Chemical Centrifugal Pump FAQ (2-1)

1. What is a chemical centrifugal pump?

A: It uses the impeller to subject the liquid flowing through the impeller to centrifugal force, which increases the mechanical energy of the liquid and thus transports the liquid. It is a machine that increases the energy of the liquid.

2. What are the characteristics of chemical centrifugal pumps?

Can adapt to the needs of chemical processes;

Preservative;

High temperature resistance, low temperature;

Wear-resistant, washable;

Reliable operation;

No leakage or less leakage;

Liquid that can deliver a critical state.

3, According to the working principle of chemical pump, what kind of structure is it divided into?

A: According to the working principle, it can be divided into: vane pump, positive displacement pump and other types of pumps: electroMagnetic Pumps that use electromagnetic energy to transport liquid electrical conductors; pumps that use fluid energy to transport liquids, such as jet pumps, air lifters, etc.

4. What is the working principle of the centrifugal pump?

A: The drive machine rotates the impeller, and the blades in the impeller drive the fluid to rotate together to generate centrifugal force. Under the centrifugal force, the fluid is swept along the blade flow path to the impeller outlet, through the diffuser, and the volute is fed. Export pipe. When the impeller rotates continuously, the fluid is continuously taken in and discharged, allowing the centrifugal pump to work continuously.

5, The advantages of centrifugal pumps?

The single-machine output flow is large and continuous, no pulse, and the operation is stable;

The pump has small size, light weight, less locality and low investment;

The device has simple structure, less wearing parts, long cycle of Yunzhuang, and small operation and maintenance workload;

Good regulation performance and reliable operation;

There is no lubrication inside the pump and the fluid delivered is not contaminated by the oil.

6, What is the flow of the centrifugal pump?

A: The flow rate of the centrifugal pump refers to the amount of liquid discharged from the discharge port of the pump per unit time.

7. How many expressions are there for centrifugal pump flow?

A: Centrifugal pump flow has two forms of expression: volume flow and mass flow.

8, What is the volume flow?

A: Volume flow (Qv) refers to the volume of liquid discharged from the discharge port of the pump per unit time, in m3/s.

9, What is the mass flow?

A: The mass flow rate (Qm) refers to the mass of liquid discharged from the drain port of the pump per unit time, in units of kg / s.

10. What is the relationship between the volumetric flow rate of the centrifugal pump and the mass flow?

A: The volume flow and mass flow of the centrifugal pump are both expressions of the flow, the relationship between the two: Qm = Qvρ

Note: (Qm is mass flow kg / s; Qv is volume flow m3 / sρ is the density of liquid, kg / m3).

11, What is the lift of the centrifugal pump?

A: The head (indenter) of the pump refers to the increase in energy per unit mass of liquid flowing through the pump, also known as the effective energy head, in m.

12. What are the lifts of the centrifugal pump?

A: The head is an energy unit that can be expressed by the height of the liquid column that pumps the liquid. It includes liquid potential energy, static pressure energy and kinetic energy.

13. Is the lift of the centrifugal pump related to other factors?

A: The theoretical head of the pump is related to the discrete, the angle at which the blade exits, the number of blades, and the flow rate of the pump.

14, How to determine the level of A Yang's continuous insurance?

The angular displacement of the blade exit, the theoretical head of the increase in the conversion flow increases accordingly; the smaller the exit angle of the blade, the increase in the transmission flow, and the corresponding theoretical lift.

The more the number of blades, the theoretical head above.

In the past few decades, the theoretical lift was the lowest.

15, What is the location of the centrifugal pump?

A: The rotation speed of the centrifugal pump refers to the number of times the unit centrifugal centrifugal pump rotor works, and its unit is r / min.

16, What is the power of the centrifugal pump?

A: The power of the pump usually refers to the work that the unit interval is transmitted from the prime mover to the pump main shaft. It is also called the shaft power, and the unit is W or KW.

17, What is the effective power of the centrifugal pump?

A: It is the effective energy obtained by outputting liquid from the pump per unit time, also known as output power, in units of W or KW.

18, What is the efficiency of the centrifugal pump?

A: The efficiency of the pump is the ratio of effective power to shaft power, which reflects the extent of energy loss in the pump.

19. What is the hydraulic loss of the centrifugal pump?

A: The hydraulic loss of a centrifugal pump is also called the flow loss, which is the difference between the theoretical head and the actual head.

20. What are the hydraulic losses of a centrifugal pump?

A: The hydraulic loss of a centrifugal pump includes three aspects: eddy current loss, loss of shrinkage loss, and impact loss.

21. What is the volume loss of the centrifugal pump?

A: Volume loss is the energy loss caused by flow leakage.

22, What is the mechanical loss of the centrifugal pump?

A: The mechanical loss is due to the loss of bearings, seal packing and wear on both ends of the impeller.

