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NHL Series

  • Overview
  • Features & Benefits
  • Specifications
  • Other Info

Overview

The Dickow NH/HP Series is a range of hot water circulation pumps. It consists of two basic pump types (NHL, HPL) developed for medium and large size heating applications which require water temperatures > 180°C. The NHL variant is designed for pressures up to 45 bar @ 238 °C with a maximum capacity of 900 m³/h and differential head of 150 m. The HPL/HPR variants are designed for pressures up to 80 bar @ 280 °C with a maximum capacity of 300 m³/h and differential head of 60 m.

The series are single stage, volute casing pumps with a back pull out design, an end suction flange and a centre-line discharge flange.  In order to take full advantage of the back pull-out design, spacer type couplings are recommended so that the motor can remain bolted to the base plate.  The standard pump casing is cast in one piece and foot mounted on the base plate, sealed to the atmosphere by confined non-asbestos gaskets.

Casings with rigid foot mounting are supplied as a standard for the NH types.  HP-pumps are generally provided with centre-line mounted casings.  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.

Closed impellers are standard.  Impellers are cast in one piece with solid hubs.  To minimize the axial load of the bearings, the impellers are fitted with wear rings on the back and balance holes to the suction.  The impellers are keyed to the pump shaft and secured by cap screws with Heli-Coil-inserts.  The replaceable wear rings are held in place by a press fit with locking screws.  Additional impeller wear rings are available as an option.  The running clearances are in accordance with API 610.

The pump shaft is carried by antifriction bearings outside the pumped liquid.  The bearings are oil lubricated with the level 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.  HPL and NHL pumps, designed for temperature swing applications, are provided with shaft nuts.  The calculated service life of bearings is in excess of 25000 hours.

Three designs of water-cooled mechanical seals are available for use with pumps in the NH/HP Series.

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