DESCRIPTlON
TITLE OF INVENTION
ELECTROI'LATING APPARATUS FOR STEEL PIPES
TECHNICAL FlELD
[OOO I]
'The present invention relates to an electroplating apparatus for steel pipes.
More particularly, the present invention relates to an electroplating apparatus for steel
pipes configured to apply an electroplated coating to a female thread formed on a pipe
end portion of a steel pipe as a threaded joint element.
BACKGROUND ART
[0002]
In oil wells, natural gas wells, and the like (hereinafter also collectively referred
to as "oil wells"), oil country tubular goods are used for extraction of underground
resources (e.g., petroleum, natural gas, etc.). Oil country tubular goods, which are
steel pipes, are configured to be sequentially connected to each other, and threaded
joints are used for the connection.
[00031
Such threaded joints are generally classified into two types, a coupling-type joint
and an integral-type joint. A coupling-type threaded joint is constituted by a pair of
tubular goods that are to be connected to each other, of which one is a steel pipe having
a longer length and the other is a coupling having a shorter length. In this case, the
steel pipe is provided with a male thread formed on the outer periphery at each end
portion thereof, and the coupling is provided with a female thread formed on the inner
periphery at each end portion thereof. The male thread of the steel pipe is screwed into
the female thread of the coupling, thereby making up a joint between them. An
integral-type threaded joint is constituted by a pair of steel pipes as tubular goods that
are to be connected to each other, without a separate coupling being used. In this case,
each steel pipe is provided with a male thread formed on the outer periphery at one of
its opposite end portions and a female thread formed on the inner periphery at the other
thereof. The male thread of one of the steel pipes is screwed into the female thread of
the other of the steel pipes, thereby making up a joint between them.
[0004]
In recent years, from the standpoint of improving the manufacturability of oil
country tubular goods, there is an increasing need for using a threaded joint of the
integral type. This is because no separate coupling is required.
[0005]
When making up steel pipes, lubricating grease (dope) is applied to the male
thread and the female thread. The purpose of this is to prevent galling in the threads
and also to enhance the sealing performance of the threaded joint. Conventionally, as
the lubricating grease, lubricants specified by API (American Petroleum Institute)
standards (hereinafter also referred to as "API dope") are widely used. API dope
contains heavy metals such as Pb (lead) and exhibits high lubricity.
[0006]
In recent years, environmental regulations have become more stringent. Thus,
the use of API dope has been restricted, and a need has arisen for use of lubricating
grease free of heavy metals (hereinafter also referred to as "green dope"). However,
green dope has lower lubricity than API dope. Because of this, in the case of using
green dope, it is necessary to apply an electroplated coating such as a copper coating to
the surface of at least one of the male thread and the female thread. The purpose of
this is to prevent galling in the threads by compensating for the insufficient lubricity.
[0007]
When applying an electroplated coating to a coupling-type threaded joint, the
coating is applied to the female thread of the coupling. Threaded joints having an
electroplated coating on the female thread of the coupling exhibit high reliability.
Because of the high reliability, when applying an electroplated coating to an
integral-type threaded joint, too, it is increasingly desired that the coating be applied to
its female thread on the pipe end portion of the steel pipe.
[OOOS]
Japanese Patent Publication No. S63-6637 (Patent Literature 1) discloses an
apparatus for applying an electroplated coating to a male threaded region formed on one
of the pipe end portions of a steel pipe, i.e., to the outer peripheral surface at a pipe end
portion of a steel pipe.
ClTATION LIST
PATENT LITERATURE
[0009]
Patent Literature 1: Japanese Patent Publication No. S63-6637
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[OO 1 01
During an electroplating process, typically, bubbles of hydrogen, oxygen, or the
like are generated while a plated layer is formed. When an electroplated coating is
applied to a male thread formed on the outer periphery of a pipe end portion, as
disclosed in Patent Literature 1, gas bubbles quickly depart from the surface of the male
thread and float. Thus, gas bubbles do not cause a problem. However, when an
electroplated coating is applied to a female thread formed on the inner periphery of a
pipe end portion, gas bubbles are retained, in particular on an upper portion of the inner
periphery of the pipe end portion. The regions where the gas bubbles are retained
become unintentional bare spots.
