Is the power of the already installed centrifugal pump rated, regardless of the opening degree of the outlet valve?

Overview, definitions, and differences between safety valves and relief valves. I. Overview Safety valves are important safety accessories installed on boilers, pressure vessels, and other pressurized equipment. The reliability of its operation and its performance have a direct impact on the safety of equipment and people, and are closely related to energy conservation and environmental protection. And some users and design departments always choose the wrong model when making selections. To this end, this paper analyzes the selection of safety valves. II. Definition: In a broad sense, a safety valve includes relief valves. From the perspective of regulatory requirements, it is a valve that must be installed directly on steam boilers or pressure vessels of category 1, and it is necessary for such a valve to be approved by the technical supervision authorities. In a narrow sense, it is referred to as a safety valve; other similar valves are generally called relief valves. Safety valves and relief valves are very similar in structure and performance; both discharge the fluid inside automatically when the set pressure is exceeded, in order to ensure the safety of the production equipment. Due to this fundamental similarity, people often confuse the two when using them; furthermore, some manufacturing equipment also specifies that either one can be used. Therefore, the differences between the two are often overlooked. As a result, many problems have arisen. If a more precise definition for both is to be provided, it can be understood in accordance with the definition outlined in Part 1 of the ASME Boiler and Pressure Vessel Code: (l) Safety Valve – An automatic pressure relief device driven by the static pressure of the medium in front of the valve. It is characterized by a sudden, full-open starting action. Used for gas or steam applications. (2) Relief Valve, also known as a overflow valve, is an automatic pressure relief device driven by the static pressure of the medium in front of the valve. It opens proportionally as the pressure exceeds the opening force. It is mainly used in fluid applications. (3) Safety Relief Valve: Also known as a safety overflow valve, it is an automatic pressure-relief device driven by the pressure of the medium. It can be used as either a safety valve or a relief valve, depending on the application. Taking Japan as an example, there are few clear definitions for safety valves and relief valves. Devices used as safety mechanisms in large pressure vessels such as boilers are generally referred to as safety valves, while those installed on pipes or other equipment are called relief valves. However, according to the \"Thermal Power Generation Technology\" guidelines issued by Japan’s Ministry of International Trade and Industry, safety valves are specified as an essential component for ensuring safety in equipment such as boilers, superheaters, and reheaters. Where the lower side of the pressure relief valve needs to be connected to a boiler and a turbine, a drain valve or safety valve must be installed. From this perspective, safety valves are required to be more reliable than relief valves. Furthermore, based on the regulations regarding the management of high-pressure gases set by Japan’s Ministry of Labor, as well as the rules established by the Ministry of Transport and various ship associations concerning the acceptable levels of emissions, we refer to valves that ensure such controlled emissions as safety valves, while those that do not guarantee controlled emissions are called relief valves. In China, both fully open and slightly open types are collectively referred to as safety valves. This post was last edited by dyzdyz12345 on 2009-4-4 22:09.]

There is an inverse relationship between the discharge head and head lift; can it be said that P*H = constant? Wrong; the Q-s curve of a pump is not straight. If it were, then a higher flow rate from the pump would correspond to a lower head, and a lower head would correspond to a higher flow rate, right? It looks like this on the Q-s curve. How can energy be saved in pump operation according to the Bernoulli equation? Select a pump with appropriate flow rate and head based on the process requirements. Considering both energy consumption and equipment wear, is it better to use a high-flow backflow operation or a low-flow throttling operation for the working flow rate? I would be very grateful if some experts could give me some advice. The flow rate should be determined based on the process requirements; if the backflow is too high, the motor will operate under excessive current, which is harmful to the motor. In such cases, it is recommended to use an appropriate pump or implement frequency control.

Thank you. One more question: For a pump with a rated flow rate of 550 m3/h, can throttling be used to control the liquid level when the actual operating flow rate is 250 m3/h? Would a backflow operation be more ideal? From the perspective of device optimization

In your case, variable frequency control is the best option – it provides stability, saves energy, and is beneficial for both the motor and the pump

Is the power rated? How should I say that? The rated value is only a theoretical figure. From the perspectives of energy conservation and equipment performance, variable frequency control is the preferred option; if not available, throttling at a low flow rate should be employed according to the process requirements.

The operating condition of the pump depends on the process requirements of the pipeline. To meet the process requirements, methods such as backflow generation or using outlet valves to restrict flow may be employed to control flow or pressure, and all of these will result in energy losses for the pump. It is recommended to make a reasonable choice regarding the process selection, and variable frequency technology can be adopted for post-treatment based on economic considerations.

Power is related to flow rate; the greater the flow rate, the more work is done. Of course, when the outlet valve is opened wider, the relative power increases.

Another question: For a pump with a rated flow rate of 550 m3/h, can throttling be used to control the liquid level when the actual operating flow rate is 250 m3/h? Would a backflow operation be more ideal? From the perspective of device optimization, the opinion on the 3rd floor is correct. For ordinary centrifugal pumps, backflow regulation is not required (except for high-speed pumps or those where there is a large difference between the rated flow rate and the actual flow rate). Normally, we use control valves to regulate flow, which is essentially throttling control. At this point, part of the energy output by the pump is wasted on the control valve. To save energy, the best approach is to use up-conversion, followed by reducing the size of the impeller, etc

The head and flow rate of a centrifugal pump are related to the structural dimensions of its impeller; a larger diameter results in a higher head； Large width, high flow rate ； It is related to speed; flow rate is directly proportional to speed ； Additionally, the head of a pump is related to the number of impeller stages, while the head of a centrifugal pump is independent of specific gravity.