GB2116284A

GB2116284A - Method of cleaning the inner surfaces of metal pipes of ring or coil form

Info

Publication number: GB2116284A
Application number: GB08305255A
Authority: GB
Inventors: Manfred Moik
Original assignee: KM Kabelmetal AG
Current assignee: KM Kabelmetal AG
Priority date: 1982-02-27
Filing date: 1983-02-25
Publication date: 1983-09-21
Also published as: ES518351A0; ES8402885A1; PL240767A1; IT1153562B; JPS58153788A; IT8223029A0; CA1219407A; NL191794C; ATA322182A; DE3207135C2; GB8305255D0; FI72755B; SE8301050D0; FI72755C; SE501882C2; DE3207135A1; FR2522286B1; JPH0420997B2; DD207554A5; FI824181A0

Abstract

In the cleaning of the inner surface of metal pipes of ring or coil form by means of a liquid cleansing agent, a predetermined quantity of the cleansing agent is first introduced at one end of the pipe, and then a plug, preferably of porous material, such as felt, which fills the pipe cross- sectional area is inserted into the end of the pipe and moved by pressure through the entire length of the pipe, whereby it moves the cleansing agent ahead of itself, and the pressure in the tube is thereafter caused or allowed to dissipate. In this way, the amount of grease present on the inner surface of the tube after treatment can be reduced to less than 0.1 mg grease/dm<2> surface area.

Description

SPECIFICATION Method of cleaning the inner surfaces of metal pipes of ring or coil form The present invention relates to a method of cleaning the inner surface of a metal pipe e.g. of ring or coil form using a liquid cleansing agent, preferably an organic solvent.

It is known that the corrosion of copper pipes used in the sanitary and similar fields is generally caused by carbon deposited on the inner surface of the pipe. This carbon film may be formed, for example, by the thermal decomposition of the drawing agent which is added during the process of drawing the pipe. With soft pipes which are soft annealed after the final drawing step, the decomposition products are formed as early as during the soft annealing. However, even in the case of hard pipes which are not subjected to annealing, a harmful carbon film can be formed if, for example, the pipes are connected to one another by hard soldering or are heated in order to facilitate bending. It has been found, however,that the carbon film which occurs during heating is virtually harmless if less than 0.1 mg/dm2 grease is present on the inner surface of the pipe.

In order to remove the grease film within the pipe, it has already been proposed to circulate a degreasing agent, such as, for example, perchlorethylene, or trichlorethylene, in the pipe ring or coil and then to dry the pipe by circulating warm air in order to evaporate the residual degreasing agent. This method ensures very efficient degreasing but is extremely costly since it is slow and interrupts the normal production sequence.

It has also been proposed to introduce steam to which a specific quantity of a degreasing agent has been added one or more times, into the pipe.

However, it has been found that, in this method of treatment, the grease film can only be reduced to the desired extent when the treatment is repeated several times. It goes without saying that such a method is uneconomical.

It is therefore an object of the present invention to provide a method of cleaning the inner surface of a metal pipe which allows the grease film to be reduced in an economical manner to an extent such that it is present as less than 0.1 mg grease per dm2 of pipe surface.

According to the invention, there is provided a method of cleaning the inner surface of a metal pipe e.g. of ring or coil form using a liquid cleansing agent, comprising the steps of first introducing a predetermined amount of the cleansing agent into the pipe at one end thereof, inserting a plug which fills the cross-sectional area of the pipe in said end of the pipe, moving said plug through the entire length of the pipe by exerting pressure thereon, whereby said plug drives the cleansing agent ahead of itself, and subsequently causing or allowing the pressure in the pipe to dissipate. The liquid cleansing agent is preferably an organic solvent, such as, for example, perchlorethylene, or trichlorethylene.

In the method of the invention, only a small amount of the solvent, for example 3 to 5 litres, is required in order to clean the pipe. It is essential that the speed at which the plug is carried through the pipe should be sufficiently high to allow the cleansing agent to contact the tube on all sides.

When the plug has passed out of the length of pipe, the connection to the pressure generator to the length of pipe is broken, and the excess pressure which has built-up slowly dissipates. In order to avoid health hazards when solvents such as, for example, perchlorethylene, or trichlorethylene, are used; it is advantageous to remove by suction the pressurising medium which emerges from the ends of the tube, which contains solvent vapours. The pressure medium may advantageously be nitrogen.

