Note: Descriptions are shown in the official language in which they were submitted.
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METHODS OF BUILDING UP A PIPE WALL
TECHNICAL FIELD
[0001] Disclosed are methods and apparatuses for building up a pipe wall.
BACKGROUND
[0002] Welding is used to build up and repair used valves and directional
drilling
tools made of carbon steel, which is magnetic. Build-up is also carried out on
new and used
tools made of non-magnetic material.
SUMMARY
[0003] Methods of building up metal articles, such as pipes, by deposition
of weld
metal. The metal article may be made of stainless steel, such as non-magnetic
stainless steel.
Non-magnetic alloy metals may also be used.
[0004] A method of pipe build up comprising: rotating a pipe about a pipe
axis
relative to a welding tip directed towards an external wall of the pipe;
depositing weld metal
circumferentially about the external wall using the welding tip; supplying
coolant to an
internal wall of the pipe; and in which the pipe comprises one or both a non-
magnetic
stainless steel alloy containing nickel, or a non-magnetic steel alloy
containing nickel and
magnesium.
[0005] Another method of pipe build up comprising: rotating a pipe about a
pipe axis
relative to a welding tip directed towards an external wall of the pipe;
depositing weld metal
circumferentially about the external wall using the welding tip; supplying
coolant to an
internal wall of the pipe; and in which the pipe is non-magnetic and comprises
metal.
[0006] In various embodiments, there may be included any one or more of the
following features: Supplying flux to the external wall, in which weld metal
is deposited as
part of a submerged arc welding process. Shot peening the deposited weld metal
to harden
the deposited weld metal. Shot peening further comprises: rotating the pipe
about the pipe
axis relative to a shot peen nozzle directed towards the deposited weld metal;
and delivering
shot peen under pressure circumferentially about the external wall using the
shot peen
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nozzle. Coolant is supplied from a 360-degree nozzle located within the pipe.
Coolant is
supplied at conditions sufficient to maintain the temperature of the external
wall 100 degrees
Fahrenheit or more below a maximum temperature limit of the pipe. Coolant is
supplied at
conditions sufficient to maintain the temperature of the external wall between
200 and 500
degrees Fahrenheit. The non-magnetic stainless steel comprises 3-8% nickel and
5-15%
magnesium. The external wall has an indented wear area, and the weld metal is
deposited
over the indented wear area to repair the pipe. The pipe is part of a drilling
tool. Translating
the pipe along the pipe axis relative to the welding tip.
[0007] These and other aspects of the device and method are set out in the
claims,
which are incorporated here by reference.
BRIEF DESCRIPTION OF THE FIGURES
[0008] Embodiments will now be described with reference to the figures, in
which
like reference characters denote like elements, by way of example, and in
which:
[0009] Fig. 1 is a side elevation view, in section, of an apparatus used to
perform a
buildup method on a non-magnetic pipe.
[0010] Fig. 2 is a side elevation view, in section, of an apparatus used to
perform a
method of hardening a built up non-magnetic pipe by shot peening.
[0011] Figs. 3A and B are side elevation views, in section, of an apparatus
used to
perform a method of testing a built up pipe. The apparatus of Fig. 3A uses
outer ultrasonic
pads, while the apparatus of Fig. 3B adds inner ultrasonic pads.
[0012] Figs. 4 and 5 are side elevation views, in section of a built up
pipe (Fig. 4)
and a pipe (Fig. 5) with a faulty buildup portion removed.
DETAILED DESCRIPTION
[0013] Immaterial modifications may be made to the embodiments described
here
without departing from what is covered by the claims. % values for elements
such as nickel
and magnesium refer to volume / volume percentages.
