ALIGNMENT CHECKING
Basically, arrangement in s straight line
is called as alignment
1 1) Axis Alignment.
2 2) Surface Alignment.
1) AXIS ALIGNMENT:
The axis
alignment used for pressure vessel, column, storage tank for proper straightness
of whole job. Axis Alignment is checked with axis of job. The axis alignment
checked on respective four orientation of vessel by rotating the shells of vessel.
In axis alignment measure the perpendicular distance between plumb line and
horizontal line (See Pic.001) and record.
Diagrammatical
view of checking of Axis Alignment as shown below,
Pic.001
The reading record
as per table shown below,
Pic.002
The axis alignment
of vessel check by following method,
1) Firstly, plot the points on Graph paper
with suitable scale
2) Draw the best fit line to pass through all
points on graph.
3) The maximum distance measured from the line
is the maximum Out of Alignment.
4) Find
out maximum out of alignment in both the planes and note as (A) 0-180 Degree.
Readings 90-270 degree. Readings
Pic.003
5) Repeat the process for the same 90-270-degree orientation by rotating the
shell of vessel
2) SURFACE ALIGNMENT:
The typical example of measurement of vessel dimensions for surface
alignment as shown below,
Pic.004
The method of checking surface alignment as shown below,
1) Firstly, level the shell at
main degrees orientation (0,90,180 & 270 Degrees) vertically or
horizontally.
2) Drop the pair of plumbs near
each Circular seam and on both ends.
3) Put twins horizontally on both sides of shell.
4) Maintain equal distance at both
ends of sections between horizontal twins and plumb.
5) Then measure the perpendicular distance between other plumbs and horizontal twins and records the reading in table (See Pic.005) as shown below,
6) Rotate the job 90 degree and repeat the same process for the other orientations and record the readings.
Surface Alignment = Maximum
Reading – Minimum Reading.
Pic.005
Surface alignment for different
shell Thickness:
The dimension settings at
ends and decided taking in to consideration of shell thickness (See Pic.006)
and for remaining repeat the same procedure.
Pic.006
Important Note : The shell or ovality of the shell shall be controlled within the limit in order to get better alignment of Job.
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