Maintenance Tips for Telescopic Stackers


September 1, 2008

Preventive maintenance and good housekeeping procedures will help extend the life and reliability of your telescopic stacker.

by Torben Johannsen

Telescopic stackers are among the most advanced conveyors available in the bulk material handling market – worldwide. Technology has advanced to such an extent that practically anyone can operate a stacker today at the touch of a few simple buttons. Unfortunately, nothing is ever as simple as it seems, and effortless operation can sometimes lead to effortless care. As with any machine, you get out of it what you put into it. Following regularly scheduled inspection guidelines and maintenance tips provided within the operator’s instruction manual will always extend the life and reliability of your telescopic stacker. Take proper care and it will last a lifetime.

Keeping a record of all maintenance and inspections is not only informative for the future value of the machine, but will prove helpful in circumstances where warranty coverage is validated. Using a daily and monthly checklist for inspection is ideal (see checklists provided). Regardless of any manufacturer’s warranty policy, proper maintenance and care play critical roles in the process of warranty claims. In fact, most warranty claims, if and when they occur, are often rejected based on improper care or failed compliance to maintenance guidelines.

Standard maintenance tips

The following preventive measures are generally considered an essential part of a telescopic warranty policy and represent minimum guidelines for inspection and maintenance.

* Winch cables: The winch cable system must be properly maintained to ensure smooth operation as well as the safety of those who operate it. It is important to keep winch drums clean, as debris can significantly reduce the lifespan of a winch cable. Winch cables should be inspected daily for cable slack, cable fraying, and wear on the wire rope sheave. The lifespan of a typical winch cable can reach more than 20 years with proper maintenance. Most cable winch systems are equipped with tensioning springs and limit switches for additional safety.

* Lubrication: To ensure proper operation, periodic lubrication on a weekly basis or every 50 operating hours is very important. Critical lubrication points include inner and outer tail and head pulley bearings, support roller bearings, support shaft bearings, winch drum bearings, and cable sheave bearings. Failure to properly lubricate can cause multiple problems such as contamination, overheating, and, eventually, premature failure. It is important to understand that over greasing can be just as problematic as under greasing. If a bearing is greased to the point that it starts leaking, dust and dirt may stick and eventually work its way back into the bearing causing long-term damage.

* Wheel hubs: Hub oil levels should be checked before any stacker is permitted on the road or every 6 months if working in a permanent location. Follow your manufacturer’s recommendations when selecting an oil type.

* Speed reducers: Oil in all gear reducers should be changed periodically. Under average industrial operating conditions, the lubricant should be changed every 2,500 hours of operation or every six months, whichever occurs first. As every operating condition is different, it is recommended that operators consult their original equipment manufacturer for the proper oil to use at a specific location.

* Sensors: Material sensors and proximity sensors are used on telescopic stackers to provide various automated functions. If these sensors are not clean, automation may not function properly. Sensors should be inspected daily.

* Touch screens: Some telescopic stackers use touch screens for easy operation. It is important to train all operators on the proper use of a touch screen, as extensive abuse can result in the loss of transmissibility. These screens do not require the same force necessary to activate a mechanical switch. Many operators use foreign objects, which may scratch the front panel and reduce the transmissibility of the touch screen. Touch screens are easy to clean with a damp non-abrasive cloth or towel using any commercially available window cleaner. The cleaning solution should always be applied to the cloth or towel rather than the surface of the touch screen. Solvents and abrasive cleaning compounds will cause permanent damage.

* V-belt drives: Improperly tightened V-belts can lead to poor drive efficiency, excess noise, and slippage of the conveyor belt. Drive belts will require regular tightening over the full lifespan of the telescopic stacker. Slippage of the drive belts and excess noise within the first 24 hours of service is common. It is recommended that you inspect and tighten the drive belts after the first 24 hours of operation at peak load. If the V-belts are slipping or squealing, they will require tensioning. Proper tension and alignment will significantly increase the life of the conveyor’s drive system. Applying a dressing is not recommended, as it can damage the V-belts and cause early failure. V-belts will deteriorate over time under regular usage and exposure to elements. Periodic replacement of V-belts is to be expected. If you do need to replace the V-belts, always replace a complete set and never replace only one belt at a time.

* Limit switches: On most telescopic stackers, limit switches are used as input devices to the PLC, which governs key telescopic motions such as extend and retract and radial limit. It is of critical importance that all limit switches be inspected and maintained daily to ensure that these motions are in good working order.

For best results, limit switches should be free of dirt and debris, they should never be stuck, jammed, and/or damaged, and the housing should never be damaged or cracked. Both the cable and plastic whisker should always be in good condition.

Additional maintenance tips

There are many practical “unwritten” steps that many successful operations take to drastically extend the life and profitability of their telescopic stackers. These are the most valuable and yet commonly neglected recommendations in the industry.

* Housekeeping: The most important factor that is commonly neglected in telescopic stacker maintenance is proper housekeeping. Any buildup of material on the machine, as well as under the machine, should be religiously removed at all times. In accordance with the usage of the machine, a housekeeping schedule should always be developed. Properly cleaning a machine allows the operator to effectively inspect it, see all moving parts, assess the conditions of various components, and prevent costly downtime.

