Help - Need pump Pulseless Flow, 2000 PSI, 100 cc/min

For how long at one time does this pump need to deliver pulseless flow?

There are triplex piston (or plunger) pumps from the likes of Cat Pumps. But for pulseless flow (depends what you mean by pulseless) a hydraulic gear pump might be better, from the likes of Mahr, Haldex, Parker, Eckerle, etc.

I was wondering about that. I don't know, but my first thought was that a spur gear design would be unable to achieve this, but that a helical gear setup could work (if anyone makes it that way).

The likes of Maag do both spur and helical gears (so does the company I work for, but we don't go anywhere near these pressures). Spur gears should be OK, in fact better in some ways as you don't get so much axial loading.

Gear pumps have a quite high degree of non uniformity being spur or helicoidal. OP's problem is to avoid this flow pulsation.

From this point of view the quietest gear pump design is the internal gear as the Eckerle or Voight. The normal gear pumps have 2 gears with 7 to 9 teeth because of smaller dimensions (related to inter-tooth geometry, the smaller the teeth number the bigger the relative inter-teeth volume).

The second major problem is the low flow combined with the high pressure.

The higher will be the pulsation frequency the better it can be filtered by passive means (low pass hydraulic filter) but the low flow imposes very small pumps and usually those are not designed for such high pressures.

To reduce pulsations (which are also noise generators) but for higher flows Bosch designed a special gear pump with 2 sets with a relative angular shift of half a pitch. It decreases the pulsation but a rest remains. Such pumps are developed for industrial hydraulics with powers in the several kW range and not in the 25 W range (100cc/min and 14 N/mm² give a hydraulic net power of 23.3 W)! It follows that for a so small flow the rpm have to be very low and also the pulsation frequency thus very difficult to eliminate it by passive means it can only be compensated by active means. If the pulsation has to be almost nil then only the active solutions as I mentioned could help to reach the wished level.

Yes. This is one reason for considering the Zenith pump. They are small enough that a reasonable RPM can be applied at low flows. There are versions of this pump that can handle the flow and pressure range requested. We used these in a coater solution feed system that was very sensitive to pulsations. Don't have any hard performance numbers on this, but I think the manufacturer can review this application and make a suitable recommendation.

There are different solutions. If cost is a second factor the best approach is a dual piston pump with a double servo displacement (for instance electric servo actuator with speed control). The controller allows a continuous overlapping of the 2 "pumps" so that the resulting flow is constant. The speed in refilling the pump has to be higher so that the cycle can repeat. Considering the flow and the pressure it is the most promising solution. If flow has to be continuous as alternative to the 2 pistons pump an INTERNAL gear pump as the above mentioned Eckerle can be the solution. The rest of pulsation can be eliminated with an active piston with a servo-command which compensates the flow working on the gear pump output. Such systems have been designed and work very well but are not, as far as I know, standard or available of the shelf. Which is the fluid you want to supply? I ask because of the compatibility with the pump and seals. If you need more input please ask.

Suggest you look at a Zenith pump. I used them many years ago in high pressure low flow service.

http://www.zenithpumps.com/product.htm

Which type of pump have used ? They have several types and when I tried the link I did not get any technical doc proposed.

I found a good source for your application but although pulsation is low it is NOT nil since pulsation is an intrinsic property of volumetric pumps. Try following link:

http://www.hnp-mikrosysteme.de/hnp-english/products.htm

One of the pumps goes up to 150 bar pressure which will cover your requirement. The only limitation is that the net flow depends on the fluid viscosity and if this one is too low either you risk not to obtain the wished flow or to have it but with a rather high back leak to tank. The fluid going back will be heated and will increase the tank temperature which can decrease fluid viscosity and lower the flow! The brochure is in English and as far as I know the company German. I may insist once more as long as you will use a pump only and if the pulsation has not a frequency which can be filtered by passive means your flow will NOT be pulsations free. Using, as I mentioned, an active compensator the pulsation can be a lot under 1%. I know those problems because years ago I had to design a hydraulic linear drive for a paint spay hand gun. The problem was not easy since the connecting hose was very stiff so that it did not offer much compliance for pressure damping. We obtained a very good result because the cylinder had a self commuting system working within less 5 ms. You may know that the drop finesse is function of pressure and every pressure drop change at the nozzle generates a change in the drop dimension and a change in the paint density over the painted surface. The eye is extremely sensitive to such variations and it was necessary to maintain the variation very low to avoid quality problems.

Indeed, this is a company from former East Germany. However, their products can also be bought from Micropump (IDEX Health & Science) who market it as their own product:

https://www.idex-hs.com/

I found an other source which could accept a passive pulsations reduction:

http://www.marzocchipompe.com/system/9562/Catalogo_025_ITA_ING.pdf

It is an italian manufacturer - I let Holzfellerthe pleasure to tell you where you can get the product in the Uk or USA-.

Although it is an external gear pump due to the small displacement (0.25 cm^3 or 0.5 cm^3) your flow will be obtained at high rpm so that a passive system could be designed quite easy.

The suggestion to use a triplex pump is not adequate since the flow non-uniformity is quite important. It comes from the fact that flow is proportional to piston speed and between the pistons there is a phase shift of 120°. In the assumption that piston displacement is a sinus function of angle it is possible to compute quite easy the maximal and minimal flows resulting from the sum of the 3 individual flows.

Well spotted, nick name, I don't know why I didn't think of Marzocchi. You see them all over the place, I've seen them in the field on a wide range of applications and I've never heard a bad word said about them. Also not too expensive. They have their own companies in the UK and the USA, as well as distributors. A google search will find them.

standau;

Yes, it is tough; what type of material are you pumping?

There was a dual piston, diaphragm pump sold by Haskel International - but now seems to be discontinued.

You asked months ago, have you found a supplier?

Akron

Yes, I purchased a ISCO dual piston pump with water jacket.

Client has not started it up yet, We are working on a poly melt system for feeding the pump.