Slip slidin' away
Slip slidin' away
You know the nearer your destination
The more you're slip slidin' away

("Slip Slidin' Away," by Paul Simon, 1977)

 

WAKE UP, FRED!

It is time to finish the third and final part of "Tribology" ...

and that part is called Lubrication!

Tri... whaaat?

Tribology is the study of how Friction causes Wear ...

and how proper Lubrication helps decrease Friction so that Rotating Equipment will not get worn down between planned maintenance intervals.

Understanding the important role Lubrication plays with respect to the reliable, continued operation of Rotating Equipment saves industrial processing facilities money ... and that's important to Plant Owners!

And who exactly is responsible for the proper operation of Lubrication Oil Systems ... aka "Lube Oil Systems."

Process Operators ... like Fred who has woken up and is ready to learn!

Aha! That information explains why Plant Owners want modern Process Operators to understand the link between the impact of Wear which is caused by the unavoidable creation of Friction ...

and how proper Lubrication reduces Friction and extends the service life of expensive Rotating Equipment!

 

QUICKIE REVIEW OF THE FIRST AND SECOND PARTS OF TRIBOLOGY ...
FRICTION AND WEAR

Smart PTOA Readers who are reading the PTOA Segments in the intended sequential order learned all about Friction in PTOA Segment #177.

So PTOA Readers and Students already know that:

• Generating the PV Pressure in Rotating Equipment requires many surfaces to slide or roll by each other ... and ...
• "Friction Happens" ANYTIME two surfaces slide or roll by each other!
• The amount of Friction generated DOES NOT DEPEND UPON the area of contact between the two sliding/rolling surfaces but DOES DEPEND UPON the weight of a sliding/rolling surface (aka "The Load").
• Static Friction is harder to overcome than Kinetic/Dynamic Friction and that's why Process Operators must pay close attention to the Start Up Procedures for Rotating Equipment.

 

Next, brilliant PTOA Readers and Students learned all about Wear in PTOA Segment #178. They learned:

Wear is the undesirable removal of metal particles from the surface of a hardware component that is constantly sliding or rolling/rotating by a different surface.

 

PTOA Readers and Students also learned that:

• The amount of Wear caused by Friction depends upon the weight of the Load and the rate that the Load is sliding/rolling.
• Rolling surfaces (like ball bearings) reduce Wear by a factor of 100 to 1000!
• There are several types of Wear, all of which can be greatly reduce with proper Lubrication. For example ...

 

PTOA Readers and Students learned that Lubrication is the main line of defense to delay the impact of Adhesive Wear; one type of Adhesive Wear called "galling" is after-the-fact proof that the hardware involved was insufficiently lubricated!

 

Evidence of improper Lubrication is also the culprit when the post-mortem examination of failed gears, cams, and the rolling elements of bearings reveals the type of Wear known as Contact Fatigue.

These facts underscore the need for Process Operators to be equally vigilant and alert to the problems that can arise in the Auxiliary Systems that serve the expensive Rotating Equipment.

A "Lube Oil System" is a great example of an Auxiliary System that supports the reliable performance of major Rotating Equipment.

But, let us be truthful ...

The importance of Auxiliary Systems is overshadowed by the more dynamic operating demands of Process Unit hardware.

However ... without Auxiliary Systems and Utilities operating as expected ... no raw material can be converted into the desired, more valuable final products.

 

 

HOW PROCESS OPERATORS REDUCE ABRASIVE AND CORROSIVE WEAR

The Block Diagram of the Lubrication Oil System that was first introduced in PTOA Segment #163 can help PTOA Readers and Students understand the strategy for reducing  Abrasive Wear, a type of Wear that was featured in PTOA Segment #178.

Find the block labelled "Pumps."

Follow the arrows from the pump discharge and trace the flow through a block labelled  "Coolers" and then through a box labelled "Filters."

A poorly filtered Lube Oil can cause Abrasive Wear on sliding/rotating surfaces.

Outside Process Operators are responsible for knowing the status of Lube Oil Filters so they know when to change them out.

PTOA Segment #178 also mentioned that Corrosive Wear can be reduced by adding the proper amount of Corrosion Inhibitor into a Lubrication Oil.

The selection of Lubrication Oil and the required additives are matched specifically to each piece of process industry Rotating Equipment.

For that reason, the Mechanical Maintenance Department will select the appropriate Lubrication Oil, not Process Operators.

Yet, Knowledge is Power!

Process Operators still benefit from knowing that the Lubrication Oil used for the expensive Rotating Equipment is not randomly selected.

Wow! All of the above information describes WHY Lubrication Oil is strategically important to the operation of Rotating Equipment!

