Pubdate：04-24-2022 Views：3231
Initial installation of conveyor equipment should ensure good alignment of all pulleys, troughing idlers and return idlers; that is, they should be placed at right angles to the direction of belt travel and should be leveled and centered on a straight line. First movement of the belt should be slow and intermittent so that any tendency of the belt to run off can be quickly observed and the belt stopped before damage occurs.
When the conveyor is a long center installation, men should be stationed at frequent intervals to observe the action of the belt. They should be provided with an effective method of communication so they can report their observations and if necessary, stop the belt.
Initial movement of the belt will indicate where corrections of the types described are required. The first corrections must be at points where the belt is in danger of being damaged. Once the belt is clear of all danger points, a sequence of training operations can be followed. Since the training will finally complete a circuit, just as the belt does, there is no point at which training can be started without the possibility of having to make subsequent corrections when returning to the starting point as the circuit is completed. The best procedure appears to be in starting with the return run and working toward the tail pulley. This ensures early centering of the belt on the tail pulley so that it can receive its load centrally, which is highly important.
If the belt is readily troughable so that its running tendencies are not erratic, the training can and should be completed on the empty belt. Should it tend toward stiffness and erratic running, getting some load onto the belt as soon as the return run has been straightened up and the belt is centered on the tail pulley will help hold the top run.
Normally, the belt can be trained properly onto the tail pulley by manipulation of return idlers and with the assistance of self-aligning return rolls. Seldom is any adjustment of snub or tail pulley necessary, but the snub can be used in supplementary training.
Training of the top run, with the belt empty, is usually no problem if the belt is readily troughable. In this case, selfaligners on top are not required, except as insurance in the region approaching the head pulley. There, two self-aligners placed approximately 40 and 80 feet preceding the pulley will help re-center the belt if it is forced off due to some temporary disturbance.
It should not be necessary to use the head pulley for training purposes if it has been aligned properly. Likewise, the snub following the head pulley should not be required as a training means, since it is relatively ineffective in its position following the strong head pulley influence.
The take-up carriage has a strong influence on the running of the belt at that point, and due to its movement as belt length changes, is subject to misalignment. A vertical take-up carriage, hanging in a festoon of belt, must be guided in its travel so that the pulley shaft remains horizontal. The belt cannot be depended upon to center itself on the pulley. Once it becomes off-center, the pulley will tip out of horizontal if not guided closely on its posts.
Fig. 1
A horizontal take-up carriage (Fig. 1) is subject to misalignment due to loose track gauge, fouled rails, or even jumping off the track. V-shaped rails will hold the gauge tight and, with the apex upward, are self-cleaning. Hold-down rails or hooks extending under the flange of the track structure will prevent jumping off the track.
With the empty belt trained satisfactorily, good operation with load is usually ensured. Disturbances that appear with load are usually due to off-center loading or to accumulation of material from the load on snub pulleys and return idlers.
When equipment is known to be properly aligned, training action should be taken slowly – that is, in small steps, because the belt requires some time to respond to corrective measures. It should begin at some point preceding the location where runoff occurs, and gradually proceed forward in the direction of belt travel, until the runoff condition has been corrected. Under some conditions of operation where the conveyor is not level, is extremely short or is too wide to be affected by permissible crowning, belts with a special guide strip have been used. This V-guide strip runs loosely in grooved pulley and idler rolls. Guide strips are not recommended nor are they necessary for the long conveyors normally encountered in industrial use.
