TPM - Chronic Losses 
Due to Equipment Reliability Deterioration

Enrique Mora

There are, According to the Traditional Definition In TPM, Six Main Chronic Causes Of Losses

»     Equipment failure

»     Lost Times in Changes and Adjustments (setup)

»     Times of slow production and stoppages by other work stations up or down-stream

»     Lower Speed than originally scheduled

»     Defects in process

»     Efficiency Reduction at shift or after-break starting

»      One of TPM objectives is to eliminate those problems.

We pursue: 
Zero Breakdowns, 
Zero Accidents, 
and Zero Defects…   

There are innumerable advantages of TPM in the solution of these causes.  These have been identified by the industrial engineering specialists. If we analyze them, we will see that they are simple consequences associated with a poor maintenance program.  

Failures become chronic when:

»  The remedial actions, although already predefined, have not been applied. It has been lacking the leadership environment, cooperation and determination that are obtained through TPM.

»     The production pressures do not allow implementing the corrective measurement.

»     The problem is not understood by all the people involved or is misunderstood.

»     The problem is underestimated, or there is not sufficient education/or training to understand it and to solve it.

»     In order to reduce the losses caused by the chronic failures, the characteristics of the current conditions should be investigated in detail.

These can be reduced by applying actions like: 

»     Increasing the reliability of the equipment. 

»     Improving the equipment by means of its restoration to the original conditions, or even better. This last example is when the equipment not only is in excellent condition but has been adapted to better serve the purpose in the plant. This is recommended whenever there is not loss of safety characteristics.  

»     Clearly defining the good operating conditions and making sure everyone knows them. 

»     Eliminating the minor defects in the equipment. In some cases, the maker of the equipment will support us if we contribute to his re-engineering. 

»     Systematically using root cause analysis. 

»     Educating the operators in the general knowledge of their machine, auxiliary systems and the surrounding area.  

All these aspects are covered in the Kaizen Event when implementing autonomous maintenance, base of the TPM. The result is a considerable increase of the reliability of the machine.   

The Reliability Of The Equipment, Traditional Definitions:  

The intrinsic reliability of the equipment is the index of probability that the equipment, or the system, will work satisfactorily, under the specific conditions, during a certain period of time denominated cycle of useful life. The low reliability of the equipment is the main cause of losses due to chronic failures. The reliability is determined by two factors:  Original Reliability  and  Operational Reliability…    

Original Reliability   

»     Design Reliability: The bad designs cause mechanical, electric or hydraulic failures. As a result there is a short life span of the parts; low quality or inadequate measurement and control instruments, or they may be located in inaccessible points; inadequate shape or inadequate material of the functional parts, etc.  

»     Production Reliability: It fails when the maker of the equipment didn't follow the design. The correct assembly of the parts was neglected. The dimensions or forms of the parts are inaccurate, materials, hardness or finishes of the same are out of specification. There are accumulated tolerances, etc.  

»     Installation Reliability: A faulty installation can result in vibration, torsion, and other damages to the equipment. Their causes: uneven level, misalignment, not well-wired, bad pipe, deficiency in connectors, supports, supplies, lack of flexibility, poor ventilation, etc.  

Operative Or Operational Reliability    

»     Reliability in operation and maneuvers: It can be affected by the errors of maneuvers, faulty original adjustments previous to starting and during the operation. Also, inadequate operation standards, (demand that exceeds the design, or uses different to the original design) are causes for loss of reliability. Equally the inconsistency in the daily maintenance of the equipment to preserve its basic conditions will reduce the reliability. Some minutes everyday dedicated to clean, lubricate and inspect can make an important difference. The personnel's correct training will prevent the deterioration of this reliability. 

»    Reliability in maintenance: deteriorated by maintenance errors such as the substitution of parts out of specification or the incorrect assembly by maintenance personnel. The low level or scarce technical experience can also reduce the reliability of the equipment.  The training should become a daily task, not only for the maintenance personnel, but also for the operators.    

Deterioration and Restoration 

Restoration of the equipment: The whole equipment changes or it loses its characteristics through the time.  

If the smallest alterations are not detected timely and/or they are not taken care of properly, this will lead to more severe damages in the equipment. When the small changes are neglected (traditionally referred as "normal deterioration"), they can end up developing as irreparable deterioration. It is necessary to know the acceptable limits.   

Restoration refers to returning the equipment to its original or ideal conditions, and changing the damaged parts and mechanisms. It should be analyzed carefully if some parts must only be changed, or if a system, group or complete set or kit of parts should be renewed, otherwise, the losses will continue. Example: Chains of rollers that have suffered elongation, that is to say their links are deformed by normal wear. They may have caused excessive tear in the gears or "sprockets" and if these are damaged and are not changed, they can shorten the life of the new chain.   

The restoration is not always applicable to equipment that has limitations to satisfy the new technical requirements of the market, or when the parts are scarce and the maintenance costs rise, in which case replacement should considered. As general rule of thumb, with a few exceptions, we should not conserve equipment which the maintenance cost is more than 10% of its value every year. Don't count the consumption parts as: cutting edges or knives, drill bits, cutters, abrasive disks, etc.  

There are two types of deterioration:  

»     Natural: This simply happens in spite of a good maintenance and careful operation because of the normal use. (Example: the wear of a tire with 40,000 miles) 

»     Accelerated: This happens in a shorter period of time and is generally caused by external factors. (Example: the same tire in a misaligned vehicle or misbalanced wheel, or it is subjected to extreme conditions of abuse so that it is useless or very damaged before 10,000 miles) 

The deterioration should be identified by means of inspection and corrected in the quickest way possible. Unfortunately, in many cases the efforts to stop the deterioration and to make restoration are hindered by lacking a clear knowledge or not enough information available like: 

»     Original specifications  

»     Methods to detect deterioration  

»     Procedure to measure the deterioration  

»     Procedures and appropriate resources for restoration 

»     Tools to use 

»     Information on appropriate replacements 

Most problems of Accelerated deterioration can be avoided by means of the TPM, since methods and procedures are set like: 

»      Cleaning: It is an effective way to verify and to control the good shape of the equipment, serving as a primary form of inspection. 

»     Better knowledge on the part of the operator about the normal conditions of the equipment.    

Also, when there is a good Autonomous Maintenance, the economic and human resources of maintenance are devoted to more professional aspects such as...     

»    Predictive Maintenance: The technical diagnostic to measure the deterioration in physical and chemical terms. If the conditions are out of control, they take corrective measures. To carry out the Predictive Maintenance it is also necessary to have information on: how to measure the deterioration, how to detect signs of abnormality, what the normal conditions are, where are the limits of normality and abnormality.      

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