Page 112: of Maritime Reporter Magazine (November 2017)

TECH TALK

All photos courtesy Blackmer

Bene? ts of Screw Pumps in Shipbuilding Applications

Screw pumps are a practical alternative n the industrialized world, there ids that are handled on ships, tankers may be no more deceptively and barges are transferred at very high named mode of transportation ? ow rates and volumes, which hits the than the “very large crude car- operational sweet spot of centrifugal

Irier,” or VLCC. Calling an oil pumps.

tanker that can be nearly half a kilo- When meeting the operational needs meter in length “very large” is akin to of the centrifugal pump, though, care saying that King Kong is a “pretty big” must be taken to ensure that the pump gorilla or that the Great Wall of China is is operating at or close to a level of ef- “kinda long.” ? ciency that is known as its “Best Ef-

In reality, the VLCC – along with its ? ciency Point,” or BEP. A centrifugal “supertanker” cousin, the “ultra large pump that is able to function between crude carrier” (ULCC) – plays a large 80% and 110% of its BEP is operating role in the transportation of crude oil within a tolerable ef? ciency range.

and re? ned petroleum products around However, when the pump moves too the globe. The capacity of a VLCC can far off its BEP uneven pressure will be range from 160,000 to 320,000 dead applied to the impeller, which can result weight tons (DWT), with ULCCs able in increased radial thrust that causes the to accommodate upwards of 550,000 pump’s shaft to “de? ect.” When this oc-

DWT. While hundreds of VLCCs and curs, higher loads will be placed on the

ULCCs move millions of barrels of bearings and mechanical seal, which crude oil at a time, a ? eet of product can lead to damage to the pump’s cas- tankers, with capacities of up to 60,000 ing, back plate and impeller. There-

DWT, stand ready to transport the petro- fore, ensuring that the pump is working leum, petrochemicals and other re? ned within an acceptable BEP range can be a products to other pivotal points along can offer a versatile, reliable and ef? - The Challenge time-intensive task since the pump must the production and supply chain. cient alternative to centrifugal pumps in The most obvious challenge – and be monitored constantly and adjusted as

Traditionally, centrifugal pumps have the critical loading/unloading and trans- perhaps the toughest to eliminate – is needed, which costs time and money.

been a go-to technology that shipbuild- fer operations on the vessels that carry positioning the screw pumps an accept- There are other considerations that ers have used for various ? uid-transfer crude oil and ? nished petroleum-based ed solution for shipbuilders, a group that shipbuilder must contemplate before applications. However, positive dis- products for the long-haul shipping in- have long relied on centrifugal pumps. deciding on the best pump technology, placement twin- and triple-screw pumps dustry. Generally speaking, the bulk of the ? u- including: 112 Maritime Reporter & Engineering News • NOVEMBER 2017

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