[OOl 11
Further, once the electroplating process is completed, the plating solution needs
to be promptly removed from the pipe end portion. The reason for this is that
corrosion caused by the plating solution develops and results in tarnishing of the surface
of the plated layer. In this regard, with the electroplating apparatus disclosed in Patent
Literature I , discharging the spent plating solution from the cell is time-consuming
because the cell which houses the pipe end portion and the plating solution is a
completely closed system. As a result, assuming that a large diameter steel pipe is the
object to be treated, if an electroplated coating is applied to a female thread on a pipe
end thereof, tarnishing will occur in the plated layer formed on the female thread.
[OO 1 21
Typically, after the spent plating solution is discharged, water is introduced into
the cell in place of the plating solution to rinse the pipe end portion with water. If the
amount of waste water from the water rinsing is increased, the cost of waste water
treatment is increased. Thus, reduction of the amount of waste water is desired.
[00 1 31
An object of the present invention is to provide an electroplating apparatus for
steel pipes having the following characteristics:
- Preventing the retention of gas bubbles formed during an electroplating process
regardless of the size of the steel pipe;
- Promptly removing the spent plating solution after the electroplating process;
and
- Reducing the anlount of waste water.
SOLUTION TO PROBLEM
[00 141
An electroplating apparatus for a steel pipe according to an embodiment of the
present invention is configured to apply an electroplated coating to a female thread
formed on a pipe end portion of the steel pipe.
The electroplating apparatus includes: an inner seal member; a capsule; a
discharge outlet; an opening; a cylindrical insoluble anode; and a plating solution supply
mechanism.
The inner seal member is disposed in an interior of the steel pipe and divides the
interior of the steel pipe at a location longitudinally inward of a region on which the
female thread is formed.
The capsule is sealingly attached to the pipe end portion.
The discharge outlet is formed in the capsule to discharge a plating solution
inside the capsule therefrom.
The opening is formed in the capsule to facilitate the discharge of the plating
solution inside the capsule.
The insoluble anode is disposed in an inside of the pipe end portion while passing
through the capsule in a sealed relationship to the capsule.
The plating solution supply mechanism supplies the plating solution to the inside
of the pipe end portion sealed by the inner seal member and the capsule.
The plating solution supply mechanism includes a plating solution supply tube
and a plurality of nozzles.
The plating solution supply tube extends along an axis of the insoluble anode and
projects from a leading end of the insoluble anode in the inside of the pipe end portion.
'I'he nozzles are attached to a leading end portion of the plating solution supply tube to
eject the plating solution between an outer peripheral surface of the insoluble anode and
an inner peripheral surface of the pipe end portion.
The i~lsolublea node has a configuration that does not allow ingress of the plating
solution ejected from the nozzles to the insoluble anode.
[OO 1 51
Preferably, in the above electroplating apparatus, the opening is located in an
upper portion of the capsule and is opened to the atmosphere when discharging the
plating solution after being spent.
[00 1 61
Preferably, in the above electroplating apparatus, the configuration of the
insoluble anode that does not allow ingress of the plating solution is such that a cover is
provided at the leading end of the insoluble anode and the plating solutioll supply tube
passes through the cover in a sealed relationship to the cover.
ADVANTAGEOUS EFFECTS OF INVENTION
[00 1 71
An electroplating apparatus for steel pipes of the present invention has the
following significant advantages:
- Ability to prevent the retention of gas bubbles formed during a plating process
regardless of the size of the steel pipe;
- Ability to promptly remove the spent plating solution after the plating process;
and
- Ability to reduce the amount of waste water.
BRIEF DESCRIPTION OF DRAWINGS
[00 1 81
[FIG.I] FIG.1 is a schematic longitudinal sectional view showing a configuration
of an electroplating apparatus for steel pipes according to an embodiment of the present
invention.
DESCRIPlION OF EMBODIMENTS
[00 1 91
In order to achieve the above ob-ject, the present inventors have conducted
intensive studies and consequently made the following findings (A) to (D).
[0020]
(A) If the ejection of a plating solution between a female thread and an anode is
in the form of a helical jet from a plurality of nozzles, gas bubbles that are formed
during a plating process will be blown quickly, and therefore bare spots due to retention
of gas bubbles will be prevented.
[002 1 ]
(B) In order to enable prompt discharge of the spent plating solution remaining
within the pipe end portion of the steel pipe after completion of the plating process, it
may be advantageous to provide a structure for facilitating discharge of the spent plating
solution. By means of this, tarnishing of the plated layer resulting from corrosion
caused by the plating solution will be prevented.
[0022]
(C) By specifying the locations of nozzles for ejecting the plating solution and the
ejection directions, stable formation of a plated layer will be possible regardless of the
size of the steel pipe. Specifically, when a small diameter pipe is the object to be
treated, the occurrence of bare spots and surface tarnishing will be prevented. When a
large diameter pipe is the object to be treated, the increase in the amount of waste water
will be prevented. As used herein, the term "small diameter pipe" refers to a pipe
having an outside diameter of 4 inches or less, the term "medium diameter pipe" refers
to a pipe having an outside diameter in the range of greater than 4 inches to 9 inches or
less, and the term "large diameter pipe" refers to a pipe having an outside diameter of
greater than 9 inches.
100231
(D) By specifying the form of the insoluble anode and the form of the plating
solution supply mechanism, it will be possible to reduce the amount of waste water
including the plating solution.
100241
The electroplating apparatus of the present invention has been made based on the
above findings. Hereinafter, embodiments of the electroplating apparatus of the
present invention will be described with reference to the drawings.
[0025]
FIG. 1 is a schematic longitudinal sectional view showing a configuration of an
electroplating apparatus for steel pipes according to an embodiment of the present
invention. As shown in FIG. 1, an electroplating apparatus 1 is an apparatus
configured to apply an electroplated coating to a female thread 20b of a steel pipe 20.
[0026]
The female thread 20b is formed on the inner periphery of one of the pipe end
portions 20a of the steel pipe 20. FIG. 1 shows an embodiment in which the steel pipe
20 is positioned generally horizontally. Alternatively, the steel pipe 20 may be
positioned in an inclined manner such that the end region at the electroplating apparatus
1 side is slightly lower than the opposite end region. Positioning the steel pipe 20 in
an inclined manner as described above has advantages in respect of preventing leakage
of the plating solution from the interior of the steel pipe 20 to the region opposite to the
electroplating apparatus I and reducing the retention of the plating solution in the pipe
end portion 20a when the plating solution is discharged. In the following description,
by way of example, the steel pipe 20 is a seamless oil country tubular good having a
long length configured to be connected with an integral-type threaded joint.
[0027]
The electroplating apparatus I includes an inner seal member 2, a capsule 3, an
insoluble anode 4, and a plating solution supply mechanism 5. In the following, these
structural elements are described one by one.
[0028]
[Inner Seal Member]
The inner seal member 2 is inserted into the interior of the steel pipe 20 and is
placed at a predetermined location 20c longitudinally (horizontal direction in FIG. 1)
inward of the region on which the female thread 20b is formed. The inner seal
member 2 is in contact with the entire circumference of the inner peripheral surface of
the steel pipe 20, and divides the interior of the steel pipe 20 at the predetermined
location 20c. In this manner, the inside of the pipe end portion 20a is sealed internally
by the inner seal member 2. The predetermined location 20c as referred to herein is
not particularly limited as long as it is longitudinally inward ofthe region on which the
female thread 20b of the steel pipe 20 is formed.
[0029]
The inner seal member 2 may be of any configuration as long as it can divide the
interior of the steel pipe 20 and internally seal the inside of the pipe end portion 20a
thereof. An example of the inner seal member 2 is a HEXA plug (from Mutsubishi
Rubber Co., Ltd.), which is for use in closing piping in piping work at industrial process
plants for petroleum, gases, chemicals, etc. A HEXA plug includes a rubber ring
having a C-shaped cross section and a pair of flat plates that firmly hold the rubber ring
therebetween. The rubber ring is expanded in diameter by being tightly held between
the pair of flat plates. 'This brings the rubber ring into contact with the entire
circumference of the inner peripheral surface of the pipe to thereby seal the interior of
the pipe integrally with the flat plates.
[0030]
[Capsule]
The capsule 3 has a cylindrical capsule body 3a having a closed end face. The
capsule body 3a is attached to the pipe end portion 20a of the steel pipe 20.
Specifically, the capsule body 3a is in intimate contact with the outer peripheral surfdce
of the pipe end portion 20a and is in intimate contact with the end face of the pipe end
portion 20a. In this manner, the capsule 3 externally seals the inside of the pipe end
portion 20a of the steel pipe 20 with the capsule body 3a being attached to the pipe end
portion 20a of the steel pipe 20 in intimate contact. In short, the inside of the pipe end
portion 20a is sealed by the inner seal member 2 and the capsule 3.
[003 I]
The capsule body 3a is provided with a discharge outlet 3c and an opening 3b.
The discharge outlet 3c is primarily designed to discharge the spent plating solution
after completion of the electroplating process. In addition, the discharge outlet 3c is
designed to continuously discharge and collect the plating solution inside the capsule
body 3a during the electroplating process and supply the collected plating solution to
the area inside the capsule body 3a from the plating solution supply mechanism 5.
Further, the discharge outlet 3c is designed to discharge waste water from water rinsing
that is performed after the discharge of the plating solution. The discharge outlet 3c is
located at a lower elevation than the inner peripheral surface of the pipe end portion 20a
of the steel pipe 20.
[0032]
A discharge tube 7 is connected to the discharge outlet 3c. 'The discharge tube 7
at an end thereof is open to a solution tank 9 for storing the plating solution. The
discharge tube 7 is provided with a valve 8 for selecting between passages for
discharging the plating solution (e.g., three-way valve). A waste water tube 12 is
connected to the discharge valve 8. 'The waste water tube 12 at an end thereof is open
to an external waste water tank (not shown).
[0033]
When performing a plating process, the passage leading to the solution tank 9 is
opened through the discharge valve 8. With this, the plating solution inside the
capsule body 3a can be continuously collected and recirculated. Likewise, when
discharging the spent plating solution after completion of the plating process, the
passage leading to the solution tank 9 is opened. With this, the plating solution inside
the capsule body 3a can be collected in the solution tank 9. When performing water
rinsing after discharge of the plating solution, the passage leading to the waste water
tube 12 is opened through the discharge valve 8. With this, waste water inside the
capsule body 3a can be discharged to the waste water tank.
COO341
The opening 3b is provided to facilitate the discharge of the spent plating solution.
The location of the opening 3b is not particularly limited as long as it can facilitate the
discharge of the plating solution. For example, as shown in FIG. 1, the opening 3b is
located in an upper portion of the capsule body 3a. The opening 3b is preferably
located at a higher elevation than the inner peripheral surface of the pipe end portion
20a of the steel pipe 20.
[0035]
The configuration may be such that a solenoid valve (not shown) is connected to
the opening 3b so that the opening 3b can be opened and closed by the solenoid valve.
When this configuration is employed, the solenoid valve is opened after completion of
the plating process so that the opening 3b is opened to the atmosphere. 'l'his allows
atmospheric pressure to act on the plating solution inside the capsule body 3a, thereby
facilitating the discharge of the plating solution from the discharge outlet 3c.
[003 61
Alternatively, the configuration may be such that a hose extending upwardly (not
shown) is connected to the opening 3b. In this case, during the plating process, the
pressure of the plating solution supplied to the area inside the capsule body 3a from the
plating solution supply mechanism 5 by a pump 10 described below and the weight of
the plating solution introduced into the hose are balanced so that the plating solution is
prevented from squirting out of the capsule body 3a.
1003 71
Furthermore, the configuration may be such that a compressor (not shown) is
connected to the hose. When this configuration is employed, compressed air is
delivered to the area inside the capsule body 3a from the opening 3b by the compressor
after completion of the plating process. Thus, high pressure acts on the plating
solution inside the capsule body 3a, thereby facilitating the discharge of the plating
solution from the discharge outlet 3c.
[003 81
As described above, the opening 3b provided in the capsule body 3a facilitates
the discharge of the plating solution from the discharge outlet 3c. Consequently, the
discharge of the spent plating solution is accomplished quickly, and therefore no
tarnishing occurs on the surface of the plated layer formed on the female thread 20b.
100391
[Insoluble anode]
An insoluble anode 4 (hereinafter also referred to siniply as "anode" 4) is a
cylindrical electrode (anode) for applying an electroplated coating to the female thread
20b. The insoluble anode 4 passes through the end face of the capsule body 3a and
extends to the inside of the pipe end portion 20a of the steel pipe 20. Thus, the anode
4 is positioned near the female thread 20b. The capsule body 3a and the anode 4
passing through the capsule body 3a are sealed by an O-ring or the like. The anode 4
is supported by the capsule body 3a.
