11
Blast nozzle
The primary air consumption in a blast system is by the blast nozzle. This usage can vary greatly
depending upon the number of blast outlets, nozzle size of each outlet, and the blast pressure.
The nozzle consumption and other usages must be evaluated for maximum operating efficiency
of the AirPrep System. See Section 13.0, Table 1 for air consumption by nozzle size at various
pressures and then add the total usages to confirm that the AirPrep System capability is not
exceeded.
3.2
Air compressor size
The air compressor must be large enough to supply:
i.
The sum of blast air requirements for each nozzle at the highest pressure that will be
used (see Section 13.0, Table 1).
ii.
The 12 CFM breathing air supplied to each blast operator respirator.
NOTE
: Reference
OSHA regulations regarding requirements for breathing air, especially when an oil-
lubricated air compressor is used.
iii.
The AirPrep System size should be selected based on the size and capability of the air
compressor to be used.
3.3
AirPrep System Air Supply Lines
The air supply hose and fittings connected to the inlet and outlets of the AirPrep System must be
rated at a minimum of 150 psi operating pressure. The air supply hose from the air compressor to
the AirPrep System should be at least the same diameter as the air inlet piping (see Section 2.7).
AirPrep Systems are equipped with smaller secondary outlet ports which can be reduced in size
by installing pipe bushings to match the connecting equipment. Again the air requirement of the
connecting equipment must be considered so that the proper size piping/hose is selected. See
Section 5.14.
3.4
AirPrep System Air Pressure
The standard maximum operating pressure for AirPrep Systems is 150 psig; however custom
systems may have varying operating pressure. The maximum operating pressure for the AirPrep
System is stamped on the ASME nameplate attached to the vessel. AirPrep Systems equipped
with air motors to drive the cooling fan are supplied with an air pressure regulator. This air
regulator is to reduce the air pressure to the required operating pressure of the fan air motor. The
regulator is pre-set at the manufacturer and should not be altered. The required operating
pressure for the fan air motor is given in Section 11.0, Table 2.
3.5
Blast System Air Quality
AirPrep Systems are equipped with an inlet filter/separator to remove debris and condensed
moisture from the incoming air flow; however, if the air source contains an excessive amount of
debris it may be necessary to install a preliminary filter upstream of the AirPrep System inlet.
Excessive contamination of the incoming air can clog the heat exchanger of the AirPrep System
and cause expensive damage to the system.
3.6 Electrical
Requirements
AirPrep Systems can be equipped with electric fan motors. On units equipped with electric fan
motors the supply voltage can range from 110Vac (single phase) to 460Vac (three phase). Each
electric motor can be wired one of two voltages as specified by the purchaser at the time of