Thread Content
This post was last edited by 3983596_FPPZ on 2019-5-12 at 13:45. Thursday (2019.5.2): https://bbs.hcbbs.com/thread-2691043-1-1.html 1. For pumps used for normal seawater transportation, the flow-through components can be made of 304 material (incorrect)； 2. Non-destructive testing is commonly used to detect internal defects in the material structure of critical components, such as cast pressure-bearing parts, forged shafts, and welds in pressure pipelines (correct). Friday (2019.5.3) https://bbs.hcbbs.com/thread-2691686-1-1.html 1. Fill in the blank: Without considering the effect of temperature, for the same open-loop system, the NPSHA of a system installed in a highland area is (smaller) than that of a system installed in a coastal area ； 2. Judgment: In a suction tank, the check valve installed on the pump inlet pipeline to prevent backflow is a one-way valve (Correct). Saturday (2019.5.4) https://bbs.hcbbs.com/thread-2691979-1-1.html 1. Since gases have poor electrical conductivity or are non-conductive, electromagnetic flowmeters cannot be used to measure their flow rate (Correct) ； 2. Whether the pumps are connected in series or in parallel, it will result in an increase in the device’s resistance (True). Sunday (2019.5.5) https://bbs.hcbbs.com/thread-2692406-1-1.html 1. As temperature sensing elements as well, thermoresistors (such as PT100) can measure higher temperatures than thermocouples (False) ； 2. When a non-constant-speed centrifugal pump experiences cavitation, its speed will increase slightly (correct). Monday (2019.5.6) https://bbs.hcbbs.com/thread-2693217-1-1.html 1. The fundamental reason for cavitation in a pump is that its NPSHR is close to or even greater than the system’s NPSHA ； (Yes) 2. High-power motors are often high-voltage motors, and this is done to reduce the operating current of the motor and thereby lessen the load on the power grid. (Wrong) (Reducing the current is correct, but it does not reduce the load on the power grid.) Tuesday (2019.5.7) https://bbs.hcbbs.com/thread-2694603-1-1.html 1. Defects in the pump body can be corrected through professional welding, allowing the pump to be exempt from pressure tests (Wrong) ； 2. After the expiration date of the pressure gauge calibration certificate, it can still be used normally within that month, but the calibration must be completed within the same month (incorrect). Wednesday (2019.5.8) https://bbs.hcbbs.com/thread-2695650-1-1.html 1. Among the following data related to the casting of impellers for centrifugal pumps, which factors need to be given special consideration during impeller design based on casting capabilities (BCD). A. Rotor diameter B. Blade thickness C. Flow channel width D. Degree of blade twist E. Inlet diameter Thursday (2019.5.9) https://bbs.hcbbs.com/thread-2696671-1-1.html 1. Shims should be used to ensure the levelness of the equipment base; they must be firmly placed beneath the base frame and distributed evenly around it (Incorrect – shims should be placed near the foundation bolt holes) ； 2. The highest efficiency point of a centrifugal pump can be away from the flow rate corresponding to its rated operating conditions, but this requires the customer’s approval (Correct; it is common during selection to find no suitable pump model, forcing a deviation from the designed parameters, but this must be approved by the customer). Friday (2019.5.10) https://bbs.hcbbs.com/thread-2697579-1-1.html 1. Fill-in-the-blank question: According to the standard GB/T3216-2005 Rotary Positive Displacement Pumps – Hydrodynamic Performance Acceptance Tests, Grades 1, 2, and 3, during the factory suction head margin test, the required suction head margin at a drop in head of (3)% is taken as the pump’s suction head margin value ； 2. Single-choice question: If, when ordering pump products, it is required to comply only with the standard GB/T3215 \"Centrifugal Pumps for the Petroleum, Heavy Chemicals, and Natural Gas Industries\", then the basis for determining whether the pump’s flow rate and head meet the specified requirements during the factory performance tests is (A). A、GB/T3215 B、GB3216 C、API610 D、Determined by the pump manufacturer itself. Saturday (2019.5.11) https://bbs.hcbbs.com/thread-2698050-1-1.html 1、For rotating mechanical equipment, it is often necessary to turn the shaft before starting it or when it is not in use for a period of time. Regarding the angle at which the shaft should be turned, the correct principle is (C: it should be an odd multiple of 180°, so that a reversal of direction occurs) ； A 360°n B 180°n C 180°(2n+1) D 360°(2n+1) E Any angle. 2. In a BB4 multi-stage pump (segmented multi-stage pump), if the number of impeller blades is 6, then the appropriate number of blades on the guide vanes located on the outside of the impeller is C (the two numbers of blades should be coprime to avoid vibrations resulting therefrom). A 3 pieces B 6 pieces C 7 pieces D 12 pieces. Wishing all mothers in the world a happy holiday! ! !