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General
The Dickow HZS/HZSA pumps are designed with volatile liquids in mind.  These multi-stage centrifugal mechanically sealed pumps have one side channel impeller that allows for the handling of entrained vapors reducing the likelihood of vapor lock.   The HZS top-suction top-discharge design offers self-priming capabilities once the pump is initially primed.  This design makes the pump ideal for tanker truck, rail car, or underground tank unloading applications, since the HZS can purge the suction line of air and vapor.  The HZS/HZSA pumps can offer flows up to 600 m3/hr (2,460 gpm) and differential heads up to 500 m (1,640 ft).  The  maximum operating temperature is 100 °C (212 °F) and the maximum operating pressure is 16 bar (232 psi).

Unit of Measure

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Construction
HZ/HZA-pumps are multistage centrifugal pumps of radially split casing design.

Suction- and discharge casing
Suction- and discharge casings are provided with sturdy cast feet for mounting on baseplates or base frames. To obtain low NPSH-values, the suction casings of the HZ-pumps are designed volute shape.
HZA-pumps have end suction design to obtain lowest NPSH-values.

Impellers
The closed impellers are hydraulically balanced by wear ring gaps and balance holes, the antifriction bearings are carrying only minor loads and further balancing devices are not necessary. For lowest NPSH-values, the impeller of the first stage is designed as a suction impeller with enlarged impeller eye.

Bearing
The HZ-pump shaft is carried by generously dimensioned grease-lubricated double-row angular ball bearings and a roller bearing, located outside the pumped liquid. These bearings can be regreased through grease nipples, provided in the bearing casing.
The HZA-pumps are provided with a Silicon Carbide sleeve bearing on the suction side which is - to avoid dry running - connected to the discharge side.

Wear rings
Suction- and discharge casings, intermediate casings and diffusers are generally equipped with interchangeable wear rings. If requested, the pumps can also be equipped with impeller- and casing-wear rings.

Intermediate casings / Diffusers
The impellers are centered inside of the diffusers. The diffusers are of multiflow channel design converting part of the generated velocity from the impeller into pressure. The guide vanes on the rear side of the diffusers lead the pumped liquid to the impeller of the following stage.

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Materials
Standard materials for HZ/HZA-pumps as follows: (special materials available on request)

Suction- and discharge casing: Ductile iron GGG40. 3 1.4408(G-X5CrNiMo18.10) Cast steel GS-C 25
Intermediate casing Ductile iron: GGG40.3 1. 4408 (G-X5CrNiMo 18.10) Cast steel GS-C 25
Impellers and diffusers: Cast iron GG 25 1. 4408 (G-X5CrNiMo 18.10)
Pump shaft: 1.4021 (X20CM3) 1.4571 (X10CrNiMoTi18.10)
Seal casing: Ductile iron GGG 40.3 1.4408 (G-X5 CrNiMo 18.10)

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NPSH-Values
When handling hydrocarbons, condensates and other volatile liquids, it can happen that the pump fluid flashes in the impeller inlet of the first stage and interrupts or influences the flow.
However, the lower the NPSH-value of the pump, the smaller will be this risk. Due to the hydraulic design of the suction casing and the impellers as described before, the following NPSH-values can be obtained.

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Shaft sealing systems
Besides the before mentioned shaft sealings through metal bellows mechanical seals, system DICKOW N6, the following shaft sealings can be applied, depending on the pumped liquid and customer's specification.