FIELD OF INVENTION
The present invention relates to a measuring device for measurement of 'V'-
groove wall thickness of impeller disc of compressor by modification of a vernier
caliper.
BACKGROUND OF THE INVENTION
Impeller is the vital rotary part in the functioning of the compressor. Impeller is
manufactured by welding two different parts i.e. disc and counter disc. The fluid
(gas or air) enters the impeller axially at the eye of the impeller and then flows
radially out of the impeller. The gas goes through the diffuser to the return
channel and further goes into the next impeller. It is one of the most stressed
components of the compressor, demanding highly precise manufacturing
methods. Each impeller is dynamically balanced and subjected to over speed
test. They are mounted, shrink fitted and keyed on the shaft, which is coupled to
an external source (generally electric motor). This source imparts the required
energy and makes it to rotate. In an impeller, the energy transferred is in the
form of kinetic energy, which is then converted into pressure energy in the
diffuser. The pressuring ratio of any compressor depends mainly on the impeller
diameter, rotational speed and volume flow.
'V'-Groove' wall thickness of 1.5 mm ± 0.05 mm of each and every impeller disc
to be externally welded is being checked by an outside micrometer before TIG
welding. In the present method it is only possible to check the impeller groove
(DISC) dimension upto 20 mm. length from outside diameter of Impeller.
DISADVANTAGE OF THE PRESENT METHOD
In the present method if 'V' groove thickness is more that 1.5 mm beyond 20
mm from outer diameter of Impeller disc and if this is not checked properly and
finally corrected, there will problem in welding.
Hence there exists a problem and a need to invent a new measuring device to
solve the problem.
OBJECT OF THE INVENTION
Therefore, an object of the invention is to propose a measuring device for
measurement of 'V'-groove wall thickness of impeller disc of compressor by
modification of a vernier caliper which is capable of measuring the wall thickness
of the 'V' groove beyond 20 mm from outer diameter of impeller disc.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l - shows the method of measuring the thickness of V-groove in prior
art using screw gauge.
Fig.2 - shows the method of measuring the thickness of V-groove using
the modified vernier calipers, according to the invention.
Fig.3 - shows the modified vernier calipers.
Fig.4 - shows view of the impeller Disc.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
An old vernier caliper is modified as shown in fig.3. The new measuring device
(1) having the old vernier scale (8) is made of two long Jaws. One is a fixed jaw
(2) and the other is a moveable jaw (3). These Jaws are made of steel bars of 12
mm square x 100 mm length. Both these Jaws are welded to the existing jaws of
the old vernier caliper. An anvil (4) made of high speed steel bar of 6 mm
diameter is fixed on the fixed jaw (2) and a spindle (5) made of high speed steel
bar of 6 mm diameter is fixed on the moveable jaw (3). Both these anvil and
spindle is properly heat-treated and ground before brazing them in the Jaws.
This modified measuring device (1) is capable of checking the entire length of
groove wall thickness (6) on the impeller (7). With this device any variation in
the wall thickness can be easily detected before welding and necessary changes
in the welding parameters can be made to achieve good fusion between discs
and counter disc. Thus the quality of welding is improved.
Beyond 20 mm from outer diameter of disc, if turning of disc is not done
correctly this measuring device can find out the discrepancy and the groove
material thickness at bottom can be rectified by turning operation. It means that
beyond 20 mm from outer diameter of impeller disc, if the material thickness is
found say 1.8 mm by the device (1) then it can be turned and made to 1.5 mm.
WE CLAIM
1. A measuring device (1) for measurement of 'V'-groove wall thickness of
impeller disc of compressor by modification of a vernier caliper
comprising;
a vernier scale (8);
Characterized in that,
one fixed jaw (2) and one moveable jaw (3) welded to the old jaws of the
vernier caliper (9, 10) for making the device accessible to check the
impeller groove thickness beyond 20 mm from outer diameter wherein an
anvil (4) and a spindle (5) are fixed to the jaws (2, 3) for taking the
necessary measurements.
2. A measuring device as claimed in claim 1, wherein the fixed jaw (2) and
moveable jaw (3) are made of steel bar of 12 mm square and 100 mm
length.
3. A measuring device as claimed in claim 1, wherein the spindle (4) and
anvil (5) are made of high speed steel bar of 6 mm dia.

ABSTRACT

A measuring device for measurement of 'V" groove wall thickness of impeller disc
of compressor comprises of a vernier scale of a old vernier caliper having the two
original jaws welded with 12 mm square rod of 100 mm length for making an
extended jaw when an anvil and a spindle is brazed to the jaws to facilitate the
measurement. Out of two jaws, one is a fixed jaw and other is moveable.