1. Introduction
In refinery and petrochemical applications, selecting the right pump type is critical for ensuring reliability, efficiency, and long-term operation. Among the various pump types defined in API 610, OH2 and BB2 pumps are two of the most commonly used configurations.
Although both are centrifugal pumps designed for demanding services, their structural differences make them suitable for different operating conditions. This article explains the key differences between OH2 and BB2 pumps and provides practical guidance for selection.
2. What is an OH2 Pump?
An OH2 pump is a single-stage, overhung, horizontal centrifugal pump with a centerline-mounted casing.
Key characteristics:
l Overhung impeller design (impeller mounted at shaft end)
l Single bearing housing
l Flexible coupling to driver
l Centerline support for thermal stability
Typical applications:
l General refinery services
l Medium pressure and temperature fluids
l Clean or slightly contaminated liquids
3. What is a BB2 Pump?
A BB2 pump is a single-stage, between-bearings centrifugal pump, typically with a radially split casing.
Key characteristics:
Impeller located between two bearings
Double-bearing support for higher shaft rigidity
Better load distribution
Designed for higher pressure services
Typical applications:
High-pressure hydrocarbon services
Critical process units
Applications requiring high reliability
4. Key Differences Between OH2 and BB2 Pumps
5. Application Comparison
When to use OH2 pumps:
l General process services
l Moderate pressure and temperature
l Cost-sensitive projects
l Easier maintenance required
When to use BB2 pumps:
l High-pressure systems
l Critical units (e.g., hydrocracking, boiler feed)
l Continuous operation with minimal downtime
l Applications requiring higher mechanical stability
6. Selection Guide
Choosing between OH2 and BB2 pumps depends on several key parameters:
1. Operating Pressure
Medium pressure → OH2
High pressure → BB2
2. Reliability Requirement
Standard duty → OH2
Critical service → BB2
3. Fluid Conditions
Clean / low viscosity → both suitable
Severe conditions → BB2 preferred
4. Maintenance Strategy
Frequent maintenance acceptable → OH2
Long continuous operation required → BB2
5. Budget Consideration
Lower CAPEX → OH2
Higher initial cost but longer lifecycle → BB2
7. Practical Example
In refinery applications:
OH2 pumps are often used in:
Transfer services
Utility systems
Light hydrocarbon handling
BB2 pumps are typically selected for:
High-pressure feed systems
Reactor charging
Critical process circulation
8. Conclusion
Both OH2 and BB2 pumps play essential roles in petrochemical and refinery industries. The choice between them should not be based solely on cost, but on a comprehensive evaluation of operating conditions, reliability requirements, and lifecycle considerations.
In general:
OH2 = flexibility + lower cost
BB2 = stability + high reliability
9. Need Technical Support?
If you are selecting pumps for refinery or petrochemical applications and are unsure whether OH2 or BB2 is the better choice, feel free to contact us.
We can provide:
Pump selection support
API 610 compliant solutions
Customized designs for critical applications
