1. Requirements for straight pipe sections
Inlet/outlet straight pipe section: inlet should be ≥10×DN; outlet should be ≥5×DN
2. Grounding point requirement
In order to make the instrument work reliably, improve the measurement accuracy, free from external parasitic potential / the sensor should have good grounding, the grounding resistance is less than 10. (If the metal pipe is well grounded, no special grounding device is required) 3.3 Pair installation Location requirements as shown
Insert the electromagnetic flowmeter according to the situation of the pipeline in the field. If the flowmeter without the ball valve is installed, it should be installed on the pipeline without overpressure (that is, the flowmeter without the ball valve can be installed without pressure), and the hole is opened in the pipeline. Diameter 50, ready to weld the connecting welded pipe to the opening of the pipe; for occasions requiring constant flow loading or unloading or no media spillage, a ball valve must be installed, that is, a plug-in electromagnetic flowmeter with a ball valve structure is selected; With a diameter of 50, it is ready to weld the connecting welded pipe to the opening of the pipe.
Measuring range : Recommended range: 0.5m/s to 10m/s continuously adjustable. Maximum use range: continuously adjustable from 0.2m/s to 15m/s
Signal output: 1, the switch quantity can be set to: pulse output (up to 1000HZ); high/low flow alarm; empty pipe alarm; flow direction indication;
Fault alarm; 2, current output: 4-20mA output
Configuration method: 1. Field configuration through three manual keys. 2. Field configuration via remote control. 3. Perform on-site configuration through the handheld communicator.
Memory: The memory that the EEPROM does not disappear, no battery saving.
Second, gas turbine flowmeter measurement characteristics
1. Gas turbine flowmeter is one of the main types of flowmeters. Its working principle is: the gas entering the gas turbine flowmeter is accelerated by the fluid, and the accelerated gas acts on the blades of the turbine through the inlet passage. The impulse causes the turbine of the flow meter to rotate in the flow path, and within a certain flow range, the number of revolutions of the turbine is proportional to the volume of the gas flowing therethrough. By mechanical or electromagnetic induction, the number of revolutions f of the turbine can be obtained, so that the flow rate Q of the gas flowing through the flow meter can be obtained.
2. Gas turbine flowmeters are widely used in the measurement of gas flow or total gas volume, and are widely used in natural gas flow measurement at home and abroad. The theoretical research and practical experience of gas turbine flowmeters are very mature, and there are corresponding international standards. Countries also have corresponding national standards. China also adopts international standards. In Europe and the United States, gas turbine flow meters are the most important gas flow meters, and the Netherlands alone uses more than 2,600 gas turbine meters on natural gas pipelines.
Second, choose from the type of flow meter
Various flow meters, such as volumetric flowmeters, speedmeters, and differential pressuremeters, have different characteristics. Different flowmeter types have different turndown ratios. The turbine flowmeter has a turndown ratio of 1:20 to 1:30, the Roots flowmeter has a turndown ratio of 1:20 to 1:160, and the film gauge has a turndown ratio of 1: 160 (The error characteristic curves of these three kinds of flow meters are shown in Figure 1), and the appropriate flow meter should be selected according to the actual situation.
By comparing the error characteristics of the above flowmeters, it can be seen that the starting flow of the membrane meter and the Roots flowmeter is small, the initial flow of the turbine meter is relatively large, and the membrane surface exhibits a positive deviation in the small flow state. The Roots flowmeter exhibits a negative deviation. At low flow rates, the gas supply company is more willing to select a membrane meter for metering.