What Causes Wear?
Contamination has frequently been identified as one of the major causes of premature wear on rotating machines. If all other root causes, such as the alignment, balance, and mounting integrity, have been checked, then the other major influences are solid particulate and moisture.
Contamination control is critical—solids under 10µm are often the most destructive to rotating machines.
The pumped product itself may be the cause in pumping systems, but solids of less than 10µm are generally deemed the most destructive. Other root causes of premature wear also come into play, such as topping up with the wrong lubricant or using inadequately specified oils and greases.
Dealing with the Sources of Contamination
Attitude
The biggest hurdle to improving systems is to change the culture. An active discipline of good housekeeping goes a long way towards this, but ultimately, all maintenance and operations personnel need to understand why contamination control is critical.
Create a Color-coded Tagging System
Create a color and shape-coded chart to identify each lubricant. Ensure that all the units are tagged with the appropriate color code for the oil or grease in use, along with the frequency and number of shots applied on greased systems.
Color-Coded Tagging System. Courtesy Oil Safe.
Apply the color coding to the new lubricant packaging and the funnels and tools used for dispensing when it arrives on-site.
New Equipment Commissioning
The cleanliness of units at the commissioning stage is crucial to ensuring infant reliability and increased operating life. It is common to find manufacturing debris present in a new unit. Ensure that when specifying new units, the best quality breather and seals are chosen as standard.
The cleanliness of units at commissioning sets the stage for infant reliability and longer operating life.
Ensure that any openings in the castings, etc., are plugged, the shafts and gears are covered with a protective film of grease or oil while in storage, and that this is thoroughly removed before use. Use the portable filter cart to flush the unit through before it is turned.
The best way is to use a low-viscosity fluid that can splash through the box, ensuring that all the dead zones are cleaned and any debris is dislodged and trapped by the filter cart. If you request the OEM to do this before delivery, ensure they flush according to the appropriate standards and show proof of achieving your required levels.
Storage and Handling
Ensure a clean, dry environment for the storage of the oils. Pre-filter drums of new oil before use to bring them to a standard of cleanliness suitable for the machine.
Filtering Oil In Drum. Courtesy Des-Case.
Use color-coded, sealable containers to dispense the oil. Avoid leaving open containers and funnels lying by the machinery, but make provisions for storing the sealable top-up containers in a cupboard nearby, and ensure these are taken away when empty to be cleaned and refilled.
Use a small dispensing bottle for constant-level oiler bottles to minimize waste and spills, and ensure this is also sealed when not in use. For grease guns, use a dedicated gun for each grease type and use the cartridges to minimize contamination where possible.
Only use the larger 20/25kg pails of grease with a proper dispensing pump, and keep the unit sealed at all times. Identify the grease guns and pumps using color electrical cable ties in line with the grease color coding structure.
Set-up for Dispensing
Avoid using funnels and instead use hand pumps and snap-on connectors to ensure the oil is not contaminated during the dispensing. Ensure the fill ports and grease fittings are clean before use, and use color-coded dust caps on these.
Set-up for Inspection
Many units will have simple check plugs, port-hole level gauges, or dipstick. This can be improved by fitting a combination sight glass and drain that will allow inspection of the oil right down to the lower level where water may be sitting. If using an external sight tube gauge, ensure this is vented to the breather via a tee-piece to minimize contaminant ingression.
Bottom Sediment and Water Bowl. Courtesy Des-Case.
Alternatively, bottom sediment and water inspection bowls can be fitted at the unit’s base to check for water, sludge, or sediment levels.
Combine these fittings with oil sampling ports with an internal extended tube arrangement to avoid drawing sediments and sludge from the base. This will allow sampling on the run rather than stopping and inserting a tube into the unit.
Seals
Standard lip seals are a low-cost item but require frequent replacement, and their performance deteriorates over time as they cause wear on the shaft where they rub.
Mechanical and magnetic seals cost more initially but minimize dirt ingress and shaft wear, saving costs long-term.
Although mechanical and magnetic-type seals initially cost more, their superior performance will ensure minimal water or dirt ingress risk and minimize shaft wear, lubricant loss, and potential process/environmental problems.
Training the cleaning staff to avoid using high-pressure wash-down sprays directly on the seals is a must, although this cannot always be avoided in food and drug-related environments. In this instance, a seal guard can prove beneficial.
Breathers
Vent plugs serve their purpose but will not stop destructive 10µm particles. The upgrade to the breather should minimize the ingestion of hard particulate and moisture. A good quality breather, such as a 1µm-rated spin-on filter canister, will remove as much airborne particulate as possible.
If in a moist environment, then the use of desiccating breathers is advisable. However, on pumps, there is little actual need for breathers. Generally, they allow for volume changes due to top-ups, leakages, and temperature-related air pressure changes. The ideal breather form for applications with minimal volume changes is a bladder-type sealed unit.
This effectively seals the internal of the unit from the atmosphere, but a small bladder allows for expansion and contraction of the air within due to temperature changes. These are especially ideal where high levels of particulate or moisture occur in the environment.
Portable Offline Filtration
Generally, oil-lubricated pumps can benefit from the use of a filter cart. Filter carts can be applied by replacing the fill and drain plugs with snap-on quick connectors. The use of periodic portable filtration will then deal more effectively with contaminant ingression, minimizing the need for frequent oil changes, assuming the oil is not contaminated by the pumped fluid.
Periodic portable filtration combats contaminant ingress effectively, reducing the need for frequent oil changes.
The filter carts should be selected for easy maneuverability and allow for a selection of filter ratings (including small amounts of water removal) within the design constraints of the pump on the cart. If you are operating a sampling and analysis program, collect the samples before filtering.
Remember that these filter carts are non-intrusive and best used while the unit operates at higher temperatures. However, ensure that there is not too much level of loss when engaging the cart, which may be detrimental to the asset. At least 5 to 7 times the volume of the oil in the system should be passed through the filter cart to ensure adequate cleanup.
Mist Lubrication
That is mist, not missed, lubrication. In pure mist designs, the bearings are lubricated by a ‘total loss’ mist of oil droplets. This eliminates the potential for damage from oils with moisture and solids and the risk of bearing damage from oil contaminated by the pumped fluids leaking into the housing. The mist also generates a positive pressure within the bearing housing, reducing the risk of moisture and solid ingestion from the atmosphere.
Benefiting from the Changes
If spread over three years, the above changes are not onerous and are easily adapted to the pumps. Those companies that have made the changes often state that the lubrication technician’s job is now easier and safer. They also have better control over the lubrication tasks and keep better records of how much oil is being used, while wastage from leakages and spillages is minimized.
