How to tackle lubrication problems in industrial manufacturing
Lubrication maintenance in industrial manufacturing is a job that requires years of experience, SOPs, safety precautions and attention to detail.
Moving equipment such as radial and axial bearings and gearboxes in industrial manufacturing require lubricants like oil or grease to ensure a safe operating environment (see Figure 1). Downtime due to a fault caused by wear is unsafe for the workforce and detrimental to overall productivity. Just a few hours of downtime can cost tens of thousands of dollars. For example, a bearing failure in a paper mill because of lubrication issues can result in huge maintenance and component replacement costs in addition to the lost revenue from unscheduled downtime.
Importance of lubrication in industrial manufacturing
Lubrication is essential in industrial manufacturing. It protects equipment by forming a thin film between moving surfaces. Lubrication reduces wear by minimizing friction between components. It also absorbs shock, dampens machine-produced noise and dissipates the heat generated within the bearing and down the shaft due to high-speed movement.
In addition, lubrication reduces metal corrosion by flushing away contaminants from the bearings and gears. It acts as a sealing medium against water, chemicals and other impurities.
Most industries use either of the following lubrication methods:
- Boundary lubrication: Where the two surfaces are in contact during startups, shutdowns and slow speed-operations.
- Mixed lubrication: Where surfaces are partially separated.
- Elastohydrodynamic lubrication (EHL): Where the two surfaces are separated with a thin film of lubricant such as in most rolling element bearings.
- Full fluid or hydrodynamic lubrication: When the fluid film fully separates the two surfaces. This is achieved with bearing geometry, shaft speed and oil viscosity.
According to a study, 34.4% of bearings fail due to inadequate lubrication. However, to some extent, every lubricant is contaminated with solid particulates called “asperities.” Asperities can cause abrasion and adhesion, and can weld and seize together, leading to significant damage to the two moving surfaces. To improve product quality, extend machine life and reduce downtime, effective monitoring and lubrication oil filter systems is needed to remove the particles from the equipment lubrication system.
Industries use either mineral oils or synthetic oils as lubricants for certain benefits such as higher oxidation stability and viscosity index. The food industry often uses vegetable and animal oils for lubrication purposes.
Types of lubrication systems in industrial manufacturing
Lubrication systems in industrial manufacturing can be manual, automatic, splash or pressure types.
Manual lubrication. In a manual lubrication system, the onus of maintaining adequate oil or grease levels is with a technician who uses a hand-held gun or any other similar tool. There are pitfalls to manual lubrication such as lubricating a moving machine is unsafe and not recommended, hard-to-reach bearings are difficult to lubricate and it is time consuming to observe lockout/tagout (LOTO) procedures. Inconsistent lubrication can cause overheating, increased wear, bearing damage, higher downtime resulting in higher maintenance cost and even premature failure. In addition, it takes time to manually remove guards and covers, which leads to higher downtime and labor costs.
Automatic lubrication. This is the most preferred method to ensure the highest uptime. With automatic lubrication, users can ensure the machine gets the right amount of lubricant at the right time and at the right place while the machine is still running. Automatic lubrication extends equipment life, offers optimum lubricant consumption, lowers maintenance and technician costs and significantly reduces downtime, leading to increased productivity. In addition, automatic lubrication leads to safer and healthier working conditions for the staff and is less harmful for the environment as it reduces waste, lubricant contamination and energy consumption in the machine.
Two subcategories of automatic lubrication systems are splash lubrication and pressure lubrication.
Splash lubrication systems. This process may work well for smaller machines where a rotating dipper passes through a trough filled with lubricating oil and splashes it on the moving parts such as pistons and cylinders. This automatic process is not precise and usually has some drawbacks. The dipper may lubricate some parts of the machine too much and others too little. Users may need to constantly monitor the oil level in the trough. Low oil levels can cause under-lubrication and wear in the machine. Higher oil levels can cause over-lubrication and hydraulic lock. Users need to ensure the oil has adequate viscosity. Users must regularly filter and replenish the oil, which may be a manual process.
Pressure lubrication systems. This automated process works best when you need a technically advanced and precise method in larger machines.
- An oil pump precisely distributes the lubricant to the key areas in adequate quantity.
- The lubrication system uses an oil filter that filters, recycles and reuses the oil. Replaceable oil filters can greatly increase oil and machine life without manual intervention.
- Oil viscosity is not as important as in the splash lubrication system because a pump carries the lubricating oil to the key areas in the machine.
