Method of setting tip in lined pipe

FIELD: construction.

SUBSTANCE: method comprises setting the tip in the end section of the pipe lined by a plastic shell. A protector is fit in the tip with interference. The tip clamps the end of the plastic shell by mandrelling. The tip is fit in the pipe with interference. The tip is mandrelled out of the zone of protector.

EFFECT: enhanced reliability.

2 dwg

 

The invention relates to the field of engineering, namely, manufacturing of steel pipes with internal plastic shell, intended for the construction of pipelines transporting corrosive environment petrochemical and refining industries.

A known method of making lined pipe (see the book of Greenberg Z.A. and other "Steel pipe lined with polyethylene." M.: metallurgy, 1973), which consists in futerovannyh plastic shell steel pipe with end flanges, heating projecting from the pipe ends of a polyethylene shell and tortolani them on the ends of the flanges of the steel pipe. The disadvantages of this method are the need to manufacture and attach the flanges to the ends of the steel pipe, the impossibility of movement of steel pipes with flanges on the roller in the process stream at the serial manufacture of lined pipes and unreliability of flange connections with underground laying of pipelines.

There is also known a method of making lined pipe (see Instruction technology federowania polyethylene steel pipes. RD 39-0147585-335-86, TatNIPIneft, 1986), which includes accommodation in a steel pipe with a plastic shell, tips and protectors (PP, 4.4.4 [2]), planting tips and protectors and pinched all about the shell by means of burnishing tip (p [2]), when the hand (radial distortion) of the tip and subsequent jamming of the polyethylene sheath between the steel pipe and tip. When using the known method of connection of the tread from corrosive environment, which is necessary for the cathodic protection of steel tip and weld steel pipes through the holes in the tip (risb [2]). The electrical contact of the tread with a tip (also required for cathodic protection tip and weld) occurs after the radial distribution of the handpiece. If necessary, the connection of lined pipes between the pipelines this connection carry out electric arc welding.

The disadvantage of this method is the lack of reliability of the tread due to the short duration electrical contact between the steel the surface to be protected and protector. Theoretical and experimental research and experience in the joints plastic pipe (CMP) with cathodic protection interface shows the following:

The free installation of the protector on the tip and subsequent donovani after some time of operation of the pipeline is lost electrical contact between the protector and the protected steel surface. The reason is that, that in the assembled structure, due to the small contact pressure between the surfaces of the protector tip fluid under pressure passes between the surfaces of the protector tip, gradually oxidizing the surface of the tread. The oxidation products of the tread due to the high ohmic resistance prevent the passage of protective current from the tread to the steel surface. After the disappearance of the electrical contact between the protector and the tip starts to go the corrosion of steel tip and steel pipes when not yet fully trashtalkers protector.

There is also known a method of making lined pipe (see RF patent №2141070), class F 16 L 9/02, B. I. No. 31, 1999), characterized in that the pinching of the plastic shell and the landing tip is carried out by compression along the diameter of the pipe end on the length of the tip, landing tip with protector carry out preliminary pressing.

The disadvantage of this method of making lined pipe is that for the manufacture of MPT large diameter in the implementation process of compression steel pipe required for crushing the plastic shell, requires a fairly large size and weight of tools and equipment. For example, in the manufacture of MPT diameter 273 mm for compression steel pipe with thick stench the 9 mm will require portage, capable of withstanding heavy loads in compression, the diameter of 350-400 mm, snap to attach portages will have a diameter of about 500 mm, Given that the trail is replaceable and is constantly wearing tool, application of the method of compression on large diameter pipes is difficult (for pipes of small diameter 89-114 mm - change or restore the wear of the tool is not decisive in the implementation process).

