1. The core structural differences between OH1 and OH2
1. OH1: foot support structure
OH1 adopts the foot installation method, and the pump casing is fixed on the base through the lower legs. It has the characteristics of relatively simple structure, easy installation and maintenance.
However, when transporting high-temperature media, the thermal expansion of the pump casing may cause the centerline of the shaft to shift relative to the driver, making thermal alignment and pipeline stress control more difficult. Therefore, OH1 is more suitable for working conditions with small temperature changes and relatively low mechanical load requirements.
It should be noted that API 610 has specific applicable restrictions on OH1, and the equipment cannot be deemed to meet all the requirements of the standard based on the OH1 structure code alone.
2. OH2: centerline support structure
OH2 adopts a centerline support design. The pump casing is supported close to the centerline of the shaft and bears the rotor load through an independent bearing box.
This structure helps reduce the shaft centerline displacement caused by thermal expansion and improves alignment stability under high-temperature operation and frequent temperature changes. OH2 is usually used in oil refining, petrochemical industry, high-temperature oil products and devices with high continuous operation requirements.
2. Comparison of key technical parameters of OH1 and OH2
| Comparison project | OH1 pump | OH2 pump |
|---|---|---|
| Pump type structure | Single-stage cantilever type | Single-stage cantilever type |
| Installation method | base support | Centerline support |
| Influence of thermal expansion | Need more attention to axis displacement | More conducive to controlling axis displacement |
| Applicable temperature | Normal temperature and conditions with small temperature changes | High Temperature and large temperature changes |
| Bearing layout | Based on specific design | Independent bearing box |
| Maintenance requirements | Relatively simple | Need to pay attention to bearings, seals and auxiliary systems |
| Typical applications | General chemicals and auxiliary processes | Refining, petrochemicals and key processes |
| Purchasing costs | Usually lower | Usually higher |
Note: API 610 does not specify a uniform maximum flow rate, head or operating temperature for all OH1 and OH2 pumps. Actual capabilities depend on manufacturer series, materials, pressure rating and specific design.
3. How to select OH1 and OH2 pumps?
1. Select a medium with normal temperature and small temperature fluctuation based on temperature and thermal expansion.
The economics of OH1 can be evaluated first.
For high-temperature hydrocarbons, hot oil and frequent hot and cold alternating working conditions, priority should be given to evaluating the centerline support advantages of OH2. A certain temperature value cannot be simply used as the absolute boundary between the two pump types.
2. Check flow rate, head and NPSH
Purchasers need to clarify at least the following parameters:
Normal, minimum and maximum flow (m³/h)
Rated head and system resistance (m)
Inlet pressure, outlet pressure and design pressure
Medium temperature, density, viscosity and vaporization pressure
Device available NPSHa (NPSHa)
Continuous operating time and start-stop frequency
When selecting, the rated operating point, priority operating range and minimum continuous stable flow should be confirmed based on the performance curve, and ensure that NPSHa meets the required NPSHr of the pump and project margin requirements.
3. Check materials and mechanical seals
For corrosive media, the suitability of stainless steel, duplex steel or other alloy materials needs to be evaluated; for media containing particles, the risk of wear and blockage should also be considered.
For high-temperature, flammable or toxic media, it is necessary to focus on determining the mechanical seal form, API 682 sealing scheme and flushing cooling system. The applicability of the whole machine cannot be judged solely based on the temperature resistance of the pump casing.
4. Evaluate the nozzle load and maintenance conditions
High-temperature pipes may transmit additional loads to the pump body. The allowable force of the nozzle, base stiffness, coupling alignment requirements, and on-site maintenance space should be confirmed before purchasing.
OH2 centerline support is beneficial to thermal stability, but it cannot replace correct pipe stress analysis and installation alignment.
5. Common purchasing issues of OH1 and OH2
Is OH2 definitely more efficient than OH1?
Not necessarily. Pump efficiency depends primarily on hydraulic design, impeller size, rotational speed and actual operating point. Centerline bracing does not directly improve hydraulic efficiency.
Can OH1 transport high temperature media?
Yes, but thermal expansion, materials, sealing and shafting alignment conditions need to be verified. High temperature applications cannot be determined based solely on the pump model code.
Can OH2 directly replace the existing OH1 pump?
Cannot be replaced directly by default. There may be differences in the base, pipe orifice position, coupling center height and auxiliary pipelines. The installation dimensions and pipe interfaces must be checked before modification.
7. Feiyue Pump Industry OH1/OH2 Product Solutions
Jiangsu Feiyue Pump Industry provides a variety of petrochemical process pumps, which can be selected according to medium characteristics, design temperature, flow and pressure requirements.
Among them, the published flow range of Feiyue OH2 petrochemical process pump series is 3–2600 m³/h, and the head range is 4–300 m; different FZA/FZE configurations have different design pressure and temperature ranges.
