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Selection of proper HI-GRIP BELTS
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To
select the proper belt for any given drive involves a simple calculation using the
formula: |
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Belt
Width = Total H.P. Required * Service Factor *25.4 |
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(mm)
H.P./25mm roling*Arc of Contant Factor |
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STEP
1. |
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Determine
Service factor |
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(a)
Select Factor form, table1, Insert this value in belt width Formula. |
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STEP
2. |
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Determine
H.P./ 25mm rating |
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(a)
First calculate belt speed in meters per sec.(mtrs/sec) using the formula. Drive pulley
dia(mm)* R.P.M.*3.14 1000*60 |
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(b)
Using calculated speed in mtrs/sec. refer to table 11. Move across the table to the
minimum pulley size( Figures shown in red) The number shown in black is the H.P./25mm
rating value. Insert in formula. The belt type is designated at the top of the selected
column. 'KHCA' types are used where one surface of the belt comes in contact with pulley
and or pulley and jockey pulleys. |
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STEP
3. |
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Determine
Arc or Contact correction factor. |
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(a)
If both drive and driven pulley have identical diameters no correction factor is required. |
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(b)
If pulleys have different diameters, determine a difference (in mm) and refer to table
no.111. Move across table to apropriate center distance column to find Arc of contact
Correction Factor. Insert this value in formula. |
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STEP
4. |
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Complete
belt width formula calculations. |
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STEP
5. |
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Calculation
of length : Calculate length of all the belt from following formulae : |
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(a)
Open Drive ( Good Approximation) |
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L=2C
+ 1.57 (D+d) +(D-d) 2/4C |
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(b)
Cross Drive ( Good Approximation) |
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L=
2C + 1.57 (D+d) + (D+d) 2/4C |
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STEP
6 : |
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Tension
: See tensioning and mounting |
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EXAMPLE |
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60
H.P. 1440 R.P.M. electric motor driving Balt Mill, heavy load under normal conditons.
Drive pulley 300mm diameter, 150mm face. Driven pulley 750mm diameter, 150mm face. Pulley
centre distance 1850. |
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OPEN
DRIVE |
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STEP
1. |
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From
table 1, Service factor for Balt Mill is 1.3. |
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STEP 2. |
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Surface
Speed =(300*1440*3.14)/1000*60 = 22.6 mtrs/secs. |
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Using
22.6 mtrs/secs table 11 give H.P./25mm rating of 21.28. HI-GRIP BELT type KHC2A 10. For
simple open drive select KHC2A 10 |
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STEP
3. |
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Table
111 gives Arc of contect factor of 0.94. |
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STEP
5. |
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Length
of the belt L=2C + 1.57 (D+d) + {(D-d)(D-d)}/4C |
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=2*1850+1.57*1050+{(202500/(4*1850))}=5375.86mm
or 537mm |
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STEP
6. |
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Tension
hte belt to 3%. Thus Belt selected is KHC2A 10 width 100mm .Length 5376mm and tension 3%. |
Table
1 Load correction factor |
DRIVE |
TYPE
OF MACHINE |
CORRECTION
FACTOR |
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Light
starting load, uniform speed |
Centrifugal pumps,
electric generators, blowers, fans, light textile machines, automated lathes, light duty
evenly loaded conveyors. |
1.0 |
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Medium
load, unevn speed |
metal and
wood woking machines, milking machines, smaal lathes, rotary compressors, group
drives,belt conveyors with intermittent loads. |
1.1 |
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Medium
starting load, iregular speed, fluctuating load. |
Centrifuges,
large fans, piston pumps, pulpers, dough mixers, ball mills, tube mills, grinding
machines, carding engines,spinning frames, gang saws, piston pumps with speed fluctuation
at 1:80. |
1.3 |
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heavy
starting, pulsating and intermittent loads. |
calenders,
paper mill rolls, brick machines, forgingpresses, power punches and shears, vibrators,
dredgers, rolling mills for non ferrous metals, piston pumps and compressors with a speed
fluctuating of 1:80, pan grinders, planners. |
1.5 |
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Very heavy
starting, very uneven speeds, usually severe. |
Beater
mills, crushers, extrusion presses, cold rolling mills, heavy toeque drives oily, dusty
conditions. |
1.7 |
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