Parker Hydraulic Group
NSH20 Series Pressure-Sensitive Unloading Gear Pumps

Key Features

  • Flows to 98 GPM per section
  • Tandem & triple section units available
  • Pressures to 2500 PSI
  • Speeds to 2500 RPM
  • Pressure & flow sensing valves available
  • Dry valve option
  • Piggy back option available
  • Also available as motor
  • Cast iron versions available
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Tandem Pump with Pressure-Sensitive Unloading Valve

The NSH pump system uses an unloading valve to divert the flow from one section of a tandem pump. The system is designed to limit the hydraulic horsepower, and thus limit the horsepower taken from the prime mover. Flow is supplied from both pumping sections at low, working pressure and from only the front pumping section at high pressure. As the system pressure increases to a predetermined value, a pilot relief valve opens, causing the main spool to divert the rear pumping section to the common inlet port, while the front pumping section continues to supply fluid to the system.

When the system pressure decreases to the predetermined value for which it was set, the relief valve closes, causing the main spool to divert the unloaded flow of the rear pumping section back into the system. The rear section can be manually unloaded at any time, regardless of system pressure, by venting the manual unload pilot port.

Description ............... Pressure-Sensitive Unloading Gear Pumps
Combined Flow Range ........To 98 GPM Per Section (370.9 LTR)
Displacements ... To 9.10 C.I.R. Each Section (149.12 CC’s/REV.)
Maximum Pressure to ...................................... 2500 PSI (172 BAR)
Maximum Speed to ........................................................... 2500 RPM
Rotation ......................................................................................A or C
Bearings ................................................................................... Journal
Construction .......................................................................Aluminum