Unscheduled breakdown on machines is a common issue in any industry. These breakdowns can cause the production lines to be slowed down or even stopped for a few days and this can cause several damages to the plant such as late delivery, production loss, material wastes and human injuries.
A machine can be breakdown due to several issues such as:
Bearing failures due to: Excessive load, speed, overheating, mount/dismount, lubrication, contamination, corrosion, fatigue, true/false brinelling, current leakage, abrasive wear.
Vibration issues: Unbalance forces, misalignment shafts.
The best solution In order to minimise/prevent these breakdowns is developing a maintenance strategy, being a strategic mix between corrective, predictive, preventive and proactive that is optimised to meet the business objectives.
How can proactive maintenance improve Fonterra sites output?
Proactive maintenance combines root causes analysis and regularly condition monitoring. By analysing the root causes, repetitive failures from the same sources can be corrected. Condition monitoring can detect abnormal vibration in order to correct the problems before the machine breakdowns. This method will minimize the downtime cost and maximize the production time.
Why is lubrication important to Fonterra specific machines?
In most areas of the Dairy industries, equipment is subjected to frequent washdowns and applied machinery must be food-compatible. This puts very tough requirements on the lubrication and sealing in order to avoid conflicting with their performance requirements.
The main purpose of this project is facilitating the implementation of an SKF pro-active maintenance programme in order to prevent bearing failures and maximize the production time at selected Fonterra sites.
This project is a contract between SKF New Zealand and Fonterra industries. The author of this project will be supervised under AUT supervisor and SKF application engineering manager.
2.0 OBJECTIVES:
Research and understand different types of bearing, lubrication, seal, and housing. Then, select the optimum solution.
Research and understand maintenance strategies: corrective, predictive, preventive, pro-active.
Apply state-of-the-art tools for determination of reliability of rotating machinery to improve plant reliability and energy efficiency.
Develop root cause analysis skills for bearing inspection.
Develop vibration analysis skills to detect unbalance and shaft misalignment.
Apply SKF pro-active maintenance programme in order to improve the production time at Fonterra sites.
DELIVERABLES:
Bearing failures will be carefully inspected in order to prevent further costs.
Recommendations for more suitable bearings, seals, housings for specific machines.
The most suitable lubrication types as well as re-lubrication amount and re-lubrication intervals will be applied for specific machines.
3.0 TIME SCHEDULE:
CODE
ACTIVITY
DURATION (weeks)
A
Project and supervisor selection
2
B
Project's Proposal
2
C
Research bearings, lubrications, seals, housing and maintenance strategies
26
D
Research bearing failure analysis
14
E
Familiar with SKF software (lubrication planner, lubeselect, dialset… etc)
12
F
Bearing inspections
16
G
Condition monitoring & applying proactive program to Fonterra sites
22
Report writing
20
CODE
March
April
May
June
July
August
September
October
November
A
B
C
D
E
F
G
Interim Oral presentation Final Oral presentation
The total time available for this project is approximately 450 hours, divided in 29 weeks.
The first semester is equivalent to one paper but the second semester is equivalent to two papers. Therefore, more work will be involved in semester-two.
There are slacks for section C, D, E, F and "Report writing". The two semester-breaks and the three-week mid-year break will be used as back-up periods.
Regular meetings with academic supervisor and industrial supervisor will be arranged through email or phone.
Project log must be used at all time to record useful information for later use and writing the final report.
As shown in the Gantt chart, the report will be updated at the end of each month.
4.0 APPENDIX:
4.1 SKF BACKGROUND:
What does SKF stands for?
SKF stands for "Svenska Kullager Fabriken" which means "Swedish Ball Bearing Factory" in the Swedish.
SKF is one of the leading global suppliers of products and solutions within rolling bearings, seals, mechatronics and lubrication systems. It is also well known for its excellent services which include technical support, maintenance services, condition monitoring and training.
SKF was founded in 1907 by Sven Wingquist, and grew at a very fast rate to become one of the biggest global company. Today, there are more than 100 manufacturing sites and sales companies supported by about 15,000 distributors at over 130 countries.
