INSPECTIONS OF NOZZLES OF PRESSURE VESSELS
The inspection during setup (In process Inspection) and inspection during final dimensions is two
different activities. In process Inspection is the inspection before welding in which checking of given setup is to be correctly set-up as per given engineering drawing or not and
final inspection is the inspection after welding so this are two different
activities. The pressure vessels or column is closed container and design in
order to hold different gasses, liquids so the inspection is main parameter in design and fabrication point of view in pressure vessels.
Basically, inspection is main activity in pressure vessels, because in inspection consisting large number of activities includes different attachments like (Pipe Cleats, Platform Cleats, Lugs, Nozzles, Openings Welding of parts, Insulation Rings etc.) So the dimension is the main part of inspection of pressure vessel or column.
The Picture of nozzle welded on vessel shown below for reference,
Pic.01
We learn about how to check nozzles during in-process and final dimensions. So first thing is that during inspection of nozzles following main parameters to be checked as,
1) Projections
2) Nozzles data
3) Orientation
4) Elevations
1) Projections of Nozzles:
Projections
is checked simply with help of measuring tape from nozzle flange face to the
center-line of the vessel or column and the required projections are given in engineering
drawings. For example, if we want to check the projections of the nozzles (For example N-1A) see
below figure,
Pic.02
In above figure we see the projections given as 1650mm from flange face to V.C.L. (Vessels Center Line) Generally required projections given in appropriate engineering drawings
In above figure the S.R. Neck(Self
Reinforced Nozzle) Welded with WNRF Flange (Weld Neck Raised Face) and the
projections are given so we can check the projection of given nozzle named as N-1A by measuring tape from flange face of nozzle to center-line of the vessel or column.
i) Tolerance for Projections of Nozzles :
The acceptance for measuring projections
of nozzles is not addressed in ASME SECTION VIII DIV. 1 but as per Pressure
Vessel handbook it is to be considered as ±6mm so as per above figure or dimensions from engineering drawings the
required projections is 1650mm so if the actual measurement is vary between
±6mm then only the given nozzle projections is acceptable otherwise required to rectify and
reoffer for the inspection.
2) Nozzles Data :
During inspection or Final dimensions of the nozzle it is quality inspector’s duty to check either correct nozzle is attached/welded to the vessel or not, the things to check is that, nozzle Material Identification Mark, ProperSize, Schedule or Thickness, Rating and Type of nozzle (WNRF/S.R. NECK/LWNRF) and all parameters are mentioned in form of table in engineering drawing for reference see below figure for the data of nozzles,
Pic.03
Above
table is typical view of nozzle data in engineering drawing so its inspector’s
duty to check all data like correct rating of nozzle is to be setup/welded or
not and other parameters as shown in table. One thing is noted that the nozzle
is already inspected by inspection department as material identification so
during inspection of nozzles its Quality Control department's duty to check the correct type of nozzle is
to be setup/welded or not.
In above table Mark column contein 1A, Qty as 1, 16mm Thk.,size 400NB (NB:Nominal Bore) 150# Rating and type of nozzle as S.R.+WN.
3) Orientation of Nozzles :
Basically orientation of nozzles it means the
degrees on which nozzle to be attached/welded on vessel or column. The Orientation of
nozzles is measure simply by measuring tape. The typical measurement of outside
diameter of vessel as shown below,
Pic.04
So the
orientation of nozzle checked simply by measuring tape from centre-line of
nozzle to the nearest main degree of vessel or column.The orientation of nozzles given in engineering drawing.
For reference Typical view of Orientation of nozzles given in Engineering Drawing like this as shown below figure,
Pic.05
In above
figure Nozzles N-1A is at 20 degree so for checking the orientation of N-1A we
measure distance between nearest main degree of vessel as 0 degree to degree of nozzle that is 20 degree. so difference between this is 20-0 = 0 degree.
Firstly We
calculate the ODCF (Outside Diameter Circumference) of the Vessel for example if The vessel of ID 2000mm and
Thickness 24mm or OD (Outside Diameter) 2024mm.
firstly
If Inside Diameter given adding the 2 times of thickness to ID to get O.D.
So, (ID + 2 X
Thk. of Shell)
(2000 + 2 x
24) = 2000+48 = 2048mm
If Outside Diameter is given Or O.D. = 2048mm
Now we
multiply OD to π because we calculate circumference,
so ODCF = 2048 x 3.142 = 6434.81mm
So ODCF divide by 360 to get measurement of 1 degree as,
6434.81 / 360 = 17.87mm Degree so the measurement of 1 degree is 17.87mm
The distance Between main degree of vessel as from 0 degree to Nozzle 1A ie 20 Degrees
20 x 17.87 = 357.40mm.
i) Tolerance for Orientation of Nozzles:
The acceptance for measuring the Orientation of nozzles is not addressed in ASME SECTION VIII DIV. 1 but as per Pressure Vessel handbook it is to be considered as ±1 Degree so if measured readings within tolerance limit then only acceptable otherwise required to rectify.
4) Elevation of Nozzles :
The elevation of nozzles means at certain placement on which nozzle is attached in other-words the measurement between nozzles to other attachment or center line or nozzle center-line to T.L. (Tangent
Line). The elevations of all nozzles specified in appropriate engineering
drawings. The typical sample for elevation of nozzle N-1A shown below figure,
In above figure the elevation given is 1080mm From
T.L. (Tangent Line) So during inspection for checking elevation we required to check
distance from center-line of nozzle to T.L.(Tangent Line) by measuring Tape.The elevations given in appropriate engineering drawings.
i) Tolerance for Orientation of Nozzles:
The acceptance for measuring Elevation of
nozzles is not addressed in ASME SECTION VIII DIV. 1 but as per Pressure Vessel
handbook it is to be considered as ±6mm so if measured readings and found within
tolerance then only acceptable otherwise required to rectify.
So the Tolerance sheet provided by client as per
requirements or code requirements but if not then by practice we take tolerance as per vessel handbook.
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