Introduction

A successful Zig-Zag conveyor installation is largely the product of an orderly sequence of steps. The steps, as shown below and expanded on in the following links, will provide the application engineer with the data needed to produce the desired result.

Step 1: Assemble Job Information

The following data must be in hand prior to proceeding with the other three steps:

DESIGN DATA:

1. Description of conveyor function that includes all processes from load to unload.
2. Size and weight of product or products to be transported. It is desirable to obtain exact product weights rather than customer estimates.
3. Quantity of products loaded onto conveyor?
4. How is product carried?
5. Is it intended to carry more than one part or product per carrier?
6. Is drawing of proposed system available?
7. Are building drawings available?
8. Is the system to be ceiling supported or floor supported?
9. If items indicated in #6 and #7 are not obtainable, a sketch must be made at the site. This is to include column centers (locations), building headers (size, location and height), and location of conveyor in relation to the building, load points, unload points, washers, ovens, spray booths, etc.
10. What are the temperatures the conveyor must accommodate?
11. Is conveyor to be subjected to contamination by powder coating, acids, abrasive, etc.?
12. Are explosive proof motors required?
13. What are the electrical characteristics?

QUOTATION DATA:

• Is a firm or budget price required?
• How soon must quotation be presented?
• What are delivery requirements?
• Method of delivery: Air Freight? Motor Freight? Rail Freight? Customer pick up?
• Is shipment to be prepaid and invoiced or shipped freight collect?
• Are electrical controls to be included? If so, please provide a description of what to include.
• Is mechanical/electrical/pneumatic field installation required?
• If field installation is to be quoted, will welding of supports to building steel be permitted or must clamps be used?
• Will owner clear the area except for fixed items such as machinery, etc.?

Step 2: Conveyor Component Data

Prior to starting design of the system, it would be well to become acquainted with the various standard conveyor components, their applications, functions and limitations. This knowledge will be of great assistance to the application engineer.

TRACK – TR-471 & TR-804

TR-471 is available in 10'-0" lengths only and formed from 3/16" pickled and oiled steel sheet with tan paint finish.

Capacity: Maximum of 130 lbs. per foot with supports on 10'-0" centers.

TR-804 is available in 10'-0" lengths only and formed from 11 ga. pickled and oiled sheet steel with tan paint finish.

Capacity: Maximum of 75 lbs. per foot with supports on 10'-0" centers.

The inside dimensions of the TR-804 track are identical to those of the TR-471 track.

HORIZONTAL & VERTICAL CURVES

All track curves are made of 3/16" hot rolled, pickled and oiled sheet steel.

All changes in direction of the track, either horizontal or vertical, must be made with a curved section. While most stock curves are made in 45° and 90° radii, any degree turn may be accomplished by field cutting and/or welding together of stock curves.

There are two principle considerations governing the selection of curves; product clearance and chain pull of the system (either 400 lb. or 600 lb.).

Relative to product clearance, it is often necessary to use curves with radii larger than 2'-0" to provide close product centers on the straight conveyor while still having clearance at the horizontal and vertical curves.

The chain pull of a given system will determine whether heat treated or untreated curves are required. Heat treated curves are required in all 600 lb. systems where the horizontal or vertical curve radii is 2'-0" to 3'-0". Curves 3'-0" radii and larger need not be heat treated.

Hardened curves are necessary in the 2'-0" to 3'-0" radii range because of the load imposed on the track by the conveyor chain wheels at 600 lbs. of chain pull. In a straight section of track, the wheel load is equal to only the sum of chain link, pendant, hook and product weights. When the track is bent or curved, the chain wheels have an additional radial load at the curved section as a result of the chain tension. At 400 lbs. of tension and 2'-0"R the wheel load resulting from tension is only 100 lbs. At 600 lbs. of tension the wheel load is 150 lbs. This diminishes in direct proportion to the increase in the curve radius as follows:

600 lb. chain tension and 2'-0"R wheel loading = 150 lbs.

