Inline Centrifugal Pump

FILIPUSI manufactures space-optimized LD Series vertical inline centrifugal pumps engineered to install directly into straight horizontal pipelines. By eliminating concrete inertia bases, our long-coupled inline circulation series delivers continuous 24/7 reliability across HVAC chillers, district heating networks, process cooling systems, and industrial fluid manifolds.

The LD Series features a rigid long-coupled configuration with a spacer coupling and dedicated bearing bracket. Its Back Pull-Out design allows service teams to replace mechanical seals without removing the motor or disconnecting piping — critical for critical HVAC systems and large pumps where downtime must be minimized. The inline design installs directly into piping like a valve, reducing installation cost and mechanical room footprint by up to 40%.

Typical applications: HVAC chillers, district heating & cooling, process cooling, industrial fluid manifolds, cooling towers, high-rise commercial water boosting, closed-loop circulation systems, and solar thermal water transfer.

FILIPUSI LD series vertical inline pump installed in a horizontal HVAC pipeline — no concrete base required.

Technical Specifications

Every FILIPUSI LD inline pump undergoes hydrostatic pressure testing and performance verification before shipment. Custom voltages, frequencies, flange standards, and mechanical seal configurations are available on request.

How Vertical Inline Pumps Work

A vertical inline centrifugal pump operates on the same hydraulic principle as a standard end suction pump — an impeller spinning inside a volute casing converts rotational energy into fluid pressure — but with a critical layout difference: the suction and discharge nozzles are aligned on the same horizontal centerline. This coaxial design allows the pump to sit directly in a horizontal pipeline, with fluid entering one nozzle, passing vertically through the impeller, and exiting the opposite nozzle on the same axis.

Why the Inline Layout Saves Space and Cost

Because suction and discharge share the same pipeline axis, there is no need to route piping up and over a baseplate-mounted pump, and no concrete inertia foundation is required. The pump effectively becomes a component in the pipe run — like a valve — reducing mechanical room footprint by up to 50% compared to horizontal end suction configurations. The vertical orientation also means the pump shaft is perpendicular to the pipe axis, so thermal expansion of the pipeline is absorbed axially rather than bending the pump casing, reducing stress on flanges and seals.

Single-Stage Pressure Generation

The LD inline pump is single-stage, meaning one impeller generates the full discharge pressure. This makes it ideal for medium-head circulation duties (12 to 160 m) where high flow and reliable continuous operation matter more than extreme pressure. For applications requiring heads above 160 m — such as high-rise pressure boosting or boiler feed — FILIPUSI recommends our vertical multistage pump series, which stacks multiple impellers to build higher pressure without increasing rotational speed.

LD Series Long-Coupled Design & Construction

The LD Series uses a rigid long-coupled configuration with a spacer coupling between the motor shaft and pump shaft, and a dedicated bearing bracket integrated into the pump casing. This design is preferred for larger pumps and critical-process applications because it offers superior serviceability and independent bearing support for high-thrust hydraulic loads.

Back Pull-Out Maintenance

The defining feature of the LD long-coupled design is its Back Pull-Out capability. By unbolting the spacer coupling, technicians can slide the entire rotating assembly — shaft, impeller, bearings, and mechanical seal — out through the rear of the pump without removing the electric motor and without disconnecting the suction or discharge piping. Mechanical seal replacement can typically be completed in under one hour, compared to several hours for designs that require full motor removal and pipe disconnection.

Dedicated Bearing Bracket

Unlike close-coupled designs where the pump shaft extends into the motor bearings, the LD Series has its own independent bearing housing. This isolates hydraulic thrust loads from the motor bearings, extending motor bearing life and allowing the use of heavy-duty angular contact bearings for high-thrust applications. The bearing bracket also provides a rigid mounting surface that maintains precise shaft alignment even under thermal expansion.

Spacer Coupling Alignment

The spacer coupling connects the motor shaft to the pump shaft and requires precision alignment at installation. Once aligned, the rigid coupling maintains concentricity throughout the pump's service life, minimizing vibration and reducing mechanical seal wear. The spacer element also allows the motor to be removed independently for servicing without disturbing pump alignment.

View LD Series Full Specifications, Curves & Dimensions »

Core Advantages & Engineering Features

Space-Saving Inline Design

Installs directly into horizontal pipelines like a valve, cutting baseline footprint requirements by up to 50% and eliminating concrete inertia bases. Ideal for mechanical rooms with limited floor space and for retrofitting existing pipe runs where adding a foundation is impractical.

Back Pull-Out Serviceability

The spacer coupling and long-coupled design allow complete rotating assembly removal for maintenance without disconnecting suction/discharge piping or removing the motor. This reduces maintenance downtime by up to 60% compared to non-back-pull-out designs, critical for continuous-duty HVAC and process cooling systems.

Micrometric CNC Alignment

CNC machined in a single setup to eliminate radial run-out, preventing seal leakage and extending maintenance cycles by up to 40%. Precision coupling alignment at installation ensures permanent shaft concentricity, reducing vibration and extending bearing and seal service life.

VFD & BMS Integration

VFD and PLC ready with standard Modbus and BACnet protocols, enabling  integration into building management systems (BMS) and industrial automation networks for precise flow and pressure control. Variable speed operation can reduce energy consumption by 30–50% compared to fixed-speed throttling in variable-load HVAC systems.

Low Vibration & Quiet Operation

Precision-balanced impellers and dynamically balanced rotating assemblies keep vibration levels below ISO 10816 limits, with typical operating noise under 75 dB(A). This makes LD inline pumps suitable for installation in occupied commercial buildings, hospitals, hotels, and residential mechanical rooms where noise control is a design requirement.

How to Select the Right LD Inline Pump

Selecting the correct LD vertical inline pump requires matching four core parameters to your system requirements:

Installation & Maintenance Best Practices

Installation Guidelines

• Install the pump with the motor vertical and shaft perpendicular to the pipeline; do not mount horizontally or at an angle.
• Support the piping independently on both sides — the pump casings should not carry the weight of the pipe run.
• Allow sufficient clearance above the motor for lifting and seal replacement (minimum 1.5× motor height).
• Install isolation valves on both suction and discharge sides for maintenance without draining the system.
• Verify spacer coupling alignment after piping is connected and before first start-up — use dial indicators to ensure parallel and angular alignment within manufacturer tolerances.
• Prime the pump and vent air from the casing before starting — running dry will destroy the mechanical seal in seconds.

Recommended Maintenance Schedule

• Monthly: Inspect for leaks, unusual noise, and vibration; check motor bearing temperature and coupling condition.
• Every 3 months: Verify coupling alignment; inspect foundation bolts and pipe flanges for tightness; lubricate coupling if required.
• Every 8,000–12,000 hours: Replace mechanical seal (or annually for continuous 24/7 operation). The Back Pull-Out design allows this without removing the motor or piping.
• Every 18,000–24,000 hours: Inspect impeller and wear ring for corrosion or erosion; replace pump bearings and motor bearings.
• For corrosive or abrasive fluid service, reduce all intervals by 50%.

Frequently Asked Questions

Related Pump Categories

FILIPUSI · Zhejiang Filipusi Water Affairs Co., Ltd. · www.filipusi.com