JPS59188410A - Method for covering steel pipe with heat-shrinkable tape - Google Patents

Abstract

PURPOSE:To make it possible to obtain relatively readily a steel pipe that can exhibit a corrosion preventive effect positively, by winding spirally a heat- shrinkable tape around the outer surface of a heated steel pipe that is being rotated. CONSTITUTION:A steel pipe 2 is rotated at a definite position by under rolls 1, and while a truck 32 is self-propelled concurrently with the rotational speed of the steel pipe 2 from one end of the steel pipe 2 to the other end, the outer surface of the rotated steel pipe 2 is successively heated by a heater 3 enough to the heat shrinking temperature of a heat-shrinkable tape. The heat-shrinkable tape 6 is successively fed from a tape feeder 4 onto the heated steel pipe 2 that is being rotated with a certain tension given to the tape so that the heat-shrinkable tape 6 is wound spirally around the outer surface of the pipe 2 with the opposite peripheries of the tape 6 overlapped. Thus the outer surface of the steel pipe can be covered cohesively with the heat-shrinkable tape 6 without enclosing air between them and therefore the steel pipe can be prevented effectively from being attacked by corrosion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for covering the outer surface of a steel pipe with a tape, and in particular, by using a heat-shrinkable tape as the tape and utilizing its heat-shrinkability, the heat-shrinkable tape can be coated with a tape. A method of covering a steel pipe with a heat-shrinkable tape, which prevents air from being entrained in the steel pipe and allows the heat-shrinkable tape to be easily wrapped around the steel pipe without taking up space. It is about the method.

Conventionally, various methods have been used to coat steel pipes with synthetic resins for corrosion protection, but these methods tend to entrap air, making it impossible to obtain sufficient corrosion protection, take up space, and require large equipment. There were various problems such as whether it was necessary or not.

In view of the above-mentioned points, the present invention has been made with the aim of relatively simply providing a steel pipe that can reliably exhibit a corrosion-preventing effect. The above object is achieved by wrapping the heat-shrinkable tape around the outer surface of the steel pipe using a specific method.

That is, the present invention rotates a steel pipe at a fixed position, sequentially heats the outer surface of the rotating steel pipe from one end to the other end, and heats the heated outer surface of the rotating steel pipe. A heat-shrinkable tape is supplied onto the steel pipe under constant tension from one end to the other end, and the heat-shrinkable tape is wound in a spiral shape onto the outer surface of the steel pipe. A method of covering a steel pipe with a shrinkable tape is provided.

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the method for coating a steel pipe with a heat-shrinkable tape of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic plan view of the apparatus used for carrying out the method of the present invention. 4 under rolls to be rotated, 11 is a drive unit that drives the under roll 1, 3.4 is a steel pipe 2, respectively.
The above-mentioned steel pipe 2
A heating device and a tape feeding device are provided on a cart 32 that moves by itself electrically in synchronization with the rotational speed of the tape feeder. Incidentally, reference numeral 37 is an auxiliary rail that assists the running of the heating device 3 when the trolley 32 is running.

Thus, when the method of the present invention is used, the steel pipe 2 is rotated in a fixed position by the under roll 1, and the steel pipe 2 is rotated from one end (right end) to the other end (left end). While the trolley 32 is self-propelled in synchronization with the rotational speed of the steel pipe 2, the outer surface of the rotating steel pipe 2 is heated by the heating device 3 until it reaches at least the heat shrinkage temperature of the heat shrinkable tape. At the same time, a heat-shrinkable tape 6 (see FIGS. 2 and 3) is sequentially supplied onto the outer surface of the heated and rotating steel pipe 2 while applying a constant tension from the tape supply device 4, EXAMPLE One embodiment of the method of the present invention will be described in further detail by winding the heat-shrinkable tape 6 on the outer surface of the steel pipe 2 in an overlapping manner in a spiral manner, together with details of the above-mentioned apparatus used for carrying out the method. First, the heat-shrinkable tape 6 used in the method of the present invention may be, for example, a heat-shrinkable crosslinked polyethylene tape having an adhesive layer on one side. The heat-shrinkable tape 6 preferably has a degree of crosslinking in terms of gel fraction of 10 to 90%, particularly 20 to 80%, and a shrinkage rate of 10 to 80%, particularly 20 to 70%.

Further, it is preferable that the steel pipe 2 to be wrapped with the heat-shrinkable tape 6 is surface-treated in advance using a shot blasting machine or the like. place As the steel pipe 2, a relatively large one of 4 to 60 inches is suitable for carrying out the method of the present invention.

