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Oil filtration of Gear Boxes.
Posted Date:
Total Responses: 0
Posted By: RK Member Level: Diamond Points/Cash: 10
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CONTENTS
1) Introduction,
2) Filtration,
3) Method of filtration,
4) Types of filters,
5) Lubrication of gear box,
6) Contaminants presents in gear box oil,
7) Identifying the sources of contamination,
8) Controlling the sources of contamination,
9) Filtration of gear box oil,
10) Oil filter rating explained,
11) Keeping gear box oil clean,
12) WATER- main contaminants in gear box oil,
13) Oil analysis,
14) Sample report of gear box oil checking,
15) Conclusion.
Objective:-
To study about impurities in gear box oil and filtration.
Introduction:-
Filtration:-
Filtration is a technique used either to remove impurities from an organic solution or to isolate an organic solid. The two types of filtration commonly used in organic chemistry laboratories are gravity filtration and vacuum or suction filtration.
Types of filtration:-
1) Gravity filtration
2) Vacuum filtration
Gravity Filtration:-
Gravity filtration is the method of choice to remove solid impurities from an organic liquid. The "impurity" can be a drying agent or an undesired side product or leftover reactant. Gravity filtration can be used to collect solid product, although generally vacuum filtration is used for this purpose because it is faster.
A filtration procedure called "hot gravity filtration" is used to separate insoluble impurities from a hot solution. Hot filtrations require fluted filter paper and careful attention to the procedure to keep the apparatus warm but covered so that solvent does not evaporate. Hot gravity filtrations are no longer included in the routine procedures for the experiments in the organic chemistry teaching labs, they used to be used in the teaching labs to remove powdered Norite from a hot solution; since we switched to pelletized Norite, hot filtrations are not used. If you need to do such a filtration, read the procedure in the Handbook and consult your TA.
Vacuum Filtration:-
Vacuum filtration is used primarily to collect a desired solid, for instance, the collection of crystals in a recrystallization procedure. Vacuum filtration uses either a Buchner or a Hirsch funnel. Vacuum filtration is faster than gravity filtration, because the solvent or solution and air is forced through the filter paper by the application of reduced pressure. The reduced pressure requires that they be carried out in special equipment:
• Buchner or Hirsch funnel
• heavy-walled, side arm filtering flask
• rubber adaptor or stopper to seal the funnel to the flask when under vacuum
• vacuum source
Methods of filtration
There are many different methods of filtration; all aim to attain the separation of two or more substances. This is achieved by some form of interaction between the substance or objects to be removed and the filter. In addition the substance that is to pass through the filter must be a fluid, i.e. a liquid or gas.
The simplest method of filtration is to pass a solution of a solid and fluid through a porous interface so that the solid is trapped, while the fluid passes through. This principle relies upon the size difference between the particles making up the fluid, and the particles making up the solid. In the laboratory, a Büchner funnel is often used, with a filter paper serving as the porous barrier.
For example an experiment to prove the existence of microscopic organisms involves the comparison of water passed through unglazed porcelain and unfiltered water. When left in sealed containers the filtrated water takes longer to go foul, showing that very small items (such as bacteria) can be removed from fluids by filtration.
A further disadvantage with the physical barrier method of filtration is that the substance being filtered from the fluid will clog the channels through the filter over time. Thus the filter becomes less and less efficient over time (for example, a vacuum cleaner bag). Thus methods have been developed to prevent this from happening. Most such methods involve replacing the filter. However, if the filter is needed for a continuous process, this is highly problematic, and complex scraping and in-situ cleaning mechanisms have to be used.
For separation where there is a very small size difference, chemical filters may be used. These will use a filter that has properties so that undesirable items are attracted and retained by the filter, and the fluid from which it is to be separated is not. Filters of this kind most often take the form of electrostatic attractions. These form of filters again have the problem of either becoming clogged, or the active sites on the filter all become used by the undesirable. However, most chemical filters are designed so that the filter can be flushed with a chemical that will remove the undesirables and allow the filter to be re-used.