23. After the centrifugal pump changes the number of revolutions, what changes in the head, flow, and shaft power?

A: After the centrifugal pump changes the number of revolutions, its head, flow rate and shaft power also change. If the medium delivered by the pump is not changed, the flow ratio is higher than the ratio, the head ratio is equal to the square of the conversion, and the shaft power ratio is equal to the conversion. Than the cubic.

24, How to adjust the working point of the centrifugal pump?

Adjustment method to change the performance of the axial system:

(1) adjusting the discharge valve;

(2) Bypass adjustment method.

Adjustment method to change pump performance:

(1) changing the speed of the pump;

(2) changing the diameter of the impeller;

(3) Change the number of impeller stages.

25. What is the suction height of the centrifugal pump?

A: The suction height of the pump refers to the height from the liquid suction surface to the center line of the pump inlet, that is, the installation height.

26. What is the relationship between the suction height of the centrifugal pump and the temperature?

A: The temperature of the liquid rises, the pressure drop of the saturated steam, and the smaller the suction height, the more likely the pump is cavitation, so the over temperature of the medium is allowed during the pump operation.

27. What is the cavitation phenomenon of a centrifugal pump?

A: The phenomenon that the liquid is vaporized, condensed, impacted, and simultaneously forms high pressure, high temperature, high frequency impact load, causing mechanical peeling and electrochemical corrosion damage of metal materials is called cavitation.

28, How to improve the anti-cavitation performance of centrifugal pumps?

Measures to improve the cavitation resistance of centrifugal pumps are:

Measures to improve the cavitation resistance of the centrifugal pump itself;

Measures to increase the effective cavitation allowance of the inlet device.

29. What are the measures to improve the effective cavitation allowance of the inlet device?

Increase the pressure of the liquid in the tank before the pump to increase the effective cavitation margin;

Reduce the installation height of the pump of the suction device;

Replace the suction device with the suction device;

Reduce the flow loss in the axial direction of the pump.

30, The pump's allowable vacuum is related to other factors?

The saturated vapor pressure of the liquid being transported;

The diameter of the low pressure region of the impeller;

Liquid density

Screw of the pump;

Local atmospheric pressure;

The temperature of the liquid.

31, What is the role of the centrifugal pump impeller?

A: The impeller is the heart of the centrifugal pump. It is the most important part of the centrifugal pump. It is the main body for the fluid to be transported. The alternating mechanical energy can give the fluid, improve the pressure and kinetic energy of the fluid, and complete the process of transporting the fluid.

32. Where is the most prone to cavitation in the centrifugal pump?

The front cover with the largest curvature of the impeller, near the low pressure side of the inlet edge of the blade;

The volute tongue and the vane in the extrusion chamber are near the low pressure side of the inlet edge;

High ratio ratio impeller without a front baffle; a seal gap between the outer tip of the impeller and the shell; and a low pressure side of the tip;

The first stage impeller in a multistage pump.

33, Why can't the centrifugal pump be too high when it is installed?

A: When installing the centrifugal pump, the installation height must be within the allowable installation height. If the centrifugal pump is too high from the ground, the effective cavitation allowance of the liquid is reduced. When the liquid enters the low pressure zone of the pump, the pressure is lower than the liquid delivery temperature. Saturated vapor pressure, the liquid boils and vaporizes, causing cavitation and damage to the pump itself.

34, What are the components of the centrifugal pump impeller?

A: The impeller includes: blades, front cover, rear cover, and hub. Some impeller rear cover has balance holes, and some impellers have induction wheels on the front.

35. What are the types of impellers in terms of specific number of revolutions and the direction in which fluid flows in the impeller?

A: It can be divided into radial flow impeller, mixed flow impeller, oblique flow impeller and axial flow impeller.

36, What is a closed impeller?

A: The impeller with front and rear stripes is called a closed impeller. Such an impeller forms a completely closed flow passage, has a high lift head and high hydraulic efficiency, and is widely used in fluid medium without impurities in chemical plants.

37, What is the open impeller?

A: The impeller without the front cover and the small size of the rear panel and the completely exposed blade is called the open impeller.

38. What is the general purpose of the open impeller?

A: Open impeller is generally used to transport slurry, and liquid with large viscosity or solid particle suspension, which is not easy to block, but liquid is easy to reverse between the blades, so the lift and efficiency are also high, and some are added before the impeller. The induction wheel is used in a high speed centrifugal pump.

39, What is a semi-open impeller?

A: Only the impeller of the rear cover is called a semi-open impeller. Its efficiency is between the closed impeller and the open impeller, which can be used in high-speed pumps, and the induction wheel can be introduced in front of the impeller. It can be used in axial flow pumps instead of heads and can also be used in mud pumps.