Bearings, Seals, Mechatronics, Services, and Lubrication Systems are the five platforms of SKF's technologies. By apllying the capabilities of these platforms, SKF develop different offers for each customer demand, helping them improve performance, lower total costs, while bringing increased added value and higher price quality to SKF.
D:\Downloads\fonterra_logo.jpg
4.2 FONTERRA BACKGROUND:
"Dairy is our life's work. It's our passion and it's what we do best."
"Since Fonterra Co-operative Group was formed in 2001, they have become the world's largest dairy exporter with nearly 11,000 shareholders. They export 95 percent of New Zealand-made dairy products to the customers and consumers in more than 140 countries. Fonterra milk tankers collect around 14 billion litres of milk every year."
4.3 BEARINGS:
Bearings are an essential component of almost all machinery. The objective of a bearing is to: C:\Users\Hue\Desktop\friction.png
Reduce friction (Friction counteracts the movement between two surfaces. It is undesirable in most machines since it causes power loss, heat generation, wear and noise).C:\Users\Hue\Desktop\Industrial project\Picture\Load.png
Carry loads (A bearing can be under radial load, axial load, or a combination of both.)
Guide moving parts.
SKF has a wide range of bearing in the market such as: ball bearing, spherical roller bearing, self-aligning ball bearing, taper roller bearing, etc.....C:\Users\Hue\Desktop\1.png C:\Users\Hue\Desktop\2.png
A typical rolling bearing consists of an inner ring, an outer ring, rolling elements and a cage. Seals or shields are an optional extra, which can be added to a number of bearings.
C:\Users\Hue\Desktop\bearing part.png
4.4 LUBRICATION:
There are 2 types of lubricants: Grease and Oil. 80% of all bearings are grease lubricated because it's easy to apply, retains in the bearing and it can function as an extra seal for the bearing.C:\Users\Hue\Desktop\Factors causing bearing failures.png
Lubrication is needed to separate the rolling contact surfaces (no metal-to-metal contact), reduce friction, avoid wear and protect the bearing. Of all bearings that fail, 36% of them fail due to problems with lubrication. Therefore, it is important to choose the appropriate lubricant for different applications in order to extend the bearing life.
Once the lubrication has lost its lubricating properties, the rolling elements will make metal-to-metal contact with the raceways. Wear starts to develop and eventually this will create mirror-like finish at the surfaces. But that's not all; metal-to-metal contact between the rolling elements and the raceways will create more and more friction which leads to a huge amount of heat to be generated over a short period of time. The increasing temperature will cause the hardened material to be softened. The temperature can become as high as causing the cage to deform inside the bearing. And when the cage loses its properties, it will not hold the rolling elements to where they are supposed to be. Eventually, the rolling elements will move around and get jammed, causing the bearing to fail.
Outer ring of a spherical roller bearing
that has not been adequately lubricated.
The raceways have a mirror finish.
Cylindrical roller with mirror-like surface
due to lubricant starvation.
4.5 SKF LUBESELECT:
SKF is one of the first companies that started testing greases and analysing how lubricants deteriorate during the bearing service life. And they have developed different methods to help the customers select the best grease for their applications. The selection of lubricant depend on operating conditions such as: operating temperature, rotational speed and load.
LubeSelect for SKF grease is a web-based tool developed to select the appropriate lubricant for different applications. It processes application's parameters and provides the best lubrication advice possible, including suggested lubricant, lubricant quantity and lubrication intervals.
C:\Users\Hue\Desktop\lubeselect.jpg
4.6 ROOT CAUSE ANALYSIS:
Bearing failure due to a number of various reasons such as:
Excessive loads: cause premature fatigue. Early fatigue failure due to tight fits, brinelling and improper preloading are quite commonly known.
Overheating: The rise in temperature can soften the material and shorten bearing's life. In many cases, balls and rings will deform. The temperature rise can also destroy lubricant.