Filtration is a more efficient method for the separation of mixtures than decantation, but is much more time consuming. If very small amounts of solution are involved, most of the solution may be soaked up by the filter medium.
Types of Filters:-
1) SELF CLEANING FILTERS:-
Operating principle:
The polluted medium flows through the metallic, cylindrical filter element. The dirt particles, which are larger than the openings in the filter element, deposit on the surface of the filter element.
These pollutions are scraped off by the firm scraper-blade during the turning of the filter element. They accumulate in the sump of the filter housing. There the dirt particles are discharged periodically through a manual or automated drain-valve out of the housing. The cleaning and the discharge of the dirt happen without interruption of the flow.
This makes a continuous use of our self cleaning filters possible. Special perforated filter elements are available for the filtration of gel-like and fibrous particles. These elements have been developed especially for such applications, where conventional wedge-wire-elements are not suitable, e. g. filtration of algae, fibres etc. out of water.
2) AUTOMATIC BACKWASH-FILTERS:-
Operating principle:-
The liquid flows through the filter element from the inside to the outside. The dirt deposits on the inner surface of the filter element. The differential pressure increases caused by the accumulation of the dirt. If the differential pressure reaches a certain level, the cleaning cycle is released.
The gear motor starts its operation and turns the hollow shaft with the nozzles. The drain-valve is opened. The flow direction is reversed locally by this constellation. The dirt is dissolved from the filter element. It is discharged of the filter housing over the nozzles and the hollow shaft through the drain-valve with a small quantity of of liquid. The filtration is not interrupted during this cleaning cycle.
3) BASKET-FILTERS in welded design:-
BASKET-FILTER type DELTA-SKS:-
Basket-filters of type DELTA-SKS in welded design are
a robust and affordable solution for the cleaning of liquids or the recovery of valuable solids. They can also be used for the protection of fittings and pipelines. The compact filter has a flat cover. An O-ring is used for the sealing of the cover. The filter stands on its flat bottom. The fastening flaps on the bottom are for the fixing of the filter on the floor. The pick-up for the basket is inside the housing. The basket is made of high-grade stainless steel. The standard baskets are available with filtration ratings from 5 µm up to 5000 µm. We can deliver baskets with pleated fabric on request. The standard sizes are from DN25 (1") up to DN300 (12"). Carbon steel or stainless steel is used as material for the housing. Special materials, inner coatings, high-pressure versions, TÜV acceptance\ etc. are available on request.
4) BASKET-FILTER in casted design:-
Single-Basket-Filter type DELTA-OV:-
Single-Basket-Filters of type DELTA-OV offer an affordable method for the cleaning of liquids or for the recovery of valuable solids. They can also be used as protection for pipelines and fittings. The compact filter housing is made in casted design. It is delivered with a strainer basket insert of high-grade stainless steel. The standard baskets are available in filtration ratings from 50 µm up to 6350 µm. Filtration ratings of 10 µm or 25 µm are possible with special baskets. The sizes are available from DN20 (3/4") up to DN150 (6"). The sizes DN200 (8") and DN250 (10") are available in multi-basket design.
5) CANDLE-FILTERS of types DELTA-KFS, -KF, -KF-1:-
CANDLE-FILTER type DELTA-KFS:-
The standard candle-filters of type DELTA-KFS are constructed for filter-cartridges, which are douple open ended (DOE), e. g. wound elements of type DELTA-WYND. 3 respectively 6 filter elements with a length from 9 3/4" up to 40" can be fitted in the different housings. Stainless steel 1.4301 and 1.4571 are available as material for the housings. The pick-up for the candles is of stainless steel 1.4404.
The cover closure is done with a quick-action clip that ensures fast and simple filter cartridge replacement - no tools required! The casing is sealed by an O-ring produced from NBR (standard), alternative sealing materials are available. The nozzles of the in- and outlet are designed with male or female thread. They can also be done with thread-flanges, if required. Sockets for ventilation and purging for the clean and dirt side are available. Working pressures of 10 bar at 90°C are possible.
