Wednesday, January 9, 2008

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/cm2.

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.