Reflux Boiler Pressure

[deeferdog]

I recently did a revamp on my still. I finally addressed all the problems and added a few features, such as wheels and finally heater control. The column is a Boka with SS scrubbers. The height of the packing is 600mm. As a still it has always worked well and it can achieve 95% with a 10% TPW, however I have always had flooding issues. Since fitting the heater control and a new boiler it has been less of an issue but I was looking for some way to indicate that the system was being overworked which in my case would lead to the liquid being held up in the column and eventually pouring out the top if I didn't catch it in time.
From reading on this and other forums the general consensus is that the liquid cannot flow back to the boiler due to the pressure of the rising vapour. Cutting back on the boiler heat will reduce the pressure and stop the flooding, but the question arises of how much to cut back?
I had an idea for one method and I tried it over the weekend. I would like to share this with anyone else who may be interested.
Because the boiler pressure is very low, I decided to detect it using a manometer which is a U tube with water in it. One end is open to the atmosphere and the other connected to the boiler.If there is no pressure in the boiler then the water level will be the same in each side of the U tube, as the pressure in the boiler rises it will try to force the water out of the tube and the level of the water will be different in the two sides of the U tube. This difference is easy to measure, in this case I used a small rule as a measuring scale to measure the distance between the two water levels.
I connected the tube to the boiler through a small cock that I could shut if things got out of hand. I coloured the water in the tube with food colouring to make it easier to see. I filled the boiler with 20L of 10% TPW, fired up the heater to 2000w (max) and sat back to watch. There was no difference in the levels until the wash began to boil, then the difference went to over 2 1/4" (60mm) of pressure. I cut back the heat to 1500w and the pressure dropped to 2" (50mm) and I further wound back to just under 1000w and the pressure dropped to 1" (25mm). Take off was just below a continuous stream and after the usual cuts I got around 1.8l of 90% distillate for a total of four hours boiling. The manometer made it easy to monitor the boiler pressure and thus the vapour pressure in the column, it was surprising, to me at least, how a small increase or decrease in power, 100w or so would raise of lower the pressure. (My power for the heater is monitored through a wattmeter from Aldi).
So, there it is. I have put up a few pics to make it clearer. I guess most of you knew all this already, but it was all new to me. Cheers.

Deeferdog

[warramungas]

You're going to have some pressure in the boiler when its operating regardless in reflux mode. It has to keep that mass of alcohol up in the column defying the laws of gravity. Not sure its a good indicator to show when its flooding as its just measuring how much weight is in the column really. The higher the measurement the more liquid its holding up.
Unless you can work out exactly at what measurement it floods but I don't think I would want that plastic tube attached to my boiler on a permanent basis.

[hillzabilly]

Deeferdog ,if I was you ,I would repack your column with less scrubbies,and see the pressure difference ,for me I found a tightly packed column gave a higher ABV but was at a much higher risk of flooding,I donot use scrubbies anymore as they were difficult to pack evenly,unlike the copper mesh rolls,and copper will always give a better flavour as it neatralizes the sulphides.Flooding can also happen towards the end of the run as the more % of water in the spirit the slower it will drain back down,a high ABV will form a stream were as a low AbV will usually break into dropplets and drain slower,she sure has all the bells and whistels tho ,if ya can eliminate the flooding issue she will be a real masterpiece.cheers hillzabilly :handgestures-thumbupleft: