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

Time	Narration
00:01	Hello everyone!! Welcome to this Spoken Tutorial on construction of the dome of the digester tank.
00:08	The tutorials on digging of the pit and laying the foundation are available on Spoken-tutorial.org website.
00:18	In this tutorial, we will learn the step-by-step procedure for constructing a dome.
00:26	So, what is a dome?
00:28	Dome is an arch like structure placed on the digester tank where the biogas is collected.
00:36	Construction of the dome is a very interesting and important procedure.
00:43	Items used for construction are steel rods, chicken mesh and steel wire.
00:51	Detailed specifications of these are mentioned in the tutorial on materials required.
01:00	Let’s begin. First, make a circle of 7 feet 6 inches diameter with lime powder.
01:08	Now, put 12 marks on the circumference of the circle and number them from 1 to 12, as shown.
01:19	These 12 marks should be separated by a distance of two feet from each other.
01:27	Next, hammer twelve 10-inches steel rods all along the marked circumference.
01:35	Hammer 10-inches steel rods up to 2 inches in the ground.
01:42	Remember that they have to be removed later.
01:48	Next comes the use of 12-feet long steel rods.
01:53	With the 12-feet long steel rods, we’ll make an outer circle around the hammered 10-inches steel rods.
02:02	I will now tell you how to make a circle using the hollow rod.
02:08	Use an iron rod having hollow ends.
02:12	With this iron rod, bend the 12-feet steel rods to form a circular shape.
02:19	Then place the circular steel rods around the smaller 10-inches steel rods, as shown.
02:28	We will need two 12 feet rods to complete the circle.
02:33	Now tie the circular steel rods to the 10-inch steel rods using steel wires, as shown.
02:42	Ensure that the knot is tied very tightly and the steel rod circle is very stable.
02:49	This is the base of the dome.
02:52	Hence it has to be very strong to bear the load of the plastered dome later.
02:58	Now, hammer a 4-feet and 2 inches long bamboo stick in the center of the circle, as shown.
03:06	Hammer the bamboo stick up to 2 inches in the ground.
03:11	Ensure that it can stand firmly by itself and can be easily removed later.
03:18	This bamboo stick should be able to temporarily support the frame of the dome.
03:24	Now, let’s start building the frame of the dome.
03:27	Again, use the hollow iron rod and bend a 12-ft long steel rod to form an arch like shape.
03:37	This arch will give the semi-circular shape to the dome.
03:41	Hence, ensure that the arch is symmetric on either side when bent.
03:48	Similarly, bend 2 more 12-feet rods to form arches.
03:55	Let me explain exactly how the arches have to be placed on the circumference using a diagram.
04:03	Secure one end of the arch at rod number 1 and the other end of the arch at rod number 7.
04:11	This will ensure perfect symmetry to the arch and it will rest on the bamboo stick in the centre.
04:19	Use steel wires to tie the arch together with the hammered 10-inches steel rod and the circular ring.
04:28	For tying, make a knot like structure with the steel wire, as shown here.
04:35	Do likewise at the opposite end of the arch as well.
04:40	Next we will tie two more arches.
04:44	Secure the second arch to rod number 3 and rod number 9.
04:50	And, secure the third arch to rod number 5 and rod number 11.
04:57	The 12 feet steel rod arches should be at an angular separation of 60 degrees at the base.
05:07	Now, we have three arches for the frame of the dome.
05:12	Next, carefully slide the steel rods at the top such that a small gap is left open in between.
05:22	Tie the steel rods using the steel wires as shown.
05:27	Intersection of the three arches will look like a triangle.
05:32	The sides of the triangle should be approximately 2.5 inches as shown in the image.
05:40	The top view of the framework should look like this after tying.
05:46	What you see here is the mason showing the exact position of the open triangular gap using the bamboo stick.
05:54	This gap is where the main gas pipe of 1 inch diameter will fit.
06:01	Once the arches have been fixed, we have to make circular rings with the remaining 12-feet steel rods.
06:11	First let us understand how to make these rings with the help of a diagram.
06:17	This is the framework we constructed so far,
06:21	circular base and semi-circular arches.
06:26	Now we need to fix 8 circular rings such that they can be placed on the arches, as shown.
06:34	The rings have to be uniformly separated by a distance of 8 inches between each of them.
06:43	To make circular rings, start from the top and gradually move downwards.
06:49	Two things to keep in mind while making circular rings are:
06:54	the length of the steel rod would depend upon the position of the circular ring on the frame.
07:02	longer steel rods would be required as we gradually go from top to bottom.
07:09	We will first have to cut the steel rods to the required length before we fix the rings.
07:16	So, let’s do that.
07:18	For the first ring which is the smallest ring at the top, we will need approximately 4 feet and 7 inches steel rod, adding 2 feet extra for tying.
07:33	Diameter of this circular ring will be 10 inches.
07:39	For the second ring, we will need approximately 7 feet and 1 inch of steel rod.
07:47	Diameter of this ring will be 1 foot and 7 inches.
07:53	For the third ring, 9 feet and 8 inches steel rod would be required;
07:59	diameter would be 2 feet and 5 inches.
