It will depend somewhat on the application. You may want to look at some of the Gardner Denver products. They have well service pumps.

http://www.gardnerdenverproducts.com/microsite_product.aspx?id=3004

Your service is in a gray area that either a centrifugal or a positive displacement pump could handle. Which one would be better suited would require some more info on your service/system.

Is the water clean? Any abrasives? Corrosives?

Describe the dishcharge side of your system. What are you pumping into?

Is service intermittent?
Any specifications you must adhere to?

The application is to drive a high-pressure atomizer array.  The service is continuous.  You can assume the water is river water that has been passed through a sand-filter to remove the leaves, crawdads and silt.  There may be a few granules of sand and an occasional fleck of scale from the pipes, but not much.  This is for a plant location, not laboratory, so pump needs to be reliable and robust.  There are no outside engineering specifications.

Gardner Denver as proposed by bimr is a good advice unless you are in a country where they have no presence.

Make sure that the stroke nos. complies with API 674 and that they have a plunger seal with water flushing or grease lubrication and that their proposal is complete (incl. all necessary accessories). Some plunger pump manufacturers like to add some good and important accessories later to let their first bid look more attractivce.

This service could be satisfied by a centrifugal.  Either Sundyne or Roto-Jet could meet these conditions in a single stage machine.  However, for the Roto-Jet, you would need to be sure that there were no heavy solids (sand).  The Sundyne would also have problems with solids, but would be less sensitive than the Roto-Jet.  We also use a Sulzer stacked diffuser multi-stage pump is a service very similar to this (95 gpm at 1000 psi).  It has worked well and it is more efficient than either the Sundyne or Roto-Jet.  If I was building a new unit today, I would definitely not choose Sundyne. I would evaluate the Sulzer or Roto-Jet options based on suction conditions, efficiency and up-front cost.  

We have used positive displacement (piston) pumps for services such as this.  All of them have been removed because of poor reliability.  But, our services run 24/7 for at least two years at a time.

Johnny Pellin

Thank You!

Have a look at these pumps. We also have pumps acc. to API674, but the outlet pressure depends on the media and operating conditions.

http://www.danfoss.com/BusinessAreas/High-Pressure+Systems/Products/Pumps  

• http://www.danfoss.com/BusinessAreas/High-Pressure+Systems/Products/Pumps

We have had good luck with the roto-jets.  Especially in water service.  I prefer them over the sundyne's due to simplicity.