40. What is the number of blades of the centrifugal pump impeller?

A: The number of blades of the centrifugal pump impeller is usually 6~8 pieces. For the liquid centrifugal pump that transports impurities, the number of blades is the largest, which is as small as 2~4 pieces, and the shape of the blade also changes significantly. The diameter of the pump, the flow rate is reduced, the more the blades, the more the number of revolutions exceeds, and the fewer the number of blades.

41. What kind of material is the impeller of a centrifugal pump made of?

A: Commonly used materials are: gray cast iron, acid-resistant ferrosilicon, alkali-resistant aluminum cast iron, chromium-based stainless steel, chromium-manganese-nitrogen series acid-resistant cast steel, chromium-manganese series alkali-resistant cast steel, hard lead, nickel-containing acid-resistant cast steel, Cr18, Copper alloy, aluminum-magnesium alloy, etc.

42, What are the material requirements for manufacturing centrifugal pump impellers?

A: There is sufficient strength and rigidity, good welding or machining performance. For chemical pumps, it also needs to have resistance to liquid medium corrosion and cavitation.

43, What is the role of the pump body of the centrifugal pump?

A: The liquid gradually reduces the speed in the channel, which converts part of the kinetic energy into static pressure energy, which not only increases the pressure of the liquid, but also reduces the energy loss inside the pump body caused by the passage being too large. Therefore, the pump body collects liquid as both the outer casing of the pump, and it is itself an energy conversion device.

44. What are the common structures of the pump body?

A: The pump body is the center of the pump structure, also called the volute or pump casing. The forms are: horizontal split type, vertical split type, inclined split type, simplified type.

45, According to the support form of the pump casing can be divided into several?

A: According to the support form of the pump casing, it can be divided into standard support type, central support type, cantilever type, pipeline type and hanging type.

46. Why does the centrifugal pump generate gravity?

A: Because the pressure at the suction and discharge ports is not equal, the hydraulic pressure at the ends of the impeller, which is usually not completely symmetrical, is not equal, which creates a potential force.

47, What is the hazard of the centrifugal pump for the first time?

A: Due to the existence of unbalanced balance force, the work load of the thrust bearing is aggravated, which is unfavorable for the work that will go out. At the same time, the insertion force causes the whole rotor of the pump to sway to the suction port, causing vibration to cause the impeller inlet and the seal ring to occur. Friction, when it is serious, makes the one not work properly.

48, How to eliminate the first force of the centrifugal pump?

Open balance hole;

Add a balance tube;

Install balance blades;

Using a double suction impeller;

The impeller is symmetrically arranged;

Use a balance disc.

49, What is the shaft seal?

A: The seal between the rotating pump shaft and the fixed pump casing is called a shaft seal.

50, What is the role of the shaft seal?

A: The function of the shaft seal is to prevent high-pressure liquid from leaking out from the pump along the shaft, or the outside air is infiltrated along the shaft. For the shaft seal of the centrifugal pump, it is a dynamic seal.

51, What is the packing seal?

A: The packing seal is a traditional gland seal. It generates a pre-tightening force by the gland, thereby pressing the packing, and the shrinking packing is tightly pressed on the sealing surface (the outer surface of the shaft and the sealing cavity) to generate a sealing radial force for axial sealing action.

52, What are the characteristics of the packing seal?

A: The packing seal can be applied to large stuffing boxes and heavy loads. The structure is simple, the operation and maintenance are convenient, and the cost is low. The disadvantage is that the power consumption is large, the sealing reliability is poor, and the shaft seal is worn during use.

53, What is the material used for packing?

Synthetic fiber plus polytetrafluoroethylene;

Synthetic fiber

Fiber plus black lead;

PTFE

Hemp PTFE;

Asbestos immersed in PTFE;

Asbestos graphite

Asbestos plus black lead;

Cotton plus natural rubber.

54, What is a mechanical seal?

A: The mechanical seal, also called the axial seal, is a shaft seal device for a rotating machine. It refers to the action of the liquid pressure and the compensating mechanism's elastic force (or magnetic force) and the auxiliary seal by at least one pair of ends perpendicular to the rotating axial direction. A device for preventing fluid leakage, which is formed by holding and attaching relative sliding.

55, Mechanical seal of the moving ring, static ring, sealing ring, the working state of the elastic components?

Dynamic seal ring (also known as moving ring);

Static seal ring (also known as static ring);

Static ring seal ring;

Moving ring seal

Elastic element.

56, What are the conditions for the selection of commonly used fillers?

A: In the chemical plant, the filler of the pump filler should meet the following four requirements: the filler can resist the corrosion of the medium; the filler has a certain strength; the filler has certain homogeneity and plasticity; the filler can adapt to the temperature of the medium (high temperature or low temperature).

57, What is a mechanical seal?

58, What is the role of mechanical seal?

