 |
Gandhi Tubes |
|
Other Tubes |
Raw Material |
Prime Quality raw material from leading European Mill. Raw Material is out of Fully
Aluminium Killed steel to ensure resistance to ageing & fine grain structure
required for High Degree of reliability |
|
Cheap raw material with less reliability. Generally carbon content in raw material
is very high resulting in hard tubes prone to cracking while forming operations
like bending/flaring etc. |
Plant & Machinery |
Project setup in Technical collaboration with M/s Benteler of Germany with state
of art plant. Critical equipments imported from Germany. |
|
Improper Technology & inadequate manufacturing facility. |
Annealing / Normalizing |
As per the specifications En 10305-1+N (NBK as per DIN 2391) the normalizing of
he tubes should be done above upper critical transformation temperature i.e. above
880 deg. Centigrade. Tubes at Gandhi tubes are normalized / annealed above 900 deg.
Centigrade). This results in uniformly soft and ductile tubes. |
|
Tubes are heat treated at 700 to 750 Deg. Centigrade temperature, which is the furnace
temperature, actual material temperature is even less. Low temperature heat treatment
is done to reduce scale. However tubes still have varying degree of scale &
results in improper normalizing resulting in hard tubes prone to crack. |
Surface & Mechanical Properties |
Tubes are Annealed / Normalized in Roller Hearth continuous Bright Annealing Furnace,
so the tubes are consistently Bright, soft & ductile. |
|
Improper heat treatment may result in cracks. Tube surface has varying degree of
scale.
|
Surface Roughness |
Tubes are Normalized / Annealed in Bright Annealing furnace so no scale formation
while annealing / normalizing. The Surface Finish of the tube is Bright & surface
roughness of the tube well below 4 micron Ra value as required as per EN 10305-1
(as per DIN 2391 surface roughness required below 6.3 micron Ra value.)
|
|
Roughness values are not monitored & do not meet specification limits. |
Pickling |
Tubes are Bright Annealed under reducing atmosphere in imported state of the art
German continuous Roller Hearth Furnace where there is no scale formation while
annealing.
Tubes are absolutely bright & scale-free after annealing & they are subsequently
oiled for rust prevention. Hence there is no need to pickle Tubes.
In Hydraulic System only Bright Annealed tubes are recommended. |
|
Because of non-availability of proper Bright annealing technology tubes need to
be pickled to remove rust/scale inside the tubes as scale inside tubes keep on coming
out under high pressure, contaminating hydraulic oil.
However since pickling is done with acid, acid residue remains inside the tubes
even after rinsing etc. This causes even more rust & contamination after some
time.
In Hydraulic System, contamination is a major issue as contamination in Hydraulic
oil can damage Hydraulic Pump & Valve. With recent technological upgrade to
electronically controlled pumps & valves contamination in Hydraulic oil has
become even more significant issue. |