Neptune NXP-M Operating Instructions Manual page 23

Stepper motor-driven diaphragm dosing pump NXP-M and NXP-P
8.7.8 Dosing of suspensions
When dosing suspensions, the dosing head must be rinsed regularly to
prevent depositing. To do this, you install a feed line for the rinsing
medium (water) in the suction side installation.
8.7.9 Suction pressure regulator
A suction pressure regulator may be necessary if the suction-side
installation of the system demonstrates a varying suction pressure or
supply pressure:
Dosing pumps that are installed above dosing tanks deliver less as the
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tank empties, since the suction head increases.
Dosing pumps that are installed below dosing tanks deliver less as the
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tank empties, since the positive delivery pressure reduces.
Further problems that can occur:
Greater wear on the dosing pump, e.g. diaphragm rupture due to the
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effects of heavy forces with particularly high tanks and high-density
dosing media.
Idling of the dosing tank in the case of a diaphragm rupture or pipe
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breakage.
Impermissibly high forces in the pump transmission that occur when
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dosing pumps receive the dosing medium directly from the pressure
line.
Reduced performance or destruction of fittings due to cavitation with
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long suction lines.
Installing a suction pressure regulator is a remedy for the problems
above. The suction pressure regulator is opened by the dosing pump's
suction pressure. This ensures that no dosing medium can flow if the
dosing pump is not running or no vacuum can be generated following a
pipe fracture.
Notes on assembly:
When using a large suction pressure regulator, you should provide a
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pulsation dampener on the suction side.
Subject to technical changes.
Operating instructions
Hydraulic installations
23
Hydraulic accessories