TABLE OF CONTENTS Light and medium drilling and breaking tools are usually powered by air supplied by portable compressors that are driven by standard types of industrial engines. These machines draw in atmospheric air, compress it, and deliver it through hose to the tools. The compressed air provides a power medium somewhat similar to steam in performance, with the important difference that it can be used cold.
Types of Construction. Compressors used in construction work are one of three types. They may be of the original reciprocating type, the newer rotary vane type, or the newest rotary screw type. Most portable compressors used in construction are of the rotary vane or screw type of air pumps with one or two stages.
In all manufactured forms, it is important that incoming air be filtered to prevent dust from causing excessive wear, fouling moving parts, and choking passages. Intake may be through one or several passages or manifolds.
The diagram in Fig. 20.1 shows the airflow in a single-stage compressor. The inlet passage receives atmospheric air through a cleaner. The discharge is at full working pressure, usually 100 pounds per square inch (psi), and opens into a line to a storage tank (air receiver) from which it is piped to the tools.
The two-stage machine, Fig. 20.2, has one or more primary or low-pressure cylinders which draw in atmospheric air, compress it to about 30 psi, pass it through a cooling radiator (intercooler) to a secondary...
