Reliability of industrial computers is often stated of Mean Time Between Failure - in short MTBF. The larger number is better. One year has 8,760 hours. It takes 87,600 hours for a computer to operate without failures for 10 years. MTBF has big impact on the cost of ownership of computer over the years. The fewer failures is better.
There are many factors that affect reliability of industrial computers:
1. Selection of the most reliable components. Computer consists of millions of parts – one part fails and everything stops. Quality control is the key to success.
2. Good thermal design inside enclosure to assure adequate dissipation of the heat
3. Ambient temperature. MTBF I stated at average room temperature, typically 21C. As the ambient temperature rises internal components suffer accelerated aging. Computer should not operate at high temperatures for a long period of time.
4. Using hard drives for longer than 5 years.
5. Dust contamination in dirty environments affects heat removal from the internal components.
6. Poor quality processor fan that often fails.
7. Chemical contamination by presence of chlorine and sulphur in the air. These chemicals combine with the fine copper traces on the memory elements and cause shorts.
8. Using fanless computers in closed cabinets that prevent heat exchange.
9. Failure to replace air filters clogged with dust.
10. Improper long-term storage in humidity exceeding 50% RH. Oxides forms and corrosion starts over longer periods of time.
How we calculate MTBF at Transduction? We use data base records of the computers purchased by our clients. For example, computer model TR-MAX4 records show 5 documented failures per year with 500 units in the field. The total time of these computers is 8760 x 500 = 4,380,000 hours. Divided by 5 (failures) we ger MTBF of 876,000 hours. In terms of percentage failure rate is 1 %. This figure is more realistic for the mature computers as data has service records for many more years. In general, MTBF higher than 10 years is good. Even though some of our computers last 15 years, we recommend total replacement of computers after 10 years.
Most people fail to notice that cost of ownership of the computer, just like the cost of the ownership of their car is related to frequency of repairs. The fewer repairs is better. High MTBF is most desirable feature of the industrial computer because cost of interruption of the manufacturing or service may exceed price of the computer many times. Some of our clients estimate cost of one-hour stoppage to be over $300,000. Thus, the most reliable industrial computers with high MTBF should be used. They cost more than the “office” computers but save a lot of money preventing costly failures over long periods of time.
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