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1. Common standard throttling devices include (orifice plates), (nozzles), and (Venturi tubes). 2. Common non-standard throttling devices include (double orifice plates), (notched orifice plates), (1/4 circle nozzles), and (Venturi nozzles). 3. The common pressure tapping methods for orifice plates include (corner tapping) and (flange tapping); other methods include (theoretical tapping), (radial distance tapping), and (pipe connection tapping). 4. The standard orifice plate flange pressure extraction method involves a distance of (25.4±0.8) mm between the centers of the pressure extraction holes on the upstream and downstream sides, as well as between these holes and the front and rear surfaces of the orifice plate; this is also known as 1-inch flange pressure extraction. 5. The operating voltage range for the 1151 transmitter is from (12) VDC to (45) VDC, with a load ranging from (0) ohms to (1650) ohms. 6. The measurement range of the 1151DP4E transmitter is from (0～6.2) to (0～37.4) Kpa. 7. The maximum positive drift of the 7.1151 differential pressure transmitter is (500%), and the maximum negative drift is (600%). 8. The fluid velocity within a pipe is, under normal conditions, highest at the (centerline of the pipe), and zero at the (pipe wall). 9. If the (Reynolds number) is the same, the flow of the fluid is similar. 10. When the fluid filling the pipe flows through a throttling device, the flow stream undergoes (local contraction) at the (throttle), which results in an increase in (flow velocity) and a decrease in (static pressure). 11. The 11.1151 differential pressure transmitter uses a variable capacitor as the sensing element; when the differential pressure increases, the measuring diaphragm moves, resulting in an increase in capacitance on the low-pressure side and a decrease in capacitance on the high-pressure side. 12. When the 11.1151 differential pressure transmitter is used within its minimum calibration range, the maximum load shift is (600%) of the range, while the maximum positive shift is (500%). If it is used within its maximum calibration range, the maximum negative shift is (100%), and the positive shift is (0%). 13. The accuracy of the 1151 differential pressure transmitter is (±0.2%) and (±0.25%). Note: The large-differential-pressure transmitter has a precision of ±0.25%. 14. Common units for flow rate are as follows: volumetric flow rate is expressed in (m3/h) and (t/h), while mass flow rate is expressed in (kg/h) and (t/h). The volumetric flow rate of gases under standard conditions is given in (Nm3/h). 15. When using a orifice plate flow meter to measure steam flow, the density of the steam is assumed to be 4.0 kg/m3 during design, whereas the actual density in operation is 3 kg/m3; as a result, the actual indicated flow rate is (0.866) times the designed flow rate. 16. When measuring the flow rate of gaseous ammonia using an orifice plate flow meter, with a design pressure of 0.2 MPa (gauge) and a temperature of 20°C, while the actual pressure is 0.15 MPa (gauge) and the temperature is 30°C, the actual indicated flow rate is (0.897) times the design flow rate. 17. The required length of the straight pipe section before the throttle orifice plate is generally (10)D, while that behind the orifice plate is usually (5)D. For accurate measurements, it is advisable that the straight pipe section before the orifice plate be (30–50)D, especially when there is a pump or control valve in front of the orifice plate. 18. To make the flow coefficient α of the orifice flow meter tend to a constant value, the Reynolds number of the fluid should be greater than (the critical Reynolds number). 19. Among the technical requirements for orifice plate manufacturing, the upstream surface should be perpendicular to the centerline of the orifice plate, and there should be no visible defects; the upstream and downstream surfaces should be parallel to each other, and the upstream inlet edge should be sharp, without any protrusions or defects. 20. For which type of fluid is the pressure measurement location shown in the diagram correct? (A) A. Gas B. Liquid C. Vapor D. High-viscosity fluid E. Sedimenting fluid Principle: When measuring gas, in order to allow any small amount of condensate present in the gas to flow back smoothly into the process pipeline without entering the measurement lines and instruments, the pressure tap should be located in the upper part of the pipeline, namely at point 1 in the diagram. When measuring liquids, in order to allow the small amount of gas that forms within the liquid to return smoothly to the process pipeline without entering the measurement piping and instruments, the pressure tapping point should be positioned at an angle of 0–45 degrees below the horizontal centerline of the pipeline, as shown at position 2 in the diagram. For steam media, it is necessary to maintain a steady amount of condensate in the measurement pipeline, while also preventing solid materials at the bottom of the process pipeline from entering the measurement pipeline and instruments. The pressure tapping point should be located at an angle of 0–45 degrees above the horizontal centerline of the pipeline, as indicated at position 3 in the diagram. 21. For differential pressure flowmeters filled with isolation fluid, what should be noted when opening and closing the balance valve? What’s the logic? Answer: For differential pressure flowmeters using isolation fluid, before turning them on – that is, before opening the orifice pressure-taking valve – it is necessary to first close the balance valve to prevent the isolation fluid from being washed away. When shutting them down, the pressure-taking valve must be closed first, after which the balance valve can be opened to bring the meter back to an equilibrium state. When fluid is flowing in the process pipeline, a pressure difference exists on both sides of the throttling device. In instruments filled with isolation fluid, if both pressure-taking valves are open, the situation is similar to that in a \"U\"-tube: the liquid cannot flow from one end to the other; pressure cannot be applied at the positive-pressure end, nor can fluid be drawn out from the negative-pressure end, which ensures that the liquid in the \"U\"-tube does not escape. Therefore, for the differential pressure gauge used to monitor the flow rate of the isolation fluid, it is important to pay attention to the relative position of the balance valve, and that’s exactly why. 22. What is the static pressure error of a differential pressure transmitter? Answer: When the same pressure is applied to both the positive and negative chambers of a differential pressure transmitter, the output zero point of the transmitter shifts. The magnitude of this shift changes as the static pressure increases; this error caused by static pressure is known as static pressure error. 23. Describe the various methods for taking pressure readings at a throttle device Answer: 1. Corner tapping, 2. Flange tapping, 3. Theoretical tapping, 4. Radial distance tapping, 5. Pipe connection tapping. 24. When using a differential pressure transmitter to measure flow rate, under what conditions is it necessary to install a seal? How to install? Answer: When the medium being measured is a corrosive gas or liquid, it is necessary to install a seal in order to protect the diaphragm box and measurement conduit of the differential pressure transmitter from corrosion ； When the medium under test is a viscous medium, seals also need to be installed to ensure accurate measurement. The connection port of the capsule to the throttle element is the \"inlet\", while the port to the measurement catheter is the \"outlet\“. When the density of the medium being measured is lower than that of the filling fluid, the capsule should move \"upward in and downward out\"; whereas when the density of the medium being measured is higher than that of the filling fluid, the capsule should move \"downward in and upward out\“.