Conclusion

As our country is a developing country we everyday need better roads for transportation, for comfort while traveling and other purposes. The grade or quality of road depends on the percentage of asphalt, stone size and on skill of labour. Here main importance should be given to mixing and crushing of stone for the construction of flexible pavement. Here we observe how mechanical processes improve the quality of the civil engineering works such as road construction, building construction, bridges etc.

The hot mix plant also includes stone crushing plant from where we get stone aggregate for other constructional activities.

Bad management of stone aggregate and dust entering the mixing drum affects the binding property of bitumen with stone and also the other properties such as durability, load carrying capacity etc.

For removal of dust from stones two processes are done:

a) water spraying method

b) by blowing air current

Hot mixing plants are one of the main sources of environmental pollution mainly air and noise pollution. So their location is always preferred out of the city.

Due to emission of dust and large noise and machine vibration it badly affects the health of the workers.

The recovery of heat from flue gases is not done which reduces the efficiency of insulated bitumen tank.

Climatic condition such as rainy season reduces the output of plant and also affects other components of plant

SPRAY BAR

BITUMEN PUMP 2" X 2" Size positive displacment gear pump with output 350 Litres/min. Max.	AIR COMPRESSOR 2 Cylinder, 3 H.P. Working pressure 9 Kg/Cm2 Capacity 360 L. P. M., 550 R. P. M
DRIVING UNIT Kirloskar, Make HA-294, 25 H.P. 2000 R.P.M. Air cooled diesel engine	BITUMEN SPRAYING PRESSURE 0 to 6 Kg/ Cm2
OPERATOR PLATFORM Technometer : Slow speed 0.5 Meter/min.	TEMPRATURE GAUGE (1) 0-300oC at top of tank (2) Digital Remote-Box

SPRAY BAR

Width : 2.4 Mtr. Standard

Adjustment width : 2.4 Mtr. To 3.8/4.2 Mtr.

Nozzle distance : 225 mm Nozzle c/c.

Controlling of spray bar : Pneumatic operation of nozzle

Preheating spray bar : By full circulation of preheated bitumen.

Air Pressure gauge : 0-10 Kg./ cm²

Rate of application : 0.3 to 1 Kg/ m² calibration chart is provided inside

driver’s cabin

BITUMEN PRESSURE DISTRIBUTOR

Diesel Engine:

All the equipments such as pump and compressor require power to operate this power is given by engine whose shaft is coupled with pump and air compressor. It is a Kirlosker make HA-294, 25hp 2000 rpm air cooled diesel engine.

LDO Tank: It is a 20ltr tank which provides fuel for burning.

Spray bar:

Spray bar consists of 6 to 8 nozzles located at a distance of 225mm. This spray bar is used to spray bitumen at the pressure of 0 to 6 kg/cm². Rate of application is 0.3 to 1kg/cm². It requires air pressure of about 9kg/cm^2.

BITUMEN PRESSURE DISTRIBUTOR

TECHNICAL SPECIFICATION

BITUMEN TANK MODEL	ATM 3000	ATM 4000	ATM 6000	ATM 7000
Length	2100 mm.	2400 mm.	3100 mm.	3300 mm.
Width	1800 mm.	1800 mm.	1900 mm.	1900 mm.
Height	1500 mm.	1500 mm.	1550 mm.	1650 mm.
Capacity	3000 Ltrs.	4000 Ltrs.	6000 Ltrs.	7000 Ltrs.
Man Hole	600 mm.	600 mm.	600 mm. 2 Nos.	600 mm. 2 Nos.
Insulation	50 mm.	50 mm.	50 mm.	50 mm.
Burner Fuel Consumption	20 Ltrs/Hr.	20 Ltrs/Hr.	20 Ltrs/Hr.	20 Ltrs/Hr.
Burner	Compressed air type	Compressed air type	Compressed air type	Compressed air type
Burner Fuel Tank	50 Ltrs.	50 Ltrs.	50 Ltrs.	50 Ltrs.
­Engine Fuel Tank	20 Ltrs.	20 Ltrs.	20 Ltrs.	20 Ltrs.
Service Tank	20 Ltrs.	20 Ltrs.	20 Ltrs.	20 Ltrs.
Mounting	Ashok LL/Tata Or 148" Wheel Base	Ashok LL/Tata Or 148" Wheel Base	Ashok LL/Tata Or 148" Wheel Base	Ashok LL/Tata Or 148" Wheel Base
Bitumen Tank Shape	Rectangular, Oval Shape	Rectangular, Oval Shape	Rectangular, Oval Shape	Rectangular, Oval Shape

