All OH-type pumps adopt a single-stage overhung construction. Impellers are supported by shafts only on one side, with the bearing box carrying all axial and radial loads. They are subdivided into six types (OH1-OH6) according to layout, coupling configuration and drive integration modes.
OH1 Foot-supported Horizontal Overhung Pump Horizontal arrangement with flexible-coupling drive. The pump casing is foot-mounted at the bottom. A separate baseplate connects the pump and motor via flexible coupling. As the classic horizontal centrifugal pump for chemical-process services, it features convenient maintenance and is suitable for conveying conventional media under normal temperature and pressure.
OH2 Centerline-supported Horizontal Overhung Pump Also of horizontal flexible-coupling configuration, while the pump casing is supported at the shaft-centerline elevation. When temperature fluctuates, thermal expansion or contraction will not cause casing displacement or additional stress. It is specially designed for high-temperature hot-oil and high-temperature process-medium services.
OH3 Vertical In-line Overhung Pump (Separate Bearing Bracket) Vertically installed in-line with pipeline, equipped with an integrated independent bearing bracket and driven by motor through flexible coupling. Straight-through pipeline layout saves floor space, widely applied for pipeline boosting transfer.
OH4 Rigid-coupled Vertical In-line Pump Vertical in-line arrangement. Pump shaft and motor shaft are rigidly directly-connected without flexible coupling for simplified construction. This configuration cannot fully satisfy all stringent requirements of API 610, and shall only be applied for mild, low-risk services.
OH5 Close-coupled Vertical In-line Pump Closed close-coupled design. The impeller is mounted directly on the motor output shaft with no separate coupling, delivering the most compact footprint. It also fails to fully comply with stringent API-610 design requirements, limited to low-pressure clean-media transfer.
OH6 High-speed Gear-driven Overhung Pump High-speed overhung pump integrated with an integral speed-increasing gearbox. The impeller is fitted on the gearbox output shaft, and the gearbox is flexibly coupled to the motor. It can be installed either horizontally or vertically, intended for low-flow high-head high-pressure services such as high-pressure feed-water and chemical-process boosting.
For BB-series pumps, impellers are supported by bearings on both sides. Symmetrical rotor support ensures outstanding operational stability. The portfolio covers single-stage, two-stage and multi-stage variants, categorized as BB1-BB5 based on casing split style and casing quantity. BB-type pumps represent mainstream selections for high-pressure, large-flow and heavy-duty services.
BB1 Axially-split Single / Two-stage Between-bearings Pump The pump casing is horizontally axially split along the shaft centerline. Two mounting forms are available: foot-mounted (BB1-A) and near-centerline mounted (BB1-B). Disassembly and reassembly can be performed without disconnecting suction & discharge piping for easy maintenance. Commonly used for large-flow circulating-water and raw-material transfer.
BB2 Radially-split Single / Two-stage Between-bearings Pump Casing is radially split perpendicular to shaft axis, featuring superior pressure-bearing capacity compared with axially-split BB1. Suitable for single- / two-stage medium-and-high-pressure media transfer, widely adopted in petrochemical-raw-material and boiler-feed-water applications.
BB3 Axially-split Multi-stage Between-bearings Pump Combines axially-split casing and multi-stage impeller assembly. It balances easy maintenance and multi-stage high-head requirements, selected for medium-pressure large-flow long-distance conveyance.
BB4 Radially-split Single-casing Segment-type Multi-stage Pump Single-casing radially-split segmental construction, also known as tie-bolt pump. Individual stage segments are clamped by long tie bolts. Risk of inter-stage media leakage exists; this design does not fully comply with all API-610 criteria, mostly used for low-pressure multi-stage water-supply duties.
BB5 Radially-split Double-casing Barrel-type Multi-stage Pump Double-wall barrel-type construction. Inner casing adopts radial split, and the outer barrel bears full process pressure and isolates process fluid. It achieves extremely high pressure rating, serves as core pump equipment for refinery hydro-processing and high-pressure processes, fully compliant with stringent API-610 high-temperature high-pressure operating conditions.
All VS-type pumps feature vertical suspended configuration. Pump casings are submerged below liquid level inside tanks or sumps, while motors and bearing assemblies are located above liquid surface. Classified as VS1-VS7 by casing structure, flow-passage form and driving mode. Mainly deployed for liquid extraction from tank farms, wastewater sumps and underground storage tanks.
VS1 Single-casing Diffuser-can Type Vertical Sump Pump Single-casing with internal diffuser vanes. Process medium is discharged upward through central discharge riser with stable flow-path performance. Frequently used for clean-chemical-liquid storage tanks.
VS2 Single-casing Volute-can Type Vertical Sump Pump Single-casing volute-type construction with fluid discharged via riser. Compared with diffuser-type VS1, VS2 delivers better hydraulic efficiency under large-flow conditions, primarily for wastewater and crude-oil tank transfer.
VS3 Single-casing Axial-flow Vertical Suspended Pump Axial-flow impeller design for large-flow low-head duties, similar to mixed-flow storm-water pumps. Applied for large-volume pool circulation and flood-drainage services.
VS4 Long-shaft Multi-guide-bearing Vertical Sump Pump Extended shaft reaching deep into liquid, equipped with multiple intermediate guide bearings. Applicable for deep-wall storage tanks. Bearings are immersed in process fluid; service is limited to media providing adequate lubrication.
VS5 Overhung-type Vertical Sump Pump without Submerged Guide Bearings Short overhung rotor with no submerged intermediate guide bearings. Rotor load is entirely undertaken by upper-side bearings only. Eliminates bearing wear caused by submersion in process fluid, suitable for solids-bearing and scaling-prone media.
VS6 Double-casing Diffuser-type Vertical Suspended Pump Based on VS1 single-casing diffuser pump with additional outer pressure-containing shell. Double-casing construction greatly enhances pressure resistance. Specially for high-pressure storage tanks and hazardous-toxic-fluid applications.
VS7 Double-casing Volute-type Vertical Suspended Pump Upgraded double-casing variant derived from VS2 volute pump. Combination of volute inner casing plus pressure-bearing outer barrel satisfies both large-flow conveyance and high-pressure sealing requirements. It is the preferred selection for high-hazard chemical-tank liquid extraction.
API 610 unifies industry-wide language for design, procurement and maintenance via standardized pump-type designations. Users can select proper sub-models within OH / BB / VS series according to operating temperature, pressure, flow-rate, medium properties and installation space. It serves as the universal technical reference for centrifugal-pump selection and equipment management within petroleum-chemical sectors.