Does the water pump experience cavitation at any operating point?
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Location of pressure gauges: The inlet pressure gauge is located at the pump’s inlet for residue removal; the main pipe has a diameter of DN1600. The inlet eccentric elbow has dimensions of DN1600mm*1000mm*1560mm (length). The outlet pressure gauge is situated at the center of one side of the main pipe. Export concentric reducers 1400mm*800*mm*1138mm (length). I. Data before operation: Inlet pressure gauge reading: 0.03 MPa; elevation: 1150 mm. Outlet pressure gauge reading: 0.046 MPa; elevation: 1650 mm. II. Data after stable operation: The valve on the recirculation pipeline is closed, and the outlet valve is gradually opened. After the outlet valve was fully opened and stabilization was achieved: Inlet pressure gauge reading: 0 MPa, with fluctuations between 0 and 1 MPa; Outlet pressure gauge reading: 0.58 MPa; Main pipe pressure: 0.57 MPa. NDE vibration levels: 5 mm/s vertically, 6.3 mm/s horizontally, and 5 mm/s axially. DE vibration levels: 4.6 mm/s vertically, 4.7 mm/s horizontally, and 4.8 mm/s axially. Turbine speed: 5000 r/min; Gearbox speed: 595 r/min. III. Abnormal conditions observed: 1. Cavitation occurred in the pump, accompanied by very high noise and vibration in the pump chamber. 2. To address the cavitation caused by excessive flow, adjustments were made to the outlet valve in order to control the flow rate; cavitation would persist as long as the outlet valve was not completely closed. What could be the possible reasons for this?
The rated cavitation head of the water pump is 6.7 meters, while the actual cavitation head should be 8.9 meters. The water level in the inlet tank is 6.7 meters, with the liquid surface being 3 meters away from the center line. Why is cavitation present under any operating conditions? Nothing went wrong during the factory testing: Q:Q:Q:Q:Q:'(
How do you know that the actual cavitation head of the pump is 8.9 meters, rather than the rated 6.7 meters? What is the flow rate of the pump?
The center height of this pump is 6.7 - 3 = 3.7 meters, is it on the second floor?
There was no observation on this, but the pipe bends downward after reaching the pool
The factory test report indicates a net positive suction head under rated operating conditions that is different from the value indicated on the nameplate; the center line is at a height of 1.5 meters above the ground, as the center line is located below a bend in the tank, with a flow rate of 15,800 and a head of 58
What is the net positive suction head at factory testing?
As the title suggests, why do you say it’s “cavitation”? Let me guess your question. Your problem is likely overcurrent after starting the pump, with pressure not reaching the required level. The problem lies in the operation. The steps to start the pump are as follows: First, ensure that the pressure before the pump meets the operating conditions; then open the pump inlet valve fully and close the pump outlet valve. After venting the air from the pump using the vent valve, close it. Start the pump; once the pump pressure exceeds the design value, gradually increase it while ensuring that the outlet pressure of the pump remains at or above the design value. The outlet valve is stopped from opening further until the pressure slightly drops and the current reaches the rated value; this position becomes the subsequent pump operation setting. Then it’s a matter of waiting, waiting for the system to reach its full load (design pressure); as for how users utilize the allocated resources, that is a matter for the users themselves. Your adjustment amount is determined by using the outlet valve to control the current. If what I’m guessing is true, then I’d like to say, regarding issues at the scene: only discuss the issues that occur on site; do not submit opinions that are merely personal interpretations. Just like with the pump problem, you say cavitation is one issue, but what exactly is wrong with the equipment? Is cavitation the reason you mentioned? If not, wouldn’t that be leading everyone down a wrong path? With all due respect.
Based on the specified net positive suction head, the suction lift is 3.13 m; with the water level 3 m above the pump’s center, this is clearly not sufficient