ASTM D4177 dispersion calcs

[Tuckabag]

Hi All,
Has anyone here done any work using ASTM D4177 - 95 (2010), with particular reference to the dispersion ratio calculations?
I am working with a client, assisting them with choosing auto-sampler locations that are deemed suitable according to D4177.
According to the standard, a dispersion ration of >0.9 is considered to have "very good" dispersion, whereas a ratio of <0.4 is considered to have "poor" dispersion. The standard also recommends that a location with a ratio of <0.7 should not be considered reliable as the coalescence of water droplets invalidates the prediction technique.
The question that I (and our client) have is how do we interpret a calculated ratio of 0.7~0.9? There is no definitive answer as to whether we can consider these ratios as good, bad or indifferent. My gut feel is that they are most likely acceptable locations, though not ideal, but I don't like providing recommendations based on a gut feel!
Has anyone used these calcs before, and if so any thoughts on how to interpret ratios in this range?
Cheers.

 

[BigInch]

First. I haven't done those calculations.
Apparently ASTM says 0.9 is very good. If you don't ageee, use D 4177?
If your client's client specified it, they must have a reason, so your choice would be to meet it, convince them that value x is OK, or don't bid.

If you're asking what 0.7-0.9 means, sorry I don't know, however ASTM tests are generally there to eliminate those "gut feelings". So, either go with the numbers, or don't go at all.

I don't know what else to tell you, but I think that's how it will work out in the end, one way or another.

Independent events are seldomly independent.

 

[Tuckabag]

Thanks BigInch.
My issue was whether we can consider a ratio of 0.7~0.9 as an acceptable location according to the standard.
D4177 makes it blatantly obivous that a ratio of >0.9 is OK, a ratio of <0.4 is not ok and anything <0.7 is not to be trusted.
The reason we ask is that it may require a lot less pipeline modification to get a ratio of 0.7~0.9 than it would to get a ratio of >0.9. The client obviousy would like to explore this avenue if the standard allows locations with these ratios.
I sent an enquiry to ASTM through their website, only to find after sending it that they don't provide interpretations of their standards.......
I guess the only thing we can do to ensure we are compliant is to select a location that is >0.9?

 

[BigInch]

That's pretty much what I figured. It usually boils down to use the ASTM standard as is, or agree with your client to a modifications of certain clauses. If you try modifying, I think that you'll have to do some research into what the parameter means and how variations affect your pipeline design to have a basis for your recommended solution, if it is to be anything less than "ASTM good". Sorry I don't know anything about the parameter itself.

Independent events are seldomly independent.

 

[Tuckabag]

Thanks BigInch.
Think we will just work with designing to a ratio of >0.9. This covers our arse and also our clients as the contract with their customer/s states that the sampling must be done in accordance with D4177.
Cheers.

 

[BigInch]

Sometimes there's just not too many options. Hope it works out.

Independent events are seldomly independent.