Burner lines and Positive displacement pump

These lines are made of copper and their diameter is about 230mm. These lines carry the hot compressed air inside the tanker. These lines help to exchange the heat of these gases with the bitumen inside the tanker. The bitumen takes heat from these copper lines and thus fails to stick over the surface and remains in liquid state, the hot bitumen reduces its density after heating and thus its space is taken by cooler bitumen, in this way cycle continues and the bitumen remains in hot condition.

Positive displacement pump is also called bitumen pump which is used to empty the tank and also provide bitumen under pressure(6kg/cm²) to the spray bar consisting nozzles for spaying bitumen on road. It is 2’’ X 2’’ gear pump with output of 350LPM.

Compressor: & Burner:

Compressor:

Compressor provides the necessary air pressure at the spay bar and also the air inside the burner necessary to burn the fuel inside burner. Specifications of compressor are:

2 cylinder, 3hp, working pressure 9kg/cm²

capacity 360 L.P.M at 550 rpm

Burner:

Burner consists of a gas lighter which ignites the mixture of LDO and compressed air. The burner is connected to burner pipe lines which move hot gas inside the tanker. The burner also contains regulating valve through which supply of fuel can be controlled.

Welding:

Once the sheets are bent they are welded together to form cylindrical shape for this purpose carbon arc welding is used. It is the process in which a pure graphite rod of 4 to 19mm diameter and 300 to 400mm length. Non-consumable electrode is used to create an arc between it and work piece by holding it in electrode holder with an electrode extension of 15 to 125mm welding can be done with or without the addition of filler material. The arc which is called carbon arc is a soft arc and is usually of 25 to 40mm length, the temperature of the weld pool can be easily controlled by varying the arc length.

First the curved sheets are welded together to form the base of tank than one sheet with small curvature is welded over the two sheets and are welded with flat sheets to form another cylindrical tank on the outer periphery of the tank. Small pieces of plates are longitudinally welded such that they are at right angles to the surface of cylinder. On open side of the plates another curved sheet is welded such that it creates a hollow space between the inner and outer surface, thickness of this hollow space is equal to length of metal plates provided to fill insulating material of low thermal conductivity such as glass wool.

The cylinder is then tested for leakage with the help of UV light. The space between the cylindrical tank is filled with insulating material, in case of powder it is important that material is only filled in such a way that air gap between the material is maintained otherwise thermal conductivity will change. The insulating material should not contain any moisture. After this tank is painted from outside and a non-sticky coating is provided inside. The tank is mounted on the wheelbase and connected with necessary pipings.

Manufacturing of tank by rolling and welding:

Manufacturing of tank by rolling and welding:

Three roll benders work by "pinching" the flat work piece between two rolls and bending it as it comes in contact with a forming roll. This bends the work piece into a cylindrical form, where it is welded together to produce a cylinder. The upper roll is in a fixed position; the lower roll has adjustable movement to perform the gripping function. These are the "pinch" rolls. The third roll (the forming roll) is also adjustable. With a manually or hydraulically moved drop hinge, the top shaft is raised to release the pressure on the rolled sheet and allow removal of the finished work piece, especially a completed cylinder shape that may have had it's seam welded while still on the machine. Note: Without a lot of skill, on 3 roll machines, it can be difficult to form metal into tubular shapes smaller than 3 times the upper roll diameter when forming near capacity thickness and 1.5 times the upper roll diameter is often the tightest diameter using thinner and narrower metal. Results vary depending on metal thickness, width, and tensile strength.

