Make sure spray nozzles are fully open and operational.

These eight tips will help to keep all types of aggregate screens in optimal working condition.

Aside from all the proper adjustments and operating parameters required to gain the most in screening efficiency, the need for good preventive maintenance practices is a must for longer lasting screens and reliable performance. “Above all, be proactive,” says Deister Machine Co. Service Manager Scott Murphy, an industry veteran with more than 25 years of experience. “Develop a keen focus in forecasting, and then fixing, each factor that could cause potential problems. And take the time to do maintenance the right way — before, rather than after, component failures occur.” Murphy shares the following tips for superior screen maintenance.

1.  Establish an oil sampling program.

Although a commonly overlooked practice, a regularly scheduled oil sampling is an operator’s best insurance against catastrophic component failure and costly downtime. The valuable insights provided by samplings — such as detecting a worn bearing — allow operations to cost-efficiently schedule maintenance downtime around periods of prime production.

Scheduled sampling and analysis establish a baseline of normal wear and can help indicate when abnormal wear or contamination is occurring. Oil that has been inside any moving mechanical apparatus for a period of time reflects the exact condition of that assembly. Oil is in contact with mechanical components as wear metallic trace particles enter the oil. These particles are so small they remain in suspension. Particles caused by normal wear and operation will mix with the oil. Any externally caused contamination also enters the oil. Identifying and measuring these impurities indicates the rate of wear, as well as any excessive contamination. Importantly, an oil analysis will also suggest methods to reduce accelerated wear and contamination.

2.  Employ recommended lubrication practices.

Always consult your owner’s manual for the manufacturer’s recommended lubrication practices.

Clear material buildup around components such as the screen support springs.

Install the correct amount of oil, and use the recommended type of oil. Change the oil at the proper intervals, making sure that the oil in storage is clean and that clean containers are used to transport the oil. Make sure that your machine is completely level so that oil does not flow to the low side of the machine.

3.  Maintain proper belt tension.

Belt tensioning must be right on target for optimum screen performance — not too loose and not too tight. Ideally, the belts should only be tight enough that they do not slip during startup. If necessary, use a belt gauge to tension correctly. If belts squeal during startup or in operation, or whip excessively, this may indicate insufficient belt tension.

Importantly, over-tightened belts can cause serious damage such as the vibrating frame being pulled out of square with the support frame. Operating in this twisted position introduces stresses that may lead to spring failure, metal fatigue, or cracking and broken welds. Additionally, this twisting affects stroke amplitude and character, which then affects material flow and screening efficiency. Over-tightened belts also put an extra load on the mechanism bearings and may tear up motors and motor bases.

Additionally, to prevent drive belts from slipping, flopping, or coming off, belts and sheaves must be kept clean and properly aligned. Inspect sheaves for wear, and, if the grooves are worn, replace the sheave.

4. Prevent material buildup.

Accumulation of dust and stone around moving parts is one of the largest single causes of part failures, particularly for pivot motor bases, support springs, roller bearings, and the vibrating frame. Impact between the vibrating frame and accumulated material may lead to tower vibrations as well as potential side-sheet and support-deck cracking.

Shown here is a section of screen cloth manufactured with a severe warp that would cause it to fall permanently.