Chain drives are used to transmit force and motion between parallel shafts. Many varieties of chains are in use like heavy duty roller chains, precision roller chains, flat top crate conveyors, duplex or triplex roller chains, inverted tooth or silent chains. While friction characteristics of these types of chains vary depending on construction and mounting position, there are common challenges in ensuring effective lubrication of drive chains. And special care should be taken while restarting chain drives after prolonged stoppage. Here is a quick check list of possible affects due to unplanned stoppage and remedies to ensure smooth and efficient operation of drive chains working in various operating conditions.
Chain links running dry is sure way to wear, noisy operation and breakdown. Cause for worry if you are restarting chain drives after prolonged downtime
The chain drives in industry are classified as follows:
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Chain drives operating at room temperature
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Chain drives operating at high temperatures (temperature of 80°C and more)
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Chain drives operating at dusty environments
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Chain drives operating at humid, chemical and water environments
Possible affects due to prolonged stoppage
Chains operating at room temperature, dusty, humid, water and chemical environments
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Oxidation of lubricant used due to prolonged idle time
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Formation of oxidative by products which are usually higher in molecular weight and hence forming thick deposits
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Dust accumulation on top of chains which in turn will form a paste in combination with the lubricant.
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Entry of abrasive dust particles into the outer plate / pin and inner plate / bush clearances. This can result in abrasive wear
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Corrosion within precision parts of the chain due to chemical and water attack.
Restarting after prolonged stoppage
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Clean the accumulated dust, pasty dust (mix of lubricant and dust) and oxidised lubricant with a lint free cloth. Use fast evaporating solvent like Petrol if necessary
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Check for elongation of chain in comparison with original length. If the extension is above 5 % of original length, remove links accordingly or replace chain
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Check for corrosion on chains. If severe corrosion is noticed replace the chain. In case of mild corrosion, clean the same with a cleaner
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Use specially designed high viscosity chain lubricant which has good adhesion properties and anti-wear properties
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If chain is manually lubricated, apply oil from oil can at a rate of four to ten drops per minute (depending on the pitch of the chain) in the gap between the inner and outer plates
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Allow thirty minutes time for the lubricant to penetrate into the deep friction partner (pin, bush, roller, outer plate and inner plates) before restarting the chain
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If the chain is passing through a dip system (force feed splash lubrication), check for cleanliness of the lubricant sump. If contaminated or oxidised, replace oil sump with fresh oil
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During initial phase of running check for slackness, noise, improper engagement with pinion and sprocket. If the system displays any of these symptoms, do the necessary mechanical corrections before the chain is put into regular use
Possible affects due to prolonged stoppage
Chains operating at high temperatures (above 80°C ), dusty and chemical environment
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Reduction in base oil viscosity of the lubricant due to high temperature exposure, resulting in oil bleed from the lubrication zone
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Chances of dry running, due to low presence of lubricant in the friction zone, which can result in increased wear
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Evaporation of base oil from the chain due to high temperature resulting in lubricant starvation
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Oxidation of the oil and formation of lacquer like hard adhering residues on the chain links
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In case of centralised lubrication system, nozzle direction can get off located resulting in oil spray to the non-friction areas in the chain
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Corrosion on chains exposed to chemical attack
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Accumulation of dust from the environment resulting in abrasive wear
Restarting after prolonged stoppage
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Clean old residues of lubricant, Oxidation deposits and dust using a lint free cloth. If necessary, use a fast evaporating solvent to remove the residues
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Check for presence of oil on the chain links with a tissue paper impression. If found dry, apply a liberal coating of high temperature chain oil fortified with anti-wear and adhesion improvers
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In case of centralised lubrication system, check for proper system pressure and spray pattern. Conduct the necessary corrections to ensure required spray pattern
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Check the orientation of the nozzles to ensure that the Oil and air mist is directly reaching the friction partners. Adjust the nozzle orientation as necessary
