1. Overview of the Water Pump
Pumps, as a key equipment for fluid transportation, are widely used in various fields such as industry, agriculture, and daily life. Through the rotation of the impeller, they lift liquids from lower levels to higher ones, or transfer them from one place to another to meet various process requirements. There are numerous types of pumps, and when selecting one, it is necessary to comprehensively consider the specific application scenarios and performance requirements.
2. Overview of Pumps
Pumps, which are mechanical devices for transporting liquids or increasing their pressure, play a crucial role in construction projects. They are mainly responsible for transporting domestic and industrial water and are the core power source of the building water supply system. The working principles of pumps vary, but they can be broadly classified into three types: centrifugal pumps, axial flow pumps, and mixed flow pumps. Among them, centrifugal pumps are the most common in construction projects, and their functions are diverse, including water supply pumps, hot water pumps, fire pumps, sewage lift pumps, and circulation pumps, etc. In addition, technical parameters for evaluating the performance of pumps are also very important, covering aspects such as flow rate, suction height, head, shaft power, water power, and efficiency.
Related standards
After gaining an understanding of the basic knowledge of water pumps, we further explored the industry standards related to them. These standards cover various aspects such as the technical conditions of well-used submersible pumps, the methods for measuring pump flow, and the installation and acceptance specifications of pumps, providing clear guidance for the design, production, and use of water pumps.
The composition of the water pump
Next, we will delve into the internal structure of the water pump.
According to the main structure of the pump, it can be divided into seven key parts: the suction component, the impeller, the discharge component, the support component, the shaft seal component, the balance device, and other auxiliary devices. The suction component is located before the impeller and mainly responsible for guiding the liquid smoothly into the impeller. The impeller, as the core working element of the pump, is responsible for efficiently converting mechanical energy into the energy of the liquid. The discharge component, usually located around or behind the impeller, functions to collect and discharge the liquid flowing out from the impeller, while converting some of the kinetic energy into pressure energy. The support component is responsible for enabling the impeller to rotate and perform work effectively, as well as bearing some of the axial and radial forces. The shaft seal component is of crucial importance as it can prevent the leakage of the high-pressure liquid inside the pump or the entry of air into the pump. The balance device is mainly used to balance or reduce the axial force, ensuring the stable operation of the pump. In addition, there are other auxiliary devices such as lubrication devices and cooling devices, which together ensure the efficiency and reliability of the pump.
In addition, the model of the pump is also crucial for understanding its structural features and working performance. Different types and specifications of pumps have different models. The following lists some common pump models and their meanings: The BA type pump, such as 8BA-18A, where 8 represents the diameter of the suction pipe joint as 8 inches, BA indicates a single-stage single-suction cantilever centrifugal pump, and 18 is a simplified representation of the specific speed, while A indicates a reduced outer diameter impeller. The SH type pump, such as 48SH-22, 48 represents the diameter of the suction pipe joint as 48 inches, which is 1.2 meters in diameter, SH indicates a single-stage double-suction horizontal split vertical centrifugal pump, and 22 is a simplified value of the specific speed. The DA type pump, such as 3DA8x9, 3 represents the diameter of the suction pipe as 3 inches, DA indicates a multi-stage segmented centrifugal pump, and 8 and 9 respectively represent the specific speed and the number of impeller stages. The DG type pump, such as DG270-150, DG represents a boiler feed pump, 270 and 150 represent the flow rate and the outlet pressure respectively. The N and NL type pumps, such as 8NL-12, 8 represents the diameter of the suction pipe opening as 8 inches, N indicates a condensate pump, L indicates a vertical structure, and 12 is a simplified value of the single-stage head. Through these models, we can gain an in-depth understanding of the various performance and characteristics of the pumps.
