Figure 12-1. Flow diagram for mechanical-compression system.
b. Condensing Unit. The coil assemblies should be
(6) A control panel with gages, switches,
reducing valves, pilot lights, and other devices for
inspected periodically and the framed surfaces cleaned
checking operation of the air conditioning when the car is
with compressed air. Accumulated cinders and dirt
in service and for checking replacements and repairs
should be cleaned from the framework. Supporting bolts
when the car is out for maintenance. Most elaborate
should be checked to assure they are drawn up tight, with
systems use a series of thermostats, gaged to meet the
the nuts locked in place.
varying requirements of heating, cooling, and humidifying
c. Compressor. Surface dust accumulations will be
blown off with compressed air at the periodic inspections.
12-4. Maintenance and Repair
An oily dirt accumulation indicates leaks which should be
a. General. A definite program of inspection and
located and corrected. All nuts will be tightened. Check
of compressor speed will indicate any belt slippage. The
maintenance is essential to the operation of air-
correct compressor speed is 511 rpm for 6-ton equipment
conditioning equipment on railway passenger cars.
and 382 rpm for 5-ton equipment. The corresponding
Commercial railroads have found by experience this
motor speeds are 1,750 rpm and 1,450 rpm respectively.
maintenance program is divided into three general
Direction of rotation of the compressor is clockwise when
categories. The railroad designation and its military
facing the flywheel end.
equivalent are: daily or end-of-trip maintenance
d. Belt Adjustment. After loosening the motor
support), and annual equipment overhaul (general
supporting bolts, adjust the belt tension by shifting the
support-depot) In commercial railroad practice, this is
motor in its slotted supports by means of the adjuster
flexible and is changed as necessary to meet the
screws. When belt adjustment is necessary and until the
requirements of the particular service in which the
initial stretch is taken up, the fan shroud on the movable
equipment is placed. Maintenance procedures for various
back half of the back cover should be moved with the
components are discussed below.
motor so that the fan shift will always be centrally within
the shroud. Proper belt tension will be