V-Belt Installation and Tensioning 1.08 by hedongchenchen

VIEWS: 16 PAGES: 43

									V-Belt Installation & Tensioning
V-Belt Installation Check List
 1) Disconnect and lock out power source. Observe all safety procedures.
 2) Remove belt guard
 3) Loosen motor mounts
 4) Shorten center distance
 5) Remove old belts
 6) Inspect belt wear patterns for possible troubleshooting
 7) Inspect and clean drive elements-bearings, shafts, etc.
 8) Inspect sheave grooves for wear - replace if necessary
 9) Preliminary sheave alignment
 10) Identify proper replacement belts
 11) Install new belts
 12) Tension belts
 13) Final sheave alignment
 14) Replace guard
 15) Start drive (look & listen)
 16) Re-tension after 24 hours
Safety First


      • Be sure to review and
        comply with all building
        and safety codes
      • Disconnect and lockout
        the power supply
Inspect Drive Elements


           • Inspect and replace faulty
            or damaged machine
            elements such as worn
            bearings or bent shafts
Relieve Belt Tension

          • Loosen the drive take-up
           and move the sheaves
           closer together to facilitate
           the removal of the old
           belts and to insure
           installation of the new
           belts without damage
Inspect Drive Elements

           • Sheaves should be
            cleaned of rust and
            foreign material
Inspect Sheaves
      • Sheave condition and
        alignment are vital to
        V-Belt life & performance
      • Never install new belts
        without a thorough
        inspection of the sheaves
      • Look for worn groove
        sidewalls, shiny sheave
        groove bottom, wobbling
        sheaves and damaged
        sheaves
Select Replacement Belts

        • Never mix new and used belts
         on a drive
        • Never mix belts from more
         than one manufacturer
        • Always replace with the right
         type of belt
        • Always observe belt matching
         limits
Installing New Belts

         • Place the new belts on the
           sheaves and be sure that the
           slack of each belt is on the
           same side
         • Do not force the belts on the
           sheaves by using a pry bar or
           by rolling the sheaves
Check Sheave Alignment

         • Sheave should be mounted
           as close to bearing as
           possible to reduce overhung
           load on bearing
         • The straight-edge should
           make contact at two distinct
           points along the outside
           perimeter of both sheaves
         • V-Belt sheave alignment
           should be within a tolerance
           of 1/16” per 12” of drive
           center distance
                Sheave Alignment
   The straight-edge should make contact at four distinct
   points along the outside perimeter of both sheaves.

                    1

                    2

There should
be no gaps
between the
sprocket and
straightedge        3
at 1-2-3-4
                    4

               Proper   Parallel    Horizontal      Vertical
                        (Off-Set)    Angular        Angular
                                    (Pigeon-Toed)
V-Belt Tensioning

         • Proper tensioning is the
           single most important
           factor necessary for long,
           satisfactory operation
         • Too little tension will result
           in slippage, causing rapid
           belt and sheave wear and
           loss of productivity
         • Too much tension can
           result in excessive stress
           on the belts, bearings and
           shafts
V-Belt Tensioning

        Tension-Finder
        • A simple method to assure
          proper tensioning
        • Easy and Accurate
        • For use on individual belts
          or V-Bands
        • Should not be used with
          aramid or glass cord belts
  V-Belt Tensioning
Using the Tension-Finder

            • Step 1: Install belts
              loosely on the drive
            • Step 2: Apply enough
              tension to take the slack
              out of the belts
  V-Belt Tensioning
Using the Tension-Finder

            • Step 3: Scribe a line on
              the belt using the Tension-
              Finder as a square
  V-Belt Tensioning
Using the Tension-Finder


            • Step 4: Place the Start
              Slot over the line
  V-Belt Tensioning
Using the Tension-Finder


            • Step 5: With the line in
              the Start Slot, attach the
              spring to the belt
            • For cog belts, the best
              place for the spring may
              be in the cog
  V-Belt Tensioning
Using the Tension-Finder

            • Step 6: Scribe a line at the
              spring end of the Tension-
              Finder. Use this line as a
              reference point in case the
              spring slips off the belt
  V-Belt Tensioning
Using the Tension-Finder

            • Step 7: Determine the
              required slot for your drive
              from the table. Then
              keeping the Tension-
              Finder snug against the
              clip, tighten the belt until
              the line has moved to the
              designated slot.
  V-Belt Tensioning
Using the Tension-Finder