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Clean mild corrosion using cleaner, If severely corroded, replace the chain
Machine Restart Guideline
General guideline to check condition of lubricant (greases and oils) in machines after prolonged stoppage to ensure maximum performance and avoid wear damage
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Do not start any bearing in full load and maximum speed condition immediately after extended stoppage period. If possible, run the bearings under no load condition for one hour, before increasing the load and speed in steps
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Where ever dynamic or static seals are provided in the equipment, check them for hardening and brittleness. Change the seals if they have become too hard or brittle
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Equipments which are prone for mis-alignment as per maintenance records, should be checked for alignment before restarting them
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All grease guns and grease pumping equipments need to be recalibrated, before being put to use. Grease in containers to be checked for oil separation and stirred with a clean rod wherever necessary
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All oil storage drums should be checked for sedimentation and cleanliness. Thoroughly shake oil drums/ oil cans before taking oil for lubrication
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For rust removal of machine parts such as housing, bearings, gears etc, Beruclean 3849 is recommended
The recommendations are based on our books of experience and available knowledge at the time of release. The general guidelines are to check condition of lubricant (greases and oils) in machines due to unplanned stoppage that can be affected due to a combination of known and unknown factors including natural ageing, environmental impact or contamination by external impurities. For further reference and practices specific to the equipment, we suggest you to follow the machine manual or contact the Service team. This information is intended as a guide and does not necessarily represent a marketing specification. To address your concerns, please contact our Engineering Team on +91 80 66900800 / +91 9379917484
Machine Restart Guideline for Bearing
Avoid bearing failure while restarting machines after prolonged stoppage. Restarting machines without priming after prolonged stoppage can have adverse effect on the components and land you in further downtime. While there is a vast range of bearings suited for every application based on speed, load and alignment, optimal lubrication is a common yet critical requirement for efficient performance. Here is a list of possible scenarios that can adversely affect bearing performance due to lubricant starvation and remedies to ideally prep the machine before restart.
Machine Restart Guideline for Industrial Gearbox
7 Possible lubrication failure scenarios of industrial gear boxes due to prolonged stoppage. Condition of the oil prior to restarting a gearbox after a prolonged or unplanned stoppage would make the difference between smooth operation and unwanted wear as well as surge in temperature. Here is a list of possible scenarios that can adversely affect performance output of the gear box due to lubricant starvation and remedies to ideally prep the gearbox before restart. Condition of the oil is an indicator of the long-term reliability of the gear box.
The post Effective lubrication practices for smooth operation of chains appeared first on Speciality Lubricants from Carl Bechem Lubricants India.
]]>Peculiar noises and jerky movements from your conveyor chains are a signal that the lubrication set-up needs a relook.
Case Study Overview:
Berusynth CF 250 is a high performance chain oil based on synthetic ester developed for conveyor chains in plastic film stretching section of BOPP machine. The adhesive chain oil with superior penetrating properties and excellent wetting ability ensures optimal lubrication of friction partners in the chain. The special formulation of Berusynth CF 250 does not throw off or drip even at high speeds of the chain.
From solid granules to smooth thin films
In a typical plastic film manufacturing process, plastic polymers in granular form are melted and subsequently passed through multiple rolls as a woven film, intermittently cooling and heating, until the desired film thickness is achieved. The film stretching happens both length wise and also transversely. The transverse stretching involves clips that grasp the film during the intricate stretching process. Berusynth CF 250 is specifically designed for the chain conveyors of transverse direction orientation of polypropylene film stretching machines.
Performance and Reference
The BECHEM team had the opportunity to work with one of India’s leading manufacturer of BOPP films on optimising the lubrication consumption of conveyor chains at one of their facilities. With multiple manufacturing facilities and presence across the globe, the company supplies its high quality speciality films for packaging, lamination and labelling applications to top brands.
Details of the application
The high-speed conveyor chain is a critical equipment which needs to be efficiently lubricated to ensure break-down free film stretching operation. The BECHEM team in coordination with the Plant Maintenance personnel conducted a lubrication audit to observe lubrication requirements of the frictional partners in the conveyor chain.
Conveyor chain operational load and stress factors that need to be considered
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Nature of movement, example:
sliding, rolling and impact . The frictional partners in the conveyor chain and guideways are subjected to high speed sliding movement
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Relative speed
In modern machines, the chain speeds can be as high as 500 meters per minute.
