Detailed explanation of installation specifications for time difference ultrasonic flowmeter
(I) Learn more about the scene
The ultrasonic flowmeter should be aware of the situation before installation, including:
1. What is the distance from the host where the sensor is installed;
2. Pipe material, wall thickness and pipe diameter;
3. Pipeline life;
4. Fluid type, whether it contains impurities, air bubbles and whether it is full of tubes;
5. Fluid temperature;
6. Whether there are interference sources at the installation site (such as frequency conversion, strong magnetic fields, etc.);
7. The temperature of the four seasons where the host is placed;
8. Whether the power supply voltage used is stable;
9. Do you need remote transmission signals and types?
According to the on-site conditions provided above, manufacturers can configure the on-site conditions, and can also make special models if necessary.
(Two) choose the installation location
The selection of the installation pipe section has a great impact on the test accuracy. The selected pipe section should avoid the two situations that have a large impact on the measurement accuracy. Generally, the pipe section should meet the following conditions:
1. Avoid installing machines in pumps, high-power radio stations, frequency conversion, that is, where there is a strong magnetic field and vibration interference;
2. Select pipe sections that are uniform and dense and easy for ultrasonic transmission;
3. To have a long enough straight pipe section, the upstream straight pipe section of the installation point must be greater than 10D (Note: D = diameter), and the downstream must be greater than 5D;
4, the installation point upstream from the pump should be 30D distance;
5. The fluid should fill the pipeline;
6. There should be enough space around the pipeline for on-site personnel to operate. Underground pipelines need to be tested wells. The test wells are as follows:
(Three) determine the probe installation method
Ultrasonic flowmeters generally have two probe installation methods, namely Z method and V method.
However, when D "200MM and the site conditions are one of the following conditions, you can also use the Z method to install:
1. When the turbidity of the fluid to be measured is high, no signal is received or the signal is weak when measured by the V method;
2. When the inner wall of the pipeline is lined;
3. When the service life of the pipeline is too long and the inner wall has serious fouling;
For those with better pipeline conditions, even if D is slightly larger than 200MM, in order to improve the measurement accuracy, V method can be used for installation.
(4) Find the installation distance and determine the probe position
1. Enter the parameters of the pipeline into the instrument and select the probe installation method to obtain the installation distance;
2. On horizontal pipelines, generally choose the middle of the pipeline, avoiding the top and bottom (the top may contain air bubbles and the bottom may have sediment);
3. V method installation: first determine a point and measure another point at a horizontal position according to the installation distance.
Z method installation: first determine a point, measure another point at a horizontal position according to the installation distance, and then measure the symmetrical point of this point on the other side of the pipeline.
(V) Pipe surface treatment
After determining the position of the probe, within the range of ± 100MM of the two installation points, use an angle grinder, file, sandpaper and other tools to polish the pipe to a bright and smooth pit.
Requirements: uniform gloss, no undulations, smooth and round feel. Special attention should be paid to the fact that the grinding point must have the same arc as the original pipe. Do not sand the mounting point to a flat surface, and wipe this area with alcohol or gasoline to facilitate probe bonding.
(VI) Probe and instrument wiring
(VII) Fine-tuning the probe position
After connecting the wires, fill the inside of the probe with silicone, leave it for half an hour, then fix the probe to the polished pipe with silicone and clamps (note the direction of the probe, the lead end is outward), and then observe the signal strength and transmission of the meter Time ratio. If it is found to be bad, finely adjust the probe position until the signal of the instrument reaches the specified range:
(Signal strength: generally greater than 6.5, a few can be determined according to the specific conditions of the scene.)
(Transmission time ratio: within the range of 100 ± 3, this value must be stable.)
(Eight) fixed probe
After the instrument signal is adjusted, fix the probe with the provided fixture. Be careful not to tilt the wire rope, so as not to pull the probe and move the probe, and then seal the surrounding area where the probe contacts the pipe with silicone. It takes about a day for the gel to solidify. The probe must be waterproof before it dries. (The outer shield of the signal wire must be reliably grounded)