Basic Structure and Working Principle
What is an OH (Overhung) Pump
OH (Overhung) pumps, such as the LZA model from Longgang Pump, feature a design where the impeller is mounted on the end of a shaft that is supported by bearings on only one side. The foot-mounted single-stage cantilever centrifugal pump is mainly used to transport clean or containing trace particles, neutral or highly corrosive, low-temperature or high-temperature liquids.
What is a BB (Between Bearings) Pump
BB pumps are characterized by having bearings on both sides of the impeller, offering increased stability and support for high-load applications. For example, the LBD(BB2) series of heavy-duty petrochemical process pumps are horizontal, radially split, single-stage, two-stage, or three-stage centrifugal pumps with between bearing structure.
Key Structural Differences
OH pumps are typically simpler in construction and easier to install due to their overhung design. In contrast, BB pumps like the LBD feature a dual-end support structure with centerline mounting that enhances performance under high-temperature conditions. The BB2 type also includes a double volute structure to reduce radial forces and extend bearing life, which is absent in most OH designs.
Performance Comparison in Industrial Applications
Flow Rate and Pressure Capabilities
OH1(LZA) pumps offer flow rates from 5.5 to 2600 m³/h and heads up to 250m with working pressure up to 5MPa. On the other hand, the LBD(BB2) pump supports higher pressure applications with flow rates suitable for heavy-duty petrochemical processing and pressures up to 30MPa, depending on configuration.
Vibration and Operational Stability
BB pumps generally exhibit better vibration control due to symmetric bearing support. The rigid shaft design of BB2 ensures the operating speed remains below critical speed for smooth operation. Meanwhile, OH pumps like LZA include features such as balance holes and wear-resistant rings for axial force balancing, but may not match BB types in extreme conditions.
Energy Efficiency Considerations
The independently developed BB2 efficient centrifugal pump achieves a verified hydraulic optimum efficiency point of 90.5%, which is 3.5% higher than the national first-level energy efficiency standard. This makes BB designs more energy-efficient for large-scale operations compared to typical OH models.
Suitability for Different Operating Conditions
High-Temperature and High-Pressure Environments
BB2 pumps are ideal for high-temperature services due to their centerline mounting that prevents misalignment from thermal expansion. In contrast, OH1 models like LZA are suitable for moderate temperature ranges up to +200°C but may require additional cooling systems in more extreme conditions.
Corrosive or Abrasive Fluids Handling
Both types can handle corrosive fluids depending on material selection. Longgang has developed special alloy material pumps, such as anti-dilute sulfuric acid, hydrochloric acid, and concentrated sulfuric acid, using super-low carbon duplex stainless steel materials. Customized material options enhance resistance across both pump types.
Space and Installation Constraints
OH pumps have an advantage in compact installations because of their smaller footprint. The pull-out design of the LZA model allows maintenance without disturbing piping. However, if space allows, BB pumps offer superior durability and performance under demanding conditions.
Longgang Product Overview and Recommendations
Longgang LBD(BB2)-Radial Dissection Chemical Process Centrifugal Pump
LBD series is designed according to API610 standards with centerline mounting and double volute casing for reduced radial load. It is ideal for transporting high-pressure and high-temperature media in petrochemical plants.
Longgang LZA(OH1)-Single Stage Cantilever Centrifugal Pump
LZA adopts a volute casing with an optional double volute hydraulic design at DN80 outlet sizes to balance radial force effectively. It’s best suited for clean or slightly contaminated liquids in chemical processing environments requiring moderate performance levels.
Application Scenarios for Each Model
Use the LZA model when installation space is limited or when dealing with less aggressive fluids at moderate pressures. Choose the LBD model when handling critical media under high-pressure/temperature environments such as vacuum units or quenching cycles in ethylene plants.
Maintenance, Durability, and Lifecycle Cost
Ease of Maintenance and Downtime Reduction
Both the LZA and LBD series feature back-pull-out designs, allowing maintenance without disturbing piping systems. However, BB pumps often require more time due to heavier components despite their longer maintenance intervals.
Spare Parts Availability and Service Life
Longgang provides qualified spare parts according to customers’ needs. With strong OEM capabilities and lifecycle support, including regular return visits and 24-hour problem resolution commitment, customers benefit from long-term reliability.
Total Cost of Ownership Analysis
Although initial investment in BB pumps may be higher due to complex construction, lower downtime frequency combined with higher energy efficiency results in reduced total cost over time. For OH types like LZA, lower upfront costs suit budget-sensitive applications with less demanding operational profiles.
Selection Guidelines Based on User Needs
Choosing Based on Flow, Head, and Fluid Type
For flows exceeding 1000 m³/h at heads above 300m under corrosive/high-temperature conditions—BB2 (LBD) is recommended. If your application involves flow under 500 m³/h with moderate head requirements, OH1 (LZA) offers an efficient yet economical solution.
Industry-Specific Recommendations (Chemical, Petrochemical, etc.)
For petrochemical refining units, LBD models serve well as raw material oil pumps or quenching circulation systems. In environmental protection engineering or general chemical transfer, LZA provides robust performance while maintaining easy installation benefits. All models can be customized based on user-specific fluid properties or site constraints.
Longgang Pump offers not only standardized solutions but also full-cycle customized services—from design through after-sales—ensuring optimal performance across diverse industries. Contact us today at info@longgangpump.com or call +86 18865532020 to explore how our bb pump or oh pump solutions can meet your operational challenges efficiently.
FAQ Section
Q: What’s the main difference between OH and BB pump structures?
A: OH (Overhung) pumps have impellers supported on one end only; BB (Between Bearings) pumps have impellers supported on both ends, offering greater stability under high loads.
Q: Which type is better for high-pressure applications?
A: BB pumps like Longgang’s LBD series are better suited due to their dual-end support structure that handles pressure more effectively.
Q: How do I choose between an OH1 pump like LZA versus a BB2 like LBD?
A: Choose based on your specific flow rate, head requirement, fluid characteristics, temperature/pressure conditions—and consult our technical advisory team for customized recommendations tailored to your needs.
