railway training

1. WELDING SHOP
Welding is the process of joiningof two similarmetals or dissimilar
metals.
In welding shop we mainly saw two types of welding which is oxy fuel
gas welding and consumable electrode arc welding process.
Arc Welding-an arc is produced between the tip of the electrode and
the work piece to be welded by the use of an AC or a DC power supply.
This arc produces temperatures of about 30000 deg Celsius much
higher than those developedin oxy fuel gas welding. Shielded metal
arc welding is the most commonly used welding method.
SMAW:-SHIELDED METAL ARC WELDING
 Used in general construction and maintenancework
 Portable and easily maintained
 Useful for work in remote areas where portablefuel power
generator can be used as power supply
 Best suited for work piece thickness 3mm-19mm
OFW:-OXYFUEL GAS WELDING
It is used for structural sheet metal fabrication,variousrepair works.
The welding process uses a fuel gas combined with oxygen to produce
flame. The flame is source of heat that is used to melt the metals at the
joint. The process utilizes the heat generated by the combustion of
acetylene gas in a mixture with oxygen.
C2H2 + O2 =2CO + H2 + heat

2. OFC-OXYFUEL GAS CUTTING
A piece of material can be separated into two or more pieces or into
variouscontours by the use of a heat source that melts and removes a
narrow zone in the work piece. The sources of heat can be torches,
electric arcs, or lasers.
The heat source is now used to remove a narrow zone from a metal
plate or sheet. Heat is generated here and it can produce a
temperature rise to about 8700
C. However, this temperature is not
sufficiently high to cut steels, so the work piece is preheated with fuel
gas, and oxygen is introduced later. Cutting occurs mainly by the
oxidationof the steel; some melting also take place.
OVERVIEW:-
 Max thickness cut is about 300mm to 350mm with oxyacetylene
gas
 With oxy hydrogen about 600mm
 Kerf width ranges from 1.5mm to 10mm