6) BAG-FILTERS:-
Operating principle:-
Bag-filters of type DELTA-BF are conceived for the pick-up of filter-bags in different sizes, filter rates and materials. The standard types are with hinged lid, balve-valve for ventilation, hasp screws and eye nuts. Erected using feet, which are adjustable in height. The self-adjusting pressing device for the filter-bag adjusts to the different material thickness of the bags and the rings. Four types of bags with varying filter areas are suitable. The support baskets have a large filter area. Multi-combination or housings with several filter-bags are available for higher flow capacities.
The bag-filters of type DELTA-BF can also be offered and produced according your specification and wish! Especially our bag-filters of polypropylene with internal parts of PP, PVDF or PVC shall be mentioned here. Also we can deliver you the suitable filter-bags in different designs.
LUBRICATION OF GEAR BOX
• Proper Lubrication with timely addition / replacement plays vital role in maintaining the gear boxes with efficiency and increasing its working life.
• Oil level should be checked in all the gear boxes oil indicators / dip sticks.
• Oil level should be in between the minimum and maximum limits of the dip stick (or indicator).
• Testing of the lubricating oils used to be carried out periodically. The following tests are to be done…
1. Dirt contamination
2. Moisture
3. Volatile materials (Benzene, kerosene, spirit etc,)
4. Viscosity
5. Acidity
6. Alkalinity due to soda (Na2 Co3) etc.
Contaminants present in gear box oil:-
There are following particles presents in gear box oil:-
1) Some non metallic crystal,
2) non metallic amorphous particles,
3) Rubbing wear particle,
4) Fatigue wear particles,
5) Moisture,
6) Dust
• “Wear and tear” is a common expression used to describe the ageing of the mechanical systems.
• Wear commonly occurs as a result of the contamination and degradation of the lubricant.
• The contaminants can… not only cause a breakdown in the health of the lubricant, but will also interact with the moving surfaces to cause wear, leading to component failure.
• Adhesion, abrasion and corrosion of component surfaces will typically result from oil contamination as will poorly specified or unhealthy lubricants.
• The wear rate can be reduced as a result of some basic measures to protect the gear box from wear.
Need to Filter the gear box oil:-
Contamination of hydraulic, lubrication, and dielectric fluids can cause accelerated wear of a systems vital parts. (Bearing, valves, pumps, gears, contacts, etc.) This causes inefficient operation of the system and complete failure in some cases. To help eliminate contamination, Oil Filtration Systems manufactures a variety of fluid purification equipment and distributes high efficiency filter elements for virtually any industrial, mobile or process application.
IDENTIFYING THE SOURCES OF CONTAMINATION:-
• Contaminants are hard particles, moisture, high temperature and aeration. The other examples are radiation, process chemical or physical matter from the environment.
• Ingression points of the gear box contamination are seals and the breathers. This will be during maintenance activities such as top –ups, drain and refill etc.,
• Wet conditions may ingress moisture into the gear box.
• Dust particles are ingresses in the gear boxes from the environment.
CONTROLLING THE SOURCES OF CONTAMINATION:-
• SEALS: Standard lip seals are low-cost item, but require frequent replacement. Their ability to seal against oil leakage and dirt/water ingress is poor by comparison to labyrinth seals. These seals cannot be directly loaded or pressurised with external forces.
• BREATHERS: snorkel type, or vent plug type breathers can prevent large bodies to ingress into the gear box, but cannot stop a destructive 10 µm particle from entering into the gear box. (like a ball rolling into a open door)
• Upgrading the vent into a proper contaminant-exclusion breather should minimize the ingression of hard particles and moisture. (1 µm filters)
• For applications where volume changes are minimum and the dusty environment, the bladder type (also known as expansion chamber) of breather is recommended to use.
• The bladder allows for expansion and contraction of the air within the casing as a result of temperature changes.
FILTRATION OF GEAR BOX OILS:
* PORTABLE OFF-LINE FILTRATION: Some gear boxes may incorporate a small pump with a filter.
