Overhead Conveyors

An Overhead Conveyor System offers many advantages in terms of the ability to transport products, pieces or parts in unused plant spaces above the work area….come down to places needed for loading or unloading….handle heavy loads and odd shaped items….incorporate cleaning, painting, heat treating, baking, or similar operations….and can be easily modified if production needs change. Use the links below to skip to a specific topic on this page.

• Overhead Conveyor Types
• System Layout Information
• Chain Pull Calculation
• Drive Specifications
• Trolleys & Attachments
• Safety Devices
• Screen Guarding
• Pitfalls To Avoid
• Conveyor Electrical Controls and Control Panels

Overhead Conveyors are of three basic types:

• Free Systems with hand pushed trolleys available with a complete line of curves, brackets, switches, turntables, crossovers, lowerators, etc
•  Power Systems with chain, drive(s) and a complete line of horizontal and vertical curves, take-ups, attachments, load bars, safety devices, etc
•  Power and Free with chain, drive(s), trolleys with load bars, horizontal, and vertical curves, switches, take-ups, stops, etc

Overhead Conveyors have three basic capacities:

• Light Duty:    For 1 lb to 75 lbs per hook loading
• Medium Duty: For 75 lbs to 200 lbs per hook loading
• Heavy Duty:  For 200 lbs and 1200 lbs per hook loading
• (Note:  Load bars are available for each to increase hook loading)

Overhead Conveyors come in three basic styles:

• Round enclosed track, 1-5/8” &  2-3/8” diameter
• Rectangular enclosed track
• I-beam,  3”I,  4”I and  6”I

The following are some basic considerations to help you layout your system:

– Start with drawing a plan to scale of the building area in which the conveyor system  will be installed, showing all aisles, columns, obstructions, equipment, and areas to be considered. – Determine the type of load carried.

Consider the size and type of load to be carried and also the type of carrier or hook to be used.

– Then consider the total load to be carried on each trolley.  

This is an important factor in determining the size of the trolley, chain, track and drive to be used.

– Plan the material flow which involves the speed at which the conveyor will operate, and the spacing of   trolleys, carriers or hooks.  

The desired conveyor speed is calculated by taking the required number of parts per hour, multiplying this by the carrier spacing and dividing by 60 multiplied by the parts per carrier. Manual loading and unloading of an overhead conveyor is considered to be between 10 and 25 FPM.

– Consider the type of conditions under which the conveyor will operate.  

This includes temperature, paint and chemical conditions and the accessibility for lubrication or other factors which would have important bearing on the type of components to be used especially the kind of trolleys, turns and bearings.

– Choose the horizontal and vertical curves based on the size of load and desired carrier spacing.  

See tables A and B below for radii and trolley spacing minimums

– Be sure that the loads do not interfere with each other in curves by laying out the horizontal and  vertical curves and then laying in the loads. – Allow for one trolley spacing of straight track between horizontal and vertical changes to ensure proper chain alignment. – Try to place the drive in the high point in the system with the take-up in front of the drive preferably in the low point in the system, but close to the drive as possible.  

This will ensure that slack chain is pulled away from the drive chain.

– Figure the total chain pull by first calculating the weight of the product, carrier, chain and attachments on the entire system. 

The most practical thing to do is to provide an ample margin of safety in planning the chain and drive size.

– One means of figuring the total chain pull, particularly on simple systems involving only one drive is the Total Moving Load Method as described below:

The quick chain pull method for simple systems with one drive and no more than 18 changes in direction is: 

Calculate the total moving load and multiple this number by the friction factor from Table C. This will give you a quick chain pull to help choose a drive, system size, and type. To this figure you must add the vertical loads by adding and subtracting the up and down loads.  Multiply the vertical drop or rise by the number of pounds per foot and consider the worst conditions of loading.  Many times a load going up will be cancelled by a load going down.

Overhead Conveyor 180 Degree Take-Up Types:

Screw Spring Air

*Note*  

Take-Up travel is normally 8”, 12” or 16” and amount of chain that can be taken up is double the travel.

*Note*

 The “X” number designation of I-beam conveyors is a combination of the chain pitch (3”,4” or 6”) and the diameter of  the chain pin (.48”, .58”, or .68”)

Overhead Conveyor Trolleys:

Trolleys for overhead conveyor systems come in many styles and types depending on the application and cost. The brackets come in two styles:  

• Forged: where strength and rigidity are desired.
• Stamped: where economy is important and demands on the trolley are not too great.

