HZA Multi-Stage Centrifugal Pump, Centrifugal Pumps Type HZ/HZA
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).

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.

Sealless Pumps 

Why Sealless?
Why Use Dickow Magnet Drive Pumps?
Since the 1970s concern for the environment has become increasingly important in the design of industrial plants. Today this issue is a vital concern in any discussion involving new plants and updating of facilities. Equipment designers, engineers, and suppliers must offer solutions which will eliminate any adverse environmental impact, or at a minimum reduce it to sustainable or regulated levels.

The weakest link with respect to centrifugal pumps is the shaft seal, when considering release of fluids to the environment. This is because there is always some inherent emissions from mechanical seals. The average emission rate of a mechanical seal is 0.13 GPM to 0.35 GPM, and although this appears to be quite small, the actual atmospheric penetration is quite large when one considers that large chemical plants have thousands of pumps in operation. In 1989 the Environmental Protection Agency (EPA) published its first report on environmental pollution. The report documents that American chemical and petrochemical industries, in 1987, emitted 390 tons of toxic materials into the atmosphere, in part attributable to pump leakage.

Potential problems occur by the formation of dangerous explosive mixtures, which become worse when toxic or malodorous gasses and vapors endanger plant personnel. In order to prevent the vaporization of liquids between seal faces additional cooling is required when the media has vapor pressure greater than atmospheric pressure at operating temperatures. Additionally, when handling fluids that crystallize in the atmosphere, an appropriate quench connection or barrier fluid must be provided.

Various attempts have been made to improve the performance of mechanical seals in order to meet regulations pertaining to emissions. Examples include double acting mechanical seals of "tandem design", "back-to-back design", and various gas seal types. All of these require auxiliary equipment, systems, and controls. For many applications the costs of this equipment is not justifiable in light of the gains attained.

It would appear that the outer limits have been reached for improvements in mechanical seals with regard to reliability and emissions control. The only realistic solution is a sealless pump with zero leakage, i.e. without the connection of the media to the environment due to the absence of a seal. Many of our earliest customers installed Dickow sealless magnet drive pumps for their zero leakage feature, but quickly realized that their mean times between failures was greatly improved as down time due to seal replacement was eliminated completely.

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Dickow Pump Company has produced pumps for over 100 years. Our pumps are working steadily and dependably in all corners of the globe.

As the technical world leader in magnetic drive pumps, Dickow holds many patents, is ISO 9001 certified, and is a supplier-partner of major chemical companies.