Lack of proper housekeeping has created more downtime and mechanical breakdowns in the bulk material handling industry than any other singular maintenance procedure. Although it may not be the most exciting job to do, it has the greatest long-term value. Successful aggregate operators systematically implement an ongoing housekeeping schedule, which often eliminates about 90 percent of their downtime.

*Transfer points: Another factor often overlooked is the importance of setting proper transfer points. As material shoots into the receiving end of a telescopic stacker, it should always land in the very center and as close the rear of the receiving hopper/chute as possible. Sometimes, because of the trajectory of the material as the conveyor makes its radial motions, material can miss the center target. This can create problems such as “miss-training,” spillage, and, in extreme cases, rip the edge of the belt. Operators often overlook the relevance of transfer positioning, and start “training” the belt as soon as they see that the belt is not running well. Improperly diagnosing this problem will only lead to additional wear that could be prevented with proper consideration to the transfer point positioning and material trajectory. It may be a tedious job, but it pays off big time in the long run.

* Continuous feed: A constant even feed of material will cut down the cost of energy. Not only do you spend money for every rotation running empty belts, but loading a belt after empty puts an initial higher load on the motors. Such costs in wattage and wear on the motors are unnecessary.

Crushing operations should try not to have surge hoppers, as they cause numerous problems and inconsistencies to the overall material handling. Several variables can affect continuous feed. Assess these variables and target the weak areas by the source.

* Smooth terrain: Although most telescopic stackers are designed to run on uneven surfaces, a concrete runway is often recommended. If this is not possible, it is important for operators to understand the affects of uneven terrain. The flow of material is directly affected as a telescopic stacker or any radial stacker, for that matter, moves over rough terrain. Bumps and small craters can also affect the center point of material trajectory into the receiving hopper. By interrupting the flow of material, you run the risk of material segregation and belt degradation. The smoother the terrain, the better the flow of material and the less stress you put on the machine. A concrete runway can often provide a quick return on investment. It often rapidly pays for itself by reducing long-term potential downtime.

* Electrical panel: The electrical panel can be considered the brain of a telescopic stacker and, therefore, should be treated with special care. Operators often fail to properly close the electrical panel, which exposes critical components to damaging environmental elements. Constant exposure will increase the risk of fraying and damage that is costly to repair. Keeping the electrical panel closed at all times is a simple task that should never be overlooked. When cleaning a panel, always use a vacuum; do not use a blower hose. This will simply push contaminants further into the component.

* Standing position: Quite often, a machine that is standing unused can cost more than a machine that is being operated. Although inspections on telescopic stackers are scheduled based on operating hours, if not put aside properly, the machine can undergo continuous stress. Since a telescopic stacker is a cantilever structure, the operator should always retract the machine at the end of the day. Exposure to weather and severe conditions can damage the structure, especially when it is not fully retracted and lowered to the ground. Winds that pick up overnight will add substantial and unnecessary stress to the machine.

Leaving a telescopic stacker sitting loaded is also not a good operating practice. Clearing the machine of all material removes unnecessary stress on the structure of the conveyor. Reducing the loads on the structure and all moving parts will prolong the operating life of the machine.


Torben Johannsen is a territory manager and service technician for Thor Global Enterprises Ltd. Johannsen’s industry experience dates to 1992, as he participated in the building of the first telescopic stackers made for the aggregate industry. He continues to be involved in all facets of the business through sales, service, management, product development, and international expansion.

Monthly Inspection Checklist (or every 180 operating hours)

Drive Belts: Are belts free of wear and/or damage?

Are belts seated properly for tension and alignment?

Motors & Gearboxes: Are all components of the drive system free of wear, damage, and/or improper operation?

Lubrication: Are all recommended components properly lubricated?

Conveyor Belting: Are belts free of debris, damage, obstruction, and/or malfunction?

Idlers: Are idlers free of debris, damage, obstruction, and/or malfunction?

Pulleys: Are pulleys free of debris, damage, obstruction, and/or malfunction?

Scrapers: Are scrapers free of debris, damage, obstruction, and/or malfunction?

Structure: Is the structure free of damage, wear, distortion, and/or evidence of stress?

Hydraulics: Are all hydraulic components free of damage, wear, cracking, and/or malfunction?

Are fluid levels accurate?

Electrical Panel: Are all wires free of damage or fraying?

Are all components in good condition and protected from the elements?

If the answer to any of the above is No, then the problem must be rectified immediately. Maintenance Required


Daily Inspection Checklist (or every 12 operating hours)

Safety Features: Are all covers and guards secure and in place?

Are all warnings posted and visible?

V-Belt Drives: Are V-belts tight and in good condition?

Limit Switches: Are the limit switches free of dirt and debris?

Are the limit switches free of jams and/or damage?

Are housings free of damage or cracks?

Are cables in good condition?

Are plastic whiskers in good condition?

Tires: Are the tires inflated and in good condition?

Structure: Is the structure free of damage, wear, distortion, and/or evidence of stress?

Conveyor Belting: Are belts aligned and in good condition?

Winch: Is the winch system taut, properly wound, aligned, and free of damage?

Hazards: Is the area around the conveyor free of personnel, equipment, and other obstructions?

Sensors: Are all sensors visibly clean?

If the answer to any of the above is No, then the problem must be rectified immediately. Maintenance Required

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