Exploration • Drilling • Field Services
Submersible motor pumps for offshore applications
Submersible motor pumps provide an effective means of lifting seawater for duties including cooling, fire-fighting, temporary ballast and emergency drain pumps.
Las bombas de motor submarino proporcionan un medio efectivo de elevación del agua del mar para las labores de enfriamiento, extinción de incendios, lastrado temporal y bombas de drenaje de emergencia.
Motortauchpumpen sind eine effiziente Lösung zur Meerwasserförderung zur Kühlung, Brandbekämpfung, als behelfsmäßiger Ballast usw. Sie sind auch als Notlenzpumpen einsetzbar.
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ubmersible motor pumps have become an indispensable feature of the offshore industry in recent years, largely due to the combination of technical
sophistication and cost-effectiveness. Providing maintenance-free operation
over extended periods, the pump is a conventional multi-stage centrifugal type in a ring-section or vulture design that allows the pumphead and output to be matched to the application by varying the number of centrifugal stages as required. Te pump is driven by a submersible motor which is directly flanged below the pump (Fig. 1). By virtue of its design and underwater application, the pump is suspended below the platform or vessel either in the sea or in a stilling tube, so in terms of space allocation all the installation needs is a simple head plate. Te power supply and functional monitoring is via electric cables and water delivery through a simple vertical discharge column. Typically these pumps operate at 20- 30m below sea level, but the maximum
operating depth needed is 5-15m below the LAT (Lowest Atmospheric Tide) and flows up to and beyond 2,000m³/h. In the Middle East where the sea levels are much shallower and flat, depths below 8m are rarely encountered so it is necessary to ensure that the water level is always above the pump. Submersible does not just mean that the whole motor operates in water: the inside motor space, i.e. the space between the rotor and stator, including the windings, is also filled with potable water. Tese water-filled motors do not require any form of lubricant as the bearings are lubricated by the water. In addition, the water constitutes an effective cooling medium for the motor. Te most important advantage of water- filled motors is that they can withstand any pressure as the internal and external pressures are always kept in balance. Tis means that the submersible motor pump can be installed at any depth irrespective of the prevailing pressures. Te design of the submersible centrifugal pump, whereby the pump and water-filled motor constitute a compact unit with the motor located below the multi-stage pump, is a mixed flow type consisting of a suction stage, bowls and a discharge casing. Te suction casing connects the stationary parts of the pump and motor, and is fitted with a suction strainer to protect the pump against the ingress of larger sized solids. Te pump shaft is connected to the motor by a rigid coupling, with the shaft being protected by sleeves and transmission of the motor torque to the impellers performed via shaft keys.
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www.engineerlive.com Fig. 1. KSB’s UPA 350 14-inch submersible pumps.
Seawater motors All the parts of submersible motor pumps that may come into contact with seawater are manufactured from materials that are resistant to seawater (Fig. 2). Te three-phase asynchronous motors are
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