Below is a letter from a customer on proper seawater desal application of this pump:
The pump is working very well! •ll tell this also those people whom I know and who might be interested in upgrading their watermakers.
Mine is powerd from a 2200 Watt pure Sine inverter (12VDC -> 230VAC, which is the European household current, similar to your 115VAC), by an 1800 Watt (2.5 hp) 3-phase AC-motor. The inverter of course supplies 230VAC at 1-phase. The AC motor is controlled by a Hitachi frequency inverter (make 3-phases out of 1 and allows to control the 3-phase-AC-motor from 0 to 3600 rpm continuously, look here http://www.hitachi-america.us/products/business/inverters/ There are other brands as well, I•m sure. Here at least the Hitachis were the cheapest ones).
There is no other way to control rpm on those industrial motors (so called •universal motors• as in vacuum cleaners are easy to control however almost impossible to get in proper housings, as I found out). Anyway, probably you know all that.
I wanted to control rpms on the pump motor in order to control current draw during the starting sequence and also during the watermaker working. I don•t have a genset aboard, so everything basically runs off the alternator, the solar panels, and the domestic battery banks.
I also use a Jabsco ParMax 4 pump (4.3 gpm) as a booster pump.
I run the 0.8 Danfoss pump at approx. 2500 rpm and at approx 60 bar (870 psi).
When I go up to the allowed 3600 rpm water flow becomes incredible high, but also the amp draw goes up to 150 Amps, which is • at least in my setup • not acceptable. I stay around 100 Amp (which is the nominal rating of my alternator. Thus, when the engine is running I am around 0 Amp to minus 40 Amps from the battery banks, depending on the actual alternator rating, which goes down when it becomes hot).
Here a 2.5hp 3-phase AC motor is about $100, the Hitachi frequency inverter is about $200, the bell housing to flange the pump onto the motor is about $30, the flexible coupling is another $20. If there is a DC->AC inverter aboard the AC version seems to be cheaper and more reliable than a 12V-setup (no brushes, standard industrial components).
With one SW30 2540 Filmtec membrane and the local (Mediterranean/Adriatic) water conditions (salinity of 3.6 percent, which is one of the highest worldwide, and 20•C / 68•F) the watermaker produces some 18 gph fresh water @ 2500 rpm and goes up to 28 gph at •full speed• / 3600 rpm.
These are my experiences, dated from April this year, when I first went to sea with the new Danfoss 0.8 pump (which obviously is optimized to a 2540 membrane, in terms of flow capacity).
APP pumps are designed to supply low viscosity and corrosive fluids under high pressure, eg in seawater reverse osmosis filtration applications and for high-pressure salt water pumping.
The pumps are based on the axial piston principle enabling a very light and compact design. The design ensures that lubrication of the moving parts in the pumps is provided by the fluid itself. No oil lubrication is thus required.
All parts included in the pumps are designed to provide long service life, ie long service life with a constantly high efficiency and minimum of service required.
The pumps are fixed displacement pumps in which the flow is proportional to the number of revolutions of the input shaft and the pump displacement, regardless of any counter-pressure.