1. The main differences between OH2, BB2, BB3 and BB5
OH2 is a single-stage cantilever, radially split, centerline support process pump. The impeller is located outside the bearing box. It has a compact structure and easy maintenance. It is suitable for petrochemical processes with medium flow and lift. The centerline support can reduce the impact of thermal expansion of the pump casing on shaft system alignment under high temperature conditions.
BB2 is a two-end supported, radially split process pump, usually using a single-stage or two-stage structure. The impeller is located between two sets of bearings. The rotor rigidity and high temperature stability are better than those of cantilever pumps, making it suitable for higher temperature, pressure or inlet pressure conditions.
BB3 is an axially split multi-stage pump, with multiple impellers connected in series to produce high head. The rotor can be inspected by opening the upper cover of the pump casing. Maintenance is relatively easy, and it is suitable for high-lift working conditions such as oil transportation, pipeline pressurization, boiler water supply, and oil field water injection.
BB5 is a double-casing cylindrical multi-stage pump. The internal multi-stage pump core is installed in the pressure-bearing outer cylinder. It is suitable for ultra-high pressure, high temperature, flammable media and key stations of the device. It is the structure with the highest pressure-bearing capacity and operational reliability requirements among the four types of pumps.
2. Technical parameters that must be confirmed when selecting models
Buyers should provide at least the following data when making inquiries:
Normal, minimum and maximum flow;
Normal head, pressure difference or inlet and outlet pressure;
Media name, density, viscosity and vapor pressure;
Operating temperature and design temperature;
Suction pressure and device effective cavitation head NPSHa;
Solid particles, corrosive and flammable and explosive characteristics;
Continuous or intermittent operation requirements;
Explosion-proof level, power supply, sealing and flushing scheme;
Execution standards, material requirements and inspection levels.
The selection point should be close to the best efficiency point of the pump to avoid long-term operation at low flow rates or far away from the high-efficiency area. For high-temperature, volatile media, NPSH margin, minimum continuous stable flow, thermal expansion, and mechanical seal auxiliary systems must also be checked.
3. How to match typical engineering applications?
OH2 is commonly used in atmospheric and vacuum devices, chemical processes, light hydrocarbon transportation, circulation and pressurization stations. Its advantages are mature structure and convenient spare parts management, which is suitable for a large number of general process pump positions.
BB2 is suitable for high-temperature oil products, heavy hydrocarbons, bottom liquid and high inlet pressure processes. When the OH2's shaft deflection, bearing loading, or housing pressure capabilities are insufficient, the BB2 is usually a safer choice.
BB3 is suitable for crude oil and refined oil pipelines, boiler water supply, mine drainage and oil field water injection. For high-lift projects, emphasis should be placed on checking interstage sealing, axial force balance, critical speed and variable working condition performance.
BB5 is often used in high-pressure feeds, hydrogenation units, boiler water feeds and other key stations that cannot be shut down easily in refineries. The outer cylinder can withstand high system pressure, and the pump core structure is easy to extract and repair as a whole, but the equipment cost and manufacturing requirements are higher.
4. Selection errors that are likely to occur during procurement
1. Determine the pump type only based on the head. Under the same head, the required structure may be completely different if the medium temperature, inlet pressure and hazard level are different.
2. I think BB5 must be better than BB3. BB5 has a stronger pressure-bearing capacity, but the procurement, spare parts and maintenance costs are also higher. If BB3 can meet the pressure, temperature and reliability requirements, it is not economical to blindly upgrade.
3. Ignore the actual operating range. If the pump is operated below the minimum continuous stable flow rate for a long time, backflow, temperature rise, vibration and seal damage may occur.
4. Only compare initial prices. Critical process pumps should also be compared for efficiency, maintenance intervals, spare parts availability, sealing systems and life cycle costs.
5. Purchasing suggestions and product solutions
For general petrochemical processes and medium parameter working conditions, OH2 can be evaluated first; BB2 can be selected when high temperature, high inlet pressure or higher rotor rigidity is required; BB3 can be evaluated when high lift and maintenance convenience are important; BB5 can be mainly considered for ultra-high pressure, critical equipment and high-risk media.
Feiyue Pump Industry can provide OH2 petrochemical process pumps, BB2 two-end support pumps, BB3 axially split multi-stage pumps and BB5 double-shell multi-stage pump selection plans based on flow, head, temperature, medium properties, inlet conditions and device standards, as well as supporting material selection, mechanical seals, flushing systems, performance testing and pump skid complete services. Providing a complete operating condition table before purchasing can help engineers determine a more reliable and economical pump type.
