Keywords: Centrifugal pump Pump characteristic curve Impeller cutting Non-standard impeller method
1 Introduction
Centrifugal pump in pumping the liquid process, you need to consume a certain amount of energy. In the actual use of centrifugal pumps, often due to various reasons, part of the centrifugal pump actual operating conditions deviate from the high efficiency zone, resulting in excessive energy consumption of centrifugal pumps and operating conditions are not ideal. In order to improve this phenomenon, we must make the necessary technological transformation to the centrifugal pump and further improve the operation efficiency of the centrifugal pump under the premise of meeting the water quantity and lift required by the water supply system.
2, pump reform project put forward
Huizhou City Water Works Corporation, a water pumping station pumping station designed to take the scale of 600,000 m 3 / d, the first phase of the completion of 200,000 m 3 / d, suction pumping station water intake equipment are two 44SAP-14 centrifugal water pump, the nameplate Parameters for Q = 9000m 3 / h, H = 28.5m, n = 425r / min, η = 88%, the specific speed of 140 r / min, impeller diameter ф = 1110mm. After two pumps run 3000 hours, the pump impeller has more obvious cavitation damage, pump vibration increased, the bearing temperature is not normal. The unsatisfactory performance of the pump is mainly due to the selection of the pump is based on the long-term 600,000 m 3 / d, so the selected head is higher than the actual head required for the first phase, resulting in pump operating conditions deviate from the high-efficiency zone, in Low head, low efficiency and poor cavitation performance of the regional operation. June 6, 2002, the actual operating point of the pump (Q, H) is (11800,18) (Z point in Figure 1), the operating efficiency is only η, = 75% or so. In order to solve the above problems, in July 2002, Huizhou City Water Corporation decided to conduct its own right transformation.
3, the centrifugal pump to determine the transformation program and the transformation effect
Option One: The replacement of a new pump is the most thorough solution. The new pump can be selected 44SAP-25 centrifugal pump, the pump design parameters: Q = 10800m 3 / h, H = 20m, n = 425r / min, η = 90%. Although the pump can be used to replace the original pump motor, but because of the high cost of the program, and time-consuming and laborious, inevitably affect the water plant production, it is not used.
Scenario 2: When the pump head is too high, the cutting impeller diameter is a way to adjust the performance of the pump to reduce the power consumption of the pump simple and easy way. Considering the first phase of the plant's water supply and the matching of the two pumping stations, the pump should be operated at QB = 9700m 3 / h and HB = 18m after cutting by the impeller, ie at point B in Figure II. Through the point B for cutting parabola H '= K (Q') 2 , and the original water pump curve QH intersection at point A. Point A is to meet the cutting law requirements of the corresponding point B conditions: QA = 10900m3 / h, HA = 22.7m.
Impeller after cutting, the performance parameters Q, H changes and the wheel diameter D after cutting the following relationship: QB / QA = DB / DA, HB / HA = (DB / DA) 2 where DA is the original impeller diameter, DB The diameter of the impeller after cutting. Substituting A and B into the above formula, DB / DA = 89%, that is, the cutting capacity of the original impeller is 11%, and the critical cutting speed is 14% of the maximum allowable cutting speed of the impeller at the specific rotation speed of 140r / min. In addition, according to the law of cutting, within the cutting limit, the cutting parabola H '= K (Q') 2 is also called the equivalent efficiency line. That is, the corresponding efficiencies at two points A and B on the curve can be regarded as equal. Because the efficiency at point A is 81%, it is in the low efficiency zone of the pump characteristic QH curve, and the operating efficiency at point B after the impeller cutting will also be in the low efficiency operating zone (see Figure 1). The program to improve the efficiency of the pump is not running, it is not used.
Program three: The non-standard impeller method of the pump impeller transformation, that is, design and manufacture of non-standard impeller and the assembly of the original pump body to run in order to effectively change the pump performance parameters. According to this idea, can over the 44SAP-25-type pump impeller cutting and parameter integration, so that it meets the requirements of 44SAP-14-type pump. At the same time, the specific speed of the original pump is increased from 140 r / min to 250 r / min, so as to achieve the effect of reducing the lift and improving the operation efficiency of the modified pump. In November 2002, according to this plan, one of the pumps was remodeled. After the transformation of the 44SAP-14/25-type pump operating point QD = 9700m 3 / h, HD = 18m (point D) in the pump operating high efficiency area, the operating efficiency of about 88%. (Its pump characteristic curve shown in Figure 3)
44SAP-14-type pump after non-standard impeller transformation, the pump vibration was significantly reduced during operation, reduce noise, cavitation has been very well improved. The original pump supporting motor running current from the original 65.5A down to 59.5A, so that pumping station power consumption has dropped dramatically. To 200,000 tons of water a day to calculate, save the day after the transformation 9.6 × 200 = 1920 degrees, six months to save electricity up to 350,000 degrees. Before and after the pump energy consumption comparison is as follows:
4 Conclusion
In the inappropriate replacement of new pumps and cutting impeller case, the use of non-standard impeller method to transform the centrifugal pump, you can achieve the following results:
(1) The rated parameters can be re-determined according to actual needs, subject to the original pump parameters smaller restrictions;
(2) The new pump operating parameters can be more in line with the production needs after the renovation, the pump operating efficiency can be properly increased, and the energy saving effect after the renovation is remarkable.
(3) can be targeted to improve some of the pump's specific properties.
About the Author:
Jiang Naichang, Jin cone. Pumps and pump stations. China Building Industry Press. 1993 June third edition.
Rong Zhenhui (1975 -), male, Han, Bachelor of Engineering, engineer. In 1998 graduated from the Department of Civil Engineering, Hunan University, Hunan Water Supply and Drainage Professional, currently Huizhou City Water Corporation Jiangbei Waterworks director, responsible for waterworks production and technology research. Tel: Email:
Zhang Rong (1963-), male, Han nationality, Bachelor of Engineering, senior engineer of water supply and drainage, chief engineer of Huizhou Water Supply Company, has been engaged in urban water supply for more than 20 years and has rich experience in water supply design, construction and management. Tel:.
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