ASTM B117 (Salt Spray Chamber Operation) Question

[WidowMakerSB]

Currently we are in the process of running a 720 hr salt fog test in accordance with ASTM B117-02. (I know its not the most recent version) The test is scheduled to end this weekend, and the technician in charge of the parts was asking me whether or not the test can be stopped today and restarted next week to finish.
As I recall, this is not a preferred process, but can be allowed. If the chamber is purged and the fog turned off, I was under the impression that it is an acceptable procedure. Unfortunately, in my attempts to find documentation of this (looking through the spec. and searching a few other sources) I was unsuccessful.
Could someone please inform me as to whether or not this is accurate? Thank you in advance,

Stan

 

[CoryPad]

Here is an excerpt from ASTM B 117 – 03:
[blue]
11. Continuity of Exposure
11.1 Unless otherwise specified in the specifications covering the material or product being tested, the test shall be continuous for the duration of the entire test period. Continuous operation implies that the chamber be closed and the spray operating continuously except for the short daily interruptions necessary to inspect, rearrange, or remove test specimens, to check and replenish the solution in the reservoir, and to make necessary recordings as described in Section 10. Operations shall be so scheduled that these interruptions are held to a minimum.[/blue]


The section 10 part is:

[blue]The temperature within the exposure zone of the closed cabinet shall be recorded (Note 8) at least twice a day at least 7 h apart (except on Saturdays, Sundays, and holidays when the salt spray test is not interrupted for exposing, rearranging, or removing test specimens or to check and replenish the solution in the reservoir)[/blue]

While it is preferred to run continuously, it is standard practice at many testing locations to not run during weekends or holidays, and the standard recognizes this.

Regards,

Cory

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[mshimko]

I disagree with Cory's interpretation of the standard.

The first excerpt he provided clearly indicates the test should be run continuousely except for the items mentioned, and weekends were not mentioned.

The second excerpt merely states the temperature does not have to be recorded on weekends, but this says nothing about stopping the test. Putting the two excerpts together tells me the testing should continue over the weekend.

Last, the corrosion engineer in me tells me a test run for ~30 days continuous could provide different results than a test run for a total of 36-38 days, with the apparatus merely shut off for the 6-8 days that comprise the weekends.

 

[CoryPad]

Perhaps I am mistaken regarding ASTM B 117. I do know it is common practice not to run corrosion equipment over the weekends and holidays for cyclic corrosion tests like GM9540P and SAE J2334.

Regards,

Cory

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[mshimko]

Cory - I guess we'll disagree on this item.

I saw my TPOC at one of the labs we use quite a bit. He said they run all tests continuously over the weekend, with the only exception being when they remove specimans for interim observations and photographs, and even this they do in a manner to minimize any possible effects on the results.

For my part, I'll be sure to query labs performing future work to ensure tests are run continuously.

 

[CoryPad]

mshimko,

I don't think it is necessary to disagree. Continuous operation is preferred and common, but it is not universal. I think it is a good idea to learn in advance what method is used by third parties.

Regards,

Cory

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[elwoodskibum]

My interpretation of the intent of ASTM B117 is that the test is to be continuous. Most commercially available salt fog chambers I am familiar with have provisions for weekend capacity with reservoir systems. However, during long weekends or holidays, it is sometimes necessary to interrupt a test cycle. The first action that should be required, and I think this is per ISO Quality Standards, is that the final report should include any deviations from the intended test procedure. In the case of salt spray, our practice is to rinse the specimens, dry them off, and place them in a desicant chamber, or at the very least, keep them from excessive humidity. I believe this is also spelled out in a procedure I have seen, but I can't seem to get my hands on it. I have not found any adverse results in this process over the years, but I have not actually performed a side by side comparison of parts with a standard cycle and an interrupted cycle.