Flowserve Worthington LNN Axially Split Double-Suction Pump

Flowserve LNN axially split double-suction pump: what it is

The Flowserve LNN, sold under the Worthington name, is a single-stage, double-suction centrifugal pump built with an axially split casing. Liquid enters the impeller from both sides, which balances axial thrust and keeps the net positive suction head requirement low. The result is a pump that moves very large volumes at moderate head, with the maintenance advantages of a casing that opens along the shaft axis.

Seven Star LLC supplies Flowserve LNN pumps in Oman and the GCC as an independent supplier in Muscat. LNN is a pump series, not a single ordering code: the right size, materials, sealing and driver arrangement are fixed from your duty point. This page explains the range, the layout variants and the information we need to prepare a quotation.

LNN technical specifications

How the LNN double-suction design works

In a double-suction impeller the liquid is split into two streams that enter the impeller eye from opposite sides. Because each side sees the same pressure, the axial forces cancel almost completely, and the thrust bearing carries only a small residual load. Splitting the inlet flow also lowers the velocity at the eye, which is why this layout achieves good suction performance on duties with limited NPSH available.

The LNN casing uses double-volute hydraulics. A single volute produces uneven pressure around the impeller when the pump runs away from its best efficiency point, and that imbalance shows up as radial load on the shaft. The double volute evens this out, reducing radial force at low flow and protecting seals, bearings and wear rings from the deflection that shortens their life.

LNN layouts and related designations

The same product family page groups several configurations that share the LNN hydraulic concept. The plain LNN is horizontally mounted with side suction. Orientation and nozzle arrangement are then changed to suit the installation.

Bottom-suction layouts such as LNNC suit pump stations where the suction pipe arrives from below the floor, and the vertical layouts suit sites where floor space is the limiting factor. Confirm the layout you need before the casing is selected, since it affects nozzle positions and the foundation drawing.

Where the LNN fits and related pumps

The LNN is a large-volume, moderate-head machine. It is typically found in raw-water intake, cooling-water circulation, condenser water, transfer and booster duties. When the head requirement is higher than the LNN envelope allows, a multistage between-bearings pump is the usual alternative. For related Flowserve between-bearings designs, see the UZDL two-stage API pump, the HED two-stage radially split pump and the DMX multistage pump, which cover higher pressures than the LNN.

The page for the family also lists user-instruction manuals and a maintenance checklist for the LNN, LNNV and LNNC, which are useful when planning spare parts and overhaul intervals.

Selection and ordering checklist for the LNN

• Rated flow and the required head at that flow, plus minimum and maximum operating points
• Liquid, density, temperature and any solids, chlorides or dissolved gases
• Net positive suction head available at the pump suction flange
• Required layout: horizontal, vertical or bottom-suction (LNN, LNNV, LNNC)
• Flange standard and pressure class for suction and discharge piping
• Driver power, speed, supply frequency (50 or 60 Hz) and whether a variable speed drive is used
• Sealing preference: packing or mechanical seal, with flush and cooling plan
• Materials for casing, impeller, shaft and wear rings, matched to the liquid

Installation, commissioning and maintenance of the LNN

An axially split pump is sensitive to pipe strain, so suction and discharge piping should be supported independently and aligned to the nozzles without force. Set the baseplate on a properly grouted foundation, check soft foot, and align the coupling hot and cold where the temperature rise is significant. Before first start, prime the casing and vent it fully; a double-suction pump running with trapped air loses prime quickly.

During routine service, watch bearing temperature, vibration and seal leakage. The separate 360-degree bearing housings give good shaft support and easier access, and the split casing lets the rotor be lifted out for wear-ring inspection without disturbing the piping or the driver. Keep a spare set of wear rings, bearings and seal parts, since these are the components most often replaced at overhaul. We can quote spare parts if you send the pump serial number or nameplate details.

LNN applications in Oman and the GCC

Large water-handling pumps are central to the Gulf region. In desalination plants, LNN-class pumps serve intake, transfer and distribution duties. Power stations use them for cooling-water circulation, where high flow at moderate head is exactly what the design delivers. Municipal water transmission, irrigation and flood-control systems use the same type of machine.

Site conditions matter in this climate. High ambient temperature, sand and dust, and warm, saline water put demands on bearing cooling, seal selection and material choice. Corrosion resistance of the wetted parts and a sealing arrangement that tolerates abrasive particles should be specified from the start rather than corrected after commissioning.

Information to send with an LNN RFQ

So that we can respond quickly and accurately, please include the following with your request:

• The pump designation (LNN, LNNV or LNNC) and size, or the nameplate photo of the existing unit
• Duty point, operating range and the liquid data listed above
• Required flange standard, driver and seal arrangement
• Whether you need the pump alone, a complete baseplate package, or spare parts only
• Delivery location in Oman or the GCC and the required timeline

Documents and quotation

Send the LNN designation, size and duty data and we will confirm the available documents and a quotation. Seven Star LLC supplies Flowserve products as an independent supplier in Muscat and is not the manufacturer.

Please ask for the user instructions and maintenance checklist for your exact layout when planning installation and overhaul.