The efficient degreasing action may be explained by the fact that the cleansing agent is carried along the wall of the pipe at a high speed so as to give rise to turbulence effects which flush the grease even out of the smallest pits in the surface of the pipe. In addition, it is ensured that the film of cleansing agent which remains behind the plug considered in the direction of passage is very thin, so that after the evaporation of the cleansing agent the remaining film of grease (which had been dissolved in the film of cleansing agent) is so thin as to constitute less than 0.1 mg grease per dm2 of pipe surface. In order to obtain such an extremely thin film, it is advantageous in carrying out the invention, to use a plug made of porous material, preferably a felt plug, the diameter of which is slightly greater than the internal diameter of the pipe.When the plug contacts the cleansing agent it becomes saturated therewith and, because of its larger diameter, ensures that an intensive cleaning of the inner surface of the pipe takes place, with the production of the desired extremely thin film of cleansing agent. The ratio of length to diameter of the felt plug is preferably between 1.1 and 2.0.

The object of the invention, i.e. less than 0.1 mg of grease per dm2 of pipe surface, may be met by carrying out the process of the invention just once. If substantially lower grease values are required, however, the process can be repeated as necessary. If, immediately after the release of the cleansing agent and the plug from the pipe, this is followed by the application of a dry felt plug, grease values considerably below 0.1 mg grease per dm2 surface are achieved. The dry felt plug serves to remove the film of cleansing agent adhering to the walls of the pipe.

Another substantial advantage of the process of the invention is that the copper spangle which has been formed as a result of the drawing process is also removed from the interior of the pipe.

One embodiment of the invention will now be described in detail, by way of example.

Five litres of pure trichlorethylene are first introduced into a copper pipe having an outer diameter of 1 5 mm, a wall thickness of 1 mm, and an overall length of about 100 m and which is wound in the form of a coil. From the charging end, a felt plug having an outer diameter of 14 mm is pressed into the pipe and the end of the pipe is connected to a pressure producer, preferably a cylinder containing nitrogen under pressure. The pressure in the nitrogen cylinder is about 20 bar. As soon as the valve of the nitrogen cylinder is opened, the felt plug moves through the turns of the pipe at a speed of about 6 to 7 m per second. In so doing, it drives the amount of solvent ahead of itself, so that the latter washes around the entire inner surface of the pipe. When the solvent and the plug have emerged from the pipe coil, the connection of the nitrogen cylinder to the tube is broken. The nitrogen, which now contains solvent, emerges from the two ends of the pipe. When pressure equalisation has been established (which process lasts for about two minutes) the pipe is completely dry. This pipe is then subjected to a straightening operation and is cut to length.

Before treatment, the grease content on the inner surface of the pipe was 5 mg/dm2. After the treatment described, it was established that the grease content was 0.06 mg/dm2. This extremely low grease content was substantially uniform over the entire length of the pipe, apart from slight fluctuations.

In the example described, nitrogen was used as the pressurising medium. However, any other medium under pressure can be used, including compressed air, in which case it should be ensured that this is free from oil.

Claims

1. A method of cleaning the inner surface of a metal pipe e.g of ring or coil form using a liquid cleansing agent, comprising the steps of first introducing a predetermined amount of the cleansing agent into the pipe at one end thereof, inserting a plug which fills the cross-sectional area of the pipe in said end of the pipe, moving said plug through the entire length of the pipe by exerting pressure thereon, whereby said plug drives the cleansing agent ahead of itself, and subsequently causing or allowing the pressure in the pipe to dissipate.

2. A method as claimed in Claim 1, wherein said liquid cleansing agent is an organic solvent.

3. A method as claimed in Claim 2, wherein said solvent is perchlorethylene, or trichlorethylene.

4. A method as claimed in any one of Claims 1 to 3, wherein said plug is made of porous material, and has a diameter which is slightly greater than the internal diameter of the pipe.

5. A method as claimed in Claim 4, wherein said plug is made of felt.

6. A method as claimed in Claim 5, wherein said plug has a ratio of length to diameter of from 1.1 to 2.0.

7. A method as claimed in any one of the preceding Claims, wherein the passage of said plug through said pipe is repeated one or more times.

8. A method as claimed in any one of the preceding Claims, wherein, immediately after the or the last passage of said plug through the pipe, a dry plug of porous material is passed through the pipe.

9. A method as claimed in any one of the preceding Claims, wherein the pressure to move said plug through the pipe is provided by nitrogen under pressure.

10. A method of cleaning the inner surface of a metal pipe in ring or coil form as claimed in Claim 1, substantially as hereinbefore described with reference to the exemplary embodiment.

1 A metal pipe in ring or coil form, the inner surface of which has been cleaned by a method as claimed in any one of Claims 1 to 10.