RU2536730C1 - Sealed threaded connection of casing pipes - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: sealed threaded connection for casing pipes from unplasticised polyvinylchloride comprises a male element and a female element with trapezoid thread profile, the female pipe end comprises an elongated socket with the inner diameter being less than the outer male element diameter by double height of the thread profile. The thread on the male and female elements is fitted by cone sections, the pipe section before the first thread turn is additionally fitted by a lead-in rib made as a cone. Additional leakproofness of the threaded connection is achieved due to a rubber packing ring set after the outer thread of the male element and adjoining the smooth cylindrical part of the lead-in rib on the inner thread on the female element.

EFFECT: improved strength and resistance of the threaded connection to axial and radial loads and the improved leakproofness of the threaded connection.

4 dwg

Description

The invention relates to the field of construction of water wells, as well as technological wells for transporting solutions, to which the material polyvinyl chloride (PVC) is chemically resistant, and can be used in casing and other pipes for technological purposes with sealed threaded joints. The tight threaded connection of casing pipes is intended for use in wells that have both low and high intensity of curvature of the barrel and / or with difficult operating conditions (axial and radial loads). The technical result consists in increasing the strength and stability of the threaded connection to axial and radial loads, as well as ensuring the tightness of the threaded connection.

When laying water wells, metal pipes with various types of threaded joints designed for casing are mainly used.

A threaded connection for pipes and a threaded connection method (Patent RU No. 2150040) are known, which comprises a coupling provided with two grooves with a tapered thread into which the inner ends of two metal pipes are screwed. The invention improves the reliability of the tightness of the pipe connection, and also improves the strength of the connection and the speed of the connection due to the larger profile and the pitch of the thread, but increases the number of elements involved in the connection.

Modern joints have metal-metal seals (Patent RU No. 2058505), formed by the contact between two surfaces, usually at one or two ends of the threaded part of the joint, expanding in the elastic range of the elastic modulus to provide an appropriate voltage value.

However, in some situations, instead of metal seals or in combination with them, it is necessary to use elastic seals to prevent the penetration of fluid from the outside into the gaps of the thread.

In such cases, metal casing is increasingly being replaced by metal casing pipes, ensuring high-quality and long-term pipeline laying.

Among plastic pipes, unplasticized polyvinyl chloride (nPVC) has the best performance. NpVC pipes have the best properties and the highest physicomechanical characteristics with respect to other polymers.

Known methods for threaded connection of PVC pipes without a socket with increased wall thickness and with internal and external threads, in which it is necessary to perform a threaded connection with a small thread profile height and a small pitch. Such a thread can withstand significantly lower axial loads, and a small thread pitch greatly complicates the start of screwing one end of the pipe into the other and can lead to damage to the threads. In addition, when connecting pipes in this way, it is possible for liquids to flow through the thread inside the pipe, which means an imperfect sealing system.

This type of threaded connection is implemented at the production site of Hemkor CJSC and they also presented another type of connection (Fig. 1), containing a female element (socket) with an internal thread and a male element with an external thread of a trapezoidal profile (http: //www.chemkor .ru / assets / files / GOST_TU / Extract_TU_obsadnye.pdf).

This technical solution was made as a prototype for the claimed invention.

This type of threaded connection allows you to eliminate the disadvantages of the aforementioned threaded connection, while reducing the wall thickness a and, accordingly, the cost of the product, however, there is a risk of pipe breakage in the event of bending deformations in curved wells and wells drilled at an angle.

The present invention is directed to solving the technical problem of resistance to external (axial and radial) loads by increasing the threaded cone and, as a consequence, lengthening the base of the socket, which does not come into contact with the extreme turn of the outer threaded zone of the male element, thereby moving the zone from high levels of stress and improving the work of the threaded connection to bend.

The specified technical result is achieved in that the sealed threaded connection contains male and female elements with a trapezoidal thread profile, and the female end of the pipe contains an elongated socket with an inner diameter of double the height of the thread profile less than the outer diameter of the male element. The thread on the male and female elements has conical sections, in addition, before the first turn of the thread, the pipe has a lead-in band made in the form of a cone. Additional sealing is ensured by a rubber sealing ring installed behind the external thread of the male element and adjacent to the even cylindrical part of the lead-in girdle of the internal thread of the female element.

The technical result achieved is to increase the strength and stability of the threaded joint to axial and radial loads, as well as to ensure the tightness of the threaded joint.