A: Its main function is to change the leaky tandem seal to an end seal that is more difficult to leak.

59. What are the parts of the mechanical seal?

A: The mechanical seal includes a seal ring, a static seal ring, a spring load device and a static sealing element.

60, What are the advantages of mechanical seals?

Reliable sealing;

Long life;

Friction power consumption is small;

The vibration bearing shaft of the rotating shaft is insensitive to the deflection of the housing hole;

Wide range of applications.

61, What are the disadvantages of mechanical seals?

A: The mechanical seal structure is complicated to manufacture, the dynamic and static end face processing requirements are high, the friction pair load other component materials are not easy to match, and at the same time, certain installation technology is required, and the cost is high.

62, Why should the mechanical seal be washed?

A: The sealing medium in the sealed cavity contains particles and impurities, which must be re-returned. Otherwise, the precipitation of crystals, the deposition of particles and impurities will cause the mechanical seal to lose its floating and the spring will fail. More serious is the particles, impurities entering the friction pair will aggravate the friction and wear, and the rapid destruction of the child's mechanical seal.

63, How many methods of mechanical seal flushing?

Self-rinsing;

External flushing;

Back flush.

64, Sealing performance of the mechanical seal is related to what is doping?

A: The sealing performance of mechanical seals is related to the material of each component, especially the material of the end seal (friction pair), and the material of the auxiliary seal material.

65. What is the material used for the end seal friction pair?

A: The materials used for the end seal friction pair are graphite, ceramic, hardfacing hard alloy, tungsten carbide alloy.

66. What are the materials used for the auxiliary seals?

A: The material used for the auxiliary seal is rubber, PTFE.

67. What are the materials used for the elastic components?

A: The materials used for the elastic components are spring material and bellows material.

68. What are the faults on the parts of the mechanical seal?

Failure of the sealing end face: wear, hot crack, deformation, damage;

Spring failure: slack, breakage and corrosion;

Auxiliary seal failure: assembly failures are lost, cracked, bumped, curled and twisted; non-assembled faults are deformed, hardened, cracked and deteriorated.

69. What is the function of the shaft of the centrifugal pump?

A: The function of the pump shaft is to support the rotating parts such as the impeller, and drive the impeller to make the high-speed rotating screen to transmit the driving power components in the determined working position.

70, What is a sliding bearing?

A: Bearings that use the sliding motion of the shaft and the bearing to bear the load are called plain bearings.

71, Sliding bearings can be divided into several categories?

A: According to the principle of oil film formation between the two opposite moving surfaces of the sliding bearing, it can be divided into fluid dynamic pressure lubrication bearing (also known as dynamic pressure bearing) and hydrostatic bearing (also known as hydrostatic bearing).

72. What are the commonly used bearing materials?

Cast iron;

Bearing alloy

Copper alloy

Aluminum alloy

Ceramic metal

Graphite;

Other non-metallic materials: rubber, phenolic tape, nylon.

73. What is a rolling bearing?

A: Bearings that use rolling friction to withstand loads are called rolling bearings.

74. What are the components of the rolling bearing?

Inner ring (also known as inner or inner ring);

Outer ring (also known as outer or outer ring);

Rolling body (steel ball or roller);

Cage (also known as retainer and isolator).

75. What is the role of the inner ring of the rolling bearing?

A: The inner ring (also known as the inner or inner ring) is usually fixed to the journal and the inner ring rotates with the shaft. The outer surface of the inner ring has a groove for rolling a steel ball or a roller, which is called an inner groove or an inner race.

76. What is the role of the outer ring of the rolling bearing?

A: The outer ring (also known as the outer or outer ring) is usually fixed to the housing of the bearing or the machine to support the rolling elements. The outer surface of the outer ring has grooves for rolling steel balls or rollers, called outer grooves or outer races.

77. What is the role of rolling bearing rolling elements?

A: Each set of rolling elements (steel balls or rollers) is equipped with one or several sets of rolling elements, which are installed between the inner ring and the outer ring to play the role of rolling and transmitting force. The rolling element is a load-bearing part whose shape, size and number determine the bearing's ability to withstand loads and high-speed operation.

78. What is the role of the rolling bearing cage?

A: The cage (also known as the retainer and the isolator) separates the rolling elements in the bearing evenly, so that each rolling element rolls normally between the inner ring and the outer ring. In addition, the cage has the function of guiding the rolling elements, improving the lubrication conditions inside the bearing, and preventing the rolling elements from falling off.

79. What are the basic requirements for steel for rolling bearings?

High contact fatigue strength

Good wear resistance

Hardness generally reaches HRC61~65

Good rust resistance

Good processing performance

80, What is the clearance?

A: The so-called rolling bearing clearance is the maximum amount of movement of a ferrule in the radial or axial direction.

Chemical Centrifugal Pump FAQ (2-2)