The naming rules for NB, NBA, GN, and GNL type pumps are as follows: N represents a condensate pump, B indicates a suspended type, BA indicates a bracket type, G indicates a higher suction head, and L indicates a vertical type. Taking the 6PWL pump as an example, PW type pump, where 6 represents the diameter of the discharge pipe in inches, P indicates an impurity pump, W indicates wastewater, and L is the simplified value of the single-stage head. And the XB type pump, such as XBD-20-50-HY, its name includes XB indicating a fire pump, D indicating motor drive, 20 and 50 represent the rated flow rate of 20 L/s and the rated pressure of 50 meters water column pressure respectively, and HY indicates a constant pressure pump.
3. Detailed explanation of pump parameters
Flow rate: refers to the capacity of the pump to convey liquid in a unit of time, commonly expressed in m3/h (cubic meters per hour) or L/s (liters per second).
Head: This refers to the energy that a pump exerts on a unit weight of fluid. It is typically measured in units such as m (meter of water column) or MPa (megapascal of pressure).
Efficiency: This reflects the power utilization situation of the water pump during the water lifting process. It is calculated as the ratio of effective power to shaft power.
Power: It includes shaft power and effective power. Shaft power is the power that the motor transmits to the pump shaft through the transmission equipment, while effective power is the power obtained by the water flow within the pump.
Speed: Refers to the number of rotations per minute of the pump's impeller.
Model: A unique code that comprehensively reflects the performance of the water pump.
Suction Head: Also known as "maximum self-suction height", it refers to the maximum height at which the water pump can automatically draw water without the aid of a suction pipe. Its calculation formula is [Suction Head = 10.33 (standard atmospheric pressure) - Cavitation Margin - 0.5 (safety margin)].
In addition, there are pump inlet diameter and outlet diameter, which respectively refer to the pipe diameters of the water pipes connected to the pump inlet and outlet. At the same time, the cavitation margin is also a key parameter, representing the excess energy of the liquid per unit weight at the pump suction inlet that exceeds the vaporization pressure. The unit is m (meters).
Key Parameters and Selection Points
The position of the water pump has specific requirements regarding the spacing of the foundation and the distance from the wall. For pumps with a power of less than 22KW, the minimum spacing of the foundation is 0.4 meters and the minimum distance from the wall is 0.8 meters; for pumps with a power ranging from 22KW to 55KW, the minimum spacing of the foundation should be 0.8 meters and the minimum distance from the wall is 1.0 meters. For pumps with a power exceeding 55KW, the minimum spacing of the foundation and the distance from the wall should be at least 1.2 meters each.
When choosing a water pump, the flow rate and head are the key factors. The flow rate should be at least the maximum instantaneous flow rate or 1.1 to 1.15 times the maximum daily flow rate. At the same time, the height difference between the pump and the least water-utilizing point as well as the water head loss in the pipeline should be fully considered. In addition, it is necessary to consult the samples of each water pump manufacturer, select a series of pumps that meet the basic performance based on the pump series spectral chart, and comprehensively consider the comprehensive parameters and quotations of each series of pumps to make the optimal choice.
In terms of specifications and models, the energy-saving performance indicators of the equipment are of great significance, including motor efficiency, pump efficiency, and overall efficiency. These indicators generally should not be lower than specific parameters. At the same time, other standard parameters such as the size of the unit should also be paid attention to. The size can be adjusted according to the manufacturer's size, but the limitations of the on-site installation site should also be considered.
If the manufacturer provides the quotation directly, the delivery address is usually at the project site. However, the equipment placement needs to be clearly communicated and agreed upon separately with the installation subcontractor. Besides, during the equipment acceptance and installation process, a series of matters need to be paid attention to to ensure that the automatic fire sprinkler pump can be safely and efficiently put into use.
Transportation and Installation of Water Pumps
After leaving the factory, the water pump is usually transported by road using trucks. During the lifting process, it is necessary to strictly follow the manufacturer's instructions and use the lifting ears of the equipment for stable lifting. Also, ensure that it avoids bumpy sections during transportation to reduce unnecessary vibrations. Please note that the water pump has undergone detailed testing and debugging before leaving the factory, so special attention should be paid to the protection of the finished product during installation.
