Capital Equipment Suppliers  Most experienced plant operators know these formula and will find this boring. However, this issue of “Cliff’s Notes” is directed to the less experienced operators, the new guys. They will find these things both interesting & informative.

To convert horsepower To KW:

Multiply horsepower (h) by .7457
Assume the following: h= 350hp
EXAMPLE: 350x .7457= 261 KW

To calculate the length of a slat conveyor at a 45-degree angle:

Measure height (h), multiply by 1.41416
Assume the following: h= 65'
EXAMPLE: 65x 1.41416= 91.9204 feet long slat at 45 degrees

To calculate the speed in FPM of a slat conveyor, the following information is needed:

Motor RPM- (rpm)
Motor sheave size- (ms)
Driven sheave size- (ds)
Gear box ratio- (gbr)
Head sprocket size- (hs)
Assume the following: Rpm= 1755, ms= 8", ds= 14", gbr= 25.13 to 1 and hs= 9"
Calculate the sheave ratio, i.e.: 8" drive, 14" driven
Multiply motor speed by the answer = input RPM
Input RPM divided by gear box ratio x diameter of head pulley x .2618= slat speed in Feet Per Minute
EXAMPLE: 8 divided by 14 = .571 x 1755 = 1002.86 input rpm div. 25.13 gbr = 39.91 head shaft rpm 39.91 x 9 = 359.19 x .2618 = 94.04 FPM

Asphalt Oil

To find asphalt % by total mix:

Add oil to aggregate then divide oil by total of the two
Assume the following: 250 tons aggregate used, 15 tons oil used
Example: 250agg + 15oil = 265 15 div 265 = .0566% oil by total

To calculate where you should be running with a known aggregate TPH:

TPH of dry aggregate x % of oil, div. 100-% of oil = oil tph
Assume the following: 70tph aggregate (dry), 5.4% oil
Example: 100% - 5.4% = 94.6 70 tph x 5.4% = 378 div 94.6 = 3.99 tph of oil

To find the number of gallons delivered on a particular bill of lading:

Net weight in pounds (x), divide 8.328 (pounds per gallon of water, which has a specific gravity of 1.0) = y
Divide y by the specific gravity (z) listed on the delivery ticket for the oil you are using
Assume the following: x= 66,920, z= 1.0273
Example: 66,920 divide 8.328= 8,035.54 (y)
8,035.54 divide 1.0273 (z)= 7,822 gallons at 60 degrees Fahrenheit

To find asphalt gallons per ton:

Look up AC pounds per gallon at the oil's temperature (x)
Divide that number into 2000
Assume the following: x = 7.81
Example: 2000 div. 7.81 = 256.08 gallons AC per ton at the chosen temperature

To convert gallons of oil to tons:

Look up AC pounds per gallon at the oil's temperature (x)
Multiply that number by number of gallons
Divide that number by 2000
Assume the following: x = 7.81
Example: 7.81 ppg x 25,000 gals = 195,250# div
2000 = 97.625 tons of oil at (x) temperature

To find out how many tons of oil are in an AC tank:

Check oil temperature (t)
Measure liquid, convert inches to gallons (g)
Find temperature on compensation chart and get conversation factor (f)
Read oil pounds-per-gallon* at 60 degrees (p)
Assume: t= 325 degrees
g= 12,834 gallons, f= .9105, p= 8.456
Example: 8.456 x .9105= 7.699ppg at 325 degrees
7.699ppg x 12,834gals = 98,811.37 pounds
98,811.37 # divide 2,000 = 49.41tons of oil

To figure how much mix you can make with a given quantity of oil:

Tons oil divided by percent of oil in mix = yield
Example: 28 tons div. .055%= 509.09 tons of hot mix produced

To find pounds-per-gallon of any oil:

Find specific gravity listed on 'bill-of-lading' (g)
Multiply pounds-per-gallon of water (8.33)* by the specific gravity (g) of the oil
Assume: g= 1.0273 {actual reading for Oregon PBA-2} w= 8.33
Example: 8.33 x 1.0273= 8.56pounds-per-gallon for the oil at 60 degrees

*Actual PPG of Water

To find U.S. gallons capacity of a cylindrical tank:

Measure the diameter (d) and the length (l)
Square the diameter, multiply by length, then multiply by .0034
Assume: d= 95", l= 337"
Example: 95x 95x 337x .0034= 10,341 gallons

Baghouse

It requires approximately 165 CFM of air to produce 1 ton of hot mix.

To find the correct baghouse size for a particular drum:

Radius x radius x 3.142 (pi) x *1000= CFM required
Example: Assume a 9 foot drum. 4.5 x 4.5 = 20.25 x 3.142 = 63.6255 x 1000 = 63,625.5 CFM
This drum would require a 65,000 CFM baghouse

* 1,000 feet per minute equals the air velocity through the dryer/mixer. This figure is usually down around 750 to 850 fpm, but using 1,000 fpm gives us a little bit of over sizing which is a good thing since we don’t want the air-flow through the baghouse to limit production rates.

To find the square feet of cloth in a particular baghouse, you need to know the diameter of bag (D), lengths of bags (L) and number of bags (N):

The formula is: D x 3.142 = A
A div 12 = B
B x L = SF (sq. ft. per bag)
SF x N = total sq. ft. of cloth in baghouse

To find air-to-cloth ratio (should be under 5.- to-1 in batch, and 5.5-to-1 in drum plants):

Determine square footage of an individual bag (X)
Multiply that by the number of bags (Y)
Divide that answer by baghouse CFM (Z). X times Y = total square feet of cloth (sq/ft). Z divide sq/ft = air to cloth ratio

Most manufacturers figure drum air velocity at between 900 and 1,000 FPM.

Conveyors

To find the speed of the conveyor:

Calculate the sheave ratio, i.e.: 10" drive, 18" driven
10 divided by 18 = .555 Multiply motor speed by the answer = input RPM
Input RPM divided by gear box ratio x diameter of head pulley x .2618= belt speed in FPM
Example: Assume an 1800 RPM motor, a 25-1 gear box and an 28" head pulley: 1800 x .555= 999 divide 25 = 39.96 x 28= 1118.88 x .2618= 292.92 FPM

Viking pump sizing

HL225 .01898 gallons per revolution
K225 .1055 gallons per revolution
L225 .23 gallons per revolution
2"Q34 .23 gallons per revolution
3"Q34 .61 gallons per revolution

Used in conjunction with an accurate tachometer, these pump specifications can be helpful to calculate pump outputs when considering erratic mix sample results relating to asphalt content.

General Facts

A plant loses about 3% of its production rate per 1,000 feet of elevation due to the thinning of the air.

Plants are designed to remove 5% moisture. Obviously, the higher the moisture, the lower the production rate. NAPA publishes a series of charts to figure losses for elevation and moisture. Visit asphaltpavement.org for more information.

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