(i) Three holes of diameter 52 mm (size of GI pipe)
and a small hole to insert vacuum valve are made
on to an outer container.
(ii) Three holes of 52 mm diameter are also made in
middle container and after inserting GI pipes into
it, these are welded together with outer container
as shown in Figure 3.
(iii) A lid of diameter same as that of middle
container is taken and a hole of 186 mm is made
to fix the inner container (to hold the cooker).