Technical Information

Belting Technical Information

Flat Wire Belt Materials

Galvanized low carbon steel (C1015)

  • Most common flat wire belt material
  • Used because of low cost and some resistance to rust
  • Can be used in temperatures up to 500° Fahrenheit, although usually limited to 350° as galvanizing will flake off above this temperature

High carbon steel (C1050)

  • Used in the 350° to 800° Fahrenheit range for dry, non-corrosive environments
  • Provides for higher strength at elevated temperatures
  • Has a greater resistance to abrasion than C1015

Type 304 stainless steel (T-304)

  • Standard material used in food processing industry
  • Highly resistant to most corrosive atmospheres
  • Can be used in temperatures up to 1100° Fahrenheit
  • Corrosive resistance may be lost at temperatures above 800° Fahrenheit

Type 316L stainless steel (T-316L)

  • More resistant than T-304 to sulfuric, acetic, and phosphoric acids
  • Stronger and offers greater resistance to corrosion at higher temperatures

Type 201 stainless steel (T-201)

  • Highly resistant to most corrosive atmospheres
  • Can be used in temperatures up to 800° Fahrenheit
  • Extra strength due to slight work hardening

Belt Wrap

Keystone recommends that the maximum belt wrap on drive sprockets be limited to 150o. Belt wrap of more than 150o could resist releasing from the sprocket and continue a full revolution around the sprocket, damaging the belt. For tail sprockets, the maximum wrap is not as critical, but should be limited to 180° or less.

Belt Identification Process

In order to identify a belt for replacement:
  1. Measure the overall belt width, including the rods.
  2. Count the number of openings across the width of the belt.
    * This will always be an odd number.
  3. Determine the belt gauge (standard duty or heavy duty).
    a) Determine the height of the strip by placing the belt flat on a table and measuring from the table to the top of the belt.
    * A standard duty belt will measure 3/8" and a heavy duty belt will measure 1/2"
        OR
    b) Measure the diameter of the connecting rod.
    * Standard duty rods can be 0.105" or 0.120" and heavy duty rods are 0.192"
  4. Measure the longitudinal pitch of the belt, as shown.
  1. Determine the selvage of the belt by visual inspection.
    * This will be either clinched or welded, as shown.
  2. Determine the belt material.
    * Because stainless steels are not magnetic, a magnet can narrow the choice to either a carbon or a stainless steel.
    * Beyond this, material determination can be done by application. For more information about belt materials, see section above.

DRIVE TENSION CALCULATIONS FOR STRAIGHT RUNNING BELTS

(consult factory for TURN BELTS)

Important

  • Drive tension is used to determine the maximum load a belt can handle without premature fatigue and failure.
  • Consult Keystone for application assistance when approaching the maximum tension or for complex systems, as well as for the maximum number of sprockets that can be used for a given belt width.
  • The fi gures for the maximum allowable tension are given for drum-driven applications. In order for the belt to withstand these tensions with a sprocket-driven system, it is necessary to place a sprocket in every drive opening.

Use the following equation for rough calculations. This calculation CANNOT be used for Key-Turn belts.

  1. Determine the drive tension (Td) as shown below:
    Td = (F x B x L) (2WB + WL)
    Where:
    Td = Drive Tension (lbs.)
    WB = Weight of Belt (lbs/ft2)
    WL = Weight of Load on Belt (lbs/ft2)
    F = Friction Factor (see Table, below)
    B = Belt Width (ft.)
    L = Conveyor Length (ft.) (1/2 the belt length)
  2. Calculate the drive tension per foot of belt width by dividing Td by the belt width (B).
  3. If using the belt at an elevated temperature, multiply the maximum allowable tension per foot of width (given in the conveyor specifi cations tables, pages 2-6), by a factor from the table below to get the working tension at an elevated temperature.
  4. Compare the calculated value from step 2 with the maximum allowable tension found in step 3. The calculated value cannot exceed the maximum allowable tension.

ELEVATED TEMPERATURE (F) vs. STRENGTH

  500 600 700 800 900 1000 1200 1400
Galvanized
Low Carbon
1.0 N/A  
C1050
High Carbon
1.0 1.0 0.9 0.3 N/A  
T-201
Stainless Steel
1.0 1.0 1.0 0.65 N/A  
T-304
Stainless Steel
1.0 1.0 1.0 0.8 0.75 0.7 0.5 N/A
T-316
Stainless Steel
1.0 1.0 1.0 0.85 0.8 0.75 0.65 0.5

FRICTION FACTORS BETWEEN BELT & BELT SUPPORT

Belt Support Friction Factor
Ball Bearing Rollers 0.10
Sleeve Bearing Rollers 0.15
Plastics Faced Slider Bed 0.20
Steel Slider Bed - Lubricated 0.30
Steel Slider Bed - Unlubricated 0.35

Sprocket Selection

To calculate the minimum number of drive sprockets for a conveyor system:
  1. Divide the drive tension (Td) by the maximum load per sprocket (see table).
  2. Divide the belt width (B), in inches, by 6 and add 1.

The larger of the two numbers is the minimum number of sprockets needed.

Spacing of tail or idler sprockets should be between 6" and 9".

Never exceed a drive sprocket spacing of 6 inches, even for light loads.
Conveyor Belt
 
Maximum Pounds of Drive
Tension per Sprocket
Standard Duty Belts 1 Sprocket for every 70 lbs
Heavy Duty Belts 1 Sprocket for every 190 lbs
Decrease the maximum loading per sprocket for elevated temperatures using the table above.
 
Sprocket Type Maximum Belt Speed
Cast Sprockets 120 fpm
Machined Tooth Sprockets 250 fpm

Internal Welds


All welded selvage belts over 24 inches in width feature the resistance welding of every other connector rod to the flat strip on the 2nd opening in from each edge of the belt. On True 1/2" x 1/2" mesh belts this weld is on every 3rd connector rod.

This provides for greater strength and eliminates belt shrinkage under heavy loads without restricting flexibility of the belt.

Upon special request, belts 24" and under can be supplied with internal welds.

COMPARISON OF FULL SCALE FLAT STRIP & ROD SIZES


Belt Tracking

The belt length to width ratio should be no less than 5:1 as tracking problems are more likely to occur with wide belts which have a short length. Using alignment guides on the edges of a flat wire belt can cause premature wear.

Since the majority of belting problems are alignment related, it is extremely important to have all shafts parallel to each other and perpendicular to the conveyor bed. If a good alignment is not completed before using a flat wire belt, longitudinal pitch can be distorted causing the belt to track to one side. Improper handling of the belt before and during installation can also damage the belt creating alignment problems.

The best way to track a flat wire belt is to use several adjustable support rolls located on the return side of the conveyor just before the tail shaft. These rolls are skewed either forward or backward, on a horizontal plane, to track the belt.

Belt Assembly

Belts are supplied with an additional connector rod for each 10 feet of belting. To splice sections, or to create an endless belt, bring the two ends of the belt together and insert a connector rod. Standard duty, clinched selvage connector rods are supplied with a preformed hook on one end and straight wire on the other. With pliers, close this hook and form a similar hook on the opposite side. Welded selvage and heavy duty connector rods are supplied with a button head weld on one end, and a thread nut on the other end. Tighten the nut and cut off any excess rod. Rod end threads should be distorted to secure the nut.

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