Many gear boxes don’t have filtration facility. In such cases filter carts can usually adopted by replacing the fill and drain plugs with quick –connect fittings.
At least 5 to 7 times the volume of the oil in the system should be passed through the filter cart to ensure adequate clean up.
* PERMANENT OFF-LINE FILTRATION: Larger units where large volumes of oil and high levels of cleanliness must be maintained, a permanent off-line circuit should be employed.
Oil filter rating explained:-
"What does industry consider the standard in regards to filter efficiency? When I hear that a filter is rated at 1 micron, does that mean it is 100 percent efficient at that micron size?"
Filter ratings are an often misunderstood area of contamination control. The most commonly used rating is the Beta ratio, which is defined as the ratio of the number of particles upstream of the test filter versus the number downstream, greater than a given size. Using the Beta ratio, a 3 micron filter with a Beta 75 rating, will have on average 75 particles larger than 3 micron upstream of the filter for every one 3 micron or greater particle.
The efficiency of the filter can be calculated directly from the beta ratio since the % efficiency is simply (beta-1)/beta x 100. A beta 75, 3-micron filter is thus said to be 98.66% efficient at removing 3 micron and larger particles. It is important to note that a change in the beta rating from 75 to 200 at the same micron rating represents an increase of less than 1% in efficiency, but the beta 200 filter is more than 3 times more effective at removing 3 micron and larger particles than the beta 75 filters.
Caution must be exercised when using beta ratios since they do not take into account field operating conditions such as pressure surges and changes in temperature, which can affect real life performance. A filters beta ratio also does not give any indication of its dirt holding capacity, the total amount of material that can be trapped by the filter throughout its life, nor does it account for how the capture efficiency changes over time. Nevertheless, beta ratios are an effective way of gauging the expected performance of a filter.
The ISO standard for Multi-pass filter testing (ISO 16889) has changed to require filter manufacturers to determine the average particle sizes which yield Beta ratios equal to 2, 10, 75, 100, 200, and 1000, again using the multi-pass test stand approach. The new standard gives a better interpretation of a filter's overall performance.
Of course, regular monitoring of fluid cleanliness using ISO particle counting should be used to determine the efficiency of the filter in actual field conditions.
Keeping Gearbox Oil Clean:-
"I notice that the ISO cleanliness level doesn't change much after changing the oil in my gearboxes. Shouldn't the oil be cleaner after the change?"
Most gearboxes are drained on a quarterly, semi-annual or annual basis - usually to eliminate contaminants. Typically, five percent or more of the old lube is left in the gearbox. If the oil is not drained shortly after shutdown, the sludge and contaminants will accumulate in the bottom of the sump and remain with the residual oil. When the box is refilled with lubricant and restarted, the contaminant is re-suspended, and the oil change fails to achieve its objectives. Also, the new oil may not be clean if it is not prefiltered.
Consider the following alternatives:
1. Drain the oil within 15 minutes of shutdown and pre-filter the new oil.
2. Instead of draining the oil, periodically filter the oil with a portable filtration cart while the machine is operating. Sample and analyze the oil periodically to determine if it needs to be changed. This strategy will reduce your overall cost of maintenance and extend the life of the gearbox, and requires little up front investment.
3. Install full-time filtration on the gearbox and sample and analyze the oil periodically to determine if it needs to be changed. This strategy will also reduce your overall cost of maintenance and extend the life of the gearbox, but requires some up front investment.
Alternative 1 helps, but alternatives 2 and 3 are real winners. Most scheduled oil changes can be eliminated with the one-two punch of filtration and oil analysis. This strategy reduces lubricant and labor costs – and the fact that your gearboxes will last longer is a major bonus. Plus, the maintenance of the fluid can typically be performed during run-time, shrinking the task list during scheduled outages.
WATER – Main contaminants in gear box oil.
Water is a common contaminant in hydraulic and lubricating systems. Moisture can enter these systems at several points:
* Through reservoir breather caps in humid air. System fluid absorbs some of this moisture, while some is condensed on the inside surfaces of the reservoir.
