Marflex Brochure Deepwell Pumps_lr2013

Deckarrangement

Pipe stack

Pumphead

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The MarFlex Deepwell Pump

As the new MarFlex deepwell pump needed to be driven by an electric motor, we first had to develop a ‘non-cargo-lubricated’ driveshaft. This resulted in a unique ‘oil-lubricated’ shaft running in a separate supporting pipe.

The service life of an oil-lubricated shaft arrangement is more than 10,000 operating hours, based on the service life of the bearings in the electric motor.These 10,000 operating hours are normally sufficient to last the service life (20-25 years) of a sea-going vessel.

To explain the MarFlex deepwell pump in detail, we will divide the total pump into three sections:• Deckarrangement• Pipestack• Pumphead

Deepwell pumps with a so-called ‘cargo-lubricated’ driveshaft for chemical and product tankershadalreadybeenproducedformanyyearsbyvariouswell-knownpumpmanufacturers. The operational disadvantages of this design, however, are very familiar in the shipping industry.

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050 100 200 400 800 1600 3200

MDPD-80

MDPD-100

MDPD-150

MDPC-200

MDPC-250

MDPC-300

MDPC-300 OS

MBDPC-150

MBDPC-200

MBDPC-300

MBDPC-400

MBDPC-500

Pump performance curves

Capacity (m3/h)

Hea

d (m

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Deckarrangement

Advantages of electric-drive deepwell pumps compared with hydraulic-drive deepwell or submerged pumps:• Totalsystemefficiencyapproximately20%higher;• Lownoiselevel;• Easytoinstall,thankstotheelectricalwiring instead of a complicated hydraulic piping system (commissioningisreducedtoarealminimum);• SimpleandrobustACmotor;• Cleansystem(nohydraulicoilleakages);• Lessmaintenance.

The speed of the electric-drive MarFlex deepwell pumps can be controlled in several ways:

One-speed electric motorSuitablefortankersthatcarryproductswithasmallspecific gravity range, such as the so-called ‘product tankers’.

Variable speed control by means of the electric shaft principleThis is mostly used for inland barges. The variable speed generator set that drives the bow thruster also drives the pumps during offloading.

Variable speed control by means of a frequency converterA frequency converter system has the following advantages:

1. Power• Highefficiency;• Energyconsumptionaccordingtoactualneed;• E-motorsandconsequentlygeneratorsdonot need to be over-dimensioned for products with a highviscosityand/orspecificgravity;• Softstart(noinrushpeaks):lessfrequentstart-up of generators.

2. ControlIndependentcontrolofeachdeepwellpump;• Accurate,variablecontrol;• Lowmechanicalwear;• Lowcavitation;• Programmableforspecificpumpingrequirements: -minimumdischargingtime; -minimumcavitation; -liquidlevel; -specificgravity;•Connectiontocargomonitoringormachinery automation system.

The MarFlex deepwell pump can be driven by an explosion-proof, class-approved electric motor or a hydraulic motor.However,99%ofallthedeepwellpumpsinstalledbyMarFlexsincetheintroductionofthenewdesignin1987 are electrically driven, for the following reasons:

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Pipestack

The separation of the shaft from the cargo gives the following obvious advantages:•Theintermediatedriveshaftismadeof42CrMo4V,

which is a heat treatable steel. If the shaft were exposed to the cargo, it would be necessary to use AISI 316L steel, which is not the ideal material for a deepwell pump driveshaft.

•Becausetheshaftisoil-lubricated,thepumpbearingsneverruns‘dry’duringstrippingandtankcleaning operations.

- No danger of explosion as a result of overheating of intermediate shaft bearings. - Longer service life of the shaft bearings (approx. 10,000 operating hours). •Becausetheintermediateshaftandbearingsare

oil-lubricated, the pump can run at relatively high speeds. This results in a single stage deepwell pump.

The shaft bearings of the MarFlex deepwell pump aremadeofRailko®,heldwithinaViton®orKalrez®flexible member.

Advantages of the MarFlex intermediate shaft design:•Noshaft-alignmentproblems;•Fixedcouplingbetweentheshaftofthedrivemotorondeckandtheintermediatedriveshaft;

•Becausetheintermediateshaftbearingsareoil-lubricated, they have a long service life.

