N/A Impellers are casted in one piece with solid hubs. To minimize thrust loads, the closed impellers are hydraulically balanced by wear rings and balance holes in the impeller hub. The impellers are keyed to the pump shaft and secured by cap screws with Heli-Coil-inserts. The impellers are properly statically and dynamically balanced acc. to DIN ISO 1940T1 Grade 6.3.

N/A Due to high vapor pressures of hot water, standard mechanical seals cannot be used for high temperatures.

N/A Design
The pumps are single stage volute casing pumps in "back-pull-out" design with end suction and top centerline discharge flange. The "back-pull-out" design allows disassembly of the rotating pump parts without removing the volute casing from the piping system.
For fully utilizing the advantage of the "back-pull-out" design, use of spacer-type couplings is highly recommended because the driver can then remain bolted to the base plate.

Volute Casing
Casings with rigid foot mounting are supplied as a standard for the NHL/NHM type.
The casing bolts are of heat resistant expansion type. For applications with temperature swing, additional cup springs avoid leakage, caused by thermal expansion.
Confined gaskets avoid blow-out of the liquid. Centerline mounted design according to API 610/ISO 5199 is available for high operating temperatures on request.
This minimizes thermal stress and misalignment of the coupling due to heat expansion of the casing during operation.
All of the HPL/HPR-pumps will generally be provided with centerline mounted casings.

Wear rings
Volute casing and intermediate casing are both fitted with renewable wear rings held in place by a press fit with locking screws.
Additional impeller wear rings available as an option. The running clearances are in accordance with API 610.

Shaft, shaft sleeve
The pump shaft is able to transmit the full driver output and is accurately machined throughout his entire length and is properly finished at the bearing surfaces.

In order to have satisfactory seal performance the shaft diameter and overhung are sized to minimize shaft deflection at the seal faces.

The shaft design guarantees a critical speed of more than 10% over the maximum operating speed. The connections "cap screw - hub" and "hub - shaft sleeve" are sealed by confined gaskets and the pump shaft has no contact to the pump fluid.

Antifriction bearings
The pump shaft is carried by generously dimensioned antifriction bearings outside the pumped liquid. The bearings are oil-lubricated. The oil level in the bearing bracket is regulated by a constant level oiler.

The standard design has angular ball bearings on the coupling side fixed on the pump shaft in axial direction by circlips. The HPL-pumps and NHL-pumps in temperature swing applications are provided with shaft nuts.

The roller bearings takes the remaining hydraulic radial loads. The bearings proved a life time of more than 25000 operating hours even under severe conditions.

If required, bearing bracket cooling is available, on request.