[0014] Referring to Fig. 1, a method of pipe build up is illustrated. A
pipe 10 is non-
magnetic and comprises metal. In one case pipe 10 comprises one or both a non-
magnetic
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stainless steel alloy containing nickel, or a non-magnetic steel alloy
containing nickel and
magnesium. Example pipe compositions are given below. The pipe 10 is rotated
about a pipe
axis 12 relative to a welding tip 14. Pipe 10 may be rotated any number of
suitable ways. For
example, pipe 10 is mounted at an axial pipe end 20 to a rotating chuck 18. In
other cases
external wall 16 of pipe 10 may sit upon and be rotated by pipe rollers (not
shown). Welding
tip 14 is directed towards external wall 16 of pipe 10. Weld metal is
deposited
circumferentially about the external wall 16, for example over an indented
wear area 21,
using the welding tip 14. Indentation may be caused by wear from use. The
deposition of the
weld may create a collar 22 (build up) of weld metal about the hollow pipe 10.
While the
deposition is occurring, coolant 24 is supplied to an internal wall 26 of the
pipe 10.
[0015] The non-magnetic stainless steel may comprise 3% nickel or greater
(for
example 3-8% (such as 3%, 5% and 8% for example in the case of drilling tools)
up to 15%,
or more. Some inkaloids have 20-25% Ni. In some cases magnesium may be
present, for
example 5% or greater and in some cases 5-15% or up to 37%. Magnesium % may
increase
as nickel % increases. Magnesium may improve machining capability. Relative to
carbon
steel, stainless steel is more expensive but also more resistant to corrosion.
Thus, stainless
steel is used in various pipes, including pipes 10 forming part of drilling
tools used in the oil
and gas industry. Various stainless steels are non-magnetic, including
austenitic stainless
steels.
[0016] Material preparation for welding may include cleaning offal! foreign
material
from external wall 16. The base material should be clean, with no rust, scale,
grease, dirt or
product that may distort material bonding to the base material.
[0017] Weld metal may be deposited by a suitable welding method. Welding is
a
fabrication process that joins metals by causing coalescence. Welding is often
done by
melting adjacent workpieces and adding a filler material to form a pool of
molten material
(the weld pool) that cools to become a strong joint, with pressure sometimes
used in
conjunction with heat, or by itself, to produce the weld. Build-up material
may include wire
rod, flux, stick rod and powder. In the method shown in Fig. 1, weld metal,
such as wire 30
from a wire loop 32, may be fed to the tip 14 and coalesced with external wall
16 at the
welding site, which may be at an intermediate axial location along the pipe
length as shown.
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One or more motors (not shown) may be used to dispense wire 30 at a desired
rate. The wire
30 may comprise similar or identical material as the material of pipe 10 to be
welded, for
example stainless steel.
[0018] A submerged arc welding (SAW) process may be used to deposit weld
metal.
In such a method flux 28 is supplied to electrode 14 and external wall 16, for
example via a
flux hopper 32. In SAW processes the molten weld and arc zone are protected
from
atmospheric contamination by being submerged under a blanket of the granular
fusible flux
28. Suitable flux material may be used such as lime, silica, manganese oxide,
calcium
fluoride, and other compounds. When molten, the flux becomes conductive, and
provides a
current path between the electrode and the work piece. The layer of flux
covers the molten
metal and prevents spatter and sparks as well as suppressing ultraviolet
radiation and fumes.
Although SAW welding is mentioned, other types of welding may be used in the
disclosed
apparatuses and methods, for example plasma welding.
[0019] One or more or all aspects of the welding process may be automated.
For
example, flux 28 and wire 30 may be dispensed at a desired rate proportional
to one another
and the rotation speed of the chuck 18. A processor, for example in the
welding unit 34, may
be connected to send control signals to tip 14, hopper 32, and wire loop 32
for control
purposes. Welding unit 34 may also contain the components required to convert
an electrical
power input into the arc required to melt the weld metal and external wall 16
at the welding
site. The welding unit 34 may also be connected to send control signals to
chuck 18 to
execute all parts of the process automatically, for example to carry out a pre-
programmed
welding process selected for the particular work piece 10 to be repaired. One
or more
processors or controllers (not shown) may be used to control the process.
[0020] Pipe temperature during the process may be maintained to support
build-up
material bonding to the base material. Temperature control may be maintained
to support the
core temperature and thus the base material (pipe 10) from distorting. The
optimal
temperature may vary per base material make up. Temperature may be controlled
by fluid,
air, or mist contact and removal. Coolant 24 may be supplied to internal wall
26 via a nozzle
36, which may be directed at a portion 42, of internal wall 26, that underlies
an active
welding site 44 on external wall 16. Nozzle 36 may be a 360-degree nozzle 36
located within
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an interior of the pipe 10. The nozzle 36 may be a perforated tube 38 as
shown, with
perforations represented by dotted lines in the figure. A 360 degree nozzle
supplies coolant
circumferentially about the internal wall 26, thus providing cooling at the
active welding site
44 and even on portions of external wall 16 that are not being directly
welded. The nozzle
360 may be changeable, to permit removal and installation of different nozzles
sized
according to the ID of the pipe 10 being welded. The position of the torch
output point 36
may be adjusted throughout the process, for example moved along the axis 12 to
correspond
with relative motion of the welding tip 14.
[0021] In the example shown, the tube 38 is part of a supply line 39
that extends into
the interior 46 of pipe 10 through a bore 49 in an annular seal 48, seal 48
being seated within
or over end 20. In some cases nozzle 36 is positioned outside the pipe end 20
with or without
seal 48. Seal 48 may itself be, or may have bore 49 lined with, a rubber
gasket, about the
supply line 39. Bore 49 may form a dynamic seal with the supply line 39, so
that the pipe 10
rotates relative to the supply line 39. In other cases the nozzle 36 rotates
in sequence with the
pipe 10 and relative to the tip 14, and in other cases the nozzle 36 rotates
independently of
both the pipe 10 and tip 14 for example if the nozzle is designed to rotate
under application
of coolant fluid pressure.
[0022] In the example shown coolant runs into pipe via one end 20, along
the pipe
length, and exits pipe 10 via a second pipe end 50 opposite pipe end 20. In
other cases the
coolant may enter and exit the same pipe end 20, for example if a packer (not
shown) or end
plug (not shown) was positioned to block end 50 and seal 48 included an inlet
for line 39 and
an outlet for a spent coolant line.
[0023] Coolant is supplied to line 39 via a suitable coolant supply
system, which may
be open or closed, and may be once-through or recirculating. Coolant is pumped
into line 39
using a fluid pump 54 drawing coolant from a coolant reservoir 52. Heated
coolant 24
exiting pipe end 50 is expelled into a collection reservoir 56, and then
pumped via a cooling
pump 58, for example a vane type or propeller type pump, through line 60 into
a cooling
fluid tower or radiator 62. Cooled coolant passes through radiator 62 through
line 64 and
back into reservoir 52 for supply to line 39. Radiator 62 may incorporate a
heat exchanger
and a fan. Suitable devices other than radiator 62 may be used for reducing
the temperature
Date Recue/Date Received 2021-07-02
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of the heated coolant. A fluid controller 66 may be used to regulate the
operation of the
coolant system. In one embodiment a processor or the welding unit 34 is
connected to
operate the coolant system.
[0024] A suitable coolant may be used, for example a liquid such as a non-
water base
or water, or a gas such as air. In one case antifreeze is used, for example
selected with a
boiling temperature above the maximum temperature of the interior wall 26
achieved during
welding, to avoid coolant vaporization and unwanted deposition on the interior
wall 26.
Temperature may be measured via a temperature sensor 19, and fluid control
adjusted to
maintain the operating temperature within a predetermined temperature range.
One example
cooling fluid is an antifreeze type coolant, for example a green type coolant
with components
such as silicates and phosphates that inhibit corrosion, and having a 40/50
viscosity as
measured using a Marsh funnel test. Higher viscosity means increased heat
removal, but
greater difficulty to cool the heated coolant. A gel may be used in some
cases. Temperature
may be monitored and one or more operating parameters adjusted to compensate,
for
example the parameters listed in Table 1, or other parameters such as welding
parameters.
[0025] Coolant may be supplied at conditions sufficient to maintain the
temperature
of the external wall 16 to 100 degrees Fahrenheit or more below a maximum
temperature
limit of the pipe 10. Precise coolant monitoring and control may be required
to regulate the
external wall 16 temperature because the non-magnetic material absorbs height
relatively
fast compared to carbon steel. Coolant may in some cases be supplied at
conditions sufficient
to maintain the temperature of the external wall 16 to between 200 and 500
degrees
Fahrenheit. for example between 200 and 400 degrees Fahrenheit. If temperature
climbs
outside of the predetermined range, coolant flow may be increased in response,
or the action
of the radiator 62 increased to reduce the temperature of the incoming
coolant. By converse,
if the temperature falls below the predetermined range, coolant flow may be
decreased and
the action of the radiator 62 reduced. An example predetermined range is from
200 to 100
degrees Fahrenheit below the maximum temperature limit of the pipe. Different
materials
have different maximum temperature thresholds, and above such limits, the
material may
start to distort the makeup of the material, shape and composition. The
maximum
temperature limit may be the lower limit of hot working, which is generally
60% of the
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melting temperature, beyond which crystal structure changes may begin to be
observed.
With some inkaloids, temperature limits are higher, for example in the 900-
1000 degrees
Fahrenheit range. Temperature limits tend to increase as nickel % increases.
Limits of 200-
350 degrees Fahrenheit were observed on the 3-8% Ni-containing materials
tested.
[0026] During the welding process the pipe 10 may be translated along the
pipe axis
12 relative to the welding tip 14. Translation may occur to reposition the tip
14 and apply a
band of weld metal adjacent an already deposited band. Either the pipe 10 or
the tip 14 may
be moved to achieve the new orientation. Translation may occur during weld
metal
deposition or during an intermediate period where no weld metal is deposited,
for example to
create a spiral band pattern. The combination of rotation of pipe 10 and
translation may be
used to repair or otherwise build up a relatively larger section of the pipe
10.
[0027] Once the pipe 10 is built up and cooled to room temperature, further
processing may be carried out. The build-up area may be treated to support
hardness and
remove contamination. An example process to decontaminate material includes an
acid bath
(for example 1-10% acid content) and shot peening.
[0028] Referring to Fig. 2, in the example shown shot peening is carried
out on the
deposited weld metal 68 to harden the deposited weld metal 68. Shot peening is
a cold
working process used to produce a compressive residual stress layer and modify
mechanical
properties of metals. It entails impacting a surface with shot, for example
round metallic,
glass, ceramic, sand, and nonferrous or non-magnetic particles, with force
sufficient to create
plastic deformation. In one example stainless steel fragments are used as shot
and delivered
to the metal 68. During shot peeninu the pipe 10 may be rotated about the pipe
axis 12. For
example, pipe 10 may be mounted at an axial pipe end 50 to a rotating chuck
70. Other
suitable rotation mechanisms may be used. The shot peen 74 may be delivered to
the weld
metal 68 under pressure, for example circumferentially about the external wall
16, using a
shot peen nozzle 76. A peen house 72 may be supported by one or more ground
engaging
members such as legs 86. One or more dust collectors (not shown) may be used
with the shot
peening system. Shot peening may be carried out to an extent required to raise
the hardness
of the build up (deposited weld metal 68) to within 20% of the hardness of the
base material
(pipe 10)..
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[0029] The peen house 72 may be positioned partially or fully around the
pipe 10, to
shroud the portion of pipe 10 that contains the deposited weld metal 68 and to
contain and
collect shot expelled from nozzle 76. f he peen house 72 may have a top wall
78,
surrounding side walls 80, and a base 82, with an outlet 84, for example in
the base 82, for
collecting and removing expelled shot from house 72. The base 82 may be sloped
to direct
expelled shot by gravity into outlet 84. The pipe end 20, which extends into
peen house 72,
may be sealed with an end cap or plug 88, and a seal (not shown) may also be
provided
about pipe 10 at a pipe entry point 90 in the peen house 72, in order to
prevent expelled shot
from escaping the bounds of the peen house 72 except through outlet 84, which
may be a
perforated plate as shown by dashed lines. In some cases pipe 10 is entirely
contained within
the peen house 72 during shot peening.
[0030] Shot 74 may be cycled once through the system, or may be collected
and
recirculated as shown. The outlet 84 may be positioned at, or may be connected
to a hopper
92 that collects expelled shot 74 into a shot basin 94, after which the shot
74 is pumped
through one or more lines 98 by a shot pump 96 into and out of nozzle 76.
Thus, the shot
peen is recycled during use. In other cases shot is supplied via one or more
cartridge
mechanisms, or a hopper. Fluid pressure, for example from air pressurized by
pump 96, may
be used to transport and expel the shot 74 throughout the system. Other
suitable fluids may
be used.
[0031] Shot peening is used to harden the deposited weld metal 68 to obtain
a higher
hardness rating. For example, shot peening may be controlled to provide a
hardness of 20 to
25 or higher on the Rockwell scale, although the Brinell scale may be used.
Shot peening
provides an impact on the metal 68 surface intended to close up voids, densify
the metal 68,
and flatten the surface. In some cases shot of size 0.010" to .016" intensity
is used, with a
coverage of 150 % to 200%. C grade shot may be used, C grade having relatively
sharp-
edged beads in contrast to A grade, which is a round bead. Shot velocity may
average 560-
780 mm/second, at a coverage of 150%, and in some cases up to 200%. The
greater the
velocity, the greater shot impact on the surface, although shot peening above
a threshold
velocity will roughen the surface, potentially leading to erosion or non-
sealing when
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pumping fluid during use of the tool. In some cases, to close up voids and
keep the surface
smooth, a velocity range of 120-200 ft/sec is used.
[0032] Referring to Figs. 3A and 3B, after deposition, and shot peening of
the
deposited weld metal 68, the weld metal 68 may be subject to quality control,
such as a
visual inspection for flaws, a dye test under black lights checking for
cracks, or other testing.
For example the build-up area may be tested for the correct base and build-up
material
bonding and porosity. Testing may be destructive, non-destructive, or both.
[0033] In an example non-destructive test, the pipe 10 is subject to an
ultrasonic
bonding test. Ultrasonic testing is a family of non-destructive testing
techniques based in the
propagation of ultrasonic waves in the object or material tested. Ultrasonic
pulse-waves are
transmitted into materials to detect internal flaws or to characterize
materials. An example is
ultrasonic thickness measurement, which tests the thickness of the test
object, for example,
to monitor pipework corrosion. As shown one or both outer and inner ultrasonic
pads 100 or
102, respectively, may be positioned adjacent the deposited weld metal 68 and
connected to
an ultrasonic control unit 104. A thickness profile may be generated and
reviewed to identify
defects, if any.
[0034] Example partial destructive testing includes an acid test, which is
used to
analyze compositional variance between the build up and the base material
using wet
chemistry. 10% HCI may be applied to the base material and the build up, and
the color of
the resulting solution compared. Higher Ni content generally produces a blue
color, while
lower Ni content produces a lighter green color. A color difference indicates
a different
composition, and if the difference is sufficiently large the process may be
repeated using
weld metal of a composition more closely aligned with the composition of the
base material.
[0035] In some cases hardness may be tested. One non-destructive hardness
test is
the air injection test, where a head hits the material and the resistance is
quantified to
produce a Rockwell hardness amount. In a destructive hardness test a machine
is used to put
a dimple in the metal, and the depth of penetration is used to quantify
hardness.
[0036] In some cases a test pipe may be subjected to destructive testing,
of a nature
that brings the pipe to failure, to determine if a particular welding program
is suitable for the
composition of the pipe. For example, a test pipe was subjected to a visual
bonding
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inspection by slicing the pipe into pieces along planes perpendicular to the
pipe axis, passing
through the deposited weld metal 68 and the underlying pipe base. At the
transition point
where welding occurred the matrix is inspected, visually or by analytic
methods, to check for
any obvious differences in the matrix indicative of incomplete coalescence. In
tests done on
actual pipes, almost 100% bonding was achieved. In some cases a program is
selected to
achieve 100% bonding or within 1-3% deviance from 100%. The area of build-up
may
achieve bonding of 50% - 100%. Porosity sizes may range 0.001 - 0.010 and 0-30
inclusion
per square inch.
[0037] After the build-up process is complete, excess build-up material may
be
removed to produce a smooth finish on deposited weld metal 68. The build-up
area may be
finished by a process that supports a smooth finish 10 plus, which is a micro
finish quantifier
based on voids per square inch. Referring to Figs. 4 and 5, if the build up
fails during or after
testing, the build up area 68 may be machined off, either partially (Fig. 5),
or entirely to the
base material. The process of correcting flaws may be carried out in stages.
For example,
after machining off a portion of the weld metal 68, the remaining machined
area 106 is
inspected for flaws, and if the area 106 passes inspection, further build up
may be carried
out. If the area 106 does not pass, another skin of the material may be
machined off, and the
process repeated until the desired thickness and quality of deposited weld
metal 68 is
achieved. In some cases, prior to any welding the pipe 10 to be repaired may
be machined
down at the site to be welded, and then built up back to an outer diameter
equal to or greater
than the original outer diameter of the pipe, so that the build up area is
flush with the
adjacent area of the pipe 10.
[0038] Table 1 below illustrates parameters and test data for a sample test
done on a
non-magnetic alloy pipe made of stainless steel with Ni 3% and Mg 5%.
Table 1: Parameters and test data for non-magnetic alloy pipe
Ni 3%
Mg 5%
OD - starting material 165mm 6.5"
ID - starting material 83mm 3.25"
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wall thickness 42mm 1.62"
coolant rate 15-18 I_/minute 4-4.5 gallons/minute
wire diameter 0.05mm 1/16"
wire speed 381 cm/minute 150 inch/minute
pipe rotation 60 revolutions / minute (30-40 in some cases)
amperage 200-225
temperature of material 93-260 C. 200-500 F
Build up thickness 35mm 1.5"
[0039] The methods disclosed here may be carried out on various pipes 10,
including
pipes used in the oil and gas industry, for example as part of a downhole tool
such as a
drilling tool or other oilfield tubular. Other applications include parts in
valves, such as to
repair non-magnetic stainless steel parts in ball or gate valves. Downhole
parts often become
worn over use, particularly those used with heavy oil or hydrocarbons carrying
corrosive
substances such as sand.
[0040] In one embodiment the welding is carried out on the internal wall 26
while
supplying coolant to the outer wall 16. In one such example the pipe 10 may be
positioned
within a coolant bath (not shown) with a temperature sensor, a circulation
device such as a
stirrer, and a cooling device connected to maintain a desired temperature in
the bath. In
another example coolant may be sprayed upon the external wall 16, for example
from a
nozzle manifold extending up to a full circumference around the pipe 10
adjacent the active
welding site.
[0041] In some cases a multi-layer build up may be produced. A single layer
of weld
metal may be deposited, by depositing weld metal in adjacent rings or a spiral
pattern. The
number of adjacent rings or the length of the spiral is selected to achieve
the desired axial
length of build up. After deposition, the pipe 10 is allowed to cool and may
be tested, shot
peened, and machined if necessary, before additional layers of weld metal are
deposited. In
some cases the deposited weld metal is machined down to a smooth surface, upon
which one
or more further layers of weld metal may be deposited. Each layer may be
applied in the
same or a similar fashion.
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[0042] In the claims, the word "comprising" is used in its inclusive sense
and does
not exclude other elements being present. The indefinite articles -a" and -an"
before a claim
feature do not exclude more than one of the feature being present. Each one of
the individual
features described here may be used in one or more embodiments and is not, by
virtue only
of being described here, to be construed as essential to all embodiments as
defined by the
claims.
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