In addition, as is well known [see the book Ponomareva S.D. "the strength Calculations in engineering], for any deformation of the material there is the phenomenon of elastic sediments of the material to its original, undeformed state. When the compression steel pipe that leads to the fact that after compression the inner surface of steel pipe "departs" from the outer surface of the protector is installed on the tip of the preliminary pressing. Thus, between the tread and the steel pipe after compression there is a slight gap, about 0.15-0.25 mm depending on the diameter, which adversely affects the operation of the tread in a constantly changing pressure and temperature of the fluid in the pipeline.

The technical result of the invention is the provision of reliability of the tread when the protection of steel Nakane is nick and weld lined steel pipes.

This technical result in the implementation of the invention is achieved by the fact that in the described method of installation of the tip in the tube, lined with a plastic shell, including the placement of the tip with protector, installed with an interference fit in the end portion of the pipe and the pinched end of the plastic sheath tip by the burnishing, according to the invention the placement of the tip in the tube in the range of location tread carried out with tension, and the burnishing tip carried out outside the location of the protector.

When mutual accommodation details with tightness (tip protector and tip steel pipe) created the contact pressure exceeds the pressure of the transported fluid, which prevents the passage of fluid along the border of the tip protector. So the placement of the tip with protector Assembly in a steel tube with an interference fit eliminates the difference in the deformation of the tip and protector, caused by variations of pressure and temperature fluctuations of the fluid in the pipeline, and thereby to maintain the necessary tension in the connection and, therefore, to ensure the preservation of a reliable electrical contact between the protector and the protected steel surface during operation of the pipeline.

The burnishing tip outside of the races whom the provisions of protector allows not to disturb the mutual fit of parts tip - protector - steel pipe after Assembly. The need for this due to the fact that according to the calculations of stress-strain state of the parts, posted with tension each other (the protector in the tip and the tip in the tube), after subsequent radial distribution between, in this case, the protector and the tip or tip and the steel pipe lost the contact pressure, which arose after fitting these parts. In other words, the deformation of the mating parts with the transition in their plastic state lost the preload and contact pressure, which is achieved by placing the parts fit into each other.

Figures 1 and 2 is a flow diagram of the proposed method of making lined pipe. Figure 1 - the process of placing with tightness (by pressing) tip with protector Assembly in a steel pipe (protector pre-planted with tightness in the tip); figure 2 - the end of the operation of crushing the plastic shell by means of burnishing tip outside the location of the protector.

The proposed method is implemented as follows:

First into the steel pipe 1 remove the plastic end of the shell 2 to a depth corresponding to the estimated installation tip with protector. Then the tread 3 of the tread, and manual the aqueous alloy (for example, aluminum alloy 1915) pre presoviet in steel tip 4 ("press" fit H8/z8), after which the tip Assembly with the protector), and the mandrel 5 and the stop 6 mounted on the rod 7 of the hydraulic press, as shown in figure 1. Further, with the stop 6 "direct" stroke 7 Gidropress presoviet the tip Assembly with the protector) in a steel pipe; steel pipe is fixed against axial movement with crimp clamps 8 (figure 1). While planting tip with a steel pipe is carried out on the surface of the tip in the part where the protector.

Then from the rod Gidropress remove the stop 6, and pushes the steel lined pipe to the thrust ring 9 Gidropress 10 and "reverse" stroke hydraulic press pinch the plastic shell, while the burnishing is carried out only to the location of the tread (2), provided that the ratio of the outer diameter of the mandrel and the inner diameter of the tread and part of the tip of the outside tread area, i.e. in the zone tamamlama plot polyethylene sheath tip. Condition nedeformovanyh tip mandrel at the location of the tread due to the need not to disturb the prior mutual landing tip and protector.

The use of the present invention, the call is lit to ensure the reliability and efficiency of the tread for long life lined steel pipes.

The method of installation of the tip in the tube, lined with a plastic shell, including the placement of the tip with protector, installed with an interference fit in the end portion of the pipe and the pinched end of the plastic sheath tip by the burnishing, characterized in that the placement of the tip in the tube is performed with the tightness, and the burnishing tip carried out outside the location of the protector.



 

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