Overwhelmed about testing please help!!
Overwhelmed about testing please help!!
(OP)
I need some advice from some of the reliability professionals in the room. I work for a small company in the capacity of research and development and now have been asked to develop a reliability program. My company manufactures 12V and 24V air compressors primarily for automotive, OEM and industrial applications. We have been working on a military contract for about a year or so and going through all the mil spec testing (which is a learning curve for all of us). I have a test lab (PLC controlled)on site that will allow me to run our product and log data to narrow in on and pin point failures. Frankly I am not sure where to begin. I was asked to do this to help improve our current products and help validate new upcoming designs. Anyone know of a computer program or book to assist a non-statistician in accoplishing building the foundation to a reliability program. as an FYI I am not an engineer by trade I just happen to have a very firm knowldege and understaning of most things automotive,so here I am and, needless to say,my head is swimming due to the amount of information out there that I have been looking at to help guide me through this so.....HELP! Thank you in advance to anyone who can assist me in the slightest way
Sean
Sean





RE: Overwhelmed about testing please help!!
Next, determine your limits for each "thing", i.e. output pressure +/- 2.5 PSI.
Then, figure out how to measure each thing. Use a pressure gauge that has 0.1 PSI resolution.
Finally, verify your measurement systems are repeatable and reproducible.
Hopefully, that will point you in the right direction.
RE: Overwhelmed about testing please help!!
Then get it instrumented and collect data. Stuff like:
- temperature
- pressures
- voltage & current waveforms
- on/off cycling times
- time 'on' with respect to the primary 'mission' (eg if its part of an engine installation, how many hours will the compressor be on compared to engine running hours)
- vibration inputs from the compressors mounting points
Once you have this sort of info, you can start to think about replicating the real service loading of the part with concurrent, temperature, prssure loading and vibration.
It's not easy.
Alternatively, if you're in the USA, talk to Southwest Reasearch, San Antonio. If you're in the UK talk to MIRA, Nuneaton.
Neither are cheap but both are practised at this sort of thing.
You could also sift the papers of the SAE and the UK Institute of Mechanical Engineers for service loading and reliability studies.
Once you have devised a test and achieved some results, which should include systems that have been run to failure, you'll need some help from a reliable and practical statistician. Alternately, software from someone like Fulton Findings (California, I think) to conduct your reliability analysis.
Bill
RE: Overwhelmed about testing please help!!
>> You need to understand what type of contract this is; is it a fixed price contract, or is it a cost-plus development contract. This will affect your flexibility in addressing what your contract calls for.
>> You need to find out what your company bid. Likewise, this determines what.
>> You need to find out how your products fail. Hopefully, your company keeps records? Are there others that have failed, but were unreported because the customer switched to a more reliable product? Are your competitors' products more reliable?
>> You need to look at the technical requirements of the contract. What environment is the product specified for?, what vibration, shock, temperature, voltage, etc.?
Bear in mind that a reliability enhancement program is not cheap, particularly if you're only using in-house product, since these will not be eligible as shippable product and therefore generates no income.
>> You need to have a REALLY GOOD failure analysis capability, either inhouse or outside. You need to find out precisely what fails on each and every product you can lay your hands on. Are there any common themes in the failures? That's what you're primarily looking for, since common failures are the most likely to be analyzable for weak spots. Single failures might simply not be statistically significant.
There are a number of military and commercial experts in failures, physics of failures, and highly accelerated life testing (HALT).
TTFN
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RE: Overwhelmed about testing please help!!
RE: Overwhelmed about testing please help!!
Additionally, automotive engines suffer their biggest reliability hits from startups; there might be similar effects here.
TTFN
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RE: Overwhelmed about testing please help!!
RE: Overwhelmed about testing please help!!
So that would be the basic test cycle, run the compressor to 145, rest a few minutes, dump the pressure down to 110 and crank the compressor again. Intersperse all of that with a complete pressure discharge and a slightly longer rest.
Therefore, the time it takes to pressure up from 110 to 145 would be useful information to know. Other than vibration and current draw, this might be the only other indication of wearout or pending failure. Likewise, the intermittent complete perssure cycle and pump time from 0 psi would also tell you something about the overall performance of the pump. The rate of pressure drop when the pump is resting might also tell you something about seal integrity.
TTFN
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RE: Overwhelmed about testing please help!!
RE: Overwhelmed about testing please help!!
Msquality here. Try Mil-Handbook-217. Reliability predictions. Should be on software. Minitab.
Msquality