Thinking Inside the Box: Broken Screen Diagnoses
Written by Steve Fair, Engineered Media Division Manager, Haver & Boecker Niagara’s Canada location
Imagine you’re in the midst of peak production. Material output is at its prime and systems hum along smoothly. But then a section of wire cloth breaks. The operation grinds to a halt until a technician completes the repair. It’s bound to happen at some point, but it will happen less frequently by checking some tell-tale signs.
Here are four steps to minimize downtime and promote a smooth operation:
Step 1. Ask an Expert: When excessive screen wear occurs, a screen media expert can quickly analyze the operation to find a solution. And, if screens are wearing quickly, there’s likely a better screen media solution. Polyurethane screens, as an example, manage wear well, but some perform better than others. A screen media expert will examine your media, and explain your options. For instance, open-cast polyurethane will last 1.5- to two-times longer than injection molded.
Step 2. Check to See if the Section has Moved: How do the hooks look on the screen sections? If there are shiny areas, it could be a sign that the section is loose and moving back and forth during operation. Also, ensure that the bar rail liner is in good condition and the tension rail bolts are tight. Consistently monitoring the torque helps determine the cause of some problems since improper tensioning leads to premature breakage. It’s also essential to look at the machine as a whole and take several aspects into consideration, such as if there is a bolt in every hole. Areas without bolts are susceptible to breaking.
Beyond checking the torque values, using the correct section size is vital on side-tensioned screens. To check, begin by measuring inside the vibrating screen from sideplate to sideplate. If the measurement is 72 inches, for instance, subtract 1.5 inches to determine the outside hook dimension. From there, measure the length of the tension rail and ensure the section matches that dimension.
Step 3. Look at the Camber: Check the camber on the screen deck and the bar rails for wear. On a double cambered deck, make sure the center hold down is being used. The camber gives the section the down-and-out tensioning required to keep it in place. Every bar rail should be supporting the section. If the screens aren’t tensioned correctly or the center hold-down bar isn’t being used, breakage will happen sooner rather than later.
Step 4. Inspect the Bar and Tension Rails: Are they in good condition? It is important to ensure the bar rails are not worn. Even if you put new liners on a worn bar rail, they can’t support the section. Also, monitor the tension rails that hold each screen section in place. Worn or bent tension rails need to be replaced. If the rails are worn, speak with your OEM to have them replaced and avoid turning to local fabricators for the replacement. While cheaper, you’re sacrificing quality because local fabricators frequently use substandard material and can put the wrong bend on the rail, which shortens the section’s life. OEM parts are made specifically for each machine, so there’s never a worry about it not fitting precisely as intended. Check, too, that the bar rail liners are in good condition and that no areas are missing, which also can lead to premature breakage.
When All Else Fails
Even if all of these steps are done correctly, there could still be a problem if the wrong screen media is being used for the application. Talk to your screen media expert to see if there is a better solution for your application.
Some manufacturers have certified technicians who provide on-site inspection of your vibrating machine and screen media as well as training to help a team learn the best way to install screen media. Many also use vibration analysis software for a more detailed analysis, with some systems able to monitor as many as 24 channels of data in real time. That combination will keep an operation running smoothly and minimize downtime.