String Book - Logan Oil Tools

6
Worn eLevatorS, tooL jointS,
LinK armS anD LinK earS
how to Measure Wear on Elevators and tool Joints
It is obvious that visual inspection cannot suffice for most
elevator checks. To measure link arms it is necessary to
use calipers and to read the result on a rule. Since significant
wear is restricted to the top link arm, it is here that
the measurement is taken.
Hinge pins, latch pins, and socket holes are not normally
measured for wear in the field. When it becomes apparent
that the hinge or latch pins are loosening, the elevator
should be sent to the factory for a general engineering
check-up.
For square-shoulder elevators, a rule marked in sixteenths
of an inch is adequate. The straight edge of the rule is
used to check the squareness of the top bore, and the
end is inserted into the worn pockets and ridges. Wear
of 1/16 in. or more should require re-facing of collar surface.
The squareness of tool joints (where collar meets
the pipe) may be checked using the right angle formed
by the rule end. Joints out of square by 1/16 in. or more
should be reconditioned or replaced according to recommendations
of manufacturer.
Determining wear of the 18° taper elevator and tool joint
is more difficult. As shown in Figure 1, an arm containing
a true 18° surface is extended into and matched against
the elevator bore. At the top of the bore, the actual angle
is read off a protractor attached to a straight edge. The
same principle is used for tool joints. In Figure 2, the
straight-edge is placed on top of the tool joint and the true
18° surface is placed along the tool joint taper.
Figure
Figure
Figure . To measure elevator taper, a true 18° surface
is inserted on an arm into the elevator bore and matched
against the taper. Result is read on a protractor attached
to a straight-edge.
Figure . To measure tool-joint taper, a true 18° surface
is matched against the taper and the result read on a protractor
mounted on a straight-edge at the top of the tool
joint. Hardbanding should also be checked for violation
of this taper.
Since these tapers do not wear evenly, it is necessary to
use the smallest angle of contact found.
Inspection gauge for Elevators and tool Joints
Recognizing the importance of an accurate measurement
and appreciating the difficulty in constructing an instrument
as described, Cooper Industries, Inc. has engineered and
manufactured a permanent aluminum gauge.
This instrument permits many measurements and calculations
without reference to supplementary data.
Evaluation of Wear
Once the degree of wear has been ascertained, the evaluation
is conducted as follows:
The effect of wear on 18° taper elevators and tool joints
may be determined by using Figure 3. Entering chart at
actual angle of taper, read across to diagonal reference
line and down to base of chart. The result is the percentage
to which an elevator capacity is reduced by such worn
tapers. Example: Inspected tool joint was found to have
a taper of 13°. As it was to be used with a perfectly sound
250-ton elevator, the elevator capacity was reduced to
78%, or 195 tons.
Measured Angle of Taper (deg)
2
4
6
8
10
12
14
16
18
100 90 80 70 60 50 40 30
Percentage to which Rated Capacity is Reduced
Figure
Figure . Percentage to which elevator capacity is reduced
by wear of elevator and tool-joint tapers is shown in this
chart. To use the chart, locate actual angle of taper at
left, read across to diagonal reference line and down to
per-centage at base of chart.
periodic Inspection (See ApI Rp8B)
This examination, as outlined below, whether conducted
in the field or shop, should be made using calibrated
instruments to determine any deviations from the manufacturer’s
technical data for original parts.
Square Shoulder Collar-type Drill pipe, Casing,
and Standard tubing Elevators: Inspect the collars for
squareness, and uniformity and depth of wear. Uneven
wear, or worn recesses of 1/16 in. or more, requires refacing
of collar surface. Hinge pins and springs should be
carefully inspected visually for excess wear and obvious
weakness.
8° taper-type Elevators: Inspection is the same as for
square shoulder, except that the conical bore should be
observed and measured (in many instances this check
should be more frequent.) All tool joints used with these
elevators should be measured. Amount of wear should be
checked with chart, Figure 3. In addition to the angle of
taper, hardbanding should be checked to see if it extends
beyond the taper. Any straight-edge may be used for
this purpose.