Further, in order to rotate the steel pipe 2 placed on the under roll 1 in a fixed position, the under roll 1 is rotationally driven by the drive unit 11. During this rotational drive, the rotation of the steel pipe 2 can be adjusted within a range of 1:10, for example, so that the heat-shrinkable tape 6 can be wrapped in different wrapping modes (overlamp, etc.) around steel pipes 2 of different sizes. It is preferable to keep it at 5-. Further, the rotational drive of the underroll 1 by the drive unit 1 may be performed on at least one of the four underrolls 1, but if only one underroll 1 is rotationally driven, the steel pipe 2 is rotated when the tape is supplied.
Since slips are likely to occur between the under roll 1 and the under roll 1,
For example, it is preferable to drive the two under rolls 1 on the right end side of the steel pipe 2 to rotate. In this case, the two under rolls 1 on the left end side of the steel pipe 2 are left rotatable.

Note that it is preferable that the under roll 1 be coated with a rubber coating such as silicone rubber that has high heat resistance and a desired hardness that is effective as an anti-slip agent.

・Also, when heating the steel pipe 2 by moving the heating bag W3 while the steel pipe 2 is rotating, the heat shrinkage of the heat-shrinkable tape 6 is kept constant to prevent irregularities in the tape pitch, wrinkles in the tape, and when winding the tape. In order to prevent air entrapment, poor tape adhesion, etc., it is preferable to heat the steel pipe 2 evenly and accurately over its entire length. for that purpose,
When the heat generation amount per unit time due to the heating bag W3 is set to be constant, the moving speed of the heating device 3, in other words, the moving speed of the trolley 32 is made adjustable by synchronizing it with the rotational speed of the steel pipe 2. As shown by D in the time chart of the figure, the heating device 3, in other words, the trolley 32
is made to move slowly at both ends of the steel pipe 2.

This is because a large amount of heat is radiated at both ends of the steel pipe 2, and the temperature at these ends will not reach a sufficient temperature unless time is taken. When heating the steel pipe 2 with the heating device 3, the outer surface of the steel pipe 2 is heated to a temperature sufficient to heat-shrink the heat-shrinkable tape 6 used, preferably 100 to 250°C, more preferably 120 to 200°C. However, the heating device 3 is designed to be compatible with heat-shrinkable tapes 6 having different heat-shrinking temperatures.
It is preferable to use one that can adjust and heat the outer surface of the steel pipe 2 to a desired temperature as appropriate.

As shown in FIG. 2, the heating device 3 includes a hood 33 fixed to the trolley 32 so as to surround at least approximately 1 semicircle of the steel pipe 2, and It is preferable to use a furnace equipped with a combustion furnace section 34 for heating the semi-circumferential portion of the road surface of the steel pipe 2 from the outside on the inside of the rear end in the direction, and more preferably, a plurality of combustion furnace sections constituting the combustion section 34 are used. A burner 35 such as a gas burner is arranged at an angle of, for example, about 15 degrees in the direction of movement of the hood part 33 with respect to the vertical direction, and a heat retaining part 36 surrounds the lower semicircumferential part of the steel pipe 2 as shown by the imaginary line. Use one with a If the heating device 3 having such a structure is used, the burner 3
5 can be injected and guided in the direction of movement of the heating device 3, which not only heats the vicinity of the combustion furnace section 34 but also efficiently preheats the outer surface of the steel pipe 2 in the direction of movement of the heating device 3. At the same time, the tape supply device 4 is located at the rear of the heating device 3 in the direction of travel.
It is possible to avoid the risk of causing flames to spread to the heat-shrinkable tape 6 supplied onto the outer surface of the steel pipe 2. Note that if a burner is provided in the heat retention section 36, the burner 35 in the combustion furnace section 34 will be lacking in oxygen, so combustion efficiency can be increased by not providing a burner in the heat retention section 36. .

