【Questions about PID drawings】What are the requirements for the straight pipe section for flow regulation?
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Recently, I came across a PID diagram for measuring gas flow, which utilizes vortex flow meters, temperature and pressure compensation, as well as control valves. However, as can be seen from the diagram, there are many requirements for straight pipe sections, as shown below. Dear sea friends, please tell us what the function of each straight pipe section is ?
Straight pipe sections 1 and 2: These are the lengths of the straight pipe sections before and after the flow meter that are required. Straight pipe section 3: specifies the distance between the thermometer and the pressure sampling point. Straight pipe section 5: Specifies the distance between the thermometer and the control valve. Straight pipe section 4: Specifies the length of the flow meter.
Straight pipe sections 1 and 2 are requirements before and after the flow meter; that’s how it should be understood. For different types of flowmeters, are there requirements regarding the length of the straight sections before and after them? What is the reason for the distance between the straight pipe section 3 and the temperature and pressure sampling points? What are the impacts? ? Additionally, what is the impact of the length between the thermometer and the control valve in the straight pipe section 5? Straight pipe section 4, flow meter length? What is the meaning of this, exactly? ?
GB20093 contains relevant provisions: 1. The length of the straight sections before and after the flow meter should generally follow the requirements specified by the manufacturer; if no such requirements are given in the design, the provisions in the standard appendices shall apply. 2. When installing the thermometer and pressure sensors, the pressure sensor should be placed before the temperature sensor; otherwise, the thermometer will affect the flow pattern of the fluid, which in turn will impact the accuracy of the pressure measurement. 5.3.2 When the pressure sensing element and the temperature sensing element are installed on the same pipe section, they shall be installed in front of the temperature sensing element. 3. The same relationship exists between the thermometer and the control valve. Now, rating posts costs you your own wealth. No need to score.
This PID is somewhat similar to conventional ultrasonic flowmeters in that it requires a certain length of straight pipe sections before and after the flowmeter; typically, 10 times the diameter of the flowmeter ahead and 5 times that diameter behind. It also demands that the straight pipe sections be round and concentric, in order to prevent issues such as gas vortices inside the flowmeter. Temperature compensation for flow measurement is required to be carried out 3 to 5 times the diameter of the flowmeter downstream. However, pressure transmitters take pressure readings from the flowmeter itself, and as far as I know, vortex flowmeters do not require any specific length of straight pipe sections before or after them.
Yes, flowmeters require specified lengths of straight pipe sections before and after them.
There’s something I don’t understand: why are the temperature and pressure measuring devices installed between the flow meter and the control valve? Is it feasible to install it after the control valve?
Typical flow requirement: 10 straight sections ahead and 5 straight sections behind
For such flowmeters that require temperature and pressure measurement for compensation, all instruments must be installed in front of the control valve, and there are specific regulations regarding the installation distance depending on the pipe diameter. Mass flow meters and positive displacement flow meters seem to have no requirement for straight pipe sections. I can’t remember