To the best of my knowledge, the answer to your question is "No" based on your specifications and generally speaking.
As a runner up to your question I offer the following.
There are many things that influence the amount of spray powder needed like, ink properties, job coverage, UCR/GCR, paper type, stack/lift height, press-room ambient conditions, etc.
The best way to determine the minimum spray powder needed, is to reduce by half the spray setting for the first 25 sheets of a lift. Flag and note the spray setting control knob position used for those sheets with a tag on the lift. Then return your spray setting control knob back to what's normal for the rest of the lift. Of course all your lifts/stacks must contain roughly identical numbers of sheets for this test to have any meaning.
When the job is ready for backing-up or post-press, Inspect the flagged sheets for set-off compared to a lift using your standard spray settings . Compare sheets from the bottom of both your flagged low-spray lift and a normal-spray setting lift that followed it. The bottom-most sheets in the lift/stack are the most likely to set-off.
Save and attach together representative samples from both spray settings. Note the spray settings and lift/stack sizes used for each sample source along with the date and time. Optionally, note as many other press and paper variables as possible. Put them in a file for future reference.
Obviously, if there was no difference in set-off between the regular and low spray sheets, then you would use the lower spray setting for similar jobs in the future, or perhaps a spray setting somewhere between the two, or no change at all depending upon your findings.
Now every sheet-fed pressman knows that each job is different, different ink coverages, different stocks, different spot colors and therefore different minimum spray settings as well. The whole purpose of this testing I've suggested is to familiarize you with these differences and create an archival record of your previous jobs and the settings used to print them, while only placing 25 sheets at risk for each job.
If you did this spray powder test on every job you ran on a particular press for six months, I believe that you would develop quite an archive of minimum powder settings, both physically and mentally.
Alternatively, you could skip all this testing stuff and run the spray powder unit just the way you have been and deal with all the problems that inspired you to start this thread. Personally I liked the testing route and the knowledge I gained from it.
One last word of advice, anytime you change a variable on the press, ink lot/type, powder type/size, etc, etc. Use settings that you know are safe initially and then test the new variable, putting only 20-30 sheets at risk in just the same way. Better safe than sorry!
Best regards
otherthoughts
