Heavy Duty Balanced Opposed Compressors - Ariel Corporation

FOR MODELS: JGZ AND JGU SECTION 5 - MAINTENANCE
Crankshaft
Checking Main Bearing Clearances
1. Do not remove main bearing caps to check for bearing wear, if a cap is removed
it is recommended that a new bearing be installed, i.e. DO NOT REUSE BEAR-
ING SHELLS.
2. Determine main bearing wear by checking actual journal bearing vertical jack
clearance, at each bearing, and crankshaft thrust clearances against the clearance
limits given in Table 1-4 on Page 1-13 and the last new bearing clearance
values if available. High copper content in the oil analysis can be an indication of
bearing wear. Use calibrated dial indicators with 0.0005 inches (0.005 mm)
increments and magnetic bases to check clearances.
3. Operate pre-lube pump before rotating the crankshaft.
4. Measure main bearing vertical jack clearances as follows:
a. Manually rotate the crankshaft to turn an adjacent throw to the highest
position, and see Figure 5-11 on Page 5-18.
b. Place lifting strap completely around the crankshaft at the adjacent web and
attach strap to a crane.
c. Install a magnetic base on the top of the main bearing cap, with a needle
type dial indicator placed against the top of the crankshaft web of the
adjacent turned up throw. Set indicator at zero.
d. Gently lift crankshaft with the crane until needle on dial indicator stops
moving. Repeat to make sure reading is accurate. Should the connecting
rods are removed, put a clean lifting strap around the adjacent pin and
carefully pull up on the crankshaft with the strap. Repeat to be sure that the
reading is accurate.
e. Repeat Paragraphs a. through d. for each main bearing.
7/09 PAGE 5 - 17