Lautering problems

[grnis]

Well, I have decreeesed the amount of malt by 200kg and it works better now, but 50hl to fermenter with 1 ton of malt seems more reasonable if I want a 6% beer.
The brewhouse is a 50hl one and with lower malt bill I get around 43hl per brew.

The lauter tun has rakes I can adjust the height of, so I don't think the malt load should really be a problem. Or should it? 5 hours lautering with 1 tonne malt vs 3 hours with 800kg malt...

[grnis]

Left the lauter tun to drain over night. Let's see if it's dry tomorrow, but there did not appear to be any problems sending the last runnings down the drain.

[grnis]

We have two pressure sensors. That doesn't work... so I guess that would be a good start then

[jebzter]

I don't think the pump is the issue, since I get a high flow even without using the pump.

When I open all valves from the lauter tun to the copper, the liquid goes about 3 meters above the bottom of the copper and around 1,5 meters above the liquid level of the lauter tun.

If flow slows down, and it is towards the end of your run, its not pipe size, its less likely to be a stuck mash since the viscosity is lower, it could be an air bubble. Do you have sight gauges to indicate differential pressure above and below the false bottom? With our system we do, and if I let things run as fast as they can go, it will suck air in and this could block part of your collector. Typically if flow drops off as the kettle fills, it is pump related, since gravity is helping less and less as the kettle fills. Unless you are drawing air into the collection ring of your lauter tun or for some reason you are getting bed compaction. Both would be caused by too high of flow rate on your first wort. I could see an air bubble getting in the way at your pump inlet if you use a concentric reducer. Something to try, fill your lauter tun with water only, then pump it over and see if you get the same flow drop once they even out, if it still happens, it's probably pump, if it doesn't then it is probably the lauter rate, which should start slower, and can speed up as you get closer to the end of the run. Doesn't hurt to check you pump specs, you can rule it out quickly that way.

[grnis]

I don't think the pump is the issue, since I get a high flow even without using the pump.

When I open all valves from the lauter tun to the copper, the liquid goes about 3 meters above the bottom of the copper and around 1,5 meters above the liquid level of the lauter tun.

[jebzter]

What is the maximum head pressure of your pump? Larger pipes wont help if your pump just doesn't have the power to push the wort. If you can get the pump curve , you can see what your flow rates will be with the total head you are pumping against. It sounds like your initial run off is helped by the head pressure of the liquid in the lauter tun, but when the levels in your kettle and tun start to get closer together, that pressure is balanced out. An example, a Waukesha C-100 with 11 feet of head will only pump 15 gpm ~34hl/hr, if you go to 13 feet of head, the flow rate on the pump drops to zero. If your lauter tun and kettle are at the same level then you are pushing 5m of head once the fluid level in the kettle and tun equalize, thats over 15' of head pressure, so depending on your pump this could be an issue. You probably need more HP and a larger impeller, pipe size and a grant will not help.

[HorriblePunHere]

If you're bottom feeding your kettle, you'll have that back pressure to deal with, we increase pump speed the more wort that's collected in the kettle, just to maintain the same flow rate. I don't think it's a problem on smaller systems, but on our 20BBL system, if we leave the pump on the same setting the flow progressively slows.

[grnis]

In the basement, we have all the pipe works and pumps. During lautering, the wort is collected in a 2 inch pipe from the lauter tun to a reducer to 1 inch before the lauter pump, and on the pressure side of the lauter pump we have an 1 inch pipe.
The pipe goes all the way up to the floor above so I can watch the clarity and regulate lauter speed via a valve.

This is the third brew, and I noticed that I can get a flow of around 20hl/h with the lauter pump turned off. The pipe on floor 2 is 3,5 meters above the lauter pump and around 1,5 meters below the lauter tun bottom.

Venturi effect, is my guess, and it works fine until the liquid levels in the lauter tun and copper starts to even out. Right now I can't get passed 3hl/h for the last 10hl.

Any tips on how this can be solved?
A wort grant before the pump or a larger pipe is two possible solutions I have thought of.