600 lb. chain tension and 2'-3"R wheel loading = 133 lbs.

600 lb. chain tension and 2'-6"R wheel loading = 120 lbs.

600 lb. chain tension and 3'-0"R wheel loading = 100 lbs.

As evident, the limiting factor is the track, rather than the chain wheels. Therefore, if the wheel loading, as a result of chain tension, exceeds 100 lbs., hardened curves must be used. If the 100 lb. loading is exceeded with un-heat-treated curves, failure will occur as a result of peening of the track wear surface. The peening action removes metal in the form of flakes or slivers until the metal is too thin to resist the wheel load. This is most apparent at the track lips of the top vertical curves. With an overloaded condition, the lips will deform or roll downward until the chain finally emerges from the track.

The minimum radius for any track curve is 2'-0". The limitation is imposed of wheel loading and clearance of the vertical chain wheels at the inside wall of the horizontal curves. At 2'-0"R, the wheel clears, but at 1'-6"R the wheel faces bear on the track wall to increase the friction and drastically elevate the chain pull.

If it is necessary to use less than a 2'-0"R horizontal curve, as required in many oven applications, 24", 30" and 36" diameter traction wheel turns are available from stock. The traction wheel carries the chain around the curve as opposed to the chain wheels rolling around a track curve. Consequently, there is no peening action.

Bottom vertical traction wheel turns of 24", 30" and 36" diameter are also available on special order. However, top vertical traction wheel turns are not adaptable since the wheel face would interfere with the chain pendants, carriers and products.

All 600 lb. curves are identified by a yellow label and letter "H" stamped on one end. The 400 lb. curves have red labels.

CONVEYOR CHAIN – CH-1974

CH-1974 Chain is all steel construction, natural finish, 600 lb. chain pull capacity, 450°F maximum operating temperature, ball bearing vertical and lateral wheels and a maximum load capacity of 75 lbs. @ 6" centers.

Conveyor chain is the most important item in a system, and every effort must be made to guard against those elements which are harmful.

The 450°F (232°C) operating temperature is maximum. If this is exceeded, hardness is reduced in certain critical parts, and chain life is greatly reduced.

Exceeding the recommended chain pull accelerates chain wear and is injurious to chain wheel bearings, track curves and drive units.

Exposure to acidic solutions, corrosive vapors and liquids removes lubrications, corrodes bearings, pin joints, etc., which effectively shortens the useful life of the chain.

Abrasive laden air, such as in foundry and sand blast applications, are particularly injurious.

Vapor degreasers are often designed to allow the vapor level to extend above the conveyors. The chain is then completely stripped of lubricant of each complete circuit. An automatic mist spray oiler can be installed just "down stream" from the degreaser, but it is difficult to apply a sufficient amount of oil in just one pass. Rapid wear and short chain life is the result of inadequate lubrication.

Most of the above problems may be overcome by installing a "Protective system." However, if in doubt, consult the factory.

All conveyor chain is sold in 10'-0" coils only. Each coil is coated with a preservative prior to placing in individual cartons.

Pendant spacing is usually dependant on load clearance at the horizontal and vertical curves. This is discussed in "Step 3, System Design" section.

TAKE-UP FITTINGS

The take-up fittings are so designed because the unit includes only the two take-up sleeve assemblies, two support track sections, two hangers and two brackets. The curves, in which the radii may vary greatly, are not included.

One take-up is required for each system at a 180° track turn. The take-up sleeves are always installed parallel and usually 4'-0" apart on the centers. However, wider take-ups may be used to suit job conditions. If the take-up sleeves are to be spaced more than 14'-0" apart, additional support tracks and hangers must be provided.

The primary purpose of the take-up is to provide an easy method of keeping chain slack at a minimum. The chain develops slack or loosens as a result of normal wear in the various joints. This condition is first apparent at the "down stream" end of the drive unit or at the bottom of the first decline beyond the drive. The 18" adjustment in the take-up sleeves permits a number of movements before it is fully extended, and approximately 36" of chain can be removed from the system.

