IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
Each plumbing line consists
of 12 components made of
SS316 material, The Overall
size of the assembly is 2232 x
1155 mm. The critical
requirement is leak tightness of
the assemblies in the order of 1
x 10 -10 mbar * l /s and 100 %
radiography on all welds.
To achieve this task,
meticulous process planning,
selection of the optimum
parameters for machining the
components precisely in
different machines to meet the
stringent dimensional
tolerances were selected.
Fig.1 Beam chamber and cryostat vacuum plumbing lines
Unique layout was prepared to Liquid Penetrant Inspection,
for each assembly, stage 100% Radiography and Final
inspection , fit up of Assembly was subjected to
components, assembly and Helium leak test to 1 x 10-10
welding by GTAW process was mbar * l /s and found
used to minimize distortion. All satisfactory.
the weld joints were subjected
VII.2. Machining of Iron Thimbles for Fabrication of
Electrochemical Carbon Meters
Thirty numbers of Amco Iron
thimbles were machined
precisely for fabrication of
electro chemical carbon meters
(Fig.1). The thimbles are made
up of soft Armco Iron material
of size OD 19mm, ID 16mm
and 90mm length. The critical
dimension of 0.5mm wall
thickness was standardized for
rapid diffusion of carbon
through iron thimbles. Mockups
were carried out to
establish process sequence and
machining parameters to
achieve the critical requirement
of 0.5 mm uniform wall
thickness, close dimensional,
Fig.1 Machined iron thimbles
geometrical tolerances and machine the OD of soft iron
surface finish. The critical thimble to achieve 0.5 mm
machining of ID 16 mm ± 0.01 uniform wall thickness and to
mm was achieved by prevent possible damage
progressive machining using during machining and achieved
drilling, hole mill cutter and the dimensions within the
boring tool. A mandrel was tolerance of 0.01 mm.
designed to suit ID and used to
174 INFRASTRUCTURE FACILITIES