Integrated Pest Management Program Department of Plant Science and Landscape Architecture

UConn Extension

Materials Handling – Conveyors Everyone strives for labor efficiency, whether operating a greenhouse alone or with the help of many employees. Moving materials is one of the most labor-intensive jobs in the production of plants. Although carts are becoming more popular as a method of moving container plants, conveyors are more versatile in that it can quickly move cartons, bags, bales, bulk soil as well as plants. Many types of conveyors are used in greenhouse/nursery operations including belt, gravity, chain and auger.

Belt conveyors The belt conveyor consists of a belt that rides on a flat steel bed or set of rollers. It may have legs or may be designed to be placed directly on the floor. A gear motor is used to power the belt. This is usually variable speed to adapt to the materials that are handled. Some conveyors can operate in either direction to help with loading or unloading. Belt conveyors come in many styles and sizes. They can have a belt that is flat, troughed or with flights. For most horticultural uses, a light to medium duty unit will give good service. Widths of from 4 to 24 inches and lengths to 200 feet are available. One of the most popular types of conveyors is the multi-section conveyor. It is made up of one section with a drive unit and a number of additional modular sections that can be added to provide the desired length. These sections are connected together with gears or belts so that the power unit drives all the sections up to 200’ in length. These work well for moving pots from one bench to another when they need to be spaced or for loading plants onto a long truck bed. It takes about 5 to 10 minutes to set up a 75-foot unit.

Multi-section belt conveyor powered by a single gear motor

If bulk materials need to be handled, as when filling a potting machine, a belt conveyor can be fitted with flights or formed into a trough. This works well as long as the material is not too wet. Side rails and a hopper at the bottom can be added to increase capacity. If the conveyor is to be moved frequently, a carriage with pneumatic tires and a winch will make the job easier.

Belt conveyor fitted with flights to handle growing mix

A belt conveyor is often used for potting or transplanting operations. Filled containers are placed on one end of a slow-moving belt. Workers, standing or sitting beside the belt, stick plants as the container moves past. A variable-speed motor is needed to adjust the belt speed for different conditions. Production is usually greater than with most other methods because workers do not have to walk to get materials and the belt paces the worker to keep up with the constant flow of flats or pots. Working height of the top of belt for operating standing is 32 to 40 inches depending on height of container. Working height for operator sitting is 28 to 33 inches.

A combination of belt and roller conveyors can be used to speed transplanting In selecting a conveyor, consider the following:

Type of material – boxes, containers, bulk material - a flatbed should be selected for moving pots, flats and hanging baskets. A concaved bed should be selected for bulk materials.

Size of containers or rate of flow - the width should be adequate to support the container. Eight, 10 and 12” widths are common for handling pots, flats and small boxes. Soil and growing media is usually handled in 12” or 18” wide belts.

Weight of materials – flat bed for light loads, roller bed for heavy loads. Distance to be transported – lengths to 200 feet are available Vertical distance – up or down. Motor size may have to be increased for elevating

materials. Power unit – narrow, sectional conveyors to 100’ length are usually powered by a one

horsepower electric motor. This requires a 20 amp duplex electric outlet. For outdoor operation, a two to five horsepower gas engine is common.

Variable speed – this is desirable Belt material – a PVC cover over polyester monofilament plies provides good lateral

stability and excellent tracking and is used by most manufacturers. A rib may be incorporated as a guide to aid tracking. For soil and other bulk materials, a polyurethane material is used.

Support for the conveyor – multi-section conveyors are designed so that they can be set on the ground on the top of a bench. Legs can be added to raise it to working height. Wheels can be added to make a unit portable. Some growers have suspended sectional conveyors from overhead trusses or heating pipes.

Weight of conveyor sections – light-weight, multi-section conveyors are made from aluminum and weigh from 50 to 70 pounds. Steel conveyors weigh several hundred pounds and are usually mounted on wheels for transport.

Maintenance – frequent cleaning of soil and debris from rollers and belt surfaces is needed. Adjustment of belt tension and tracking may be required. Keep guards in place for safety. Purchase from a manufacturer that has repair parts readily available.