Two types of take-ups are offered. The screw type is preferred where the conveyor is not exposed to any appreciable variation in operating temperatures and in those cases where a track decline is located just "down stream" from the drive unit, it is necessary to prevent loose chain from accumulating at the outgoing end of the drive. The chain telescopes as it becomes slack, thereby moving the conveyor chain back into the caterpillar drive chain. This, in turn, prevents the Caterpillar dogs from releasing the chain links easily. Considerable noise is created, and the drive will eventually jam.

Automatic type take-ups are advisable where operating temperatures are extreme. A good example is an oven. At 450°F, an oven chain length of 300'-0" would expand or grow about 13". Therefore if all slack is removed from the chain at 70°F, it would be too loose when the oven reached 450°F. If a screw take-up is used and adjusted when the oven is a 450°F, the chain would then be under abnormal tension as the oven cooled to 70°F. Contraction would shorten the chain length to cause damage as a result of abnormal tension. The automatic type take-up will accommodate the variation and also maintain a constant chain tension.

In a level or monoplane system, the chain will gather or accumulate at the outgoing end of the drive, unless an automatic take-up is used.

Automatic take-ups are available in either spring or air cylinder types. Either will function properly. The air cylinder take-up, while more expensive, is capable of maintaining a constant chain tension as opposed to the spring unit which decreases tension as the springs are extended. automatic take-ups are available only as fully framed units, not as "fittings."

INSPECTION SECTION – TR-820

The inspection section, made from standard 3/16" track, facilitates inspection and maintenance at points other than the drive unit. It may be placed in any straight run of track. The section is made with the top and sides of the track open down to the center of the chain. This allows for full inspection of the chain for proper lubrication, chain tension and general condition of the conveyor chain. The opening is covered with a removable housing and is equipped with a handle. The inspection section also permits easy installation and removal of chain. The most desirable location is at the lowest spot between the output of the drive unit and the take-up.

EXPANSION SLEEVE – TU-1114

This device is intended for use in areas where temperature extremes are encountered and where no provision is made to accommodate expansion and contraction. Some ovens have an expansion joint at the mid-point. In such installations, an expansion sleeve should be installed in each conveyor track in line with the oven expansion joint. Uni-construction ovens do not have an expansion joint. Therefore, the expansion sleeves are not necessary. However, good conveyor practice dictates that the track in the oven be suspended from BR-1912 brackets, which will allow for some track movement throughout the temperature range.

LUBRICATORS – LU-664, LU-669 & LU-2724

Proper lubrication greatly extends the useful life of the conveyor chain. Consequently, the best lubricator available is recommended.

For ease of maintenance, the oiler should be located at the lowest track elevation. It is also recommended they be installed near the exit of an oven. Ovens tend to effectively decrease the amount of lubricant on conveyor chain which, in return, increases wear.

If drainage is objectionable, the oiler may then be placed in the return line or in an unloaded section of the conveyor.

As indicated in the section covering conveyor chain, lubrication is one of the most important considerations as far as conveyor chain life.

The choice of lubricant is governed partly by the application. Therefore, the user is obligated to consult his supplier for proper oil, based on the conditions to be encountered. In seeking this recommendation, attention must be given to temperature and the general operating environment. Ordinary petroleum derivatives leave a carbon residue when subjected to high temperatures. This is very harmful to chain wheel bearings. A high-temp synthetic type lubricant is suggested. In situations where the conveyor is exposed to high humidity, the oil should also contain a residue-free rust inhibitor. Moreover, the ideal oil in all circumstances should have a penetrate to carry the lubricant to all chain parts. The latter is especially beneficial when used with brush type lubricators.

If Molybdenum Disulfide based oils are used, the supplier must provide assurance that the "Moly" particles will stay in suspension and not settle out to clog tubes, brushes, orifices, etc. SAE #10 to #15 weight oil is best suited to all brush lubricators.

