Hoechun KIM*
Goro KATO**
Junya KAWABATA***
Akinori MURATA*
Satoshi YAMAZAKI*
*
New Business Development Department, Business Development Division, Fluid Machinery and Systems Company
**
Business Development Division, Fluid Machinery and Systems Company
***
Fluid Machinery Development Department, Business Development Division, Fluid Machinery and Systems Company
Model GSO, classified as a single-stage end-top centrifugal pump, was developed as a core product for various industrial fields in the global market. This product ensures more versatility and reliability by complying with international standards including ISO 5199 and ISO 2858. Furthermore, for covering a wide range of services, it is designed to use a uniquely shaped impeller (reverse-open impeller. the impeller’s hub plate is open) to handle not only clean applications but also process liquids containing light slurries. High efficiency, high quality, and enhanced usability have been achieved using fluid, structural, vibration analysis and experiments as development and design techniques.
Keywords:Single-stage end-top centrifugal pump, Industrial pump, Reverse-open impeller, ISO 5199, ISO 2858
We developed a single-stage end-top centrifugal pump model GSO (Fig. 1), which is our core product for industrial applications for the global market, while ensuring versatility and reliability by complying with the international standards ISO 5199 and ISO 2858.
GSO type pumps are our core products; we meet customer needs with products designed from our experience accumulated from the Japanese industrial market and our development technology, and strengthen the local supply chain in cooperation with overseas production bases.
This paper will provide an overview and introduce features of GSO model pumps for the global market.
Fig. 1 Single-Stage End-Top Centrifugal Pump Model GSO
In order to handle a wide variety of handling liquid in the industrial field, this pump features a reverse-open impeller without a balance hole so that a small quantity of slurry can be discharged. The unique impeller design reduces the pressure inside the box of the shaft seal and achieves the same performance as a pump with a closed type impeller. The shapes of the impeller front and back shrouds were designed and developed in several patterns to balance the shaft thrust on the impeller. An example of those shapes is shown in Fig. 2.
Fig. 2 Impeller shape
The shaft seal is provided with gland packing and other mechanical seals that can handle various circumstances in order to deal with special process liquids. Quenching is used to prevent damage or leakage from the mechanical seals for handling liquids that crystallizes during running of the pump and for handling liquids that are at low temperature. Double seals, in which barrier fluids are used, cartridge-type seals, and special structure seals are also available.
In order to support various handling liquids in chemical plants and various industrial applications in the global market, the technical specifications of GSO type pumps conform to ISO 5199, flange connection and main dimensions conform to ISO 2858, and the seal box dimensions refer to ISO 3069.
Reverse-open impeller, which is one of the pump’s most distinguishing features was developed using CFD(Computational Fluid Dynamics) analysis. We checked the degree of thrust reduction and slurry discharge by looking at how various shapes of impellers affect the performance of the pump and from the results calculated for shaft thrust, and designed the impeller front and back shrouds to an unique and optimal shape to facilitate shaft thrust adjustment. We actually measured the performance and shaft thrust of the impeller and confirmed that it met the specified performance and function. Fig.3 shows an example of the CFD analysis result. The streamlines are along the shape of the vanes without separation vortices, and the desired blade loading for the impeller has been obtained.
Fig. 3 Example of flow analysis
The reverse-open impeller development ensures not only low shaft thrust and high efficiency, but also strength. The results of FEM (Finite Element Method) analysis of the strength of the impeller using the stresses obtained by CFD analysis are shown in Figure 4. The minimum value is shown in blue and the maximum value is shown in red. Though there were some stress concentrations in the key way and the shroud side and the boss side of the impeller, we confirmed that the stress value was below the fatigue limit.
We carried out endurance tests on the actual pump, and passed the penetrant test(PT).
By carrying out structural analysis and tests as described above, we confirmed that this impeller had sufficient strength.
Fig. 4 FEM analysis
The bearings were selected after the shaft thrust on the impeller was accurately obtained by CFD analysis and actual measurement.
As a standard specification, we adopted grease-shield single row deep groove type ball bearings, which do not require frequent maintenance and are easy to handle. Oil bath type bearings can also be used, when long-term use or cooling is required. The pump also supports back-to-back angular contact ball bearings (oil bath type) that can withstand a larger axial load.
