FVD (VS6)

The API VS6(model FVD) pump is a vertically suspended, double-casing centrifugal pump designed in accordance with API 610 (ISO 13709). Its defining characteristic is the barrel or suction can configuration: the pump bowl assembly is enclosed within a fabricated or cast suction can that forms an integral part of the pump. The can is typically installed below grade or within a tank, creating its own suction vessel from which the pump draws liquid. This design is particularly suited to services with limited available NPSH (Net Positive Suction Head), as the submerged can provides a flooded suction condition that effectively eliminates cavitation concerns .

The VS6 pump comprises four primary components: the suction can, bowl assembly, column pipe, and discharge head. The suction can is manufactured in compliance with boiler and pressure vessel standards and may be supplied with U-Stamping upon request. Anti-vortexing features are incorporated into the can design to ensure smooth, uniform flow into the first-stage impeller .

The bowl assembly contains single or multiple stages of diffuser-type bowls with enclosed radial impellers. Each impeller is fitted with front and rear wear rings and balance holes to minimize axial loads. The bowls are bolted together individually with metal-to-metal joints, permitting easy disassembly while ensuring leak-proof operation suitable for high-temperature applications .

The column pipe connects the bowl assembly to the discharge head and encloses the drive shaft. For low-flow, high-head duties, the shaft may be supported by intermediate radial bushings spaced along the column. For longer column lengths, a divided shaft with rigid couplings is employed to maintain alignment and facilitate installation .

Capacities range from small flows up to approximately 5,000 m³/h, with some specialized designs reaching higher. Heads can reach up to 1,600 m, depending on the number of stages and pump speed. Design pressures up to 160 bar are achievable, with some applications requiring up to 220 bar. Operating temperatures span from cryogenic services down to −195°C up to approximately 300°C, depending on materials and construction.

Technical Parameters

DESIGN STANDARD	API610
FLOW RATE	Up to 5000 m³/h
HEAD	Up to 1600 m
APPLIED TEMPERATURE	-195~300℃
MAX PRESSURE	16Mpa
General Description	VS6 pump is designed and manufactured according to API610 Standard.

Product Features

Vertical Wet-Pit, Line-Shaft Design – Pump element suspended below ground in a wet pit or sump; driver mounted above ground on a discharge head, connected by a vertical line shaft.
Double-Casing Construction – Inner cartridge (bowl assembly) enclosed within an outer barrel or pressure casing; the inner element can be removed without disturbing the outer casing or main piping, simplifying maintenance.
Radially Split Inner Casing – Diffuser/bowl casing is radially split (vertically split), with stages stacked in series for high head at moderate-to-high flow.
Diffuser-Type Bowl Assembly – Single or multistage diffuser bowls with axial or mixed-flow impellers, delivering high head and high efficiency.
Excellent Low-NPSH Performance – First-stage impeller is submerged in the pit liquid, providing very low NPSH required (NPSHr); ideal for services with low NPSH available (NPSHa) where horizontal pumps would cavitate.
Flexible Sealing Options – Packing gland or API 682 compliant mechanical seals at the discharge head.
Standards Compliant – Fully compliant with API 610 / ISO 13709 heavy-duty process pump requirements.

Applications

VS6 pumps are widely used in refinery and petrochemical services including condensate extraction, LPG and LNG handling, tank farm booster service, and crude oil pipeline applications. Chemical processing, power generation, and cryogenic services are also common applications. The barrel configuration is particularly valuable for installations where available NPSH is extremely low—below 1 meter or even approaching zero—such as LPG storage tank export pumps and cryogenic liquid transfer . The integral suction can creates its own effective NPSH, making the VS6 an ideal solution for low-boiling-point hydrocarbon services.