The LU-669 electro-brush oiler is a self contained unit. The oil flow is by gravity. The solenoid valve, which may be tied into the motor starting circuit, is opened when the conveyor starts and closed when it stops. There is an adjustment to regulate the oil flow. The brush type applicator depends on capillary action to flow the lubricant over all chain parts. In many situations, this lubrication is adequate, provided that some oil drainage is not objectionable. While the oiler operates only when the conveyor is running or when a timer permits it to do so, the lubricant will continue to bleed out of the brush for a period of time. This situation could be corrected by interrupting the oil flow some time prior to stopping the conveyor.

The LU-664 oiler is much the same as the Electro-Brush lubricators except that the oil flow is controlled by an "on-off" toggle at the top of the reservoir. It must be manually turned on and off. In certain applications it is adequate, providing that the user is careful to operate it often enough to thoroughly lubricate the chain.

The LU-2724 automatic PLC controlled lubricator is designed to precisely lubricate the critical bearing points of the conveyor chain. The lubricator has five nozzles, strategically located to dispense lubricant in the vertical and lateral wheel bearings along with the vertical link pin and roller. Each nozzle has its own adjustable valve to control the amount of lubricant that is dispensed. The lubricator is controlled by a small "Programmable Relay" inside the electrical panel. The control can be set for specific "ON" (Lubricating) and "OFF" (Non Lubricating) revolutions of the conveyor chain. Air inlet pipe size is 1/4" N.P.T. and a minimum of 60 psi is required for the lubricator to function with up to 30 weight lubricants. 110-130VAC, 50/60 Hz, 1 amp service is required for operation.

DRIVE UNITS

A wide variety of drive units is offered from factory stock to accommodate almost any system. Selection of the proper unit is relatively simple when the chain pull, conveyor speed and speed variation, if any, is known.

Variable conveyor speed is often times a requirement in systems involving washers, paint booth, dip tanks and ovens. In certain other installations, a fixed or constant speed is acceptable.

Multiple drive units must be used when conveyor chain pull exceeds 600 lbs. They must be located from chain pull calculations. The conveyor drive units must be located to have theoretical loading within 10% of one another.

SPEED FORMULA

FPM = (RPM/Gear Ratio) x (# of Teeth on Small Sprocket/# of Teeth on Large Sprocket) x (1.5)

RPM = Rotations per minute on motor

Gear Ratio = Ratio of gears on reducer

The 1.5 factor relates to the distance traveled for each revolution of the caterpillar drive sprockets which have 12 teeth x 1 1/2" pitch = 18" or 1.5 feet.

PENDANTS

A single 75 lb. capacity pendant may be attached to the chain on 6" centers. The double suspension pendants are attached at two points, 6" apart. This then allows loads of 150 lbs. on 12" centers. Multiple suspension pendants are attached at four points, each 6” apart. This then allows loads of 300 lbs. on 24” centers

WELDING JIG – TR-155

Straight track and curves in most systems are joined together by welding the joints. The welding jig, which is installed inside the track astride the joint, serves two purposes. It aligns the two ends when adjusted and the brass jig facing, at either side, prevents the weld flash from extending past the inner track walls. Without the jig, the weld flashes would cause a track obstruction which would be very difficult and costly to remove. While the device may be reused a number of times, repeated use does erode the brass facings. Therefore, it is recommended that at least the welding jigs are supplied with each system of 500 feet or less.

Step 3: System Design

PRODUCT HOOK OR CARRIER DESIGN

The system design must start with a device for supporting the product from the conveyor. Usually, the end user will specify the position in which he would like the product suspended. The processing equipment through which the conveyor passes will tend to influence the type of product hook required. The carrier assembly drawing also provides valuable dimensional information for the washer, spray booth and oven manufacturers as well as determining track elevations at conveyor crossovers and interference points such as pipes, ducts, etc. The carrier assembly layout is also used to fix the conveyor height at the load and unload points. To reduce operator fatigue in handling, the center of the product should be about 3'-6" from the floor if applicable.

