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1. General aspects of monitoring and diagnostics.

Question 1.2.

We have a small factory. Can you make an estimation whether we need a diagnostic system and will the cost of the system recoup itself? The question was asked by the participants of VAST seminar "Machine and Equipment Vibrodiagnostics".

The question is answered by Yury Azovtsev:

Discussing the recoupment problem it is worth to divide it in three parts

  1. Is it possible to reduce greatly the failures of the equipment if they are very often at your factory?

  2. Is it expedient to transfer the maintenance according to a plan to a maintenance according the real machine condition?

  3. Is there any sense in buying the equipment with built in monitoring and diagnostic systems?


The answer on the first part of these questions, viz.:

1. Is it possible to reduce greatly the failures of the equipment if they are very often at your factory?

The detailed diagnostics decreases the unexpected failures at least in several times. The quantitative evaluation of the failure decrease depends on whether it is possible to make the diagnostic measurements by inexpensive portable instruments in the points of the machines and equipment where they have to be done. If the number of inaccessible points is about 10% of all control points (a usual situation for most industries), and you cannot fix your transducer during the measurements in these points, then you can expect that the decrease of failures will be about five times, taking into account that in the inaccessible points there will be no decrease of failures.

Now about the estimated economic efficiency. From one side, the evident part of your positive balance is the net profit due to the decrease of the equipment downtime because of the unexpected failures. Evaluate this profit for 2-3 years. Besides this you can take into account the profit due to the increase of the machine operation life because you are able to control the quality of the equipment maintenance and repair, the labor consumption for the maintenance will be decreased and the number of the spare parts can be decreased too. From the other side sum up the expenses for :

  • the diagnostic system; if the number of your machine does not exceed 1000 and the number of bearing units in these machines does not exceed 4000-5000 then you need one monitoring (control) system the price of which is about $10,000.:

  • the software for detailed diagnostics of about the same price;

  • the payment for the operator for the estimated period of time.


If the number of your machines is less it is possible to cooperate with some other small enterprises.

The answer on the second part of the question, viz.:

Is it expedient to transfer the maintenance according to a plan to a maintenance according the real machine condition?

Our experience shows that the maintenance of rotating equipment according to the real machine condition enables to decrease the expenses for spare parts and maintenance by one third. But such decrease of expenses is as a rule real only when all the equipment units are controlled including those that are not accessible for measurements by portable measurement instrument (sensor). To meet this requirement it is necessary to mount permanently a vibration transducer, and if necessary other sensors, in the inaccessible points. The number of such transducers is about 10% of all units under control on the enterprise. If you want to use only the vibration transducer, and it is possible if you use our system for detailed diagnostics, then to make the system work full time the number of such permanently installed transducers can be about 300-400 units. The expenses for purchasing and mounting each transducer can be about $300-500. So your additional expenses for permanently installed sensors will be about $100-200 for each machine if the number of your machines is about 1000.

If you take into account the expenses for purchasing the diagnostic system and the payment to the operator-diagnostician then you can expect that your expenses for the transfer of your rotating machine maintenance according to its real condition will be about $100 a year per one machine that has in average 4 bearing units. If you decide to address a specialized diagnostic company your expenses can be several times more. So, if you have the number of your main and auxiliary machines much less than a thousand, think about sharing your efforts with several companies in this direction.

The answer on the third part of the question, viz.:

Is there any sense in buying the equipment with built in monitoring and diagnostic systems?

If the protective monitoring system is an obligatory one the manufacturer includes it in the supplied equipment necessarily. In the case when the monitoring and diagnostic system is only recommended in the supplied equipment it is necessary to evaluate how much you need it for the moment of its supply.

The price of an on-line monitoring and diagnostic system is comparatively high and is about 20-30 thousand US dollars for 20-30 control points. As a rule during the first years of operation the equipment is not in a dangerous condition and the system detects only in time the mistakes of the maintenance personnel. So it is necessary to evaluate the qualification and responsibility of the personnel and if it does not bother you to plan the supply of the system to the time when the equipment will work out about 50% of its specified service time. To this time several generations of monitoring and diagnostic systems can substitute each others because they are developed and improved by the same rate as the computer technology. Only the physical bases of diagnostics and the construction of the sensors will undergo minor changes. So we recommend you while making an order for a new equipment consult the manufacturer of the on-line monitoring and diagnostic systems about the requirements for preparation of the places for the transducers of monitoring and diagnostic system that the manufacturer of the rotating machinery must meet. The system itself you can install later, for example during the planned maintenance of your equipment after the guarantee period.

 

 

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