In general, submersible pump motors are not as efficient as their surface-mounted counterparts because their rotor rotates in fluid, which has more friction than air. Indeed the motor on a submersible pump can be something of an Achilles heel as it can be damaged by sand if it finds its way inside, and it can over heat if not enough pressure is available to force the water into it. This enables semi-submersible pumps to be driven by a much wider range of motors, diesel engines, hydraulic motors or HV motors. Their motors are accessible and positioned in the rig which means they can be monitored and changed with relative ease. However, despite all of the advantages that submersible pumps have over their semi-submersible relatives, vertical line shaft pumps may not be completely dead in the water as there are several situations where they are still the better, if not the only choice. Additionally, submersible pumps are quieter, as the motors are in the water and usually have narrower diameters than vertical line shaft pumps, a factor which can be of benefit in some retrofit and decommissioning situations. For instance, Aturia can go down to 10 m3/hr and achieve differential heads of up to 700 m. This makes their use in platform caissons feasible and thereby gives them a whole range of low flow high head duties not open to vertical line shaft pumps. The construction of a vertical submersible pump also means that radial flow submersible pumps do not need a separate discharge pipe as is required by a semi-submersible pump. All of this makes the risk, initial cost and maintenance commitment of a vertical line shaft pump much higher than that of a submersible. With caisson delivery columns typically in excess of 40 meters, this is an important factor because such shafts not only require significant maintenance, but increase the complexity of the installation process and require guides in the caisson to ensure a perfectly straight alignment. This move towards submersible pumps has been for one very good reason submersibles do not contain a rotating column shaft along with all of its associated bearings as the delivery column with a submersible pump is nothing more than that, a pipe with no moving parts. However, in spite of this sterling service over the half a century, the preference when it comes to seawater lift pumps has shifted towards fully submersible pumps. With a such a well proven design and the correct materials, they can last for decades and it's not unusual for AxFlow to see vertical line shaft pumps in our repair facility that are well over 30 years old. Their design is simple, with the motor positioned above the pump turning the pump impellers via a vertical rotating shaft that passes down the discharge column into the pump chamber. So, in the 1950s and 60s, when offshore platforms were first constructed they represented the only real choice for the seawater lift pumps. Essentially their designs haven't changed since then, although their applications have widened over the years to include docks, mines and power generation. For example, AxFlow's partners Gruppo Aturia have been producing them since the 1890's when they were employed to pull water out of wells for agriculture and drinking supplies. Semi-submersible vertical line shaft pumps are one of the oldest types of pump design. These pumps come in two varieties: semi-submersible vertical line shaft pumps with the motor located above the pump assembly, and fully submersible pumps with the motor positioned below the pump in the sea. The most popular route for this water to get onto the platform is via vertical caissons into which narrow column pumps are inserted. Certain models are also fitted with bronze upper cover, bearing bracket and mechanical seal bracket adding to corrosion resistance.Ĭommon applications for this sump pump include water supply and drainage for large flow rate aquaculture applications, brine, flood control, extracting water from docks, power plant cooling, irrigation, high flow rate dewatering, water features, horticulture irrigation and extracting water from lakes, rivers and reservoirs.Due to its proximity it's not surprising that seawater is used widely on offshore platforms as cooling water, for reinjection into the well, and as a firewater supply. All models within this range are manufactured with an aluminium bronze impeller, epoxy coated and supplied with sacrificial anodes making them excellent for use in sea water and marine applications. The largest model within this range is capable of achieving flow rates up to 480m³/hr and heads up to 7m. The HCP L range of submersible pumps are designed for applications requiring high flow rates. HCP L Series High Flow Rate Submersible pump
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |