Biogas-Plant/C3/Construction-of-the-Dome/English

Visual Cue	Narration
Slide 1f Welcome to this Spoken Tutorial on construction of the dome of the Digester tank.	Hello everyone. Welcome to this Spoken Tutorial on construction of the dome of the Digester tank.
The tutorials on- digging of the pit and laying the foundation are available on Spoken-tutorial.org website	The tutorials on- digging of the pit and laying the foundation are available on Spoken-tutorial.org website
Slide 2 We will learn: The step-by-step procedure for constructing a dome.	In this tutorial, we will learn- The step-by-step procedure for constructing a dome.
Slide 3 What is a dome?	So what is a dome?
Image of the animated Biogas dome	Dome is an arch like structure placed on the Digester tank where the Biogas is collected.
[[Image:]]	Construction of the dome is a very interesting and important procedure.
[[Image:]] [[Image:]]	Items used for construction are- Steel rods Chicken mesh and Steel wire Detailed specifications of these are mentioned in the tutorial on materials required.
	Let’s begin
[[Image:]]	First, make a circle of 7 feet 6 inches diameter with lime powder. Now put 12 marks on the circumference of the circle and number them from 1 to 12, as shown. These 12 marks should be separated by a distance of two feet from each other.
Animation [[Image:]] [[Image:]]	Next, hammer 12 10-inch steel rods all along the marked circumference. Hammer the 10-inch steel rods upto 2 inches in the ground. Remember that they have to be removed later.
Next, comes the use of 12-ft long steel rods.	Next comes the use of 12-ft long steel rods.
[[Image:]]	With the 12-ft long steel rods, we’ll make an outer circle around the hammered 10-inch steel rods.
[[Image:]]	I will now tell you how to make a circle using the hollow rod. Use an iron rod having hollow ends. With this iron rod, bend the 12-ft steel rods to form a circular shape.
[[Image:]]	Then place the circular steel rods around the smaller 10-inch steel rods, as shown. We will need 2, 12-ft rods to complete the circle.
[[Image:]]	Now tie the circular steel rods to the 10-inch steel rods using steel wires, as shown. Ensure that the knot is tied very tightly and the steel rod circle is very stable. This is the base of the dome. Hence it has to be very strong to bear the load of the plastered dome later.
[[Image:]]	Now hammer a 4-ft and 2 inches long bamboo stick in the center of the circle, as shown here. Hammer the bamboo stick up to 2 inches in the ground. Ensure that it can stand firmly by itself and can be easily removed later This bamboo stick should be able to temporarily support the frame of the dome.
Let’s start building the frame of the dome.	Now let’s start building the frame of the dome.
Animation	Again, use the hollow iron rod and bend a 12-ft long steel rod to form an arch like shape. This arch will give the semi-circular shape to the dome. Hence, ensure that the arch is symmetric on either side when bent. Similarly, bend 2 more 12-ft rods to form arches.
Diagrammatic representation [[Image:]]	Let me explain exactly how the arches have to be placed on the circumference using a diagram. Secure one end of the arch at rod number 1, and the other end of the arch at rod number 7. This will ensure perfect symmetry to the arch And it will rest on the bamboo stick in the centre.
[[Image:]]	Use steel wires- To tie the arch together with the hammered 10-inch steel rod And the circular ring
[[Image:]]	For tying, make a knot like structure with the steel wire, as shown here.
[[Image:]]	Do likewise at the opposite end of the arch, as well.
Next, we will tie two more arches.	Next, we will tie two more arches. Secure the second arch to rod number 3, and rod number 9. And secure the third arch to rod number 5 and rod number11.
The 12 feet steel rod arches should be- at an angular separation of 60 degree at the base	The 12 feet steel rod arches should be- at an angular separation of 60 degree at the base
[[Image:]]	Now, we have three arches for the frame of the dome. Next, carefully slide the steel rods at the top such that a small gap is left open in between. Tie the steel rods using the steel wires as shown. Intersection of the three arches will look like a triangle. The sides of the triangle should be approximately 2.5 inches. As shown in the image, the top view of the framework should look like this after tying.
[[Image:]]	What you see here is the mason showing- the exact position of the open triangular gap using the bamboo stick This gap is where the main gas pipe of 1 inch diameter will be fit.
[[Image:]]	Once the arches have been fixed, we have to make circular rings with the remaining 12-feet steel rods.
	First let us understand how to make these rings with the help of a diagram.
3D animation	This is the framework we constructed so far - circular base semi-circular arches Now we need to fix 8 circular rings such that they can be placed on the arches, as shown. The rings have to be uniformly separated by a distance of 8 inches between each of them.
[[Image:]]	To make circular rings, start from the top and gradually move downwards.
[[Image:]]	Two things to keep in mind while making circular rings are- The length of the steel rod would depend upon the position of the circular ring on the frame. Longer steel rods would be required as we gradually go from top to bottom.
Image	We will first have to cut the steel rods to the required length before we fix the rings.
3D animation- steel rod bending to form a ring with length and diameter	So, let’s do that. For the first ring, which is the smallest ring at the top. We will need approximately 4 ft and 7 inch steel rod (adding 2 feet extra for tying). Diameter of this circular ring will be 10 inches For the second ring, we will need approximately 7 ft 1 inch of steel rod. Diameter of this ring will be 1 foot and 7 inches For the third ring, 9 ft and 8 inches steel rod would be required Diameter would be 2 ft 5 inches Fourth ring will require 12 ft 3 inches long of steel rod. Diameter of this ring will be 3 ft and 3 inches Fifth ring will need 14 ft 10 inches long steel rod Diameter of this ring will be 4 feet 1 inch Sixth ring will require 17 feet 4 inches long rod. Diameter of this ring will be 4 feet and 10 inches Remember- as mentioned while explaining the first circular ring an extra 2 feet has been calculated for tying the rods together with steel wires for all the 8 rings. And the diameter for all the 8 rings is calculated excluding the 6 inches.
