Pump basic knowledge introduction

Pump model meaning: If 40LG12-15 40 - Import and export diameter (mm) LG-high-rise building water pump (high speed)

12- Flow rate (m3 / h) 15-single-stage lift (M)

200QJ20-108 / 8 200 --- Said frame number 200 QJ --- Submersible pump 20- Flow 20m3 / h 108 --- Head 108M 8 --- Series 8

The basic composition of the pump: motor, coupling, pump head (body) and machine base (horizontal).

The main parameters of the pump are: flow, with Q said that the unit is M3 / H, L / S. Head, said H, the unit is M.

For clean water pumps, the necessary NPSH (M) parameters are important, especially for suction type water supply equipment.

Submersible pumps, rated current parameter (A) is very important, especially when used in frequency conversion water supply equipment.

Motor's main parameters: motor power (KW), speed (r / min), rated voltage (V), rated current (A).

Coupling pump head (body _) horizontal base

What is the traffic? What alphabet is used? How many units of measurement? How to convert? How to convert into weight and formula?

A: The volume of liquid discharged by the pump per unit time is called the flow rate, and the flow rate is expressed by Q. The unit of measurement is: m3 / h, l / s, L / s = 3.6 m3 / h = m3 / min = 60 L / min

G = Qρ G is the weight ρ is the liquid specific gravity

Example: A pump flow of 50 m3 / h, when seeking pumping weight per hour? The specific gravity of water ρ is 1000 kg / m3.

Solution: G = Qp = 50 × 1000 (m3 / h · kg / m3) = 50000kg / h = 50t / h

What is the lift? What alphabet is used? What unit of measurement? And pressure conversion and formula?

A: The weight per unit weight of liquid obtained by the pump is called lift. Pump head including the suction stroke, approximately pump outlet and inlet pressure difference. Head with H said, in meters (m). The pressure of the pump is expressed by P in units of Mpa (MPa), H = P / ρ, H = 1kg / cm2 / 1000kg / m3 if P is 1kg / (1000 kg / m3) = (10000 kg / m2) / 1000 kg / m3 = 10m

1 Mpa = 10 kg / c m2, H = (P2-P1) / p (P2 = outlet pressure P1 = inlet pressure)

What is the efficiency of the pump? What is the formula?

A: The ratio of pump effective power to shaft power. η = Pe / P

Pump power usually refers to the input power, that is, the prime mover to the pump shaft power, it is also known as shaft power, with P said.

Effective power is: pump head and mass flow and acceleration of the product of gravity.

Pe = ρg QH (W) or Pe = γQH / 1000 (KW)

ρ: liquid density of the pump (kg / m3)

γ: Severe degree of liquid pumped by pump γ = ρg (N / m3)

g: Gravitational acceleration (m / s)

Mass flow Qm = ρQ (t / h or kg / s)

What is the rated flow, rated speed, rated head?

A: According to the pump performance parameters set pump performance design, and to achieve the best performance, as the pump rated performance parameters, usually refers to the product catalog or sample the specified parameter values.

Such as: 50-125 flow rate of 12.5 m3 / h for the rated flow head 20m rated head speed of 2900 rev / min is the rated speed

What is the NPSH? What is suction stroke? The respective units of measure that letters?

A: The pump at work at the impeller inlet at a certain vacuum pressure will produce vapors, vaporized bubbles in the impact of the liquid particle impact on the impeller and other metal surface erosion, and thus destroy the impeller and other metals, this time the vacuum Pressure is called vaporization pressure, NPSH refers to the pump intake at the unit weight of liquid excess energy than the vaporization pressure. Units marked with meters, with (NPSH) r. Suction stroke is required NPSH Δh: That is, the degree of vacuum that the pump allows liquid to be sucked in, that is, the allowable installation height of the pump, in meters.

Stroke = standard atmospheric pressure (10.33 meters) - NPSH - safe amount (0.5 meters)

Standard atmospheric pressure pipeline pressure can be 10.33 meters in height.

For example: a pump required NPSH is 4.0 meters, suction Δh?

Solution: Δh = 10.33-4.0-0.5 = 5.83 meters

What is the characteristic curve of the pump? Including several aspects? What is the role?

A: The curve representing the relationship between the main performance parameters is usually referred to as the performance curve or characteristic curve of the centrifugal pump. In essence, the performance curve of the centrifugal pump is an external manifestation of the movement of the liquid in the pump and is obtained by the actual measurement. The characteristic curves include: QH, Q-Q, QN, Q- (NPSH) r, and the performance curve is Pump any point of flow, can be found in the curve of a group of its head, power, efficiency and NPSH value, this group of parameters is called the working state, referred to as working conditions or conditions point, the centrifugal pump The most efficient point of the condition known as the best condition point, the best condition point is generally the design condition point. General centrifugal pump rated parameters that the design conditions point and the best conditions coincide or very close. Operating in the practice of selecting efficiency range, that is, energy conservation, but also to ensure the normal pump work, so understand the performance parameters of the pump is very important.

What is the pump's full performance test bench?

A: The equipment capable of accurately testing the full performance parameters of a pump with precision instruments is the full-performance test bench. National standards for the B-level accuracy. The flow rate is measured with a precision worm gear flowmeter and the head is measured with a precision pressure gauge. Suction with a precision vacuum gauge measurement. Power measured with a precision shaft power machine. Speed ​​with tachometer. Efficiency according to the measured value: n = rQ102 calculation.

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