Next, the heat-shrinkable tape 6 is applied by the tape supply device 4 as the trolley 32 moves following the heating device 3.
When supplying, the starting end of the heat-shrinkable tape 6 is appropriately fixed on the outer surface of the steel pipe 2, and then the heat-shrinkable tape 6 is supplied onto the outer surface of the steel pipe 2 under constant tension. This is because the steel pipe 2 is heated by the heating device 3 as described above, so the heat shrinkage begins immediately after the heat-shrinkable tape 6 comes into contact with the steel pipe 2, and the heat-shrinkable tape 6 is heated by the heating device 3 as described above. The heat shrinkable tape 6 is applied with a resistance force, that is, tension, such that the heat shrinkable tape 6 can be tightly attached to the outer surface of the steel pipe 2 while keeping it in tension when the heat shrinkable tape 6 is applied to the outer surface of the steel pipe 2 before it comes into contact with the steel pipe 2. It is necessary to apply tension to 6 in the opposite direction to the winding direction, but if this tension is not constant, wrinkles will occur and air will be trapped.
This is because the purpose of preventing corrosion of the steel pipe 2 cannot be achieved.

FIG. 3 shows a schematic diagram of the internal mechanism of a tape supply device 4 suitably used for carrying out the method of the present invention. As shown in the figure, the tape supply device 4 wraps a heat-shrinkable tape 6. In order to almost eliminate tension changes due to radius changes from the loaded tape roll 41 or 9, the heat-shrinkable tape 6 is pulled out in a free state, and the drawn-out heat-shrinkable tape 6 is passed through a plurality of tape feeding adjustment rolls 4.
2 is sequentially wound, and the heat-shrinkable tape 6 is bent to provide contact resistance to the adjusting roll 42 to provide a braking effect to the heat-shrinkable tape 6, thereby making the final adjusting roll 42 heat-shrinkable. At the position where the tape 6 passes, the change in the tension of the heat-shrinkable tape 6 due to the change in the radius of the tape roll 41 is made as small as possible, and the heat-shrinkable tape 6 is further passed through a guide roll 43 and runs in contact with a brake-equipped roll 44 at a large winding angle.
Due to the braking action of the brake roll 44, which is effectively performed in conjunction with the above-mentioned braking effect, the tension of the heat-shrinkable tape 6 wound around the steel pipe 2 is adjusted, and the heat-shrinkable tape 6 is held at a constant tension. None so that it can be supplied to the steel pipe 2.

To explain the tape supply device 4 in more detail, the smaller the diameter of the tape feed adjustment roll 42 is, the higher the braking effect is, and the effect on the tape roll 4110- side is transmitted to the tape winding side. can be prevented. Further, 45 is a heat-shrinkable tape 6 that fits the running heat-shrinkable tape 6 between the tape feed adjustment roll 42, the guide roll 43, the brake-equipped roll 44, and the guide roll 46, and regulates it from both sides. This is a tape meandering prevention unit with a double cross structure that prevents tape from meandering in the width direction. Meandering prevention by the tape meandering prevention unit 45 is most effectively performed at the portion of the tape feeding adjustment roll 420 where the tape tension is the weakest. The purpose of preventing meandering in this way is that if the heat-shrinkable tape 6 is supplied to the steel pipe 2 while being deviated in the middle direction, the winding pitch of the heat-shrinkable tape 60 may be irregular and the heat-shrinkable tape 6 may be
This is because the skin has a habit of causing wrinkles.

Further, the roll with brake 44 has a silicone rubber sheet with high frictional resistance applied to the surface of a neoprene roll, and a brake drum 44a is fixed to the side of the roll.
The brake drum 44a is configured to be tightened by a belt heald 44b. The belt belt 44b is tightened by an air cylinder 44c. By adjusting the air pressure of the air cylinder 44C with a regulator, the tightening force of the belt belt 44b is adjusted, and the heat shrinkable tape 6 is tightened. For example, the tension is 0.1
None so that it can be adjusted within the range of ~1.5 kg/cm.

Further, 47 is a tape approach angle adjustment roll arranged so that the vertical position setting can be changed, which makes it possible to adjust the supply direction of the heat-shrinkable tape 6 even for steel pipes 2 of different sizes, and to adjust the heat shrinkage to the steel pipe 2. The approach angle of the shrinkable tape 6 can be varied according to the rotational speed of the steel pipe 2. When it is necessary to increase the rotational speed of the steel pipe 2, the tape approach angle adjusting roll 47 is normally positioned at a lower position to deepen the approach angle of the heat-shrinkable tape 6 into the steel pipe 2. By deepening the approach angle of the heat-shrinkable tape 6 to the steel pipe 2 in this way, the distance between the position of the touch roll 50 described later and the contact start position of the heat-shrinkable tape 6 to the steel pipe 2 is increased. The heated steel pipe 2 heats the heat-shrinkable tape 6 sufficiently until it reaches the position of the touch roll 50, and the heat-shrinkable tape 6 becomes faster as the rotational speed of the steel pipe 2 increases. It is possible to supplement the preheating by heating line burners 48 and 49, which will be described later, which tends to be insufficient.
8 preheats the adhesive layer of the heat-shrinkable tape 6 to a flow temperature at which it can sufficiently exhibit its adhesive effect before wrapping it around the steel pipe 2. This is a heating line burner that prevents adhesion failure in the overlamp area. Also 49
The tape layer of the heat-shrinkable tape 6 is preheated before winding the heat-shrinkable tape 6 around the steel pipe 2, and the winding of the heat-shrinkable tape 6 around the steel pipe 2 is started by over-ramping the heat-shrinkable tape 6. This is a heating line burner that can be easily deformed to correspond to the stepped portion at the end of the section. The two burners 48 and 49 make it possible to easily and reliably degas the stepped portion in particular.

