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Yvan Richard
Posted: Apr 14, 2011 11:26 PM
Pressure Fluctuations
The other day when spraying 2lb, I noticed a huge increase in pressure. I ran back to the trailer and the gauges were at approx 1600 on my E30. The gauges were about 300 off ratio, so I did a density test and it came out at 2.42lbs/cubic foot. I know that is high, how do I bring it down a bit to improve my yield?

I talked to my supplier and they mentioned that if the foam looks good (colour) and is rising properly it will be good foam. They also mentioned that the gauges are just that, and to be more concerned to how the foam is reacting when sprayed.

When spraying walls I normally spray around 1100.

What can cause this surge in pressure? Tips to staying on ratio? (currently I am doing the following, band heater on B side drum, clean out y strainers, ensure pumps on E30 lubricated)

I know my comments can lead into many other topics, but I am more concerned with the increase pressure and making sure I am on ratio.
steven argus
Posted: Apr 15, 2011 07:26 AM
Which guage was high?

Try running your "A" pre heater 5 - 10 degrees cooler. And watch the band heater on the "B" drum. Those can get way too hot.
Craig Gifford
Posted: Apr 15, 2011 03:10 PM
What did you use...or how did you test the density?
Posted: Apr 15, 2011 09:43 PM
If outside temps are in the 50's or even 60's and you are only running band heaters on the B Side, you will get off ration 200-300 psi easily if you are spraying with a decent size proportioner. We spray a set in less than an hour with an 03 and when it is cold, we let the band heaters run at around (Band Temps, not barrel temps) 160 on the B side and 100-120 on the A side to even things out a little.

The only thing that throws me off is that you are spraying 2 pound and your density was 2.7 or 2.8, which means that you are slightly A Rich unless your density testing is not accurate.
Yvan Richard
Posted: Apr 16, 2011 01:23 PM
What you are saying makes sense to me since my A side pressure was lower than the B. Meaning the B side was not heated up enough or perhaps a supply issue.

Is there any risk on having the foam too dense? The only thing I can think of it could be too brittle, but when you cut the foam it isn't porous (odd little open pore here and there), the cells look fine.

My proportioner is a Graco E30.
Yvan Richard
Posted: Apr 16, 2011 01:34 PM
I will give this a try. Thanks
Daniel X
Posted: Apr 16, 2011 05:46 PM
High density just means lower yield, your manufacturer should have a range for acceptable densities for a given product though.

For example my foam is allowed to get as low as 1.77 lb./cubic foot and still be covered by their warranty ect. Not that I ever get that low.

You should play around with your temp and pressures, a lot of people don't do enough of their own density testing to see how big of a difference spraying too hot, or with too much pressure makes...

EDIT: the porosity you're speaking of is likely just small moisture pockets turning to steam and trying to escape when the foam is still fresh... I'm sure it's fine, in fact I find it's quite typical when spraying onto a wood substrate vs. gypsum/steel...
Yvan Richard
Posted: Apr 19, 2011 09:39 AM
Thanks, based on your respsonse does a higher temp mean the possibility of a higher density?

Does a higher pressure mean greater density or the opposite?

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