True brinelling: can be caused by static overload or severe impact. It occurs when loads exceed the elastic limit of the outer/inner ring material.
Brinell marks show as indentations in the raceways which increase bearing vibration.
False brinelling: elliptical wear marks in an axial direction at each ball position with a bright finish and sharp demarcation, often surrounded by a ring of brown debris - indicates excessive external vibration.
Contamination: Contamination is one of the most commonly known for bearing failure. The bearing raceways and balls will develop small dents which are resulting in high vibration and wear over time.
Lubricant failure: Once the lubrication has lost its lubricating properties, the rolling elements will make metal-to-metal contact with the raceways. Wear starts to develop and eventually this will create mirror-like finish at the surfaces. The temperature will rapidly rise up due to the increasing in friction can cause the cage to deform inside the bearing. Eventually, the rolling elements lose their track and get jammed, causing the bearing to fail.
Corrosion: This condition results from exposing bearings to corrosive fluids or a corrosive atmosphere. Red/brown areas on balls, race-way, cages, or bands of ball bearings are symptoms of corrosion.
4.7 MAINTENANCE STRATEGIES:
Maintenance is known as the actions which are required for restoring or retaining a system, machine or equipments to the specified operable conditions to achieve its maximum useful life span.
4.7.1 Corrective maintenance:
Corrective maintenance can be defined as a maintenance which is performed when an item of a machine has already failed or broken down. It is probably the most commonly used maintenance method but it is easy to see its limitations. When equipments fail, production lines have to be stopped and this will lead to many other costs such as: downtime cost, maintenance cost, replacement cost and it's also important to consider health, safety and environment issues related to malfunctioning equipments.
4.7.2 Preventive maintenance:
The main goal of preventive maintenance is to prevent the failures of machine's components before they actually occur. It is a schedule of planned maintenance actions aim at the unscheduled breakdowns and failures. For example, replace worn equipments before they actually fail. Actions such as: Equipment checks, partial or complete overhauls at specified periods, oil changes and re-lubrication are parts of preventive maintenance activities.
4.7.3 Predictive maintenance:
Instead of relying on industrial statistics to schedule maintenance services, preventive maintenance used vibration analysis technique to monitor the mechanical condition and system efficiency directly in order to find the actual mean time failure or loss of efficiency of the plant. Then, the final decision on repair or rebuild schedules will be made base on the basis of intuition and the maintenance manager's experience.
4.7.4 Proactive maintenance:
These days, engineers are moving toward a maintenance program which targets the root causes of machine failure. It is called Proactive maintenance. Its methods are currently saving industries millions of dollars on unscheduled breakdowns each year. In many industries, maintenance costs often exceed the annual net profit. The problem of costly maintenance has reached a serious level, but as more and more companies have realized every day, their maintenance costs can be reduced greatly by using proactive maintenance method.
4.8 SKF BEARING BEACON:
SKF bearing beacon is an advanced calculation tool used by SKF engineers to find the best solution for specific bearing arrangements. It is developed for analysis of rolling bearings in 3D graphic environment. SKF bearing beacon is the result of many years in specific research and development within SKF organization. It can solve many complicate problems such as contact pressure, deflection, model analysis, etc....
2
4.9 SKF LUBRICATION PLANNER:
A lubrication plan provides a way to formalize and keep track of the activities that lubrication engineers will perform in order to ensure:
The right lubricant
The right quantity
At the right time
At the right point
With the right method
SKF Lubrication planner is a software designed to maintain a lubrication plan for industry.
C:\Users\Hue\Desktop\Industrial project\Lubrication planner\7.png
4.10 SKF DIALSET:
SKF DialSet is developed in order to calculate the correct re-lubrication intervals settings. After selecting the criteria and grease relevant to specific applications, the program will offer us with the correct settings for our SKF automatic lubricators.
C:\Users\Hue\Desktop\DIALSET.png
4.11 BEARING SELECTION:
The selection of ball and roller bearings for a given installation depends upon the following factors.