This PTOA Segment #179 features the  many important functions of Lubrication Oil ... besides reducing Friction.

 

The following PTOA Segment #180 will explain HOW Lubrication Oil separates metal surfaces apart ... and of course continues to emphasize the important role Process Operators play with respect to making certain Lubricants can perform their important functions.

 

WHAT DOES 'LUBRICATION' MEAN AND WHAT IS A LUBRICANT?

Any material that is specifically situated between two surfaces that are sliding/rolling by each other for the purpose of reducing the creation of Friction that causes Wear is functioning like a Lubricant.

In the nearby photo, a layer of common water on the plastic surface of a Slip N Slide is acting as a Lubricant. The weight of the person sliding on the inner tube is "the Load" that rubs along the plastic sliding lane.

Note that the water Lubricant is causing "the Load" to hydroplane just a bit above the surface of the plastic Slip N Slide.

The layer of water Lubricant on the Slip N Slide reduces the Friction created between the skin of the sliding person and the plastic fabric of the Slip N Slide.

Without the water Lubricant, the plastic would wear down and eventually break from multiple attempts to slide flesh on plastic ...

And Ouch!

The body of "the Load" would also experience Friction in the form of blisters ... evidence of Wear.

The point is that the term "Lubricant" can be many things:

Lubricants can be liquids like water and Lubrication Oil as has been described above.

Lubricants can be semi-solids like the Grease being applied with a Grease applicator in the nearby photo.

Lubricants can even be solids ... like the Teflon coating on cookware pan in the nearby photo.

Even high pressure air ... a gas ... can be used as a Lubricant!

And that's because ANYTHING that is intentionally placed between two sliding or rolling surfaces for the specific purpose of reducing Friction that causes Wear is a Lubricant!

 

 

 

THE MULTIPLE FUNCTIONS OF LUBRICATION OIL

PTOA Readers and Students just learned that the function of Lubrication can be performed by liquids, semi-solids, solids, and even gases.

Until otherwise noted, the PTOA focus on Lubrication is concerned with Lubrication Oil and Grease.

Besides decreasing Friction and hence Wear,  Lubrication Oils perform these important industrial functions:

 

The "Cooling Down Friction-Generated Heat" Function

PTOA Readers and Students learned in PTOA Segment #177 that Friction created by sliding and rolling surfaces also creates heat.

And PTOA Readers and Students who are reading the PTOA Segments in the intended sequential order already know about heat transfer methods because they have read the complete PTOA Focus on Heat Transfer which was included in the PTOA PV Temperature Focus Study Area.

It is time to connect some dots ... with Fred!

The Friction-created heat that occurs in any piece of Rotating Equipment will be transferred by conduction and convection into the circulating Lubrication Oil System.

Once again the nearby Block Diagram of the familiar Lubrication Oil System loop will help illustrate how the generation of heat is controlled.

Find the block labelled "Compressor Train."

The word "Train" is a hint that this block represents a set of Rotating Equipment Compressors that are in series boosting up the PV Pressure of a gas in sequential steps.

The Lubrication Oil that is supplied to and then flows through the Compressor Train eventually is drained from the Compressors and flows into the block labelled "Reservoir."

The drained Lubrication Oil is hotter when it leaves the Compressor Train because it has picked up the heat created by Friction.

The Friction heat that has been transferred into the Lubrication Oil by conduction and convection will be transferred out of it after the Lube Oil flows through the box labelled "Coolers" ... which is situated on the discharge side of the block labelled "Pumps."

A Block Diagram simply illustrates how the functions of a system are connected; the exact equipment within each block is not revealed.

 

The box labelled "Coolers" could be an Air Cooled Fin Fan Heat Exchanger like the one shown in the nearby photo. The heat that was picked up by the circulating Lubrication Oil inside the Compressor Train is continually transferred into the air!

Aha! That's how the circulating Lube Oil System performs its "Cooling Down Friction-Generated Heat Function!"

Stop Here if you are a PTOA Reader or Student that does not understand the above statements.

Your time would be better spent rereading PTOA Segments starting from HERE. Why be confused? Just get caught up!

 

The "Cleaning" and "Corrosion Inhibiting" Functions

Friction-created heat can create temperatures that allow chemical reactions to occur.

These chemical reactions can result in the formation of dinky solids (called 'particulates') which contaminate the Lubrication Oil.

The nearby photo shows Lubrication Oil used in a hydraulic service before and after filtration removed water and dirt.

Furthermore, Abrasive Wear can knock off little specs of material from a surface.

So ...

Chemical reactions and Abrasive Wear are just two examples of pathways that lead to Lubrication Oil contamination within Rotating Equipment.

