January 6, 2012
Material handling system operational reliability and safety requires the proper care and feeding of conveyor hydraulic systems.
Slackers beware. While some operations are right on target with the somewhat sophisticated hydraulics maintenance needs of major stationary crushing components or highly mobile portable plants, they may not allocate adequate maintenance time to material handling systems with simpler hydraulic setups, yet similar demands in day-to-day operating hours. Don’t fall prey to the common misconception that one can realize maximum performance from conveyor hydraulic systems with little to no maintenance attention — as the latter will surely lead to costly repairs, component failures, and safety risks regarding the operation of indispensible and hard-working material handling systems.
A proactive and preventive conveyor hydraulics maintenance program leads to greater cost- efficiency paybacks, plus the delivery of the reliable machine performance required for the high-volume feeding, transfer, and stockpiling of saleable products. Certainly a modest investment in time and effort is involved; however, conveyor hydraulic maintenance is not rocket science, but rather the adherence to simple common sense guidelines. According to material handling experts, here are the top factors to include in an effective hydraulics maintenance routine.
1. Monitor fluid levels
Most importantly, always maintain the correct hydraulic oil level according to the gauge on the tank itself, and check the levels before starting the equipment. Inadequate oil levels may result in major component failures due to cavitation, or causing parts to starve for oil, or from aeration, which means that air is being sucked into the system, or from overheating. These issues result in a snowballing effect that ultimately deteriorates or even destroys the pump and contaminates the entire system. Note that, if a pump does not receive oil, severe damage can occur within as little as 10 seconds.
2. Conduct routine maintenance inspections
Weekly inspections should include checking fluid levels, filter indicators, temperature gauges, breather caps and filters, and checking all components, system hoses, and connections for leakage. Inspect for aeration which is identified in the reservoir by looking for foaming or little whirlpools that appear due to gulps of air being taken into the suction strainer. If detected, this may indicate low fluid levels, high viscosity, low fluid temperatures, faulty shaft seals, or air leaks in the suction line. Listen to pumps for any high-pitched whining sounds during operation, which may indicate signs of cavitation.
3. Use the right hydraulic oils
Always use the manufacturer-recommended brand and do not mix oils. Use the proper viscosity grade. Viscosity is defined as a measurement of how resistant a fluid is to attempts to move through it. Low viscosity fluid is said to be thin, while high viscosity fluid is thick. The usage of the proper oil is integral to ensuring cold starts, offering high-temperature protection, and maintaining optimum system efficiency. Your manufacturer will work with you to select the right oils for the application and environment. Note that, depending upon climate and temperatures, oil heaters or cooling systems may be required. Additionally, highly dusty applications may require specialized breather systems, while extremely wet applications may require special attention to component seals.
4. Eliminate leaks
Many say that hydraulic systems are invariably going to leak; therefore, leaks are commonly accepted in the industry. Think again — leaks should never be accepted — period. If you see a leak, fix it. Not only do leaks let oil escape, they are also an attraction for dirt that may build up on equipment, leading to contamination of the system, the product, and the environment; and safety hazards such as fire or injuries to workers from oil leakage contacting parts of the body.
5. Maintain fluid cleanliness
On conveyor systems such as telescoping radial stackers, change the hydraulic oil every 1,000 hours or certainly whenever contamination is suspected. Don’t fall for the misconception that sealed hydraulic systems do not require oil changes, as they do have sources of pollution. Changes in temperature can induce moisture into the oil, and any leaks are a source for dirt contamination. Combine that with a lack of oil changes and one is running a dirty mix of oil with the potential of wearing out pumps and valves.
Properly store hydraulic oils in their original closed containers. Clean the top of the container before opening and pouring, and use a clean funnel with a built-in strainer when filling. Remember that particles as small as 10 microns can cause severe damage to a hydraulic system.
6. Change oil filters and breathers
So often, it’s thought that just any filter will do. But balance the cost of the recommended filter against the prevention you receive — and don’t cut corners. Use only filters meeting performance specifications, as improper filters may lead to premature hydraulic failure. Change out the hydraulic oil filters every 500 hours of operation and also when the oil is changed seasonally. Change both the filters and the oil if contamination is suspected.
When the fluid level lowers in the reservoir, it is displaced with air. The breather is a fiber filter (located on the top of the tank) that allows free air flow in and out of the tank. The breather must be kept clean and maintained. It is not all that uncommon to see systems where breathers have been lost and not replaced, and that is unacceptable. The breather should be replaced once every season or more often if the unit is run in extremely dusty or abrasive conditions.
7. Maintain an oil analysis program
An effective oil analysis program can detect some early warning signs of contamination or impending component failure. For example, rising metal levels in the oil can indicate serious pump wear and tear. Alternatively, analysis trends may indicate that oil change intervals can safely be increased. At minimum, check your hydraulic systems by analysis no less than annually. On a telescoping radial stacker, due to its continuous operation of belts, feeders, pump, and computerized hydraulic systems, oil sampling is recommended every 500 hours.
8. Commit to a “complete” approach
Should a component failure occur, conduct a failure analysis. What caused the failure and how might it be avoided in the future? Consider that, if a hydraulic motor has failed, contamination has affected the entire system. If a pump has failed, metal is flaking into the system. Yes, replacing either of these components will get the system up and running, but it is a must to take the next step of cleaning out the entire system — including all the hoses and tanks — to ensure the removal of contamination. Make sure that systems are cleaned externally as well. It is advisable to pressure wash the outside and top of the hydraulic tank. Also, wash the oil filter assembly and the area around the oil filter.
The integrity of hydraulic systems is directly tied to the reliable performance of material handling systems. For example, in the case of telescoping radial stacking conveyors, hydraulics and valves hold the unit in position during operation. Valve contamination could allow inconsistent operating height levels and serious safety risks. So keep a heads up on hydraulic equipment, as its proper maintenance really does matter. AM
Material supplied by Superior Industries, a manufacturer of conveyor systems and components. Contributors include Superior Industries Customer Service Agent Lyle Hettver; and Brian Pichlar, service manager for Superior Industries dealer R.B. Scott.