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Old 04-29-2011, 12:06 AM   #1
brewfeller
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Default March Pump mounting ?

I am having trouble with my March pump cavitating. It seems overly difficult to get primed. It is the center input version of the pump. it's supposed to have better throughput compared to the regular version. I have it mounted horizontally. I have seen people mount them vertically. does it make a difference? What can I do to improve the odds of priming the pump correctly without cavitation?

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Old 04-29-2011, 01:28 AM   #2
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I am having trouble with my March pump cavitating. It seems overly difficult to get primed. It is the center input version of the pump. it's supposed to have better throughput compared to the regular version. I have it mounted horizontally. I have seen people mount them vertically. does it make a difference? What can I do to improve the odds of priming the pump correctly without cavitation?
IMO & IME, priming these pumps is no problem at all if you have the plumbing configured properly. Obviously, the pump should be mounted at the lowest point in the system. Add a small bleeder valve on the output side of the pump between the flow control valve and the pump head. Horizontal mounting should be fine. Position the output port up if possible. To prime the pump, close the flow control valve and open the bleeder valve fully to purge any air in the pump head. The wort/water or whatever should flow easily to the pump head and flood it. Any entrapped air in the pump head or hoses should get pushed out by the incoming flow of liquid. It has to unless there is some other restriction in the circuit. I do this with the pump turned on, but you can also start with the pump off until you get some liquid coming out of the bleeder valve by gravity flow alone. When you have a very strong flow established from the bleeder valve, you can close it and open the flow control as required.

Here's some key points:

1. There must be sufficient vertical drop from the kettle outlet port to the pump intake port. More is better, but it's best to have at least an 8-12" drop and preferably a little more.

2. Use large inside diameter hose (1/2" or larger is good). Beware of restrictions caused by fittings, particularly the barb type. IOW, use large I.D. fittings and keep the elbows, etc to a minimum.

3. Use the shortest hose lengths as conveniently possible, particularly on the suction side of the pump. This is probably the the most common mistake. These pumps don't have a lot of power to spare, so minimizing resistance to flow any way you can will help a lot. Not a little; a lot.

4. Having the flow control valve closed when bleeding the system is important.

5. Make sure you have no air leaks on the suction side. This should be obvious.

If you continue to have problems, post some pics of your system and we might be able to spot something. Good luck with it.
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Old 04-29-2011, 01:35 AM   #3
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I forgot that you mentioned cavitation. Can you describe the circumstances/conditions when the cavitation occurs? What are you pumping and where when it happens? Unless you are trying to pump near boiling water or wort, cavitation is an indication that there is a major restriction on the suction side of the pump. Sometimes an abrupt and large change in pipe or hose diameter can cause cavitation when pumping at a high rate. I doubt that is the problem, but it could be. I'm gonna guess that there is a leak somewhere on the suction side and you are sucking air in. Can you see bubbles in the suction hose? That's what I always look for when checking for leaks.

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Old 04-29-2011, 03:41 PM   #4
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make sure the ouput is higher than the input. it will look like this _O-

I realize you have a center input to the pump but one side will be higher than the other. Also make sure you never restrict on the input side of the pump. i have a ball valve on the output and close it a good bit.

I just mounted my pump for the first time this week and have not brewed with it but did a fair amount of reading about it.

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Old 04-29-2011, 04:39 PM   #5
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Not to high jack the thread but I have heard multiple times that near boiling fluids or boiling fluids can lead to cavitation. Is it advised not to pump fluid at these temps? I ask because I would like to recirculate during the boil to sanitize the pump prior to chilling.

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Old 04-29-2011, 04:46 PM   #6
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i think everyone does just that. I have not done mine yet, but i think this is a very standard practice.

That is also why having the output higher than the in is important. It allows the air to escape as much as possible.

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Old 04-29-2011, 04:47 PM   #7
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Quote:
Originally Posted by Scut_Monkey
Not to high jack the thread but I have heard multiple times that near boiling fluids or boiling fluids can lead to cavitation. Is it advised not to pump fluid at these temps? I ask because I would like to recirculate during the boil to sanitize the pump prior to chilling.
You can kill two birds with one stone... Wait to start recirculating until flame out, then pump the hot wort through the chiller (with no cooling water running) for ten minutes. It will still be hot enough to sanitize and will drop the wort temp some.

Ed
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Old 04-29-2011, 05:16 PM   #8
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You can kill two birds with one stone... Wait to start recirculating until flame out, then pump the hot wort through the chiller (with no cooling water running) for ten minutes. It will still be hot enough to sanitize and will drop the wort temp some.

Ed
+1 That's the way I do it. The wort temp drops below boiling very quickly after flame out. The pump will be much less prone to cavitation at higher temperatures if you have some net positive suction head, and more is generally better.
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Old 04-29-2011, 06:39 PM   #9
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How do you know if cavitation is occuring? Does the pump head make a loud rough noise?

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Old 04-29-2011, 09:16 PM   #10
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How do you know if cavitation is occuring? Does the pump head make a loud rough noise?
Yes, it will sound like there's gravel rolling around inside the pump head. The pump should be purring smoothly and relatively quietly when all is right. Sometimes with minor cavitation the vapor bubbles get pushed right through the system without causing any problems, but usually you will hear a change in the sound of the pump when that's happening.
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