Table 1-1. Equipment Data
Model 340, two stage, belt driven
10 hp, 60 Hz, 240/460 Vac
1-9. Safety, Care, and Handling. Safety precautions must be observed at all times while performing
maintenance. General WARNINGS and first-aid data appear in the front of this manual. Review all safety
information before starting any task. Carefully read through an entire maintenance procedure before
performing any maintenance function. Make sure the task can be done safely. All WARNINGS, CAUTIONS,
and NOTES are of great importance to your safety and the safety of the equipment.
SECTION III. PRINCIPLES OF OPERATION
The Principles of Operation will give you basic information about how these two compressors work.
1-10. General. There are two QR-25, Model D340 air compressors, which are intended to supply air to the
storage tanks. The two air compressors are mounted one over the other on the port side aft end of the engine
room. The air pressure from each compressor is controlled by an individual pressure switch mounted near
each compressor which is set to cut out at 200 psi (5 psi). The bottom air compressor is set to start and
operate at a minimum of 180 psi (5 psi) and the top air compressor is set to start and operate at a minimum of
160 psi (5 psi). The system pressure relief valves are set at 240 psi (5 psi). The air compressors are
controlled by a local start-stop switch located at the air compressor in the engine room. An emergency run
switch is located at the motor controller located on the forward bulkhead of the engine room. The pilot house
and engine room control consoles each have an air pressure gauge which displays system air pressure.
a. Air Compressor. The following is a brief summary of the QR-25, Model D340 air compressor
assembly and the drive system, and a description of controls that are separate from the compressor assembly
(1) Drive Sheave (Pulley). The drive sheave (pulley) has cast iron fan blades that direct a blast of
air across a finned intercooler, then across the finned cylinders and heads.
(2) Intercooler. The intercooler is an integral design of the air-cooled two-stage compressor. The
intercooler consists of finned tubes connecting the first stage and the second stage. The tubes cool and
condense the air.