LOAD CLEARANCE

Next in importance is the determination of load spacing on the conveyor. In most instances the user prefers minimum load centers for full utilization of all equipment. This is especially true in paint finishing systems where close product spacing is mandatory to minimize the size of the paint bake oven.

In Figure #1, a 180° horizontal 2'-0"R track curve is shown with loads placed on 24" centers. It will be seen that at the closest point there is a clearance of approximately 4". If the loads were moved 6” closer together, or 18" apart, there would be a load interference as shown in Figure #2.

Figure #1 | Figure #2

In Figure #3 a side elevation of a track incline is shown. It will be seen that the 24" load centers do allow sufficient clearance.

Figure #3

SYSTEM LAYOUT

Resolution of the product carrier design and load spacing clears the way for the system layout, providing all information is at hand.

Be sure to locate building columns since this fixes the location of the conveyor system with respect to the building. It is only necessary to show only that portion of the building in which the conveyor is to be located.

Next in order, washers, spray booths, ovens and other equipment to be tied together by the conveyor are drawn in to scale and should be shown in phantom lines. Phantom lines merely indicate that equipment shown thus is not included in the conveyor sales proposal.

The conveyor may now be sketched in heavy lines, starting at the load point. (See Figure #5) and continuing on through the washer, dry off oven, spray booths, oven cool down area and on to the unload area.

INCLINES AND DECLINES

Next, the inclines and declines are shown to indicate elevation changes. It will be noted that track rises or dips, in plan view are shown as a heavy line at either side of the track line with the track elevations noted at top and bottom. In Figure #4, it will be seen that for a rise of 6'-0" @ 45°, the overall length is approximately 7’-8". This dimension may be determined by calculation, a scaled layout such as Figure #4, or it may be found in the Zig-Zag catalog chart. In any case, all elevation changes must be located on the drawing to scale.

Figure #4

Step 4: Chain Pull Calculation

WHAT IS CHAIN PULL?

Chain pull is the effort necessary to maintain the normal operating speed of a conveyor under a related load. To arrive at this figure, it is necessary to add the lift load and the friction factors, expressed as a small percentage of the live load, which act as resistance to the progress of the conveyor. Friction resistance is found in the bearings of the chain wheels, curves, and the drive unit itself. It should be noted that these percentages are for average conveyors that travel under normal conditions. When adverse environment conditions exist or the conveyor is abnormally long or complex and exceeds the chain pull capacity of one drive, a progressive chain pull computation is necessary where the friction losses are progressively calculated and accumulated through the path along the conveyor.

There are few, if any, short cuts in the process of determining the chain pull on an endless chain conveyor. Many factors, which vary greatly from system to system, influence the end result. Product carrier weight, product weight, coefficient of friction, track curves, inclines, declines, temperature and lubrication are some of the principle items affecting chain pull. However, by knowing the value of the various factors, the total chain pull may be determined by the point to point accumulation method of calculation.

ZIG-ZAG FRICTION FACTORS

The above friction factors were obtained from accurate laboratory tests with lubricated chain and have been verified by dynamometer tests of complete systems.

It will be seen that straight conveyor has a friction factor of 1.50%. Therefore, if a conveyor did not have any vertical or horizontal curves, inclines or declines, the weight of the total live or moving load could be multiplied by 1.50% to determine the weight in pounds to move the conveyor. For instance, a 100'-0" conveyor with 1.5 lb. hooks and 6 lb. loads on 1'-0" centers would be 10 lbs. per foot (including chain @ 2.5 lbs. per foot) x 100'-0" or 1000 lbs. @ 1.50% = 15 lbs. chain pull. However, an endless conveyor chain must at least have horizontal curves, and each of these generate additional forces which must be taken into account as will be seen in Figure #1.