Accessories – side guides are used to keep containers from falling off the belt. Diverter bars are available to direct containers to different belts. Counters can be added to total production. Electric eyes are used to stop flow. Right angle powered roller sections are available for turns. Roller conveyors are often used for accumulating containers at the end of the belt. Hoppers are available to feed bulk materials to the belt.

Cost – used conveyors are often available from equipment suppliers or at auction. New conveyors cost varies based on the above design features but generally cost from $100 to $150/ linear foot.

Belt conveyors are a convenient tool to reduce labor and speed materials handling. Review your operations to see where they can fit in.

Gravity Conveyors Gravity conveyors are ideal for moving boxes, bales and flats either horizontally by manually pushing the material along, or sloped down using the force of gravity. To work well, the items to be moved must have smooth, flat bottoms or else be placed on a pallet or piece of plywood (slip-sheet). The original investment in gravity conveyors is a fraction of that required for most other material handling equipment. In addition, operating costs are low because power is not required. With the widespread use of gravity conveyors in many industries, used equipment is readily available. Types There are two basic types of gravity conveyors: wheel and roller. The rolling surface of a wheel conveyor is a series of small-diameter skate wheels supported by a metal frame. Light loads and items with solid bottoms work best on this conveyor. It is the preferred conveyor because of its lower cost, greater simplicity, lighter weight and easier portability. When moving heavier items, objects with recessed bottoms or wooden pallets, a roller conveyor should be used. Under certain situations, a powered roller conveyor may be needed. Rollers/wheels Spacing of the rollers or wheels is important. A rule of thumb is to provide a minimum of three rollers or wheel axles under the shortest item to be conveyed. This gives good support and avoids excess vibration. Standard spacing is 1½, 2, 2-1/2, 3, 4 and 6 inches. The closer the spacing the more expensive the conveyor becomes, but the smoother the operation. Smaller pots can be placed in a carrier tray for ease of handling and conveying. To calculate the roller or wheel spacing, divide the length of the object by 3 and then select the next size smaller. For example, a roller conveyor for handling 20-inch long flats should have a minimum roller spacing of 6” (20” / 3 = 6.7”). Load capacity also varies. Light-duty equipment is designed to carry articles up to 50 pounds. Medium-duty will carry items to 300 pounds. Slope The slope that a roller conveyor has to be placed varies with the weight and the smoothness and material of the item being conveyed. Table 1 lists suggested pitch for different materials.

Table 1. Roller conveyor slope* Container Weight (lbs.) Slope (in/ft.) Slope (in/10 ft.)

Flats 2-20 ½ 5

Boxes/cartons 50-75 ½ 5 Boxes/cartons 15-50 5/8 6-1/4

Boxes/cartons 5-15 ¾ 7-1/2 Boxes/cartons 1-5 7/8 8-3/4

Bale 60-75 1 10 *varies with smoothness of bottom and weight Roller and skate wheel conveyors can also be set up level. Materials such as flats are placed on the conveyor and then pushed manually as a unit. It saves time over hand carrying. Sizes Standard lengths are 5 and 10 feet per section. Sections can be hooked together to form any total length. When portability is needed, such as in temporary setups for moving plants into or out of a greenhouse or for unloading a truck, use a conveyor with an aluminum frame and plastic rollers or wheels. For horizontal runs, ball bearings work best for the rollers or wheels rather than sleeve bearings, which create more friction. Accessories that will make a permanent installation more versatile include curved sections, switches, carton stops, guides and turntables. Powered roller conveyors are available for use with heavy items. If you have a flat filler or potting machine, you may want to use a roller conveyor at the output end to accumulate the containers until they can be loaded onto a pallet or cart. This will help to smooth out the flow. Use for order assembly - One application of roller conveyors used by several growers is to hold plants for assembling orders in the shipping area. Plants brought from the growing area are loaded by varieties onto one end of a series of conveyors. Workers picking orders for delivery to garden centers take the plants off the other end. The conveyors act as a stocking area until the plants are needed. This system eliminates traveling to large area or number of greenhouses to assemble an order.

