Key points of customization of differential pressure flow meters:
The design and customization of the differential pressure flowmeter are to determine the various parameters of the differential pressure flowmeter according to the on-site process conditions. When customizing a differential pressure flow meter, you should first determine that the fluid conditions meet the following requirements:
(1) The fluid must be continuous and full of pipes.
(2) The fluid must be a Newtonian fluid, which is physically and thermodynamically homogeneous, single-phase, or can be considered single-phase. Mixed gas, solution, and colloid with dispersible particles smaller than 0.1um, in the gas, there is no more than 2% (mass component) evenly divided
Scattered solid particles, or bubbles with no more than 5% (volume component) uniformly dispersed in the liquid, can also be considered as a single-phase fluid, but the density should be average.
(3) No phase change occurs when the fluid flows through the throttle.
(4) The fluid flow rate does not change with time or changes very slowly.
(5) Before the fluid flows through the throttle, its stream must be parallel to the axis of the pipe, and there must be no swirling flow.
Second, the design requirements of the differential pressure flowmeter
1. Determine the necessary parameters, and determine the geometric size of the throttling piece through alternative calculations. These parameters include the name of the measured component, the percentage of each component for the mixed medium, the maximum flow rate, the common flow rate, the minimum flow rate, working pressure and variation range, working temperature and variation range, the maximum allowable differential pressure, and the maximum allowable The pressure loss, the type of throttle, the inner diameter of the pipe, the outer diameter of the pipe, the pipe material, the material of the throttle, the layout of the pipe, the type of upstream and downstream resistance and the length of the straight pipe, the roughness of the inner surface of the pipe, etc.
2. Fluid physical parameters
Including density, viscosity, isentropic index, gas compression factor, gas relative humidity, etc. also need to participate in the selection calculation, these are calculated by looking up the table or through the empirical formula. When using physical parameter data through literature materials, you need to pay attention to whether the selected data has the accuracy for reference and whether it can maintain consistency with other literature data. At present, the physical parameter data of flow measurement is generally taken from various physics, chemistry, and engineering manuals. Due to the mixed sources, the data is inconsistent.
The requirements of various manuals are different. It is difficult to fully meet the high accuracy of flow measurement and needs to be clear. The order of magnitude of accuracy is required. There are also insufficient data on many physical parameters, especially the physical properties of mixed fluids under high pressure, high temperature, low pressure, and low-temperature conditions, which are not only low in confidence or even completely lacking. Therefore, when citing empirical data or empirical formulas, pay attention to the following 3 points:
(1) Clarify the applicable conditions of empirical data, including the form of the medium, the temperature of the medium, and the pressure of the medium:
(2) Clarify the source of the collected data and ensure the consistency of the data;
(3) If necessary, determine the magnitude of uncertainty of empirical data
3. Determine the necessary accessories and complete the process of customizing the flowmeter
Due to the complexity of actual use, in order to be able to accurately measure, some accessories are required. for example. For straight pipe sections that do not meet the requirements, a flow regulator must be installed. When using a flow regulator, you should take into account its rectification function and at the same time pay attention to the conditions of the straight pipe section used.
4. Accessories on the pressure guiding pipeline
In the pressure guiding pipeline, some accessories are also required according to the conditions of use. The condenser is used to condense the steam in the pressure guiding tube, and make the condensate level in the positive and negative pressure guiding tubes have the same height and remain constant. The gas collector is installed at the highest point of the pressure guiding tube. Used to collect and periodically discharge the gas in the pressure guiding tube when the measured medium is liquid. The settler is installed at the lowest part of the pressure guiding pipe and is used to collect and regularly discharge the dirt in the pressure guiding pipe and the water in the gas pressure guiding pipe when the measured medium is liquid or gas. Isolators are used for high viscosity.
The measured medium is corrosive, easy to freeze, and easy to precipitate solids. To protect the differential pressure flowmeter. When measuring dirty or dangerous liquids, in order to prevent the medium from entering the pressure guiding tube, an injection system is adopted. These accessories are also selected according to actual needs and sometimes used in combination.