* Through worn seals. Besides humid air, coolant and cutting fluid sprays can enter hydraulic systems through worn rod seals as the cylinder moves. In lubricating systems, these water-based fluids can enter through rotating shaft seals on pumps, machine tool spindles and gear boxes.
* Through heat exchangers. Worn and damaged heat exchangers can allow cooling water to leak through seals and ruptured lines into the oil system, and vice versa.
* In new oil. An oil barrel stored outside in a vertical position is likely to collect rainwater around its bung. With changes in temperature, some of this moisture will be sucked into the barrel. Eventually, this water enters the system fluid when the reservoir is filled.
Oil Analysis:
Oil analysis is a predictive maintenance technique by this we can predict the breakdown which may occur and subsequently take action so break down is prevented, which otherwise would lead to lose of production, lose of equipment/spares, maintenance cost involved to bring the equipment to its working condition.
Secondly changing / replacing the oil from the standard period provided by the suppliers, we just change the lubricant at regular interval irrespective of the condition. So there are two possibilities
1.Chances of deterioration/degradation of the oil due to some parameters related to process, contaminant etc, though the oil is not recommended for change as per schedule but has deteriorated, will result in damaging the costly equipment, breakdown, maintenance cost etc.
2. If oil is good and we replace the oil as per schedule then there will be wastage of oil.
`There is few equipment which are running for years even after the expiry date of lubricant is over. But by oil analysis we monitor the contamination and other oil parameters and replace if really required.
Considering the long term benefits achieved by this condition monitoring technique, by keeping the plant equipment in the reliable condition and reducing the equipment breakdown by monitoring the oil quality as per the schedule the amount which we pay to the laboratory is negligible.
Knowing the high sump capacity and the oil inside it, if we replace the oil as per the manufacturer’s recommendation it will not be feasible for us to do it practically. Thus result in loss of money and also good oil which we can use it further for some more months / years.
Taking the example of Mill Zos 2000 which is having the tank size of 80,000 liters, Zos 400 tank size of 10,000 liters. MOS 1700 tank size 55,000 liters. Zos 80 tank size is 5000 liters, Mill HP hydraulic tank size is 12000 liters mill LP hydraulics tank size is 12000 liters, Mill down Coiler Hydraulics tank size is 12000 liters, Mill coil conveyor hydraulics tank size is 8000 liters.
So generally as per oil supplier recommendations oil is to be changed for gear oil is at every 5000 hrs. In that case the oil is to be changed at every 10 months, but we have not changed the oil of these systems since 1997 (starting of the commissioning of the plant).
ZOS 2000 (Oil grade Omala 460)
Oil filled 60,000 liters. Would have changed 3 times by now
ZOS 400 (Oil grade Omala 460)
Oil filled 8000 liters. Would have changed 3 times by now
ZOS 80 (Oil grade Omala 460)
Oil filled 4500 liters. Would have changed 3 times by now
HP hyd, (Oil grade Tellus 46)
Oil filled 10000 liters, Would have changed 3 times by now
LP Hyd, (Oil grade Tellus 46)
Oil filled 10000 liters, Would have changed 3 times by now
DC hyd. (Oil grade Tellus 46)
Oil filled 10000 liters, Would have changed 3 times by now
So By the price of the oil it can be assessed how much would have been the lubricant cost, changing cost and disposal cost.
Sample report of gear box oil checking:-
Oil Analysis Report
Sample Date :- 15.03.05
Laboratory :- Shell
Equipment Tag : - 2MCK0602 GB
Equipment Name : - Caster crane no 06, Main hoist GB
Area : - Mill
Observation : - Low Viscosity, high Iron, presence of copper and lead,
That may be due to some wear out component.
Recommendation :- Please replace the oil and inspect the gear box for any deterioration, which may be Causing presence of iron, copper and lead.
Conclusion:-
Due to this filtration of gear box oil, Contamination of oil is reduced. This leads to avoid the deterioration of gears and bearings and increase the life of gear box.
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