Chain Conveyor Select a chain conveyor for low-cost, heavy-duty moving of materials horizontally or between floors. They are also used in potting machines and bale breakers to move the soil vertically. The simplest system uses a single endless chain to carry pots from a potting machine to carts or trailers for transferring to the growing area. Sprockets power the chain, unlike rollers, which are used with belt conveyors. Rails along the side guide the pots and keep them from tipping. A double-chain unit is frequently used for flats. Multiple units are often attached together and powered by one drive unit.

Plastic chain conveyor carries flats through a subirrigation watering tunnel

Chain selection Several types of chain may be used. A detachable link chain is the least expensive, with a long wear life if used for moderate loads and at low speed. For higher loading or more speed, a pintle chain works better. It has fewer corrosion problems than the precision roller chain. Plastic chain is common on watering tunnels. All chain is available with attachments for flights or pushers.

By adding flights and a solid bottom, a chain conveyor becomes a low-cost device for conveying or elevating bulk materials. Frequently, manufacturers use chain conveyors, fitted with pans or potholders on their potting machines. Maintenance on chain conveyors is much less than on other types of conveyors because chain conveyors resist wear from soil and sand. In addition, they are not affected by high-moisture growing media.

Auger Conveyor Use an auger if you have to convey or elevate granular materials, such as growing mixes, peat, vermiculite, sawdust or chips (Fig. 7-37). Augers are preferred for these applications to other types of conveyors because of their simplicity, low cost, durability and versatility. Operation can continue at any angle. Size The delivery rates and power requirements of auger conveyors are affected by many things, including the conveyed material, angle of elevation, auger diameter, length, flight pitch and rotation speed. For most greenhouse applications a 6 or 8 inch-diameter auger works well if the material has a low moisture content. A 6 inch-diameter unit will handle up to 25 yards of mix per hour at a 45-degree angle. Power can be either an electric motor or a gasoline engine.

Applications Along with flat and pot fillers, augers are used to keep potting benches filled with mix. The inlet is fitted with a hopper or connected to a bin, and the mix is conveyed horizontally along the back of the potting bench. Spouts located over each bench allow the mix to flow out until the bench is full. Another application places an open auger on top of a bin to increase the volume of material that it will hold. When soil at the fill end builds up, the auger moves it to the other end until the entire bin is full. When higher moisture content material such as peat or soil mixes needs to be conveyed horizontally, a U-trough auger should be used. Various feed and discharge systems are available.

Overhead Monorail Conveyor This conveyor can be used to eliminate the time-consuming, backbreaking job of moving plants from the transplanting area to the growing area and on to the shipping area. One person can move 10 to 30 flats at a time. Trains can be assembled that will carry 100 flats or more. The system consists of tubular or angle track suspended from the greenhouse frame and a trolley-mounted rack that is pushed along manually. Suspending the track over the benches and plants means that no additional aisle space is needed. System cost is $3- $5/linear foot.

Low-cost monorail conveyor speeds plant handling

Carriers need to be sized to fit the greenhouse area and not be overloaded to affect the integrity of the greenhouse. A cart or carrier with 50 flats may weigh as much as 1000 lbs. Before

installing one, you should inspect the greenhouse frame carefully to see if it will carry the extra load. Curved sections of track can be used to get around corners. Switches may be positioned anywhere in the system to allow transfer from one track layout to another or to a storage area near a loading platform. Motorized conveyors are available, but these are more expensive. They use a chain or cable powered by a drive unit at one end and idlers at other direction changes. Take-up units are needed to keep the chain taut. There are many styles of hooks, clevises, load hangers and other attachments possible. Vertical movement between floors is possible. Speed can be fixed or variable. Motorized conveyors are used in packing areas for roses, bulbs and growing mixes that may be placed in bags or boxes.

