DE8011918U1 - Device for electropolishing pipes - Google Patents

Description

80 165 KN

it · ·

NUKEM GmbH 6450 Hanau 11

Device for electropolishing pipes

The invention "relates to an apparatus for electropolishing the inner walls of metallic pipes.

The process of electropolishing has been around for many years known, however, it has only matured for industrial use in the last few years. By electrolytic removal the metal surface, which is located as an anode in an electrolyte, becomes a very smooth, clean, quasi polished surface finish preserved. The electropolishing process is widely used in the production of metallic ground joint samples, where a high surface quality is required.

But it is also used industrially to manufacture high-quality semi-finished products. For example, fuel element cladding tubes, After they are loaded with fuel and welded, the outside is electropolished.

A corresponding quality is also required for the inner pipe surfaces. Try to get the inner surface of the Electrolytic polishing of pipes has so far produced unsatisfactory results. The uniformity of the surface quality was very difficult to maintain and reproducible, so that one had to pay for the remuneration of the inner pipe walls is still dependent on pickling and sandblasting steps.

These known steps for polishing the inner walls of pipes have major disadvantages both economically and ecologically. They require one high expenditure of manpower, a high consumption of pickling solution and thus a high expenditure for reconditioning or for conditioning the waste solutions. Furthermore, there is a great deal of dust nuisance when sandblasting. In spite of this, only a non-uniform, difficult-to-reproduce surface quality of the inner pipe walls is obtained.

It was therefore the object of the present invention to provide a device for electropolishing the inner wall of a pipe to find, with which a uniform polishing of the pipe inner walls can be achieved.

This object has been achieved according to the invention in that a pipe lance is introduced into the pipe, the area of which formed as a metallic cathode between the tip and a retaining ring and its shaft is electrically insulated is, the baffle rings or baffle rings in front of and behind the cathode area a uniform distance and a defined Ensure the flow of electrolyte fluid between the cathode area and the tube.

The pipe lance is preferably provided with bores for the electrolyte liquid to pass through. The electrolyte liquid is passed through the pipe lance, cools the cathode and is advantageously through the bores

behind the first retaining ring, between the pipe wall and the cathode
directed.

In the electrolyte | cell at the same time a tubular cathode to the outer wall | to accommodate treatment of the pipe. This allows the interior
and the outer surfaces of the tube in one operation
be remunerated.

Figures I to III show schematically an example | adhesive embodiment of the device according to the invention. Ij

The pipe (1) to be treated is transported by means of two conveyor rollers ||

(2) driven through an inlet nozzle (3) into the electrolysis cell (4) 1 with the electrolyte liquid. In a tubular cathode (5), for example, an outer wall treatment takes place.
The pipe (1) is pushed further over the pipe lance (6) for internal treatment and leaves later through the conical
Outlet nozzle (7) the electrolysis cell (4).

It is taken over by two further conveyor rollers (8).
With the help of a limit switch (9), the conveying direction
reversed and the pipe (1) now in the reverse direction
transported through the electrolysis cell (4) and thereby
treated again inside and outside. Contact Rolls (10)
and (11) maintain electrical connections at all times
with the positive pole of a voltage source.

The tube lance (6) serves as the inner cathode, the shaft (12) of which
is electrically isolated. Between the plastic loading | standing tip (13) of the pipe lance (6) and an artificial $

I III ■ I Il

material ring (14), the lance (6) is bare metal, so that the inner cathode (15) is thereby formed.

The electrolyte liquid is fed through the hollow pipe lance (6) pumped and exits through bores (16) which are mounted inside the plastic ring (14). Attached impact rings (17) conduct the electrolyte parallel to the pipe lance (6), so that a bubble-free electrolyte flow during the electropolishing (18) is ensured between the pipe lance (6) and pipe (1).

The insulating plastic tip (13) and the retaining ring (14) serve as damming elements and spacers. The direction of flow as well as the flow is designed so that When the cell is unloaded, hardly any electrolyte fluid escapes through the outlet nozzle (7) and thus the level in the cell (4) remains constant.