Available space
Loads
Misallignment
Precision
Speed
Quiet running
Stiffness
Axial displacement
Mounting and dismounting
Integral seals
Different bearing type has different characteristic properties and design which makes it more or less suitable for different applications. For example: let's look at deep groove ball bearings which are the most commonly used bearing in the world. They can accommodate both radial and axial loads at a moderate amount. They have very low friction due to the point-to-point contact between the rolling elements and the raceways at the surfaces. Therefore, they can be used in quiet running applications such as: fan, air- conditioner, small and medium sized electric motors.
On the other hand, spherical and toroidal roller bearings have line-to-line contact surfaces between the rolling elements and the raceways. Therefore, They can carry a very large amount of radial load. And the special design of the rolling elements gives them the abilities to accommodate moderate misalignment as well. These properties make them suitable for heavy applications where there are heavy loads and shaft deflections or misalignment.
4.12 CALCULATIONS:
Bearing Life:
The equation for SKF rating life is in accordance with ISO 281:1990/Amd 2:2000
Lnm = a1 aSKF L10 =a1 aSKF (C/P)p
If the speed is constant, the life can be expressed in operating hours, using the equation
Lnmh = a1 aSKF 106/(60n) L10
where
Lnm
=
SKF rating life (at 100-n1)% reliability) [millions of revolutions]
Lnmh
=
SKF rating life (at 100-n1)% reliability) [operating hours]
L10
=
basic rating life (at 90% reliability) [millions of revolutions]
a1
=
life adjustment factor for reliability (table 1)
aSKF
=
SKF life modification factor, (diagrams 1, 2, 3 and 4)
C
=
basic dynamic load rating [kN]
P
=
equivalent dynamic bearing load [kN]
n
=
rotational speed [r/min]
p
=
exponent of the life equation
3 for ball bearings
10/3 for roller bearings
Friction moment - power loss:
SKF has created a new model for calculating the frictional moment. It has become a more accurate calculation for the frictional moment generated in SKF rolling bearings. The equation is.
M = Mrr + Msl + Mseal + Mdrag
C:\Users\Hue\Desktop\Friction.png
Minimum load:
In order to achieve the satisfactory operation, ball and roller bearings shall always be used up to a given minimum load. The "rule of thumb" indicates that roller bearings and ball bearings should have a minimum load of 0.02 C and 0.01 C respectively.
C:\Users\Hue\Desktop\minimum load.pngC:\Users\Hue\Desktop\minimum load 2.png
Relubrication intervals:
The re-lubrication intervals tf for bearings with rotating inner ring on horizontal shafts under normal and clean conditions can be obtained from diagram 4 as a function of
-
the speed factor A multiplied by the relevant bearing factor bf
where
A
=
n dm
n
=
rotational speed, r/min
dm
=
bearing mean diameter
= 0,5 (d + D), mm
bf
=
bearing factor depending on bearing type and load conditions
-
the load ratio C/P
C:\Users\Hue\Desktop\Diagram 4 - relubrication intervals.pngC:\Users\Hue\Desktop\Relubrication.png
Shaft tolerances and resultant fits:
Dimensional tolerance is a designed in clearance between two parts. For example, a nominal diameter of a shaft is 20 mm have a sliding fit within the hole, the shaft might be assigned with a tolerance range from 19.928 to 20 mm and the hole might be assigned with a tolerance range from 20.08 mm to 20.152 mm. This would provide a clearance fit between 0.08 mm and 0.224 mm. In this case, the tolerance range for both the shaft and hole is chosen to be 0.072 mm.
C:\Users\Hue\Desktop\Shaft tolerances and resultant fits.png
Housing tolerances and resultant fits:
The fit between the inner ring and the shaft as well as the fit between the outer ring and the housing must be suitable for different applications In order for a ball or roller bearing to perform satisfactorily. For example, too loose of a fit can make bearing bore and shaft to be corroded, while too tight of a fit will require larger mounting and dismounting forces.
C:\Users\Hue\Desktop\Housing tolerances and resultant fits.png