Further, 50 presses the heat-shrinkable tape 13-pro supplied to the steel pipe 2, and in combination with the above-mentioned burners 48 and 49, deaerates the inside of the heat-shrinkable tape 6 and It is a taft roll that provides uniform contact adhesion to the tape 6. The touch roll 50 is preferably disposed at a position where the heat-shrinkable tape 6 contacts the steel pipe 2. Further, as shown in FIGS. 2 and 3, the pressing force of the Tafti roll 50 can be adjusted by an air cylinder 51, and as shown in FIG. It is mounted so that it can swing in a vertical plane. Ideally, the pressing by the touch roll 50 should be applied to the portion of the heat-shrinkable tape 6 supplied to the steel pipe 2 excluding the overlapped portion, that is, the same plane portion, as shown on the right side of FIG. However, if the overlap part moves from side to side by about 5 to 10 mm, the stepped part at the end of the overlap part must be completely degassed, so the touch roll 50 is heated as shown on the left side of Fig. 4. The entire width of the heat-shrinkable tape 6 is pressed to achieve a degassing effect and a contact adhesion effect as described above over the entire inside of the heat-shrinkable tape 6, and to completely degas the stepped portion. Preferably, an auxiliary touch roll 52 is provided and this is carried out. The touch roll 50 is preferably made of silicone rubber having a desired hardness and is relatively hard, and the auxiliary touch roll 52 is preferably made of silicone rubber having a relatively soft desired hardness.

As described above, while the steel pipe 2 is rotating, the heating device 3 and the tape supply device 4 are moved from one end of the steel pipe 2 to the other end.
Once the heat-shrinkable tape 6 is spirally wound around the outer surface of the steel pipe 2, the heat-shrinkable tape 6 from the tape supply device 4 is cut, and then the heat-shrinkable tape 6 is wrapped around the outer surface of the steel pipe 2. Cant back (remove) 6 by a predetermined dimension
Then, the steel pipe 2 is further cooled. In this case, cooling may precede cutback, but it is preferable to precede quadrup.

The cut bank is a rotary cutter (not shown) placed inside the under roll 1 that supports both ends of the steel pipe 20.
is brought into contact with the steel pipe 2 while the steel pipe 20 rotates to cut the heat-shrinkable tape 6 in the circumferential direction of the steel pipe 2,
This can be carried out by peeling off the cut heat-shrinkable tape 6 from both ends of the steel pipe 2, and then scraping off the adhesive from the steel pipe 2. In this case, if the cutback is performed prior to cooling, the cutting with the rotary cutter can be performed at a high temperature, so the cutting can be done without any effort, and damage to the steel pipe 2 can be prevented. can do.

Further, it is preferable to cool the steel pipe 2 after moving the steel pipe 2 to a cooling rack using a crane or the like. During cooling, while rotating the steel pipe 2 in a fixed position, water is preferably sprayed into the interior of the steel pipe 2 from both ends thereof to cool the steel pipe 2 to the outside temperature. In this case, cooling is not done rapidly;
And make sure to do it evenly. Another cooling method is to spray water from the outside of the steel pipe 2. When watering, air jetting may be used in combination to form a skin layer on the surface of the steel pipe 20.

Therefore, in the case of cooling the steel pipe 2 by spraying water from outside, it is preferable to wait until the temperature of the outer surface of the heat-shrinkable tape 6 has decreased. Otherwise, uneven shrinkage of the heat-shrinkable tape 6 may cause heat shrinkage. Pockmarks are likely to occur on the surface of the adhesive tape 6, resulting in poor appearance.