            • Step 8: Remove Tension-
              Finder hardware from the
              belt, tighten mounting
              bolts and replace belt
              guards. You’re ready to
              start the drive!
            • Warning!! Remove all
              Tension-Finder hardware
              from the belt before
              starting the drive.
     V-Belt Tensioning
Special instructions for Cog Belts


                 • Place the spring in a
                   cog groove
     V-Belt Tensioning
Special instructions for Cog Belts


                 • Put a dot in the start
                   slot. Be careful not to
                   catch the pen in the
                   slot so you don’t pull
                   the tip out of the pen.
     V-Belt Tensioning
Special instructions for Cog Belts


                 • Scribe a line through
                   the dot. The line should
                   extend across the width
                   of the Tension-Finder.
               V-Belt Tensioning
Recommended tensioning slots for Tension-Finder




  The recommended slot numbers will provide an
  adequate level of belt tension on average drives.
  If more tension is required go to a higher slot number.
  For less tension go to a lower slot number.
        V-Belt Tensioning
Using the Spring Loaded Tensiometer


                1. Measure the span length of
                the drive. Set the large “O” ring
                at 1/64” for each inch of belt
                span. For example, set the
                large “O” ring 1/4” for a span
                length of 16”, at 1/2” for a span
                length of 32”, at 1” for a span
                length of 64” etc.
        V-Belt Tensioning
Using the Spring Loaded Tensiometer


              2. Set the small “O” ring at zero and
              press down the Tensiometer at the
              center of the belt span.
              A. On a single belt drive, depress the
              Tensiometer until the large “O” ring is
              even with the bottom of a straight
              edge placed on the outside rims of the
              two sheaves.
              B. On a multiple belt drive, depress
              the Tensiometer until the large “O”
              ring is even with the top of the next
              belt. Measure each belt in the drive.
              and take the average reading of all
              belt tensions.
       V-Belt Tensioning
Using the Spring Loaded Tensiometer

                3. Remove the Tensiometer, and
                observe that the small “O” ring has
                moved from its original setting at
                zero to the number of pounds
                required to deflect the belt to the
                extent noted above.

                4. Check this reading against the
                value of Pmin and Pmax calculated
                in Step 4 of the “Formula Method”
                or from the Table.
                    V-Belt Tensioning
        Strand Deflection - Formula Method
This method is based on the fact that the force required to deflect a given
span length by a given amount is related to the tension in the belt.

                                   Step 1. Measure span length (t) in inches as
                                   shown or calculate as follows:




                                   Where:
                                   t =      span length, in inches
                                   C =      center distance, in inches
                                   D =      large sheave pitch diameter, in inches
                                   d =      small sheave pitch diameter, in inches
                    V-Belt Tensioning
      Strand Deflection - Formula Method
Step 2. Calculate the deflection distance by: t/64 = deflection. Note that the
  deflection distance is always 1/64” per inch of span length (for example, a 32”
  span length would require a deflection of 32/64 or 1/2 inch).

Step 3. Calculate the static strand tension (Ts) per belt by the following formula:

         Design HP x K                                          Note: The value of
  Ts =                   + Tc                                     Ts is for an
             QxS                                                  individual V-belt.

Where: K = value from the table depending on value of D - d
                                                            C
  Q = number of belts/ribs on drive
  S = belt speed, feet per minute / 1000
  Tc = add-on tension allowance for centrifugal force, from Table.
                     V-Belt Tensioning
        Strand Deflection - Formula Method
  Step 4.
Calculate the recommended minimum & maximum deflection forces (P), in pounds:


                  Ts + Y                    (1.5 x Ts) + Y
         Pmin =                    Pmax =
                    16                            16


Where:
 Ts = Static strand tension (from Step 3)
 Y = Constant from Table 30
                   V-Belt Tensioning
      Strand Deflection - Formula Method
For drives using only one belt, and at least one shaft is free to turn, use
the following for the deflection forces (P):


               Ts + tLr                 (1.5xTs) + tLY
      Pmin =                   Pmax =
                 16                           16