Thelengthofthepipestackhasnorestrictions.However,anintermediateshaftsupportisfittedat 6-metre intervals (see drawing on page 8). This supportconsistsofaballbearing,whichtakesonlythe axial load of each shaft length of 6 metres.Axialthrust/loadfromtheimpelleristakenonlyby the pump shaft bearings and is not transmitted totheintermediateshaft(bearings),thankstothe‘spline’ connection between the pump shaft and the intermediate shaft.

The design of the MarFlex deepwell pump is based on a driveshaft that is separated from the cargo. Thepumpstackconsistsoftwopipes:oneisthedischargepipeandtheotheristheenclosureforthe intermediate driveshaft, the shaft bearings and the lubricating oil.

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PumpheadThe MarFlex deepwell pump is designed in such a way that the total pump head can bedisconnectedfromthepipestack,whichmakesmaintenanceveryeasy.

A so-called ‘spline’ connection between the intermediate driveshaft and the pump shaft in the pumpheadmakesitpossibletodisconnectthepumpheadfromthepipestackbyloweringthepumphead.

1. The pump shaftThisshaftismadeof32CrNiMo6Vsteel,averyhighgrade steel that is ideal for this purpose.Liketheintermediatedriveshaft,thepumpshaftisnot made of AISI 316L because it is oil-lubricated rather than being exposed to the cargo.

2. Seal arrangementThe MarFlex deepwell pump is supplied as standard with a special seal arrangement to separate the cargo from the lubricating oil and vice versa.This seal design has proven over many years to be a simple and reliable seal for all chemicals and mineral oil products.

The seal arrangement is built up as follows: •Uppersealarrangementwithoilseal•Lowersealarrangementwithsinglecargoseal and double cargo seal

Between the two seal arrangements there is an atmospheric drainage chamber.This chamber is called the ‘cofferdam’, and it acts as a safety barrier.Anyleakagethatmightoccuriscollectedinthecofferdam. The cofferdam is connected to the main deckbymeansoftwopurgelines.By purging the cofferdam with air or nitrogen, its contentscanbeblownoutandcollectedondeck.A regular purging routine enables the condition of the seals to be constantly monitored.

The advantages of this seal arrangement are:•Doubleprotectionwithanatmosphericdrainage

chamber between the cargo side and the lubricating oil side.

•Proventobesimpleandreliable.•Easyreplacementbytheship’screw(lowcost).•Sealconditioncanbemonitoredfromthemaindeckside.

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Pump materials

The MarFlex deepwell pump is made entirely of

stainless steel AISI 316L.

All seals and O-rings in contact with the cargo are

made of Teflon® or Kalrez®. Thanks to the materials

used, the MarFlex deepwell pump is fully chemical-

resistant and suitable for handling cargoes with a

temperature up to 100°C.

On request, the MarFlex deepwell pump can also be

made from higher grade materials, such as ‘duplex’ or

‘super duplex’, to fulfil the customer’s requirements.

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Stripping procedureWhenthecargotankisempty,thecargostrippingvalvemust be opened and the main cargo valve closed.The residual cargo left in the main cargo pipe is removed by forcing inert gas or air via the stripping pipe into the cargolineondeck.Duringthestrippingprocedure,thepumpshouldbekeptrunning(theimpelleractsasadynamicfootvalve) until the cargo pipe is completely empty.This procedure guarantees an absolute minimum of residual cargo in the pump well, and complies with all IMO rules.

Outlet stripping pipe

Inert gas /air under pressure

Main cargopipe

Stripping cargo pipe

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INERT GAS / AIRUNDER PRESSURE

MAIN CARGO PIPE

STRIPPING CARGO PIPE

SNAP-ON-COUPLING

SNAP-ON-COUPLING

NON-RETURN VALVE

CARGO STRIPPING VALVEOPEN

OPTIONAL:DIRECTLY TO MANIFOLD

FLEXIBLE HOSE OPEN

MAIN CARGO VALVECLOSED

OPEN

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Pumping Excellence

Louis Pasteurstraat 123261 LZ Oud-BeijerlandThe Netherlands

T +31-186-890200F [email protected]

MarFlex Europe (Headquarters)Oud-BeijerlandThe [email protected]

MarFlex Services Oud-BeijerlandThe [email protected]

MarFlex Asia Singapore

MarFlex GuangzhouGuangzhouChina

MarFlex MoscowMoscowRussia

MarFlex do BrasilRio de Janeiro Brazil

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Marflex Brochure Deepwell Pumps_lr2013

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