In addition, when cooling the steel pipe 2 by spraying water from outside, the heat-shrinkable tape 6 functions as a heat insulating material, so the cooling efficiency of the steel pipe 2 becomes poor, and the cooling time is 4 to 5 times longer than when cooling the steel pipe 2 internally by spraying water as described above. It takes. Furthermore, internal cooling by water spraying and external cooling by water spraying may be used together.

FIG. 5 shows a time chart of one embodiment of the method of the present invention described above, and the horizontal axis shows the time axis corresponding to the position of the steel pipe 2. In the same figure,
A indicates the burner combustion time of the heating device 3, which starts heating before the heating device 3 reaches one end of the steel pipe 2, and starts heating when the flame is released from the other end of the steel pipe 2. This indicates that heating by the device 3 is finished.

Further, B indicates the lighting time of the red lamp during work, and C indicates the pressing time of the heat-shrinkable tape '6 by the touch roll 50. Furthermore, D shows the velocity diagram of the carriage 32, ie the heating device 3 and the tape supply device 4, and thus also the (rotational) velocity diagram of the steel tube 2 synchronized therewith. As described above, the cart 32 is moved slowly at both ends of the steel pipe 20. In this case, it is possible to automatically control the moving speed of the cart 32 and the rotational speed of the steel pipe 2 using a sequence controller, setting volume, frequency converter, etc. For example, it is possible to automatically control the moving speed of the cart 32 and the rotation speed of the steel pipe 2. When the moving cart 32 reaches a position where the speed of the cart is changed, it is detected by a limit switch, etc., and this position detection signal is sequentially input to the sequence controller, and the output signal is sent via the setting volume. This is done by inputting the frequency into a frequency converter, and sending a constant ratio of frequency from the frequency converter to the variable speed motor of the truck 32 and the variable speed motor (drive unit 11) of the steel pipe 2, which are configured to change at the same ratio. Can be done. Further, a cutback is performed at a portion d in the speed diagram.

In one embodiment of the method of the present invention described above, the heat-shrinkable tape 6 is wrapped when the cart 32 is moved in one direction, so to speak, when it is moving forward.
The heat-shrinkable tape 6 may also be wrapped during the return movement to improve work efficiency.

In order to wrap the heat-shrinkable tape 6 even during the backward motion, the heating device 3 and the tape supply device 4 are driven separately, with the heating device 3 always preceding the tape supply device 4. Further, the tape feeding device 4 is configured to be able to adjust the tape feeding angle during the backward movement, as shown by the two-dot chain line in FIG. What is necessary is to provide a combustion furnace section that performs the operation.

As described in Section 2, the method of coating a steel pipe with a heat-shrinkable tape of the present invention uses a heat-shrinkable tape, and applies the heat-shrinkable tape onto the outer surface of a heated steel pipe under constant tension. Since the heat-shrinkable tape is wrapped using its shrinkability, the heat-shrinkable tape can be tightly coated on the outer surface of the steel pipe without entrapping air, thereby effectively protecting the steel pipe from corrosion. In addition, since the steel pipe is heated and the heat-shrinkable tape is supplied without moving the steel pipe, the heat-shrinkable tape can be easily attached to the steel pipe without taking up space. It has excellent working efficiency, such as being able to be wrapped, and has outstanding effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of the apparatus used in the method of the present invention, FIG. 2 is a perspective view of the main parts of the heating device and tape supply device in the apparatus, and FIG. 3 is the internal mechanism of the tape supply device. FIG. 4 is a perspective view illustrating the arrangement of the touch roll in the tape supply device, and FIG. 5 is a time chart in a preferred embodiment of the method of the present invention. 2... Steel pipe 3... Heating device 4... Tape supply device 6... Heat shrinkable tape 34... Combustion furnace section

Claims (2)

[Claims] (1) Rotate a steel pipe in a fixed position, heat the outer surface of the rotating steel pipe sequentially from one end to the other end, and heat shrink the heated outer surface of the rotating steel pipe. The heat-shrinkable tape is sequentially supplied under constant tension from one end of the steel pipe to the other end, and the heat-shrinkable tape is wound spirally onto the outer surface of the steel pipe. Method of coating steel pipes. (2) The outer surface of the steel pipe is heated by sequentially moving a heating device from one end of the steel pipe to the other end, and the heat-shrinkable tape is supplied onto the outer surface of the steel pipe with the heating device. The heat-shrinkable tape according to claim 11 is characterized in that the rotation speed of the steel pipe is synchronized with the moving speed of the heating device and the tape feeding device by a tape feeding device that moves at the same time. method of coating steel pipes.