08:04	Fourth ring will require 12 feet 3 inches long steel rod;
08:11	diameter of this ring will be 3 feet and 3 inches.
08:15	The fifth ring will need 14 feet and 10 inches long steel rod;
08:21	diameter of this ring will be 4 feet and 1 inch.
08:27	Sixth ring will require 17 feet and 4 inches long rod;
08:33	diameter of this ring will be 4 feet and 10 inches.
08:39	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.
08:54	And the diameter for all the 8 rings is calculated excluding the 6 inches.
09:02	Now come the 7th and 8th rings.
09:06	Both will be used for making the circular rings and also the entrance of the dome.
09:13	Measurements for these two rings are-
09:17	The seventh ring will require 20 feet and 10 inches long steel rod.
09:23	And, for eighth ring 23 feet and 5 inches long steel rod would be required.
09:31	Keep in mind that this includes the measurement for the bent rods as well.
09:38	As soon as three circular rings are placed, an important thing to be done is:
09:45	Place 6 bamboo sticks of length 4 feet in an inclined position inside the frame of the dome.
09:54	Note that bamboo sticks have to be spread out uniformly from the centre of the base.
10:02	And, should be firmly rested against the circular rings or the arches.
10:09	These sticks will further give support to the frame of the dome.
10:14	Please note that if you follow the measurements mentioned earlier then you will get a uniform distance of 8 inches between each circular ring.
10:26	To confirm this, use a 1 foot steel scale having two hooves.
10:32	The distance between these two hooves should be 8 inches
10:37	and it should fit in between two circular rings as shown here.
10:43	However, you may ignore minor variations, if any.
10:48	Just after placing the 6th circular ring, an important thing to be done is to fix vertical rods on the frame.
10:58	I will explain how to do that:
11:01	Between two half-arches, fix a steel rod of length 5 feet and 5 inches bisecting the two main arches.
11:13	Tie this rod using steel wires from the base ring up to the first ring as shown in the image.
11:22	Similarly, fix two more steel rods of 4 feet and 7 inches, bisecting the half-arch and the 5 feet and 5 inches steel rod.
11:36	Tie these two rods using steel wires from the base ring up to the second ring, as shown.
11:44	Please note- between the 5th and 6th 10 inches hammered steel rods, do the following:
11:52	The 4 feet 7 inches long steel rod has to be bent and tied to the 6th ring.
12:00	This is done to make space for the entrance of the dome as shown in the image.
12:06	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.
12:17	Now we will fix the last two circular rings i.e. the 7th and 8th ring.
12:23	However, it is to be noted that between 6th and 8th ring will be the gap or the entrance to the dome.
12:32	This gap should be big enough for the mason to enter inside the dome.
12:39	Size of this gap would be approximately 2 feet of width and 2 feet of height.
12:47	Use 7th and 8th rings to make gap of the mentioned size.
12:53	Bend the 7th rod to make the upper side of the entrance, as shown in the image and bend the 8th ring downward.
13:04	This will make the lower end of the gap or entrance as shown in the image.
13:10	Now, tie the bent 7th and 8th rings firmly with steel wires.
13:17	Next comes covering the frame of the dome with chicken mesh.
13:23	Use a metal scissor to cut the required size of the chicken mesh.
13:29	Start covering the frame tightly with the mesh, from top to bottom.
13:35	To tie the mesh to the frame, stretch the mesh tightly and tie it to the frame with steel wires.
13:45	This can be done by using a metal hook.
13:49	To tighten the layers of the chicken mesh-insert the hook into the hole(s) of the two layers.
13:57	Rotate the hook by stretching the mesh and simultaneously entwining the meshes.
14:04	Please note- if the chicken mesh is not stretched tightly then cracks might appear later while plastering the dome.
14:15	Remember to leave an extra 4-5 inches of chicken mesh at the nape of the frame.
14:23	Reason for this will be explained while fixing the dome on the digester tank.
14:29	The entire frame should be covered with 3 bundles of chicken mesh.
14:35	This would form approximately 3 layers over the dome.
14:40	The multiple layers of chicken mesh will help to hold the cement firmly while plastering the dome.
14:48	Chicken mesh covering the entrance to the dome, should be cut with scissors.
14:53	What you see here is the mason getting inside the dome through the same gap or the entrance.
15:00	Once the chicken mesh is fixed, remove the bamboo sticks placed inside for support.
15:07	Please note that the sticks have to be gently removed so as to not disturb the frame of the dome.
15:15	Do so carefully and slowly.
15:18	The mesh dome is now ready and can be placed on the digester tank.
15:24	Before shifting, untie the 10 inches hammered steel rod from the base ring
15:31	and make sure of re-tying the loose ends of the mesh.
15:36	This brings us to the end of this tutorial of constructing a dome for the biogas plant.
15:44	Fixing of the dome on the biogas plant will be explained in a later tutorial.
15:50	Let us summarize. In this tutorial, we learnt the step-by-step procedure to construct the dome of the digester tank.
16:00	This video was created by Spoken Tutorial Project with inputs from Rural-ICT team, IIT Bombay.
16:08	More information on these projects can be found at these links.
16:17	This is Bella Tony along with the animation team of the Spoken Tutorial project, signing off. Thank you for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14