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Temperature:
The conveyor chain in a typical TDO (Transverse Direction Orienter) oven, stretching BOPP film can experience temperatures anywhere between 160 to 190°C depending on the zones.
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Time:
Film stretching lines typically operate around the clock, 24 X 7 and 365 days a year unless a maintenance downtime is scheduled
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Shock loading:
Remote possibility, only in case of film tear
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Type of movement, example:
Intermittent or continuous: Continuous movement with very little start and stop
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External contamination, example:
Presence of dust, solvent, acidic or alkaline chemical, water, humidity etc. No possibility of exposure to water or alkaline/acidic media, however mild film particles in case of film tear and remote possibility of floating dust particles.
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Residue formation:
The oil should leave minimal residues as frequent cleaning of the chain links, pins and guide ways are not possible
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Material compatibility:
The oil has to be compatible with Polypropylene material and in case of incidental contact with the film, should not form marks or wrinkles on the sheet. Additionally, components in the machinery are made from special materials such as phosphor bronze, copper and grades of steel. Some of these metals are sensitive to regular oils, resulting in undesired deposits over a period of time.
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Life time expectation:
The chain oil operates on continuous loss type lubrication during regular operation. However, the lubricant should be able to provide efficient lubrication film. For example, a minimum of one hour between the friction partners in case of 30-micron film
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Evaporation rate:
With temperatures hovering up to 190 °C in the TDO oven, the evaporation rate of the oil should be low to provide extended lubrication
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Adhesion to lubricated surface:
Strong adhesive characteristics are required to withstand high speed sliding movement and resultant shearing forces
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Corrosion protection:
Good corrosion protection properties will insulate frictional partners and associated components from corrosion.
Test Results: Berusynth CF 250
Evaporation
To study performance of the product at high temperatures a simple in house procedure was followed with sample of Berusynth CF 250 and another comparator chain oil. The samples were exposed to a temperature of about 210 °C until the oil dried off.
Berusynth CF 250 after 216 hours and Comparator sample after 142 hours
The comparator sample dried off by 142 hours with only dried residue available on the petri dish. The sample of Berusynth CF 250 was still good to perform at the same time period. Continuing the exposure, the chain oil finally turned sticky adhesive kind residue after about 216 hours.
Lubrication Efficiency: SRV Test
To understand the load carrying abilities and lubricating effect of the oil under actual operating conditions of repetitive rubbing of the frictional surfaces, a SRV test was conducted for Berusynth CF 250 and two other comparators.
Operating temperature : 210°C | Duration: 8 hours
Frequency: 50 Hz | Load: 200 N
The lubrication film of Berusynth CF 250 withstands the test duration without any seizure for the complete 8 hours. However, the film of the comparator oil breaks down within 2 hours leading to seizure.
Corrosion Protection
Copper test strips were immersed for about 48 hours in samples of Berusynth CF 250 and comparator at elevated temperature of 210 °C to expedite the oil oxidation process. An oxidized layer was formed on the copper test strip of the comparator sample while there was negligible deposits on the strip immersed in CF 250.
Trial Recommendation and Result
With the lubrication audit complete and necessary tests conducted for compatibility, the product was trialed out in the TDO oven with the following parameters.
Film thickness: 30 microns | Chain speed: 240 mpm
Chain temperature at oven inlet: 123 °C (LH) and 130 °C (RH)
Chain temperature at oven outlet: 140 °C (LH) and 148 ° C (RH)
Trial Observation
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Smooth movement of chain without any abnormal noise
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Slight reduction in current consumption. Indicates, lower coefficient of friction due to better lubrication abilities of CF 250
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Smooth pumpability of oil through all pumping systems and nozzles
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Berusynth CF 250 leaves a thin oil film on the friction partners over a period of operation.
Observations: Long term usage
After a year’s continuous operation, the following observations were noted by the Maintenance team
- Smooth movement of chain without any abnormal noise
- Optimal consumption of the lubricant with no wear failure reported for chains, chain block and graphite blocks
- No residue formation on nozzles. With continuous operation, no change of nozzles for the period
- Oil compatible with Polypropylene sheet. No material compatibility issue reported
The post Are you listening to your conveyor chains? appeared first on Speciality Lubricants from Carl Bechem Lubricants India.
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