[0040]
As the anode 4, a cylindrical body formed from a titanium plate coated with
iridium oxide, a stainless steel plate, or the like, is used.
[004 1 ]
An electrically conductive rod 6 is connected to the anode 4. Examples of the
electrically conductive rod 6 include a titanium rod, a stainless steel rod, and the like.
[0042]
A potential difference is applied between the anode 4 and the pipe end portion
20a of the steel pipe 20 surrounding the anode 4, across the plating solution. With this,
an electroplated coating is applied to the female thread 20b of the steel pipe 20.
[0043]
As described above, the anode 4 has a cylindrical shape and is hollow inside.
Thus, the anode 4 is light weight and easy to handle. Also, the material cost therefor
can be reduced. It is to be noted that the anode 4 has a configuration that does not
allow ingress thereto of the plating solution ejected from the nozzles 5b described below.
Because of this, the discharge of the plating solution after coinpletion of the plating
process is expedited. As a result, surface tarnishing of the plated layer formed on the
female thread 20b is further prevented.
[0044]
'The configuration that does not allow ingress of the plating solution to the anode
4 is not particularly limited, but, for example, the following configuration may be
employed. A cover 4a having a donut shape is provided at a leading end of the anode
4 disposed within the pipe end portion 20a. 'The cover 4a is joined to the anode 4 by
welding or the like and separates the inside of the anode 4 from the outside thereof. It
is noted that a plating solution supply tube 5a described below passes through the cover
4a. The cover 4a and the plating solution supply tube 5a passing through the cover 4a
are sealed by an O-ring or the like.
[0045]
[Plating Solution Supply Mechanism]
The plating solution supply mechanism 5 supplies a plating solution to the inside
of the pipe end portion 20a sealed by the inner seal member 2 and the capsule 3.
Specifically, the plating solution supply mechanism 5 includes a plating solution supply
tube 5a and a plurality of nozzles 5b. The plating solution supply tube 5a extends
along the axis of the anode 4, and projects from a leading end (the cover 4a in the
electroplating apparatus I shown in FIG. 1) of the anode 4 in the inside of the pipe end
portion 20a. 'The nozzles 5b are attached to a leading end portion of the plating
solution supply tube 5a projecting from the leading end of the anode 4. A trailing end
portion 5aa of the plating solution supply tube 5a passes through a side portion of a
trailing end portion 4b of the anode 4 projecting outwardly from the capsule body 3a,
and extends outwardly. The plating solution s~~pptluyb e 5a is supported by the
capsule body 3a via the anode 4.
[0046]
A main tube 11 from the solution tank 9 for storing the plating solution is
connected to the trailing end portion 5aa of the plating solution supply tube 5a. The
main tube 11 is provided with a pump 10 for pumping the plating solution to the plating
solution supply tube 5a. Further, the main tube 11 is provided with a valve 13,
between the pump 10 and the solution tank 9, for selecting between passages for
supplying the plating solution (e.g., three-way valve). A water tube 15 from a water
tank 14 for storing water for water rinsing is connected to the supply valve 13.
[0047]
When performing a plating process, the passage from the solution tank 9 to the
plating solution supply tube 5a is opened through the supply valve 13. Further, the
pump I0 is actuated. This allows the plating solution to be supplied to the area inside
the capsule body 3a through the plating solution supply tube 5a. When discharging the
spent plating solution after completion of the plating process, the operation of the pu~np
10 is stopped. Thus, the supply of the plating solution to the area inside the capsule
body 3a is stopped, and the plating solution inside the capsule body 3a is collected in
the solution tank 9. When performing water rinsing after discharge of the plating
solution, the passage from the water tank 14 to the plating solution supply tube 5a is
opened through the supply valve 13. Further, the pump 10 is actuated. This allows
water to be introduced into the area inside the capsule body 3a through the plating
solution supply tube 5a, so as to rinse the pipe end portion 20a of the steel pipe 20 with
water.
[0048]
The nozzles 5b are positioned inward of the leading end of the anode 4 in the
longitudinal direction of the steel pipe 20, and each nozzle tip 5ba is pointed toward the
outside of the pipe end portion 20a in the longitudinal direction. The plating solution
pumped to the plating solution supply tube 5a is ejected from the nozzles 5b in the form
of a helical jet between the outer peripheral surface of the anode 4 and the inner
peripheral surface of the pipe end portion 20a (the female thread 20b formed on the pipe
end portion 20a, to be exact). The number of the nozzles 5b is not particularly limited,
but it is preferably two or more, and more preferably three or more.
