Descaling Pumps with single flow impeller

Descaling Pumps with Single Flow Impeller Arrangement:

This pump design is horizontal multistage ring-section with single flow impeller arrangement (with all impellers facing the same way) and automatic compensation of rotor axial thrust by a balancing device. These pumps are designed to meet the stringent duty requirements of descaling of slabs in plate mills and hot strip mills. There are frequent changes from design flow to minimum flow during descaling operation that put huge thrust loads on the balancing disc and shaft. We have supplied more than 20 descaling pumps in 8 steel plants world over. The oldest is running since more than 20 years.

Construction Features

The pump casing consists of a suction casing; a discharge casing and a set of stage casings, which are concentrically aligned with respect to each other, being fitted on circular rabbeted fits, and tied up with studs (tie bolts). The tightness of joints between the stage casings, suction and delivery casings is ensured by a metal-to-metal contact of the mated surfaces, with round section joint rings (O-rings) of rubber placed in between them for additional sealing.

Renewable casing wear rings and inter stage bushes are fitted respectively in the suction casing and stage casings and in the diffusers in order to reduce internal leakage from the high (discharge) pressure area to the suction pressure side. They together with the sealing surfaces of the impellers form throttling gaps (impeller sealing or running clearances).

The suction and discharge nozzles are oriented vertically to the top.

The pump rotor is composed of shaft, impellers, balance disc, sleeves, oil throwers and fasteners.

Axial forces arising during the pump operation act on the impeller shrouds and shaft end face. They are directed towards the pump suction.

Balancing device incorporating a balance disc with balance disc seat and recirculation of balance liquid stream to the suction serves to absorb the axial thrust of the pump rotor. The extent of compensation of the rotor axial thrust varies automatically as the operating conditions of the pump change.

A thrust antifriction bearing and an automatic shaft position indicator are provided in the non-drive end bearing for the limitation of axial shifts of the rotor.

Balance disc and balance disc seat are assembled units, each of them consist of basic part and executive elements – wear rings, manufactured from special wear resistance W carbide alloy. Such design ensures long service term of balancing device and allows carrying out easy repair works when necessary.

Technical Parameters

NosPump makeCapacity, m3/hHead, mRotational speed (synchr.),rpmMotor nominal power, kW
1CNS 90-1900100200030001250
2CN 280-1180284118036001250
3CNS 300-1800360170036003150
4CNS 360-2000250237030002500
5PE 270-150-4250185030002000