Analysis of OH Centrifugal Pump Centerline Mounting

In harsh working conditions such as petrochemical and high-temperature fluid transfer, the stability of OH centrifugal pumps (compliant with API 610 standards) is crucial. As a core mounting method, centerline mounting is widely used in heavy-duty OH2/OH3 pump models. What makes this design unique?

1. What is Centerline Mounting?

At a refinery's pump area renovation site, I saw technicians comparing the mounting differences between OH1 and OH2 pumps: the OH1 pump is fixed via feet at the bottom of the casing, while the OH2 pump's flange is directly aligned with the reference line on the base plate — this is a straightforward manifestation of centerline mounting. This structural design is explicitly required by API 610 standards and can effectively address operational challenges in high-temperature and high-pressure environments.

2. Why Choose Centerline Mounting?

The key lies in solving the problem of thermal expansion. When the pump transfers high-temperature media (such as hot oil at 200-400℃), the casing and shaft will undergo expansion and deformation. Traditional foot mounting is prone to misalignment between the pump shaft and motor shaft, causing vibration, seal leakage, and even bearing damage. Centerline mounting, by fixing the central axis, allows thermal expansion to distribute evenly along the axis of symmetry, maintaining alignment stability. For example, a refinery once experienced seal leakage in a foot-mounted pump after only three months of transferring hot oil at 380℃; disassembly revealed a 0.2mm offset between the pump shaft and motor shaft. After switching to centerline mounting, similar issues never occurred again.

3. Three Core Advantages of Centerline Mounting

In practical operation and maintenance, these advantages are not just theoretical but can truly reduce troubles:

• Strong thermal stability: A pump in an ethylene plant needs to switch between cold and hot media frequently, with temperature fluctuations ranging from 80℃ to 320℃. However, the pump with centerline mounting maintains a vibration value below 4.5mm/s after each switch, far lower than the standard limit.
• High maintenance efficiency: Previously, repairing a foot-mounted pump took 8 hours just to disassemble the motor and align the shafts. In contrast, for a centerline-mounted pump with a back-pull-out rotor, when we replaced the mechanical seal last year, it only took 3 hours — no need to disassemble the motor, just pull out the rotor directly, saving most of the time.
• Improved reliability: Checking our company's equipment records, under high-temperature conditions, the average trouble-free operation time of centerline-mounted pumps can reach 18 months, while most foot-mounted pumps can only last about 12 months — a significant gap of 30%-40%.

4. Application Scenarios and Mounting Key Points

Typical applications:

• High-temperature media transfer (≥150℃), such as hot oil circulation systems in refineries
• High-pressure working conditions (≥2.5MPa), such as reactor feed pumps in chemical plants
• Critical process equipment, such as solvent transfer pumps in PTA plants

Key mounting steps:

① The base plate must be grouted and fixed to ensure foundation vibration resistance;

② Use a laser alignment tool to calibrate the pump shaft and motor shaft, with a deviation ≤0.05mm/m;

③ Install compensation gaskets at the flange to eliminate the impact of micro-deformation of the base;

④ Recheck the alignment status after installation and the first thermal cycle.

5. Conclusion

Centerline mounting is not just a simple fixing method but a systematic solution designed to address the operational pain points of heavy-duty pumps. From thermal expansion control to maintenance convenience, its value runs through the entire life cycle of the pump. For industrial scenarios requiring long-term stable operation, choosing a centerline mounting scheme compliant with API 610 standards is an important decision to ensure production continuity.

If you found this content helpful, feel free to follow Teffiko—we’ll keep releasing the latest industry insights, technical guides, and pump application cases to support your operations! For personalized advice or product inquiries, don’t hesitate to reach out to our team.