Conveyor maintenance

by Emily Wilson
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Once harvest season is over, it’s a good time for grain storage facilities to think about maintenance on conveyor equipment. That way, the equipment will be in good working order when the next harvest gets under way.

A preventative maintenance program that is followed regularly will keep forced maintenance or equipment breakdowns to a minimum, according to William L. McLean, president of The Essmueller Co., Laurel, Mississippi, U.S.

The frequency of maintenance inspections depends on the type of material being conveyed and the class of service (length of operation), McLean said. "A conveyor that operates 24 hours a day will need to be inspected twice as often as one that runs eight hours a day," he said.

Dry, abrasive products also cause the most wear, he said, while ground products with a small amount of oil prolong the life of the conveyor.

The three main types of conveyors used in the grain industry include screw conveyors, drag conveyors and belt conveyors. This article will discuss preventative maintenance suggestions for the two most widely used conveyors: drag and enclosed belt.

IT’S A DRAG. Drag conveyors utilize a series of flights, or paddles, attached to a chain within a trough. Its mechanism consists of a chain, sprockets, flights, shafts, flange bearings, take-ups and other parts. The flights are made of a single piece of smooth, non-metallic material that is shaped to fit the trough. It exerts a wiping action that cleans the trough interior.

McLean’s company specializes in drag conveyors, although new enclosed trough and en-masse conveyors were recently added to Essmueller’s product line. He described the two general types of drag conveyors and offered tips for keeping them in good working order.

Round bottom and flat bottom drag conveyors get their names from their shape. The round bottom, or U-trough, conveyor forms the letter "U" when viewed from the end. The round bottom drag conveyor has a tall, half-moon shaped flight that covers approximately half of the material carrying area. As a result, it only partially depends on conveying material en-masse.

The flat bottom conveyor has straight sides and a flat bottom, hence the name, and a short, rectangular flight that covers only 10% to 15% of the material conveying area. This type of conveyor depends almost entirely on moving material en-masse.

McLean described the following items on a drag conveyor that need to be inspected and maintained regularly.

Bearings — Follow the manufacturer’s recommendations for proper lubrication per class of service.

Reducers and motors — Follow manufacturer’s recommendations.

Flights — Inspect flights to make sure that they have not been damaged or worn to the point that they allow the chain or attachments to rub on the bottom of the conveyor. "Steel-on-steel is not a good wear situation," McLean said. Damaged flights also can cause the shutdown of a conveyor by allowing the capacity of the material to drop enough to cause the conveyor to plug.

Chain take-up — Taking up the stretch in the chain is a normal procedure. In the first few months of the conveyor’s operation, check the chain monthly. After several months of operation, check it every six months to a year, depending on the class of service.

Chain wear — A visual inspection is not adequate to determine the amount of wear on the chain. Most of the wear is on the pins and internal bore of the block link, McLean said. During normal stretching and taking up of the chain, a piece of chain is usually removed. Place this piece of chain on a flat surface and try to move it side-to-side. New chain has little side-to-side movement, so the more your chain moves, the more wear it is showing.

Sprockets — Head and tail sprockets should be a part of the regular preventative maintenance inspection. Look at the profile of the teeth of the sprockets. When the sprockets start to wear, they will start to look like a hook. When the hook gets bad enough, the sprocket will grab the chain and shear the pin, breaking the chain.

Return system — Whether idlers sprockets or rails are used to return the chain and flights, both should be inspected regularly. There is no reason to replace the sprocket until it stops working, no matter how worn it looks. Also keep an eye on rail returns. Check the rails for wear, especially at the points where they join together. Rails that wear unevenly can damage the chain and flights.

Interior rust — A conveyor that sits for months at a time without operating can accumulate a healthy coat of rust on the interior of the trough. This rust will hamper the ability of the conveyor to handle material en-masse upon start-up. Break it in easy by following the same procedure used to start operating a new conveyor.

TIGHTEN YOUR BELT. Belt conveyors utilize endless rubber belts that move along supporting surfaces upon which bulk materials ride. Open belt conveyors often have safety and housekeeping issues. Enclosing the belt in a rectangular steel housing contains spills and airborne grain dust.

Most enclosed belt conveyors are equipped with reclaim systems that automatically reload spilled grain back onto the belt and have been designed with external bearings as a safety feature to reduce the risk of fire or an explosion.

Not to be confused with a "covered conventional conveyor," Hi Roller’s conveyor is designed to be totally enclosed, dust tight, and weather tight, with no internal brackets, ledges, or areas where material can build up, said Mike Spillum, sales manager.

Hi Roller uses a unique bell-shaped carrying idler, which provides the trough for the belt and utilizes two external bearings as opposed to the six internal bearings associated with a conventional idler. The bell-shaped idler also has built-in self-aligning characteristics for both single and bi-directional conveyors.

Hi Roller manufactures various versions of its enclosed belt conveyor, including one with a moveable tripper that is remote-controlled with a programmable logic controller. But the company designs all of its conveyors to be easily maintained, Spillum said.

"Great thought and customer input goes into the ongoing improvements in design and function of our conveyors," he said.

The terminal sections split at the shaft allow quick replacement of head and tail pulleys without the need to cut and re-splice the belt. Snub, tripper, and upbend pulleys are mounted in a framework that allows the complete assembly to be removed from the side of the conveyor. Two independent stub shafts are used to support the troughing idlers, which permits quick removal and replacement of bearings or idlers in confined spaces.

Spillum said to follow the manufacturer’s recommendation regarding lubrication and drive adjustments. He also suggested the following preventative maintenance checks:

Inspect carrying idlers — Worn paint at the junction of the 45-degree trough slope and the center tube of the idler is an indication of an undertensioned belt.

Inspect idler shafts — Check that setscrews are tight between the shaft and bearing and between the shaft and idler.

Inspect belt splice — Look at the carrying and underside of the belt.

Check belt tension — Follow manufacturer’s recommendations.

Inspect splice protector/wiper cleats — If these are worn or peeled back, eliminate ledges that they could catch on or wear on and replace the wiper cleat.

Inspect reloading flippers/vanes — Reloading flippers should be free of wear or build-up.

Inspect product contact areas — These include liners in impact areas and skirting at infeed areas.

Spillum also recommended regular inspections of the tail section. "A continuous stream of material returning to the tail is an indication of product spilling off the belt, carryover at the discharge or a damaged belt," he said.

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