Time： 2016/1/23 14:00:32  Hits： 1285

The pump foundation knowledge is introduced

   12 - flow (m3 / h) single head (M) with 15 -

   200 qj20-108/8 - said the base 200 QJ - 200-20 - submersible pump flow 20 m3 / h - 108 head 108 m 8 - series 8

   Basic structure of the pump, motor, coupling, pump head (body) and stand (horizontal).

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

   The fresh water pump, it is necessary NPSH (M) parameters is very important, especially when used in suction type water supply equipment.

   For submersible pump, rated current (A) parameters is very important, especially when used in frequency conversion water supply equipment.

   Main parameters of the motor: the motor power (KW), speed (r/min), rated voltage (V), rated current (A).

   Coupling pump head (_) horizontal base

   What is flow? With what letter? In several units? How to conversion? How to convert to weight and formula?

   Answer: the pump discharge volume of liquid flow rate, flow with Q, said units: cubic meters/hour (m3 / h), litres per second (l/s), l/s = 3.6 m3 / h = 0.06 m3 / min = 60 l/min

 G = Q rho G for weight rho for liquid proportion

  Example: a pump flow 50 m3 / h, o pumping weight per hour? The proportion of water rho is 1000 kg/m3.

   Solution: G = Q rho = 50 x 1000 (m3 / h · kg/m3) = 50000 kg/h = 50 t/h

   What is a lift? With what letter? What unit of measurement? And conversion and formula of pressure?

   Answer: unit of energy gained by the weight of the liquid through the pump head. Pump lift, including suction approximation for the pump outlet and inlet pressure difference. Head with H said, the unit is meter (m). The pressure of the pump with P said, the unit for the Mpa (Mpa), H = P/rho. If P is 1 kg/cm2, is H = (LKG/cm2)/(1000 kg/m3) = (1 kg/cm2)/H (1000 kg/m3) = (10000 kg/m2) / 1000 kg/m3 = 10 m

 1 mpa = 10 kg/m2, c H = (P2, P1)/rho (P2 = outlet pressure P1 = inlet pressure)

    What is the efficiency of the pump? The formula?

    Answer: the effective power of the pump and the ratio of the shaft power. Eta = Pe/P

 Usually refers to the input power of pump power, the power of the prime mover to the pump shaft, so it is also called shaft power, expressed in P.

 Effective power: pump lift and the product of the mass flow rate and the acceleration of gravity.

 Pe = QH (W) or Pe = gamma rho g QH / 1000 (KW)

 Rho, pump the liquid density (kg/m3)

 Gamma: pump liquid severe gamma rho = g (N/m3)

 G: gravity acceleration (m/s)

 Mass flow Qm = rho Q (t/h or kg/s)

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

    Answer: according to the work performance parameters of the pump water pump design, and achieve the best performance, as the rating of the pump performance parameters, usually refers to product catalog or samples as specified by the parameter values.

 Such as: 50-125 flow 12.5 m3 / h for the rated flow, lift 20 m for rated head, speed 2900 r/min to rated speed

    What call NPSH? What is a suction? Each unit of measurement said letters?

    Answer: at the inlet of the pump the liquid in the impeller at work because of a certain vacuum pressure will produce gas, evaporation of bubbles in the liquid particle collision movement, the impeller of metal surface erosion, undermining the impeller of metal, at this time Vacuum pressure is called vaporization pressure, NPSH refers to the pump suction unit weight liquid has more than vaporization pressure at the entrance of surplus energy. Unit, rice (NPSH) r. Suction is the necessary NPSH Δ h: namely allow liquid absorption of vacuum pump, which allows the installation height of pump, unit from rice.

= standard atmospheric pressure suction (10.33 m) - NPSH - security amount (0.5 meters)

 Standard atmospheric pressure can vacuum pipeline height 10.33 meters.

    For example: a pump NPSH required is 4.0 meters, o Δ suction h?

 Solution: Δ h = 10.33-4.0-0.5 = 5.83 m

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

    Answer: usually called said the curve of the relationship between the main performance parameters of the centrifugal pump performance curve or characteristic curve, in essence, a centrifugal pump performance curve is the law of motion of the liquid in the pump in the external form, by the measured. Characteristic curve include: flow (Q - H) - the head curve, traffic - efficiency curve (Q - eta), flow rate (Q - N) - power curve, traffic - NPSH curve - (NPSH) r (Q), the performance curve is made with pump flow of arbitrary point, can find a set of the curve and its relative lift, power, efficiency and cavitation surplus value, a set of parameters called work status, referred to as "condition or conditions, the highest efficiency point centrifugal pump condition known as the best conditions of points, the best point as design point in general. Generally rated parameters of centrifugal pump design point and best point collocated or close. In practice to choose interval running efficiency, saving energy, and to keep the pump to work properly, so understanding the performance parameters of the pump is quite important.

     What is the full performance of the pump test bed?

     Answer: by precision instruments accurate test of pump out all the performance parameters of the equipment performance test bed for the whole. The national standard for class B precision. Flow with precision worm gear flowmeter measurement, head precision pressure gauge is used to test. With precision suction vacuum gauge measurement. Power precision shaft power machine is used to test. Speed tachometer is used to test. Efficiency according to the measured values: n = rQ102 calculation.