BRACKET 2056233 - Caterpillar

CONFIDENTIAL
TECHNICAL INFORMATION BULLETIN April 20, 2001
OFF-HIGHWAY TRUCK 797 (5YW1-Up)
Component Code(s) 4263-045SUBJECT: THE PRE-CHARGE PRESSURE FOR THE 797 OFF-HIGHWAY TRUCKS SERVICE BRAKE AND PARKING BRAKE ACCUMULATORS HAS INCREASED
PROBLEM:
The pre-charge pressure for the 797 Off-Highway Trucks service brake and parking brake accumulators needs to be increased.
SOLUTION:
Increase the pre-charge pressure of the accumulators for the service brake and parking brake from 6895 KpA (1000 Psi) to 10342 kPA (1500 Psi) at an oil temperature of 21? C (70? F).
This increased pre-charge pressure will provide longer service life of bladders within the accumulators. In addition, the increased pre-charge pressure will improve the operational performance of both brake systems.
Use the following chart to set the pre-charge pressure if the temperature of the oil varies ? 5.5? C (? 10? F) or more from 21? C (70? F).
Relationship Between The Charging Pressure and The System Oil Temperature
System Oil Temperature deg C (deg F) Brake Pre-Charge Pressure kPA (Psi)
-40 (-40) 8198 (1189)
-34 (-30) 8391 (1217)
-29 (-20) 8584 (1245)
-23 (-10) 8784 (1274)
-18 (0) 8977 (1302)
-12 (10) 9170 (1330)
-7 (20) 9363 (1358)
-1 (30) 9563 (1387)
4 (40) 9756 (1415)
10 (50) 9949 (1443)
16 (60) 10149 (1472)
21 (70) 10342 (1500)
27 (80) 10535 (1528)
32 (90) 10735 (1557)
38 (100) 10928 (1585)
43 (110) 11121 (1613)
49 (120) 11321 (1642)
54 (130) 11514 (1670)
60 (140) 11707 (1698)
66 (150) 11900 (1726)
71 (160) 12100 (1755)
77 (170) 12293 (1783)
82 (180) 12486 (1811)
The above chart will replace Chart 11 in Testing and Adjusting, RENR2611, "Service Brake Accumulator and Parking Brake Accumulator".
The pre-charge pressure of the accumulators for the service brake and parking brake should be checked at every 500 SMH interval. This will help to ensure that there is a proper pre-charge pressure in the service brake and parking brake accumulators.
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