Single-pinch (initial-pinch) machines require inserting the work piece into the machine twice in order to prebend both ends of a cylinder and ensure closure of the seam. To prebend the first end, the operator inserts the plate into the machine, which clamps it and pinches it between the top and bottom rolls. A side roll, moving diagonally toward the top roll, sets bend radius. The operator then removes the plate from the bender, rotates the plate 180 degrees to insert the second end into the rolls, then rolls the cylinder to completion. Recommended maximum thickness (or width instead) for prebending is usually 2/3 to 3/4 of the capacity of the machine.

Double pinch pyramid machines, also called three-roll double-pinch machines, can also prebend both ends of a plate with a single insertion into the bending machine, for reduction in material- handling time and cost. These machines can act as single-pinch machines or as pyramid machines, allowing the fabricator to select the best procedure for a particular job. The wide opening between the rolls allows short, heavy plate to be rolled. Double pinch-pyramid machines drive all three rolls, the top roll is fixed and the two lower rolls move in a straight path or an arc toward the top roll. This type of machine reduces the need for feeding the sheet through more than once.

On some machines, a cone shape can be formed by pre-cutting a flat metal blank with the correct inner and outer radius to form the cone (funnel) shape wanted. Usually the blank is fed on one side so that the inner radius rubs against a cone forming attachment. The bending roll position can sometimes be independently adjusted lower on one side to help.

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

Conclusion:

• The cams are most widely used elements in IC engines, machine tools, printing control mechanism, dye casting, milling and punch presses. The complicated motions that are difficult to achieve can be easily achieved with the help of a cam. Radial and tangent cams are most widely used in high and moderate speed engines. Their use is not only limited in engines or machines but we can often find their use in computer also. The cams can be designed and fabricated according to our need also. Radial and tangent cams are easy to manufacture and a large amount of these cams can be manufactured within a shorter period of time.

• The whole mechanism is composed of follower arm and guide; the motion of follower can be oscillatory or reciprocating. Guide plays an important role that it guides the motion of follower in a straight line. In absence of guide the motion of the follower can be disturbed and if proper lubrication between the guide and follower is not maintained then it may also jam the cam. An arm is brought into use when the follower cannot be directly connected to operate valves.

Formulae used:

Formulae

• S = stroke of the follower

• qo = angle of outstroke
• qr = angle of returnstroke
• Vo = velocity during outstroke

• Vr = velocity during returnstroke

• Ao = acceleration during outstroke
• Ar = acceleration during returnstroke
• w = angular velocity of cam
• Rc = radius of base circle of cam
• Rr = radius of roller follower
• N = speed of cam in rpm.
• q = Instantaneous cam rotation angle

Working of cam and follower:

Cam is mounted or fixed on a camshaft, which gets its motion from the rotation of flywheel by coupling it with a toothed wheel mounted on crankshaft. As flywheel rotates at high speed therefore a smaller wheel is coupled with a big wheel so that its motion can be reduced.

• The base circle of a cam can be divided into four parts that is angle of ascent, angle of dwell, angle of descent and angle of dwell again. During the first sector. i.e. angle of ascent , cam lifts the follower which with the help of arm and guide opens the valve then period of dwell comes into picture in which there is negligible displacement of follower takes place and the valve remains open for some time. During third sector. i.e. angle of descent , cam descents down and also the follower which closes the valve and then again dwell period comes into picture as a result valve remains closed for some time .These events occur in a cycle and in this way cam functions.