	Now comes the 7th and 8th ring. Both will be used for making the circular rings and also the entrance of the dome. Measurements for these two are- Seventh ring will require 20 ft and 10 inches long steel rod. And for eighth ring 23 ft and 5 inches long steel rod would be required. Keep in mind that this includes the measurement for the bent rods as well
[[Image:]]	As soon as three circular rings are placed, an important thing to be done is-
[[Image:]]	* Place 6 Bamboo sticks of length 4 ft in an inclined position inside the frame of the dome. Note that- Bamboo sticks have to be spread out uniformly from the centre of the base. And should be firmly rested against the circular rings or the arches. These sticks will further give support to the frame of the dome.
[[Image:]]	Please note, if you follow the measurements mentioned earlier- Then you will get a uniform distance of 8 inches between each circular ring. To confirm this, use a 1 foot steel scale having two hooves. The distance between these two hooves should be 8 inches. And it should fit in between two circular rings as shown here. However, you may ignore minor variations, if any.
	Just after placing the 6th circular ring an important thing to be done is - to fix vertical rods on the frame.
	I will explain how to do that:
[[Image:]] Saurabh: Show animation remove the image below as it already has mesh. [[Image:]]	Between two half-arches - Fix a steel rod of length 5 ft and 5 inches bisecting the two main arches. Tie this rod using steel wires from the base ring upto the first ring as shown in the image. Similarly, fix two more steel rods of 4 ft and 7 inches bisecting the half-arch and the 5 ft and 5 inches steel rod. Tie these two rods using steel wires from the base ring upto the second ring, as shown. Please note- between the 5th and 6th 10 inch hammered steel rod do the following: The 4ft 7 inches long steel rod has to be bent and tied to the 6th ring. This is done to make space for the entrance of the dome as shown in the image. Note that, in both cases- Extra 3 inches have been left at the top for the ease of tying the steel wire to the circular rings.
	Now we will fix the last two circular rings i.e. 7th and 8th ring. However it is to be noted that - between 6th and 8th ring will be the gap or the entrance to the dome.
[[Image:]]	This gap should be big enough for the mason to enter inside the dome. Size of this gap would be approximately- 2 ft of width and 2 ft of height
	Use 7th and 8th ring to make the gap of the mentioned size. Bend the 7th rod, to make the upper side of the entrance, as shown in the image And bend the 8th ring downward. This will make the lower end of the gap or entrance, as shown in the image.
	Now, tie the bent 7th and 8th rings firmly with steel wires
	Next comes covering the frame of the dome with chicken mesh.
	Use a metal scissor to cut the required size of the chicken mesh. Start covering the frame tightly with the mesh, from top to bottom.
[[Image:]] [[Image:]]	To tie the mesh to the frame, stretch the mesh tightly and tie it to the frame with steel wires. This can be done by using a metal hook. To tighten the layers of the chicken mesh- Insert the hook into the hole(s) of the two layers Rotate the hook by stretching the mesh and simultaneously entwining the mesh(es).
	Please note- if the chicken mesh is not stretched tightly then- cracks might appear later while plastering the dome.
[[Image:]]	Remember to leave an extra 4-5 inch of chicken mesh at the nape of the frame. Reason for this will be explained while fixing the dome on the digester tank.
[[Image:]]	The entire frame should be covered with 3 bundles of chicken mesh. This would form approximately 3 layers over the dome.
[[Image:]]	The multiple layers of chicken mesh will help to hold the cement firmly while plastering the dome.
[[Image:]]	Chicken mesh covering the entrance to the dome, should be cut with scissors.
[[Image:]]	What you see here is the mason getting inside the dome through the same gap or the entrance.
[[Image:]]	Once the chicken mesh is fixed, remove the bamboo sticks placed inside for support. Please note that the sticks have to be gently removed so as to not disturb the frame of the dome.
[[Image:]]	Do so carefully and slowly.
	The mesh dome is now ready and can be placed on the digester tank. Before shifting untie the 10 inch hammered steel rod from the base ring. And make sure of re-tying the loose ends of the mesh.
	This brings us to the the end of this tutorial of constructing a dome for the Biogas plant.
	Fixing of the dome on the Biogas plant will be explained in a later tutorial.
Slide 4 Summary: We have learnt: The step-by-step procedure to construct the dome of the Digester tank.	Let us summarize In this tutorial we learnt, Step-by-step procedure to construct the dome of the Digester tank.
Slide 5 Acknowledgements This video was created by: Spoken Tutorial project with inputs from Rural-ICT team IIT Bombay	This video was created by Spoken Tutorial Project with inputs from Rural-ICT team, IIT Bombay.
Slide 6 Acknowledgements More information on these projects can be found at these links http://spoken-tutorial.org/NMEICT-Intro http://ruralict.cse.iitb.ac.in/	More information on these projects can be found at these links. http://spoken-tutorial.org/NMEICT-Intro http://ruralict.cse.iitb.ac.in/ in
	Pictures and technology support: Courtesy: Bhagirath Rural Development Foundation Village- Zarap, Taluka- Kudal, Dist.- Sindhudurg
	This is Bella Tony along with the animation team of the Spoken Tutorial project signing off. Thank you for joining.

Contributors and Content Editors

Bellatony911, Nancyvarkey