International F4370 Flatbed Truck w/ IR750 Compressor

DLT #:  TK2411
Model Year:  1979
Miles:  71917

    The Spiro-Flo series air compressor is a completely enclosed, single-stage compressor, directly connected to and driven by a diesel engine.  Special attention has been given to the aesthetic appeal of this unit.  The compressor is a positive displacement, cycloidal type.  The engine is a heavy-duty, industrial type, specially compressor-matched to provide optimum performance with the utmost in fuel economy.  The engine is operated at its maximum speed and horsepower rating while still maintaining good servie life.

    Each unit includes, as standard equipment, compressor and engine air cleaners, a compressor air inlet unloader valve, OSHA type fan guards, full but simplified instrumentation and controls and an air receiver-oil serparator system.

    Instrumentation includes an air discharge pressure gage, and air discharge temperature gage, and engine coolant temperature gauge, an engine oil pressure gauge, an ammeter and a tachometer/hourmeter on the instrument panel.  Compression and engine air filter service indicators are located on the control panel.  Also located on the control panel are pushbutton switches for engine starting, safety circuit bypass and an electric fuel primer pump.  Controls also include a start-run (2-way) valve and a manual engine speed and stop control.
   
    The compressor lubricating oil system includes a combination primary oil separator tank and air receiver plus a secondary separator tank, and oil cooler, an oil temperature bypass valve, and oil filter, and an oil shutoff valve.  An unusual feature of these units is the cooling fan which is driven by the compressor instead of the usual engine mounted type.  This provides more efficient fan operation with resulting higher air flow since engine blockage is greatly reduced.  The secondary separator tank is provided with a readily replaceable element featuring a unique porous separation media.  The engine is provided with an electrical starting system, an alternator, a large capacity fuel tank, and a cold weather starting aid.  Engine Operator's and Spare Parts Manuals are provided with each unit shipped from the factory.  Refer to these manuals for specific information concerning the engine in your unit.

    The enclosure is of a rigid construction utilizing acoustic materials to attenuate noise levels.  This unit is also equipped with an acoustically baffled air flow to further reduce the noise level.  Other elements of design incorporated to comply with the EPA noise control act are the engine and cooling fan speeds of 2500 rpm and 1385 rpm maximum, respectively.  All of the above contribute to limiting the full load sound level to 76 decibels (A scale) at a distance of 7 meters in compliance with the U.S. Environmental Protection Agency.

Description of Compressor

    Compression is created by the meshing of two helical rotos (male and female) on parallel shafts enclosed in a heavy-duty cast iron housing with air inlet and outlet ports located on opposite ends of the housing.  The male roto has 4 lobes 90 degrees apart and the female rotor has 6 grooves 60 degrees apart.  The grooves of the female rotor mesh with and are driven by the male rotor.  Thrust bearings at the rear of the air end prevent longitudinal movement of the rotors.  As rotation in the compressor occurs, the rotors enmesh and free air is drawn into the cavities or pockets between the male rotor lobes and the grooves of the female rotor.  The air is trapped in these pockets and follows the direction of rotation of each rotor.  As soon as the inlet port is closed, the compression cycle begins and the trapped air is directed to the opposite or discharge side of the rotor housing.  As the rotors mesh, the normal free volume of air is decreased and the pressure increased until the closing pocket reaches the discharge port.  Cooled lubricating oil is admitted to the compressor by being injected, in a metered flow, directly into the rotor housing so that is passes on with the air being compressed.  This removes the heat of compression to a large degree and results in an unusually low final discharge air temperature.  From the discharge port, the compressed air and lubricating oil is directed to the primary oil separator tank and air receiver which also serves as an oil storage reservoir.  Service air is drawn from the receiver-separator through operation of the minimum pressure valve (which serves as a manual shutoff).

Description of Air Flow

    Air flow through the compressor can be regulated from full capacity to zero capacity dependent upon the air demand placed upon the unit.  Reduction to zero capacity is accomplished by the inlet unloader valve.  The inlet unloader valve, mounted on the rotor housing intake port, controls the capacity of the compressor through a throttling effect.  This is accomplished through the use of a calibrated spring which maintains a sufficient pressure on the diaphragm to prevent movement of the inlet unloader valve until such time that the regulator valve signals the air actuating cylinder to slow the engine to idle speed and the unloader to close off air tor the airend.  Discharge air pressure can be controlled between 70 psi (490 kPa) and the unit's rated operating pressure by adjustment of the regulator valve.

Lubrication

    Both compressor lubrication and cooling are accomplished by the compressor lubricating oil.  The oil is forced from the oil storage reservoir (receiver-separator tank), under system pressure, to the oil cooler.  The cooler is located at the compressor end of the unit in such a manner that the heat exchanger fan cools the compressor lubricating oil.  When the compressor is operating at low capacity, some of the oil may bypass the cooler through a thermostatically controlled bypass valve.  This valve bypasses varying amounts of oil, depending upon the temperature, until the oil being circulated reaches a temperature of 185°F  (85°C).  This maintains a higher average oil temperature thereby reducing the possibility of water vapor condensation in the oil.  From the oil cooler, the cooled oil is directed thru the oil filter then to the rotor bearings, and in metered amounts directly into the rotor housing.  All of the oil thus introduced mixes with, and passes on with the air being compressed, thus removing the heat of compression to a small degree.  On its way to the final discharge connection the air passes through piping to the receiver-separator where the oil is removed from the air to collect in the oil storage reservoir.  Primary separation of the oil takes place through a change in velocity and direction as the compressed air enters the receiver-separator, dropping out most of the oil from the air.  Secondary separation of the oil takes place in the separator element, which is located entirely within the tank.  The oil separator consists of a disposable element made of special materials designed to separate and trap the finely divided oil droplets carried in the compressed air as it passes through the separator element.

XP-750B-W-GM Specifications
Actual Delivery of Compressor	750 cfm  (354 litres/sec.)
Rated Operating Pressure	125 psi  (875 kPa)
Air Cleaner Primary Element	Part. No. 35109263
Air Cleaner Safety Element	Part No. 35109271
Compressor Oil Filter Element	Part No. 35330133
Compressor Oil Capacity	36 US gals.  (136 litres)
Detroit Diesel Allison Div., General Motors Corporation Diesel Engine, Series 6V-71N	Model 7063-7000
Engine Speed at Full Speed	2100 RPM
Engine Speed at No Load	1200 RPM
Electrical Starting System	24 Volt
Engine Lube Oil Capacity (Including Oil Filter)	21 qts.  (19.9 litres)
Engine Coolant Capacity	22 US gals.  (83 litres)
Fuel Tank Capacity	120 US gals.  (454 litres)
Height	7.92'  (2.41 m)
Width	7.25'  (2.21 m)