[0049]
With regard to the locations of the nozzles, one simple configuration is such that
the nozzles are disposed on the end surface of the capsule body 3a, i.e., the nozzles are
disposed outside the pipe end portion 20a in the longitudinal direction. However, this
configuration is not employed for the electroplating apparatus of the present
embodiment for the following reasons.
[0050]
The size of the steel pipe 20 ranges broadly, for example, from about 60 mm to
about 410 mm in outside diameter. When the steel pipe 20 is a small diameter pipe, a
small outside diameter cylindrical anode 4 is used. In this case, if the nozzles are
positioned outside the pipe end portion 20a, jets of the plating solution from the nozzles
are greatly affected by return flows of the plating solution from the inside of the pipe
end portion 20a toward the discharge outlet 3c located outside the pipe end portion 20a.
Because of this, sufficient jet streams from the nozzles cannot be obtained. As a result,
retention of gas bubbles may occur and bare spots may be caused.
[005 1 ]
On the other hand, when the steel pipe 20 is a large diameter pipe, even if the
nozzles are positioned outside the pipe end portion 20a, it is possible to obtain sufficient
jet streams of the plating solution as long as the power of the pump 10 is ensured, so
that retention of gas bubbles does not occur and no bare spots are caused. However, in
this case, if the nozzles are positioned outside the pipe end portion 20a, the discharge of
the plating solution becomes time-consuming when discharging the spent plating
solution after completion of the plating process, and this results in tarnishing of the
surface of the plated layer formed on the female thread 20b. Furthermore, when
performing water rinsing after discharge of the plating solution, the amount of waste
water from the water rinsing is increased if the nozzles are positioned outside the pipe
end portion 20a, and this results in increased costs of waste water treatment.
[0052]
Specifically, when the steel pipe 20 is a small diameter pipe of 2-718 inches
(73.03 mm) in outside diameter, if the nozzle tips are positioned outside the pipe end
portion 20a, it is impossible to obtain uniform and sufficient jet streams, and this results
in retention of gas bubbles and the occurrence of bare spots. In contrast, when the tips
5ba of the nozzles 5b are positioned inward of the leading end of the anode 4 in the
longitudinal direction of the steel pipe 20 as in the present embodiment described above,
neither bare spots nor surface tarnishing occurs. This is because uniform and sufficient
jet streams are formed between the female thread 20b and the anode 4, and therefore no
retention ofthe plating solution occurs. The outside diameter of the steel pipe 20
(2-718 inches (73.03 mm) as presented herein is a nominal outside diameter specified by
API standards, and the same notation is used below.
[0053]
Next, when the steel pipe 20 is a medium diameter pipe of 7-518 inches (1 93.68
mm) in outside diameter, bare spots or tarnishing rarely occurs even if the nozzle tips
are positioned outside the pipe end portion 20a. However, the amount of waste water
is increased, resulting in increased costs of waste water treatment.
[0054]
When the steel pipe 20 is a large diameter pipe of 13-318 inches (339.73 mm) in
outside diameter, it is possible to obtain sufficient jet streams even if the nozzle tips are
positioned outside the pipe end portion 20a, and therefore bare spots due to retention of
gas bubbles are not caused. However, discharge of the large volume of plating
solution is time-consuming, and therefore surface tarnishing is likely to occur. In
contrast, when the nozzles 5b are positioned inward of the leading end of the anode 4 in
the longitudinal direction of the steel pipe 20 as in the present embodiment described
above, the volume ofthe plating solution is actually reduced, and this results in rapid
discharge of the plating solution. Thus, surface tarnishing does not occur. Moreover,
the amount of waste water is reduced to about one-tenth, which results in a significant
reduction in costs of waste water treatment.
[0055]
For the above reasons, the electroplating apparatus 1 is configured such that the
nozzles 5b and their tips 5ba are positioned inward of the leading end of the anode 4 in
the longitudinal direction of the steel pipe 20, and each nozzle tip 5ba is pointed toward
the outside of the pipe end portion 20a in the longitudinal direction.