CHAIN PULL CALCULATION FOR A LEVEL SYSTEM

In Figure #1 a simple system about 115'-0" long is shown with four horizontal curves. The first item to be determined is the pounds in chain pull per foot of straight conveyor. The following formula provides a result of .45 pounds per foot.

Figure #1

= 30.5 lbs. per foot x 1.50% = .4575 lbs./ft. chain pull

In the following computation, it will be seen that the footage from the down stream end of the drive to the far tangent of the next curve (0 to 1) is multiplied by .45 lbs. and the 2% friction for the 90° curve is added. Next, the footage from (1) to (2) is multiplied by .45 lbs., added to the 3.08 lb. resultant plus 2% for the 90° curve. The procedure of accumulating at each curve is followed back to "0".

CHAIN PULL CALCULATION FOR A MULTI-LEVEL SYSTEM

Introduction of inclines and declines in a system further complicates chain pull calculation by adding to the forces. In Figure #2, a conveyor is shown identical to Figure #1 except for the addition of an incline and decline. Due to the elevations changes, the formula for finding the pounds per foot chain pull is arranged differently because it must be assumed that at some point the incline will be loaded and the decline empty. In systems having multiple rises and falls, this may be treated somewhat differently, depending on loading patterns.

Figure #2

When the loads are spaced under 2'-0" on centers, the formula of the total pounds per foot multiplied by the rise in feet can be used to determine the additional force in pounds for the inclined section. This can be seen in the chain pull calculation for the conveyor in Figure #2 from point #3 to #4. It is expressed as (6’-0” x 30 lbs./ft.) or 180 lbs. as the additional force induced by the rise.

In situations where the loads are more than 2'-0" on centers, a more accurate result can be achieved by multiplying the total live load on the inclined portion by the sine of the angle of incline. It will be seen that a maximum of four loads can be on the incline at any one time.

Trigonometry can provide the sine of any angle, but the following angles of slope are most used.

Figure #4

SHORT CUT METHOD OF CHAIN PULL CALCULATION (Approximation Only)

Using a 2.50% friction factor for the short cut method will cover most normal conditions. A large number of vertical and horizontal curves will create slightly higher friction.

CAUTION:

If calculated chain pull using this short cut method is in excess of 550 pounds per drive, you must use the long point-to-point accumulation method of calculation.

STEP #1: DETERMINE QUANTITY OF CARRIERS

The required number of carriers is equal to the total conveyor length divided by the carrier spacing.

STEP #2: DETERMINE QUANTITY OF LOADED AND UNLOADED CARRIERS

Establish distance from loading to unloading. Divide this distance by carrier spacing to determine number of loaded carriers.

STEP #3: DETERMINE LIVE LOAD

The live load on a conveyor is equal to the sum of weights of the chain, pendants, product hook or carrier, and the product.

A. Multiply weight of the chain (3.0 lbs.) by the number of feet of chain.
B. Multiply weight of pendants by required number of total pendants in system.
C. Multiply weight of empty product hooks or carriers by total number of carriers in system.
D. Multiply weight of product only by number of loaded carriers only as determined in Step #2.
E. Total of A, B, C, D = total live load on the conveyor system.

STEP #4 DETERMINE LIFT LOAD

The lift load is the amount of force required to pull the live load upward along the vertical curves in the entire system.

To calculate this force, determine the difference in elevation of all the vertical curves traveling upward in the system. The net vertical rise (in feet) will be considered the total lifting height of the conveyor.

The lift load for the elevation changes of the conveyor is equal to the total lift height (in feet) multiplied by the individual product weight (in pounds), then divided by the load spacing centers in feet.

STEP #5: DETERMINE THE CHAIN PULL

To determine the chain pull due to friction, multiply total moving load by selected friction factor.

A. Multiply total live load from (E) in Step #3 by friction factor of .025.

B. Add lift load obtained in Step #4 to (A) to obtain total chain pull.