RIMS Recirculation causing stuck sparge?

My last two brews I had a stuck sparge. I decided to upgrade my mash tun after the first stuck sparge. I went from a braid to a copper mainifold. Well, got another stuck sparge due to compacted grain bed. Once I got the grain bed stirred everything drained as normal.

I'm wondering how to avoid compacting the grain bed. During the mash I recirculate to my pump, then back to the cooler. I open the drain valve all the way, but throttle the output of the pump.

Any advice? Seems like I've established a pattern.

You may be recirculating too fast wich can compact the grainbed too much.

Do I need to slow down the rate at which I pump out? Or the rate at which I drain into the pump? Or both?

This is where I'm confused.

Dgonza9 said:

Do I need to slow down the rate at which I pump out? Or the rate at which I drain into the pump? Or both?

This is where I'm confused.

Click to expand...

Only restrict the outlet ( after the pump ). Restricting the inlet could burn your pump head up.

For my HERMS I like about 1 gallon per minute and a 1.3 q/lb mash ratio. I find this gives me good recirculation and doesn't compact the grainbed. You can test your recirculation rate with regular water, a stopwatch and a gallon container. You are doing it right, you need to regulate the flow on the pump out valve. I use a SS false bottom from NB:

http://www.northernbrewer.com/brewing/10-s-s-false-bottom.html

I like these the best for recirculation.

How do you figure out how much to open the valve each time to get 1gpm? Or do you just eyeball about how much is coming out? I'm considering the blichman autosparge to help with this issue, and the issue of maintaining equal flow.

HarkinBanks said:

For my HERMS I like about 1 gallon per minute and a 1.3 q/lb mash ratio. I find this gives me good recirculation and doesn't compact the grainbed. You can test your recirculation rate with regular water, a stopwatch and a gallon container. You are doing it right, you need to regulate the flow on the pump out valve. I use a SS false bottom from NB:

http://www.northernbrewer.com/brewing/10-s-s-false-bottom.html

I like these the best for recirculation.

Click to expand...

My mash tun is a square cooler.

Dgonza9 said:

How do you figure out how much to open the valve each time to get 1gpm? Or do you just eyeball about how much is coming out? I'm considering the blichman autosparge to help with this issue, and the issue of maintaining equal flow.

Click to expand...

Sight glass. I use my BK as a grant. I match the flow until the sight glass level equals out. I think it's much better than pumping (suction) on the mash tun. It's a gravity break. The MLT drains, via gravity, to the BK. I pump from the BK back to the MLT. I adjust the valve until the level in the BK stabilizes. I can only pump as fast as the MLT drains.

You cannot state that there is a single flow rate that is appropriate for every mash on a system. The grist composition has a substantial effect on the permeability of the mash. In addition, the permeability of the mash actually changes during the mash. It starts relatively low and becomes more permeable as the extract is drawn into the wort.

My system includes a pressure tap at the bottom of the grain bed to allow me to monitor what the pressure drop is across the bed. I find that if I keep the pressure at the bottom of the bed from going negative, I do avoid compacting the mash. That does mean that I have to vary the flow rate during the mash. But since I can see the pressure at the bottom of the bed instantly, its easy to modulate what the flow rate should be.

Adding the pressure tap is easy. Its just a standpipe that's plumbed into the bottom of the tun. The water level is equal to the water level in the tun when there is no flow in the system. The water level drops as the flow rate through the mash increases. The headloss is proportional to both the permeability of the grist and the flow rate. Since we can't adjust the permeability, we have to adjust the flow rate to avoid placing too much head loss across the bed and compacting the mash.

Are you sure the grain bed is causing the stuck sparge? You may have an airlock in the manifold. This is what caused my stuck sparge. You need to make sure the manifold is filled with liquid, not air when you drain, otherwise the siphon will not start.

Well, here's what's been going on. The recirculation during the mash is fine. But when I then drain into the kettle for the continuous batch sparge, it's a trickle and the mash tun fills up faster than I can drain it with a wide open valve.

I stirred and kind of lifted the manifold a bit and flow corrected itself and was fine for the rest of the sparge. My speculation is that without the pump suctioning it, the compacted grain bed wouldn't gravity drain.

When the grain bed compacts, the manifold will suction to the bottom of the kettle and gently prying it up will correct the problem.

I installed 1/8" spacers on the underside of my manifold to keep it off the bottom and haven't had the issue reoccur.

I use a sight glass on my pump re circulation manifold as an easy way to prevent stuck sparges.

The open top of the sight glass will prevent the pump from ever sucking vacuum on the grain bed.