100561
The tips 5ba of the nozzles 5b are preferably positioned, in the radial direction of
the steel pipe 20, between the female thread 20b and the anode 4.
[0057]
The tips 5ba of the nozzles 5b shown in FIG. 1 have a straight shape pointed
toward the female thread 20b. Alternatively, in order to enhance the uniformity of the
jet streams that are formed between the female thread 20b and the anode 4, the tips 5ba
of the nozzles 5b may be inclined toward the outside of the steel pipe 20 in the radial
direction, for example, depending on the diameter of the steel pipe 20, the dimension of
the female thread 20b, or the like. Furthermore, when performing electroplating on
steel pipes 20 having different sizes, it is preferred that the direction in which the plating
solution is ejected from the nozzles 5b is appropriately modified for each of the steel
pipes 20 depending on its diameter, the dimension of its female thread 20b, or the like.
EXAMPLES
[005 81
To verify the advantages of the electroplating apparatus of the present
embodiment, the following test was conducted using the electroplating apparatus shown
in FIG. 1. As plating solutions, a degreasing solution (sodium hydroxide: 50 g/L), a Ni
strike bath (nickel chloride: 250 g/L, hydrochloric acid: 80 g/L), and a Cu electroplating
bath (copper sulfate: 250 g/L, sulfuric acid: 110 g/L) were prepared. Then, using the
baths in order, an electroplated coating (copper coating) was applied to a female thread
on a pipe end portion of a steel pipe. Process conditions for each step using each bath
were as shown in Table 1 below.
[005 91
[Table 11
TABLE 1
Step Cathodic Degreasing Ni strike Copper Coating
Bath
Current Treatment Current Treatment Current Treatment
Bath
Process Temp.("C) Density Time Density Time Density Time
Bath
Temp.("C)
Conditions (A/dm2) (Sec.) (A/dmz) (Sec.) Telnp.('C) (A/dm2) (Sec.)
5 0 6 60 3 5 G 120 5 0 8 400
[0060]
In the test, using steel pipes having different outside diameters, the nozzle
location was varied between positions inward of the leading end of the anode and
positions outside the pipe end portion. Also, the presence or absence of an opening in
the capsule body was varied. Evaluations were conducted as to bare spots, tarnishing
of the surface of the plated layer, and the amount of waste water from water rinsing that
is performed between steps. Table 2 below shows the test conditions and the results
obtained. The meanings of the reference symbols in the evaluation item sections (bare
spots and tarnishing of surface of plated layer) ofTable 2 are as follows.
[Bare Spots]
- 0 (Excellent): No bare spots were observed.
- x (Poor): Many bare spots were observed.
[Tarnishing of Surface of Plated Layer]
- 0 (Excellent): No tarnishing was observed.
- A (Fair): Minor tarnishing was observed.
- x (Poor): Tarnishing was observed.
[0061]
[Table 21
'TABLE 2
[0062]
The results in Table 2 demonstrate the following. As seen in Comparative
Examples 1 and 2, when a small diameter pipe was the object to be treated and the
nozzles were positioned outside the pipe end portion, uniform and sufficient jet streams
were not obtained, and therefore bare spots were caused because of retention of gas
bubbles. In addition, as seen in Comparative Example 2, even when the capsule body
had an opening, some tarnishing occurred on the surface of the plated layer.
[0063]
In contrast, as seen in Example 1, when a small diameter pipe was the object to
be treated and the nozzles were positioned inward of the leading end of the anode,
neither bare spots nor surface tarnishing was observed. This is due to the fact that
uniform and sufficient jet streams were formed between the female thread and the anode,
and therefore retention of the plating solution did not occur.
[0064]
As seen in Comparative Example 3, when a medium diameter pipe was the object
Classification
Comparative
Example 1
Comparative
Example 2
Comparative
Example 3
Comparative
Example 4
Example 1
Example 2
Example 3
Pipe Size
(ODIinch)
2-718
(snlall diameter
pipe)
2-718
(small diameter
pipe)
7-518
(medium
diameter pipe)
13-318
(large diameter
pipe)
2-718
(small diameter
pipe)
7-518
(medium
diameter pipe)
13-318
(large diameter
pipe)
Opening
Absent
Present
Present
Present
Present
Present
Present
Nozzle
Location
Outside
Outside
Outside
Outside
lnside
Inside
Inside
Bare Spots
x
x
0
0
0
0
-
0
Tarnishing
x
A
A
A
0
0
- -
0
Waste Water
Amount (L)
8.4
8.4
1 02.4
343.2
6.2
32.4
43.2
to be treated and the nozzles were positioned outside the pipe end portion, no bare spots
were caused. However, some surface tarnishing occurred and the amount of waste
water was significantly increased.