The inlet nozzle (3) on the opposite side has the same task. The electrolyte liquid becomes ring-shaped through arranged bores (19) slides over the conically tapering nozzle tip into the cell (4). Here too Only a small amount of electrolyte fluid flows out, even when it is unloaded, so that it is very advantageous to use expensive sealing devices between the moving pipe and the electrolysis cell can be completely dispensed with.

, ι ι

A correspondingly large AblauiVehr (20) provides a constant level in all operating conditions. The electrolyte cell (4) and the conveyor rollers (2, 8) are located in a tub (23) so that both the electrolyte liquid overflowing from the cell and the electrolyte liquid flowing out of the tube (1) can run into a collecting tank (21), from where a pump (22) circulates them to the cell (4).

A cooling coil (24) in the tank (21) holds the desired
Constant temperature in the electrolyte.

In the following examples, the surface treatment and the surface quality obtained with that according to the invention Device explained in more detail:

Example 1:

Electropolishing of the inner walls of pipes.

Material: Zircaloy, diameter outside 10.5 mm and inside 9.6 mm

Pipe length: 3500 mm
Electrolyte: 10% perchloric acid
7090 acetic acid
20% water

Feed or return feed: 3 m / min
Voltage (U ₁ ) 11 volts, current (J ₁ ) 35 amps
Electrolyte flow: inner cathode: 4.5 l / min

Inlet nozzle: 7.0 l / min
Temperature: 25 ⁰ C

Dimensions of the inner cathode: 0 6 mm, length 120 mm

Result:

Number of tubes examined: 10

Weight loss after electropolishing:

Average value: 2.121 g

Standard deviation: 0.158 g

The loss on the inner wall is calculated from the weight loss:

Average: 3.09 am

Standard deviation: 0.23 «m

Surface roughness: 0.06 «m (initial quality 0.4 do)

Example 2:

Electropolishing of the inner and outer walls of pipes Material: Zircaloy, diameter: outside 10.5 mm and inside 9.6 mm

Pipe length: 3500 mm
Electrolyte: 10% perchloric acid

70% acetic acid

20% water

Feed or return 3 m / min Conditions for interior walls:
Identical, example 1
Conditions for external walls:

Voltage (U2) 16 volts, current (I ₂ ) 44 amps

Current (I,) 79 Amp

Dimensions of the outer cathode: outer diameter 40 mm Inner diameter 20 mm, length 100 mm

Result:

Number of tubes examined: 10 Weight loss after electropolishing:

Average value: 3.829 g

Standard deviation: 0.302 g Surface roughness inside: 0.06 (before 0.4) outside: 0.06 (before 0.25)

Using the results from Example 1, the following can be calculated for the outer wall:

Weight loss: 3.829-2.121 = 1.708g

Average removal: 2.2.7 fm

Standard deviation: 0.40 Lm (for interior and

External removal).

04/23/80
Kl / Han

Claims (4)

ρ * r GmbHNUKE M116450Hanau 80 165 KN a-erftnsprüche 1. A device for electropolishing the inner walls of a pipe, characterized in that a pipe lance (6) is introduced into the pipe (1), the area (15) of which is formed as a metallic cathode between the tip (13) and a retaining ring (14) the shaft (12) of which is electrically insulated, with the baffle rings (14) or baffle rings (17) in front of and behind the cathode area (15) a uniform distance and a defined flow of the electrolyte liquid (18) between the cathode area (15) and tube (1 ) to ensure. 2. Apparatus according to claim 1, characterized in that the pipe lance (6) is provided with bores (16) for the passage of the electrolyte liquid. 3. Apparatus according to claim 1 and 2, characterized in that a tubular cathode (5) for the outer wall treatment of the tube (1) is housed in the electrolytic cell (4) at the same time. 4. Apparatus according to claim 1 to 3, characterized in that the level of the electrolyte liquid is kept the same in all operating states via a discharge weir (20) with a sufficiently large cross-section and through the lateral feed via the inlet nozzles (3) and (7).