Cable Conveyor This is a low-cost system consisting of steel cables supported by rollers the move plants horizontally. A gear motor, located at one-end powers the drive shaft. An idler shaft at the other end keeps the cables taut. Cables are spaced about 4 in. apart to support the flats. Idler rollers are spaced about 12’ apart to prevent sag of the cable. This type conveyor is usually built in place along one wall of the greenhouse next to an aisle.

Cable conveyor carries flats in or out of greenhouse

Hanging basket conveyor A system for supporting hanging baskets has become popular as it can provide significant increase in plant production. One to three levels of plants spaced as close as 8” apart can be supported from hangers attached to the cable. Plants moves past work and watering stations at the end of the system. The convenience of having the plants brought to the end of the

greenhouse for inspection and shipping can offset the cost of the system. Because plants change location, they are exposed to more uniform daily light enhancing growth. Plants underneath the cable system will receive less light so careful plant selection is necessary. Fixed or variable speed operation is available. A controller is available to operate multiple systems allowing scheduled watering depending on type and age of plants, and weather conditions. Cost for the system is approximately $2/sq. ft.

Hanging basket conveyor can support up to three levels of pots

Gantry A gantry is a beam, truss or frame that is supported by wheels on rails on both ends and spans over a bay of plants. The frame can support a misting or watering system, transplanting equipment, photoperiodic lighting, sprayer, conveyor or other equipment. Aisle space normally used for working and walking is eliminated, maximizing the production area. Where ground crops are grown, soil is not compacted. Support for the gantry is usually a set of rails attached to the post line or the sides of the greenhouse. Height depends on whether the crop is located on the ground or on benches. For ground crops, a height of 20” is common. Rails can be channel iron, pipe or extruded aluminum. Square tubing has been found to work well as it is easy to attach to supports and provides more tractive surface than round pipe or tubing. In some greenhouses, heat pipes are installed to serve as the rail. Wheels can be free rolling as for a hand pushed gantry or powered. Powered wheels may have a rubber surface to increase traction. Wheels that engage one rail are usually fixed. The opposite wheels that ride the other rail need to be adjustable to follow any rail variations. Gantries can also be supported on wheels that ride on concrete walkways along the sides of a greenhouse. These are more expensive to build as individual wheels have to be powered but can be moved from bay to bay as each wheel can be steerable.

Gantries can be pushed by hand or powered by hand crank, battery, electric motor or internal combustion engine. A lightweight gantry used for moving plants can be easily pushed by hand on steel rails. If used for inspection of plants, a hand-powered unit may be sufficient. When spraying equipment, rotary tiller or harvestor is attached, a powered unit is better. One wheel on both rails should be powered to keep the gantry from crabbing. Battery power, two 12-volt batteries, will power a gantry with spray or irrigation equipment attached for about 8 hours of operation. Variable speed motors or V-belt speed changers allow adjustment of movement from 5 ft. /min for planting or harvesting to 300 ft. /min for spraying or transport. Electric motors are more difficult to power as a cable has to be pulled along. For outdoor operation, gasoline engines are frequently used. They can also power accessory equipment such as a rotary cultivator, transplanter or lettuce harvestor. Gas engines should not be used in an enclosed area such as a greenhouse. Due to the cost, gantries can be built to be transferable between individual greenhouses or bays in a gutter-connected greenhouse. Lightweight units are frequently moved on a simple two-wheeled handcart. Heavier units can be moved on a four-wheel wagon or by installing rails connecting one area with another.

Gantry conveyor can carry plants, irrigation and lighting systems

John W. Bartok, Jr., Extension Professor Emeritus & Agricultural Engineer, Department of Natural Resources and the Environment, University of Connecticut, Storrs CT - 2018 Disclaimer for Fact Sheets: The information in this document is for educational purposes only. The recommendations contained are based on the

best available knowledge at the time of publication. Any reference to commercial products, trade or brand names is for information only, and no

endorsement or approval is intended. UConn Extension does not guarantee or warrant the standard of any product referenced or imply approval

of the product to the exclusion of others which also may be available. The University of Connecticut, UConn Extension, College of Agriculture,

Health and Natural Resources is an equal opportunity program provider and employer.