The installation position of the pump is of vital importance. It must meet the requirements of the allowable suction vacuum height. At the same time, it is necessary to ensure that the foundation is stable and level to guarantee that the rotation direction of the power machinery is consistent with that of the pump. During the installation process, if the pump and the power machine are connected by shaft, the center of the shafts must be on the same straight line to prevent unnecessary vibration and single-sided wear of the bearings during the operation of the unit. If belt drive is used, the centerlines of the shafts should be kept parallel and the belt pulleys should be aligned.
Furthermore, when installing multiple units in the same machine room, there should be a distance of at least 800mm between each unit and between each unit and the walls. The suction pipe of the water pump must be kept well sealed and the number of bends and gate valves should be minimized. When adding water, the air should be completely drained to ensure that no air accumulates in the pipe during operation. The suction pipe should be slightly inclined upwards and connected to the water pump's intake port, and the intake port should have a certain submerged depth. Finally, the reserved holes on the pump foundation should be poured according to the specific size of the pump.
The key points during equipment installation include: The installation position of the water pump should be as close to the water source as possible to shorten the length of the suction pipe; the foundation at the installation site must be stable. For fixed water pumps, the preparation for the pump foundation (pump set foundation) should be done in advance.
2. The inlet pipeline must be kept sealed reliably, especially for pipes with a diameter greater than DN200, special supports should be provided to ensure stability.
3. The pump and motor base should be installed horizontally and firmly connected to the foundation. If belt drive is used for the machine and pump, ensure that the tight side of the belt is on the bottom to achieve efficient transmission, and the rotation direction of the pump impeller must be consistent with the arrow indication. If coupling transmission is used, the machine and pump must be strictly coaxial.
4. The installation position of the pump must meet the requirements of the allowable suction vacuum height, and the foundation must be level and stable to ensure that the rotation direction of the power machinery is consistent with that of the pump.
5. The suction pipe of the water pump must be well sealed to reduce the number of bends and gate valves. When adding water, completely drain the air, and there should be no air accumulation in the pipe during operation. The suction pipe should be slightly inclined upwards and connected to the pump inlet, and the inlet must have a certain submerged depth.
Supplementary and Notes
When ordering the variable frequency pump set as a package, components such as the variable frequency control cabinet, air pressure tank and the base of the unit are usually included. When choosing the pump, it is necessary to pay attention that it is the core product of the variable frequency water supply equipment and directly determines the water supply capacity. The variable frequency pump unit is usually a parallel operation of multiple pumps, with one of them serving as a backup pump.
In terms of control mode, the following options are available: the main pump operates continuously while the auxiliary pump performs automatic rotation; or the main and auxiliary pumps rotate alternately. This is to prevent the standby pump from remaining idle for a long time, which could lead to failure. The accompanying electrical control cabinet is divided into a conventional relay control type and a variable frequency speed control type. The measurement and control part can be controlled using an electrical contact pressure gauge or a pressure sensor.
When choosing a controller, priority should be given to the solution that can address the oscillation problem of the pump when the critical flow occurs. At the same time, ensure that the accessories such as the frequency converter and circuit breaker are of high-quality brands, which will facilitate maintenance and the purchase of spare parts.
Regarding the selection of pressure tanks, it is recommended to choose automatic air replenishment tanks (jet air replenishment or small pump air replenishment). These tanks can automatically detect and replenish air, ensuring that the pressure tank is always in the maximum energy storage state. They are not limited by the installation method of the equipment, which is conducive to the design of mechanical-electrical integration, and are also cost-effective.
The pressure tank has an automatic detection function, which can replenish air according to the demand, thus ensuring that it is always in the maximum energy storage state.
The installation method of the pressure tank is flexible. It can work normally whether it is installed separately or connected in series in the pipeline network.
The reliability of the pressure tank has been significantly improved.
The energy storage device equipped with an automatic air replenishment device is relatively independent in design, simplifying the design process.
