# How To Avoid Compaction Of The Grain Bed Using A Pump?



## Pumpy (12/4/09)

I have been considering the use of a 'Grant' to go under the Mash tun !

A Grant is a small vesssel holding a few litres of runnings from the mash tun and ensures the pump is only gravity fed ,So the pump cannot suck down and compact the grain bed 

There seems a bit of work in making one ,a re they worth making ?

Does anyone use a Grant have you a picture of one you might share ?

Pumpy :unsure:


----------



## Frank (12/4/09)

Pumpy said:


> I have been considering the use of a 'Grant' to go under the Mash tun !
> 
> A Grant is a small vesssel holding a few litres of runnings from the mash tun and ensures the pump is only gravity fed ,So the pump cannot suck down and compact the grain bed
> 
> ...



I don't use a Grant, but if you are concerned, another method to try is putting a T piece on your tap at the base of the mash tun, with a clear tube facing up. Just like a large site glass, the top is open to the air, ensure your flow rate is maintained at about 50mm difference in height to your liquid level inside the mashtun. If you pump too hard the level will drop and eventually suck air.
I hope you can picture what I am saying. I don't actually use this method, I just circulate enough to get the wort back on top, quite slow.
Make sure you reduce the flow of the pump on the discharge side not the inlet.


----------



## Pumpy (12/4/09)

Wow that is a good idea Boston .

otherwise like you say perhaps I shoulds be restricting the flow of the wort on the discharges side of the pump more !

Pumpy


----------



## kevnlis (12/4/09)

Pumpy said:


> Wow that is a good idea Boston .
> 
> otherwise like you say perhaps I shoulds be restricting the flow of the wort on the discharges side of the pump more !
> 
> Pumpy




I am not so sure it is a good idea, because of certain oxidative reactions in the mash liquor it is generaly a good idea to avoid any aeration. If you have a problem with the pump running too fast, perhaps you simply need a smaller pump, or larger mash tun


----------



## Online Brewing Supplies (12/4/09)

Boston said:


> I don't use a Grant, but if you are concerned, another method to try is putting a T piece on your tap at the base of the mash tun, with a clear tube facing up. Just like a large site glass, the top is open to the air, ensure your flow rate is maintained at about 50mm difference in height to your liquid level inside the mashtun. If you pump too hard the level will drop and eventually suck air.
> I hope you can picture what I am saying. I don't actually use this method, I just circulate enough to get the wort back on top, quite slow.
> Make sure you reduce the flow of the pump on the discharge side not the inlet.


A differential sight gauge, they are a great indicator of how hard you are sucking down that grain bed.You first have to mark you starting level on the sight tube then watch the difference.Its good.
GB


----------



## razz (12/4/09)

Pumpy said:


> Wow that is a good idea Boston .
> 
> otherwise like you say perhaps I shoulds be restricting the flow of the wort on the discharges side of the pump more !
> 
> Pumpy


I find restricting the wort flow out of the pump by far the easiest and simplist method Pumpy. Happy Easter to all by the way. I continous sparge and manage to maintain a fairly "soft" feel to the mash whilst running sparge water in the top and wort out the bottom.


----------



## jjeffrey (12/4/09)

razz said:


> I find restricting the wort flow out of the pump by far the easiest and simplist method



+1. use a globe valve (or gate valve if you can't get a globe valve) rather than a ball valve to restrict flow- you'll get much better flow adjustment.

I used to have grain bed compaction problems with my pump until I used better valves on my outlet to restrict flow. gently does it. I use a pneumatic diaphramn pump rather than a march pump, cause you can tell how much flow you're getting based in how fast the pump runs (no need to open up the tun to watch).

Most commercial breweries use a differential pressure guage and/or transmitter, combined with pump speed control to control pressure drop across the grain bed. I have found that, on a homebrew scale, the tappings are a pain in the bum to clean. As Kevlis and others said, you do also run the risk of sucking air in (not good).

jj.


----------



## Pumpy (12/4/09)

razz said:


> I find restricting the wort flow out of the pump by far the easiest and simplist method Pumpy. Happy Easter to all by the way. I continous sparge and manage to maintain a fairly "soft" feel to the mash whilst running sparge water in the top and wort out the bottom.






jjeffrey said:


> +1. use a globe valve (or gate valve if you can't get a globe valve) rather than a ball valve to restrict flow- you'll get much better flow adjustment.
> 
> I used to have grain bed compaction problems with my pump until I used better valves on my outlet to restrict flow. gently does it. I use a pneumatic diaphramn pump rather than a march pump, cause you can tell how much flow you're getting based in how fast the pump runs (no need to open up the tun to watch).
> 
> ...




Happy Easter Razz must try the 'Continuous flow' I am unsure if I can do it with my pump configuration , as I use the pump to transfer liquids from the tun to the kettle .

JJ is this a pic the type of Globe valve you use ?

pumpy


----------



## jjeffrey (12/4/09)

Pumpy said:


> JJ is this a pic the type of Globe valve you use ?



looks similar. I use a 1/2" "Mars" globe valve, which is basically a mass-produced cheapo valve made in Taiwan. Stainles steel seat- no rubber or teflon (food grade valve). Means it will handle boiling water no probs for cleaning and no crevises for nasties to hide in. You should be able to throttle your discharge- just open it up when you transfer to the kettle (as required- if I open mine fully I compact the bed too much and get stuck).


----------



## roger mellie (12/4/09)

jjeffrey said:


> looks similar. I use a 1/2" "Mars" globe valve, which is basically a mass-produced cheapo valve made in Taiwan. Stainles steel seat- no rubber or teflon (food grade valve). Means it will handle boiling water no probs for cleaning and no crevises for nasties to hide in. You should be able to throttle your discharge- just open it up when you transfer to the kettle (as required- if I open mine fully I compact the bed too much and get stuck).


