【Daily Question: Pump Equipment】Weekly Summary May 26, 2019

Thread Content

Monday (2019.5.20) https://bbs.hcbbs.com/thread-2706904-1-1.html 1. Some flow pumps (also known as tangent pumps) are typical pump designs that convert the kinetic energy of liquids into pressure energy (correct)； 2. In most cases, the mechanical seals at the high-pressure and low-pressure ends of a multi-stage pump cannot be used interchangeably as a whole (there is some debate: pumps with large thread locks, requirements regarding the direction of the springs, significant differences in pressure levels between the two ends, or large differences in shaft diameter between the two ends cannot be interchanged; other pumps can be interchanged). Tuesday (2019.5.21) https://bbs.hcbbs.com/thread-2708469-1-1.html Discussion topic: For pump stations A, B, and C under the same operating conditions, with the same medium and located in the same place, where one pump is in use while two are in standby mode, three identical single-stage centrifugal pumps were ordered. An additional impeller was ordered for each pump as a spare part. The manufacturer conducted factory tests on each complete pump before shipping it once the tests were successful. Please discuss whether the outer diameters of these 6 impellers should be the same, and whether they can be used interchangeably Tip: Impeller castings from the same batch can vary, which leads to differences in hydraulic performance. Combined with the acceptance criteria used during testing, this results in slight variations in impeller diameter. It is recommended to label the components properly; generally, it is not advisable to interchange them arbitrarily. Wednesday (2019.5.22) https://bbs.hcbbs.com/thread-2709435-1-1.html 1. The inlet diameter of the centrifugal pump impeller must be the same as the inlet diameter of the pump casing (False) ； 2. The inlet diameter of the pump body must always be larger than the outlet diameter (False). Thursday (2019.5.23) https://bbs.hcbbs.com/thread-2710247-1-1.html 1. The standard width of a flat key with a shaft diameter of φ42mm should be (12) mm; 2. The gauge pressure at the inlet of the centrifugal pump is 0.3 MPa, the head is 125 m, the inlet and outlet have the same diameter, and the specific gravity of the fluid is 0.8. Without considering other factors such as viscosity or the height difference between the pump inlet and outlet, the gauge pressure at the pump outlet should be (1.28 or 1.3) MPa. Friday (2019.5.24) https://bbs.hcbbs.com/thread-2711623-1-1.html 1. Given that the grid frequency is 50Hz, the motor has 4 poles, and its slip rate is 2.8%, then the motor’s speed at this time is (50x60/2=1500; 1500x(1-2.8%)=1458) rpm ； 2. The diameter of the pump inlet pipe is DN100, and the flow rate is 80 m3/h; therefore, the average flow velocity of the fluid in the inlet pipe is (4x80/(36x3.14159)) = 2.83 m/s. On Saturday (May 25, 2019), https://bbs.hcbbs.com/thread-2712356-1-1.html The units used to measure pump vibration are (amplitude in mm), (vibration velocity in mm/s), and (vibration acceleration in mm/s2); among these, mm/s is the most commonly used unit. Happy weekend! ! !