on tow-behind
compressors.
NOISE
Due to their gas or diesel engines, tow-behind air compressors
contribute to high noise levels when running on the job site. Most
compressors nominally operate in the 90 to 100 dBa range, with
some units generating up to 110 dBa. To keep noise levels safe and
within OSHA standards, under these conditions hearing protection is
mandatory. See OSHA Standard 29 CFR 1910.95.
In addition to mechanical noise, crack the output valve of any tow-
behind air compressor not connected to an air hose and the noise
generated by escaping air can be in excess of 120 dBa – a noise level
equivalent to a commercial jet at takeoff.
Products such as the Guardair Quiet-Test,
attach to the output of the compressor
and allow for testing the air
compressor at full flow,
while reducing noise
levels by 20 dBa.
For example, increasing the compressor output pressure (by say 30
percent to 117 psi) increases the air-jet force and exit momentum flux
(stress seen by the soil) but only nominally. Supplying higher pressure
to a supersonic nozzle designed to work at 90 psi actually de-focuses
the air-jet thereby degrading performance. In addition, operating the
air compressor at higher pressures will dramatically increase energy
(fuel) consumption.
AIR COMPRESSOR SAFETY
HOSE WHIP PREVENTION
Potentially hazardous links in any compressed air system are the
connections between the air compressor and the air hose, connections
between lengths of air hose, or the connection between the air hose
and the air tool. Should a coupling blow apart under pressure, the
loose end of the hose can whip around in a dangerous manner.
People have been killed this way.
Air hose restraint systems, such as WhipChek®, hold the two couplers
together, preventing them from flailing around should a break occur.
OSHA requires “positive means” such as these to secure the air tool
to the air hose. See OSHA Standard 29 CFR 1926.302 (b) (1).