【Daily Question: Pump Equipment】Weekly Summary 2019.1.27
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Monday (2019.1.21) https://bbs.hcbbs.com/thread-2268702-1-1.html 1. In the chemical composition of steel, excessive levels of sulfur, phosphorus, and carbon can have harmful effects on the steel; therefore, their levels should be kept as low as possible. (Wrong) 2. There is an optimal range for the number of blades in a centrifugal pump’s impeller; too many or too few blades can result in suboptimal hydraulic performance. (Right) Tuesday (2019.1.22) https://bbs.hcbbs.com/thread-2270431-1-1.html 1. Pump components that are completely submerged in the fluid do not fall under the category of pressure-bearing components. (Wrong) 2. It is prohibited for anyone to stand near either side of the coupling when the pump is started. (Right) Wednesday (2019.1.23) https://bbs.hcbbs.com/thread-2271722-1-1.html 1. The new national standard designation for stainless steel 304 (0Cr18Ni9) is 06Cr19Ni10, which provides a more accurate description of its carbon content. (Right) 2. In welded connections between pipes and flanges, the strength of fillet welds is greater than that of butt welds. (Wrong) Thursday (2019.1.24) https://bbs.hcbbs.com/thread-2273117-1-1.html 1. When a centrifugal pump operates under pressure with its inlet and outlet valves closed, the pressure throughout the pump chamber is the same, equal to the pressure at the pump’s outlet. (Wrong) 2. In standard metric threads, except for those with the largest pitch, which are called coarse threads, all other threads are considered fine threads. (Right) Friday (2019.1.25) https://bbs.hcbbs.com/thread-2274373-1-1.html 1. The flow rate of the minimum flow return line connected to the outlet pipe is not included in the pump’s designed flow rate. (Right) 2. The inlet pressure of a single-stage cantilever centrifugal pump has no effect on the axial force balance of the pump. (Wrong) Saturday (2019.1.26) https://bbs.hcbbs.com/thread-2275444-1-1.html 1. As the flow rate of a centrifugal pump increases from zero to its maximum value, its vibration level also increases. (Wrong) 2. If a pressure gauge has an accuracy class of 1.6 and a range of 4.0 MPa, then the allowable pressure error for this gauge is: 4.0 x 1.6% = 0.064 MPa. (Right) Have a great weekend!
I have questions about the following statement; please indicate its source? 1. Pump components that are completely submerged in the medium do not fall under the category of pressure-bearing components (incorrect). According to API 610, 11th edition, section 3.43, pressure-bearing components refer to all flanges, sealing gaskets, sealing chambers, and associated connections, with the mechanical seal itself being excluded. According to this, pump components that are not immersed in the medium are not included; wear rings and impellers do not count either.
I also thought the same way when this SeaUser started asking questions – it was because our consideration was limited to the components inside the pump. But for example, the pump body of submersible pumps and the casing of submersed pumps are both submerged in the medium, yet both of them are pressure-bearing components. Considering this aspect of being submerged in the medium makes the problem more complicated: lol
The pump casings in the special situations mentioned by the original poster are all those where the internal pressure is greater than the external pressure, and should be considered pressure-bearing components. However, it is correct that components such as impellers and mouth rings, which are inevitably immersed in the process medium, do not belong to pressure-bearing parts.
That’s correct; the mouth ring, impeller, and impeller nut are all submerged in the medium, so they do not constitute pressure-bearing components