View source for Biogas-Plant/C3/Construction-of-the-Dome/English-timed


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|  '''Time''' 
|  '''Narration''' 

|- 
| 00:01
|  Hello and 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 and 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-inch steel rods all along the marked circumference. 

|- 
|01:35
|Hammer 10-inch 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-inch 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 degree 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. 

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|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. 
 
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|  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. 

|- 
|17:02
|* 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, 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 4feet 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 ring 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 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. 

|}