Technical Terms used in CAM II

• Motions of follower
• Simple harmonic motion
• Constant acceleration and deceleration
• Constant velocity
• Cycloidal Motion

• Simple harmonic motion: In this type of motion there is an abrupt change of acceleration from zero to maximum at the beginning of the follower motion and also from maximum negative to zero at the end of follower motion when the follower rises. Similar abruption would also be there at the start and end of the return motion. As these abrupt changes result in infinite jerk, vibration and noise etc. The programme should be adopted only for low or moderate cam speeds.
• Constant Acceleration and Deceleration: In such a follower programme, there is acceleration in the first half of the follower motion whereas it decelerates during the later half. The magnitude of the acceleration and deceleration is the same and constant in two halves.
• Constant velocity: Constant velocity of the follower implies that the displacement of the follower is proportional to the cam displacement and the slope of displacement curve is constant.

Cycloidal motion: A cycloid is the locus of a point on a circle rolling without slipping on a straight line. In this there are no abrupt changes in the velocity and the acceleration at any stage of the motion, thus it is the most ideal programme for high-speed follower motion.

Cams with specified contours:

• Tangent cam
• Circular arc cam

Tangent cam: When the flanks of the cam are tangential to base circle and nose circle then the cam is known as tangent cam. These cams are usually symmetrical about the central line of camshaft. These types of cams are used to operate inlet and exhaust valves of internal combustion engine.

circular arc cam: When the flanks of the cam connecting the base circle and nose are of convex circular arcs , then the cam is known as circular arc cam.

Technical Terms used in CAM (Diagram)

Technical Terms used in CAM

• Base circle: It is the smallest circle tangent to the cam profile (contour) drawn from the center of rotation of a radial cam.
• Trace point: It is the reference point on the follower to trace the cam profile such as the knife-edge follower and the center of the roller of a roller follower.
  Pitch curve: It is the curve drawn by the trace point assuming that the cam is fixed, and the trace point of the follower rotates around the cam.
• Pressure angle: It represents the steepness of the cam profile, it is the angle between the normal to the pitch curve at a point and the direction of follower motion. It varies in magnitude at all instants of follower motion.
• Pitch point: It is the point on the pitch curve at which pressure angle is maximum.
• Pitch circle: It is the circle passing through the pitch point and concentric with the base circle.
• Prime circle: The smallest circle drawn tangent to pitch curve is known as the prime circle.
• Angle of Ascent (outstroke): It is the angle turned by cam during the time of rise of follower.
• Angle of Dwell: It is the angle turned by cam while the follower remains stationary at the highest or lowest position.
• Angle of descent (Returnstroke): It is the angle turned by cam when follower returns to its initial position.
• Angle of action: It is the angle turned by cam during beginning of rise and the end of return of the follower.

According to shape

1. Knife-edge follower: - It is simple in construction it is pointed at one end; it produces a great wear at the surface of point of contact.

2. Roller follower: - It is widely used follower and has a cylindrical roller free to rotate about a pin joint, it has pure rolling action, but at high speeds sliding also occurs.

3. Mushroom follower: - This type of follower does not cause the problem of jamming the cam, it has high surface stresses and wear so instead flat-faced follower is used.

According to movement: -

1. Reciprocating follower: - In this type the cam oscillates and the follower reciprocates or oscillates.

2. Oscillating follower: - In this the follower is pivoted at one point and frame oscillates as the cam makes a rotary motion.

According to location of line of movement: -

1. Radial follower: - In this the line of movement of follower passes through center of rotation of cam.

2. Offset follower: - In this the line of movement of roller follower is offset from center of rotation of cam.

Applications and advantages of different cams:-

Radial or disc cam- used in smaller engines due to simplicity and compactness.

Spiral cam-used where we need to reverse the direction or reset the position of follower, mostly used in computers.

Cylindrical cam-used where more prompt and accurate service is required.

Conjugate cam-used where low wear, low noise, better control over follower at high speeds and high dynamic load is needed.

Globoidal cam- used in moderate speed engine where angle of oscillation of follower is large.

Spherical cam-used where exact transmission of motion is needed to follower.

Cams are widely used in automatic machines, IC engines, machine tools, printing control mechanism, dye casting, milling and punch presses.

