Understanding the optimal flow rate range and allowable operating range of centrifugal pumps
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Dear colleagues: According to API6106.9.3.1, centrifugal pumps are classified into preferred operating areas and allowable operating areas. I have a few questions and would appreciate your guidance: 1. During the design phase of a centrifugal pump, the process parameters are determined based on the process requirements, which in turn helps to define the preferred and allowable operating areas. Is it the design institute that determines these areas, or does the pump manufacturer determine them based on the process parameters of the pump? If it is the pump manufacturer who makes the decision, then how can data accuracy be ensured during the design phase? In other words, how can process quality be controlled? Please ask the relevant personnel for some guidance. 2. During the manufacturing phase, how do pump manufacturers produce centrifugal pumps that fully meet the design requirements, based on their own manufacturing capabilities? In other words, how to accurately produce centrifugal pumps that meet user requirements by translating design ideas into reality through manufacturing? (Could a friend from a pump manufacturer answer these questions?) 3. During the acceptance phase, whether it is the manufacturer’s factory testing or the user’s on-site performance inspection, how can these two operating areas be measured accurately? What is the specific process? The question might be a bit confusing, jian’liang
1. The design only specifies parameters; the workspace is generally not taken into consideration； The pump factory should select the model based on the given parameters; if no suitable option can be found, it should inform the client. If none of the manufacturers can provide a suitable solution, then the design parameters need to be modified. 2. Pump manufacturers generally only supply pumps based on existing models; therefore, it is unlikely that they can produce pumps that precisely meet the design parameters and operate at their optimal efficiency point, unless one is willing to invest the necessary funds for custom manufacturing. 3. During on-site inspection, these two areas will not be checked; it is necessary to determine at the time of selection how much the deviation from the optimal efficiency point is, and whether it falls within an acceptable range.
Take a look at the performance curves and hydraulic models
This post was last edited by RichardChan on 2020-6-23 at 13:58. 1. The priority workspace is POR; the workspace AOR is defined based on the BEP (Best Efficiency Point), which is a characteristic of the pump itself. The process parameters are determined; the manufacturer selects the pump based on these parameters, while the owner or the design institute (if one is hired for the design work) decides whether the chosen pump is suitable. When selecting a model, the parameter values should preferably fall within the preferred operating range; however, in some cases, due to stringent process requirements, it may not be possible to stay within this range, such as in scenarios involving low flow rates and high head pressures. Since the BEP points vary among different manufacturers/pump models, it is possible that the pump model chosen by a supplier has its rated value outside its optimal operating range (do not blindly assume that the manufacturer’s selection is correct). At this point, it is necessary to identify this issue during the technical clarification phase and request that a different pump model be selected. If the supplier is indeed unable to find a suitable pump model, then it can be accepted as long as it remains within the allowable operating range. However, when evaluating the technologies of several suppliers, priority was given to pump types whose rated values fall within the preferred operating range. Of course, when determining whether a pump’s curve is appropriate, the optimal operating range is just one factor to consider; other elements such as the shape of the curve (for example, whether a hump-shaped curve affects operation), the NPSH difference, and whether the operating point lies to the right of the BEP also need to be taken into account. 2. Manufacturers all have their own quality assurance systems, with the key focus being on how these systems are implemented. In some cases, the quality assurance systems are merely documents kept in cabinets for use during inspections. So try to find manufacturers that strictly implement a quality assurance system and have a good reputation. 3. For the performance testing of pumps, 5-6 points are generally measured, and the software will automatically generate the test curve. The acceptance criterion is that the deviation from the specified point (the parameter value set by the manufacturing process) being within the acceptance range defined in the contract constitutes compliance.
The interval is determined by the shape of the curve; the design allows for adjustments to narrow or widen this curve shape, but these adjustments are not necessarily accurate – the curve from the factory tests should still be taken as the reference
:) Questions 1 and 2 should be answered together. Generally, pump manufacturers have a range of hydraulic models as well as standardized products developed based on the performance of manufacturers both domestically and internationally. These products are compared with the customer’s specific requirements and data, and finally a suitable standardized product is selected (according to the selection criteria). If no such standardized product is available, it is possible to develop a new set that meets the requirements using the existing hydraulic models, or to create new hydraulic models from scratch (though this is generally not done in China due to the high costs). The hydraulic models and standardized products mentioned above have all been tested in the market and have proven track records, so they can be considered reliable (regarding the second question). Before shipment, pump manufacturers conduct their own tests on the performance of the pumps; two operating conditions are taken into account during the design phase, and subsequent tests are carried out to verify those performances
Priority work areas and permitted work areas depend on the pump models and performance curves provided by various manufacturers. Each manufacturer has its own catalog of pump models. First, based on the flow rate and head parameters provided by the buyer, the appropriate pump model is selected from this catalog; thereafter, parameters such as the medium, net positive suction head, shaft power, and efficiency are taken into account to determine the most suitable pump model. 1. As for the issue of compatibility mentioned by the original poster, it is related to the manufacturer supplying the products. For example: 1.1 When selecting pumps for the standard OH1 and OH2 applications, domestic manufacturers offer a wider range of pump models compared to those from joint-venture companies, making it easier to find a better-suited pump model. 1.2 However, when selecting pumps for the more complex BB3, BB4, and BB5 types, the pump models offered by the joint venture manufacturers have an advantage. 2. During the manufacturing phase, an ITP is prepared in accordance with relevant standards at the time the technical agreement is signed; supervision of manufacturing can then be carried out based on that ITP. 3. Priority operating area and allowable operating area: When selecting a pump, there are expected performance curves available, which determine whether the pump will operate in the priority operating area or the allowable operating area. During manufacturing, performance tests are conducted to verify the correctness of the assembly, thereby assessing the pump’s efficiency (since if the shaft alignment is not properly adjusted during assembly, it can result in a misalignment between the center of the impeller and the center of the flow channel, which in turn reduces the pump’s efficiency).
The pumps are standardized; choose the one whose parameters are closest to yours. The error might be significant, but as long as it works, the efficiency level doesn’t matter