roo651
In contrast, as seen in Example 2, when a medium diameter pipe was the object to
be treated and the nozzles were positioned inward of the leading end of the anode, the
amount of waste water was reduced to about one-third that of Comparative Example 3.
[0066]
Also, as seen in Comparative Example 4, when a large diameter pipe was the
object to be treated and the nozzles were positioned outside the pipe end portion, bare
spots due to retention of gas bubbles did not occur because sufficient jet streams were
obtained. However, discharge of the large volume of plating solution required a long
time, and therefore some surface tarnishing occurred.
[0067]
In contrast, as seen in Example 3, when a large diameter pipe was the object to be
treated and the nozzles were positioned inward of the leading end of the anode, the
volume of the plating solution was actually reduced, and as a result, rapid discharge of
the plating solution was achieved, so that surface tarnishing did not occur. Moreover,
the aniount of waste water was reduced to about one-tenth that of Comparative Example
4.
INDUS'TRJAL APPLICABILITY
[0068]
The electroplating apparatus according to the present invention is useful in
applying an electroplated coating to a variety of steel pipes having a female thread,
including sean~lesso il country tubular goods configured to be connected using an
integral-type threaded joint.
REFERENCE SIGNS LIST
[0069]
1 : electroplating apparatus, 2: inner seal member,
3: capsule, 3a: capsule body, 3b: opening, 3c: discharge outlet,
4: insoluble anode, 4a: cover of insoluble anode,
4b: trailing end portion of insoluble anode, 5: plating solution supply
mechanism,
5a: plating solution supply tube, 5aa: trailing end portion of plating solution
supply tube,
5b: nozzle, 5ba: nozzle tip, 6: electrically conductive rod,
7: discharge tube, 8: discharge valve, 9: solution tank, 10: pump,
1 1 : main tube, 12: waste water tube, 13: supply valve,
14: water tank, 15: water tube,
20: steel pipe, 20a: pipe end portion, 20b: female thread,
20c: predetermined position

We claim:
1. An electroplating apparatus for a steel pipe, the electroplating apparatus is
configured to apply an electroplated coating to a female thread formed on a pipe end
portion of the steel pipe,
the electroplating apparatus comprising:
an inner seal member that is disposed in an interior of the steel pipe, the inner
seal member dividing the interior of the steel pipe at a location longitudinally inward of
a region on which the'female thread is formed;
a capsule that is sealingly attached to the pipe end portion, the capsule having a
discharge outlet through which a plating solution inside the capsule is discharged, the
capsule having an opening that facilitates discharge of the plating solution inside the
capsule;
an insoluble anode having a cylindrical shape, the insoluble anode being disposed
in an inside of the pipe end portion, the insoluble anode passing through the capsule in a
sealed relationship to the capsule; and
a plating solution supply mechanism that supplies the plating solution to the
inside of the pipe end sealed by the inner seal member and the capsule,
wherein the plating solution supply mechanism includes:
a plating solution supply tube that extends along an axis of the
insoluble anode, the plating solution supply tube projecting from a leading
end of the insoluble anode in the inside of the pipe end portion; and
a plurality of nozzles that are attached to a leading end portion of the
plating solution supply tube, the nozzles being configured to eject the
plating solution between an outer peripheral surface of the insoluble anode
and an inner peripheral surface of the pipe end portion, and
wherein the insoluble anode has a configuration that does not allow ingress of the
plating solution ejected from the nozzles to the insoluble anode.
2. The electroplating apparatus according to claim 1, wherein:
the opening is located in an upper portion of the capsule and is opened to the
atmosphere when discharging the plating solution after being spent.
3. The electroplating apparatus according to claim 1 or 2, wherein:
the configuration of the insoluble anode that does not allow ingress of the plating
solution is such that a cover is provided at the leading end of the insoluble anode and
the plating solution supply tube passes through the cover in a sealed relationship to the
cover.