If you want to keep the upfront cost low, a splash lubrication system is better option. However, if you need lubrication system and machine longevity, you may want to spend a bit more on a pressure lubrication system.
How to maintain your lubrication system
Start by identifying lubrication problems and causes in industrial manufacturing.
1. Lack of procedures and knowledge handover. Wherever technicians do the lubrication manually, retirement is a big problem. Outgoing technicians take with them a great deal of on-ground knowledge that cannot be taught in a book. The technicians often hold the position for decades and know every detail of their job from the sound, sight and smell the machine produces.
Lack of documented procedures and knowledge handover causes a sharp learning curve for the new staff. During this learning period, many new technicians can cause expensive and life-threatening mistakes.
The solution: Create standard operating procedures. The experienced technicians need to document the procedures into standard operating procedures (SOPs) that can be easily passed on to the new staff once they retire. These SOPs not only include ways to effectively use the lubricant but also to properly handle, store, decontaminate and dispose of it after use.
It is important to design SOPs from a long-term point of view. Rather than just noting the current practices, SOPs should include improvisations as per industry standards of machine lubrication. They also must be constantly updated.
2. Inadequate sampling points and hardware. Insufficient sampling points and hardware to check the health of the oil and the machine can cause catastrophic damage before you can take corrective action. Many plants consider oil sampling as a secondary activity and just take samples from the drain port or drop-tube method. While samples from the drain port can contain an unusually high amount of sludge, drop-tube testing requires you to take the machine out of service, which can cause many particles to settle at the bottom.
The solution: Adequate primary and secondary point sampling. You need to identify live zones in the machine from where you draw the lubricant sample to get a snapshot of the entire system. The primary point is on the main return line manifold before any return line filters in the area of the most turbulent flow. Secondary points should be in the oil return line after each lubricated component. You also need to train the technicians in proper ways to draw lubricant samples.
3. Over-greasing. Most technicians who are not well trained just point the grease gun at the bearing and work on the lever until the grease starts to purge. While this may be effective for rudimentary applications, it can be harmful to heavy machines. Over-greasing can cause higher operating temperatures, premature bearing failure and contaminant ingression.
The solution: Standardize the grease guns. It is best to standardize the grease gun so that the outflow is consistent. Only one type of grease should be used in a single gun, and the gun should be checked once a year. You should also outfit the bearings with purge fittings to allow excess grease to expel without compromising the seal.
4. Lack of proper oil or grease container labeling. Proper labeling avoids cross-contamination and helps new technicians easily identify the correct lubricant for a particular machine. Inadequate or wrong labeling can cause confusion, work outage and even accidents.
The solution: Define an easy-to-read labeling system. It is important to take time to design a proper labeling system for your plant. The best labeling system would have a color/shape scheme for each lubricant for quick visual reference. An even more advanced system may have lube labels with bar codes integrated with a central maintenance system for automatic work orders.
5. OEM breathers and dust caps. Original equipment manufacturer (OEM) breathers have little resistance to tiny particles that infiltrate into the oil. Often, these breathers are just small containers filled with steel wool or a mesh screen to block larger particles. These breathers are ineffective against particles of 5 to 10 microns and ambient moisture that can cause rust and increase oxidation and hydrolysis rates.
The solution: Replace OEM breathers with high-quality lube filters. High-quality breathers or lube and hydraulic filters can restrict smaller particles and ambient moisture from entering the lubricant. It is important to get a breather that is right for your machine and the environment.
Other common lubrication problems and remedies
Constant-level oilers are great for small amounts of consistent oil supply to the sump, but they need proper maintenance and installation.
Generic grease may not fit well with high-speed machines that rotate at several thousand RPM. As the temperature increases, generic grease can drain out of the system. It is important to use grease of suitable viscosity.
Lubrication standards in industrial manufacturing
Legislations and norms established by the environmental protection and chemical regulation agencies govern lubricant specification and consumption in the U.S. Some of the key regulatory authorities in the U.S. for lubrication standards are OSHA, U.S. EPA, REACH, CFR, ECHA, U.S. FDA and NIOSH.
Lubrication maintenance in industrial manufacturing is a job that requires years of experience, SOPs, safety precautions and attention to detail. Advanced OEM breathers and lube filters, lube sampling and grading and labeling are not an option but a necessity for any industry to avoid lubrication problems and loss of revenue.