Air powered diaphragm pumps

[DaveB]

I received my new pump and am trying to get it working optimally but so far I'm not impressed with the performance. So far I've been mostly moving cold syrup but still. For those using air powered diaphragm pumps, I have a couple of questions:

1. How big of an air compressor do you use? I have a 2.5HP pump that provides 4.7CFM at 90psi and it seems like the pump struggles. I'm not sure if it's the pump or if it's not getting enough air.

2. Do you use an air filter? Someone mentioned adding a filter or something that keeps the membranes conditioned but I wasn't sure about that.

3. Does your pump ever stop pumping? Mine seems to pump but then slow down and speed up without regard to the pressure. Sometimes it just stops pumping and air just exhausts. I'm not sure if that is normal or what.

Are there any other best practices that I should employ? I appreciate any input that folks can give me.

Thanks!

[Russell Lampron]

Dave, for moving cold syrup these pumps are slow. The colder the syrup the harder it is to pump for any pump. I have seen gear pumps struggle under the same circumstances. I put my bulk syrup in my RO room which is 40* or a little higher a couple of days before I plan to pump it and that makes it pump a lot easier than trying to pump syrup that is below freezing.

I use a 3hp contractors compressor and it runs almost non stop when I'm using my pump, even at 1/2 throttle when I'm using it on my filter press.

My pump came with an air filter.

Occasionally my pump will stop pumping but that's only when I trying to get that last bit of syrup through the filter press when the press is getting clogged. When I'm doing that I've got the pump throttled down so that it's not pumping very fast. On my pump I can push on the pump piston to get it moving again.

[Super Sapper]

I would think that your air compressor should work. It may be slower but should still work. The air should not come into contact with the diaphragm, it is used to push a rod back and forth to flex the membrane. I would filter it to make sure your actuator does not get fouled. It should not speed up and slow down unless you have a leak in the suction line. As far as air going through it and not pumping your actuator is stuck between strokes (gummed up). If it is cycling really fast but not pumping you have air in your pump and it is having a hard moving it through due to high discharge head or restricted suction. I would use some oil for air tools and run it through the air line while pumping some water to see if this clears it up.

[maple flats]

My air diaphragm pump does vary in speed too. I can pump cold syrup but it is vary sloooow. I use a heater like this bascousa.com/silicone-rubber-band-heater-4-inch-wide-30-gallon-drum.html
I put it on the drum in the cold sugarhouse 3-12 hrs ahead. I set it for about 100 F. If 12 hrs passes it is fully up to that temp, but at about 3 hrs it is warm enough to pump easily. I usually do the 12 hr setting, put it on the night before and when I get to the sugarhouse in the morning it is ready. I don't very often do the 3 hr time because I prefer doing the work early and waiting the 3 hrs sets me back. However I have used the 3 hr time a few times and pumped it into my finisher to heat it the rest of the way or sometimes, heat it the next morning. I only filter at 205-210 or hotter, never when colder.
I have a 1" hose and suction tube for pulling syrup to the pump. If you plan to pump cold, try a 1.25" or even a 1.5" suction, that will help delivery speed on the suction, even if the actual inlet to the air diaphragm pump is only 3/8" or 1/2". Just make sure the diameter you choose will fit in the barrel bung hole and that the suction hose is stiff enough to not collapse under a partial vacuum.

[wishlist]

I would think that your air compressor should work. It may be slower but should still work. The air should not come into contact with the diaphragm, it is used to push a rod back and forth to flex the membrane. I would filter it to make sure your actuator does not get fouled.

The way a AODD pump works is the compressed air is on the back side of the diaphragm. The valve spool or actuator shifts back and forth and allows compressed air to fill the chamber which “ pushes “ the liquid being pumped out the discharge .

A filter/ moisture trap on your compressed air supply side is a very good idea .

[DaveB]

Thanks for the replies guys. When you're not 100% sure about something I know I can count on getting some direction here. Lots of good suggestions.

The stuck piston diagnosis was a good one. It was just blowing air this morning and I took off the cover for the air intake and rocked the piston back and forth and it worked like a charm after that. I did notice some moisture in there so I will add a filter/moisture trap in the future.

Temps were warmer today with the rain and the syrup pumped much better. I was getting about 0.7 gals/min which is OK with me. I pumped about 120 gallons today in about 3 hours. The pump is rated at 10.5 gallons/min and I'll see what it does with hot syrup and if it comes close to that.

I have an oil heater that I have put next to a drum and placed heavy moving blankets over in the past and it warms up the drums nicely after a few hours. My only problem is that the drums are usually outside and I need to move the syrup inside so I can only do that when the weather is nice.

[GeneralStark]

I acquired a Yamada NDP-15 BAT (Aluminum Body) last spring and it has been working well to pump cold syrup. When shopping for one of these pumps, look for pumps with a 1/2" input/output if you really want to be able to move cold syrup fast. A moisture trap is essential and I have found a regulator to be quite handy to control the speed of the pump. I use if for pumping hot and cold syrup and sweet from the flue pan and having the ability to control the speed of the pump is very helpful. That may also help to clean up some of the start/stop pumping as well.