These features are significant and interconnected with the formation of a stable set of essential features sufficient to obtain the desired technical result.

The present invention is illustrated by a specific example, which, however, is not the only possible, but clearly demonstrates the possibility of obtaining the desired technical result.

Figure 2 presents a tight threaded connection of casing pipes.

According to the present invention, a sealed threaded connection includes male and female tubular parts with a trapezoidal thread profile with a profile angle of 30 °. The female end of the pipe contains an elongated, compared to the prototype, bell with an inner diameter D1 of a double profile height (engagement height H) of the thread less than the outer diameter D3 of the male member. Thus, the inner diameter of the socket D1 is equal to the diameter of the troughs of the profile of the male thread. Thread pitch P is defined as the average diameter of mating parts. To facilitate screwing in the pipes, the threads at the ends of the male and female parts have conical sections with a taper of 0.75. In addition, in front of the first turn of the thread there is a lead-in band made in the form of a cone with an angle of 15 ° to the axis of the pipe. In the conjugated state, gaps C1 and C2 are formed between the apex and the groove of the thread. When rolling the thread, the thread groove profile is rounded. The radius of the fillet R1 along the groove of the external and internal thread is C1, and the radius of the fillet R2 at the top of the external thread is 0.5 C2. The tightness of the threaded connection is ensured by the conical threaded connection, as well as an additional sealing element - a rubber ring installed behind the external thread of the male tubular part and adjacent to the even cylindrical part of the lead-in girdle of the internal thread of the female pipe.

The following are descriptions of specific implementations of these examples (figure 3, 4).

Figure 3 presents a sealed threaded connection of casing npvc with a nominal diameter of 125 mm and a wall thickness of 5 mm. The wall thickness provides high strength characteristics of the product during its operation with workloads and taking into account the safety factor.

The tight threaded connection contains a socket with an external diameter of the internal thread of 125.7 mm and with an internal diameter of the thread of 124.7 mm. The length of the socket in this connection is increased by 15 mm compared with the prototype, which allows you to immerse the casing in a bent or drilled at an angle borehole, without fear of pipe breakage. The internal thread of the socket is connected to the external thread mating to it, both threads having a trapezoidal profile with an angle of 30 ° and a profile height of 2 mm, which ensures high reliability of the threaded connection when axial tensile forces occur. This type of thread profile is due to its high performance under axial loads arising in the joint.

The internal and external threads are made in the form of a cone with a value of 0.75 over a length of 50 mm (Fig. 4), which facilitates the screwing of pipes. The lead-in band before the first turn of the external thread is also made in the form of a cone with an angle of 15 ° to the axis of the pipe. A taper angle of 15 ° provides an additional compression of the radial seal, which reduces radial interference, which in turn reduces the likelihood of damage to the sealing surfaces. With an increase in the specified angle, significant deformations of the inner diameter of the covered pipe begin to occur during compression or twisting of the connection. As the angle decreases, the taper effect is lost, because the conical groove of the socket becomes stiffer in the axial direction. The negative angle of the thread profile eliminates the possibility of the external thread coming out of engagement with the internal thread at significant tensile stresses, as the radial components of the reactions in the thread tend to press the pipe against the sleeve.

The main function of a thread is to absorb tensile load and bending, as well as partially compressive load. However, due to the taper, the tightness of the threaded connection is also ensured. To enhance the tightness effect and the suitability of using this connection for casing, an outer ring is fitted with an 115 × 121 × 36 O-ring in accordance with GOST 9833-73 / 18829-73, which is adjacent to the smooth cylindrical part of the lead-in girdle of the internal thread.

Due to the elongation of the socket and the use of seals, the threaded joint acquires the ability to work under the action of combined loads in aggressive environments, including those arising during the construction of deviated wells with a bore intensity of up to 10 °, which is an advantage over the prototype.

Claims (1)

A tight threaded connection for casing pipes made of unplasticized polyvinyl chloride, containing male and female elements with a trapezoidal thread profile, where the female end of the pipe contains an elongated socket with an inner diameter equal to twice the height of the male thread profile than the outer diameter of the male element, the thread on the male and female element has conical sections on which, before the first turn of the internal thread of the enclosing element, there is a cone-shaped lead-in band , to the smooth cylindrical part of which is attached a rubber o-ring mounted behind the external thread of the male element.

Images