BG12 Low Pressure Issues

So I finished my single tier RIMS rig and used it Friday. When I got to the boil I was able to get a boil but a weak one at that if the lid wasn't on. I'm running a BG12 at .5 PSI off a Marshall two stage regulator. I have a 57 orifice in te boil kettle burner which get me 100% solid blue flames and the burner is 3.5 inchs from the bottom of the kettle. I can run the gas full open with this orifice size. I do have another one of these on my HLT but I'm running it with a 55 orifice. I found that I can't run this one full open or get yellow and orange flames.

I was hoping I could get some feedback on orifice sizing that people have used with these burners. I did use the orfice size chart as a starting point but I have foudn there alot of other factors that play into this from testing. Including that I have full heat sheilds around these burners meaing on the sides and bottom. there are 3 1.5 inch holes drilled out in three places to provide air flow.

Thanks!! I need the help!!!!!

Down size the orifice drill size to a #45 and see where the air shutter opening is when the flame tips turn yellow, if less than 75% open step down to a #43 then a #40 to reach that point. Operating the burner with a noisy blue flame is counter productive, it should be quiet and just a hint of yellow in flame tips for maximum heating effort.

Where do I get the additional orifices? I'm having similar problems with a nice flame but it takes a long time to bring 7 gallons to boil. I have the head 1.5" from the bottom of the kettle.

I'm using a stock BG12 from Agrisupply.

Any advice is appreciated.

Adjust the air shutter to get the flame tips to start to show yellow, this is best efficiency for the burner and slowest heat loss from burner flame from under the pot. The next suggestion is to start burner when 2" of wort are in bottom of boil kettle so it will reach a boil when all the wort is finally added to boil pot at the end of the sparge time ~ 30-45 minutes from start of sparge.

http://www.bigway.com/CARTgallery196.htm

Here 's a link to a site with orifices. I can tell you though that from my experience going through 5 different sizes and PLENTY of gas volume. I get about 3.5 inch solid blue flame but still take 45 minutes for a boil and it want be a rolling boiling if the lid isn't on. I called any talked to the guy that runs and makes alot of the things you see on this site and has been in propane for awhile. Its pretty clear that these burners at low pressure will not cut it. He's rating on these burners in 25,000 btu's at low pressure. I have decided to put my boil burner on high pressure which I know works well and keep my HLT and MLT on low. I had already made my stand for these burners and really not feel like changing it at this time. I have some picks up you can check out. Below is how I made orifices if you interested. I never bought any I was going to from this guy but didn't after talking with him.

So I just made my own orifices which is actually pretty easy. Acehardware has everything you need. You will need to buy a wire bit to size to like #55 is the one that I found to be the best. You buy a 1/8 brass pipe fitting and tap out the inside of it. You then buy a brass screw to fit your tap size. Drill a hole in the brass screw VERY carefully with your wire bit. Cut the head off the screw and put some gas tap on it. thread it in and you have an orifice.