The main factors affecting the measurement accuracy of quantitative feeders

The accuracy of the quantitative feeder itself is determined by the equipment manufacturer. In addition to the manufacturing level of the scale body, the errors of the quantitative feeder mainly include measurement errors of belt load (material load), belt speed, instrument conversion and control calculation errors, errors caused by zero point changes, belt tension and changes, uneven belt stiffness, uneven belt quality, horizontal force changes, and material instability in daily maintenance.

The two main methods of existing weighing mechanism models

(1) Leverage type (with a cross spring serving as the lever fulcrum, all quantitative feeders on lines A and B of our company adopt this mode). The lever type scale frame has a large body and a large surface area in the horizontal direction, which can easily lead to zero point errors due to the accumulation of dust over a large area.

(2) Direct load-bearing type (usually using four sensors, our company uses this mode for mixed material conveying measurement, and A and B lines use this mode for clinker conveying measurement). The direct load-bearing belt scale adopts the "three no" structure of the direct load-bearing scale frame, which includes no lever, no fulcrum, and no balance weight, that is, there is no weighing carrier, and there is no problem of fulcrum wear; The surface area of the direct load-bearing scale frame in the horizontal direction is small, the amount of ash accumulation is small, and the zero point error caused by ash accumulation is small.

Daily maintenance content and precautions

(1) The weighing frame is a key maintenance point during the use of the scale body. It is necessary to keep the pressure head of the weighing sensor and the scale frame clean, check whether the fastening bolts are loose, whether the weighing frame is stuck in the scale (Figure 3), and whether the weighing roller rotates flexibly. The weighing sensor and speed sensor should be kept clean, especially the three weighing rollers on the weighing section, to avoid affecting the overall measurement accuracy.

(2) The belt, drum, and idler are all prone to material sticking, and the distance between the rubber plates of the inner and outer layer cleaners of the belt and the belt should be adjusted as appropriate to eliminate the impact of material sticking on measurement accuracy (most of the inner and outer layer cleaners of our batching scale have been removed, which will affect the measurement accuracy of the quantitative feeder).

(3) The length and tension of the belt can affect the accuracy of weighing. After replacing the feeding belt, maintenance personnel should adjust the belt tension by adjusting the bolt of the driven drum, and the measuring personnel should recalibrate the feeder.

(4) The scale bracket must not be moved or stepped on at will, otherwise it may cause damage to the weighing sensor due to overload fatigue, affecting the entire measurement accuracy (our company's cement grinding batching station has experienced damage to the weighing sensor due to blockage of the discharge port, explosion and cleaning, and shock waves).

(5) The conveying and weighing rollers should rotate flexibly without any jamming phenomenon. The weighing rollers should not rub against the scale body or belt, otherwise it will affect the measurement accuracy and even damage the motor and reducer (our company's cement grinding batching station has experienced the phenomenon of roller wear not being replaced in a timely manner or roller hard friction with the leather belt not being dealt with in a timely manner, which affects the measurement accuracy).

(6) In general, welding operations are not allowed on the scale body. If welding operations are necessary, electrical personnel must be notified to cut off the power of the quantitative feeder controller. Maintenance personnel should connect the grounding wire near the welding part, otherwise the current passing through the weighing sensor will cause damage, thereby affecting the entire measurement accuracy (our company did not take the above protective measures when maintaining the scale body welding, and the A and B clinker conveying weighing sensors were damaged due to welding problems and lost their normal weighing function).

(7) When repairing or replacing the belt of the quantitative feeder, the post or machine maintenance personnel must notify the electrical personnel to first cut off the power of the quantitative feeder controller and lift the sensor protection bolt. Otherwise, the weighing sensor will be damaged due to overload, which will affect the entire measurement accuracy (our company did not take the above protective measures when maintaining and replacing the belt of the scale body, resulting in fatigue and damage to the weighing sensor).

(8) When the quantitative feeder is not used for a long time, the protective bolt of the weighing sensor should be slightly supported to prevent overload of the sensor. At the same time, the weighing sensor controller should be powered off, the funnel gate valve should be closed, and the material should be emptied to prevent deformation of the belt due to long-term compression.