What's the matter with the false bottom in the lauter tun of the brewery equipment being scraped by the rake?
Here's a message for help from the brewers at PROBREWER. In the use of brewery equipment, he encountered the problem of the false bottom being pulled up by the rake in the lauter tun. I would like to try to analyze this type of problem based on years of experience in beer equipment processing and the feedback I have collected from our equipment users over the years. It is hoped that more brewers can provide some methods and inspirations for the use of equipment, so as to avoid unnecessary damage to your brewery beer equipment and the resulting brewing and economic losses.
We have a 10 BBL 3 vessel Bohemian Brewery system that has a single blade rake that has been causing us issues. At some point in the past, the brewery personnel had disabled the variable speed ability of the rake so it only goes one speed: Warp Factor 5. We are looking into getting this fixed at some point but due to time, money, and lack of knowledge how to fix it, we can't do that right now. Here is my issue. Before I start to dough in my grains I activate the rake and add in about 1/3 of my mash water. Adding in some rice hulls and then the grains and more mash water. At some point around 3-5 sacks of grain I can hear a loud bang and I know that the rake has pulled up one section of my 4 screens. As it is, I have some issues with the edges of the screens letting too much grain pass to the bottom and plug up my drains. Well you can imaging what happens when a whole section gets pulled up and does not sit back down. Has anyone dealt with an issue where your rake pulls up a section of your screen? It is hard for me to imagine how much force/suction is required for that as I struggle every time I remove and replace the heavy suckers. Looking for advice to my dough-in procedure to minimize that suction that is pulling up the plate.
Why does the rake hit the false bottom/false bottom?
There are generally two reasons why the rake of beer equipment touches the false bottom: First, there are problems with the design and fixing method of the false bottom itself. The second is the process of worlauf.
Reason One: Design of the false bottom
Let's first analyze the first reason, the design of the false bottom itself. The false bottom in the lauter tun is mainly to prevent the spent grains from passing through the false bottom, while allowing the liquid wort to flow through the false bottom. The gap of the false bottom is generally 0.7 mm on the front and 1.5 mm on the bottom. A picture of the false bottom is below. Usually false bottoms need to meet several basic requirements. The false bottom has a strong ability to withstand the spent grains, and the design capacity of the false bottom is usually 160-170kg/m2, and now it is usually required to be 200kg/m2. Equivalent to two adults standing on a one square meter area. Constrained by the processing level and cost, the thickness of the false bottom is usually 4-6 mm. For the function of the false bottom, it is still relatively thin, not to mention that the surface of the false bottom has slits that have been cut. This makes the false bottom easily deformed during use.
Once the force is uneven and deformed, the edge of the false bottom will be lifted. In order to make the grain rake work better in the filter tank, the distance between the grain rake and the surface of the false bottom will be 20-30mm. Once the raised edge exceeds this distance, the grain rake will touch the false bottom. This is a hard contact without any buffering, and there is a high probability that the false bottom will be lifted directly. If not dealt with in time, this problem will become more and more serious, thereby destroying the false bottom to a greater extent. Serious and almost irreparable, and also damage the grain rake and the reducer of the grain rake.
What should be considered in a good false bottom design?
In order to avoid the deformation of the false bottom due to uneven force, enough attention should be paid to the design of the false bottom. The following points need special attention:
1. The false bottom should have enough support points and the distribution should be even. Calculate the support number and distribution of the false bottom according to the weight of the spent grains required by the process. We will control the distance between the support points of the false bottom within 20cm.
2. There should also be support around the false bottom. This is especially important. Many designers and processors of beer equipment often overlook this because of the difficulty and cost of processing. The support around the false bottom can effectively avoid the pressure deformation of the false bottom due to the force on the edge.
3. There must be fixed pins at the support of the false bottom. The edge of the false bottom should be fixed with the support at the bottom, and the edge should be pressed with screws to prevent it from lifting when under force. Of course, this does not affect the easy disassembly function of the false bottom. We usually configure small tools to easily open the false bottom for cleaning.
Reason Two: Wort lautering operation
The second is the reason why the beer filtration process operates. No matter how much pressure-bearing capacity the false bottom has, it also has a limit. There is a phenomenon called negative pressure in the filtration operation. When using the pump for wort filtration, if the grain bed on the false bottom is very strong and the wort cannot pass through, the pump is still running at this time, which will easily cause the bottom of the false bottom to be in a negative pressure state. In the state of negative pressure, the weight or pressure of the false bottom has far exceeded the weight of the grain itself, which may reach several times or even ten times the force (there is no data calculation here, just to illustrate the power of negative pressure) . Under such a large pressure, it is conceivable that the false bottom will collapse and deform. Even some tanks with thin steel plates will bulge upwards at the bottom.
How to avoid negative pressure during work lautering?
Usually to solve the problem of negative pressure, we will do the following operations.
One is to be very careful when vorlauf, so that the flow of wort is controlled in a relatively slow state. In this way, the grains bed will not be compacted and negative pressure will not be generated. Some will also add a sensor to measure the liquid at the wort outlet. If there is no liquid, the pump will stop. This is also a way to protect the pump and the tank. But this method is not very helpful for the process operation and is the last security guarantee.
The second is to use the wort balance tank, which we also call Wort Grant. The wort flows to the wort balance tank by natural gravity, and the pump draws the liquid from the wort balance tank. The wort balance tank is connected to the outside world or the lauter tun. It is in a normal pressure state, and there will be no negative pressure phenomenon. Our wort balance tanks usually use transparent glass, so that the liquid level and the flow rate of the wort can be observed at any time, which is very helpful for the process operation of the filtration process.
The above is a brief description of this problem in the use of brewery beer equipment. These points of view are from the equipment manufacturer's point of view. We also welcome the vast number of brewers and beer equipment users to visit Tiantai's discussion community to put forward your views. Sharing together makes beer brewing more fun.
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