The Importance of Oring Lubrication

Many sealing situations call for the minimization of frictional forces created by a seal. One method of minimizing oring friction is to introduce a lubricant. This lubricant can be of three general types:

Internal Lubricant:
A lubricating agent is mixed into the elastomer before molding. This lubricant is dispersed evenly throughout the rubber before vulcanization and lowers the coefficient of friction of not only the surface, but the entire rubber part. An example of an internal lubricant that is commonly added to elastomers is Teflon™.

Temporary External Lubricant:
A lubricating agent, generally a liquid, is applied to the surface of a molded part. This lubricant generally sits on the surface of the seal, and as such it can be removed by particular fluids or solvents. Temporary external lubricants can greatly reduce abrasion, pinching, and cutting during installation and assembly. An added benefit of temporary external lubricants is that they can act as a barrier between harmful system chemicals and the elastomer, increasing its useful service life. An example of a commonly used temporary external lubricant is petrolatum. It should be noted to that compatibility testing should be conducted before the use of a particular lubricant.  Some lubricants can swell the rubber seal material and degrade its physical properties.  An example of this chemical incompatibility is silicone lubricating oil swelling a silicone seal.

Semi-Permanent Lubricant Coatings:
Some applications may require a lubricant, but temporary lubricant greases would contaminate the assembly. For these applications different types of coatings are available that can provide good lubrication to seals without the contamination issues associated with temporary external lubricants. The term semi-permanent is used because these coatings can peel and flake over time, so they are not totally permanent. Two common semi-permanent lubricants are parylene coating and Teflon™ coating.

Comparison:
Below is a plot of insertion and actuation force for AS568-010 orings made from a standard 75 durometer fluorocarbon that has been treated with some common lubricants and inserted into an Aerospace Recommended Practice (ARP)-1233 standard oring groove and bore to show the relative decrease in forces exhibited by the lubricants.

Notes:
Standard 75 Durometer Fluorocarbon is a Viton A
75 Durometer fluorocarbon plus 8% Teflon™ mixed into the compound
P-80® is a temporary assembly lubricant

The Importance of Oring Lubrication

Despite the fact that correct lubrication is one of the most crucial aspects of a reliability programme for rotating equipment, lubrication is often perceived as a lowly job that doesn’t require much experience or skill.

Lubrication-related failures are probably the most preventable type of all failures of rotating machinery, yet it’s an area of industry that isn’t always allocated the appropriate level of attention.

Machine reliability relies on the right methods of lubrication, the right quantities and formulations of lubrication and the appropriate application procedures and intervals – and a vigilant machinery operator will be able to maximise the performance and the operating life of the equipment by adhering to a well-planned and appropriate maintenance programme.

Most people believe that lubrication is only important because it makes the parts ‘slippery’.  In reality, lubricants are substances which play a major role in bearing and machinery function and longevity by:

• Reducing wear of moving parts
• Reducing friction between rotating parts and stationery ones
• Absorbing shock
• Reducing operating temperatures
• Minimising corrosion of metal surfaces
• Keeping contaminants out of the system
• Sealing and protecting components

The incorrect choice and application of lubricants is said to account for around 40% of all machine failures, and so lubrication procedures are a critical factor in maximizing your equipment’s reliability.

To ensure optimum lubrication, it is important to use the right type and quality of lubricant, in the right amounts, at the right place and at the right time.    Once lubrication has been applied, the equipment and the lubricant should be tested to see if:

• The correct formulation of lubricant was used for the application
• Whether the lubricant solved – or merely masked – the problem
• Whether the amount of lubrication applied was correct

The need for frequent lubrication may well be a symptom of underlying machinery damage (such as wear or damage to bearings, shafts or seals) so the solution isn’t simply to lubricate to stop vibration or excessive noise.  In fact, too much lubrication can be just as detrimental as too little lubrication. Under lubrication can cause bearings to wear out before their time, whereas over-lubrication can lead to catastrophic results to the bearings or long-term damage to motor coils and windings.

It is critical to follow the manufacturers’ recommendations and use the right type and quantities of lubricant with the appropriate frequency of application that is best suited to the machinery’s optimal functioning.

An optimal lubrication programme requires vigilance, skill and experience from the operator and should include thorough checking and testing procedures using quality equipment.  Ultrasound technology has advanced significantly over the years and is ideally suited for testing for lubrication flaws and condition-monitoring of bearings.

Ultrasound technology will not only improve machine reliability and help a production line run more smoothly, the big picture is that it can help to decrease the cost of production and the cost of maintenance, enhance safety and improve quality control.  The key focus should be on finding the best technology that meets organisational needs and making sure that it delivers both financial and operational benefits.

Best practice lubrication regimes will ensure world-class machinery reliability, so it’s worth talking to an experienced supplier of technical equipment to ensure your testing and inspection procedures are up to the task.

Nexxis will customise and implement appropriate and cost-effective testing and inspection solutions that meet your financial and operational goals.  Our flexible, solutions-driven approach has helped organisations across all industries around Australia make smarter and more profitable business decisions and you can benefit from a value-driven partnership with this leading-edge technical partner by contacting us today.

Discover more about our Ultrasonic test equipment or contact us today for a no-obligation chat.

Does your rotating equipment overheat repeatedly or completely seize up? Maybe you have noticed your equipment is making more noise than before. Is your equipment smearing? Is it discolored? Rotating equipment that is not adequately lubricated will not function properly. Adhering to a regular lubricating maintenance schedule is necessary to keep your rotating equipment functioning at its optimum levels. The two largest causes of rotating equipment failure are inadequate lubrication and lubricant contamination. Properly lubricated equipment will operate for longer periods, at lower temperatures, and extending the mean time between repairs (MTBR).

The point of lubricating moving parts is to:

• Decrease or eliminate friction
• Reduce wear
• Protect from corrosion
• Absorb heat
• Reduce noise
• Prevent damage from debris

All of these results of poor lubrication lead to serious downtime and preventable costly repairs. So, do you just slap some oil in there and hope for the best? Absolutely not! The viscosity, type, method of lubricating, and the quantity are all determined by your particular equipment.

Viscosity

A lubricant’s viscosity is an important property (most experts will say it is the most important) as it ensures the load carrying ability of the lubricant is at its most effective. Viscosity is determined by your equipment’s operating temperature, rotating speed, and load. Oils with a lower viscosity will have higher shear rates than higher viscosity oils. If you use a lower viscosity oil while operating under high temperatures, the oil film will deteriorate and metal-to-metal contact will occur causing wear, corrosion, and damage. If the viscosity is high, but operating temperatures are low, resistance to flow will increase the temperature, cause overheating, breakdown of the oil film, and oxidation of the oil. Consulting your equipment’s OEM manual will help you acquire viscosity recommendations.

Types of Lubricant

The particular type of lubricant used is determined by service temperatures and operating speed. There are two lubricants used – grease and oil. Though most lubricants are petroleum-based, there are synthetic lubricants available. Both are subject to differing degrees of oxidation and deterioration, and are suitable for certain types of components and temperatures. Synthetic oil is less sensitive to fluctuations in temperature and oxidation – making it longer lasting and not needing to be changed as often. Hydrocarbon oil is more widely used, but synthetics are becoming an ever-popular choice for consumers.

Methods of Lubrication

There are different methods of lubricating your rotating equipment:

Oil Misting: Mist generator systems are centralized systems of compressed gas that is used to atomize oil. Low pressure systems then distribute the atomized oil at multiple dispersal areas for optimal lubrication. Oil mist systems are highly effective at keeping equipment lubricated and minimizing temperature fluctuations. This is the best lubricating technology available on the market today.

Grease: The lubricant of choice for most machine elements, but is limited by service temperatures. Grease has additional sealing properties and minimizes leakage and contaminants. Unfortunately, grease lubrication does not dissipate heat like oil mist and oil splash systems. Because it is highly resistant to motion, it takes longer at start-up for adequate lubrication to occur.

Oil Splash: Splash lubrication is the most common method of lubrication. In this method, parts can be in direct contact with the lubricant, or oil rings and flingers may be used. As in the mist generator systems, splash lubrication is effective in regulating temperature. Splash lubrication is at its most effective when oil is filtered and replenished regularly. With oil rings and flingers, parts are not in direct contact. The oil ring or flinger picks up oil and transfers the lubricant over the rotating parts. Oil rings and flingers require close monitoring of lubricant levels — too much oil and the ring or flinger becomes submerged and will not adequately splash the oil; if the level is low, it will not pick up enough oil to lubricate the parts.

Quantity of Lubricant

Too much lubricant and your rotating equipment must work harder to move causing it to overheat; too little lubricant, friction increases, oil film fails, metal-to-metal contact occurs, and your equipment stops operating and needs repairs. Your equipment needs the right amount of lubricant to function at its optimal level.

Keeping your rotating equipment properly lubricated will be one of the most important parts of your maintenance program. Adhering to this will ensure a longer operating life, lower service costs, and reliability of your equipment.

Houston Dynamic Service has over 35 years of experience with rotating equipment service and repair. Give HDS a call to help keep your equipment operating at its peak performance.