What are the components that make up a fire pump and how can they be made more efficient?
Nov 14, 2022
Share:
What are the main components of a fire pump?
The main components of a fire pump are the impeller, the pump casing and the shaft sealing device.
1、Impeller
The role of the impeller is to transfer the mechanical energy of the prime mover directly to the liquid, in order to increase the static pressure and kinetic energy of the liquid (mainly to increase the static pressure energy).
Impeller generally has 6~12 back curved blades.
The impeller has open, semi-closed and closed types, as shown in Figure 2-2.
Centrifugal pumps Main components
Open impeller in both sides of the blade without cover plate, simple manufacturing, easy cleaning, suitable for conveying a large amount of suspended materials, low efficiency, transport of liquid pressure is not high; semi-closed impeller in the inlet side without cover plate, and in the other side of the cover plate, suitable for conveying easy to precipitate or contain particles of materials, efficiency is also low; closed impeller in the impeller in the blade on both sides of the front and back cover plate, high efficiency, suitable for conveying no Containing impurities of clean liquid. The general centrifugal pump impeller is mostly of this type.
Impeller has a single suction and double suction two suction way.
2、Pump casing
The role is to close the impeller in a certain space, so that the role of the impeller inhalation and pressure out of the liquid. The pump casing is mostly made into a snail shell shape, so it is also called a snail shell. Due to the gradual expansion of the cross-sectional area of the flow channel, so from the impeller around the high-speed liquid gradually reduce the flow rate, so that part of the kinetic energy effectively converted to static pressure energy. The pump casing not only brings together the liquid thrown out by the impeller, but is also an energy conversion device.
3、Shaft seal device
The function is to prevent the liquid in the pump casing from leaking out along the shaft or the outside air from leaking into the pump casing.
Commonly used shaft sealing device has two kinds of packing seal and mechanical seal.
The packing is generally oiled or coated with graphite asbestos rope. Mechanical seal mainly relies on the dynamic ring installed on the shaft and fixed in the pump casing between the static ring for the relative movement of the end face to achieve the purpose of sealing.
What are the factors related to the efficiency of a pump?
Water pump is a kind of energy conversion machine, energy conversion process is bound to be accompanied by energy loss, and the efficiency is the measure of this conversion, how to improve the efficiency of the pump, reduce the loss of energy? It is necessary to clarify the loss of energy in the pump. The energy loss in the pump mainly includes the following three aspects.
1, mechanical loss
Mainly liquid and impeller before and after the cover plate and the pump cavity friction loss (also called disc loss).
The proportion of disc loss is large, even up to 30% of the effective power. The test shows that the disc loss and the speed of three times proportional, and the impeller outside diameter of five times proportional. Therefore, the larger the impeller outer diameter, the larger the disc loss. Although the disc loss and the speed of three times proportional, but in a given head, with the increase in speed, the impeller outer diameter correspondingly reduced (can be considered that the pump speed doubled, the impeller outer diameter reduced by half), disc loss into five times the proportion of decline, so, with the increase in speed, disc loss does not increase, but rather decline, which is one of the reasons for the development of high-speed pump.
2、Volume loss
A part of the impeller liquid through the impeller seal ring gap leakage back to the impeller inlet and not effectively used, the formation of losses. Therefore, the seal ring gap should be as small as possible, but due to processing and assembly and other reasons, too small a gap may form bias grinding or jamming, the national standards for various types of pumps to make special provisions for the gap.
3、Hydraulic loss
Pump overflow part (from the inlet to the outlet) of the liquid fluid is bound to have speed size and direction change caused by the loss, these two parts is the hydraulic loss. To reduce this part of the loss, in addition to improving the smoothness of the overflow parts, try to use the excellent hydraulic model.
Translated with www.DeepL.com/Translator (free version)
The main components of a fire pump are the impeller, the pump casing and the shaft sealing device.
1、Impeller
The role of the impeller is to transfer the mechanical energy of the prime mover directly to the liquid, in order to increase the static pressure and kinetic energy of the liquid (mainly to increase the static pressure energy).
Impeller generally has 6~12 back curved blades.
The impeller has open, semi-closed and closed types, as shown in Figure 2-2.
Centrifugal pumps Main components
Open impeller in both sides of the blade without cover plate, simple manufacturing, easy cleaning, suitable for conveying a large amount of suspended materials, low efficiency, transport of liquid pressure is not high; semi-closed impeller in the inlet side without cover plate, and in the other side of the cover plate, suitable for conveying easy to precipitate or contain particles of materials, efficiency is also low; closed impeller in the impeller in the blade on both sides of the front and back cover plate, high efficiency, suitable for conveying no Containing impurities of clean liquid. The general centrifugal pump impeller is mostly of this type.
Impeller has a single suction and double suction two suction way.
2、Pump casing
The role is to close the impeller in a certain space, so that the role of the impeller inhalation and pressure out of the liquid. The pump casing is mostly made into a snail shell shape, so it is also called a snail shell. Due to the gradual expansion of the cross-sectional area of the flow channel, so from the impeller around the high-speed liquid gradually reduce the flow rate, so that part of the kinetic energy effectively converted to static pressure energy. The pump casing not only brings together the liquid thrown out by the impeller, but is also an energy conversion device.
3、Shaft seal device
The function is to prevent the liquid in the pump casing from leaking out along the shaft or the outside air from leaking into the pump casing.
Commonly used shaft sealing device has two kinds of packing seal and mechanical seal.
The packing is generally oiled or coated with graphite asbestos rope. Mechanical seal mainly relies on the dynamic ring installed on the shaft and fixed in the pump casing between the static ring for the relative movement of the end face to achieve the purpose of sealing.
What are the factors related to the efficiency of a pump?
Water pump is a kind of energy conversion machine, energy conversion process is bound to be accompanied by energy loss, and the efficiency is the measure of this conversion, how to improve the efficiency of the pump, reduce the loss of energy? It is necessary to clarify the loss of energy in the pump. The energy loss in the pump mainly includes the following three aspects.
1, mechanical loss
Mainly liquid and impeller before and after the cover plate and the pump cavity friction loss (also called disc loss).
The proportion of disc loss is large, even up to 30% of the effective power. The test shows that the disc loss and the speed of three times proportional, and the impeller outside diameter of five times proportional. Therefore, the larger the impeller outer diameter, the larger the disc loss. Although the disc loss and the speed of three times proportional, but in a given head, with the increase in speed, the impeller outer diameter correspondingly reduced (can be considered that the pump speed doubled, the impeller outer diameter reduced by half), disc loss into five times the proportion of decline, so, with the increase in speed, disc loss does not increase, but rather decline, which is one of the reasons for the development of high-speed pump.
2、Volume loss
A part of the impeller liquid through the impeller seal ring gap leakage back to the impeller inlet and not effectively used, the formation of losses. Therefore, the seal ring gap should be as small as possible, but due to processing and assembly and other reasons, too small a gap may form bias grinding or jamming, the national standards for various types of pumps to make special provisions for the gap.
3、Hydraulic loss
Pump overflow part (from the inlet to the outlet) of the liquid fluid is bound to have speed size and direction change caused by the loss, these two parts is the hydraulic loss. To reduce this part of the loss, in addition to improving the smoothness of the overflow parts, try to use the excellent hydraulic model.
Translated with www.DeepL.com/Translator (free version)
