Best rpm for plunger pumps?

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DetroiTug
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Re: Best rpm for plunger pumps?

Post by DetroiTug » Mon Mar 08, 2021 7:00 pm

The hypro on the tug stopped working, I just disconnected the discharge side where there was no resistance and it flushed a bunch of crap out, reconnected and it worked fine after that.

Ron
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fredrosse
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Re: Best rpm for plunger pumps?

Post by fredrosse » Fri Mar 12, 2021 2:21 am

From Barts:

"On the drawing you note that there's discharge on both upstroke and downstroke. I assume the latter is due to the difference in area above and below the piston?"
ANS: Yes that is correct, with larger discharge volume on the upstroke.

"In your design does the piston have an o-ring seal, or are those water groves?"
ANS: The brass piston does have an O-Ring seal. In the past I have had various connections on this pump, used it as a bilge pump with a fine suction screen, also as a washdown pump when the boat is pulled out of the water, with extra water in the feedwater tank, and residual steam pressure works the main engine and the pumps.
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cyberbadger
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Re: Best rpm for plunger pumps?

Post by cyberbadger » Sat Jun 12, 2021 11:32 pm

What models of hypro piston pumps are you folks using?

When I look at the specifications the max temp is 140F for most of the models I saw.

Also some of these have leather cups, or rubber cups, I assume those don't work?

I'm looking for something to take hot condensate from a tank and pump it into the boiler.

-CB
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barts
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Re: Best rpm for plunger pumps?

Post by barts » Sun Jun 13, 2021 12:05 am

cyberbadger wrote:
Sat Jun 12, 2021 11:32 pm
What models of hypro piston pumps are you folks using?

When I look at the specifications the max temp is 140F for most of the models I saw.

Also some of these have leather cups, or rubber cups, I assume those don't work?

I'm looking for something to take hot condensate from a tank and pump it into the boiler.

-CB
Teflon (CX) or Rubber (RX) work fine in this service; leather likely works as well.

140F is pretty hot - you'll burn yourself if you need to get into the hotwell. I'd keep it at hot tub temps or maybe a bit warmer.

- Bart
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Re: Best rpm for plunger pumps?

Post by cyberbadger » Sun Jun 13, 2021 12:21 am

barts wrote:
Sun Jun 13, 2021 12:05 am
140F is pretty hot - you'll burn yourself if you need to get into the hotwell. I'd keep it at hot tub temps or maybe a bit warmer.
?

The condensate will be the temperature it will be, if the equipment cant handle it then it's the wrong piece of equipment.

-CB
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Re: Best rpm for plunger pumps?

Post by barts » Mon Jun 14, 2021 4:00 am

cyberbadger wrote:
Sun Jun 13, 2021 12:21 am
barts wrote:
Sun Jun 13, 2021 12:05 am
140F is pretty hot - you'll burn yourself if you need to get into the hotwell. I'd keep it at hot tub temps or maybe a bit warmer.
?

The condensate will be the temperature it will be, if the equipment cant handle it then it's the wrong piece of equipment.

-CB
Your feed pump will cavitate if your feed temperature is too high; in that case you'll need to make your condenser larger or use a bigger feed water heater if you still have a significant temperature difference between boiler feed temperature and exhaust temperature.

- Bart
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Bart Smaalders http://smaalders.net/barts Menlo Park, CA
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Lopez Mike
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Re: Best rpm for plunger pumps?

Post by Lopez Mike » Mon Jun 14, 2021 6:47 am

Wish I could get my hot well temps up to hot tub numbers. If I size my condenser for hard running, it is too big for piddling around. I have thought of having two keel condensers in parallel with a valve to block one off when running on a slow bell. Better ideas anyone?

Bart was scarred by having a pine tree near where his boat was stored. And no filter on the pump inlet. I've been running his old Hypro with zero maintenance now for several years.

Along with a filter before the Hypro, probably the only gimmick I might recommend is that I have an outboard motor in-line gas squeeze bulb pump just before the Hypro. It serves more than one purpose. It passes the water though with no pressure drop in normal service. Should I get a slug of air in the pump due to some doltish behavior behavior on my part I can grab the bulb and prime the Hypro. And if there is some blockage in the suction line from the hot well, the rubber bulb gives it away by collapsing.

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Re: Best rpm for plunger pumps?

Post by cyberbadger » Mon Jun 14, 2021 10:46 am

Anybody actually have the model and makeof the hypro pump they are using as a boiler feed pump?

-CB
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Re: Best rpm for plunger pumps?

Post by barts » Mon Jun 14, 2021 3:19 pm

Lopez Mike wrote:
Mon Jun 14, 2021 6:47 am
Wish I could get my hot well temps up to hot tub numbers. If I size my condenser for hard running, it is too big for piddling around. I have thought of having two keel condensers in parallel with a valve to block one off when running on a slow bell. Better ideas anyone?
The only reason to keep the hot well really hot is to reduce dissolved oxygen - hardly an issue for our boats that run at best a couple of hundred hours/year. Our boilers corrode during storage, not operation.

Note that the BTUs available in the exhaust steam by condensing the remaining steam far exceeds the BTUs required to raise the condensate coming out of the condenser, even at local sea temps of 50F, back up to exhaust temperature.... so having both an amply sized condenser and feedwater heater will insure that the plant is at maximum efficiency at both 'piddling around' and hard running.

By the way, my experience has been that the acid test of a condenser is a bollard pull test, or debugging a plant while running hard against the dock lines as there's no flow over the condenser other than that due to the prop wash. On a warm day ( 70F+ water temp) in the CA Delta Otter was burping steam into the hotwell (there is no vacuum pump while I was debugging my air locking pump problems; when running there the hotwell is normally 85F or so.

- Bart
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