Embed Size (px)
DESCRIPTION
Robust and reliable, gearboxes are designed to provide many years of service with very limited maintenance requirements. Recent trends in equipment design require them to operate withincreased power requirements, higher speeds and higher stresses. This adds to the importance of initial equipment set-up, maintenance operating conditions, and the quality and performance of the lubricant to ensure reliable operation. While incorrect operating temperatures, misalignment and resonant vibrations typically provide a slow path of component degradation, lubrication condition and contamination will lead to rapid and unnecessary wear, and theeventual failure of the unit itself.
Citation preview
Best Practices Series
Lubrication Management:Gearbox Contamination Control
BEST PRACTICES SERIES
2 Best Practices Seriesmaximumrpm.ca
Robust and reliable, gearboxes are designed to provide many years of service with very limitedmaintenance requirements. Recent trends in equipment design require them to operate withincreased power requirements, higher speeds and higher stresses. This adds to the importanceof initial equipment set-up, maintenance operating conditions, and the quality and performanceof the lubricant to ensure reliable operation. While incorrect operating temperatures,misalignment and resonant vibrations typically provide a slow path of component degradation,lubrication condition and contamination will lead to rapid and unnecessary wear, and theeventual failure of the unit itself.
Controlling Contamination
A contaminant is any substance that entersa system and adversely affects its functionor reliability. Contaminants such as solids,water and gases (primarily air) will reactwith lubricants also decreasing the life ofrotating equipment. Fluids must beprotected from these contaminants by acomprehensive contamination-controlprogram.
Understanding the contaminants and theirorigin will provide clues as to how they canbe excluded, removed, or their effectsneutralized. Contaminants can be built-indue to manufacturing or maintenanceprocesses, or they may enter a system whileparts of it are open during construction orrepair. They can also be internallygenerated as a result of system operation,such as wear debris, compounds ofchemical reactions, or substances resultingfrom decomposition of the fluid or itsadditives.
The most common source of entry isthrough breather caps, imperfect seals, orother unplanned openings during normaloperation of the equipment. This includes
the addition of fluid during initial fills ortop-ups.
Original Equipment Manufacturers willprovide their own equipment specificrequirements for targets and limits ofcontamination in their maintenancemanuals or service bulletins. In most cases,these targets are not adequate or evenmeet the specifications of the bearingmanufacturers.
TYPCIAL GEARBOX (OEM) REQUIRMENTS
Gearbox(OEM)
Bearing(OEM)
Filtration (ISO4572)
ß25 =200 ß 6 = 200
ISO ParticleCount (ISO
4406)
Max21/15
Max14/11
WaterConcentration
Max. 0.05%(500 ppm)
Max. 0.05%(500 ppm)
As system or environmental temperatureschange, the lubricant and air inside thesump will expand and contract; forcing airinto or out of the housing.
3Best Practices Series maximumrpm.ca
When inhaling, the air carries thecontaminants of the local environment intothe gearbox or bearing housing. Managingthis source of contamination is the first steptowards controlling the quality of lubricantinside the gearbox. Typical methods toallow for this ‘breathing’ are a small hole inthe cap, or a very poor quality strainer stylevent that will not adequately protect thegearbox or maintain the OEM specified fluidrequirements.
Choosing the proper breather starts withunderstanding the environment around thehousing. Oil sampling and testing, coupledwith investigating the surroundingenvironment, will ensure that the type ofcontaminants and source of entry areaddressed. The following chart lists someof the breather exclusion methods alongwith the contaminants that they restrictfrom entering the housing headspace.
Breathers that contain filters or desiccantcan become plugged with debris orsaturated with water. When this happensthe sump will have no other option but toexhaust the air through the seals causingleakage and a newsource ofcontamination. It isimportant to monitorthe condition of thebreather frequently to ensure that it isoperating properly and change it when it isnot. Filter minders or breather conditionmonitors are highly effective to provide aquick and easy visual indicator of thebreather condition.
Closing a system completely with anexpansion chamber or bladder system willeliminate the need to change drying agents,however must be sized according to theamount of expansion within the sump.
METHODS OF
EXCLUSION >5
0
MIC
RO
NS
<1
0
MIC
RO
NS
<5
MIC
RO
NS
Open Vent
Metal Screen X
Cellulose Filter X X
Filter Pads X X
Microglass Filter X X X
Desiccant Silica Gel X
3m Filter/ Desiccant
Silica GelX X X X
Activated Carbon X
Activated Carbon / 3m
FilterX X X X
3m Filter,/Silica Gel
/Activated CarbonX X X X X
Expansion Bladder
SystemsX X X X X
SOLID PARTICLES
AIR
BO
RN
E
WA
TER
FUM
ES/O
DO
UR
Note: All breathers must be properly sized and
CONTAMINANTS EXCLUDED
4 Best Practices Seriesmaximumrpm.ca
These chambers capture the air inside thesump as it expands then allows the bladderto retract as the air contracts. If notproperly sized these units can cause anyexcess expansion of air to occur through theseals causing leakage and allowingcontaminants to enter the system.
SUMMARY
Temperature, pressure, contaminants,aeration, water, metal particles, andagitation accelerate the oxidation process(destruction) of lubricants. Combine thatwith the destructive nature of solid particlestrapped between rolling elements,raceways and gear teeth, and the result isthe sacrifice of equipment performance andreliability.
Lubrication Management forGearboxes/Reducers combines:
Maintaining headspace quality
Operating within the designedoperating conditions
Use of dedicated and/or portablefiltration for contamination control
A competent oil analysis programfor maintaining the specific physical,chemical and cleanliness standardsthroughout the life of the lubricant
Controlling contamination will help extendthe life of equipment and the frequency oflubricant change outs. A few simple toinstall, value added parts can provideimproved reliability and lower costs for allrotating equipment.
Condition monitoring programs require equipment specific knowledge to set-up and executean oil analysis program thatis effective and efficient.Completely understandingthe fluid path(s) of alubrication system willallow for the identificationof the optimum samplinglocation(s) for criticallocations and/orcomponents of the system.This location in many casescan appear inaccessible orsamples in reducing maintenance costs. =
Maximum RPM1000 Windmill Road
Suite 381.902.444.4252
BEST PRACTICES SERIES
For more information about reducing the amount of contaminants entering yourgearboxes please contact us
