Barko 495B - SE - Eliminating Air from the System; Causes; Damage to the System; How to Avoid Aeration

Service ManualLast Updated - 9/28/2016
495B SE (S)
44
ELIMINATING AIR FROM THE SYSTEM
Allhydraulicuidcontainssomedissolvedair,usuallyabout10%byvolume.Underincreasedpressure,theuidwill
absorb much more air. Aeration in a hydraulic circuit is the presence of free air in places where there ought to be only
uid.Usuallytheairwillbeintheformofbubblesdispersedthroughtheuid.
Difcultieswithaerationwilloccurmorefrequentlyasowvelocitiesincreaseinhydrauliccomponents.This
section covers some of the causes of air being introduced into a system and the suggested practices to effectively
reduce and eliminate this problem.
CAUSES
The most common places for air to be introduced into a hydraulic system or for aeration to occur are listed below:
1. Damagedinletline;looseordefectivettingsorsealsatanycomponent.
2. Damagedreturnline;looseordefectivettingsorsealsatanycomponent.
3. Damaged or worn cylinder rod, packing or seals.
4. Cracked junction blocks, tees or piping.
NOTE:Becauseuidactsasasealantatatmosphericpressure,whensystemdropsbelowatmosphericpressureair
  maybedrawninwhereuidwillnotnecessarilyleakout.
5. Fluid level too low. This can cause vortexing at pump inlet in reservoir, thus drawing in air.
6. Airtrappedinlterwithnomeansofbleedoff.
7. Returnuiddischargedaboveuidlevelinreservoir.Poorbafinginthereservoircanalsocauseturbulenceand
resultant introduction of air.
8. Airtrappedinsystemduringoriginallling,orwhenaddinguidformakeup.
DAMAGE TO THE SYSTEM
The condition listed in the previous paragraph all contribute to inducing air into a hydraulic system. This aeration can
cause jerky and uneven movement in pumps and motors, seizure, overheating, and possibly eventual failure.
HOW TO AVOID AERATION
Regular inspection and regular maintenance are the best ways to prevent air from being introduced into a hydraulic
system.Keepingallconnectionsandttingstightistheeasiestwaytoavoidtheintroductionofair.
Returnuidenteringthereservoirwillcreateaerationifitisdischargedabovethemainbodyoftheuidinthetank.
Topreventthiscondition,maintainsufcientuidinthetanktokeepthereturnlinesubmerged.Thepumpintakeline
shouldalwaysbebelowtheuidsurfaceforthesamereason.
Improved service life depends on maintaining proper conditions within the system.