Tank,Size,Capacity & Distance between supply centers

Tank: To design the tank following points are to be considered.

Size: It is very difficult to have all advantages in one size. If the size is large tank will become bulky when loaded and if the size is small capacity of tank reduces. So we have to find optimum size of the tank, while selecting size following points should be considered.

• · Capacity or power of truck
• · Required material in one trip
• · Cost of transport

Capacity: Capacity of tank depends on type of work or rate of supply, in most of the situations the rate of supply changes with conditions. We take average rate of supply for deciding capacity.

Distance between supply centers: This is considered for the amount of insulation and amount of insulation needed and amount of fuel (Low Density Oil) used per km, by calculating L.D.O/km we can decide the capacity of L.D.O tank.

Bitumen Pressure Distributor tanks:

Bitumen Pressure Distributor tanks:

To run Hot-mix plants we need to transport asphalt to the plant site. For this purpose distributor tanks are needed, these tanks are insulated and are similar to the bitumen tanks installed on the site, but the only difference between the two is that these distributor tanks are portable and are mounted on truck wheelbase. These tanks also include spray bars which help to spray bitumen in road construction. Bitumen pressure distributor tanks include following parts:

1. Insulated tank
2. Compressor
3. Burner
4. Burner lines
5. Positive displacement pump
6. Diesel Engine
7. Light Diesel oil tank
8. Spray bar with multiple nozzles

Aggregate storage and feed:

Aggregate storage and feed:

Aggregate gradation and uniformity are entirely dependent on the cold-feed system. Proper care must be exercised not only in producing the aggregate but also in storage. Aggregates used for drum-mix plants must be received, handled, and stored to ensure that there is no danger of contamination or intermingling. Stockpiles must be properly graded and split into different sized fractions to control the gradation of the mix properly. Uncorrected segregated stockpiles will result in mix gradation difficulties. The plant supervisor should establish and maintain stockpiles in the most economical manner and correct any deficiencies in uniformity before the aggregate is fed into the mixing plant. Since the typical drum-mix plantdoes not have a gradation unit, the aggregate must be proportioned before entering the mixing drum. This is accomplished with a multiple-bin cold-feed system equipped with precision beltfeeders for control of each aggregate.

Conveyor belts:,Bitumen tank:,Mixer drum:

• Conveyor belts:

Conveyor belts are used to transport the aggregate within the plant. The conveyor belts are made up of vulcanized rubber with reinforced nylon wires. The width of belts range from 32 to 46 inches driven with the help of motors and double conical rollers. The power of motors range from 3 to 5 hp. Strength of belt ranges from 32.8 to 35 Mpa. Predicted life of belt is 2 to 3 yrs.

• Bitumen tank:

It is a cylindrical tank provided with insulation of glass wool about 50 to 80mm thick. The diameter of the tank varies according to production; it ranges from 6 to 12ft. Its length varies from 12 to 28ft. This tank is facilitated with a pump and burner and a blower. The inner surface is heated with the help of burner lines provided inside the tank. The fuel that is burnt inside these lines is Low Density oil. Due to heating of this inner surface the bitumen fails to adhere to the inner surface and remains in liquid state. Blower provides necessary air needed for combustion inside the burner. A pump is also provided with a valve to provide the bitumen inside the mixer drum from the tank.

• Mixer drum:

A mixer drum is a rotating cylinder with longitudinal angles provided inside its inner periphery. Its diameter ranges from 6 to 8ft and 12 to 18ft in length. The drum is rotated with the chain drive with 15hp motor.

Vibrating screen:

Vibrating screens are also called as scalping screens or gizzlers. Vibrating screen delivers optimum separation of fine materials due to a steeper screen inclination (typically 25 to 30 degrees), effective material bed management and higher Gravitational-force operation and increased inclination boosts the particle travel rate, reducing the bed depth, while a higher-than-conventional speed and stroke create maximum Gravitational-forces that quickly stratify material for effective screening. Vibrating screens are available in a wide range of sizes from 4' x 12' up to 6’ x 18' . The mechanism of driving screen is similar to movement of crank and piston rod. The driving units of vibrating screen are vibromotors which range from 15 to 50hp. Vibrating screens are totally enclosed in a housing. Screen houses are rigid and reasonably dust tight with self closing doors or close fitted entrances and exits for access. The dust exhaust at outlet should not exceed more than 0.50mg/m³ .

In Hot-mix plant vibrating screens are mainly used to separate stones into different sizes ranging from 6 to 20mm.

Note: As stone is irregular in shape therefore the longest dimension of stone determines its size.

Introduction to Hot-mix plant:

Hot mix plants are also called as asphalt mixing plants or drum mix plants. In a drum mix plant the aggregate is not only dried and heated within a drum, but is also mixed with the asphalt. The basic plant consists of a rotating drum dryer, an asphalt proportioning and asphalt dispensing system. The ease of setup and operation of the drum mix plant makes it ideal machine for operation. A complete set up of hot mix plant includes broadly three operations:

• Crushing and separating of stones
• Aggregate storage and feed
• Drum mix

CONTENTS

	Introduction to Hot-mix Plant
	Crushing and separating of stones
	Components of Hot-mix plant
	Stone crushers or Jaw crushers
	Vibrating screen
	Conveyor belts
	Bitumen tanks
	Mixer Drum
	Aggregate Storage and Feed
	Bitumen Pressure Distributor Tanks
	Technical Specification