Is this a stoopid question - why don't u throttle the suction? 

Or is this the limitation of a centrifugal pump ? 

Never have this problem with a positive displacement pump.

RM


----------



## NickB (12/4/09)

If you're using a March pump, never throttle the inlet, only the outlet. If you throttle the inlet you risk burning out your pump prematurely!

Cheers


----------



## porky (12/4/09)

roger mellie said:


> Never have this problem with a positive displacement pump.
> 
> RM



With a positive displacement pump the problem is just the opposite. If you restrict the flow out you will over load the pump or burn it out.
You should use a bypass to control the flow, meaning sending some of the liquid back into the original container, so the pump sees the same volume all the time.

Cheers,
Bud


----------



## Frank (12/4/09)

kevnlis said:


> I am not so sure it is a good idea, because of certain oxidative reactions in the mash liquor it is generaly a good idea to avoid any aeration. If you have a problem with the pump running too fast, perhaps you simply need a smaller pump, or larger mash tun



The idea with this method is that air will not get sucked down the T piece, if you set the flow of your pump correctly, approx 50mm displacement. If air does get sucked into the pump, it will stop working straight away.


----------



## newguy (12/4/09)

I've never had grain bed compaction issues and I run my pump wide open. I have 1/2" ID lines except for my HE which has a 3/8" ID. I think it helps restrict the flow and is partially responsible for me not having a compaction issue.

In my mash tun I have a 12" perforated SS false bottom. My mash tun is a 64l aluminum cooking pot with a flat bottom. I have a pickup tube running from the false bottom up & over to the side via a SS tube where there is a weldless valve assembly. To brew I place a flat rubber washer from a garden hose on the bottom of the pot, off centered with the tube. It's simply there to prop the tube up off of the bottom so that flow is never impeded by the tube itself sucking to the bottom. The false bottom goes on top of the washer, then the tube goes into place in the hole in the false bottom. There is another circular washer on the tube to prevent husks from being sucked in at that junction.


----------



## Jazzafish (12/4/09)

I also have a ball valve on my pump outlet. I start with the valve craked a little and slowly open it as the recirculation progresses. Works fine, no stuck mashes yet.


----------



## jjeffrey (12/4/09)

budwiser said:


> With a positive displacement pump the problem is just the opposite. If you restrict the flow out you will over load the pump or burn it out.



True, except if the positive displacement pump is a diaphramn pump. In this case, the pump will stop when the outlet pressure matches the air supply pressure. So, pneumatically driven pumps that are positive displacement are ok the throttle on the discharge, so long as your discharge fittings can handle the pressure you are running your airline at.

The reason why it's not a good idea to throttle on the suction of ANY pump is because of the Net Available Suction Head required (NPSHr) to avoid cavitation- ESPECIALLY when dealing with hot fluids. 

Cavitation is when you get gas bubbles forming in the casing of the pump, which reduces it's ability to transfer momentum from the pump impeller to the fluid. Eventually what happens is you loose your prime, so that the impeller is moving around but no flow. You can tell cavitation is occuring because it sounds like the pump is trying to pump gravel.

When you apply a restriction to the suction side of a pump, you put the fluid immediately upstream of the pump under a vacuum (or to be more technically correct, a lower absolute pressure). The lower the pressure on the fluid (pressure- kPa is proportional to head- metres) the lower the boiling temperature of the fluid. If you place the fluid at a low enough pressure it will boil, forming bubbles (ie- the pump cavitates). This is especially important when you are pumping fluids that are hot, because you only have to reduce the pressure a little bit to cause cavitation. If you try and pump boiling wort around, for example, you will get cavitation just because of the pressure drop in the hoses.

Why does cavitation cause your march pump to burn out? Because there is not enough fluid passing through the pump (lots of bubbles due to cavitation, very little liquid) to transfer away heat that is generated in the coil in the housing as well as the additional friction of the impeller slug against the casing, causing it to overheat.

You should minimum the number of valves, fittings and hose on the suction side of a pump to prevent cavitation. You should also make your suction hose as large a diameter as practical.

jj.


----------



## redbeard (12/4/09)

Pumpy, dont u have a SS bucket ? why not drain into that and pump out of it ?


----------



## Pumpy (25/4/09)

redbeard said:


> Pumpy, dont u have a SS bucket ? why not drain into that and pump out of it ?




Ha Ha Redbeard I do have a SS bucket and that is an excellent Idea, 

the answer has been staring me in the face all the time .

About time to put that Bling factor to a function .

Will give it a go for sure.

http://www.aussiehomebrewer.com/forum/inde...si&img=1312


----------



## technocat (26/4/09)

The March pump is a non priming pump so the flow as stated above should be controlled on the outlet. However cavitation or air getting into the system can lead to oxidization or staling of beer which shows up as a wet papery aftertaste in the beer. It is a taste not detected in the aroma or first taste and one I had problems with until a brewer put me on the right track.

Cheers :icon_cheers:


----------



## Thirsty Boy (27/4/09)

The differential sight gauge is a nice idea - it not only lets you set your pump in the first place - it allows you to see if the grain bed is compacting significantly as you go.

I will be including one on my new mash tun (when I finally get around to building it) because compaction is one of the reasons I am changing. Mind you... I discovered a bit of beta glucanase into the mash loosen things up enough so that it isn't an issue anyway, but I've bought the damn pot now so what the hell.


----------



## jjeffrey (27/4/09)

Thirsty Boy said:


> I discovered a bit of beta glucanase into the mash loosen things up enough so that it isn't an issue anyway,



TB, where do you get your beta glucanase from?

jj.


----------