To combat the formation of deposit and corrosion products, the circulating Lubrication Oil will have additives.

A partial list of common Lubrication Oil Additives includes:

Detergents are additives which prevent deposits from forming.

Dispersants are additives which prevent contaminating particles from attaching to each other ... thus making problematic big particles out of manageable small ones.

Corrosion Inhibitors are additives that lay down and renew a protective coating on metals which keeps moisture away ... and without the oxygen in water rust cannot form!

 

The "Seal Oil" Function

Every brilliant PTOA Reader and Student knows that the purpose of a Pump or a Compressor is to add the PV Pressure into the fluid that is being pumped or compressed.

Think about it!

The process fluid at the Pump or Compressor discharge will have a Discharge Pressure that is definitely greater than Atmospheric Pressure!

So the process fluid will leak through the clearance created by the shaft piercing through a housing ... unless there is a sufficient opposing pressure preventing this leakage.

Seal Oil is oil that is pumped into the Stuffing Box at a PV Pressure that prevents any other liquid or air flow into the Stuffing Box.

Seal Oil will also prevent debris and contaminants which may be flowing in the pumped/compressed process stream from entering the Stuffing Box through the shaft/housing clearance.

The nearby photograph illustrates one type of Seal Oil design.

To see an animated version of the drawing access THIS LINK.

And if that doesn't work, copy this link into your browser:

http://www.aesseal.com/en/resources/api-plans/api-plan-52

A properly chosen Lubrication Oil can perform the duo role of Seal Oil. When performing these duo functions, the Lubrication Oil will be compatible with the process fluid that is being pumped or compressed.

 

The "Transfer Force" Function

PTOA Readers and Students who are reading the PTOA Segments in the intended sequential order expertly understand that the head of any contained liquid generates a Force and hence PV Pressure ... because they calculated the Force and Pressure way back in PTOA Segment #146.

When the Force of a contained liquid is used to move an object, the movement is said to be caused by hydraulic power.

The force of hydraulic fluids can be used to transfer power ... and sometimes Lubrication Oil is used to perform the function of hydraulic oil.

Summary of Lubrication Oil  System Functions 

Wow! Lubrication Oil Systems can perform multiple important functions!

• Reduce Friction that causes Wear.
• Remove Friction-Created Heat.
• Carry Away Dirt and Contaminants.
• Prevent Corrosion and Rust.
• Seal Oil Function.
• Hydraulic Fluid that transfers Force and Power.

 

Wow! No Wonder Lubricants are specifically matched to the application of the Rotating Equipment.

Careful matching of Lubricant selection to Rotating Equipment service ...

• Improves Rotating Equipment Performance.
• Lowers Operating Costs.
• Gives Longer Service Life of Rotating Equipment.

 

TAKE HOME MESSAGES: Lubrication is the front line of defense to reduce the impacts of Wear that is caused by Friction.

A Lubricant is any material that is intentionally situated between two surfaces that are sliding/rolling by each other for the purpose of reducing Friction ... which causes Wear.  

Lubricants can be gases, liquids, semi-solids like Grease, and liquids like Lubrication Oil.

Lubrication Oils are specifically chosen for the Rotating Equipment application. The Mechanical Maintenance Shop will select the Lubrication Oil for each piece of Rotating Equipment. 

Lubrication Oil may have a variety of additives. Common additives are:

• Detergents
• Dispersants
• Corrosion Inhibitors

 

Circulating Lubrication Oil Systems may perform more than one of these important industrial functions. 

• Reduces Friction that causes all types of Wear.
• Removes Friction-Created Heat.
• Carries Away Dirt and Contaminants.
• Prevents Corrosion and Rust.
• Can perform Seal Oil Duo Function.
• May act as the Hydraulic Fluid that transfers Force and Power to move an object.

 

Lubrication Oil Systems are Auxiliary Systems that support expensive Rotating Equipment.

Without a properly functioning Lubrication Oil System, the Rotating Equipment requiring the lubrication will not function for long and will be expensive to repair/replace. For this reason, Plant owners want modern Process Operators to understand the direct link between proper Lubrication and the reduction of Friction and Wear. 

Process Operators must be vigilant with respect to optimal operation of Lubrication Oil Systems. For example, the Process Operator can:

• Reduce Abrasive Wear and control contaminants with good filtration.
• Optimize the transfer of Friction-Created Heat out of the Lube Oil with properly functioning Lubrication Oil Coolers.

 

This PTOA Segment included practice reading and interpreting Block Diagrams.

 

 

©2017 PTOA Segment 0179
PTOA Process Variable Pressure Focus Study Area
PTOA PV Pressure Rotating Equipment Focus Study

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