High pressure low volume water pump

[DDM]

Hey all, I'm looking at doing a water jet/ abrasive jet machine for use on wood and I'm having problems finding pumps that are in the hobby price range. I wouldn't mind building some parts due to the fact that I work in a machine shop but just trying to some basic plans to work off of would be a start. I've thought of using a radial piston pump for hydraulics but there's lubrication (don't know if water would be enough) and then there is how much pressure I could actually get out of it. Piston pump systems typically run around 3000 psi to my knowledge and I'm looking probably closer to 10k psi. I think this would be a great open source project and I'd be willing to try and make some head way but I need somewhere to start from. Any help would be greatly appreciated.

Carl

[trubleshtr]

Hi Carl, 10,000 PSI is pretty steep! You'll probably want t stick with either the piston pump or possibly a rotary screw style. To simplify, perhapps you could modify a a rotary screw system (used) from an old industrial compressor or a mazda RX7 , and put it together A'LA junk yard wars style???? Or an old v-8 engine driven buy an electric motor to get things mov'n?.....

[DDM]

Yeah I know it seems kinda steep but what to the professional water jets run at, isn't it like 30,000 or more PSI at less than a gallon a minute. I was looking through my Industrial Hydraulics manual last night and found some of the equations that should apply for a waterjet system. I figured a two horse power moter running a system at 10,000 psi could flow about a quarter gallon a minute.

Kind of a side note, how does a booster pump work, I know it creates more pressure but at the same time looses volume. I'm not really worried about the volume because it's the high velocity of the water that would erode the wood away. So what if a person was able to use a electric pressure sprayer and put a booster pump on it.

I've thought of using something from another industry as a pump but the piston in my mind would have to be rather small to create that much pressure. And it would take one hell of an electric motor to push a V8 pump. And as far as the RX7 I'd be driving that one

Carl

[balsaman]

Piston pumps don't last long pumping water. Don't ask me how I know this.

You might be able to do a hyd pump pumping oil and use a oil over water intensifier (oil in a big dia cylinder pushing on a small dia cylinder with the water in it. When it stroked out you would need to pause while the cylinders retracted and then start again. You get pressure intensification based on the ratio of large dia cylinder area to the small dia cylinder area.

I am afraid there is no DIY (read cheap) way to make 10,000 psi

Also you need some serious (expensive) filtration to keep the nozzle from plugging up

Eric

[HuFlungDung]

I've conjectured that the way I would attempt this is to use several gear pumps in series. Each pump should be capable of increasing the pressure of its outlet over its inlet by 2000 or 3000 psi.

The technical difficulties of this I am not sure about. For sure, the pump housings handling the latter stages must be extra robust to keep from simply bursting. Water is also quite low viscosity to try to pump with a gear pump, maybe another type would be better. But a piston pump would suffer extremely heavy piston ring loads on such an application and would wear out, or simply break out the ring lands in no time at all.

Extra precautions should be taken in the form of heavy steel lines, and heavy shielding in case something under high pressure springs a leak. You don't want to be cut in half with it

[DDM]

HuFlungDung you've read my mind, I was thinking about doing several pumps in series with each consecuative pump building just that much more pressure. I've also thought of using two hydraulic rams pushing two small pistons and valved right so that with the return of one the other is pushing in so that you can retain a constant pressure, I think that's kinda how the big boys do it. I could really tell from the pictures on one of the websites but it looked like it.

The other think I've thought about is lubrication. At work the head guy is trying to market this polymer that is added to water that has some great properties from lubrication, to anti-misting, to settling sediments in water. The stuff feels like... well astroglide when you rub it between your fingers so I might have to keep that in mind. The stuff goes into water as a powder and it's enviromentally safe. If anyone is interested in the stuff let me know and I can more than likely get you the info.

Well I'm going to check out some gear and vane pumps tonight and let you all know what I find out.

Carl

[DDM]

well I checked northern Hydraulics and they've got some gear pumps in there that working pressure is 3000 psi at .5 gpm, from that the motor required to run it would be just over 7/8 hp, so pickup some 1hp motors or a single 3hp and run 3 of those gear pumps in series. So For motors and pump there would be about 600 bucks unless you can get something off of ebay. You'd probably want to put in a second circuit (running about 30 amps of current) but I'm not an electrician. Then there are the check valves, which I would want one inbetween each of the pumps and they are only rated at 3000 psi. That's just off of northern hydraulics, I'm going to do some more checking around and see what I can find.

I do realize that this project is not for the weak of heart because this kind of setup could be very dangerous. The third pump at 9000 psi is going to be under a lot of pressure from the inside out and could have chance of exploding. Never under estimate the power of hydraulics. Thats kind of my disclaimer if anyone else is looking at doing something of this sort.

If I'm off on my thinking somewhere please let me know, or if I'm completely nuts.

Carl

[DDM]

Hey just an off idea before I went to bed... Does anyone know the specs on the pressure and flow of a diesel injection pump? Just an idea.

Carl

[HuFlungDung]

I used to watch my Dad test diesel injectors. If memory serves me right, the injectors opened at about 3500 psi. I suppose the pump had a bit more reserve than that. These pumps have strict requirements for cleanliness and lubrication (from the fuel), of course.

[trubleshtr]

Check out Hammelman. We use a 4000 psi piston pump stlye unit with 2.5mm orfices for cleaning/deburing aluminum castings, this set-up actually causes porosity issues if we don't protect the aluminum areas we don't want blasted. You might get ideas on how they creat high pressure systems?

Also don't forget some kinda of unloading valve in your design so you don't trap any high pressures betweeen lines/pumps and valves.
Vane pumps are non-positive displacement and will "slip" under load, they are more for high flow. low pressure apps.
You need a positive displacement pump to create these high pressures
I like the idea of air over oil if you put several in series it's "like" a big piston/crank set-up in a vehicle
.

[DDM]

Yeah the whole diesel injector pump was just an idea, I'm pretty sure they are piston pumps and with the water lubrication would be kinda tricky. I'm thinking that small gear pumps would be the best course of action, simple and it takes quite a bit to tear them up. I need to get over and talk to my old boss (used to work at place that manufactured hydraulic pumps) and see what he has to say.

trubleshtr - I think we are looking at different kinds of vane pumps. There is the turbine type which I think you are thinking of which is used in most general applications of moving liquid and is good more or less to 60 psi. I was talking about the Vickers style pump for hydraulic systems which is good around the 2000 psi range. They have a mulit cam/lobe setup and pilot pressure pushes the vanes to the wall causing the fluid to stay in one particular chamber making the greater pressure. I'll try and get a link if I can find one.

If anyone else has any ideas I'd be happy to hear them and long as it doesn't involve me loosing any fingers or other important body parts.

Carl

[trubleshtr]

Ops For some reason I was thinking Impeller pumps not vane. My mistake.