FABRICATION AND WELDING ENGINEERING

FABRICATION AND WELDING ENGINEERING

This paper consists of a case study with questions.
The case study is based on a sketch (Figure 1).
Attempt ALL questions, using the information provided in the Resource Pack
where appropriate.
CASE STUDY
Figure 1, on
Page four,
illustrates details of a fabricated and welded Pressure Vessel End
with a 12 mm thick “set-on” Pipe. The Pressure Vessel End has to be manufactured from
12 mm thick carbon steel with a composition as shown in the table below.
Material Composition:
Carbon Silicon Manganese Nickel Chromium Molybdenum Copper
(C) (Si) (Mn) (Ni) (Cr) (Mo) (Cu)
%%%%% % %
0·15 0·10 1·50 0·10 0·40 0·40 0·10
The welds for the manufacture of the component are to be produced in the flat position
using the Metal Active Gas Welding Process (MAG), solid wire.

1.
In the Metal Active Gas (MAG) welding process:
(
a
) explain how the shielding gas protects the weld pool from
contamination;
(
b
) name the output characteristic for the type of power source used;
(
c
) state how the current is controlled;
(
d
) state the function of the following items of MAG welding equipment:
(i) Contact tip;
(ii) Wire Drive Unit;
(iii) Harness.
2.
Interpret the
two
weld symbols as shown in Figure 1.
Remainder
Iron with
acceptable
limits of
impurities
Page three
3.
(
a
) Using the information detailed in the material composition table,
calculate the Carbon Equivalent of the material used for the manufacture
of the Pressure Vessel End.
(
b
) Determine the pre-heat temperature for the weld shown between the
Pipe and the Pressure Vessel End in Figure 1.
Note:
Assume a heat input of 1·1 kJ/mm.
(
c
) A partially completed Welding Procedure Specification is provided in
Worksheet Q3(
c
)
. Complete this specification for the weld shown
between the Pipe and the Pressure Vessel End in Figure 1 by inserting
the correct information in the boxes marked with an asterisk (*).
4.
Produce a planning operations sheet for the manufacture of the Pressure
Vessel End. The operations sheet should include information on each of the
following:
• appropriate sequence of operations
• marking out
• cutting and forming processes
• joining and assembly processes
• inspection.
The operations sheet should be appropriately designed.
5.
(
a
) During service the Pressure Vessel End is subjected to tensile stresses.
Explain the meaning of this term.
(
b
) After manufacture the Pressure Vessel End has to be normalised.
Describe how this process would be carried out.
6.
During service the external shell of the Pressure Vessel is exposed to
corrosive conditions and requires surface protection.
(
a
) State
two
methods of preparing the component for surface protection.
(
b
) State
two
suitable methods of surface protection.
7.
Magnetic Particle Inspection (MPI) is used to test for cracking in the welds.
Describe the procedure for carrying out this process.