The wheel connections come in two syles:  

• Swaged: most common due to low cost and strength
• Bolted: used where there is a need to replace wheels due to heavy loads and contaminant conditions.

There are two basic choices for trolley wheels:

• Retainer Type:  These are typically used in light or moderate load and low contaminate conditions such as transportation, parts delivery or assembly operations. The advantage is low friction, minimum ball wear, and the least drive energy.
•  Full Ball Type:  These are used for heavier loads and contaminant conditions.  Also,  they are use in high temperature conditions up to 500 degree F…retainer types have a maximum range of 325 degrees F.

(There are special types of wheels such as thermoplastic wheels designed to resist cleaning solutions available in 3” I)  

*Note*Wheels can be open or sealed depending on the application.

Overhead Conveyor Attachments:

Attachments for overhead trolleys come in many varied sizes and types depending on the application and load.

Load Bars:  designed to connect two trolley brackets designed to negotiate around horizontal and vertical curves without binding.   

3”I load bar:  6” hole centers……500 lbs capacity

4”I load bar:  8” hole centers…..1000 lbs capacity  

6”I load bar: 12” hole centers….2400 lbs capacity

1. H Attachments:(the most commonly used attachment)

• It is used to suspend almost any type of hook, tray or rack.
• They come in pairs and are bolted together between the trolley brackets.

2. B Attachments:  

• Normally used to support the load bar from a pair of trolleys but can be used for other applications.

3. C Attachments:  

• Are used when the carrier has a clevis.
• Can also be used with a bent rod hook to carry light loads.

4. I  or “Dummy” attachments:  

• Are used on intermediate or spacer trolleys that carry no load.

5. Indexing Swivels:   

• Come in many different styles in order to rotate your carrier or product.

		90 degree indexing swivel hook type with detents at 90 degrees…has a 125 lb capacity and is used on 3”I and 4”I systems.
		90 degree star wheel indexing swivel which makes contact with stops along the travel of the system to rotate the swivel….has a 125 lb capacity and is used on 3”I and 4”I systems

 

6. Rotary Rack Swivel hooks have a gear rack which provides positive turning action when engaged by a corresponding gear

 

7. Spinner hooks provide for continuous rotation when engaged by a fixed friction bar… Capacity is  50 lbs

 

8. Sanitary hooks which have a “C” yoke to be used with a sanitary pan under the conveyor rail and trolleys. This is one we designed for a specific project.

Overhead Conveyor Safety Devices:

Anti-backup “uphill” safety devices for vertical curves in the event of chain breakage to prevent chain runaway.

Anti-runaway “downhill” safety devices for vertical curves.  Involves a limit switch to cut the drive off and a mechanical device to stop the chain from running away in the case of chain breakage.

Screenguarding For Overhead Conveyors:

There are two basic styles to accommodate light, medium and heavy loads. These are used to provide protection from falling parts from the conveyor system.

Welded Wire Mesh Guarding:  This is used for most light and medium loads.  

• The mesh is normally 2” x 4” of welded rods.
• The sides and floor panels are joined with a steel helix. 
• Standard panel lengths are 96” (widths and sides vary)

Expanded Metal Guarding:  This type is for heavier loads and is fabricated from structural steel to fit the application (more expensive)

Pitfalls To Avoid With Overhead Conveyor Systems:

1. When a system is beginning to exhibit problems – one pitfall is to fail to look at lubrication and dirty conditions as the cause.   

2. When adding footage to a two drive system – one pitfall is to install new chain with old chain. 

10’ of new chain may be 10’-3” long on old chain due to stretch (wear) which means the new and old chains are different pitches. 200’ of new chain would be 205’ of old chain and when the new section rotates to the opposite side of the drives the 205’ will become 200’ and the system take-up on that side will not be able to handle it causing damage to  occur.

• It is not easy to do, but the new chain needs to be dispersed evenly in 20’ to 30’ sections evenly through out the system in order to minimize the pitch difference.

3. When replacing or adding new components to a 4”I system – one pitfall is to not realize that 4” I systems have two trolleys drops, 7-3/16” and 8”. 

Trolley drop is the distance from the top of the track to the centerline of the chain. The trolley drop for 3” I is 5-1/2” and the drop for 6” I is 10”.

• The problem comes when the wrong drop trolley comes to the drive….it will not go through.

4. When making up chain – one pitfall is to not use the manufacturers trolley nuts and bolts.

The nuts and bolts are special with thin line locking nuts and exact length bolts.

• The wrong length bolts or thicker nuts may not engage the drive and turns properly.