Disadvantage: -

Due to irregular and varying speed, varying load and jerks to the engine cam fails to work ideally or according to our need which disturbs the efficiency of engine.

Classification of follower

1. According to shape

2. According to movement

3. According to location of line of movement

According to manner of constraint of follower: -

To reproduce exactly the motion transmitted by cam to follower, it is necessary that two remain in touch at all speeds at all times.

This type of cam is of three types: -

1. Pre-loaded spring cam: - In this a pre loaded compression spring is used to maintain the contact between cam and the follower. Example: -wedge and flat cam

2. Positive drive cam:- In this type constant touch between cam and follower is maintained by a roller follower operating in the groove of a cam. Example: - spiral and spherical cam.

3. Gravity cam: - In this the rise of the cam is achieved by the rising surface of the cam and the return by the force of gravity or due to weight of cam. Example: -Flat cam

According to follower movement

The motions of the follower are distinguished from each other by dwells they have. A dwell is the zero displacement or the absence of motion of the follower during the motion of cam.

This type of cam is of three types: -

1. Rise-Return-Rise: - In this, there is alternate rise and return of the follower with no period for dwells. Its use is very limited in industries. It has linear angular displacement.

2. Dwell-Rise-Return-Dwell: - In such type of cam there is rise and return of the follower after a dwell. It is more efficient and more used than R-R-R cam.

3. Dwell-Rise-Dwell-Return-Dwell: - It is the most widely used type of cam. The dwelling of the cam is followed by rise and dwell and subsequently by return and dwell.

Classification of cams

Classification of cams- They are classified according to:

1. Shape

2. Follower movement

3. Manner of constraint of follower.

According to shape: -

1. Wedge and flat cams: - A wedge cam has a wedge in general which has translational motion .The follower can either translate or oscillate. A spring is used to maintain contact between the cam and follower. Instead of wedge a flat plate with a groove is also used.

2. Radial or Disc cam: - A cam in which the follower moves radially from the center of rotation of the cam is known as radial or disc cam. It is used due to simplicity and compactness.

3. Spiral cam: - A spiral cam is a face cam in which a groove is cut in form of spiral. The spiral grooves consist of teeth, which mesh with a pin gear follower. The velocity of the follower is proportional to the radial distance of groove from axis of cam.

4. Cylindrical cam: - In this cam a cylinder, which has a circumferential contour, cut in the surface rotate about it’s axis. These cams are also known as barrel or drum cams.

5. Conjugate cam: - A conjugate cam is a double disc cam, two discs being keyed together and are in constant touch with two rollers of the follower.

6. Globoidal cam: - A Globoidal cam can have two types of surfaces, convex or concave. A circumferential contour is cut on the surface of the rotation of cam to impart motion to the follower that has an oscillatory motion.

7. Spherical cam:- In this the follower oscillates about an axis perpendicular to the axis of rotation of the cam.

Cam and Follower Mechanism

Introduction:

A cam is a reciprocating, oscillating or rotating body that imparts reciprocating or oscillating motion to the follower, with which it is in contact. The shape of cam depends upon its motion and time of dwell, it also depends on the nature of surface in contact with the follower. There are different classification and types of cam, which are described further. It has seen that the follower usually has a line contact with the cam, so that the follower and cam constitute a higher pair. With few exceptions of the motion of the follower is only determined positively by cam during a part of each stroke, while during rest of stroke contact between cam and follower has to be maintained by an external force. This external force has to be provided by a compression spring although sometimes weight of the follower is sufficient.

Complicated motions, which are difficult to achieve, are easily achieved with the help of cam. Cams are widely used in automatic machines, IC engines, machine tools, printing control mechanism, dye casting, milling and punch presses. Cam is the main cause behind the opening and closing of inlet and exhaust valve timely.

A driver member is known as Cam.

A driven member is known as Follower.

A Frame is that which supports the cam and guides the follower.