Where: t = span length, inches (from step 1)
       L = belt pitch length, inches
       Y = constant from Table
V-Belt Tensioning
       STEP 5 Using a Tensiometer apply force
       to ONE belt of the drive, perpendicular to
       the span at its mid-point. Measure the
       deflecting force being applied when the
       belt has been deflected the distance
       calculated in Step 2 (use an adjacent belt
       as reference point; on single belt drives,
       use straight edge or taut string across
       sheaves). The measured force should be
       between the values of Pmin and Pmax
       calculated in Step 4. If the measured force
       is outside these values, adjust center
       distance to increase or reduce tension, and
       repeat above procedure. On multiple belt
       drives an average of readings on each belt
       is recommended.
V-Belt Tensioning

        NOTE: If new belts are being
        installed for the first time, it is
        permissible to tension as much as
        1.33 x Pmax to allow for initial
        stretch and seating in the grooves.

         STEP 6
        During the first 24 hours of
        operation, it is advisable to repeat
        the procedure in Step 5 at least
        once.
                  V-Belt Tensioning

• Operate the drive for a few minutes to seat the belts in
 the sheave grooves. Observe the operation of the drive
 under the highest load condition (usually starting). A
 slight bowing of the slack side of the drive indicates
 adequate tension. If the slack side remains taut during
 the peak load, the drive is too tight.

• Check the tension on a new drive several times during
 the first 24 hours of operation, by observing the slack
 side span.
                  V-Belt Tensioning
• Keep the drive free of foreign material which might cause
 slippage or damage to the belt and sheave surfaces.

• If a V-Belt slips, it is too loose. Increase the tension by
 increasing the center distance.

• Never apply belt dressing as this will damage the belt and
 cause early failure.
V-Belt Tensioning

      • Excessive tension can be
        even more detrimental
        than too little tension not
        only on the belts but also
        the bearings and shafts.
      • Indicators of excessive
        tensioning may be
        repeated belt breakage,
        excessive vibration,
        overheated bearings,
        whipping or bent shafts
V-Belt Tensioning
Elongation Method

          • Because belt elongation is
           related to the tension causing
           it, tape-measured lengths,
           both slack and tight, can be
           used to obtain proper Vee-
           Band tension.

          • Note: The Tension-Finder
           is based on the elongation
           method.
               V-Belt Tensioning
                Elongation Method

STEP 1 Check sheaves to make sure they are properly
aligned and that the grooves are not excessively worn (they
should not be dished out more than 1/64”).

STEP 2 Decrease the center distance until the Vee-
Band(s) can be easily slipped into the sheave grooves.
Forcing the belts on can damage the load-carrying cords and
cause premature failure.

STEP 3 With the Vee-Band(s) still on the drive at no
tension, tape their outside circumference (slack O.C.).
               V-Belt Tensioning
                Elongation Method




NOTE: If you are tensioning a used belt, decrease the
center distance until there is no tension on it; then tape the
outside circumference.
                  V-Belt Tensioning
                   Elongation Method

 STEP 4 Find the required static tension (Ts) per individual strand
 (rib) using the formula:

                        Design HP x K
                 Ts =                   + Tc
                             QxS

Where: K = value from table depending on D-d
                                              C
Q = number of belts
S = belt speed, fpm/1000
Tc = add-on tension allowance for centrifugal force (See Table)
                 V-Belt Tensioning
                  Elongation Method

STEP 5 Find a range of recommended Static Strand Tensions:
  Lower value = Ts (from Step 4)
  Upper value = 1.5 x Ts

STEP 6 Calculate minimum and maximum elongation band
 lengths for use in tensioning drive:
 a. From table, find length multipliers corresponding to the
 lower and upper values of Ts in Step 5.
 b. Multiply the slack O.C. found in Step 3 by the multipliers to
 find the minimum and maximum elongated band lengths.
V-Belt Tensioning
Elongation Method
         STEP 7 Increase the drive
         center distance until a tape
         measurement of the bands O.C.
         is between the two values
         calculated for elongated band
         lengths in Step 6(b).
         STEP 8 Re-tension as required.
         A new Vee-Band may lose tension
         rapidly during the run-in period &
         will probably need re-tensioning.
         A Vee-Band that has been on a
         drive for some time may also
         require re-tensioning due to
         tension decay from normal use
         and wear.
www.CarlisleBelts.com

 from


www.c-rproducts.com
sales@c-rproducts.com
Tel: +44 1327 701030
Fax: +44 1327 701031

								
To top