Trial Operation of the Molino

Whether it is a newly installed grinding mill or one that has undergone major repair, after installation is completed, testing, adjustment, and inspection have been carried out, a trial operation must be conducted. Only after passing the trial operation can the mill be put into production. The purpose of the trial operation is to further observe and adjust the interrelationships of various parts and components of the grinding mill, to check and verify whether the installation meets the design performance requirements and the quality technical standards of installation, and also to allow the relative moving parts of the mill to run in.

Preparation Before Trial Operation

The preparation work is as follows:

(1) Check the drying and insulation condition of the electric motor, and perform a no-load test run with the motor disconnected from the mill;

(2) Carefully check the tightening condition of all fasteners on all installed equipment;

(3) Clean and lubricate all lubrication points;

(4) Check whether the sealing devices at each seal (e.g., the contact area between the two end faces of the main bearing and the hollow shaft journal, etc.) meet the quality requirements;

(5) Install and check whether various protective devices are complete and reliable. For example, whether the oil pressure relay will act when the oil circuit is cut off; whether the mercury switch can close the stop contact when oil is cut off; whether the ammeter and voltmeter are normal, etc.;

(6) Perform an empty mill (no grinding media, no material) barring (turning) to check whether the grinding mill and other rotating bodies have any contact or collision with other objects, and whether there are any abnormal sounds.

After completing the above inspections and deeming everything satisfactory, the trial operation can proceed. The trial operation shall be divided into several stages: no-load, half-load, and full-load.

No-Load Trial Operation

After empty mill barring and confirming that the grinding mill can be started, start the mill without grinding media and without feed for no-load trial operation. The no-load trial operation shall meet the following requirements:

(1) The no-load test run shall last no less than 4 hours in both forward and reverse rotation;

(2) During operation, the transmission gear shall have no abnormal noise, and the liners shall have no knocking sound;

(3) The bearing temperature shall not exceed 70°C, and the double amplitude (peak-to-peak vibration) shall not exceed 0.01 mm;

(4) The double amplitude of the reducer shall not exceed 0.05 mm;

(5) The double amplitude of the transmission shaft shall not exceed 0.08 mm.

If any of the above requirements are not met during no-load operation, timely inspection and correction shall be carried out until the requirements are satisfied. After the no-load trial operation has reached the specified time, stop the grinding mill, thoroughly measure and inspect the working condition of each part, and eliminate all existing problems.

Load Trial Operation

After the no-load trial operation is (acceptable), load trial operation can be carried out. The load trial operation shall be conducted in two stages.

First, add grinding media to 25%–30% of the normal filling rate, along with an appropriate amount of material (continuous feeding is not allowed) and water. Operate for 8–10 hours. If no fault occurs, stop the grinding mill and check the operation of each part. After inspection confirms that everything is normal, increase the grinding media to the rated filling rate and appropriately increase the amount of material. Then operate for another 10–20 hours under full load and normal feed conditions. This completes the trial operation.

The load trial operation shall meet the following requirements:

(1) The grinding mill operates smoothly, without severe periodic vibration or slight impact sounds;

(2) The main motor current fluctuates within the allowable range, and the temperature is below the allowable temperature rise;

(3) All lubrication points are functioning normally, and the main bearing temperature is below 70°C;

(4) There is no water leakage, slurry leakage, or oil leakage at the grinding mill and all sealing points.

After completing the above work, the user unit and relevant technical departments shall jointly accept the mill. If deemed合格 (acceptable), the user unit, the installation unit, and relevant personnel shall sign the handover certificate, and the mill can then be delivered for production use