Selection of weighing module and precautions

Compared with the ready-made electronic weighing instrument, the biggest feature of the weighing module is that it is not limited by the site, flexible in assembly, convenient in maintenance and cheap in price.

The ground scale has a platform, so it must occupy a certain area. The weighing module is installed on the supporting point of the container, so it does not need to occupy additional land. It is especially suitable for parallel installation of multiple containers with narrow site. The measuring range and division value of the electronic weighing instrument have certain specifications, and the measuring range and division value of the weighing system composed of the weighing module can be set as required within the allowable range of the instrument. The weighing module is convenient for maintenance. If the sensor is damaged, the supporting screw can be adjusted to jack up the weighing body. The sensor can be replaced without removing the weighing module. In addition, due to the simple structure of the weighing module, the weighing system is composed of weighing modules, and the investment is relatively small.

2、 Application of weighing module in chemical enterprises

1. Chemical enterprises use a large number of storage tanks and measuring tanks in the process of material storage and production. However, two problems are commonly encountered, one is the measurement of materials, the other is the control of the production process. According to our practice, the application of electronic weighing module can be better solved. 1. The weighing module is used for material measurement. Generally speaking, most of the liquid in the storage tank is measured with a ruler or flowmeter. But both methods are measured by volume, and then converted into weight according to the density of the liquid. Because the density is related to temperature and other factors, the error is relatively large. Although there is a mass flowmeter at present, it is rarely used by general enterprises because of its high price. Therefore, it is economical and practical to directly weigh the material with an electronic weighing module.

2. The application of weighing module to liquid level indication and control is an important control parameter in chemical production process. Generally, in addition to the on-site liquid level indicator, the transmitter is used to convert the liquid level signal into standard electrical signal or gas signal for remote transmission to the control room. However, in addition to the liquid level error caused by the density change mentioned above, this method may also cause false liquid level due to material crystallization, blockage, etc., which may even lead to accidents in serious cases. In addition, because the measuring part of the transmitter directly contacts with the measured medium, for some corrosive media, it is necessary to select expensive corrosion-resistant materials. However, the weighing module does not directly contact the measured medium, and the above disadvantages do not exist. In addition, the weighing display instrument can be connected to the recorder and regulator with analog output interface to realize automatic recording and control.

3. The weighing module is used in occasions where there are strict requirements for the feeding amount. Some production processes have strict requirements for the feeding amount. Many enterprises put the measuring tank directly on the ground scale to control the feeding amount. However, it is troublesome to use hoisting equipment to hoist the measuring tank down when the ground scale is overhauled or calibrated. If the electronic weighing module is used, since the measuring tank itself is the scale body, there is no lifting problem, and the maintenance is relatively convenient.

3、 Precautions for purchase, installation and commissioning of weighing module

1. Precautions for selection of weighing modules: generally, the measuring range of three or four modules is selected according to the supporting point of the container. Due to the self weight of the weighing body (container), vibration impact, eccentric load and other factors, the following rules are generally followed.

Multi sensor static weighing system:

Fixed load (platform, container, etc.)+variable load (load to be weighed) ≤ rated load of selected sensor × Number of sensors × 70%, of which 70% coefficient is added considering vibration, impact and eccentric load.

In addition, attention should be paid to whether there are explosion-proof requirements. Explosion proof weighing modules should be selected for flammable and explosive occasions.

2. Installation precautions

(1) Pay attention to the horizontal adjustment, including the horizontal adjustment between the installation plane of a single module and a set of weighing modules.

(2) The sensor cannot pass the current during welding. When welding the top plate, the ground wire should be connected to the scale body. When welding the bottom plate, the ground wire should be connected to the foundation to prevent damage to the sensor.

(3) If there is a feeding pipe on the scale body, it should be replaced with a hose or the connecting pipe should be as long as possible to prevent them from eating the real load of the sensor and causing errors.

(4) A weight calibration table shall be welded on the container for calibration. There is generally no place to place weights on the container, so a platform needs to be welded to place weights. It is usually welded under the container to facilitate the placement of weights up and down.

(5) The junction box must be damp proof, and the excess holes must be plugged with sealing plugs. If the junction box is installed outdoors, a protective box must be added to prevent rain. In use, failures caused by the junction box being affected with moisture often occur, so enough attention must be paid.

Precautions for model selection

1. For the selection of weighing modules, the measuring range of three or four modules is generally selected according to the supporting point of the container. Due to the self weight of the weighing body (container), vibration impact, eccentric load and other factors, the following rules are generally followed. Multi sensor static weighing system:

Fixed load (platform, container, etc.)+variable load (load to be weighed) ≤ rated load of selected sensor × Number of sensors × 70%, of which 70% coefficient is added considering vibration, impact and eccentric load.

2 Installation precautions

Pay attention to the horizontal adjustment, including the horizontal adjustment between the installation plane of a single module and a set of weighing modules.

The sensor cannot pass the current during welding. When welding the top plate, the ground wire should be connected to the scale body. When welding the bottom plate, the ground wire should be connected to the foundation to prevent damage to the sensor.

If there is a feeding pipe on the scale body, it should be replaced with a hose or the connecting pipe should be as long as possible to prevent them from eating the real load of the sensor and causing errors.

A weight calibration table shall be welded on the container for calibration. There is generally no place to place weights on the container, so a platform needs to be welded to place weights. It is usually welded under the container to facilitate the placement of weights up and down.

The junction box must be damp proof, and the excess holes must be plugged with sealing plugs. If the junction box is installed outdoors, a protective box must be added to prevent rain. In use, failures caused by the junction box being affected with moisture often occur, so enough attention must be paid.

3. Commissioning precautions:

Before commissioning, be sure to check whether the nut on the top of the support screw of each weighing module has been loosened and whether the sleeve is in a free state; otherwise, large errors will occur and even weighing will not be possible.

During commissioning, it is necessary to check whether the factory setting value of each parameter meets the actual needs, especially the "startup reset" parameter, which is generally set as "startup automatic reset" when leaving the factory. It is better to change it to "no startup automatic reset" on the container scale to prevent the material weight of the container from being lost due to power failure and other reasons when the container is restarted.

The range setting does not refer to the rated total load of a set of weighing modules, nor does it include the weight of the container itself. Instead, according to the maximum material weighing, the maximum weighing weight should be selected as the range from the number and value of divisions given in the manual.

The power supply voltage of the weighing display must meet the requirements. If the voltage is unstable and exceeds the allowable range, it will cause digital drift. It is better to use a regulated power supply.

Because the weighing system composed of electronic weighing modules is convenient to realize automatic weighing and computer networking, it will be more and more widely used in chemical enterprises.

Weighing principle:

Taking the weighing of a typical chemical reaction kettle as an example, three pressure weighing modules installed at the bottom of the reaction kettle send the weight signal of the kettle body to the junction box. Each weighing module signal is connected in parallel in the junction box, and the angle difference can be adjusted according to the loading condition of each weighing module. The collected weight signal is sent to the weighing end or weight transmitter. The weighing terminal or weight transmitter processes the weight signal into corresponding weight data.

It is very difficult for non professional users to directly use the load cell.

The weighing module is a new type of weighing element, which combines the weighing sensor, load transfer device, installation connector and other components together, and can be conveniently connected with mechanical devices of various shapes, such as raceways, platforms, vertical cans, tanks, hoppers, etc.

The system installed with weighing module can not only ensure the high accuracy and good long-term stability of the weighing sensor, but also solve the weighing error caused by improper installation.

The equipment measuring with weighing module can usually achieve higher measuring accuracy.