Fig.5 shows the structures of each type of bearings. Each structure of the bearings satisfies the minimum 17,500 hours of bearing life L10 required in ISO 5199. L10 refers to the basic rated life and is a substantial total rotating time (rotated at constant rotational speed), when a group of the same bearings are individually rotated under the same conditions, 90% (90% reliability) of them can rotate without flaking due to rolling fatigue.
Fig. 5 Structure of each bearing
The ISO 5199 standard stipulates the upper limit of the vibration velocity around the bearings at the operating point. On the other hand, in the case of JIS B 8301 applied in Japan, although vibration is evaluated by amplitude, even if the amplitude satisfies the specified value of JIS B 8301, there is a case in which the value of the vibration velocity specified by ISO 5199 cannot be satisfied. Therefore, during the development of GSO model pumps, when the vibration velocity was large, we confirmed the vibration mode by analyzing the frequency and the mode of the vibration from a specific frequency that had a large impact and based on the results, we strengthened the structure and reviewed the operating flow to meet the vibration value specified in ISO 5199.
ISO 5199 stipulates that the shaft deflection at the seal face of a mechanical seal shall not exceed 50μm. This is the same shaft deflection value specified by API 610, which requires an even stricter design than general industrial applications. The basic design of the pump shaft has been optimized by taking into consideration the balance between shaft deflection, product cost, and common use of components, which entail trade-offs with each other.
The components of this pump are used in common in order to reduce the initial investment in wooden patterns, to reduce costs by reducing the number of parts, and to improve operational convenience such as inventory control. We have raised common use of parts in the same model and other models and maximization of adoption of standard parts as the highest priority from the initial stage of development, and have adopted drastically new designs and reviewed components from the conventional equivalent model. As a result, we have succeeded in making 58.8% of the components common.
The flange corresponds to PN 16 of the European standard EN 1092, and the maximum working pressure is 1.6 MPa. The shaft seal supports gland packings and mechanical seals. The table below shows the main specifications.
| Handling liquid | liquid name | Chemical liquid |
| liquid temperature | -30 to 150 °C | |
| Density | 0.7 to 1.2 kg/L | |
| Max. operating pressure | 1.6 MPa | |
| Construction | Impeller | Reverse-open type |
| Bearing | Shield ball bearing / ball bearing | |
| Lubrication | Grease lubrication / oil lubrication | |
| Shaft seal | Mechanical seal | Rotating type / unbalanced type |
| Gland packing | Carbonized fiber | |
| Flange | EN PN16 | |
| Material | Casing | SCS13/SCS14A |
| Impeller | SCS13/SCS14A | |
| Shaft | SUS304/SUS316 | |
Performance ranges are shown below and in Figs. 6 and 7.
Suction nozzle diameter: 50 to 250 mm
Flow capacity: up to 1400 m3/h (50/60 Hz)
Total pump head: up to 150 m (50 Hz), up to 140 m (60 Hz)
Fig. 6 GSO model selection chart 2P - 50 Hz
Fig. 7 GSO model selection chart 4P - 50 Hz
This pump has a back pull-out structure that allows disassembly and inspection without removing the suction and discharge piping. The top center-line discharge and foot support structure provides sufficient strength against the piping loads. By providing a necessary rigidity in the bearing housing and related structures, the standards for vibration, shaft deflection, and bearing life required by ISO 5199 are met.
Due to the structure in which the bearing housing and the pump casing are connected by an adapter, four types of bearing housings can be used for various lubrication methods. The reverse-open impeller allows for easy adjustment of the clearance between the impeller and the gland cover with the impeller shim on the back of the impeller. A cut model of the pump is shown in Fig. 8.
Fig. 8 Cut model of GSO model pump
We have released our first GSO model pump for industrial fields that conforms to ISO 5199 in the global market.
The concept of the commercialization is to realize a user-friendly and reliable pump at a high level. In addition to the outstanding performance and functions of the pump, the unique impeller shape and pump shape have enabled us to realize a more reliable product because of the well-balanced integration of the superior technologies of standard pumps, industrial pumps, and custom pumps.
In the future, based on the track record we have cultivated for customers in Japan, we will increase the number of pump types by expanding the casings and impellers with improved special shaft sealing structures, materials, high and low temperature specifications, and slurry resistance, and we will expand our business to a wider range of special industrial fields in the global market.
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