Table of Contents
Advertisement
2.5 General description
The PTS 916 Cd is a portable, two-stage screw compressor unit,
that delivers oil-free air.
The PTS 916 Cd is built for a nominal effective working pressure
of up to:
– 0.5 - 10.3 bar (7 - 150 psi) at 1550 rpm
– 0.5 - 9.3 bar (7 - 135 psi) at 1750 rpm
– 0.5 - 6.9 bar (7 - 100 psi) at 1850 rpm
The driving direction has always been originated with, when the
sides of the unit are denoted. E.g. the towbar is at the front and the
User Interface is at the rear right-hand side of the unit.
Engine
The compressor is driven by a liquid-cooled diesel engine,
manufactured by Caterpillar. This engine has the following
characteristics: direct fuel injection, electronic unit injection that is
mechanically actuated, turbocharged, and air-to-air aftercooled.
For general description, see Engine Operation Manual (EOM).
Compressor
The compressor has one low-pressure and one high-pressure
compressor element, individually bolted to the housing of a
common step up gear. The step up gear is bolted directly to the
engine flywheel housing. The power from the engine is transmitted
to the step up gear shaft through a flexible coupling.
Compressor elements
Each compressor element houses two screw-type rotors, mounted
on ball and roller bearings. The male rotor, driven by the step up
gear, and the female rotor are synchronized through timing gears,
which maintain the slight clearance between the rotors.
The male rotors have four lobes and the female rotors six flutes.
Thus, the male rotors revolve at 1 1/2 times the speed of the female
rotors. The absence of contact between the rotors and between the
rotor crests and the compressor casings eliminates wear and power
loss. The elements deliver pulsation-free air.
Air and oil sealing rings are fitted on the rotor shafts. The air seals
are located next to the compression space, the oil seals next to the
rotor bearings. The leak air from the air seals is evacuated to the
atmosphere through vent-holes. Any oil that might gather between
the oil and air seals is prevented from entering the compression
space, as it is drained through the same vent holes.
Preliminary
Cooling and lubrication
The unit is provided with an air-cooled aftercooler 2, with water
separator, and CAC (= charge air cooler)/fuel cooler placed in the
back of the unit. The cooling air is generated by an axial fan, which
is belt-driven from the engine fan shaft.
Water condensate from the water separator is drained through a
nipple in the bottom of the frame in the back of the unit.
The radiator, intercooler, aftercooler and oil cooler are installed
side by side in the front of the unit. These coolers are air-cooled by
an axial fan, which is belt-driven from the compressor main-shaft.
Oil is used for jacket-cooling of the compressor elements, as well
as for lubricating the rotor bearings, timing and drive gears. The
system includes an oil pump and an oil filter.
Speed regulation and unloading system
The regulation of the unit is governed by the Engine Controle
Module (ECM) and the Compressor Control Module (CCM),
which will vary engine speed and operate the compressor throttle
valve and unloading valve through a 3-way loading valve.
Safety devices
Two relief valves and a MP safety valve protect the LP and MP
sides of the compressor respectively.
A check valve prevents blow-back of compressed air when the
compressor is unloaded or stopped.
Pressure and thermal shutdown switches protect the compressor
against abnormal operating conditions.
Frame and axles
The compressor/engine unit is supported on a frame which also
carries the compressor cooling block.
The front axle is provided with a steering gear and a hinged towbar
with towing eye. The towbar can be locked in the raised position.
The unit is equipped with a parking brake, operated by a handle
close to the towbar.
Bodywork
The bodywork has openings for the intake, cooling and exhaust air
and specially hinged doors for maintenance and service operations.
The bodywork is internally lined with sound-absorbing material.
The air outlet valves are in the frame, at the back.
Instruction manual
15
Advertisement
Table of Contents
