To ensure the measurement accuracy of the electromagnetic flowmeter, proper installation is very important.
The transmitter should be installed in a dry and ventilated place indoors. Avoid installation in places where the ambient temperature is too high, should not be subject to strong vibration, try to avoid equipment with strong magnetic fields, such as large motors, transformers, etc. Avoid installation in corrosive gases. The installation location is easy to overhaul. This is the environmental condition to ensure the normal operation of the transmitter.
In order to ensure that the measuring tube of the transmitter is filled with the measured medium, the stacker is preferably installed vertically, and the flow direction is from bottom to top. Especially for liquid-solid two-phase flow, it must be installed vertically. If the site is only allowed to be installed horizontally, it must be ensured that the two electrodes are at the same level.
The transmitter should be equipped with valves and bypass at both ends.
The millivolt AC potential measured by the electrode of the electromagnetic flow transmitter is based on the liquid potential in the transmitter. In order to stabilize the liquid potential and maintain the potential of the transmitter and fluid to ensure stable measurement, the transmitter shell and the metal tube should have good grounding at both ends, and the converter housing should also be grounded. The grounding resistance should not be greater than 10 and cannot be shared with the grounding wire of other electrical equipment. If the transmitter housing is not guaranteed to be in good contact with the metal pipe, connect them with metal wires. Re-reliable grounding.
In order to avoid interference signals, the signal between the transmitter and the converter must be transmitted with shielded wires. It is not allowed to place the signal cable and power cable in parallel in the same cable. The length of the signal cable should generally not exceed 30 m.
Converter installation site should avoid AC and DC strong magnetic field and vibration, ambient temperature is -20 to 50 ° C, does not contain corrosive gases, relative humidity is not more than 80%.
In order to avoid the influence of the flow rate on the relative measurement, the flow regulating valve should be placed downstream of the transmitter. For small-caliber transmitters, since the distance from the center of the electrode to the inlet end of the flowmeter is equivalent to several times the length of the diameter D, the upstream straight pipe may not be specified. However, for a flowmeter with a large diameter, generally there should be a straight pipe section of 5D or more in the upstream, and the downstream pipe section is generally not required.
Turbine flowmeter composition
Turbine flowmeters are speed flowmeters, also known as impeller flowmeters. The impeller type flowmeter utilizes the relationship between the rotational angular velocity of the impeller placed in the fluid and the fluid flow velocity. By measuring the rotational speed of the impeller to reflect the volumetric flow rate of the fluid passing through the pipeline, it is a relatively mature high-accuracy instrument in the flowmeter. One. Turbine flowmeters generally consist of the following five typical parts:
1. Body
The material of the body is generally steel or cast iron, and the ends are flanged. The small diameter gauge also has a threaded interface.
2. Measured component
The turbine has precision machined blades that together with a set of reduction gears and bearings form the measuring assembly. The two high-precision stainless steel permanent self-lubricating bearings that support the turbine ensure a long service life of the assembly. Turbine flowmeters can also be lubricated with an external lubricant pump, but be careful not to overdo it.
3. counter
The following important information is available on the counter panel:
(1) Maximum working temperature and pressure:
(2) Metering and minimum and maximum flow levels
(3) Product model and number
(4) Explosion-proof grades and signs
(5) The equivalent of the fluid corresponding to the low frequency or high frequency pulse and the wiring method.
4. Rectifier
The rectifier is used to keep the fluid flowing through the turbine flow meter in a regular state, thereby eliminating the disturbance and having an unaffected effect on the metering. High metering accuracy.
5. Magnetic coupling transmission device
The device separates the counter portion in the atmospheric environment from the gas being measured and transmits the rotation of the measuring assembly to the counter.
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.